Reproducibility and observer variability of tissue phase mapping for the quantification of regional myocardial velocities

Abstract

To systematically investigate the reproducibility of global and segmental left ventricular (LV) velocities derived from tissue phase mapping (TPM). Breath held and ECG synchronized TPM data (spatial/temporal resolution = 2 × 2 mm2/20.8 ms) were acquired in 18 healthy volunteers. To analyze scan–rescan variability, TPM was repeated in all subjects during a second visit separated by 16 ± 5 days. Data analysis included LV segmentation, and quantification of global and regional (AHA 16-segment modal) metrics of LV function [velocity–time curves, systolic and diastolic peak and time-to-peak (TTP) velocities] for radial (Vr), long-axis (Vz) and circumferential (VΦ) LV velocities. Mean velocity time curves in basal, mid-ventricular, and apical locations showed highly similar LV motion patterns for all three velocity components (Vr, VΦ, Vz) for scan and rescan. No significant differences for both systolic and diastolic peak and TTP myocardial velocities were observed. Segmental analysis revealed similar regional peak Vr and Vz during both systole and diastole except for three LV segments (p = 0.045, p = 0.033, and p = 0.009). Excellent (p < 0.001) correlations between scans and rescan for peak Vr (R2 = 0.92), peak Vz (R2 = 0.90), radial TTP (R2 = 0.91) and long-axis TTP (R2 = 0.88) confirmed good agreement. Bland–Altman analysis demonstrated excellent intra-observer and good inter-observer analysis agreement but increased variability for long axis peak velocities. TPM based analysis of global and regional myocardial velocities can be performed with good reproducibility. Robustness of regional quantification of long-axis velocities was limited but spatial velocity distributions across the LV could reliably be replicated.

Cardiac Structure–Function MRI in Patients After Heart Transplantation

“…TPM data were analyzed using in‐house tools programmed in MatLab (MathWorks, Natick, MA). Analysis included manual delineation of endo‐ and epicardial LV contours and transformation of the acquired tridirectional velocities into radial velocities (representing contraction and expansion), longitudinal velocities (LV lengthening and shortening), and circumferential velocities (LV rotation), as described previously . Velocities were defined as positive for systolic contraction, shortening, or clockwise rotation.…”

“…Analysis included manual delineation of endo-and epicardial LV contours and transformation of the acquired tridirectional velocities into radial velocities (representing contraction and expansion), longitudinal velocities (LV lengthening and shortening), and circumferential velocities (LV rotation), as described previously. 20,23 Velocities were defined as positive for systolic contraction, shortening, or clockwise rotation. Peak and time-to-peak (TTP) velocities during systole and diastole were determined for radial and longitudinal directions.…”

A semiautomatic method for rapid segmentation of velocity‐encoded myocardial magnetic resonance imaging data

“…In TPM, optimal segmentation is crucial for accurate and reproducible results and its time‐consuming nature is often cited as a limiting factor . To measure myocardial velocities from a TPM scan, in every frame the myocardial pixels must be identified and separated from regions of high‐velocity signal from the blood and/or low‐signal, high‐noise regions.…”

“…To measure myocardial velocities from a TPM scan, in every frame the myocardial pixels must be identified and separated from regions of high‐velocity signal from the blood and/or low‐signal, high‐noise regions. Conventionally, this is done in a manual fashion, involving the delineation of all frames or a set of key frames , the latter incorporating simple temporal interpolation to fill in the intermediary frames.…”

Editorial for "Prognostic Value of Late Gadolinium Enhancement in Predicting Life‐Threatening Arrhythmias in Heart Failure Patients With Implantable Cardioverter‐Defibrillators"

“…For example, investigators observed increases in native T 1 and T 2 relaxation times along with a drop in 3D stain and global function in heart failure patients. More recently developed MRI sequences, such as displacement encoding with stimulated echoes (DENSE) strain encoded MRI and tissue phase mapping, may add new information on myocardial deformation and velocities in heart failure patients . The sensitivity and specificity of the new MRI multiparametric methods should be included in future studies to better identify the occurrence of life‐threatening arrhythmias and MACE.…”