Northwestern Radiology :: Cardiovascular Imaging

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Techniques

Cardiovascular MRI continues to evolve, below are some of the techniques we currently use to perform testing.

Cine MRI

The introduction of steady-state free precession (SSFP) pulse sequences has revolutionized cine MRI of the heart. These techniques have inherent high signal and produce high contrast images of the blood pool and myocardium, without the injection of contrast.

Morphology

Cardiac morphology, including cardiac masses, can readily be evaluated with Cardiac MR (magnetic resonance). To evaluate for structure and masses, we use a dark blood T2 HASTE or T1 turbo SE sequence with a double inversion pulse technique. In these sequences, all moving blood will be black.

Myocardial perfusion

Cardiac MR (magnetic resonance) perfusion techniques are sensitive for the detection of myocardial ischemia. It is proving to be a useful noninvasive modality for detecting significant stenoses in patients suspected of having coronary artery disease (CAD).

1st pass high resolution imaging

First pass imaging can also be implemented such that a single high-resolution slice is acquired per heartbeat. This is different to first pass myocardial perfusion imaging where multiple slices are acquired in each heartbeat.

Viability

Assessment of myocardial viability following a myocardial infarction is perhaps the most frequent indication for requesting a Cardiac MR. Viability studies are based on delayed enhancement imaging. Approximately 10 minutes following contrast administration, areas of infarcted myocardium are noted to “hyperenhance” relative to the normal myocardium. This hyperenhancement represents the accumulation of gadolinium in the extracellular space, due to the loss of membrane integrity in the infarcted tissue.

Flow quantification

Cardiac MR can be used to calculate velocity and flow, providing additional quantitative information in the evaluation of the heart. Flow quantification is analogous to Doppler ultrasound in which moving blood can be given a positive or negative value, depending on the direction of flow.

MR angiography

Several recent technical advances have placed MR angiography at the forefront of noninvasive imaging techniques for evaluating vascular disease. Contrast-enhanced MRA is a non-invasive investigation where Gadolinium contrast is injected through a peripherally placed intravenous cannula and images are acquired using MRI, thus avoiding ionizing radiation.