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Magnetic resonance imaging of coronary arteries: technique and preliminary results
D J Pennell1, J Keegan, D N Firmin
1Magnetic Resonance Unit, Royal Brompton National Heart and Lung Hospital, London.
Insights
Rapid magnetic resonance imaging of coronary arteries is feasible for non-invasive diagnosis. This technique successfully identified occlusions and bypass grafts, offering a promising alternative to invasive angiography.
Area of Science:
- Cardiovascular Imaging
- Medical Diagnostics
- Biomedical Engineering
Background:
- Coronary artery disease management relies on invasive x-ray contrast angiography, posing risks.
- Non-invasive imaging is needed due to the challenges of small, tortuous coronary vessels and motion artifacts.
Purpose of the Study:
- To develop rapid magnetic resonance imaging (MRI) for visualizing coronary arteries.
- To assess the feasibility and accuracy of MRI in healthy individuals and patients with coronary artery disease.
Main Methods:
- Utilized gradient echoes and segmented k-space MRI with fat suppression, acquired during breath-holds in late diastole.
- Developed an imaging strategy for proximal coronary arteries, including longitudinal views.
- Studied 21 healthy controls and 5 patients with established coronary artery disease.
Main Results:
- Successful imaging was achieved in 22 out of 26 subjects.
- High identification rates for major coronary arteries (left main, LAD, RCA, LCx) and accurate diameter measurements.
- MRI findings correlated well with x-ray contrast angiography, and occluded arteries and vein grafts were correctly identified.
Conclusions:
- Magnetic resonance coronary angiography is a feasible, non-invasive imaging technique.
- Breath-hold, fat-suppressed MRI in late diastole yields good results for visualizing coronary arteries, occlusions, and grafts.
- Further research is needed to evaluate its efficacy in detecting coronary stenosis and measuring flow velocity.
Background:
Coronary artery imaging is an important investigation for the management of coronary artery disease. The only reliable technique presently available, x ray contrast angiography, is invasive and is associated with a small morbidity and mortality. Alternative non-invasive imaging would be useful, but the small calibre and tortuosity of the coronary vessels, and cardiac and respiratory motion create formidable imaging problems.
Objective:
The development of rapid magnetic resonance imaging of the coronary arteries.
Patients:
21 healthy controls and five patients with coronary artery disease established by x ray contrast angiography, of whom two had undergone bypass grafting.
Methods:
Magnetic resonance imaging was performed with gradient echoes and a segmented k-space technique, such that a complete image was acquired in 16 cardiac cycles during a breathhold. The signal from fat was suppressed and images were acquired in late diastole to reduce artefact from cardiac motion. An imaging strategy was developed for the proximal arteries, including longitudinal imaging from oblique planes defined according to the origins and the continuation of the arteries in the atrioventricular grooves or interventricular sulcus.
Results:
Of the 26 subjects studied, 22 were imaged successfully. Identification of the artery was possible for the left main stem, left anterior descending, right coronary, and left circumflex arteries respectively in 95%, 91%, 95%, and 76%. The arterial diameter at the origin could be measured in 77%, 77%, 81%, and 63%. The mean (SD) arterial diameter in each case (4.8 (0.8), 3.7 (0.5), 3.9 (0.9), and 2.9 (0.6) mm) was not significantly different from reference values. The mean length of artery visualised was 10.4 (5.2), 46.7 (22.8), 53.7 (27.9), and 26.3 (17.5) mm. In 12 healthy men the total coronary area was 30.9 (9.2) mm2 and the ratio compared with body surface area was 16.4 (4.4) mm2m2 (both p = NS compared with reference values). In seven patients in whom x ray contrast coronary angiography was available, the proximal arterial diameter was 3.9 (1.1) mm measured by magnetic resonance and 3.7 (1.0) mm by x ray contrast angiography (p = NS). The mean difference between the measurements was 0.2 (0.5) mm, and the coefficient of variation was 13.7%. All five occluded coronary arteries were identified, as were all three vein grafts. In two patients insertion of the graft into the native arteries was identified.
Conclusions:
Magnetic resonance coronary angiography is feasible. Good results were obtained by a breath-hold, fat suppression technique, gated to late diastole. Arterial occlusions and vein grafts were readily identified. Further studies are required to establish its value in the detection of coronary stenosis and to develop the measurement of coronary flow velocity which could be used to quantify the severity of the stenosis.