Total-body irradiation (nn) is a therapy modality that is being used wilh inaeasing kquency, in conjunction wilh chemotherapy, for patients undergoing b o n e -m o w transplantation. At the Ottawa Regional Cancer centre a technique has been developed for the delivery of ~B Ito patients prior to bo~marrow transplantation. In this technique pakients are treafed on a mobile couch at approximately 195 cm SSD with a field size of 66.5 cm wide by 57 cm long. A computersontrolled stepping motor drives the patient couch at a user-selectable speed. The total dose delivered to the patient is a function of couch velocity, field size and patient separation. T"II times are of Le order of 10 min for each of the anterior and posterior fields for a 400 ffiy fraclion. It has been found that Le wnventional m k a l axis tissue maximum ntio (m) and percentage depth dose (PDD) functions are not appropiiate for describing dose delivered during dynamic t"er!l.To this end we have developed dynamic m and EUD functions. Extensive measurements have been performed in an anthropomorphic water phantom to detemine the dose dishibutions in three dimensions and the efficacy of polymethyl methacrylate (PU) bean spoilers as a replacement for anterior and lateral bolus.It has been found that 2.4 cm PMMA spoilers do provide full skin dose and negate the requirement for laled bolus. This 181 procedure is simple, rapid and appears to be well tolerated by the paIients. 55 patients have been hated since the i n m d d o n of this technique in 1991.

Stereotactic radiosurgery (SRS) treatment is characterized by high doses per fraction and extremely steep dose gradients. This requires a great degree of accurate localization to the appropriate treatment position, and continuous immobilization during the treatment session. In the case of Trigeminal Neuralgia (TGN) treatment this is especially true as the very small target volume makes positional accuracy critical. In this study we carried out a quantitative analysis of patient motion during the full treatment fraction within a radiosurgery immobilization mask system. Patient cranial movement was assessed by using the image guidance stereo x-ray cameras on a CyberKnife (CK) M6 robotic radiosurgery system (Accuray, Sunnyvale, CA). A total of five patients received treatments for either right or left TGN. The duration of treatment varied from 24-64 minutes. Orthogonal images were taken every 15 seconds during the treatment to assess patient movement. Approximately 60 stereo images were taken per patient and a total of 560 images were analyzed in this study. The mean absolute movement in each of longitudinal, lateral or vertical directions was approximately 0.3 mm for the duration of the treatment; however, on occasion much greater movement was observed during a fraction. The maximum displacement was in the longitudinal direction and reached 2.4 mm compared to the initial setup. Images taken at the end of the treatment session showed that the patients typically return to a position closer to the original setup position than the maximum excursion that occurred. This data suggests that although this mask system appears stable during much of the treatment session; for some patients there may be momentary patient movements that take place. Frequent imaging and correction can help mitigate the effect of this movement. It is important to understand the limitations of non-invasive mask systems when used for very high precision treatment.

High plan quality for complex spinal radiosurgery was achieved among all systems and all participating centers in this planning challenge. This study concludes that simple IMAT techniques can generate significantly better plan quality compared to previous established CKRS benchmarks.

No abstract