Uncertainties in prostate localization: A study in a laboratory setting

Purpose: The main goal of this study is to minimize systematic errors by utilizing linear regression to determine the position of gold seed markers that were implanted in a wax phantom, using EPID images in a controlled laboratory setting.
Materials and Methods: Pairs of orthogonal portal images were generated and carefully examined, while the phantom was subjected to a known displacement in either the lateral or superior-inferior direction. The measured seed displacement was then compared with the average seed displacement determined from the orthogonal EPID images. The accuracy of the inferred seed positions from the portal images was evaluated using linear regression, concordance correlation coefficient (CCC), intraclass correlation coefficients (ICC), and Bland-Altman plots.
Results: The average displacement errors were found to be 3.2 mm, 2.6 mm, 2.4 mm, and 6.7 mm in the lateral left, lateral right, cranio-caudal (inward), and cranio-caudal (outward) directions, respectively.
Conclusion: The results suggest that utilizing linear regression can significantly reduce the systematic errors described in this study and are consistent with previously published findings on setup errors.