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Improvement of precision in spatial localization of radio‐opaque markers using the two‐film technique
Author(s) -
Lam Kwok L.,
Ten Haken Randall K.
Publication year - 1991
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596620
Subject(s) - opacity , imaging phantom , medical imaging , optics , radiography , computation , computer science , computer vision , artificial intelligence , physics , algorithm , nuclear physics
Radio‐opaque markers implanted inside or placed on the skin of patients can be used to detect set‐up errors and patient motion. The effects of imaging geometry accuracy for standard radiotherapy equipment on the precision of calculating the positions of radio‐opaque spherical markers using two orthogonal radiographic film projections is investigated. Inaccuracies in the imaging geometry are computed from the manually digitized positions of the marker images on each film pair. Actual marker locations are calculated with a precision limited only by the variance in manual digitization by incorporating those imaging geometry inaccuracies into their computation. Results of a phantom study using a grid of markers in a plastic block indicate that submillimeter precision can be obtained for the spatial coordinates of individual markers, and that the precision is not sensitive to the small inaccuracies in imaging geometry present within the mechanical tolerances of modern radiotherapy treatment machines and simulators.