Patient Size Estimation Methods for CMS Size-Adjusted Dose Reporting: Variability, Challenges, and Recommendations

Area of Science:

• Medical Imaging Physics
• Radiology Quality Assurance

Background:

• The Centers for Medicare & Medicaid Services (CMS) introduced the CT size-adjusted dose (SAD) quality measure (CMS1074v3) linked to reimbursement.
• Inconsistent patient size estimation methods introduce variability, potentially compromising the reliability of SAD measurements and quality assessments.

Purpose of the Study:

• To evaluate five distinct patient size estimation methods.
• To assess the impact of these methods on CT size-adjusted dose (SAD) values and compliance with CMS thresholds.

Main Methods:

• Retrospective analysis of 719 CT examinations across seven protocols (five abdomen, two chest).
• Evaluation of five patient diameter calculation methods: HU Value Thresholding, Water-Equivalent Diameter (WED), Lateral/AP Conversion, LAT×AP, and (LAT + AP)/2.
• Statistical analysis using Kruskal-Wallis and pairwise tests to identify significant differences.

Main Results:

• Significant variability in SAD values was observed across different calculation methods.
• Attenuation-based methods (HU, WED) overestimated SAD in chest scans; projection-based methods showed higher variability in abdominal scans.
• Method-dependent variability affected compliance with CMS dose thresholds, leading to more failures with specific methods in chest and abdominal protocols. Urogram protocol showed unexpectedly low SAD values.

Conclusions:

• Inconsistent patient size estimation and protocol mapping present technical challenges for the CMS SAD quality measure.
• Standardizing examination mapping and reconsidering dose thresholds are recommended to improve clinical alignment and measure reliability.