Patient-specific radiation risk-based tube current modulation for diagnostic CT

Area of Science:

• Medical Imaging
• Radiological Physics
• Radiation Dosimetry

Background:

• Modern CT scanners utilize automatic exposure control (AEC), including tube current modulation (TCM), to balance patient dose and image quality.
• Conventional TCM methods, termed mAsTCM, minimize the tube current-time product (mAs) but do not account for varying organ radiosensitivity.

Purpose of the Study:

• To introduce and evaluate a novel risk-based TCM (riskTCM) framework designed to minimize patient radiation risk by considering individual organ radiation sensitivity.
• To compare the dose reduction efficacy of riskTCM against conventional mAsTCM and a noTCM (constant tube current) approach.

Main Methods:

• The riskTCM framework utilizes real-time CT reconstruction, organ segmentation, and dose distribution estimation, potentially leveraging machine learning.
• It determines a tube current curve that minimizes a patient risk measure (e.g., effective dose) while maintaining image quality.
• riskTCM was retrospectively applied to 20 patients across various anatomical regions and tube voltages (70–150 kV), with effective dose reduction evaluated against mAsTCM and noTCM.

Main Results:

• riskTCM demonstrated significant effective dose reductions compared to mAsTCM across multiple regions: thorax (23%), abdomen (31%), pelvis (24%), and neck (27%).
• A lower, yet notable, dose reduction of 13% was observed for the head region compared to mAsTCM.
• The evaluated figure of merit was the potential reduction of effective dose at consistent image noise levels.

Conclusions:

• A risk-minimizing TCM approach (riskTCM) enables substantially greater effective dose reduction than conventional mAs-minimizing TCM.
• The proposed riskTCM method offers a more sophisticated and effective strategy for patient radiation dose optimization in CT imaging.