Medicine, Faculty of
Population and Public Health (SPPH), School of
DSpace
UBCV
Chester, Clayton Marshall
Master of Science - MSc
University of British Columbia
The eye lens is particularly sensitive to ionizing radiation, and workplace exposures may potentially contribute to cataract development. This paper summarizes unattenuated eye lens dose readings within seven hospitals under the jurisdiction of Lower Mainland Medical Imaging. Unattenuated dose readings were captured from eye lens and collar dosimeters. An attenuated chest dose reading was also captured for comparison and model building. Unattenuated and attenuated dose readings above the limit of detection were analyzed for participants of two similarly exposed groups (Lower Mainland Nuclear Medicine and Lower Mainland Interventional), as determined by duration and proximity (less than one metre) to ionizing radiation. The median unattenuated eye lens dose readings for all participants were below WorkSafeBC’s eye lens exposure limits. Readings from Lower Mainland Nuclear Medicine were particularly low and did not approach action limits. Lower Mainland Interventional included readings which exceeded the internal quarterly action limit of 6.25 milliSieverts. Finally, unattenuated collar dose readings moderately explained the variance in unattenuated eye lens dose readings.
AN EVALUATION OF OCCUPATIONAL HEALTH ANDSAFETY CHANGES TO EYE LENS DOSE IN NUCLEARMEDICINE AND INTERVENTIONAL DEPARTMENTS OFLOWER MAINLAND MEDICAL IMAGINGbyCLAYTON MARSHALL CHESTERBPHE (Honours), Queen’s University, 2011A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THEREQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES(Occupational and Environmental Hygiene)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)December 2022© Clayton Marshall Chester, 2022The following individuals certify that they have read, and recommend to the Faculty of Graduate andPostdoctoral Studies for acceptance, the thesis entitled:An evaluation of occupational health and safety changes to eye lens dose in nuclear medicine andinterventional departments of Lower Mainland Medical Imagingsubmitted by Clayton Marshall Chester in partial fulfillment of the requirements forthe degree of Master of Sciencein Occupational and Environmental HygieneExamining Committee:Karen Bartlett, Professor, Occupational and Environmental Hygiene, University of British ColumbiaSupervisorYogesh Thakur, Medical Physics Lead, Vancouver Coastal HealthSupervisory Committee MemberSarah Henderson, Scientific Director, British Columbia Centre for Disease ControlSupervisory Committee MemberCheryl Peters, Senior Scientist, British Columbia Centre for Disease ControlAdditional ExamineriiAbstractThe eye lens is particularly sensitive to ionizing radiation, and workplace exposures may potentially con-tribute to cataract development. This paper summarizes unattenuated eye lens dose readings within sevenhospitals under the jurisdiction of Lower Mainland Medical Imaging. Unattenuated dose readings were cap-tured from eye lens and collar dosimeters. An attenuated chest dose reading was also captured for comparisonand model building. Unattenuated and attenuated dose readings above the limit of detection were analyzedfor participants of two similarly exposed groups (Lower Mainland Nuclear Medicine and Lower MainlandInterventional), as determined by duration and proximity (less than one metre) to ionizing radiation. Themedian unattenuated eye lens dose readings for all participants were below WorkSafeBC’s eye lens exposurelimits. Readings from Lower Mainland Nuclear Medicine were particularly low and did not approach ac-tion limits. Lower Mainland Interventional included readings which exceeded the internal quarterly actionlimit of 6.25 milliSieverts. Finally, unattenuated collar dose readings moderately explained the variance inunattenuated eye lens dose readings.iiiLay SummaryThis study evaluates ionizing radiation exposure to the eye lens in the context of reduced exposure limitsby WorkSafeBC. The study seeks to quantify and predict eye lens radiation exposure within two similarlyexposed groups within Lower Mainland Medical Imaging’s jurisdiction. This study is unique to the regula-tions and work practices of British Columbia and helps radiation safety program administrators assess whichsimilarly exposed groups may require ongoing eye lens radiation dose monitoring.ivPrefaceChapter One was completed solely by the thesis candidate. The formulations of inclusion and exclusioncriteria, within Chapter Two, were completed by the Regional Radiation Safety Lead at Lower MainlandMedical Imaging. The thesis candidate contributed to communication efforts via online presentations andcompliance documents. Eye lens dosimeters were ordered and distributed as a routine function of LowerMainland Medical Imaging’s radiation safety program. Data were anonymized by the Radiation Safety Lead.All descriptions in Chapter Two were completed by the thesis candidate. The data recovery, frame building,and analysis from Chapter Three were completed by the thesis candidate with supervision from Dr. SarahHenderson. All writing in Chapter Four was completed by the thesis candidate.This research was completed under the University of British Columbia’s Behavioural ResearchEthics Board with Research Identification Number H21-02008 and with project title Eye Lens Study.vTable of ContentsAbstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiiLay Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ivPreface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vTable of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viList of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiList of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiiGlossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ixAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xDedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi1 Chapter One: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Thresholds and Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.4 Regulatory Exposure Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.5 Regulatory Development Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.6 Notification Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.7 Dose Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.8 Dose Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.9 Eye Lens Dosimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.10 Potential Excess Risk in Healthcare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.11 Chest and Collar Dosimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.12 Eye Lens Dosimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.13 Eye Lens Dose Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.14 Worker Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.15 Research Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Chapter Two: Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.1 Research Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.2 Research Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.3 Similarly Exposed Group Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.4 Participant Inclusion and Exclusion Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.5 Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.6 Worksite Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.7 Data Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.8 Data Observation Inclusion and Exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.9 Threshold and Action Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.10 Model Building . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.11 Research Ethics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Chapter Three: Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.1 Statistical Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2 Variance Homogeneity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.3 Dosimeter Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.4 Eye Lens Dose Readings by Similarly Exposed Group . . . . . . . . . . . . . . . . . . . . . . 203.5 Predictive Dosimeter Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21vi3.6 Predictive Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 Chapter Four: Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254.1 Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254.1.1 Eye Lens Dose Reading Descriptive Statistics . . . . . . . . . . . . . . . . . . . . . . . 254.1.2 Dosimeter Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254.1.3 Unattenuated Eye Lens Dose Readings and Group . . . . . . . . . . . . . . . . . . . . 254.1.4 Unattenuated Eye Lens and Attenuated Chest Dose Readings . . . . . . . . . . . . . . 264.1.5 Unattenuated Eye Lens and Unattenuated Collar Dose Readings . . . . . . . . . . . . 264.1.6 Predictive Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264.2 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2.1 Enrollment and Donning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2.2 Shift Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2.3 Dosimeter Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2.4 Job Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.2.5 Workplace Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.3 Knowledge Transfer and Exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.3.1 Information Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.3.2 Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Chapter Five: Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Appendix A - Participant Intake Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Appendix B - Dosimetry Service Poster 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Appendix C - Eye Lens Study In-Service Presentation . . . . . . . . . . . . . . . . . . . . . . . . . 38Appendix D - Data Dictionary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Appendix E - Data Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Appendix F - Research Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50viiList of Tables1.1 Summary of Operational Quantities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 Radiation Weighting Factor by Type of Radiation. . . . . . . . . . . . . . . . . . . . . . . . . 51.3 Tissue Weighting Factor by Organ or Tissue. . