The New CMS Measure of Excessive Radiation Dose or Inadequate CT Image Quality: Methods for Size-Adjusted Dose and Their Variabilities

The Centers for Medicare & Medicaid Services (CMS) has introduced CMS1074v2, a quality measure for computed tomography (CT) that assesses radiation dose and image quality across 18 CT exam categories. This measure mandates the calculation of size-adjusted dose (SAD) using patient effective diameter and predefined size-adjustment coefficients. However, variability in SAD calculation methods raises concerns about standardization, compliance, and clinical applicability. This study evaluates five commonly used methods for estimating effective diameter and their impact on SAD determination in thoracic and abdominal CT protocols. A retrospective analysis of 719 CT exams was performed, comparing SAD values across different calculation approaches. Results indicate significant variability in SAD, with attenuation-based methods overestimating SAD in chest exams and projection-based methods exhibiting greater variability in abdominal exams. The findings highlight potential inconsistencies in CMS-defined dose thresholds and challenges in applying the measure across diverse patient populations and institutional imaging practices. Addressing these inconsistencies is critical for ensuring accurate dose reporting and maintaining diagnostic integrity in CT imaging.