Going from 3D/3D to 2D/3D registration for noncoplanar setup verification in intracranial single-isocenter multiple-target hypofractionated stereotactic radiotherapy: comparison between kilo-voltage/mega-voltage image pairs and noncoplanar cone-beam computed tomography

Jialu Lai; Shoupeng Liu; Jia Liu; Maoyue Fu; Maoqiong Jiang; An Li; Bin Li; Xinke Li; Xiaqin Cheng; Lin Zhou

doi:10.21037/qims-23-463

Going from 3D/3D to 2D/3D registration for noncoplanar setup verification in intracranial single-isocenter multiple-target hypofractionated stereotactic radiotherapy: comparison between kilo-voltage/mega-voltage image pairs and noncoplanar cone-beam computed tomography

Quant Imaging Med Surg. 2023 Dec 1;13(12):8094-8106. doi: 10.21037/qims-23-463. Epub 2023 Sep 28.

Authors

Jialu Lai¹, Shoupeng Liu¹, Jia Liu², Maoyue Fu³, Maoqiong Jiang³, An Li¹, Bin Li¹, Xinke Li⁴, Xiaqin Cheng⁵, Lin Zhou⁵

Affiliations

¹ Radiotherapy Physics & Technology Center, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
² Department of Oncology, Chengdu First People's Hospital, Chengdu, China.
³ Department of Oncology, Yibin Second People's Hospital, Yibin, China.
⁴ West China Clinical Medical College of Sichuan University, Chengdu, China.
⁵ Thoracic Oncology Ward, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.

Abstract

Background: Single-isocenter (SI) noncoplanar volumetric modulated arc therapy (NC-VMAT) has been widely used in stereotactic radiosurgery (SRS) or hypofractionated stereotactic radiotherapy (HSRT) for multiple brain metastases (BMs). However, it is critical to verify patient positioning at a noncoplanar couch angle. This study aimed to compare the noncoplanar setup discrepancies between kilo-voltage/mega-voltage image (kV/MV) orthogonal image pairs with a 2-dimensional/3-dimensional (2D/3D) matching mode and noncoplanar cone-beam computed tomography (NC-CBCT) with a 3D/3D matching mode in SI NC-VMAT HSRT for multiple BMs.

Methods: Twenty patients with multiple BMs [2-5] who underwent SI NC-VMAT HSRT were enrolled in this study. Prior to each noncoplanar field delivery, both kV/MV orthogonal image pairs and NC-CBCT were used to determine setup errors. The setup error values reported by NC-CBCT were defined as the gold standard and compared to those reported by kV/MV orthogonal image pairs. The Bland-Altman analysis method was utilized to assess the agreement of the two positioning modalities.

Results: In total, 104 kV/MV image pairs and NC-CBCT scans were acquired. The mean setup error differences (SEDs; absolute values) between the two positioning systems were 0.17 mm, 0.21 mm, 0.16 mm, 0.22°, 0.18°, and 0.17° in the vertical, longitudinal, lateral, yaw, pitch, and roll directions, respectively. The maximum SEDs regarding translation and rotation occurred in the longitudinal and yaw directions at 0.60 mm and 0.8°, respectively. Bland-Altman analysis showed excellent agreement between the two positioning modalities, and the 95% limits of agreement (LOAs) never exceeded 0.6 mm and 0.6° in the translational and rotational directions, respectively. Only 4.80% of SEDs exceeded the tolerance of 0.5 mm/0.5°.

Conclusions: Orthogonal kV/MV image pairs with 2D/3D matching mode could provide comparable accuracy for noncoplanar positioning as NC-CBCT with 3D/3D matching mode.

Keywords: 2-dimensional/3-dimensional matching mode (2D/3D matching mode); 3-dimensional/3-dimensional matching mode (3D/3D matching mode); Noncoplanar setup discrepancies; kilo-voltage/mega-voltage image orthogonal image pairs (kV/MV orthogonal image pairs); noncoplanar cone-beam computed tomography (noncoplanar CBCT).