AUTHOR=Hou Chuanke , Yin Hanjing , Gong Guanzhong , Wang Lizhen , Su Ya , Lu Jie , Yin Yong 

TITLE=A novel approach for dose painting radiotherapy of brain metastases guided by mr perfusion images

JOURNAL=Frontiers in Oncology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2022.828312

DOI=10.3389/fonc.2022.828312

ISSN=2234-943X

ABSTRACT=<sec><title>Purpose</title><p>To investigate the feasibility and dosimetric index features of dose painting guided by perfusion heterogeneity for brain metastasis (BMs) patients.</p></sec><sec><title>Methods</title><p>A total of 50 patients with single BMs were selected for this study. CT and MR simulation images were obtained, including contrast-enhanced T1-weighted images (T1WI+C) and cerebral blood flow (CBF) maps from 3D-arterial spin labeling (ASL). The gross tumor volume (GTV) was determined by fusion of CT and T1WI+C images. Hypoperfused subvolumes (GTV<sub>H</sub>) with less than 25% of the maximum CBF value were defined as the dose escalation region. The planning target volume (PTV) and PTV<sub>H</sub> were calculated from GTV and GTV<sub>H</sub> respectively. The PTV<sub>N</sub> was obtained by subtracting PTV<sub>H</sub> from PTV, and conventional dose was given. Three kinds of radiotherapy plans were designed based on the CBF values. Plan 1 was defined as the conventional plan with an arbitrary prescription dose of 60 Gy for PTV. For dose painting, Plan 2 and Plan 3 escalated the prescription dose for PTV<sub>H</sub> to 72 Gy based on Plan 1, but Plan 3 removed the maximum dose constraint. Dosimetric indices were compared among the three plans.</p></sec><sec><title>Results</title><p>The mean GTV volume was 34.5 (8.4-118.0) cm<sup>3</sup>, and mean GTV<sub>H</sub> volume was 17.0 (4.5-58.3) cm<sup>3</sup>, accounting for 49.3% of GTV. Both conventional plan and dose painting plans achieved 98% target coverage. The conformity index of PTV<sub>H</sub> were 0.44 (Plan1), 0.64 and 0.72 (Plan 2 and Plan 3, <italic>P&lt;</italic>0.05). Compared to Plan 1, the D<sub>2%</sub>, D<sub>98%</sub> and D<sub>mean</sub> values of the PTV<sub>H</sub> escalated by 20.50%, 19.32%, and 19.60% in Plan 2 and by 24.88%, 17.22% and 19.22% in Plan 3 respectively (<italic>P&lt;</italic>0.05). In the three plans, the index of achievement value for PTV<sub>H</sub> was between 1.01 and 1.03 (<italic>P&lt;</italic>0.05). The dose increment rates of Plan 2 and Plan 3 for each organs at risk (OARs) was controlled at 2.19% - 5.61% compared with Plan 1. The doses received by OARs did not significantly differ among the three plans (<italic>P &gt;</italic>0.05).</p></sec><sec><title>Conclusions</title><p>BMs are associated with significant heterogeneity, and effective escalation of the dose delivered to target subvolumes can be achieved with dose painting guided by 3D-ASL without extra doses to OARs.</p></sec>