National Heart & Lung Institute, Imperial College London
Doi
Abstract
The detection of diffuse fibrosis is of particular interest in congenital heart disease patients,
including repaired Tetralogy of Fallot (rTOF), as clinical outcome is linked to the accurate
identification of diffuse fibrosis.
In the Left Ventricular (LV) myocardium native T1 mapping and Diffusion Tensor Cardiac
Magnetic Resonance (DT-CMR) are promising approaches for detection of diffuse fibrosis. In
the Right Ventricle (RV) current techniques are limited due to the thinner, mobile and
complex shaped compact myocardium. This thesis describes technical development of RV
tissue characterisation methods.
An interleaved variable density spiral DT-CMR method was implemented on a clinical 3T
scanner allowing both ex and in vivo imaging. A range of artefact corrections were
implemented and tested (gradient timing delays, off-resonance and T2* corrections). The off-
resonance and T2* corrections were evaluated using computational simulation demonstrating
that for in vivo acquisitions, off-resonance correction is essential.
For the first-time high-resolution Stimulated Echo Acquisition Mode (STEAM) DT-CMR data
was acquired in both healthy and rTOF ex-vivo hearts using an interleaved spiral trajectory
and was shown to outperform single-shot EPI methods.
In vivo the first DT-CMR data was shown from the RV using both an EPI and an interleaved
spiral sequence. Both sequences provided were reproducible in healthy volunteers. Results
suggest that the RV conformation of cardiomyocytes differs from the known structure in the
LV.
A novel STEAM-SAturation-recovery Single-sHot Acquisition (SASHA) sequence allowed the
acquisition of native T1 data in the RV. The excellent blood and fat suppression provided by
STEAM is leveraged to eliminate partial fat and blood signal more effectively than Modified
Look-Locker Imaging (MOLLI) sequences. STEAM-SASHA T1 was validated in a phantom
showing more accurate results in the native myocardial T1 range than MOLLI. STEAM-SASHA
demonstrated good reproducibility in healthy volunteers and initial promising results in a
single rTOF patient.Open Acces