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.1 Job Classification Inclusion and Similarly Exposed Group Assignment by Department (Al-phabetical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1 Summary Statistics of Total Readings Greater and Less Than Limit of Detection by Group. . 173.2 Summary Statistics of Unattenuated Eye Lens Dose Reading by Group (MilliSieverts). . . . . 173.3 Levene’s Test of Equal Variance Between Similarly Exposed Groups . . . . . . . . . . . . . . 183.4 One-Way Welch Analysis of Variance for Compliance and Similarly Exposed Group. . . . . . 193.5 One-Way Welch Analysis of Variance for Unattenuated (log) Eye Lens Dose Reading andSimilarly Exposed Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.6 Linear Regression Model Output for Unattenuated (log) Eye Lens and (log) Attenuated ChestDose Readings by Estimate (MilliSieverts). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.7 Linear Regression Model Output for Unattenuated (log) Eye Lens and (log) Collar DosimeterReadings by Estimate (MilliSieverts). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.8 Unattenuated (log) Eye Lens Dose Reading Model by Predictor (MilliSieverts) . . . . . . . . 23A.1 Job Title Inclusion by Department (Alphabetical) . . . . . . . . . . . . . . . . . . . . . . . . 36F.1 Total Results by Query from Ovid MEDLINE Database . . . . . . . . . . . . . . . . . . . . . 50viiiList of Figures2.1 Similarly exposed group development flow chart by hospital location. Each letter representsa unique hospital location which was assigned to either Lower Mainland Nuclear Medicine orLower Mainland Interventional. Hospitals E and G contributed dose readings to both LowerMainland Nuclear Medicine and Lower Mainland Interventional. . . . . . . . . . . . . . . . . 112.2 Data synthesis flowchart by observation count. Observations are reduced by exclusion ofreadings below the limit of detection. Total observations are reduced further by selection ofmaximum reading from the two quarters studied. . . . . . . . . . . . . . . . . . . . . . . . . . 153.1 Dosimeter compliance box-and-whisker plot by similarly exposed group. Percentages are cal-culated from chest, collar, and eye lens dosimeters. The box’s centre line represents the medianvalue for the similarly exposed group. The interquartile ranges (25 and 75 percentile) reachthe bottom and top of the box, respectively. Potential outliers are represented by single dots. 193.2 Unattenuated (log) eye lens dose readings (milliSieverts) by similarly exposed group with quar-terly exposure limit reference. Readings are calculated from eye lens dosimeters. The box’scentre line represents the median value for the similarly exposed group. The interquartileranges (25 and 75 percentile) reach the bottom and top of the box, respectively. The extend-ing vertical lines (whiskers) represent minimum and maximum values. Potential outliers arerepresented by single dots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.3 (log) Attenuated chest and (log) unattenuated eye lens dose readings scatter plot (milliSiev-erts). Linear regression line with confidence intervals are shown with equation and coefficientof determination top right. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.4 Unattenuated (log) collar and (log) eye lens dose readings scatter plot (milliSieverts). Linearregression line with confidence intervals are shown with equation and coefficient of determi-nation top right. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.5 Cook’s distance bar plot of (log) unattenuated eye lens dose reading model. Readings beyondthe threshold may negatively impact linear regression model and coefficient of variation. . . . 24B.1 Dosimetry Service Poster 2021. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37C.1 Behavioural Research Ethics Board approved presentation, slide 1. . . . . . . . . . . . . . . . 38C.2 Behavioural Research Ethics Board approved presentation, slide 2. . . . . . . . . . . . . . . . 38C.3 Behavioural Research Ethics Board approved presentation, slide 3. . . . . . . . . . . . . . . . 39C.4 Behavioural Research Ethics Board approved presentation, slide 4. . . . . . . . . . . . . . . . 39C.5 Behavioural Research Ethics Board approved presentation, slide 5. . . . . . . . . . . . . . . . 40C.6 Behavioural Research Ethics Board approved presentation, slide 6. . . . . . . . . . . . . . . . 40C.7 Behavioural Research Ethics Board approved presentation, slide 7. . . . . . . . . . . . . . . . 41C.8 Behavioural Research Ethics Board approved presentation, slide 8. . . . . . . . . . . . . . . . 41C.9 Behavioural Research Ethics Board approved presentation, slide 9. . . . . . . . . . . . . . . . 42C.10 Behavioural Research Ethics Board approved presentation, slide 10. . . . . . . . . . . . . . . 42C.11 Behavioural Research Ethics Board approved presentation, slide 11. . . . . . . . . . . . . . . 43C.12 Behavioural Research Ethics Board approved presentation, slide 12. . . . . . . . . . . . . . . 43C.13 Behavioural Research Ethics Board approved presentation, slide 13. . . . . . . . . . . . . . . 44C.14 Behavioural Research Ethics Board approved presentation, slide 14. . . . . . . . . . . . . . . 44C.15 Behavioural Research Ethics Board approved presentation, slide 15. . . . . . . . . . . . . . . 45C.16 Behavioural Research Ethics Board approved presentation, slide 16. . . . . . . . . . . . . . . 45E.1 Unattenuated eye lens dose reading histogram (untransformed). . . . . . . . . . . . . . . . . . 47E.2 Unattenuated eye lens dose reading quantile-quantile plot (untransformed). . . . . . . . . . . 48E.3 Unattenuated eye lens dose reading histogram (log-transformed). . . . . . . . . . . . . . . . . 48E.4 Unattenuated eye lens dose reading quantile-quantile plot (log-transformed). . . . . . . . . . . 49ixGlossaryDeterministic Means a health effect of radiation for which a threshold level of dose generallyexists above which the severity of the effect is greater for a higher dose. Effects ofwhich can include acute tissue reactions.Effective dose Means the sum of the products, in Sieverts, obtained by multiplying the equivalentdose of radiation received by and committed to each organ or tissue set out incolumn 1 of an item of Schedule 1 by the weighting factor set out in column 2 ofthat item.Equivalent dose Means the product, in Sieverts, obtained by multiplying the absorbed dose ofradiation of the type set out in column 1 of an item of Schedule 2 by the weightingfactor set out in column 2 of that item.Hp (0.07) Means personal deep dose at 0.07 millimetres depth.Hp (10) Means personal deep dose at 10 millimetres depth.Hp (3) Means personal shallow dose at 3 millimetres depth.Stochastic Means a radiation-induced health effect, the probability of occurrence of which isgreater for a higher radiation dose and the severity of which (if it occurs) isindependent of dose. Note: Stochastic effects may be somatic effects or hereditaryeffects, and generally occur without a threshold level of dose.a All definitions as per Canadian Nuclear Safety Commission regulatory documents and guidelines.xAcknowledgementsI wish to thank my supervisory committee, friends, and family for their significant contributions to my suc-cess. Specifically, Dr. Karen Bartlett for unwavering guidance and encouragement academically, personally,and professionally. Dr. Yogesh Thakur for trusting me with this research and providing critical logisticalsupport. Dr. Sarah Henderson for introducing me to the R language and greatly advancing my knowledgeand interest of statistics.To my friends who have provided unconditional support. Specifically, our friends Adam and Saman-tha who opened their home during a difficult time. To my parents, Lynn and Philip, who have believed inthe power of my continual education, formal or informal, no matter where it has taken me. To my siblings,Dylan, Justine, and Holly, who have shown me incredible depths of care, love, and inspiration. Finally, tomy wife, Bonita, for showing me the way; I love you.xiDedicationFor my familyxii1 Chapter One: Introduction1.1 Problem StatementNew epidemiological evidence from the International Atomic Energy Agency (2013) shows deterministic ef-fects with late manifestation from radiation exposure below the previously recommended annual equivalentdose limit of 150 milliSieverts. The revised equivalent dose limits recommended by the International AtomicEnergy Agency (2013) were “20 milliSieverts in a year, averaged over 5 consecutive years, and 50 milliSievertsin any single year.” Canada’s nuclear regulator, the Canadian Nuclear Safety Commission (2016), endorsedthe proposed amendments in April 2016. In British Columbia, new exposure limits were adopted on Decem-ber 1, 2021, with an added consecutive month limit (WorkSafeBC, 2021d). With respect to the eye lens, asof December 7, 2022, the WorkSafeBC exposure limits are an equivalent dose of 50 milliSieverts over anyperiod of 12 consecutive months, and 100 milliSieverts over any period of 60 consecutive months (Work-SafeBC, 2021d). To address compliance to the new regulation, Lower Mainland Medical Imaging is seekingto assess current occupational exposures within nuclear medicine and interventional technology departmentsacross seven major hospitals. Lower Mainland Medical Imaging is responsible for radiation safety across allhospitals in the Lower Mainland of British Columbia, regardless of the health authority by which they areadministered. Services under Lower Mainland Medical Imaging’s jurisdiction include nuclear medicine, car-diology, radiology, angiography, computed tomography, magnetic resonance imaging, ultrasound, diagnosticbreast imaging, and specialty procedures.This study is being completed with the support from the Lower Mainland’s Medical Imaging oc-cupational health and safety department and Regional Radiation Safety Officer. This research exploresunattenuated eye lens dose reading data within similarly exposed groups and predicts equivalent dose tothe eye lens from adjacent dosimeters. It is expected that all participants under Lower Mainland’s MedicalImaging’s jurisdiction are below an annual action limit set to one-half of WorkSafeBC’s regulation (i.e., 25milliSieverts). Similarly exposed groups potentially exceeding the WorkSafeBC regulations will be identifiedand recommendations will be proposed.1.2 BackgroundThe eye lens is one of the most radiosensitive tissues in the human body (Ainsbury et al., 2009). According tothe Radiation Effects Research Foundation (2021), cataracts from radiation exposure “cause