Tracy S Bray1, Adelaide Kaczynski2, Kevin Albuquerque2, Francesca Cozzi2, John C Roeske2. 1. Department of Radiation Oncology, Loyola University Medical Center, Maywood, Illinois. Electronic address: tbray@lumc.edu. 2. Department of Radiation Oncology, Loyola University Medical Center, Maywood, Illinois.
Abstract
PURPOSE: We investigated the effect of body mass index on setup errors by analyzing daily shifts required in treating patients undergoing image guided radiation therapy (IGRT) for gynecologic malignancies. METHODS AND MATERIALS: Forty successive patients treated with daily kV-based IGRT for gynecologic malignancies between April 2009 and June 2012 were identified. Directional setup corrections were analyzed according to patient body mass index. Random and systematic setup errors were calculated. Image acquisition dose was estimated by performing ionization chamber measurements in a phantom. RESULTS: Obese patients had larger random setup errors, particularly in the right-left (R-L) direction, with a setup error of 7.6 mm, versus 3.9 mm for nonobese patients. The range of individual patient random errors in the R-L direction was 1.5 to 7.6 mm among nonobese patients versus 2.0 to 17.0 mm among obese patients (P = .03, F-test). For obese patients, daily IGRT prevented treating outside the planning target volume in 33% of fractions, versus 16% in the nonobese group (P = .001). The mean total image acquisition dose from daily kV-IGRT was approximately 3 cGy, versus 150 cGy if daily megavoltage portal imaging were used to correct for erratic setup errors. CONCLUSIONS: Daily kV-based IGRT in obese patients allows for correction of erratic setup error and minimizes excess dose from portal imaging.
PURPOSE: We investigated the effect of body mass index on setup errors by analyzing daily shifts required in treating patients undergoing image guided radiation therapy (IGRT) for gynecologic malignancies. METHODS AND MATERIALS: Forty successive patients treated with daily kV-based IGRT for gynecologic malignancies between April 2009 and June 2012 were identified. Directional setup corrections were analyzed according to patient body mass index. Random and systematic setup errors were calculated. Image acquisition dose was estimated by performing ionization chamber measurements in a phantom. RESULTS:Obesepatients had larger random setup errors, particularly in the right-left (R-L) direction, with a setup error of 7.6 mm, versus 3.9 mm for nonobese patients. The range of individual patient random errors in the R-L direction was 1.5 to 7.6 mm among nonobese patients versus 2.0 to 17.0 mm among obesepatients (P = .03, F-test). For obesepatients, daily IGRT prevented treating outside the planning target volume in 33% of fractions, versus 16% in the nonobese group (P = .001). The mean total image acquisition dose from daily kV-IGRT was approximately 3 cGy, versus 150 cGy if daily megavoltage portal imaging were used to correct for erratic setup errors. CONCLUSIONS: Daily kV-based IGRT in obesepatients allows for correction of erratic setup error and minimizes excess dose from portal imaging.
Authors: A Smits; J McGrane; A Lopes; E Kent; R Bekkers; L Massuger; N Simpson; K Galaal Journal: Int J Clin Oncol Date: 2017-06-15 Impact factor: 3.402
Authors: Arya Amini; Peter E DeWitt; Yevgeniy Vinogradskiy; Chad G Rusthoven; Cem Altunbas; Tracey E Schefter; Christine M Fisher Journal: Rep Pract Oncol Radiother Date: 2016-03-02