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Post-contrast non-selective double inversion recovery imaging of the coronary arteries in patients with coronary allograft vasculopathy
© Peel et al; licensee BioMed Central Ltd. 2011
Published: 2 February 2011
The uptake of gadolinium contrast agent in coronary walls may indicate metabolically-active atherosclerosis (Maintz et al, 2006 ) and therefore be useful in the setting of coronary allograft vasculopathy (CAV). The interpretation of inversion recovery (IR) images can be hampered by signal from tissues with longer T1 times (particularly the myocardium) as tissue suppression is T1 dependent and only optimal for one specific T1 species (e.g. blood). We sought to improve contrast-enhanced coronary vessel wall imaging using a novel non-selective double inversion recovery (NS-DIR) prepulse that provides signal suppression over a wide user-defined T1-range.
The NS-DIR prepulse with two time delays, TI1 and TI2, was implemented on a 1.5T MR scanner. TI1 and TI2 were optimized in MATLAB simulations by minimizing MZNS-DIR over a user-defined T1-range for a given heart rate.
A T1-phantom containing 11 T1-samples (T1-range=120ms-1730ms) was imaged with the IR and NS-DIR pre-pulses for simulated heart rates between 45 and 105bpm. For each prepulse, the signal-to-noise ratio (SNR) was calculated for each sample.
Nine patients who had undergone heart transplantation (ages=12-17y) were imaged ~20minutes after injection of 0.2ml/kg Gadobutrol using a 32-channel coil on a 1.5T MR Scanner. Firstly a coronary MRA was performed followed by a targeted, free-breathing, ECG-triggered, 3D-IR segmented gradient-echo (TFE) sequence along the right and left coronary arteries. Imaging parameters included spatial-resolution=1.25x1.25x3mm, TR/TE=3.5/1.4ms, FA=30° and the TI was chosen to null blood from a Look-Locker sequence. Subsequently, identical planes were repeated with the IR replaced by the NS-DIR pre-pulse with imaging parameters maintained. Inversion times TI1 and TI2 were set to suppress tissues with T1 values between 200-1400ms according to the patient’s heart rate. Imaging was performed every heartbeat at the mid-diastolic rest period.
Simulations and phantom studies demonstrate that the NS-DIR sequence exhibits excellent tissue suppression over a wide T1-range. Preliminary patient data show improvement in contrast agent visualization in the coronary vessel walls in patients with CAV.
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.