title: Preliminary clinical performance of a scanning detector for rapid portal imaging.
abstract: A scanning megavoltage imaging detector, with associated image storage and analysis facilities has been developed. This produces images of the treatment portals in under 10 seconds, in a digital format, facilitating rapid, quantitative image analysis. Image quality is comparable to, and at some sites improves upon, that available from film. Clinical problems in the use of megavoltage imaging include limited field of view, loss of information at the field edge due to penumbra effects, degradation of the image by bowel gas, and difficulties in the detection of soft tissue-air interfaces. Possible solutions to these problems are discussed. The imaging system has been used to assess the random errors occurring during routine para-aortic nodal irradiation. The errors detected are small, with over 95% of set-ups lying within +/- 4.5 mm of the mean daily position. No differences were detected in the magnitude of random errors between anterior and posterior treatment fields.
authors.affiliation: Department of Radiotherapy, Royal Marsden Hospital, Sutton, Surrey, UK.
authors.forename: J
authors.initials: J
authors.lastname: Gildersleve
authors.forename: D
authors.initials: D
authors.lastname: Dearnaley
authors.forename: P
authors.initials: P
authors.lastname: Evans
authors.forename: E
authors.initials: E
authors.lastname: Morton
authors.forename: W
authors.initials: W
authors.lastname: Swindell
mesh_terms: D001011:Aorta; D016477:Artifacts; D003626:Data Display; D004867:Equipment Design; D005740:Gases; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D007422:Intestines; D008198:Lymph Nodes / Q000528:radiation effects; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation*; D011882:Radiotherapy, High-Energy / Q000295:instrumentation; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D012984:Software
chemical_list: D005740:Gases