An osteogenic sarcoma arose in the right orbit of a 7-year-old boy some 5 years after the right orbit had been treated by four courses of radiotherapy (total dose approximately 13,000 rads) for a multicentric retinoblastoma. Death occurred 6 months after the orbital tumor was first detected. Study of the orbital tumor by electron microscopy revealed a cell population of varied morphology in which two main types were identified. In one group, the cells were large with radiolucent cytoplasm, which contained long branching segments of rough endoplasmic reticulum. In the second group, the cells were smaller with irregular nuclei and an electron-dense cytoplasm, which contained short segments of dilated rough endoplasmic reticulum and numerous mitochondria. The first group of cells closely resembled osteoblasts, while the second group had some features of osteoclasts or their percursors. The branching processes of the tumor cells were separated by an amorphous ground substance, which contained collagen-like fibrils and hydroxyapatite crystals. Crystal deposition was in some instances in close relation to extracellular membrane-bound vesicles.

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An optimization system using score functions to gauge the criteria used in treatment planning is described. A comparison is made between the results obtained by this system and the views of a group of radiotherapists. This comparison shows that the basic concept of calculated judgement by computer and t'he relatively simple and fast methods used are applicable to the majority of 4 Mev treatment planning situations. The role of this system in the development of radiotherapy is discussed.

No abstract

AT the Western Infimary, Glasgow, cervix radium treatment is done by the Manchester technique (Tod and Meredith 1938), using ovoids and a flexible uterine tube. The dose-distribution in the pelvis depends on the anatomical positions of the vagina and the uterus.This arrangement of a few strong sources produces a distribution containing regions of steep gradient, Dosage is based on t.hat received by the paracervical triangle (Todd 1938), which is taken as being represented