Automated size-specific dose estimation for adult non-contrast brain CT: patient-specific analysis using water-equivalent diameter

Abstract

To quantify patient-specific radiation dose for routine adult non-contrast brain CT by integrating waterequivalent diameter (Dw) and size-specific dose estimate (SSDEw), and to compare these metrics with scanner-reported CTDIvol and DLP. A retrospective analysis included 65 adult patients ($\mathbf{3 4}$ men, $\mathbf{3 1}$ women) who underwent non-contrast brain CT on a multidetector CT scanner using the department’s standard adult protocol (140 kVp; automatic tube current modulation enabled). Dw was automatically estimated from the mid-axial slice using Indose CT with bone correction (factor 1.8; threshold $\boldsymbol{+} \mathbf{2 5 0} \mathbf{~ H U}$), and SSDEw was computed from CTDIvol using brain-specific conversion factors (AAPM 293 framework). Effective dose (EDw) was estimated from DLP using an adult brain conversion coefficient. Mean exposure was $149.8 \pm 18.3$ mAs. Mean CTDIvol was $59.93 \pm 7.28 \mathrm{mGy}$ and mean DLP was $1215.2 \pm 194.8 \mathrm{mGy.cm}$. Mean Dw was $15.58 \pm 0.91 \mathrm{~cm}$, yielding a mean SSDEw of $\mathbf{5 6. 7 3} \boldsymbol{\pm} \mathbf{5. 4 3} \mathbf{~ m G y}$. Mean EDw was $\mathbf{1. 7 1 7} \pm$ 0.266 mSv. Automated Dw-based SSDEw provides a more individualized estimate of adult brain CT dose than CTDIvol/DLP alone and can support routine protocol optimization and radioprotection in clinical practice.