CANADIAN MEDICAL PHYSICS NEWSLETTER nterACTIONS Le BULLETIN CANADIEN de PHYSIQUE MÉDICALE a b C A B c d PUBLICATIONS MAIL AGREEMENT NO. 40049361 RETURN UNDELIVERABLE CANADIAN ADDRESSES TO: BARB CALLAGHAN C/O NOLAN DRUGS POST OFFICE 8901 118th AVENUE EDMONTON, AB T5B 0T5 A publication of the Canadian Organization of Medical Physicists and the Canadian College of Physicists in Medicine http://www.medphys.ca Images from prototype MVCT ISSN 1488-6847 scanner in Cobalt-60 beam 51 (2) avril/April 2005 About our Cover COMP EXECUTIVE These images were obtained by a prototype, bench-top, third generation megavoltage computed tomography (MVCT) scanner in a Co60 beam. The Chair: system uses an 80-element detector array of CdWO4 crystals and photodiodes, Mr. Peter O’Brien arranged on an arc of radius 110 cm. This phantom (module CTP612 in Toronto-Sunnybrook Regional CATPHAN500, Phantom Labs) was especially designed for MVCT, and Cancer Centre 2075 Bayview Avenue consists of inserts at 3%, 2.5% and 1.5% nominal contrast levels. Each contrast Toronto, ON, M4N 3M5 level has cylinders of diameters 2, 0.4, 0.5, 0.6, 0.7, 0.8 and 1.5 cm, and there is Tel: (416) 480-4622 a central cylinder of 0.4 cm diameter with a contrast level of 1.5 %. The dose to Fax: (416) 480-6801 the centre of the phantom was estimated to be approximately 17 cGy when all peter.o’
[email protected] the projections were used in the reconstruction process. Images with doses of Past Chair: 8.5, 4.3 and 2.1 cGy were obtained by utilising only one-half, one-fourth and Dr.