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

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.

Diagnostic Reference Levels based on clinical indications in computed tomography: a literature review

“…For tumour, the DLP values ranged from 870 mGy.cm [ 15 ] to 950 mGy.cm [ 35 ]. For oncologic follow-up, the DLP values ranged from 605 mGy.cm [ 36 ] to 970 mGy.cm [ 34 ]. One publication presents DRL ci for abdominal CT, both for males and females [ 16 ], demonstrating however similar values.…”

“…The huge variations in the reported CT dose descriptors values for almost all the clinical indications addressed above are likely to be explained by differences in protocols (exposure parameters and scan length), type and age of scanner, number of acquisition series and, in the specific case of CCTA, by the option of performing either prospective or retrospective acquisitions. The same variations in radiation doses for CT across patients is described in the literature, and the reasons are primarily related on how CT scanners are used [ 34 ], the differences in patient’s size (weight and height) [ 36 ] and to the level of image quality required to answer the clinical question [ 35 ]. Although the DRLs are defined for standard patients [ 4 ], taking into consideration that the weight and height of patients are also a determining factor for dose increase, categorising patients by body mass index should be considered in the near future [ 36 ].…”

Radiation dose tracking in computed tomography: Red alerts and feedback. Implementing a radiation dose alert system in CT

“…BMI data can also be used to approximate size specific dose estimates which take patient size into consideration when describing patient dose. 22 Quantitative measures of size would provide better data for the determination of the causes of red alerts. Also, due to difficulty with data transmission from the CT scanners to DoseWatch in Period 1, dose data of many brain and abdominopelvic CT examinations could not be retrieved for analysis.…”

A prospective, matched comparison of ultra‐low and standard‐dose computed tomography for assessment of renal colic

“…Informed consent to proceed with both SDCT and ULDCT was obtained prior to proceeding with imaging. Body mass index (BMI) was not prospectively collected and not retrospectively available, so BMI was estimated using the method described by O'Neill et al [9], who reported good correlation between BMI and imaging measurements (r = 0.88).…”