partial opacityor cloudiness in the crystalline lens and result in damaged cells covering the posterior surface of the lens.”1Depending on the dose, symptoms can appear within one or two years for high-dose exposures, and withinmany years for low-dose exposures. Damaged cells collect at the centre of the posterior pole of the eye lensand create opacities by preventing light from traveling forward. A mode of action for lens opacity fromradiation exposure is proposed by the Hiroshima International Committee for Health Care of the Radiation-Exposed (2012). Within the structure of the eye lens, a transparent layer of epithelial cells covers the lenson the interior frontal side, and the epithelial cell layer maintains function of the lens through cell divisionfrom the periphery toward the equator. Exposure to ionizing radiation damages dividing epithelial cellswhich converge at the posterior pole and result in opacity (Radiation Effects Research Foundation, 2021).Of the three different types of cataracts (nuclear sclerotic, cortical, and posterior subcapsular), posteriorsubcapsular cataracts are most associated with ionizing radiation exposure (Loganovsky et al., 2020).1.3 Thresholds and EffectsRadiation-induced cataract formations at acute, high-doses are well documented. A study from atomicbomb survivors initially proposed a threshold limit [90% confidence interval] of 700 milliSieverts [>0, 2800milliSieverts] for posterior subcapsular cataracts (Nakashima et al., 2006). The International Commissionon Radiological Protection (2012) released a statement on threshold doses for tissue reactions, and concludedthere was evidence of deterministic effects with late manifestation, where threshold doses were (or might havebeen) lower than previously considered. However, the International Commission on Radiological Protectionalso cited evidence to suggest cataract formation could be stochastic and form at any dose. This suggestslong and short-term exposures may be equally as damaging.International Commission on Radiological Protection (2012) expects this research gap to be resolvedthrough “human epidemiological approaches” and has recommended equivalent dose to the eye lens notexceed “20 milliSieverts in a year, averaged over 5 consecutive years, and 50 milliSieverts in any single year.”Canada’s federal nuclear regulator, the Canadian Nuclear Safety Commission (2016), released a technicalnote to amend the current guidelines to those proposed by the International Commission on RadiologicalProtection. In the note, the Canadian Nuclear Safety Commission recommends licensees act in investigatingwork practices, reviewing existing training material, and initiating a hazard assessment to understand currentdoses to workers. As of December 1, 2021, WorkSafeBC (2021d) amended regulations to equivalent dosesof 50 milliSieverts over any period of 12 consecutive months, and 100 milliSieverts over any period of 60consecutive months.21.4 Regulatory Exposure LimitsExposure limits for biological, chemical, and physical workplace hazards are recommended by prominentinternational regulatory bodies, governing agencies, and committees. WorkSafeBC (2022a) generally usesexposure limits established by the American Conference of Governmental Industrial Hygienists. A revisedlist of threshold limit values is produced annually and often refer to airborne concentrations of chemicalsubstances under which a worker may be exposed without adverse health effects. Exposure limits may includehazardous concentrations at 8-hours, 15-minutes, and those immediately dangerous to life and health.As per section 115 of the Workers Compensation Act, WorkSafeBC (2022b) states that the organi-zation must perform ongoing reviews of new or revised threshold limit values similar to radiation exposurelimits. After review, WorkSafeBC engages stakeholders in a pre-consultation session, and releases proposedexposure limit changes to the public for consultation. WorkSafeBC’s Board of Directors then decides on newor revised threshold limit values with public and WorkSafeBC consultation.In Canada, radiation exposure limits can be established federally and provincially. Federally, theCanadian Nuclear Safety Commission (2022a) makes recommendations with review of evidence from suchorganizations as the International Commission on Radiological Protection and the International AtomicEnergy Agency. The International Commission on Radiological Protection is an independent organizationwhich seeks to advance radiological protection for public benefit (2022). It is a community of more than 250globally-recognized experts from more than 30 countries. The International Atomic Energy Agency (2022)promotes the safe, secure, and peaceful use of nuclear technologies. For Canadian Nuclear Licencee Programs(e.g., nuclear medicine), the federal exposure limits apply. For x-ray workers, the WorkSafeBC provincialexposure limits are applicable. In practice, whichever of the federal or provincial exposure limits is mostconservative is followed by Lower Mainland Medical Imaging.1.5 Regulatory Development ProcessAmendments to the Workers Compensation Act are completed by the Legislative Assembly of BritishColumbia; WorkSafeBC is required to follow theWorkers Compensation Act, and the regulations and policiestherein must be consistent. The Policy, Regulation, and Research Division advises WorkSafeBC’s Board ofDirectors and consults with workers, employers, industry and scientific experts, as well as divisions withinWorkSafeBC. WorkSafeBC develops and implements occupational health and safety regulations, and allworkplaces must meet the legal requirements set out in the regulations. The regulatory amendment processallows stakeholders to view and comment on proposed amendments before reaching the Board of Directors3for approval. For example, the Policy, Regulation, and Research Division works with internal and externalexperts to better understand regulatory proposals. There is a public consultation phase which allows forpublic feedback. After initial consultation, a second opportunity for public consultation is made available viapublic hearings and reviewed by the Board of Directors. If approved, the amended regulation is typically ineffect within three to four months (WorkSafeBC, 2021c). With respect to the eye lens, the new regulationswere approved for December 1, 2021, in July 2021. It was previously stated at the Board of Directors meetingthat the previous dose limit “did not reflect current scientific understanding of harmful levels of ionizingradiation exposure” (WorkSafeBC, 2021a). The newly amended regulation can be found in Section 7.19(1)of the Occupational Health and Safety Regulation (WorkSafeBC, 2021d).1.6 Notification GuidelinesAs a result of the December 1, 2021, regulatory amendments, the guidelines for notification have alsobeen updated in the event of overexposure. The new guidelines apply to both equivalent and effectivedoses. Notifications of overexposure can come from an accident investigation report, employer, NationalDose Registry, or other means. Once notification has been received by WorkSafeBC, a request for incidentinvestigation will be forwarded to the local Occupational Hygiene Officer. This information will be usedto determine the suitability of the worker’s continued employment in the same category for the rest of theexposure period. The worker is to be protected from further exposure until an investigation is completed,corrective actions are implemented, and medical opinion is given. The suitability of continued employmentwill depend on the reliability and accuracy of the report, magnitude of dose received, lifetime dose, extentof injury, and adequacy of controls (WorkSafeBC, 2021b).1.7 Dose MonitoringTo measure individual radiation doses, dosimetry is performed. The Canadian Nuclear Safety Commissionissues licenses to carry out activities described in relation to nuclear substances or radiation devices. Alllicensees are required to control doses to workers and the public, and to effectively monitor dose usingan approved licensed dosimetry service (i.e., Landauer) (2022c). To understand dose to workers, directmonitoring can be carried out with a personal dosimeter. Active dosimeters produce a radiation-inducedsignal and display a direct reading (Canadian Nuclear Safety Commission, 2022b). Personal dose monitoringof numerous organs can be accomplished at variable depths with dosimeters of differing operational quantities.4Table 1.1Summary of Operational Quantities.Operational Quantity Description𝐻 𝑝 (10) Personal dose equivalent at 10 millimetre depth𝐻 𝑝 (0.07) Personal dose equivalent at 0.07 millimetre depth𝐻 𝑝 (3) Personal dose equivalent at 3 millimetre depth1.8 Dose MeasurementDose absorbed by a worker’s body is expressed as equivalent and effective doses. To determine equivalentdose to the hands, feet, or eye lens, where exposure to these parts of the body may be substantially different,WorkSafeBC recommends selecting one of two guidelines from the Canadian Nuclear Safety Commission orInternational Atomic Energy Agency. To maintain adherence to federal recommendations, the CanadianNuclear Safety Commission’s regulatory document (REGDOC-2.7.2, Dosimetry, Volume 1: AscertainingOccupational Dose) has been selected as the reference document.Table 1.2Radiation Weighting Factor by Type of Radiation.Type of Radiation Radiation Weighting FactorPhotons (i.e., x-ray or gamma) 1Electrons 1Photons and charged pions 2Alpha particles, fission fragments, heavy ions 20Neutrons 2.5 - 21The effective dose is then calculated by adding each tissue’s equivalent dose and multiplied by thetissue weighting factor (Table 1.3).5Table 1.3Tissue Weighting Factor by Organ or Tissue.Organ or tissue Tissue Weighting FactorBone marrow (red), colon, lung, stomach, breast 0.12Gonads 0.08Bladder, esophagus, liver, thyroid 0.04Bone surface, brain, salivary glands, skin 0.01Whole body 1To maintain equal equivalent dose comparisons, no tissue weighting factor will be applied in thisstudy.1.9 Eye Lens DosimetryThere is potential for non-uniform radiation exposures to hospital workers due to varied positioning and ori-entation to nuclear substances and radiation equipment. According to REGDOC-2.7.2, Dosimetry, Volume1: Ascertaining Occupational Dose (2022b), workers can be exposed to non-uniform radiation fields whenthe head is closer to the radiation source or when the trunk is shielded and eyes are not. In these