Table 4 Examples of dose estimation on abdominal computed tomography (CT)

Monte Carlo dose estimation with patient-specific anatomical models [9]

Full-body computer model created based on the patient’s clinical CT data. Large organs individually segmented and modelled. Other organs were created by transforming an existing adult male or female full-body computer model to match the framework defined by the segmented organs, referencing the organ volume and anthropometry data in ICRP Publication 89. A Monte Carlo program (General Electric Lightspeed VCT-XTe, GE Healthcare, GE Medical Systems, Waukesha, WI, USA) was used to estimate patient-specific organ dose, from which effective dose and risks of cancer incidence were derived. Study suggests the construction of a large library of patient-specific computer models could estimate dose for any patient prior to or after a CT examination

Automated measurement of effective diameter [10]

Algorithm for estimating body-size diameter on axial CT slice implemented in Python and C#. Number of pixels whose Hounsfield unit exceeding a set threshold multiplied by the area of a single pixel to give an estimate of the area of the patient cross-section. Effective diameter computed as diameter of the circle whose area is the same as that of the cross-section. Correlation between the manual and automated measurements of effective diameter was very high

Patient size modelled as a water-equivalent diameter (D_W) [11]

Water-equivalent diameter (D_W), automatically extracted from axial CT images and used to model patient size and subsequently to calculate size-specific dose estimates. The extracted D_W values correlate well with effective diameter (R² of 0.90 for abdomen and pelvis)

Dose estimation through directly using thermoluminescent dosemeters (TLDs) [12]

Thermoluminescent dosemeters (TLDs) and a Rando Alderson phantom used. Computer-simulated dose estimation based on National Radiation Protection Board Monte Carlo simulations. Directly measured dose 18% higher than computer-simulated dosimetry, suggesting underestimation by computer-simulation techniques compared with TLD measurements

Topogram-based body size indices for CT dose consideration and scan protocol optimisation [13]

Linear regression of four topographical indices for estimation of D_w (i) average diameter; (ii) girth (cross-section modelled as ellipse); (iii) topogram projection area; (iv) improved topogram projection area (corrected for patient miscentering and water attenuation coefficient)

Correlating body weight with diameter for radiation dose estimates [6]

Anteroposterior and lateral diameters were measured manually and through automated software. Effective diameter subsequently calculated. Overall body weight had a strong correlation with diameter