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Clinical evaluation of the aperture shape controller in volumetric modulated arc therapy: Effects on MLC and jaw
Tatsuya Kamima1, Yosuke Sato1, Yuki Murakami1
1Radiation Oncology Department, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Koto-ku, Tokyo, Japan.
Background:
This study comprehensively evaluated the impact of aperture shape controller (ASC) on volumetric modulated arc therapy (VMAT) clinical treatment planning.
Methods:
A total of 248 VMAT plans for head and neck, prostate, post mastectomy breast, gastric MALT lymphoma, rectum, and Lung SBRT for treatments performed between 2018 and 2023 were retrospectively enrolled. These treatment plans were divided into two groups: before (ASC-OFF group) and after (ASC-ON group) the clinical implementation of ASC. The performance of ASC in terms of plan complexity was evaluated by between group comparisons of the multi-leaf collimator (MLC) modulation complexity score (MCSv) and jaw tracking complexity score (JTCS), plan quality using dosimetric parameters, and plan deliverability.
Results:
The overall MCSv and JTCS of the ASC-OFF and ASC-ON groups were 0.318 and 0.369 (p < 0.001) and 2.85 cm and 2.98 cm (p = 0.10), respectively. In the ASC-ON group, the complexity of MLC motions was significantly lower and the complexity of jaw motions higher. In addition, most dosimetric parameters were comparable between groups or better in the ASC-ON group. There was no significant difference in the gamma passing rate of 3%/2 mm between the two groups, although at tighter criteria, the gamma passing rate was higher in the ASC-ON group.
Conclusions:
The use of ASC reduced the complexity of MLC motions without compromising the plan quality. Furthermore, this study found that ASC allows jaw tracking to be more effective.
