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RISS 인기검색어
- 검색키워드
- 저자 : Hintenlang, Kathleen (검색결과 2 건)
- 무료
- 기관 내 무료
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Smith, Ashley,Kim, Siyong,Serago, Christopher,Hintenlang, Kathleen,Ko, Stephen,Vallow, Laura,Peterson, Jennifer,Hintenlang, David,Heckman, Michael,Buskirk, Steven Korean Society of Medical Physics 2014 의학물리 Vol.25 No.4
Dynamic conformal arc therapy (DCAT) and flattening-filter-free (FFF) beams are commonly adopted for efficient conformal dose delivery in stereotactic body radiation therapy (SBRT). Off-axis geometry (OAG) may be necessary to obtain full gantry rotation without collision, which has been shown to be beneficial for peripheral targets using flattened beams. In this study dose distributions in OAG using FFF were evaluated and the effect of mechanical rotation induced uncertainty was investigated. For the lateral target, OAG evaluation, sphere targets (2, 4, and 6 cm diameter) were placed at three locations (central axis, 3 cm off-axis, and 6 cm off-axis) in a representative patient CT set. For each target, DCAT plans under the same objective were obtained for 6X, 6FFF, 10X, and 10FFF. The parameters used to evaluate the quality of the plans were homogeneity index (HI), conformality indices (CI), and beam on time (BOT). Next, the mechanical rotation induced uncertainty was evaluated using five SBRT patient plans that were randomly selected from a group of patients with laterally located tumors. For each of the five cases, a plan was generated using OAG and CAG with the same prescription and coverage. Each was replanned to account for one degree collimator/couch rotation errors during delivery. Prescription isodose coverage, CI, and lung dose were evaluated. HI and CI values for the lateral target, OAG evaluation were similar for flattened and unflattened beams; however, 6FFF provided slightly better values than 10FFF in OAG. For all plans the HI and CI were acceptable with the maximum difference between flattened and unflattend beams being 0.1. FFF beams showed better conformality than flattened beams for low doses and small targets. Variation due to rotational error for isodose coverage, CI, and lung dose was generally smaller for CAG compared to OAG, with some of these comparisons reaching statistical significance. However, the variations in dose distributions for either treatment technique were small and may not be clinically significant. FFF beams showed acceptable dose distributions in OAG. Although 10FFF provides more dramatic BOT reduction, it generally provides less favorable dosimetric indices compared to 6FFF in OAG. Mechanical uncertainty in collimator and couch rotation had an increased effect for OAG compared to CAG; however, the variations in dose distributions for either treatment technique were minimal.
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Ashley Smith,Siyong Kim,Kathleen Hintenlang,Stephen Ko,Laura Vallow,Jennifer Peterson,David Hintenlang,Michael Heckman,Steven Buskirk 한국의학물리학회 2014 의학물리 Vol.25 No.4
Dynamic conformal arc therapy (DCAT) and flattening-filter-free (FFF) beams are commonly adopted for efficientconformal dose delivery in stereotactic body radiation therapy (SBRT). Off-axis geometry (OAG) may benecessary to obtain full gantry rotation without collision, which has been shown to be beneficial for peripheraltargets using flattened beams. In this study dose distributions in OAG using FFF were evaluated and the effectof mechanical rotation induced uncertainty was investigated. For the lateral target, OAG evaluation, sphere targets(2, 4, and 6 cm diameter) were placed at three locations (central axis, 3 cm off-axis, and 6 cm off-axis) ina representative patient CT set. For each target, DCAT plans under the same objective were obtained for 6X,6FFF, 10X, and 10FFF. The parameters used to evaluate the quality of the plans were homogeneity index (HI),conformality indices (CI), and beam on time (BOT). Next, the mechanical rotation induced uncertainty wasevaluated using five SBRT patient plans that were randomly selected from a group of patients with laterally locatedtumors. For each of the five cases, a plan was generated using OAG and CAG with the same prescription andcoverage. Each was replanned to account for one degree collimator/couch rotation errors during delivery. Prescription isodose coverage, CI, and lung dose were evaluated. HI and CI values for the lateral target, OAGevaluation were similar for flattened and unflattened beams; however, 6FFF provided slightly better values than10FFF in OAG. For all plans the HI and CI were acceptable with the maximum difference between flattened andunflattend beams being 0.1. FFF beams showed better conformality than flattened beams for low doses andsmall targets. Variation due to rotational error for isodose coverage, CI, and lung dose was generally smallerfor CAG compared to OAG, with some of these comparisons reaching statistical significance. However, thevariations in dose distributions for either treatment technique were small and may not be clinically significant. FFF beams showed acceptable dose distributions in OAG. Although 10FFF provides more dramatic BOTreduction, it generally provides less favorable dosimetric indices compared to 6FFF in OAG. Mechanicaluncertainty in collimator and couch rotation had an increased effect for OAG compared to CAG; however, thevariations in dose distributions for either treatment technique were minimal.
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