Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1880107 | Medical Dosimetry | 2012 | 5 Pages |
Abstract
The goal of this work was to use daily kV-kV imaging and weekly cone-beam CT (CBCT) to evaluate rectal cancer patient position when treated on a new couch top belly board (BB). Quality assurance (QA) of the imaging system was conducted weekly to ensure proper performance. The positional uncertainty of the combined kV-kV image match and subsequent couch move was found to be no more than ± 1.0 mm. The average (1 SD) CBCT QA phantom match was anterior-posterior (AP) = â0.8 ± 0.2 mm, superior-inferior (SI) = 0.9 ± 0.2 mm, and left-right (LR) = â0.1 ± 0.1 mm. For treatment, a set of orthogonal kV-kV images were taken and a bony anatomy match performed online. Moves were made along each axis (AP, SI, and LR) and recorded for analysis. CBCT data were acquired once every 5 fractions for a total of 5 images per patient. The images were all taken after the couch move but before treatment. A 3-dimensional (3D-3D) bony anatomy auto-match was performed offline and the residual difference in position recorded for analysis. The average (± 1 SD) move required from skin marks, calculated over all 375 fractions (15 patients à 25 fractions/patient), were AP = â2.6 ± 3.7 mm, SI = â0.3 ± 4.9 mm, and LR = 1.8 ± 4.5 mm. The average residual difference in patient position calculated from the weekly CBCT data (75 total) were AP = â1.7 ± 0.4 mm, SI = 1.1 ± 0.6 mm, and LR = â0.5 ± 0.2 mm. These results show that the BB does provide simple patient positioning that is accurate to within ± 2.0 mm when using online orthogonal kV-kV image matching of the pelvic bony anatomy.
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Authors
Gavin M.Sc., Vijayananda M.D., D.M.R.T., F.R.C.R., Deluan M.Sc., Shyanne Ternes, Haresh M.D., D.G.O., F.R.C.R., Narinder P. Ph.D., F.C.C.P.M., D.A.B.M.P.,