Resolution improvement in thick‐slab magnetic resonance digital subtraction angiography using SENSE at 3T

Abstract

Purpose:To evaluate the use of parallel imaging (sensitivity encoding [SENSE]) to improve spatial resolution and achieve sub-second temporal resolution in fluoroscopic contrast-enhanced, magnetic resonance digital subtraction angiography (MR-DSA). Materials and Methods:A MR-DSA sequence was optimized on a 3-T scanner with respect to sampling bandwidth and SENSE acceleration factor subject to the constraints of half-second acquisition time and 0.6 ϫ 1.2 mm in-plane resolution. MR-DSA with and without SENSE acceleration was then evaluated in patients with arterio-venous malformations (AVMs).Results: Consistent with previously reported results and theory, SENSE factors greater than two and increasing sampling bandwidth both led to increasing image noise. Compared to lower resolution MR-DSA images with similar temporal resolution, the SENSE accelerated sequence provided better spatial resolution without notable changes in the contrast enhancement of the vascular territories of the AVMs but was hampered somewhat in the late venous phases by a reconstruction artifact.Conclusion: SENSE acceleration of MR-DSA by a factor of two allows improved temporal or spatial resolution without significant loss of image quality. Signal-to-noise degradation associated with higher SENSE acceleration factors are likely to necessitate other approaches to further improving resolution in MR-DSA. Clinically, SENSE accelerated MR-DSA improves the non-invasive pre-and postoperative depiction of AVM flow dynamics.

Arteriovenous Shunt Visualization in Arteriovenous Malformations with Arterial Spin-Labeling MR Imaging

“…Phase-contrast MR imaging has been used to measure blood flow in arteries feeding AVMs, but it is not adequate for comprehensive evaluation of AVM hemodynamics or effects on adjacent brain. 5,6 Undersampled back projection and keyhole imaging approaches and also parallel imaging methods [7][8][9][10][11][12] may provide the means for a favorable comparison with DSA to the point where it is possible to obtain complete evaluation of AVM vascular architecture as well as dynamic characteristics, including AV shunting and blood flow in adjacent brain, but current noninvasive imaging methods remain suboptimal. Even DSA is not capable of providing accurate quantitative assessment of blood flow or degree of shunt in an AVM, though there are objective indirect measures such as venous appearance time.…”

High Resolution Wall and Lumen MRI of the Middle Cerebral Arteries at 3 Tesla

“…High-field MR may be beneficial in the visualization of intracranial artery walls, which have submillimeter structures [10, 11]. The high signal-to-noise ratio and minimal scan duration offer great advantages in the clinical setting.…”

Cerebral Arteriovenous Malformation: Spetzler-Martin Classification at Subsecond-Temporal-Resolution Four-dimensional MR Angiography Compared with That at DSA

“…Furthermore, postprocessing potentials inherent to acquisition of a full 3D data set are no longer available by using these methods. Summers et al (37) described a technique of two-dimensional contrast-enhanced MR angiography that achieved subsecond temporal resolution at 3.0 T by using parallel imaging (ie, sensitivity encoding). We agree that parallel imaging and high-field-strength imaging seem to be a good combination to accelerate temporal resolution at contrast-enhanced MR angiography.…”

“…Two-dimensional single-thick-section techniques for time-resolved contrast-enhanced MR angiography have been reported to achieve high temporal resolution (34)(35)(36)(37)(38) at the expense of spatial resolution. Furthermore, postprocessing potentials inherent to acquisition of a full 3D data set are no longer available by using these methods.…”

“…Parallel imaging has proved to enable substantial improvement in temporal resolution, as well as spatial resolution, at contrast-enhanced MR angiography (37,(46)(47)(48)(49)(50). Although parallel imaging acceleration factors are limited at 1.5 T because of signal-to-noise limitations, this is less of an issue at high field strengths, where parallel imaging acceleration factors of more than eight have been successfully implemented (51).…”