Use of a three-station phased array coil to improve peripheral contrast-enhanced magnetic resonance angiography

Abstract

Purpose: To explore the imaging capabilities of a new commercially available, three-station, 129-cm long, 12-element phased array coil for contrast-enhanced magnetic resonance angiography (CE-MRA) in patients with symptomatic peripheral arterial occlusive disease.

Materials and methods: Nineteen patients, referred for peripheral CE-MRA, were evaluated using the new three-station coil. For each station four coil elements (two anterior and two posterior to the patient) were used. The expected improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were used to improve spatial resolution and increase anatomic coverage for the distal two stations compared to our previous protocol. Images obtained in the 19 patients imaged with the new coil were compared to those of the last 19 patients scanned without the use of the new coil. Differences in image quality before vs. after the availability of the new coil were compared in terms of SNR and CNR, subjective interpretability score (SIS), degree of venous enhancement, and anatomic coverage. Images were interpreted by two experienced observers, blinded for imaging technique and each other's results.

Results: Use of the coil enabled acquisition of high resolution peripheral vasculature images in all cases and allowed for substantially smaller voxel sizes (thighs: 5.3 vs. 8.4 mm(3) [-37%]; legs: 1.8 vs. 8.0 mm3 [-78%]) and much shorter acquisition durations in the aortoiliac and thigh stations (aortoiliac: 16 vs. 27 seconds [-41%]; thighs: 11 vs. 23 seconds [-52%]). Acquisition duration in the leg station was prolonged (68 vs. 29 seconds [+134%]). SNR and CNR were significantly higher only in the aortoiliac station using the three-station coil (both: P < 0.001). There were no significant differences in SIS for the aortoiliac and thigh stations (aortoiliac station: observer 1: P = 0.16, observer 2: P = 0.19; thigh station: both observers: P = 0.27). Images acquired with the new coil had significantly higher SIS for the leg station (both observers: P = 0.004). There were no significant differences in venous enhancement between the two protocols for any of the stations (all P > 0.11). In 12/12 (100%) requested cases the entire pedal arch was depicted using the new coil, whereas this was not possible with the old protocol.

Conclusion: The new three-station dedicated peripheral vascular coil allows for much higher resolution imaging in the thigh and leg stations with greater anatomic coverage and substantially improves peripheral MRA quality of the lower leg vasculature.