Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) · 2026
Refining anisotropic PTV margins for gastric MALT lymphoma radiotherapy with breath-hold: fan beam CT-guided validation and adaptation.
СтатьяВалидационное исследованиеНазвание и аннотация: Перевод в очереди
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Li Wenxiang, Yang Qiangxing, Wang Lihong, Liu Junqing, He Yu, Yan Senxiang, Lu Zhongjie, Zhao Feng
Аннотация
INTRODUCTION: To validate a fan-beam CT (FBCT)-guided Library of Plans (LoP) strategy for gastric MALT lymphoma treated under end-expiration breath-hold (EEBH), incorporating substructure-specific anisotropic margins to balance target coverage and organ-at-risk (OAR) sparing.
METHODS: Two distinct cohorts were evaluated: a historical CBCT-IGRT cohort (n=28, 142 fractions) to establish baseline rigid setup deviations, and a prospective FBCT-IGRT cohort (n=33, 330 fractions) for dose recalculation, deformation analysis, and validation of the LoP strategy. Rigid setup deviations were quantified, and non-rigid deformation vectors were decomposed into substructures (fundus, corpus, antrum) to generate anisotropic margins. A patient-specific LoP was constructed comprising three hierarchical plans (Small, Medium, Large) corresponding to the 50th, 80th, and 95th deformation percentiles. A retrospective dosimetric comparison was performed between the LoP strategy and a conventional single-plan strategy (20 mm isotropic margin).
RESULTS: FBCT-derived rigid margins were 8, 4, and 7 mm (SI/LR/AP), with significant AP deviations observed (p = 0.017). Deformation analysis confirmed a proximal-to-distal gradient (Antrum > Fundus), with 95th-percentile antral expansions peaking at ∼8 mm. In simulation, Plan Small was predominantly selected (59.7%). Dosimetrically, the LoP strategy maintained target coverage equivalent to the single-plan approach (p = 0.687) while reducing mean heart dose by ∼50% (p = 0.0005) and significantly lowering liver and kidney doses.
CONCLUSIONS: The FBCT-guided LoP strategy, utilizing anisotropic substructure-specific margins, effectively addresses regional deformation heterogeneity. This approach maintains robust target coverage while significantly reducing OAR exposure compared to conventional uniform margins, offering a precise and efficient radiotherapy strategy for gastric MALT lymphoma.
METHODS: Two distinct cohorts were evaluated: a historical CBCT-IGRT cohort (n=28, 142 fractions) to establish baseline rigid setup deviations, and a prospective FBCT-IGRT cohort (n=33, 330 fractions) for dose recalculation, deformation analysis, and validation of the LoP strategy. Rigid setup deviations were quantified, and non-rigid deformation vectors were decomposed into substructures (fundus, corpus, antrum) to generate anisotropic margins. A patient-specific LoP was constructed comprising three hierarchical plans (Small, Medium, Large) corresponding to the 50th, 80th, and 95th deformation percentiles. A retrospective dosimetric comparison was performed between the LoP strategy and a conventional single-plan strategy (20 mm isotropic margin).
RESULTS: FBCT-derived rigid margins were 8, 4, and 7 mm (SI/LR/AP), with significant AP deviations observed (p = 0.017). Deformation analysis confirmed a proximal-to-distal gradient (Antrum > Fundus), with 95th-percentile antral expansions peaking at ∼8 mm. In simulation, Plan Small was predominantly selected (59.7%). Dosimetrically, the LoP strategy maintained target coverage equivalent to the single-plan approach (p = 0.687) while reducing mean heart dose by ∼50% (p = 0.0005) and significantly lowering liver and kidney doses.
CONCLUSIONS: The FBCT-guided LoP strategy, utilizing anisotropic substructure-specific margins, effectively addresses regional deformation heterogeneity. This approach maintains robust target coverage while significantly reducing OAR exposure compared to conventional uniform margins, offering a precise and efficient radiotherapy strategy for gastric MALT lymphoma.