- Meeting abstract
- Open Access
2092 Myocardial field distortions during first pass of a gadolinium based contrast agent in perfusion studies
© Ferreira et al; licensee BioMed Central Ltd. 2008
- Published: 22 October 2008
- Contrast Agent
- Myocardial Perfusion Image
- Gadolinium Base Contrast Agent
- Frequency Offset
- Contrast Agent Concentration
Myocardial Perfusion (MP) studies using MRI have lately improved in terms of resolution and coverage, providing a valuable contribution to the detection of Coronary Artery Disease (CAD). However, MP images are often affected by artifacts, most commonly the Dark Rim Artifact (DRA), which appears in the subendocardium during the first left-ventricular pass of the Contrast Agent (CA) mimicking an under-perfused region.
The exact origins of the DRA are unclear and several causes have been suggested: motion ; Gibbs truncation ; non-uniform k-space weighting ; and susceptibility associated with CA concentration [4–6].
In this work a method has been developed and used to measure the field distortions caused by the first pass of a CA in a typical perfusion setup, and determine how these distortions may depend on cardiac long-axis orientation.
Gd contrast agent (Magnevist-Schering; Germany), with a dose of 0.1 mmol/kg of body weight was injected at 5 mL/s in 12 patients (average age 49). Field plots were acquired in three short-axis slices, during the first pass of CA with the patients holding their breath for as long as comfortably possible during 40 R-R intervals. The study was performed using a 1.5 T scanner (Avanto; Siemens) with anterior/posterior phased array cardiac coils. A FLASH sequence was used with magnitude and phase reconstructions: TR/TE of 256/2.48 ms; base resolution 192 pixels; pixel size 1.8 × 1.8 × 10 mm to 2.2 × 2.2 × 10 mm; flip angle 12 degrees; bandwidth 744 Hz/pixel; GRAPPA, R = 1.7. The coil images were saved separately, and phase correction was disabled in image reconstruction.
Single-shot frequency-offset maps were calculated using Matlab (Mathworks; US-MA) where the phase image of each coil for the first frame (before CA) was subtracted from each subsequent frame's corresponding phase images, before magnitude-weighted phase combination. The first frame was chosen to be that before contrast arrival to the right ventricle but with the patient at a stable breath-hold position. Four ROIs were drawn in the subendocardium (septal, posterior, lateral, anterior) for each slice (basal, mid, apical), and frequency offsets as a function of time were extracted, measuring also the peak field distortion of each ROI during the contrast agent first pass. The in-vivo measurements were compared with numerical simulations and specially constructed phantoms that mimicked the LV chamber and expected susceptibility differences,
During the first-pass, B0 distortion occurs mainly in the subendocardium, and the same pattern is always observed (anterior/posterior positive; septal/lateral negative). The myocardial B0 distortion is larger in patients with a more "horizontal" heart. From these results it would appear that the field distortions are too weak to cause DRAs due to intravoxel dephasing.
- Storey P, et al: MRM. 2002, 48 (6): 1028-View ArticlePubMedGoogle Scholar
- Di Bella E, et al: MRM. 2005, 54 (5): 1295-PubMed CentralView ArticlePubMedGoogle Scholar
- Kellman P, Arai A: JCMR. 2007, 9 (3): 525-Google Scholar
- Arai A: Top MRI. 2000, 11 (6): 383-398.Google Scholar
- Fenchel Michael, et al: JMRI. 2004, 19 (5): 555-10.1002/jmri.20050.View ArticlePubMedGoogle Scholar
- Schreiber W, et al: JMRI. 2002, 16 (6): 641-10.1002/jmri.10209.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd.