| Wang Haiyang,Dai Xiangkun,Niu Baolong,et al.Effect of cavity structure delineation errors on target dosimetry in Unity MR-Linac radiotherapy[J].Chinese Journal of Radiological Medicine and Protection,2026,46(5):522-527 |
| Effect of cavity structure delineation errors on target dosimetry in Unity MR-Linac radiotherapy |
| Received:November 26, 2024 |
| DOI：10.3760/cma.j.cn112271-20241126-00456 |
| KeyWords:MR-Linac Electron return effect Cavity Radiotherapy dosimetry |
| FundProject:国家重点研发计划(2022YFC2409502,2022YFC2409503) |
| Author Name | Affiliation | E-mail | | Wang Haiyang | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Dai Xiangkun | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Niu Baolong | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Rao Le | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Wang Hongchi | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Yu Faqiang | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Chen Gaoxiang | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Qu Baolin | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | | | Xie Chuanbin | Department of Radiotherapy, First Medical Center of PLA General Hospital, Beijing 100853, China | xiechuanbin2003@163.com |
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| Abstract:: |
| Objective To investigate the impact of MRgRT cavity delineation errors on tumor target dose in patients, in order to provide a reference for clinical applications. Methods A virtual target and adjacent cavity were modeled in a phantom. The cavity boundary adjacent to the target was expanded outward by 1, 2, 4, 6, and 8 mm to simulate delineation errors. Single-field plans were designed with beam angles of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°, while multi-field plans employed equally spaced beams (uniform weighting, including two opposed fields and 3-8 evenly distributed fields), totaling 28 plans. Dose calculations were performed based on identical planning parameters. Additionally, 15 online adaptive treatment fractions from two esophageal cancer patients and one cardiac sarcoma patient were selected, and the same delineation error simulations followed by dose recalculation were applied to the lung adjacent to the target. Dosimetric parameters of the target were analyzed. Results In the single-field phantom study, 65% of the dose variations caused by delineation errors exceeded 3% (5.63% ± 0.67%). Specifically, the target maximum dose (Dmax) increased with larger delineation errors for beam angles of 0°, 45°, 90°, 135°, 180°, and 225°. In the two-opposed-field scenario, only initial angles of 0°, 45°, and 135° exhibited dose variations ≥3%. As the number of beams increased, target dose variations stabilized. In patient simulations,pGTV_Dmaxsignificantly increased after introducing delineation errors, peaking at 1.31% for 4 mm (t=-2.88, P<0.05). Similarly,PTV_Dmax showed the largest difference (2.22%) at 6 mm (t=-6.66, P<0.05). With increasing delineation errors, target Dmax and man dose(Dmean) exhibited an upward trend, whilePTV_D95 demonstrated a downward trend. Conclusions In MR-guided radiotherapy, online delineation errors of cavities adjacent to the target can affect target dose distribution, with the Dmax being the most significantly impacted. To mitigate dose calculation uncertainties in clinical practice, maintaining high cavity boundary delineation accuracy is essential, and increasing the number of beams may help reduce such uncertainties. |
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