Accuracy in catheter reconstruction in computed tomography planning of high dose rate prostate brachytherapy

In high dose rate prostate brachytherapy, inadequate reconstruction of catheter geometry in treatment planning may result in erroneous dose delivery. Catheters may be digitized with: (1) Parallel reconstruction: digitized at only one point and assumed parallel and horizontal: (2) Straight reconstruction: digitized at both ends and assumed straight while at an angle: (3) Slice-by-slice reconstruction: digitized on all slices to obtain exact geometry. Our results show that individual catheters are often not parallel to each other, but fairly straight. Parallel reconstruction is the least accurate for dosimetric planning, while slice-by-slice reconstruction is time-consuming. Straight (two-point) reconstruction represents a balance between accuracy and efficiency.