Channelized hotelling observer-based low-contrast detectability on the ACR CT accreditation phantom: Part II....

Area of Science:

• Medical Imaging Physics
• Radiology
• Image Analysis

Background:

• Routine CT quality control lacks objective, quantitative evaluation for low-contrast detectability correlating with human performance.
• Channelized Hotelling observer (CHO) is a promising tool but previously considered impractical due to high scan repetition requirements.
• Previous work optimized CHO for the ACR CT phantom, enabling accurate detectability index (d') measurement with only 1-3 repeat scans.

Purpose of the Study:

• To validate the repeatability of a CHO-based low-contrast evaluation method.
• To assess the method's performance across four different CT scanner models.
• To utilize the American College of Radiology (ACR) CT accreditation phantom for standardization.

Main Methods:

• Repeatability testing on four CT scanners (Siemens Force/Alpha, Canon Prism/Prime SP).
• Acquisition of 10 phantom repositionings, with 3 scans per repositioning at 24, 12, and 6 mGy.
• Application of CHO to assess low-contrast object detectability (4-6 mm) and evaluation of repeatability using P<15%.

Main Results:

• CHO measurements demonstrated high repeatability (P<15% of 98.8%-99.9%) at 12 mGy with iterative reconstruction (IR) on all tested scanners.
• Repeatability remained high across different dose levels and object sizes on individual scanners (P<15% ranging from 91.5% to 99.998%).
• High repeatability was also observed for deep learning reconstructions and photon-counting-detector (PCD)-CT modes (P<15% > 96.5%).

Conclusions:

• CHO offers highly repeatable measurements for low-contrast detectability on the ACR phantom, exceeding 95% probability within ±15% tolerance.
• Repeatability is maintained with advanced techniques like deep learning reconstruction and PCD-CT.
• The study confirms the feasibility of practical CHO implementation for routine CT quality control and performance evaluation.