Open AccessComparison of methods to estimate water‐equivalent diameter for calculation of patient dose
Author(s) -
Daudelin Andrew,
Medich David,
Andrabi Syed Yasir,
Martel Chris
Publication year - 2018
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12383
Subject(s) - attenuation , mathematics , water equivalent , nuclear medicine , margin (machine learning) , correction for attenuation , geometry , computer science , optics , physics , medicine , machine learning , meteorology , snow
Modern CT systems seek to evaluate patient‐specific dose by converting the CT dose index generated during a procedure to a size‐specific dose estimate using conversion factors that are related to patient attenuation properties. The most accurate way to measure patient attenuation is to evaluate a full‐field‐of‐view reconstruction of the whole scan length and calculating the true water‐equivalent diameter ( D w ) using CT numbers; however, due to time constraints, less accurate methods to estimate D w using patient geometry measurements are used more widely. In this study we compared the accuracy of D w values calculated from three different methods across 35 sample scans and compared them to the true D w . These three estimation methods were: measurement of patient lateral dimension from a pre‐scan localizer radiograph; measurement of the sum of anteroposterior and lateral dimensions from a reconstructed central slice; and using CT numbers from a central slice only. Using the localizer geometry method, 22 out of 35 (62%) samples estimated D w within 20% of the true value. The middle slice attenuation and geometry methods gave estimations within the 20% margin for all 35 samples.