An important patient-size related dose metric in CT is the Size Specific Dose Index (SSDE). This index, developed by AAPM [1, 2] is calculated from the machine/protocol CTDIvol (including phantom type) and a patient-size related quantity (PA/LAT diameter via scout scan or the Water Equivalent Diameter, WED, via automatic patient contouring and use of equation 4b found on page 8 of AAPM220). AAPM recommends that the SSDE is calculated per slice, with the final reportable SSDE being the mean SSDE over all slices with consideration...

Axial CT images from two publicly available abdomino-pelvic datasets [6-10] containing image CTDIvol and phantom type information (111 studies, 4 different imaging systems) were analysed with both software packages to obtain SSDE values. CTContour processes images on a local machine, accepts the full collection of studies directly, and visualizes the patient contour (figure 1) which can be used as a visual check of contouring accuracy (and hence accuracy of SSDE); it also flags and permits the omission of truncated images. In the case of AutoWED,...

Visual assessment of the patient contours as provided by CTContour indicated that the determination of WED and hence SSDE was accurate (figures 1 and 2). For part 1, with all slices included for CTContour, very good agreement was found in SSDE values as calculated by CTContour and AutoWED (figure 3, top-left and top-right) with mean difference being only +0.06mGy (0.3%), significant at p<0.001 using a paired t-test, with the AutoWED mean value being consistently the lower estimate with the difference in SSDE between the two...

When considering all slices, including those containing truncated patient anatomy, there was good agreement between the two software tools and both tools are suitable for the validation of commercial dose monitoring systems. However, when omitting truncated slices, the discrepancy was higher. The effect of omission of truncated slices was investigated in this work, indicating that omission of truncated slices results in a lower mean SSDE. CTContour has the technical advantage of detection of truncated images and contour visualization (important for checking the accuracy of contouring...

E. Pace: Nothing to disclose C. J. Caruana: Nothing to disclose K. Cortis: Nothing to disclose M. D'Anastasi: Nothing to disclose G. Valentino: Nothing to disclose

American Association of Physicists in Medicine. Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT Examinations. Report 204. 2001. American Association of Physicists in Medicine. Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT. Report 220. vol. 2014. 2014. Pace E, Caruana CJ, Bosmans H, Cortis K, D’Anastasi M, Valentino G. CTContour: An open-source Python pipeline for automatic contouring and calculation of mean SSDE along the abdomino-pelvic region for CT images; validation on fifteen systems. Phys Medica...