Yang Sheng1, Taoran Li2, W Robert Lee3, Fang-Fang Yin4, Q Jackie Wu4. 1. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina; Medical Physics Graduate Program, Duke University, Durham, North Carolina. Electronic address: Yang.Sheng@duke.edu. 2. Medical Physics Graduate Program, Duke University, Durham, North Carolina; Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania. 3. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina. 4. Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina; Medical Physics Graduate Program, Duke University, Durham, North Carolina.
Abstract
PURPOSE: To provide a benchmark for seminal vesicle (SV) margin selection to account for intrafractional motion and to investigate the effectiveness of 2 motion surrogates in predicting intrafractional SV coverage. METHODS AND MATERIALS: Fifteen prostate patients were studied. Each patient had 5 pairs (1 patient had 4 pairs) of pretreatment and posttreatment cone beam CTs (CBCTs). Each pair of CBCTs was registered on the basis of prostate fiducial markers. All pretreatment SVs were expanded with 1-, 2-, 3-, 4-, 5-, and 8-mm isotropic margins to form a series of planning target volumes, and their intrafractional coverage to the posttreatment SV determined the "ground truth" for exact coverage. Two motion surrogates, the center of mass (COM) and the border of contour, were evaluated by the use of Pearson product-moment correlation coefficient and exponential fitting for predicting SV underdosage. Action threshold of each surrogate was calculated. The margin for each surrogate was calculated according to a traditional margin recipe. RESULTS: Ninety-five percent posttreatment SV coverage was achieved in 9%, 53%, 73%, 86%, 95%, and 97% of fractions with 1-, 2-, 3-, 4-, 5-, and 8-mm margins, respectively. The 5-mm margins provided 95% intrafractional SV coverage in over 90% of fractions. The correlation between the COM and border was weak, moderate, and strong in the left-right (L-R), anterior-posterior (A-P), and superior-inferior (S-I) directions, respectively. Exponential fitting gave the underdosage threshold of 4.5 and 7.0 mm for the COM and border. The Van Herk margin recipe recommended 0-, 0.5-, and 0.8-mm margins in the L-R, A-P, and S-I directions based on the COM, and 1.2-, 3.9-, and 2.5-mm margins based on the border. CONCLUSIONS: Five-millimeter isotropic margins for the SV constitute the minimum required to mitigate the intrafractional motion. Both the COM and the border are acceptable predictors for SV underdosage with 4.5- and 7.0-mm action threshold. Traditional margin based on the COM or border underestimates the margin.
PURPOSE: To provide a benchmark for seminal vesicle (SV) margin selection to account for intrafractional motion and to investigate the effectiveness of 2 motion surrogates in predicting intrafractional SV coverage. METHODS AND MATERIALS: Fifteen prostate patients were studied. Each patient had 5 pairs (1 patient had 4 pairs) of pretreatment and posttreatment cone beam CTs (CBCTs). Each pair of CBCTs was registered on the basis of prostate fiducial markers. All pretreatment SVs were expanded with 1-, 2-, 3-, 4-, 5-, and 8-mm isotropic margins to form a series of planning target volumes, and their intrafractional coverage to the posttreatment SV determined the "ground truth" for exact coverage. Two motion surrogates, the center of mass (COM) and the border of contour, were evaluated by the use of Pearson product-moment correlation coefficient and exponential fitting for predicting SV underdosage. Action threshold of each surrogate was calculated. The margin for each surrogate was calculated according to a traditional margin recipe. RESULTS: Ninety-five percent posttreatment SV coverage was achieved in 9%, 53%, 73%, 86%, 95%, and 97% of fractions with 1-, 2-, 3-, 4-, 5-, and 8-mm margins, respectively. The 5-mm margins provided 95% intrafractional SV coverage in over 90% of fractions. The correlation between the COM and border was weak, moderate, and strong in the left-right (L-R), anterior-posterior (A-P), and superior-inferior (S-I) directions, respectively. Exponential fitting gave the underdosage threshold of 4.5 and 7.0 mm for the COM and border. The Van Herk margin recipe recommended 0-, 0.5-, and 0.8-mm margins in the L-R, A-P, and S-I directions based on the COM, and 1.2-, 3.9-, and 2.5-mm margins based on the border. CONCLUSIONS: Five-millimeter isotropic margins for the SV constitute the minimum required to mitigate the intrafractional motion. Both the COM and the border are acceptable predictors for SV underdosage with 4.5- and 7.0-mm action threshold. Traditional margin based on the COM or border underestimates the margin.
Authors: Shyama U Tetar; Anna M E Bruynzeel; Lisa Verweij; Omar Bohoudi; Berend J Slotman; Tezontl Rosario; Miguel A Palacios; Frank J Lagerwaard Journal: Phys Imaging Radiat Oncol Date: 2022-07-03
Authors: Farshad Mostafaei; An Tai; Eenas Omari; Yingqiu Song; James Christian; Eric Paulson; William Hall; Beth Erickson; X Allen Li Journal: PLoS One Date: 2018-10-25 Impact factor: 3.240
Authors: Flora Goupy; Stéphane Supiot; David Pasquier; Igor Latorzeff; Ulrike Schick; Erik Monpetit; Geoffrey Martinage; Chloé Hervé; Bernadette Le Proust; Joel Castelli; Renaud de Crevoisier Journal: PLoS One Date: 2019-01-25 Impact factor: 3.240