Abstract
BackgroundThe size-specific dose estimate (SSDE) is a dose-related metrics that incorporates patient size into its calculation. It is usually derived from the volume computed tomography dose index (CTDIvol) by applying a conversion factor determined from manually measured anteroposterior and lateral skin-to-skin patient diameters at the midslice level on computed tomography (CT) localiser images, an awkward, time-consuming, and not highly reproducible technique. The objective of this study was to evaluate the potential for the use of body mass index (BMI) as a size-related metrics alternative to the midslice effective diameter (DE) to obtain a size-specific dose (SSDE) in abdominal CT.MethodsIn this retrospective study of patients who underwent abdominal CT for the investigation of inflammatory bowel disease, the DE was measured on the midslice level on CT-localiser images of each patient. This was correlated with patient BMI and the linear regression equation relating the quantities was calculated. The ratio between the internal and the external abdominal diameters (DRATIO) was also measured to assess correlation with radiation dose. Pearson correlation analysis and linear regression models were used.ResultsThere was good correlation between DE and patient BMI (r = 0.88). An equation allowing calculation of DE from BMI was calculated by linear regression analysis as follows: DE = 0.76 (BMI) + 9.4. A weak correlation between radiation dose and DRATIO was demonstrated (r = 0.45).ConclusionsPatient BMI can be used to accurately estimate DE, obviating the need to measure anteroposterior and lateral diameters in order to calculate a SSDE for abdominal CT.
Highlights
The size-specific dose estimate (SSDE) is a dose-related metrics that incorporates patient size into its calculation
These parameters do not provide a direct measure of the individualised patient radiation dose, a variable that is dependent on patient size
The best correlation was found with DE (0.88), where correlations between mean body mass index (BMI) and mean body diameters were highly significant (p < 0.001)
Summary
The size-specific dose estimate (SSDE) is a dose-related metrics that incorporates patient size into its calculation It is usually derived from the volume computed tomography dose index (CTDIvol) by applying a conversion factor determined from manually measured anteroposterior and lateral skin-to-skin patient diameters at the midslice level on computed tomography (CT) localiser images, an awkward, time-consuming, and not highly reproducible technique. There is a growing interest in this topic, due to Current CT scanner radiation dose output following patient imaging is displayed in the CT dose report in terms of volume CT dose index (CTDIvol) and dose length product (DLP), standardised measurements deduced from homogenous phantoms under normalised conditions [1, 2]. On a practical level this technique can be awkward and time-consuming, and open to interobserver measurement variability
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