Effects of adaptive or fixed thresholds and different platforms on the assessment of plaque characteristics using coronary computed tomography angiography.

Background: Coronary computed tomography angiography (CCTA) is used to evaluate components of atherosclerosis. Either adaptive or diverse, fixed Hounsfield Units (HU) are used to define components such as low attenuation (LAP), mixed (MP) and calcified plaque (CP). Comparisons of different platforms and different thresholding approaches have not been extensively evaluated. We compare two fixed threshold options to an adaptive threshold option within a specific platform and to fixed threshold options measured with another platform.

Methods: Coronary segments (n ​= ​24) of good image quality, with well-defined boundaries and representing a broad range of atheroma were analyzed for LAP, MP and CP. Thresholds for LAP vs MP and MP vs CP were either Fixed, Fixed or based on an automatically determined Adaptive option. Pearson correlation and Bland-Altman analyses were undertaken.

Results: Within a single platform, measures were highly correlated irrespective of use of Adaptive or Fixed and Fixed thresholds (R ​≥ ​0.819, p ​< ​0.000001). The correlation slope for measures of LAP progressively diminished comparing the Adaptive versus Fixed and the Fixed versus the Fixed approaches but bias was small. Between-platform comparisons yielded less optimal results, particularly with respect to measures of LAP and with one platform yielding both very small LAP volumes and very small ranges of volumes.

Conclusion: Measures of plaque components are highly correlated irrespective of use of Adaptive or Fixed threshold approaches within a given platform. But measures are more affected by the specific proprietary algorithms employed than by specific thresholding options, especially for LAP.