The management of a patient with arterial occlusive disease has to be planned in the context of the epidemiology of the disease and, in particular, the apparent risk factors or markers predicting spontaneous deterioration. It is obvious that proper management of arterial disease requires a comprehensive assessment of the underlying vascular morphology.
Since atherosclerotic disease affects the entire arterial system, extended coverage allowing the concomitant assessment of the arterial system from supraaortic arteries to the distal runoff vessels appears desirable. Subsequent parenchymal enhancement and contrast dose limitations had initially curtailed contrast-enhanced 3D MRA to the display of the arterial territory contained within a single field-of-view extending over 40–48 cm. The implementation of “bolus chase” techniques extended coverage to encompass the entire run-off vasculature, including the pelvic, femoral, popliteal and trifurcation arteries. The implementation of faster gradient systems has laid the foundation for a further extension of the bolus chase technique: whole body coverage extending from the carotid arteries to the trifurcation vessels with 3D MRA has become possible in merely 72 seconds. The whole-body MRA-concept is based on the acquisition of five slightly overlapping 3D data sets acquired in immediate succession. The first data set covers the aortic arch, supraaortic branch arteries and the thoracic aorta, while the second data set covers the abdominal aorta with its major branches including the renal arteries. The third data set displays the pelvic arteries, and the last two data sets cover the arteries of the thighs and calves, respectively. Correlation with a limited number of regional DSA examinations revealed the diagnostic performance of whole-body MRA to be sufficient to warrant its consideration as a non-invasive alternative to DSA. The performance of whole-body MRA was further improved with the introduction of AngioSURF, which integrates the torso-surface coil for signal reception. Use of the surface coil results in higher SNR and CNR values translating into sensitivity and specificity values of 95.3% and 95.2%, respectively, for the detection of significant stenoses (luminal narrowing > 50%) in lower extremity peripheral vascular disease.
For the AngioSURF exam all patients are placed feet first within the bore of the magnet and examined in the supine position on the fully MR-compatible AngioSURF platform, which had been placed on the existing table top. The AngioSURF platform (MR-Innovation GmbH, Essen, Germany) fits on most standard MR systems manufactured by Siemens, Erlangen, Germany. 240cm in length, the platform is placed on seven pairs of roller bearings, which are anchored within the existing patient table. Up to six 400mm 3D data sets can be acquired in immediate succession. Markers permit adjustment of the desired field-of-view. Signal reception is accomplished using posteriorly located spine coils and an anteriorly located torso phased array coil, which remains stationary within the bore. While the two utilised elements of the spine coil are integrated in the patient table, the standard torso phased array coil is anchored in a height-adjustable holder, which remains fixed to the stationary patient table. Thus, data for all five stations are collected with the same stationary coil set positioned in the isocentre of the magnet. A weight-adjusted dosage of 0.2mmol/kg bw Gd-BOPTA (Multihance®, Bracco, Italy) diluted with 0.9% of normal saline to a total volume of 60ml is automatically (MR Spectris, Medrad, Pittsburgh, PA) injected using a biphasic protocol: the first half is injected at a rate of 1.3ml/s, while the second half is administered at a rate of 0.7ml/s. The contrast is flushed with 30 ml of saline injected at 1.3ml/s.
In a series of 100 consecutive patients with PVD who were initially referred for the MR-based assessment of the peripheral vasculature, the applied AngioSURF exam revealed additional clinically relevant disease in 25 patients (33 segments): renal artery narrowing (15), carotid arterial stenosi (12), subclavian artery stenosis (2), and AAA (4).
The high degree of concomitant arterial disease in patients with peripheral vascular disease is not surprising. It merely underscores the systemic nature of atherosclerosis. Patients with intermittent claudication are at particularly high risk of atherosclerotic disease affecting other parts of the circulation. PVD, due as it is to atherosclerosis, is rarely an isolated disease process.
The extent of coexisting cardiovascular disease needs to be appreciated to ensure that the clinician will treat PVD in a true context. Studies on the prevalence of coronary artery disease (CAD) in patients with PVD show that history, clinical examination, and electrocardiography typically indicate the presence of CAD in 40% to 60% of such patients, although this may often be asymptomatic as it is masked by exercise restrictions in these patients. The link between PVD and cerebrovascular disease (CVD) seems to be weaker than that with CAD. Using duplex sonography, carotid disease has been found in 26% to 50% of patients with PVD. Most of these patients will have a history of cerebral events or a carotid bruit and seem to be at increased risk of further events.
The fact that in our series 12 unsuspected carotid lesions in 10 patients were identified highlights the often too symptom-focused means of patient questioning. Since all studied patients presented with symptoms suggestive of peripheral vascular disease, the patients’ histories were focused on that region. Only very direct questioning revealed additional symptomatology suggesting carotid disease in three patients. Approximately one-fourth of PVD patients have hypertension, and in these patients consideration should be given to the possibility of renal artery narrowing. 13 patients (13%) showed renal artery disease with a luminal narrowing > 50%.
There is ongoing controversy about the value of screening all patients with PVD, symptomatic or not, for carotid disease and aortic aneurysms. There is no doubt that claudicant patients are more likely to have significant asymptomatic disease in these areas than the general population, but the treatment of asymptomatic carotid disease is still controversial, and there is the issue of yield versus cost of such screening tests.
Non-invasiveness, three-dimensionality, extended coverage and high contrast conspicuity are the characteristics of whole- body MR angiography that combine to allow a quick, risk-free, and comprehensive screening-evaluation of the arterial system in patients with atherosclerosis.
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