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The effect of single and fractionated dose radiation on craniofacial growth in rats Lynch, Andrea M.


Bone marrow transplant (BMT) preparative regimens for children usually include total body irradiation in combination with chemotherapy. Abnormal growth and endocrine deficiencies have been observed in children after BMT (Sanders 1988). Although the detrimental effects of localized high dose irradiation on craniofacial growth and development are well documented, little is known of the effects of low dose irradiation. The purpose of this study was to determine the effect of single and fractionated dose irradiationon craniofacial growth in rats. Eighty seven male Sprague-Dawley rats were randomly assigned to seven experimental groups. Two groups (Si, S2) received single dose irradiation ranging from 200 to 500 cGy at two days of age. Four groups (F1, F2, F3, F4) received six fractionated irradiation doses ranging from 250 to 600 cGy, administered between two and four days of age. The seventh group (control), received sham irradiation. Weekly weight, length and cephalometric radiographs were taken of each animal from week one to week eight, and again at twenty-one weeks when the animals were killed. Craniofacial growth changes were determined by measurement of sequential lateral cephalographs. Post-mortem mature skulls were measured by metrographic techniques. Both single and fractionated dose irradiation significantly affected body weight, while only high single dose irradiation influenced body length. Longitudinal data derived from cephalometric radiographs demonstrated that in general the high single dose group was significantly different from the control group in all measurements except neurocranial length. No significant differences were seen between control and low fractionated groups in any measurements except neurocranial height. Cross-sectional analysis of mature skulls using metrographic measurement techniques demonstrated significant differences in cranial length, viscerocranial length, mandibular width, bizygomatic width and height of the cranial vault between control and high single and fractionated dose (Si, S2, F4) irradiation, and between high (F4) and low fractionated dose (Ft F2, F3) irradiation. In conclusion, fractionated low dose irradiation has less significant effect on craniofacial growth than high single dose irradiation, and viscerocranial growth was more affected by irradiation than neurocranial growth.

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