Fully Automated, Quality-Controlled Cardiac Analysis From CMR: Validation and Large-Scale Application to Characterize Cardiac Function

Abstract

Objectives: This study sought to develop a fully automated framework for cardiac function analysis from cardiac magnetic resonance (CMR), including comprehensive quality control (QC) algorithms to detect erroneous output.

Background: Analysis of cine CMR imaging using deep learning (DL) algorithms could automate ventricular function assessment. However, variable image quality, variability in phenotypes of disease, and unavoidable weaknesses in training of DL algorithms currently prevent their use in clinical practice.

Methods: The framework consists of a pre-analysis DL image QC, followed by a DL algorithm for biventricular segmentation in long-axis and short-axis views, myocardial feature-tracking (FT), and a post-analysis QC to detect erroneous results. The study validated the framework in healthy subjects and cardiac patients by comparison against manual analysis (n = 100) and evaluation of the QC steps' ability to detect erroneous results (n = 700). Next, this method was used to obtain reference values for cardiac function metrics from the UK Biobank.

Results: Automated analysis correlated highly with manual analysis for left and right ventricular volumes (all r > 0.95), strain (circumferential r = 0.89, longitudinal r > 0.89), and filling and ejection rates (all r ≥ 0.93). There was no significant bias for cardiac volumes and filling and ejection rates, except for right ventricular end-systolic volume (bias +1.80 ml; p = 0.01). The bias for FT strain was <1.3%. The sensitivity of detection of erroneous output was 95% for volume-derived parameters and 93% for FT strain. Finally, reference values were automatically derived from 2,029 CMR exams in healthy subjects.

Conclusions: The study demonstrates a DL-based framework for automated, quality-controlled characterization of cardiac function from cine CMR, without the need for direct clinician oversight.

Keywords: CMR feature tracking; cardiac aging; cardiac function; cardiac magnetic resonance; machine learning; quality control.

Figure 1. Bland-Altman Plots for Cardiac Volumes

(A) Left ventricular (LV) end-diastolic volume (LVEDV), (B) left ventricular end-systolic volume (LVESV), (C) left ventricular end-diastolic mass (LVM), (D) right ventricular end-diastolic volume (RVEDV), and (E) right ventricular end-systolic volume (RVESV). The grey dotted line represents the mean bias; the pink dotted lines the limits of agreement. The p values represent the difference in mean bias from zero using a paired t-test. (F) The mean error in LV is a normalized volume curve for all cases, and both subgroups is shown.

Figure 2. Bland-Altman Plots for LV Filling and Ejection and Global Peak Strain Parameters

(A) Peak ejection rate (PER), (B) peak early filling rate (PEFR), (C) peak atrial filling rate (PAFR), (D) atrial contribution (AC), (E) peak global circumferential strain (Circ), (F) 2-chamber longitudinal strain (Ell_{_2Ch}), (G) 4-chamber longitudinal strain (Ell_{_4Ch}), and (H) radial strain (Rad). The grey dotted line represents the mean bias; the pink dotted lines the limits of agreement. The p values represent the difference in mean bias from zero bias using paired t-test. LAX = long-axis; LV = left ventricular; SAX = short-axis.

Central Illustration. Total Image-Analysis Pipeline Including Pre- and Post-Analysis QC Steps

An animation of the pipeline is shown in Supplemental Video 1. LV = left ventricle; QC = quality control; RV = right ventricle.