scenarios,the nature of exposure should be documented, and a method of assessment should then be determined. In-dividual monitoring for the eye lens can also include dosimeters worn away from the eye lens (i.e., chest andcollar) which measure 𝐻 𝑝 (10) or 𝐻 𝑝 (0.07), respectively. Thus, this study will also assess individual dosefrom chest and collar dosimeters. Weakly penetrating beta radiation with energies less than 700 kilo-electronvolts are not required to be assessed and will be removed from data analysis.1.10 Potential Excess Risk in HealthcareWith the changes to the regulations in British Columbia, there are significant practical implications for work-places and radiation workers. CAREX Canada estimates 35,000 to 86,000 workers were exposed to ionizingradiation in 2016. In the medical industry, there were 48,000 workers exposed (CAREX Canada, 2021). Ac-cording to the World Health Organization (2021), cataracts are “the most common cause of blindness, visualimpairment, and low vision.” Vision loss can affect employment, quality of life, independence, and mobil-ity while also impacting mental health and social function (National Center for Biotechnology Information,2021). In a 20-year prospective cohort among radiation technologists, the adjusted hazard ratio between6the highest and lowest categories of occupational dose and cataract formation [95% confidence interval] was1.18 [0.99, 1.40] (Chodick et al., 2008). By comparison, the highest category of ultraviolet radiation-exposedparticipants produced a hazard ratio [95% confidence interval] of 1.16 [1.03, 1.31] (Chodick et al., 2008).There is a need for novel study designs, equipment, and techniques to understand occupationaleye lens dose from radiation. The International Radiation Protection Association (2016) noted a dearth ofresearch due to limited availability of eye lens dosimeters. Furthermore, an assessment of worker knowledgeof the new regulations and personal protective equipment showed a significant deficiency in knowledge andlack of equipment compliance among x-ray technicians in Italy (D’Avino et al., 2019). There is a clear needfor greater understanding and measurement of eye lens dose within the healthcare sector.1.11 Chest and Collar DosimeterLandauer Incorporated is the most prominent dosimeter service provider used in practice and within thestudies reviewed. The Landauer dosimetry service is approved by the National Dosimetry Registry in Canada,a branch of Health Canada. Their dosimeter model, Luxel+, is self-contained and pre-loaded with aluminumoxide “sandwiched within a multi-element filter pack that is heat sealed within a laminated, light-tight paperwrapper” (Landauer, 2021). To eliminate mishandling, leakage, or tampering, the components are sealedin a tamper-proof plastic pack. The Luxel+ measures photons (x-ray and gamma) and beta particles withoptically stimulated luminescence, while neutrons are measured with chemical etching and track countinganalysis methods. The filter pack is stimulated with select laser frequencies causing it to emit light inproportion to the amount of radiation dose. A dose algorithm relying on response ratios determines whetherthe dose was photon or beta radiation (Landauer, 2021). The limit of detection for the Luxel+ dosimeter is0.01 milliSieverts.1.12 Eye Lens DosimeterLandauer’s eye lens dosimeter, the Landauer Vision, is a lithium fluoride thermoluminescent dosimeter chipplaced within a polyamide holder. The dosimeter is sealed via ultrasound welding. Similar to the Luxel+,radiation dose is determined from visible light emitted in proportion to the exposure of ionizing radiation(Landauer, 2022). The limit of detection for the Vision dosimeter is 0.1 milliSieverts.Correct and consistent placement of the eye lens dosimeter is essential to limit under and overestimation of the equivalent dose. The International Radiation Protection Association (2021) recommendsusing a dosimeter “close to the eye, on a headband, the side of the head, the eyebrow ridge, on the forehead”7or attached to protective leaded safety glasses. In a simulated exposure study of eye lens dose and protectiveglasses, several positions were modeled for dose measurement. To limit underestimation of dose to the eyelens, the authors recommended positions on the skin, not shielded from glasses or close to the eye, with nocorrection factor applied (Honorio da Silva et al., 2020). The dosimeter can also be placed over the shielding,but not behind the shielding. Consideration should also be given to the style of protection being flat or wraparound lenses. Consistent application and positioning of dosimeters by workers is critical to understandingworkplace exposure values. Correct positioning and visualization of eye lens, chest, and collar dosimetersare shown in Appendix B.1.13 Eye Lens Dose AssessmentNumerous workplace studies have examined dose to the eye lens in departments of potentially extendedproximal exposures (e.g., nuclear medicine and cardiology). In a six-year study of nearly 6,000 healthcareworkers, Bellamy and colleagues (2020) found low mean eye lens dose (0.29 milliSieverts) for all monitoredworkers. Dabin and colleagues (2016) recorded weekly and annual eye lens equivalent doses ranging from0.02 to 0.27 and 0.6 to 9.3 milliSieverts, respectively. Finally, Piwowarska-Bilska and colleagues (2018) foundthree-month dose equivalents in the range of 0.20 to 0.41 milliSieverts. In some cases (Bellamy et al., 2020),workers exceeded the study’s proposed action limit and further assessment was required.Researchers have also examined the correlation between doses from different dosimeters positionedon the body. A study by Demeter and colleagues (2019) in nuclear medicine departments in Manitoba foundthat 67% of the variance in the eye lens dose could be explained by chest dose. While eye lens dosimeters wereclipped to the arm of protective glasses, the position of the chest dosimeter (over or under lead shielding)is not immediately known. Dabin and colleagues (2016) also proposed that whole body dose could be usedto roughly estimate eye lens dose (Spearman’s correlation = 0.64, p < 0.05). These outcomes suggest thatadditionally assigned dosimeters could be used to approximate eye lens dose and to indicate whether furthermeasurement is required.1.14 Worker ProtectionTime, distance, and shielding are essential methods to control exposures to physical hazards such as ionizingand non-ionizing radiation, vibration, noise, and thermal stress. The less time a worker spends in proximityto physical hazards, the lower the likelihood of exposure and dose. Furthermore, increasing distance signif-icantly reduces the risk to workers in proximity to radiation sources. Appropriate shielding at the source,8during transmission, and on the worker can also reduce potential exposure and dose. Therefore, controllingmedical workers’ distance to, and duration with, high energy emitting equipment and radioactive sources areimportant determinants of exposure reduction. In practice, workers performing fluoroscopy-guided proce-dures are potentially prone to significant or moderate eye lens exposure from x-rays (Netherlands Commissionon Radiation Dosimetry, 2018). The benefits of fluoroscopy-guided procedures include a non-invasive ap-proach to diagnosis and surgery with a greater view of internal organs and structures. However, becausesurgeons are typically within 20 to 50 centimetres of the patient, fluoroscopy and x-ray equipment increasethe likelihood of hazardous exposures and outcomes (Szermerski et al., 2016). To estimate duration of inter-ventional technology use, a study of surgeons (trauma and hand) and surgeon’s assistants (Apelmann et al.,2019) found a maximum duration of fluoroscopy of 230, 305, and 407 seconds, respectively. Each similarlyexposed group was well below the study’s proposed action limit. A contralateral position of the surgeon ispreferred to reduce potential eye lens dose (Arif et al., 2020). Significant consideration into controlling thedistance and duration to the radiation source is essential to reduce excess risk.The eye lens dosimeter should be placed externally to leaded safety glasses and recorded as an“unattenuated” dose reading. In a laboratory-controlled experiment by Gangl and colleagues (2022), theprotective effect of leaded glasses depended on eye levels (height of the interventionalist) and head rotation.Moriarty and colleagues (2022) found that particular leaded glasses worn by interventional radiologists andtechnicians reduced radiation exposure by 79%. A study of two experienced urologists determined that leadglasses can reduce average exposure to the left and right eye lenses by 72.5 and 62.2%, respectively (Suzuki etal., 2020). Consistent compliance with, and proper fitting of, eye protection during interventional proceduresis essential in reducing dose to the eye lens.1.15 Research ValueThis is the first study analyzing eye lens dosimetry in British Columbia. This study is especially valuableas it offers the first glimpse of the new regulatory changes which took effect December 1, 2021. Morespecifically, the statistical capacity of the researchers to model potential dose from adjacent dosimeters isparticularly important in estimating dose in other cohorts, authorities, provinces, and countries lackingresources or capacity for such a study. There is evidence from previous studies suggesting some exposuresmay approach the Lower Mainland Medical Imaging’s annual action limit (i.e., 25 milliSieverts). This studywill be a fundamental exploration of estimated dose to the eye lens within departments of extended proximalexposures in British Columbia.92 Chapter Two: Methods2.1 Research ObjectivesThere were three primary objectives of the research. First, to measure six-month equivalent dose to theeye lens within similarly exposed groups of Lower Mainland Medical Imaging. Second, to model potentialpredictors of equivalent dose to the eye lens from additionally assigned dosimeters. Third, to identify high-priority worker cohorts which may require ongoing eye lens dosimetry.2.2 Research SynthesisResearch was synthesized via search term queries from Ovid’s MEDLINE database (Appendix F). Abstractswere reviewed for applicability by total study population and duration, job classification, proximity andduration to ionizing radiation, and dosimeter selection, position, and compliance. The research databasewas reviewed on a quarterly basis for significant