An improved method for automated calculation of the water‐equivalent diameter for estimating size‐specific dose in CT

Abstract

The aim of this study is to propose an algorithm for the automated calculation of water-equivalent diameter (D w ) and size-specific dose estimation (SSDE) from clinical computed tomography (CT) images containing one or more substantial body part.Methods: All CT datasets were retrospectively acquired by the Toshiba Aquilion 128 CT scanner. The proposed algorithm consisted of a contouring stage for the D w calculation, carried out by taking the six largest objects in the cross-sectional image of the patient's body, followed by the removal of the CT table depending on the center position (y-axis) of each object. Validation of the proposed algorithm used images of patients who had undergone chest examination with both arms raised up, one arm placed down and both arms placed down, images of the pelvic region consisting of one substantial object, and images of the lower extremities consisting of two separated areas. Results:The proposed algorithm gave the same results for D w and SSDE as the previous algorithm when images consisted of one substantial body part. However, when images consisted of more than one substantial body part, the new algorithm was able to detect all parts of the patient within the image. The D w values from the proposed algorithm were 9.5%, 15.4%, and 39.6% greater than the previous algorithm for the chest region with one arm placed down, both arms placed down, and images with two legs, respectively. The SSDE values from the proposed algorithm were 8.2%, 11.2%, and 20.6% lower than the previous algorithm for the same images, respectively. Conclusions:We have presented an improved algorithm for automated calculation of D w and SSDE. The proposed algorithm is more general and gives accurate results for both D w and SSDE whether the CT images contain one or more than one substantial body part.How to cite this article: Anam C, Mahdani FR, Dewi WK, et al. An improved method for automated calculation of the water-equivalent diameter for estimating size-specific dose in CT.

An in-house step-wedge phantom for the calibration of pixel values in CT localizer radiographs for water-equivalent diameter measurement

“…The automatic measurement of Dw based on axial CT images was conducted using IndoseCT 20b software. 11 The first stage was to convert the axial CT image in the DICOM files into Hounsfield units (HU) using Equation 2:…”

“…7,8 However, both of these metrics have limitations 9 because they only provide information about the output dose from the CT and do not fully estimate the radiation dose to the patient, which strongly depends on the patient size. 10,11 In 2011, the size-specific dose estimate (SSDE) was introduced to estimate patient dose by taking into account the individual patient's body size, thus enabling a more accurate estimation of the dose absorbed by the patient. 12 The calculation of SSDE was based on the effective diameter (D eff ).…”

Deep Learning-based calculation of patient size and attenuation surrogates from localizer Image: Toward personalized chest CT protocol optimization

“…3D CT images provide a more robust and accurate measurement of DW and D eff . However, the input images could be affected by truncation artifacts owing to the limited reconstruction field-of-view (FOV), which is common in thoracic, cardiac, and musculoskeletal CT examinations [10][11][12]. Besides, it requires more computational and storage resources and is not available before spiral acquisition.…”

Can the Size-Specific Dose Estimate Be Derived From the Body Mass Index? A Feasibility Study

“…However, the calculation of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\mathrm{SSDE}$\end{document} may fail if the patient’s body contour cannot be clearly identified in the overview images or is outside of the overview images and the diameter in the center slice is therefore incorrectly determined or not determined at all. Although methods have been developed which recognize these problems and improve the calculations, they have not yet been implemented in the scanners currently in use ( 10 ) . In addition, the calculation of the diameter and thus the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\mathrm{SSDE}$\end{document} from all CT slices is time-consuming and only possible afterward ( 11 ) .…”