3T pulmonary MR angiography

Abstract

Purpose: MR angiography has recently benefited from higher signal at high field strength, and developments in parallel imaging, coils, and shared k-space techniques for increased acquisition speed. Still, pulmonary MR angiography is challenging at high field strength due to the geometry of the anatomy and the presence of air-vessel interfaces. Large coverage is needed with high resolution within acceptable breath hold time. Materials and Methods:Contrast-enhanced pulmonary MRA was performed in 8 subjects on a Philips Achieva 3T MR system, using a 6-channel cardiac coil. Gadolinium-BOPTA (Multihance, Bracco) contrast dose of 0.1mmol/kg was injected at 2ml/s rate. A test bolus of 1 cc of contrast was used for acquisition timing. A 3D single-shot T1 gradient echo sequence was used with TR/TE 5.4/1.47ms, partial-echo, FA 30°, 1308Hz/px bandwidth, 350mm FOV, 352×165 matrix, elliptical centric order, SENSE x2. Acquired voxel size was 1×2x2.8mm3, reconstructed 0.6×0.6×1.4mm3, and scan duration 22 seconds. Results: Contrast-enhanced MRA's were performed successfully (fig 1). Mean SNR of 324.9±37.8 was measured without SENSE, and 192.3±29 with SENSE factor 2 in a mineral oil phantom. In the enhanced pulmonary artery mean SNR was 59.87±20.83, and relative enhancement ratio was 24.33±7.25. Conclusion: The main challenges of pulmonary MRA at 3T are faster T2* decay, increased susceptibility at the vessel/air interface and SAR limitations. This study shows the feasibility of 3T pulmonary MRA with good image quality, SNR and relative contrast enhancement with limited SENSE factor.