Task-dependent estimability index to assess the quality of cardiac computed tomography angiography for quantifying coronary stenosis

Abstract

. Purpose: Quantifying stenosis in cardiac computed tomography angiography (CTA) images remains a difficult task, as image noise and cardiac motion can degrade image quality and distort underlying anatomic information. The purpose of this study was to develop a computational framework to objectively assess the precision of quantifying coronary stenosis in cardiac CTA. Approach: The framework used models of coronary vessels and plaques, asymmetric motion point spread functions, CT image blur (task-based modulation transfer functions) and noise (noise-power spectrums), and an automated maximum-likelihood estimator implemented as a matched template squared-difference operator. These factors were integrated into an estimability index ( ) as a task-based measure of image quality in cardiac CTA. The index was applied to assess how well it can to predict the quality of 132 clinical cases selected from the Prospective Multicenter Imaging Study for Evaluation of Chest Pain trial. The cases were divided into two cohorts, high quality and low quality, based on clinical scores and the concordance of clinical evaluations of cases by experienced cardiac imagers. The framework was also used to ascertain protocol factors for CTA Biomarker initiative of the Quantitative Imaging Biomarker Alliance (QIBA). Results: The index categorized the patient datasets with an area under the curve of 0.985, an accuracy of 0.977, and an optimal threshold of 25.58 corresponding to a stenosis estimation precision (standard deviation) of 3.91%. Data resampling and training–test validation methods demonstrated stable classifier thresholds and receiver operating curve performance. The framework was successfully applicable to the QIBA objective. Conclusions: A computational framework to objectively quantify stenosis estimation task performance was successfully implemented and was reflective of clinical results in the context of a prominent clinical trial with diverse sites, readers, scanners, acquisition protocols, and patients. It also demonstrated the potential for prospective optimization of imaging protocols toward targeted precision and measurement consistency in cardiac CT images.

Coronary stenosis quantification in cardiac computed tomography angiography: multi-factorial optimization of image quality and radiation dose

“…The order of the feature importance for the approximated EPF well matched with the reported order in an earlier study of individual features. 16 For specific values of the patient attributes, the approximated EPF for four different effective rotation times, namely 0.125, 0.2, 0.275, and 0.35 seconds, are depicted in Fig. 4.…”

“…We employed the methods outlined in Refs. 15 and 16 to calculate the estimability index. According to statistical decision theory, the maximum likelihood of correct estimation in the presence of Gaussian distributed stochastic noise is obtained by minimizing the squared difference between the given noise-contaminated data instance and a noise-free template of a known parameter value 17 .…”

“…Schematic of the employed method to calculate the e′ value 16 . We developed a plaque model for a certain stenosis percentage (Sd) and used motion blur effects and noise to generate multiple noisy instances of the plaque.…”

“…17 In Ref. 16, a single synthesized stochastic noise and motion degraded image with its corresponding bank of pre-computed templates was generated from computational stenosis models with predefined diameters. The minimum least square difference was calculated between the synthesized images and the templates, forming a distribution for the actual stenosis values.…”

“…2 Schematic of the employed method to calculate the e 0 value. 16 We developed a plaque model for a certain stenosis percentage (S d ) and used motion blur effects and noise to generate multiple noisy instances of the plaque. We constructed noise-free templates with varying stenosis percentages centered around S d for the observer (ground truth templates).…”