Optimization of collimator angle combined island blocking with parked gap achieves superior normal tissue sparing in SBRT planning of multiple liver lesions

Maidina Abuduxiku; Xiaoqiang Chen; Shu Zhang; Jiangping Yang; Wenjun Liao; Jianghong Xiao

doi:10.1002/acm2.14267

Optimization of collimator angle combined island blocking with parked gap achieves superior normal tissue sparing in SBRT planning of multiple liver lesions

J Appl Clin Med Phys. 2024 Jan 23:e14267. doi: 10.1002/acm2.14267. Online ahead of print.

Authors

Maidina Abuduxiku¹, Xiaoqiang Chen¹, Shu Zhang^{2

3}, Jiangping Yang², Wenjun Liao⁴, Jianghong Xiao¹

Affiliations

¹ Radiotherapy Physics & Technology Center, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
² Head and Neck Oncology Department, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
³ Department of Radiation Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
⁴ Department of Radiation Oncology, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China.

PMID: 38259201
DOI: 10.1002/acm2.14267

Abstract

Purpose: To propose an efficient collimator angle optimization method by combining island blocking (IB) and parked gap (PG) problem to reduce the radiotherapy dose for normal tissue. The reduction will be done with single-isocenter multi-lesion volumetric modulated arc therapy (VMAT) for the stereotactic body radiation therapy (SBRT) of liver cancer.

Methods: A novel collimator angle optimization algorithm was developed based on the two-dimensional projection of targets on a beam's eye view (BEV) plane as a function of gantry and collimator angle. This optimization algorithm minimized the sum of the combined IB and PG (IB & PG) areas from all gantry angles for each arc. For comparison, two SBRT plans were respectively generated for each of the 20 retrospective liver cancer cases with multiple lesions. One plan was optimized using the IB & PG algorithm, and the other plan was optimized with a previously reported optimization algorithm that only considered the IB area. Plans were then evaluated and compared using typical dosimetric metrics.

Results: With the comparable target coverage, IB & PG plans had significantly lower D_500cc , D_700cc , mean dose (D_mean ), and V₁₅ of normal liver tissues when compared to IB plans. The median percent reductions were 3.32% to 5.36%. The D_1cc , D_5cc , and D_mean for duodenum and small intestine in IB & PG plans were significantly reduced in a range from 7.60% up to 16.03%. Similarly, the median integral dose was reduced by 3.73%. Furthermore, the percentage of normal liver D_mean sparing when IB & PG plans compared to IB plans, was found to be positively correlated (ρ = 0.669, P = 0.001) with the inter-target distance.

Conclusion: The proposed IB & PG algorithm has been demonstrated to outperform the IB algorithm in almost all normal tissue sparing, and the magnitude of liver sparing was positively correlated with inter-target distance.

Keywords: collimator angle optimization; island blocking; multiple lesions; parked gap; stereotactic body radiation therapy.

Abstract

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