contributions to research subject matter.2.3 Similarly Exposed Group DevelopmentFor the evaluation of ionizing radiation dose to the eye lens, two distinct, and similarly exposed groups, wereorganized from seven hospitals within Lower Mainland Medical Imaging’s jurisdiction. Similarly exposedgroups are those workers with similar exposure profiles through the understanding of worker proximityand duration to ionizing radiation, as well as experience, training, equipment use, and available hazardcontrols. As determined by Lower Mainland Medical Imaging’s Regional Radiation Safety Officer, all nuclearmedicine departments were grouped together under the title Lower Mainland Nuclear Medicine, while allinterventional departments were grouped together under the title Lower Mainland Interventional (Figure2.1). Lower Mainland Nuclear Medicine staff are considered similarly exposed due to proximity to gammaradiation sources, while Lower Mainland Interventional is considered similarly exposed due to proximity tox-ray sources (e.g., fluoroscopy, computed tomography, portable x-ray equipment).10ALower Mainland Nuclear MedicineB C DLower Mainland InterventionalE FGFigure 2.1: Similarly exposed group development flow chart by hospital location. Each letter represents aunique hospital location which was assigned to either Lower Mainland Nuclear Medicine or Lower MainlandInterventional. Hospitals E and G contributed dose readings to both Lower Mainland Nuclear Medicine andLower Mainland Interventional.2.4 Participant Inclusion and Exclusion CriteriaGeneral inclusion criteria for the study focused on job classifications within one metre of an emitting ionizingradiation sources over a significant duration during a regular workday. Prolonged, proximal exposures weredue to complexity of procedure and interventional equipment time and type. Job classifications includedthose workers performing and assisting in interventional procedures, and distributing and handling nuclearmedicines. Full time radiation workers with greater than two years of experience were included. New workersoften transition, change locations or job classifications, and so this criterion prioritized consistent participantdata over the six-month study period. Physicians and fellows were expected to follow all regulations andprocedures mandated by Lower Mainland Medical Imaging. On June 11, 2021, participation intake formswere sent to representatives of each selected department and hospital (Appendix A). Forms were returnedto Lower Mainland Medical Imaging and were not shared with researchers. Final selections for the proposedsimilarly exposed groups are summarized in Table 2.1.11Table 2.1Job Classification Inclusion and Similarly Exposed Group Assignment by Department (Alphabetical)Department Job Classification Similarly Exposed GroupCatheterization Lab Interventional Cardiologists Lower Mainland InterventionalFellows Lower Mainland InterventionalNurses Lower Mainland InterventionalEndoscopy Physicians Lower Mainland InterventionalFellows Lower Mainland InterventionalNuclear Medicine Technologists Lower Mainland Nuclear MedicineOrthopaedic Surgery Surgeons Lower Mainland InterventionalRadiology Interventional Radiologist Lower Mainland InterventionalFellows Lower Mainland InterventionalNurses Lower Mainland InterventionalTechnologists Lower Mainland InterventionalUrology Urologists Lower Mainland InterventionalFellows Lower Mainland InterventionalVascular Surgery Surgeons Lower Mainland InterventionalFellows Lower Mainland InterventionalGeneral exclusion criteria covered job classifications deemed low priority due to greater distanceand shorter duration to emitting sources and equipment. Radiation workers under the jurisdiction of LowerMainland Medical Imaging and working at more than one location, employed on a casual basis, operatingmini-c arm fluoroscopy units exclusively, and designated as charge nurses were also excluded. Multi-site,casual employees were also excluded due to administrative complexity and preliminary nature of the study.If any extrapolated annual equivalent dose from October 1, 2021, to December 31, 2021, exceeded one-half ofthe proposed annual limit (i.e., 25 milliSieverts), then cohorts which had been deemed lower priority wouldbe incorporated into the study.2.5 Data CollectionCollection of badge dosimetry data was a routine requirement and function of each hospital. The hospitalsassigned, distributed, and collected chest, collar, and eye lens dosimeters. The dosimeters were then collected12and returned to Landauer, the third-party service provider, for processing. The processed results wereposted to a secured cloud with internal access for designated hospital staff. The Regional Radiation SafetyOfficer had access to the information and was the point person for download and processing. Also, theRegional Radiation Safety Officer at Lower Mainland Medical Imaging developed custom software to prepareanonymized data to the thesis candidate. In the event participants were overexposed, the Lower Mainland’sMedical Imaging department had a reverse-entry key to determine corrective action. Anonymized data wereadded to a shell table and shared with the thesis candidate at the University of British Columbia’s secureshared area. The shared area under the University of British Columbia’s ownership was established on June2, 2021. Data collection occurred for six months starting on October 1, 2021, and ending on March 31, 2022.2.6 Worksite CommunicationsAn intake form with inclusion and exclusion criteria was sent to department leaders for review and completion(Appendix A). A standard operating procedure with correct placement of dosimeters was developed incollaboration with Lower Mainland Medical Imaging’s occupational health and safety department (AppendixB). This procedure was used to promote the correct placement of eye lens dosimeters for the purpose of thestudy. Surgeons were instructed to wear the dosimeter closest to the most exposed eye, and on the lens frameor in the surgeon’s cap. All other staff were instructed to wear the dosimeter closest to the most exposed eye,and on the arm of the glasses. In-person meetings with leadership were held to discuss details of the study.Two in-service meetings were held weekly beginning October 1, 2021, and ending March 31, 2022. Due tothe COVID-19 pandemic, and provincially-mandated restrictions on gatherings and hospital visitations, allmeetings were held online. A Behavioural Research Ethics Board-approved PowerPoint presentation wascreated and delivered during in-service meetings to help stakeholders understand the scope of the research(Appendix C).2.7 Data SynthesisData were analyzed using R Studio (Version 2022.02.0) Statistical Programming Software (RStudio, 2015).An open-source repository (jepa, 2019) intended for use by University of British Columbia students wasadopted as the thesis template. Data were retrieved from the University of British Columbia’s secured,shared access drive after uploading by Lower Mainland Medical Imaging. Only data from October 1, 2021,to March 31, 2022, were included. Data were then converted into a comma-separated value (i.e., .csv) fileformat and uploaded to R Studio. An annotated analysis is available at a private repository (Chester,132021) on a document version control website. Data were then organized into tidy, long format with eightvariables (employee identification number, location, department, year, quarter, dosimeter, compliance, dose).An explanation of all variables included in the raw data set is available in Appendix D. R language codewas written to automatically read column values from the raw data upload, thereby limiting potentialfor transcription errors. To ensure all observations were unique from each location, a research identificationvariable was created from location and employee identification number. Generically, the pattern was: locationacronym, underscore, employee identification number, underscore, quarter (i.e., vgh_001_q1).2.8 Data Observation Inclusion and ExclusionTo satisfy study objectives, and control for potential exposure fluctuations via seasonal and personal changes,observations below the limit of detection were excluded. This approach is supported by Hornung and Reed(1990) when more than half of the data observations are determined to be below the limit of detection. Theauthors state potentially biased or imprecise calculations of the geometric mean and standard deviations mayresult when greater than half of the total observations are above the limit of detection. As an outcome ofsignificant readings below the limit of detection is hypothesized, the recommendation from Hornung and Reed(1990) is to report the percentage of observations below the limit of detection and proceed with the remainingrange. Observations of “M” (below Landauer’s limit of detection) were unchanged and uploaded as “NA”to the data frame. Only observations with “P” (photon radiation) were included. Weakly penetrating betaradiation observations, “B,” were not included. Dosimeters were stored away from radioactive sources. Acontrol dosimeter was also stored away from potential occupational dose and was used within all hospital sitesto measure non-occupational dose. The control dosimeter’s reading was then subtracted from participantdose reading. Observations of compliance and dose were uploaded from each participant’s dosimeter (chest,collar, and eye) with observations of location, department, year, and quarter. For all dosimeters, only thereported “LDE” (lens dose equivalent) was used for data analysis. Landauer’s equations and estimatesfor eye lens dose from chest dosimeters assume the eye lens dose is unattenuated. The equivalent dosetakes into account the type of radiation to which one is exposed. There were no corrections for tissue ororgan. Landauer’s proprietary dosimeters validate that exposures are dynamic and have occurred while theparticipant is active. In the event a static dose is found, quality control and re-analysis is completed anddocumented. Where a participant had two readings below the limit of detection, both readings were removed.Where a participant had one or both readings above the limit of detection, the highest readings were usedfor analysis (Figure 2.2). A histogram and quantile-quantile plot of all remaining dose readings was shown tobe right-skewed (Appendix E). As a result, all readings were log-transformed for log-normality. All analyses14were