MR Angiography Interpretation: Techniques and Pitfalls

Guidelines for Cardiovascular Magnetic Resonance Imaging from the Korean Society of Cardiovascular Imaging-Part 2: Interpretation of Cine, Flow, and Angiography Data

Cardiovascular magnetic resonance imaging (CMR) is expected to be increasingly used in Korea due to technological advances and the expanded national insurance coverage of CMR assessments. For improved patient care, proper acquisition of CMR images as well as their accurate interpretation by well-trained personnel are equally important. In response to the increased demand for CMR, the Korean Society of Cardiovascular Imaging (KOSCI) has issued interpretation guidelines in conjunction with the Korean Society of Radiology. KOSCI has also created a formal Committee on CMR guidelines to create updated practices. The members of this committee review previously published interpretation guidelines and discuss the patterns of CMR use in Korea.

Stenosis and Pseudostenosis of the Upper Extremity Arteries in Large-Vessel Vasculitis

Objective

Pseudostenosis is a magnetic resonance angiography (MRA) artifact that mimics arterial stenosis. The study objective was to compare imaging and clinical aspects of stenosis and pseudostenosis in a cohort of large‐vessel vasculitis (LVV), including giant‐cell arteritis (GCA) and Takayasu's arteritis (TAK).

Methods

Patients with LVV and comparator conditions (healthy or vasculopathies) underwent MRA of the aortic arch vessels. The subclavian and axillary arteries were systematically assessed for presence of stenosis and pseudostenosis by two independent readers. Serial and delayed imaging and clinical assessments were used to confirm suspected pseudostenoses. Multivariable regression analyses were used to identify associations between angiographic pathology and clinical findings.

Results

One hundred eighty‐four MRA scans were analyzed from patients with GCA (n = 36), TAK (n = 47), and comparators (n = 25). Pseudostenoses were frequently observed (48 of 184 scans, 26%) in the distal subclavian artery only on the side of injection and were shorter in length compared with true stenoses (25 mm vs 78 mm, P < 0.01). There was no difference in prevalence of pseudostenosis by diagnosis (GCA = 33%, TAK = 23%, comparator = 20%, P = 0.44), disease activity status (P = 0.31), or treatment status (P = 1.00). Percent and length of true stenosis were independently associated with pulse and blood pressure abnormalities in the upper extremity. Adjusting for length and stenosis degree, absence of collateral arteries was associated with arm claudication (odds ratio = 2.37, P = 0.03).

Conclusion

Although a pseudostenosis could be falsely interpreted as an arterial stenosis, radiographic and associated clinical features can help distinguish true disease from arterial susceptibility artifacts. In addition, the peripheral vascular examination can help to confirm a suspected true stenosis, as specific aspects of angiographic pathology are associated with vascular examination abnormalities in LVV.

Contrast-enhanced magnetic resonance angiography of the peripheral arteries: technique, tips, pitfalls and problems

Contrast-enhanced magnetic resonance angiography is a reliable way to assess peripheral vascular disease. This article reviews the basic physics behind this technique and discusses our institution's experience with regard to the clinical role, recent advances in image acquisition and use of contrast agents. Problems that can affect image quality and interpretation are also highlighted.

Technical inadequacies of peripheral contrast-enhanced magnetic resonance angiography: incidence, causes and management strategies

AIM

To assess the incidence, causes and effects of technical inadequacies in peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) and to discuss relevant management strategies.

MATERIALS AND METHODS

A retrospective analysis of 249 peripheral CE-MRA examinations was performed using the radiology department's RIS/PACS (radiology information system/picture archiving and communication system) database. All failed or technically inadequate MRAs were reviewed. In cases that underwent further imaging by conventional angiography (CA), we assessed if relevant arterial disease had been masked on the MRA.

RESULTS

Of the 249 examinations, 215 (86.3%) were technically satisfactory while 34 (13.7%) were a combination of technical inadequacies [29 cases (11.6%)] and examination failures [five cases (2%)]. The causes of technical inadequacies were: (1) venous contamination (13 cases; 5.2%), (2) motion-induced subtraction artefact (eight cases; 3.2%), (3) stent-induced artefact (four cases; 1.6%), (4) inadequate scan coverage (two cases; 0.8%), and (5) contrast timing error (two cases; 0.8%). The causes of failed examinations were: (1) inability to tolerate lying in the scanner (three cases; 1.2%) and (2) inability to fit into the scanner (two cases; 0.8%). Fifteen (44.1%) of the 34 cases underwent further imaging by CA, and in eight of these there was significant arterial disease that was missed on the MRA.

CONCLUSION

Technical inadequacies occur in a small but significant proportion of peripheral CE-MRAs and can mask significant arterial disease. Knowledge of the potential causes of technical problems and the relevant management options is important for quality assurance and for limiting the need for an alternative investigation.