PURPOSE: The ability to determine the accuracy of the final prostate position within a determined action level threshold for image-guided proton therapy is unclear. MATERIALS AND METHODS: Three thousand one hundred ten images for 20 consecutive patients treated in 1 of our 3 proton prostate protocols from February to May of 2007 were analyzed. Daily kV images and patient repositioning were performed employing an action-level threshold (ALT) of > or = 2.5 mm for each beam. Isocentric orthogonal x-rays were obtained, and prostate position was defined via 3 gold markers for each patient in the 3 axes. RESULTS: To achieve and confirm our action level threshold, an average of 2 x-rays sets (median 2; range, 0-4) was taken daily for each patient. Based on our ALT, we made no corrections in 8.7% (range, 0%-54%), 1 correction in 82% (41%-98%), and 2 to 3 corrections in 9% (0-27%). No patient needed 4 or more corrections. All patients were treated with a confirmed error of < 2.5 mm for every beam delivered. After all corrections, the mean and standard deviations were: anterior-posterior (z): 0.003 +/- 0.094 cm; superior-inferior (y): 0.028 +/- 0.073 cm; and right-left (x) -0.013 +/- 0.08 cm. CONCLUSION: It is feasible to limit all final prostate positions to less than 2.5 mm employing an action level image-guided radiation therapy (IGRT) process. The residual errors after corrections were very small.
PURPOSE: The ability to determine the accuracy of the final prostate position within a determined action level threshold for image-guided proton therapy is unclear. MATERIALS AND METHODS: Three thousand one hundred ten images for 20 consecutive patients treated in 1 of our 3 proton prostate protocols from February to May of 2007 were analyzed. Daily kV images and patient repositioning were performed employing an action-level threshold (ALT) of > or = 2.5 mm for each beam. Isocentric orthogonal x-rays were obtained, and prostate position was defined via 3 gold markers for each patient in the 3 axes. RESULTS: To achieve and confirm our action level threshold, an average of 2 x-rays sets (median 2; range, 0-4) was taken daily for each patient. Based on our ALT, we made no corrections in 8.7% (range, 0%-54%), 1 correction in 82% (41%-98%), and 2 to 3 corrections in 9% (0-27%). No patient needed 4 or more corrections. All patients were treated with a confirmed error of < 2.5 mm for every beam delivered. After all corrections, the mean and standard deviations were: anterior-posterior (z): 0.003 +/- 0.094 cm; superior-inferior (y): 0.028 +/- 0.073 cm; and right-left (x) -0.013 +/- 0.08 cm. CONCLUSION: It is feasible to limit all final prostate positions to less than 2.5 mm employing an action level image-guided radiation therapy (IGRT) process. The residual errors after corrections were very small.
Authors: Carlos Enrique Vargas; William Fred Hartsell; Megan Dunn; Sameer Ramchandra Keole; Lucius Doh; John Chang; Gary Lynn Larson Journal: Rep Pract Oncol Radiother Date: 2016-03-04
Authors: Carlos E Vargas; Matthew Q Schmidt; Joshua R Niska; William F Hartsell; Sameer R Keole; Lucius Doh; John Han-Chih Chang; Christopher Sinesi; Rossio Rodriquez; Mark Pankuch; Gary L Larson Journal: Adv Radiat Oncol Date: 2018-02-23