Relationship between Measurement Errors in Myocardial T₁ Mapping and Heart Rate

Abstract

Purpose: Modified Look-Locker inversion recovery (MOLLI) using a 5s(3s)3s scheme is robust to tachycardia, but some errors are occasionally observed in myocardial T 1 mapping. We sought to evaluate the relationship between measurement errors in T 1 mapping and heart rate (HR) using a confidence map. Methods: We enrolled 69 male patients with normal native T 1 values of the septal myocardium measured by a 5s(3s)3s MOLLI. The degree of measurement errors in the septal myocardium was assessed by two independent observers on a confidence map using a 4-point scale: 0, no errors; 1, errors located on the myocardial contour; 2, errors extended into the myocardial contour; and 3, errors extended into the midwall. We compared the scores of measurement errors and the average, maximum, minimum or variability of the HR indicated during the MOLLI scan (iHR), image phases of MOLLI or left ventricular ejection fraction (LVEF). Results: Patients with score >1 for the septal myocardium had significantly lower minimum iHR than those with a score ≤1 (P < 0.01; 49.8 ± 10.1 vs. 59.6 ± 9.7 beat per min). Conclusion: The confidence map shows more measurement errors in patients with lower minimum iHR. The myocardial T 1 values should be measured carefully in patients with bradycardia during MOLLI scanning.

T1T2 Mapping and Texture Analysis of Cine and T2-weighted Magnetic Resonance Imaging to Detect Myocardial Tissue Changes Associated with Chronic Kidney Disease

“…Cine SSFP imaging was acquired with the imaging parameters as follows: TR, 3.2 ms; TE, 1.6 ms; FOV, 350 x 350 mm 2 , imaging matrix, 192 x 170; and slice thickness, 8 mm. T1 mapping was performed with a 5s (3s) 3s modi ed Look-Locker inversion recovery sequence acquired with a single-shot SSFP readout 27 . Therefore, 7 to 11 multicontrast images were acquired during 11-s breath-holding in short-axis midventricular slices.…”

“…Color-coded T1 and T2 maps were automatically generated on the operator console after T1T2 mapping scanning, and a team of three MR-dedicated radiological technologists measured T1T2 values of the septal myocardium according to the previous study 10,29 . Texture analysis was performed by a radiologist with 26 years of experience in cardiac MRI using the open-access software (MaZda; Institute of Electronics, Technical University of Lodz, Poland) 23,27,30 . The intensity range of the image under texture analysis was normalized by the default method: the intensity changes of the image ranged from 1 to 256 and 6 bits per pixel were used for image quantization.…”