Open AccessAssessment of biological dosimetric margin for stereotactic body radiation therapy
Author(s) -
Kawahara Daisuke,
Saito Akito,
Ozawa Shuichi,
Shiinoki Takehiro,
Kimura Tomoki,
Tsubouchi Kento,
Nagata Yasushi
Publication year - 2020
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12843
Subject(s) - isocenter , nuclear medicine , dosimetry , margin (machine learning) , radiation treatment planning , radiation therapy , radiosurgery , relative biological effectiveness , imaging phantom , medicine , computer science , radiation , physics , radiology , optics , machine learning
Purpose To develop a novel biological dosimetric margin (BDM) and to create a biological conversion factor (BCF) that compensates for the difference between physical dosimetric margin (PDM) and BDM, which provides a novel scheme of a direct estimation of the BDM from the physical dose (PD) distribution. Methods The offset to isocenter was applied in 1‐mm steps along left‐right (LR), anterior‐posterior (AP), and cranio‐caudal (CC) directions for 10 treatment plans of lung stereotactic body radiation therapy (SBRT) with a prescribed dose of 48 Gy. These plans were recalculated to biological equivalent dose (BED) by the linear‐quadratic model for the dose per fraction (DPF) of d = 3–20 Gy/fr andα / β = 3 - 10 . BDM and PDM were defined so that the region that satisfied that the dose covering 95% (or 98%) of the clinical target volume was greater than or equal to the 90% of the prescribed PD and BED, respectively. An empirical formula of the BCF was created as a function of the DPF. Results There was no significant difference between LR and AP directions for neither the PDM nor BDM. On the other hand, BDM and PDM in the CC direction were significantly larger than in the other directions. BCFs of D 95% and D 98% were derived for the transverse (LR and AP) and longitudinal (CC) directions. Conclusions A novel scheme to directly estimate the BDM using the BCF was developed. This technique is expected to enable the BED‐based SBRT treatment planning using PD‐based treatment planning systems.