How inaccurate is weight as a metric for patient size? Comparing patient weight to effective diameter for size-specific dose estimation

Tessa S. Cook; Seetharam C. Chadalavada; William W. Boonn

doi:10.1117/12.2006132

29 March 2013 How inaccurate is weight as a metric for patient size? Comparing patient weight to effective diameter for size-specific dose estimation

Tessa S. Cook, Seetharam C. Chadalavada, William W. Boonn

Author Affiliations +

Proceedings Volume 8674, Medical Imaging 2013: Advanced PACS-based Imaging Informatics and Therapeutic Applications; 867408 (2013) https://doi.org/10.1117/12.2006132
Event: SPIE Medical Imaging, 2013, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

One of the biggest challenges in dose monitoring is customization of CT dose estimates to the patient. Patient size remains a highly significant variable. One metric that has previously been used for patient size is patient weight, though this is often criticized as inaccurate. In this work, we compare patients’ weight to their effective diameters obtained from a CT scan of the chest or the abdomen. CT exams of the chest (N=163) and abdomen/pelvis (N=168) performed on adult patients in July 2012 were randomly selected for analysis. The effective diameter of the patient for each exam was determined using the central slice of the scan region for each exam using eXposure™ (Radimetrics, Inc., Toronto, Canada). In some cases, the same patient had both a chest and abdominopelvic CT, so effective diameters from both regions were analyzed. In this small sample size, there appears to be a linear relationship between patient weight and effective diameter when measured in the mid-chest and mid-abdomen of adult patients. However, for each weight, patient effective diameter can vary by 5 cm from the regression line in both the chest and the abdomen. A 5-cm difference corresponds to a difference of approximately 0.2 in the chest and 0.3 in the abdomen/pelvis for the correction factors recommended for size-specific dose estimation by the AAPM. This preliminary data suggests that weight-based CT protocoling may in fact be appropriate for some adults. However, more work is needed to identify those patients in whom weight-based protocoling is not appropriate.

Citation Download Citation

Tessa S. Cook, Seetharam C. Chadalavada, and William W. Boonn "How inaccurate is weight as a metric for patient size? Comparing patient weight to effective diameter for size-specific dose estimation", Proc. SPIE 8674, Medical Imaging 2013: Advanced PACS-based Imaging Informatics and Therapeutic Applications, 867408 (29 March 2013); https://doi.org/10.1117/12.2006132

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