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Contrast-enhanced MR angiography of the abdomen (3T) after bolus injection of only 7 ml Gd-DTPA (single dose).
Navigator SSFP MR-Angiography of the aorta and coronary arteries without injection of contrast media with 1.5T.
Image of the Aorta ascendens and the ventricle system without motion artefacts as advantage compared with contrast-enhanced MRI sequences.
MR Angiography: A future without contrast media?
By Stefan G Ruehm MD PhD, Associate Professor of Radiology at the David Geffen School of Medicine, UCLA, California, and Director of Diagnostic Cardiovascular Imaging, CT, UCLA Radiological Sciences
Developments in MRI over the last few years have revolutionized the diagnosis and therapy of cardiovascular diseases. Contrast-enhanced MR angiography has established itself as a non-invasive, standard procedure for the diagnosis of vascular diseases in the thorax, abdomen and periphery.
[Bild-] It is characterized by fast acquisition times and lack of invasiveness. The three-dimensional display of data sets is similar to that achieved with conventional angiographic images and radiologists and clinicians are familiar with it. The paramagnetic contrast medium based on Gadolonium (Gd) is normally very well tolerated. Side effects such as allergic reactions are extremely rare. Unlike with iodine containing contrast media, if the maximum dose is adhered to there is no nephrotoxicity
However, the safe image of contrast-enhanced MR examinations has been questioned with recent reports about a link between the systemic and incurable disease nephrogenic systemic fibrosis (NSF) and the administration of contrast media containing Gadolinium. So far the occurrence of the disease appears to be limited to patients with severely limited kidney function. Ironically, it is often patients with increasingly deteriorating kidney function for whom an MR angiography is particularly indicated to eliminate a possible renal artery stenosis. In the past it was quite common for patients to be given twice or even triple the usual dose of contrast medium for this examination. Renal artery stenoses mostly develop because of arteriosclerotic changes. The systemic disease pattern of arteriosclerosis and associated diseases, such as high blood pressure and strokes, often require clarification in several vascular territories for the elimination of vascular pathologies. In the past, whole-body MR angiography was successfully used as an efficient screening procedure. All in all, it would appear sensible to reduce the total dose of contrast media because of the imminent risk of NSF. Whole-body MR angiography offers advantages here. It allows for more efficient use of the dose of contrast media administered compared with conventional protocols limited to a single vascular area. This makes it possible to reduce the amount of contrast media administered compared with the conventional procedure where separate doses of contrast media are injected for the different vascular territories to be displayed.
Navigator SSFP MR-Angiography of the aorta and coronary arteries without injection of contrast media with 1.5T.
Despite promising strategies for the reduction of contrast media, examinations completely without contrast media would be desirable, particularly for patients with limited kidney function or for general risk and cost reduction purposes, such as screening protocols. Where in the past, and based on individual indication, native sequences such as Time of Flight (TOF) or PC MR angiography, which are still used today, were only of limited use as an alternative to contrast-enhanced MR angiography procedures because of motion artifacts, saturation effects and prohibitively long acquisition times for large vascular areas, state-free precession (SSFP) sequences are becoming increasingly important as an alternative.
Image of the Aorta ascendens and the ventricle system without motion artefacts as advantage compared with contrast-enhanced MRI sequences.
For patients with normal kidney function, we should weigh up the advantages of the potential gain of additional information resulting from contrast-enhanced examination protocols against the risk reduction achieved through foregoing the administration of contrast media, along with other aspects such as acceptance among patients and cost factors.
Contrast-enhanced MR angiography is sure to retain its outstanding significance in non-invasive vascular diagnostics in the future. However, in the interest of a general cost and risk reduction, careful assessment of individual indication along with selective use of protocols with reduced doses of contrast media or of protocols without contrast media is mandatory.
This article was published on 06/03/2008