completed using log-transformed data. Visualizations were created from appropriate categorical andcontinuous variables. A parsimonious model was created by testing all variables and ensuring any variableincluded in the final model contributed at least one percent to the explanation of variance. The predictivemodel was then created and used to predict log-transformed dose readings.Total ObservationsIncluding all quarters, dosimeters, and NAsn = 10,331Removed all observations < limit of detection9176 NA observations removedn = 1155Selected highest dose readings for each participant377 observations removedn = 778Figure 2.2: Data synthesis flowchart by observation count. Observations are reduced by exclusion of readingsbelow the limit of detection. Total observations are reduced further by selection of maximum reading fromthe two quarters studied.2.9 Threshold and Action LimitsFor ionizing radiation, WorkSafeBC has set an action level and an effective dose of 1 milliSievert per year(whole body). Lower Mainland Medical Imaging has implemented the necessary controls to meet this re-quirement. In response to the reduced eye lens exposure regulations, internal action limits can also be set.For this research, the action limit for 12-month equivalent dose to the eye lens has been set to 25 milliSiev-erts. This allows Lower Mainland Medical Imaging to investigate exposures before a worker may exceedmaximum annual dose. Data in the results section are compared to eye lens equivalent dose action limits.152.10 Model BuildingThe pairwise relationships between unattenuated eye lens dose readings and each of the potentially predictivevariables (group, location, dosimeter) were visualized, tested for association, and quantified for effect usinga scatter plot, coefficient of determination, and linear regression, respectively. The model was built with allvariables included and then parsed for significant relationships (those contributing at least one percent to theadjusted coefficient of determination). The model was compared and verified with the stepwise regressionfunction within R Studio.2.11 Research EthicsThe University of British Columbia’s Behavioural Research Ethics Board is responsible for reviewing be-havioural or social science research, or research that may involve the study of patients or health careproviders. Due to the use of secondary data from health care providers, a formal application was com-pleted with the Behavioural Research Ethics Board. The initial application was approved July 26, 2021,with Ethics Identification Number H21-02008. A post application with amendments was approved Septem-ber 28, 2021, with Ethics Identification Number H21-02008-A002. The annual renewal was completed July8, 2022. The Tri-Council Policy Statement and Course in Research Ethics was completed June 26, 2021.163 Chapter Three: Results3.1 Statistical SummariesStatistical summaries of the data are presented from pre-and-post exclusion of readings below the limit ofdetection. The summaries include observation count below the limit of detection (Table 3.1), as well as postexclusion group sizes (n), medians, arithmetic and geometric means and standard deviations, and maximumdose readings (Table 3.2). It was expected that all participating radiation workers under the jurisdiction ofLower Mainland Medical Imaging were below an annual action limit set to one-half (i.e., 25 milliSieverts) ofWorkSafe BC’s current exposure limit (50 milliSieverts). A quarterly action limit was proposed to be 6.25milliSieverts.Table 3.1Summary Statistics of Total Readings Greater and Less Than Limit of Detection by Group.Group Less than Limit of Detection Greater than Limit of Detection Total ObservationsLower Mainland Interventional 8279 639 8918Lower Mainland Nuclear Medicine 699 516 1215Approximately (8279/8918) ∗ 100 = 93% and (699/1215) ∗ 100 = 58% of all readings from LowerMainland Interventional and Nuclear Medicine were below the limit of detection, respectively. With greaterthan 50% of all readings below the limit of detection, an exclusion of readings below the limit of detectionwas justified (Hornung & Reed, 1990).Table 3.2Summary Statistics of Unattenuated Eye Lens Dose Reading by Group (MilliSieverts).Group N Median Mean Max SD Geo. Mean Geo. SDLower Mainland Interventional 44 0.46 1.17 8.46 1.97 0.52 3.14Lower Mainland Nuclear Medicine 94 0.24 0.32 1.05 0.20 0.27 1.78Lower Mainland Interventional and Nuclear Medicine had median and mean readings below theaction limit. However, Lower Mainland Interventional’s maximum reading exceeded the action limit andgeometric standard deviation of 3.14 suggested high variability of worker exposure. Further definition ofLower Mainland Interventional may be required. Lower Mainland Nuclear Medicine geometric standarddeviation of 1.78 showed low variability (Government of Canada, 2022).17A visual inspection of the unattenuated eye lens dose reading data via histogram density andquantile-quantile plots showed evidence of log-normality with the mode less than the median and mean(Appendix E). After log-transformation, the dose readings followed a more normal distribution with valuesclustered around the median. As such, all values used for the remaining analysis and modeling were log-transformed.3.2 Variance HomogeneityA Levene’s test was used to determine if there were equal variances between similarly exposed groups (Table3.3). Between similarly exposed groups, there was a significantly high F-value (ratio of between group andwithin group variance) and a p-value less than 0.05. The Levene’s test rejected the hypothesis of equalvariance. Therefore, Welch’s one-way analysis, most suitable in cases of unequal variance, was used.Table 3.3Levene’s Test of Equal Variance Between Similarly Exposed GroupsF-value p-value Degrees Freedom Degrees Freedom (Residual)15.57 <0.001 1 1363.3 Dosimeter ComplianceTo visualize the relationship between similarly exposed groups and compliance, a box-and-whisker plot wascreated (Figure 3.1). All assigned dosimeter readings were included.18406080100Lower Mainland Interventional Lower Mainland Nuclear Medicine Dosimeter Compliance (%)Figure 3.1: Dosimeter compliance box-and-whisker plot by similarly exposed group. Percentages are calcu-lated from chest, collar, and eye lens dosimeters. The box’s centre line represents the median value for thesimilarly exposed group. The interquartile ranges (25 and 75 percentile) reach the bottom and top of thebox, respectively. Potential outliers are represented by single dots.Median dosimeter compliance was equal among the similarly exposed groups, however Lower Main-land Nuclear Medicine showed greater number of potential outliers. A one-way Welch’s analysis of variancewas used to test the difference in means between each similarly exposed group and dosimeter compliance.A significant difference in dosimeter compliance was found between Lower Mainland Nuclear Medicine andLower Mainland Interventional (Table 3.4).Table 3.4One-Way Welch Analysis of Variance for Compliance and Similarly Exposed Group.n Test Statistic Degrees Freedom (numerator) Degrees Freedom (denominator) p-value778 15.42 1 433.87 <0.001193.4 Eye Lens Dose Readings by Similarly Exposed GroupA box-and-whisker plot was created to visualize the relationship between similarly exposed group and unat-tenuated (log) eye lens dose readings (Figure 3.2).−1.0−0.50.00.51.0Lower Mainland Nuclear Medicine Lower Mainland Interventional Unattenuated (log) Eye Lens Dose Readings (MilliSieverts)Occupational Limit Threshold ActionFigure 3.2: Unattenuated (log) eye lens dose readings (milliSieverts) by similarly exposed group with quar-terly exposure limit reference. Readings are calculated from eye lens dosimeters. The box’s centre linerepresents the median value for the similarly exposed group. The interquartile ranges (25 and 75 percentile)reach the bottom and top of the box, respectively. The extending vertical lines (whiskers) represent minimumand maximum values. Potential outliers are represented by single dots.Unattenuated eye lens dose was lowest among Lower Mainland Nuclear Medicine. Lower MainlandInterventional showed quarterly exposures beyond the action limit. A one-way Welch’s analysis of variancewas used to test the difference in means between each similarly exposed group and unattenuated eye lensdose readings. A significant difference in unattenuated (log) eye lens dose readings was found between LowerMainland Nuclear Medicine and Lower Mainland Interventional (Table 3.5).20Table 3.5One-Way Welch Analysis of Variance for Unattenuated (log) Eye Lens Dose Reading and Similarly ExposedGroup.n Test Statistic Degrees Freedom (numerator) Degrees Freedom (denominator) p-value778 25.22 1 740.56 <0.0013.5 Predictive Dosimeter ReadingsScatter plots (Figure 3.3 and Figure 3.4) were created to visualize the potential associations between dosime-ters.y = − 0.28 + 0.22 xR2 = 0.1−1.0−0.50.00.51.0−2 −1 0Attenuated (log) Chest Dose Reading (MilliSieverts)Unattenuated (log) Eye Lens Dose Reading (MilliSieverts)Figure 3.3: (log) Attenuated chest and (log) unattenuated eye lens dose readings scatter plot (milliSieverts).Linear regression line with confidence intervals are shown with equation and coefficient of determination topright.Due to a lack of clustered readings in Figure 3.3, there was a weak correlation of determination(𝑅2 = 0.1).21Table 3.6Linear Regression Model Output for Unattenuated (log) Eye Lens and (log) Attenuated Chest Dose Readingsby Estimate (MilliSieverts).Variable Estimate Standard Error t-statistic p-value(Intercept) -0.28 0.08 -3.28 0.002chest 0.22 0.08 2.80 0.007Table (3.6) showed a 1-unit increase in attenuated (log) chest dose reading is associated with a0.22-unit increase in (log) unattenuated eye lens dose readings. Thus, a 1% increase in the attenuated (log)chest dose reading will lead to a 0.22% increase in the unattenuated (log) eye lens dose reading. The t-statistics were large, indicating a small standard error, and p-values showed significant confidence that theregression’s estimate was not zero.y = − 0.12 + 0.62 xR2 = 0.69−1.5−1.0−0.50.00.51.0−2 −1 0 1Unattenuated (log) Collar Dose Reading (MilliSieverts)Unattenuated (log) Eye Lens Dose Reading (MilliSieverts)Figure 3.4: Unattenuated (log) collar and (log) eye lens dose readings scatter plot (milliSieverts). Linearregression line with confidence intervals are shown with equation and coefficient of determination top right.With more