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. 2018 Nov 28;2(1):38.
doi: 10.1186/s41747-018-0070-5.

Using body mass index to estimate individualised patient radiation dose in abdominal computed tomography

Siobhan O'Neill  1   2 , Richard G Kavanagh  3   4 , Brian W Carey  2 , Niamh Moore  1 , Michael Maher  1   2   5 , Owen J O'Connor  1   2   5
Affiliations

Using body mass index to estimate individualised patient radiation dose in abdominal computed tomography

Siobhan O'Neill et al. Eur Radiol Exp. .

Abstract

Background: 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. 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.

Methods: In 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.

Results: There 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).

Conclusions: Patient 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.

Keywords: Abdomen; Body mass index; Radiation dosage; Tomography (x-ray, computed).

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Conflict of interest statement

Ethics approval and consent to participate

Approval for this study was granted by the Clinical Research Ethics Committee of the Cork Teaching Hospitals, Lancaster Hall, 6 Little Hanover Street, Cork, Ireland. Informed consent was obtained from each patient.

Consent for publication

The consent for publication is included in the informed consent.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Measurement of lateral (DLAT) (a) anteroposterior (DAP) (b) skin-to-skin patient diameters at the midslice level on CT-localiser images. Measurement of the inner lateral and anteroposterior diameters on the axial midslice CT image excluding the subcutaneous adipose tissue (c) to allow calculation of the effect inner diameter (DIN) and the effective diameter ratio (DRATIO)
Fig. 2
Fig. 2
Graphs show the relationship of body mass index (BMI) to anteroposterior diameter (DAP) (a), lateral diameter (DLAT) (b), effective diameter (DE) (c) and effective diameter ratio (DRATIO) (d). Correlation coefficients were 0.83, 0.84, 0.88, and 0.48, respectively (p < 0.001)
Fig. 3
Fig. 3
Scatterplots show: volume-computed tomography dose index (CTDIvol) for body mass index (BMI) (a) and effective diameter (b) with correlation r values of 0.85 and 0.9, respectively; dose length product (DLP) for BMI (c) and effective diameter (d) with r correlation values of 0.84 and 0.89, respectively; size-specific dose estimate (SSDE) for BMI (e) and effective diameter (f) with r correlation values of 0.87 and 0.88, respectively; effective dose for BMI (g) and effective diameter (h) with r correlation values of 0.84 and 0.87, respectively
Fig. 4
Fig. 4
Scatterplot of body mass index (BMI) as a function of effective diameter. Linear regression trend line equation: DE = 0.76(BMI) + 9.4
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