Scout-Dose-TCM: direct and prospective scout-based estimation of personalized organ and effective doses from tube current modulated CT exams

Abstract

Objective.This study proposes Scout-Dose-TCM for direct, prospective estimation of organ-level and effective doses under tube current modulation (TCM) and compares its performance with two established methods.Approach.Contrast-enhanced chest-abdomen-pelvis CT exams from 130 adults (120 kVp, TCM) were analyzed. Reference organ doses for six organs (lungs, kidneys, liver, pancreas, bladder, spleen) were calculated using Monte Carlo (MC)-GPU and TotalSegmentator. These data trained Scout-Dose-TCM, a deep-learning model that predicts organ-level doses corresponding to discrete cosine transform (DCT) basis functions, enabling real-time estimation for any TCM profile. The model includes a feature-learning module that extracts contextual information from lateral and frontal scouts and scan range, and a dose-learning module that outputs DCT-based dose estimates. The loss function incorporated the DCT formulation, ensuring accurate predictions across variable TCM patterns. For comparison, dose estimation was performed following AAPM Task Group 204 (Global CTDI_vol) and its TCM-adapted and organ-specific version (Organ CTDI_vol). The three evaluated methods were extended to estimate effective dose and compared against the approach in AAPM Report 96, which applies a fixed dose-length product-to-effective-dose conversion factor. Five-fold cross-validation assessed generalizability via mean absolute percentage dose errors andR²correlations with MC benchmarks.Main Results.Mean organ-level absolute percentage errors were 13% (Global CTDI_vol), 9% (Organ CTDI_vol), and 7% (Scout-Dose-TCM). The largest discrepancies occurred for the bladder (15%, 13%, and 9%). Scout-Dose-TCM significantly reduced organ-level dose errors versus Global CTDI_vol(p< 1 × 10^-7) and improved predictions for liver, bladder, and pancreas versus Organ CTDI_vol(p⩽ 0.005). It also achieved higher R²values and lower effective-dose error (3.01%) than Global (3.87%) and Organ (4.16%) CTDI_vol, and the AAPM Task Group 96 method (31%).Significance.Scout-Dose-TCM outperformed Global CTDI_voland was comparable to or better than Organ CTDI_volfor organ and effective dose estimation without requiring segmentations at inference, demonstrating its clinical potential for prospective dose estimation in CT.

Keywords: Monte Carlo dose estimation; organ dose; radiation dose; tube current modulation.