clustered readings in Figure 3.4, there was a moderate coefficient of determination(𝑅2 = 0.69).22Table 3.7Linear Regression Model Output for Unattenuated (log) Eye Lens and (log) Collar Dosimeter Readings byEstimate (MilliSieverts).Variable Estimate Standard Error t-statistic p-value(Intercept) -0.12 0.04 -3.33 0.001collar 0.62 0.05 13.14 <0.001Table (3.7) showed a 1-unit increase in unattenuated (log) collar dose reading is associated witha 0.62-unit increase in (log) unattenuated eye lens dose readings. Thus, a 1% increase in the unattenuated(log) collar dose reading will lead to a 0.62% increase in the unattenuated (log) eye lens dose reading. Thet-statistics were large, indicating a small standard error, and p-values showed significant confidence that theregression’s estimate was not zero.3.6 Predictive ModelA fitted model was created to predict unattenuated eye lens dose. The final model used unattenuated(log) collar dose reading to predict unattenuated (log) eye lens dose readings. The final predictive modelhad a multiple R-squared value of 0.69 with a p-value of less than 0.05. Therefore, the model explainsapproximately 69% of the variance in (log) unattenuated eye lens dose.eye = 𝛼+ 𝛽1(collar) + 𝜖 (3.1)Table 3.8Unattenuated (log) Eye Lens Dose Reading Model by Predictor (MilliSieverts)Predictor Estimate Standard Error t-statistic p-valueIntercept -0.12 0.04 -3.33 0.001Collar 0.62 0.05 13.14 <0.001As unattenuated (log) collar dose was the only significant contributor to the model, the findings ofTable (3.7) were applied. A Cook’s distance plot was created to identify potential observations within themodel which may have significantly influenced fitted values of the model (Figure 3.5).230.00.10.20.30.40 20 40 60 80Observation NumberCook's Distance ThresholdFigure 3.5: Cook’s distance bar plot of (log) unattenuated eye lens dose reading model. Readings beyondthe threshold may negatively impact linear regression model and coefficient of variation.There were several readings which may have contributed negatively to the model. Follow-up todetermine the cause and origin of these readings, and their potential exclusion, may positively impact themodel’s coefficient of variation.244 Chapter Four: Discussion4.1 Findings4.1.1 Eye Lens Dose Reading Descriptive StatisticsUsing arithmetic values and methods, mean unattenuated eye lens dose readings for both groups were wellbelow a quarterly action limit of 6.25 milliSieverts. However, Lower Mainland Interventional had maximumunattenuated eye lens dose readings above the quarterly action limit. These findings were consistent witha study of 5,950 healthcare workers between 2012 and 2017 (Bellamy et al., 2020). Bellamy and colleaguesfound low mean dose (0.29 milliSieverts) for all monitored workers. However, two interventional radiologyphysicians had five-year averaged doses of 21 and 40 milliSieverts. This exceeded their study’s threshold of20 milliSieverts per year, averaged over 5 years, with no single year above 50 milliSieverts (InternationalCommission on Radiological Protection, 2012). An investigation into the potential cause(s) of readingsexceeding the action limits should be completed by Lower Mainland Medical Imaging. Future researchshould focus on reviewing correct administrative controls and continuing exposure assessment within LowerMainland Interventional.4.1.2 Dosimeter ComplianceMedian dosimeter compliance was 100% across all quarters within both groups. However, the Welch’sanalysis of variance showed statistically significant differences across mean compliance percentage betweenLower Mainland Nuclear Medicine and Lower Mainland Interventional. To improve consistency, future effortsshould focus on dosimeter compliance results being communicated at the defined similarly exposed grouplevel, as part of research dissemination and knowledge transfer.4.1.3 Unattenuated Eye Lens Dose Readings and GroupLower Mainland Interventional had higher median unattenuated (log) eye lens dose readings, and its outlierscrossed the action limit. Lower Mainland Nuclear Medicine was below the action limit. These findingsare consistent with numerous publications regarding the eye lens dose and nuclear medicine workers. InBellamy and colleagues’ (2020) large study, mean unattenuated eye lens dose to all measurably exposed nu-clear medicine technicians and nurses was 2.2 milliSieverts. This also concurred with a smaller, and shorter,study by Piwowarska-Bilska and colleagues (2018) which found the nuclear medicine department’s mean eye25lens dose was from 0.20 to 0.72 milliSieverts. Their study concluded that the nuclear medicine departmentdoes “not require regular routine eye lens dose monitoring.” Some Lower Mainland Interventional readingshave either exceeded or approached the action limit and should continue monitoring eye lens dose. Furtherinvestigation into the validity of values beyond the action limits should be completed. Lower Mainland Med-ical Imaging should continue to enroll Lower Mainland Interventional participants and begin to analyze thesimilarly exposed group by job classification and procedure. Lower Mainland Nuclear Medicine technologistscan consider discontinuation of dosimetry. Future research should also look to validate the Lower MainlandInterventional similarly exposed group via adjacent collar dosimeter.4.1.4 Unattenuated Eye Lens and Attenuated Chest Dose ReadingsThere was a weak association (𝑅2 = 0.1) between attenuated (log) chest and unattenuated (log) eye lensdose readings. This is likely due to chest dose readings having been placed under lead shielding, as perCanadian Nuclear Safety Commission’s recommendations (2022b). A study by Danaei and colleagues (2021)also found a similarly weak association (𝑅2 = 0.06) when comparing attenuated chest and unattenuated eyelens dose readings. Therefore, the chest dosimeter does not provide a suitable explanation of variance forunattenuated eye lens dose reading.4.1.5 Unattenuated Eye Lens and Unattenuated Collar Dose ReadingsThere was a stronger association (𝑅2 = 0.69) between unattenuated collar and eye lens dosimeters. Thisis further evidence in agreement with Martin’s (2016) conclusions regarding the adequacy of unattenuatedcollar dosimeters in explaining the variance of eye lens dosimeters. Future research can analyze collar andeye lens dose readings within specific departments and job classifications. A larger sample size will likelyimprove estimation of association at lower and higher readings.4.1.6 Predictive ModelThe final predictive model explained 69% of the variance in unattenuated (log) eye lens dose readings. TheCook’s distance bar plot showed several observations exceeded threshold (4/𝑛) and may have influenced themodel. These potential model outliers remained in the data set as further investigation should be conductedto understand their origin and cause. Where unattenuated collar dose readings are captured, adequateestimations of unattenuated eye lens dose readings can be completed. Future research could use the modelto predict unattenuated eye lens dose readings with historical and current quarterly reports.264.2 Limitations4.2.1 Enrollment and DonningAs a secondary data analysis, observations of eye lens dosimeter compliance were not possible to verify.Compliance to study protocol included the correct enrollment of priority employees, as well as correct andconsistent donning of all assigned dosimeters. Employees were instructed in education sessions to weareach dosimeter according to the policies outlined by Lower Mainland Medical Imaging (Appendix D). Siteradiation safety officers and nurse educators were asked to remain vigilant in observation of compliance. Itwas noted on two separate occasions that dosimeters within certain departments had been lost or misplaced.In the event of a lost dosimeter, a new dosimeter was assigned. It was also reported that one dosimeter hadalso been misplaced and found within laboratory clothing. This dosimeter was replaced. As a secondarydata analysis, issuing corrective actions and following up with participants proved challenging, and this mayhave impacted definition of similarly exposed groups and unattenuated eye lens dose readings.4.2.2 Shift DurationHospitals and departments of high priority were included in the study. Priority was determined by length ofexposure to ionizing radiation in terms of proximity and duration to radiological sources. Participants werenot observed for shift duration. It is typical to consider 7.5-hours as a full work day and 37.5 hours as afull work week. However, without observation, shift lengths could have exceeded this in times of necessity orspecial circumstances (e.g., vacation). However, selection of the participant’s highest dose reading attemptedto correct potential fluctuations. Future studies, with greater study duration, may correct fluctuations inwork duration.4.2.3 Dosimeter PlacementCorrect positioning of the dosimeters was essential to reduce potential variance of dose readings acrosshospitals and dosimeters. Participants were also instructed to wear the eye lens dosimeter over lead shieldedglasses. This study did not track compliance to dosimeter positioning, adherence to personal and protectiveequipment guidelines, nor the model of lead glasses worn. Finally, because participants wore the eye lensdosimeter on the outside of the lead glasses, true dose can only be estimated by correcting for the attenuationfactor of the lead glasses. For this, model and type of lead glasses worn by each participant should be recordedto understand the protective factor of the lead glasses. The limitations of COVID-19 and ongoing restrictions27to observe compliance within the similarly exposed groups made the potential impact of non-compliancedifficult to predict and correct.4.2.4 Job ClassificationWhile specific job classifications were a major component of the inclusion criteria, cross-referencing the databeyond the group level proved difficult logistically and administratively. While Lower Mainland MedicalImaging is capable of cross-referencing to the level of job classification, this study component will becomefuture research and potential publication. With data collection still in progress, the manuscript will includea greater sample size and more job classifications for analysis of variation. If accepted for publication, thisresearch will become the largest study of eye lens dose readings in Canada.4.2.5 Workplace RestrictionsDue to