Myocardial T2 mapping using wideband T2 preparation gradient echo readout for patients with implantable cardiac devices at 1.5T.

BACKGROUND

Myocardial T2 mapping enables non-invasive assessment of inflammation and edema. However, in patients with implantable cardiac devices, such as pacemakers or defibrillators (ICDs), off-resonance effects often cause severe image artifacts and inaccurate T2 values.

PURPOSE: The aim of this study was to develop and evaluate a wideband T2-prepared gradient-echo (GRE) myocardial T2 mapping sequence combined with an advanced patch-based denoising approach, designed to reduce artifacts and improve image quality in device-implanted patients at 1.5T.

METHODS

A T2 preparation with wideband adiabatic refocusing pulses (5.0 kHz bandwidth) was integrated into a breath-held 2D GRE T2 mapping sequence (TE = 0/27/55ms). Patch-based denoising was applied after image reconstruction. The sequence was tested in a phantom, 8 healthy volunteers with and without ICDs placed on their chests, 13 patients without devices, 7 patients with ICDs or pacemakers, and 1 sheep scanned before and after induced myocardial infarction with and without external ICD. The proposed sequence was compared against reference conventional GRE and balanced steady-state free-precession (bSSFP) T2 mapping. Patch-based denoising was optimized in patients without devices and impact on T2 precision and accuracy was assessed. Phantom studies included Bland-Altman and correlation analyses between the sequences. In-vivo performance was assessed through global and segmental T2 quantification, coefficient of variation (COV), artifact scoring, and edema detection. ANOVA with Bonferroni correction and pairwise testing were used for statistical comparisons.

RESULTS

In subjects without devices, wideband and conventional GRE T2 mapping yielded comparable T2 values (P = 0.60). With ICDs, conventional GRE T2 mapping underestimated global T2 by 16% (P<0.001) and increased segmental COV up to 30%. In contrast, wideband GRE T2 mapping provided accurate T2 values (P = 0.56) and preserved edema detection, showing relative T2 elevations of 44% comparable to bSSFP. Patch-based denoising significantly improved precision (P = 0.006) without biasing mean values (P = 0.999). Results were consistent across phantom, volunteer, patient, and animal experiments, including animal ex-vivo histology confirmation.

CONCLUSION

Wideband GRE T2 mapping substantially reduced device-related artifacts, provided accurate T2 values, and allowed edema detection, offering a clinically feasible solution for patients with cardiac implants in this initial study.