Determination of Deformable Image Registration Algorithms for Accumulating Dose in Carbon-ion Radiotherapy for Pancreatic Cancer

Abstract

Background/aim: This study aimed to determine appropriate deformable image registration (DIR) algorithms for pancreatic cancer patients undergoing carbon ion radiotherapy (CIRT).

Patients and methods: The performance of three types of DIR algorithms, including intensity-based DIR (iDIR), contour-based DIR (cDIR), and hybrid DIR (hDIR) were evaluated using seventy-one CT images from eight pancreatic cancer patients. Both the geometry of the CTV and subsequent dose warping discrepancies were evaluated using the dice similarity coefficient (DSC) and the difference in V95.

Results: cDIR and hDIR had superior performance than iDIR in both DSC and V95 (p<0.0001). iDIR caused accumulated dose to be underestimated by 5% in the median CTV V95 compared to the other methods.

Conclusion: hDIR and cDIR can be utilized to assess the accumulated dose in CIRT for pancreatic cancer. iDIR can be considered when the obtained DSC is greater than 0.89.

Keywords: Deformable image registration (DIR); accuracy evaluation; carbon ion radiotherapy; contour-based DIR; dose accumulation; hybrid DIR; intensity-based DIR; pancreatic cancer.