Kai Yiu J.A.M. Ho

Three‐dimensional contrast‐enhanced moving‐bed infusion‐tracking (MoBI‐track) peripheral MR angiography with flexible choice of imaging parameters for each field of view

A technique to image peripheral arteries with flexible choice of scan parameters for separate stations was developed based on moving‐bed single‐bolus three‐dimensional gradient‐recalled echo magnetic resonance angiography. A volunteer study yielded higher signal‐ and contrast‐to‐noise ratios, less venous enhancement, and better subjective interpretability compared with imaging with fixed parameters for each station. Additionally, six patients were imaged to test the feasibility of the new method in a clinical setting. Imaging peripheral arteries with the new technique in volunteers yielded better image quality and is feasible for patients. J. Magn. Reson. Imaging 2000;11:368–377.

Motion of the distal renal artery during three-dimensional contrast-enhanced breath-hold MRA.

To study the potential detrimental effects of renal motion on breath‐hold three‐dimensional contrast‐enhanced (CE) magnetic resonance angiography (MRA).

MR angiography of run-off vessels

Abstract. Magnetic resonance angiography has taken a huge step forward since the introduction of contrast-enhanced MR angiography using gadolinium chelates. The more conventional MR angiographic techniques, such as time-of-flight and phase-contrast MR angiography, have been ousted by contrast-enhanced MR angiography in most vascular areas. However, in imaging the lower extremities, the major obstacle is the length of the vascular tree. In order to cover the entire peripheral vasculature, at least two to three fields of view are required. Using contrast-enhanced MR angiography, the best results are obtained if the vessels of interest are imaged during passage of a bolus of contrast material. Vessel-to-background contrast in subsequent acquisitions using subsequent injections of contrast material is hampered by recirculation and leakage of previously injected gadolinium, enhancing both the venous system and surrounding tissue. To overcome this problem several research groups have come up with various solutions. The three main strategies employed can be classified as either bolus catch, bolus chase, or bolus track techniques. The purpose of this article is to explain working mechanisms of the three bolus imaging strategies for imaging both inflow and outflow vessels of the lower extremities, to show their advantages and disadvantages, and to review results described in the literature in imaging patients using these techniques.

Comparison of treatment plans for peripheral arterial disease made with multi-station contrast medium-enhanced magnetic resonance angiography and duplex ultrasound scanning

OBJECTIVE This study was undertaken to investigate the effects of substituting multi-station total outflow contrast medium-enhanced magnetic resonance angiography (CE-MRA) for color duplex ultrasound (US) scanning on treatment planning in the diagnostic workup of patients with suspected or known peripheral arterial occlusive disease. Patients and methods One hundred consecutive patients referred because of suspected or proved peripheral arterial occlusive disease to a University Hospital underwent both aortoiliac duplex US scanning and multi-station total outflow CE-MRA. For 73 of these patients (57% men; mean age, 62 years) treatment or treatment plans could be retraced. Eighteen patients also underwent femoro-popliteal duplex US scanning. Three experienced vascular surgeons retrospectively formulated two sets of treatment plans based on standardized clinical parameters and either duplex US scanning or CE-MRA. The main outcome measure was proportion of patients for whom the treatment plan matched actual treatment without additional use of intra-arterial digital subtraction angiography. Actual treatment, based on all available information, including results of duplex US scanning, CE-MRA, and any other diagnostic tests, served as the standard of reference. RESULTS Duplex US scanning provided enough information for treatment planning in 46, 45, and 53 patients versus 67, 68, and 66 patients when CE-MRA was used (surgeons 1, 2, and 3, respectively; surgeons 1 and 2, P <.001; surgeon 3, P =.007). Treatment plans based on duplex US scanning exactly matched actual treatment in 37 of 73 patients (51%; surgeon 1), 36 of 73 patients (49%; surgeon 2), and 46 of 73 patients (63%; surgeon 3). Treatment plans based on CE-MRA exactly matched actual treatment in 56 of 73 patients (77%; surgeon 1), 55 of 73 patients (75%; surgeon 2), and 51 of 73 patients (70%; surgeon 3). Positive predictive value and negative predictive value of duplex US scanning as measures of ability to discriminate between surgical and nonsurgical treatment were 0 of 0 (undefined) and 43 of 46 (93%), 1 of 2 (50%) and 40 of 43 (93%), and 5 of 5 (100%) and 44 of 48 (92%) for surgeons 1, 2, and 3, respectively. For CE-MRA, positive and negative predictive values were 11 of 13 (85%) and 50 of 54 (93%), 10 of 12 (83%) and 51 of 56 (91%), and 8 of 13 (62%) and 48 of 53 (91%), respectively, for surgeons 1, 2, and 3. CONCLUSION Compared with aorto-iliac and femoro-popliteal duplex US scanning, multi-station total outflow CE-MRA is more effective for treatment planning in most patients with known or suspected peripheral arterial occlusive disease.

Need for background suppression in contrast-enhanced peripheral magnetic resonance angiography

To determine if background suppression is beneficial for peripheral magnetic resonance angiography (pMRA), nonsubtracted, subtracted, and fat‐saturated contrast‐enhanced (CE) pMRA were compared in 10 patients with peripheral arterial disease. Signal‐to‐noise ratios (SNRs) and contrast‐to‐noise ratios (CNRs), as well as venous enhancement and subjective interpretability, were determined in a station‐by‐station fashion for each technique. In three patients X‐ray angiography was available as a standard of reference. SNRs and CNRs were significantly higher for fat‐saturated vs. the other two techniques (P = 0.005). Subjective interpretability was best for subtracted data sets in the lower‐leg station. In the iliac station, fat‐saturated data sets were considered to have significantly lower interpretability than subtracted data sets. Venous enhancement occurred significantly more often in the lower‐leg station with the fat‐saturated technique. The value of subtraction depends on the hardware one has available and is a useful tool if dedicated surface coils are used. Background suppression by means of magnitude subtraction leads to the best lower‐leg image interpretability. Care must be taken to avoid venous enhancement in the lower‐leg station when using fat saturation. J. Magn. Reson. Imaging 2001;14:724–733.