Development and validation of a scatter-corrected CBCT image-guided method for cervical cancer brachytherapy

Ailin Wu; Hehe Cui; Xiao Jiang; Bing Yan; Aidong Wu; Yunqin Liu; Lei Zhu

doi:10.3389/fonc.2022.942016

Development and validation of a scatter-corrected CBCT image-guided method for cervical cancer brachytherapy

Front Oncol. 2022 Oct 27:12:942016. doi: 10.3389/fonc.2022.942016. eCollection 2022.

Authors

Ailin Wu¹, Hehe Cui², Xiao Jiang², Bing Yan¹, Aidong Wu¹, Yunqin Liu¹, Lei Zhu²

Affiliations

¹ Department of Radiation Oncology, The First Affiliated Hospital of University of Science and Technology of China (USTC), Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China.
² Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei, China.

Abstract

Background and purpose: Multiple patient transfers have a nonnegligible impact on the accuracy of dose delivery for cervical cancer brachytherapy. We consider using on-site cone-beam CT (CBCT) to resolve this problem. However, CBCT clinical applications are limited due to inadequate image quality. This paper implements a scatter correction method using planning CT (pCT) prior to obtaining high-quality CBCT images and evaluates the dose calculation accuracy of CBCT-guided brachytherapy for cervical cancer.

Materials and methods: The CBCT of a self-developed female pelvis phantom and five patients was first corrected using empirical uniform scatter correction in the projection domain and further corrected in the image domain. In both phantom and patient studies, the CBCT image quality before and after scatter correction was evaluated with registered pCT (rCT). Model-based dose calculation was performed using the commercial package Acuros^®BV. The dose distributions of rCT-based plans and corrected CBCT-based plans in the phantom and patients were compared using 3D local gamma analysis. A statistical analysis of the differences in dosimetric parameters of five patients was also performed.

Results: In both phantom and patient studies, the HU error of selected ROIs was reduced to less than 15 HU. Using the dose distribution of the rCT-based plan as the baseline, the γ pass rate (2%, 2 mm) of the corrected CBCT-based plan in phantom and patients all exceeded 98% and 93%, respectively, with the threshold dose set to 3, 6, 9, and 12 Gy. The average percentage deviation (APD) of D₉₀ of HRCTV and D_2cc of OARs was less than 1% between rCT-based and corrected CBCT-based plans.

Conclusion: Scatter correction using a pCT prior can effectively improve the CBCT image quality and CBCT-based cervical brachytherapy dose calculation accuracy, indicating promising prospects in both simplified brachytherapy processes and accurate brachytherapy dose delivery.

Keywords: CBCT; brachytherapy; cervical cancer; model-based dose calculation algorithm; scatter correction.