the ongoing COVID-19 pandemic, location access was closed for researchers. These closures andrestrictions had an immeasurable impact on the study from its initial stages. The study was originallydesigned as an observational study, to ensure compliance. While accommodations were made to communicateremotely, participant feedback was limited.4.3 Knowledge Transfer and Exchange4.3.1 Information SharingInformation will be shared within Lower Mainland Medical Imaging via presentations and information sharingwith participants, radiation safety officers, and occupational health and safety teams. Information sessionswill be delivered to all stakeholders via internal group meetings and open-enrollment sessions.4.3.2 Future ResearchFurther research can focus on full year exposure data, cross-referencing exposure data with job classification,enrolling more participants, and confirming similarly exposed groups. A long-term case-cohort study couldbe designed in the event of eye lens opacity development among participants.285 Chapter Five: ConclusionExtended and proximal exposures to ionizing radiation may impact the tissue of eye lens more than previouslyunderstood. In the workplace, proximity and duration to ionizing radiation may increase depending on jobclassification. Similarly exposed groups within Lower Mainland Medical Imaging’s jurisdiction have beenidentified and followed for a period of six months. The highest of the participants’ quarterly exposurereadings were used for analysis. Due to significantly lower unattenuated eye lens dose readings, technicianswithin Lower Mainland Nuclear Medicine may be considered for discontinuation of eye lens dose assessment.Lower Mainland Interventional should continue evaluation of unattenuated eye lens dose readings due topotential exceedance of action limits. Finally, the collar dosimeter offered an adequate potential substitutionfor eye lens dosimeters, where lower priority or difficulty donning may occur.29BibliographyAinsbury, E. A., Bouffler, S. D., Dörr, W., Graw, J., Muirhead, C. R., Edwards, A. A., & Cooper,J. (2009). Radiation cataractogenesis: A review of recent studies [Journal Article]. Radiat Res,172(May 11, 2021), 1–9. https://doi.org/10.1667/rr1688.1Apelmann, C., Kowald, B., Weinrich, N., Dischinger, J., Nienhaus, A., Seide, K., Martens, H., &Jürgens, C. (2019). Radiation dose to the eye lens through radiological imaging procedures at thesurgical workplace during trauma surgery [Journal Article]. 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Charge Nurses who do not rotate greater than half of their time close to a patient.Contact InformationEmployee:Employee email address:Hospital:Department:35Study Participant DetailsFill in total number of participants who meet inclusion criteria from appropriate department(s).Table A.1Job Title Inclusion by Department (Alphabetical)Department Job Title NumberCatheterization Lab Interventional CardiologistsFellowsNursesEndoscopy PhysiciansFellowsNuclear Medicine TechnologistsOrthopaedic Surgery SurgeonsRadiology Interventional RadiologistFellowsNursesTechnologistsUrology UrologistsFellowsVascular Surgery SurgeonsFellows36Appendix B - Dosimetry Service Poster 2021 Version: 2.1. | Last Revision: June 2021 | Replaces: January 2016 | Originally Created: April 2010 Radiation Safety Poster: Personal Dosimetry Monitoring in X-ray Areas • The dosimeters for whole body, collar and fetal monitoring have icons to identify the wear locations on your body. Whole Body Dosimeter Collar Dosimeter Fetal Dosimeter Eye Dosimeter (For project use) Wear on the front of the torso between the waist and shoulder. The label must away from the body. Place under lead apron. Wear at the front of the body at neck level. The label must face away from the body. Place over lead apparel. Wear at the waist on the abdomen. The label must face away from the body. Place under lead apron. The label must face away from the body. Surgeons: clipped on glasses, headband, or cap in front of and as close to the most exposed eye as possible. Other staff: clipped on at the side close to the most exposed eye. How to wear your dosimeter(s)? Who wears personal dosimeter(s)? How many dosimeters do you wear? • Dosimeters will be assigned where there is reasonable probability that a worker may receive more than 1 mSv annually. • The number and types of dosimeters assigned will depend on which department you work in and the type of work you do. What do you need to do? • Wear your dosimeters at all times during your shift. • Never leave your dosimeters on protective apparel or near x-ray equipment/radioactive substances when not in use. • Return your dosimeters to the badge storage location in your department after each shift. • Never store dosimeters inside your locker, or take them home (except for regional workers like biomed staff) • Review dosimeter reports and initial to acknowledge that you have review your dose. • Inform your dosimetry contact person / administrator of any incident involving your dosimeters (accidental exposure, lost dosimeter, etc). For More Information, contact your dosimetry contact person / administrator or the Site Radiation Safety Officer. Retiring, resigning or on maternity/other leave: please notify your dosimetry contact person of your last date of work. Return your dosimeters to the contact person. Figure B.1: Dosimetry Service Poster 2021.37Appendix C - Eye Lens Study In-Service PresentationFigure C.1: Behavioural Research Ethics Board approved presentation, slide 1.Figure C.2: Behavioural Research Ethics Board approved presentation, slide 2.38Figure C.3: Behavioural Research Ethics Board approved presentation, slide 3.Figure C.4: Behavioural Research Ethics Board approved presentation, slide 4.39Figure C.5: Behavioural Research Ethics Board approved presentation, slide 5.Figure C.6: Behavioural Research Ethics Board approved presentation, slide 6.40Figure C.7: Behavioural Research Ethics Board approved presentation, slide 7.Figure C.8: Behavioural Research Ethics Board approved presentation, slide 8.41Figure C.9: Behavioural Research Ethics Board approved presentation, slide 9.Figure C.10: Behavioural Research Ethics Board approved presentation, slide 10.42Figure C.11: Behavioural Research Ethics Board approved presentation, slide 11.Figure C.12: Behavioural Research Ethics Board approved presentation, slide 12.43Figure C.13: Behavioural Research Ethics Board approved presentation, slide 13.Figure C.14: Behavioural Research Ethics Board approved presentation, slide 14.44Figure C.15: Behavioural Research Ethics Board approved presentation, slide 15.Figure C.16: Behavioural Research Ethics Board approved presentation, slide 16.45Appendix D - Data DictionaryLocation: Identified by the first acronym in the file title. Categorical variable.Department: Identified by the second acronym in the file title. Categorical variable.Year: Year of the dosimetry record. Categorical variable.Quarter: quarter of the dosimetry record. Categorical variable.N: number of assigned dosimeters.U: number of unused assigned dosimeters.Compliance: percentage of unused dosimeters from assigned dosimeters. Continuous variable.Total readings: number of dosimeters assigned for the quarter.#M: number of readings below minimal reporting capabilities. After the control subtraction, theresulting occupational dose was below the minimal reporting capabilities of the dosimeter.%M: percentage of “M” readings from total readings.#B: Number of beta radiation readings.%B: percentage of “B” readings from total readings.#P: Number of photon radiation readings.%P: percentage of “P” readings from total readings.Max: maximum dose reading for assigned period. Continuous variable.Min: minimum dose reading for assigned period. Continuous variable.Ave: average dose reading for assigned period. Continuous variable.LDE: Lens dose equivalent applies to external exposure of the lens at a tissue depth of 3 mil-limetres.SDE: Shallow dose equivalent applies to the external exposure of the skin or extremity at a tissuedepth of 0.07 millimetres.46Appendix E - Data Transformation02040600 2 4 6 8dose_averagedensityFigure E.1: Unattenuated eye lens dose reading histogram (untransformed).4702468−2 −1 0 1 2xyFigure E.2: Unattenuated eye lens dose reading quantile-quantile plot (untransformed).051015−1.0 −0.5 0.0 0.5 1.0log_dose_averagedensityFigure E.3: Unattenuated eye lens dose reading histogram (log-transformed).48−1.5−1.0−0.50.00.51.0−2 −1 0 1 2xyFigure E.4: Unattenuated eye lens dose reading quantile-quantile plot (log-transformed).49Appendix F - Research DatabaseTable F.1Total Results by Query from Ovid MEDLINE DatabaseNumber Query Result (as of March 23, 2021)1 impact of radiation protection means on thedose to the lens of the eye.m_titl.12 (lens or eye or cataract*).mp. [mp=title,abstract, original title, name of substanceword, subject heading word, floatingsub-heading word, keyword heading word,organism supplementary concept word,protocol supplementary concept word, raredisease supplementary concept word, uniqueidentifier, synonyms]476,5803 (radiation or x-ray or fluoroscopy).mp.[mp=title, abstract, original title, name ofsubstance word, subject heading word,floating sub-heading word, keyword headingword, organism supplementary conceptword, protocol supplementary concept word,rare disease supplementary concept word,unique identifier, synonyms]1,407,6384 2 and 3 22,8305 (technologist* or nurse* or cardiologist* orradiolog* or hospital* or nuclear medicine ororthopedic* or surgeon*).mp. [mp=title,abstract, original title, name of substanceword, subject heading word, floatingsub-heading word, keyword heading word,organism supplementary concept word,protocol supplementary concept word, raredisease supplementary concept word, uniqueidentifier, synonyms]2,467,8996 4 and 5 2,4467 (exposure* or threshold or absorption).mp.[mp=title, abstract, original title, name ofsubstance word, subject heading word,floating sub-heading word, keyword headingword, organism supplementary conceptword, protocol supplementary concept word,rare disease supplementary concept word,unique identifier, synonyms]1,523,8148 6 and 7 72950
Thesis/Dissertation
eng
Occupational and Environmental Hygiene
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Graduate
Bartlett, Karen H.
An evaluation of occupational health and safety changes to eye lens dose in nuclear medicine and interventional departments of Lower Mainland Medical Imaging
Text