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  • Poster presentation
  • Open Access

Post-contrast non-selective double inversion recovery imaging of the coronary arteries in patients with coronary allograft vasculopathy

  • 1,
  • 1,
  • 2,
  • 2,
  • 2,
  • 2,
  • 1 and
  • 1
Journal of Cardiovascular Magnetic Resonance201113 (Suppl 1) :P241

https://doi.org/10.1186/1532-429X-13-S1-P241

  • Published:

Keywords

  • Inversion Recovery
  • Phantom Study
  • Inversion Recovery Sequence
  • Gadolinium Contrast Agent
  • Undergo Heart Transplantation

Introduction

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.

Methods

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.

Results

Simulations and phantom studies show that the IR sequence (fig.1a) only nulls one T1 species whereas the NS-DIR sequence (fig.1b) achieves excellent signal suppression over the desired T1-range.
Figure 1
Figure 1

Simulated M2 values (solid lines) and phantom SNR values (data points) for a) the IR sequence (T1 set to null T1 species 340ms for different heart rates) and b) the NS-DIR sequence (TI1 and TI2 values optimized to minimize M2 for a range between 200 and 1400ms for different heart rates.) N.B. The theoretical Mz values have been scaled in order to display the data on the same graph.

Patient studies showed that the NS-DIR sequence (fig.2a) achieved simultaneous suppression of the blood and myocardium. Only the areas of contrast uptake are visible, which correspond to the path of the LCA (fig.2b). In contrast, interpretation of the IR images (fig.2c and fig.2d) was hampered by the bright signal in the myocardium.
Figure 2
Figure 2

Post contrast imaging of the left coronary artery: a) NS-DIR TFE images, b) NS-DIR TFE images fused with coronary MRA, c) IR-TFE images and d) IR-TFE images fused with coronary MRA. Small arrows indicate enhancement of the coronary vessel walls and the large arrow indicates enhancement in the myocardium in the IR-TFE images.

Conclusion

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.

Authors’ Affiliations

(1)
Division of Imaging Sciences, King's College London, London, UK
(2)
Great Ormond Street Hospital for Children NHS Trust, London, UK

Copyright

© Peel et al; licensee BioMed Central Ltd. 2011

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.

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