Rapid Velocity-Encoded Cine Imaging with Turbo-BRISK

Abstract

Velocity-encoded cine (VEC) imaging is potentially an important clinical diagnostic technique for cardiovascular diseases. Advances in gradient technology combined with segmentation approaches have made possible breathhold VEC imaging, allowing data to be obtained free of respiratory artifacts. However, when using conventional segmentation approaches, spatial and temporal resolutions are typically compromised to accommodate short breathhold times. Here we apply a sparse sampling technique, turbo-BRISK (i.e., segmented block regional interpolation scheme for k-space) to VEC imaging, allowing increased spatial and temporal resolution to be obtained in a short breathhold period. BRISK is a sparse sampling technique with interpolation used to generate unsampled data. BRISK was implemented to reduce the scan time by 70% compared with a conventional scan. Further, turbo-BRISK scans, using segmentation factors up to 5, reduce the scan time by up to 94%. Phantom and in vivo results are presented that demonstrate the accuracy of turbo-BRISK VEC imaging. In vitro validation is performed using conventional magnetic resonance VEC. Pulsatile centerline flow velocity measurements obtained with turbo-BRISK acquisitions were correlated with conventional magnetic resonance imaging measurements and achieved r values of 0.99 +/- 0.004 (mean +/- SD) with stroke volumes agreeing to within 4%. A potential limitation of BRISK is reduced accuracy for rapidly varying velocity profiles. We present low- and high-resolution data sets to illustrate the resolution dependence of this phenomenon and demonstrate that at conventional resolutions, turbo-BRISK can accurately represent rapid velocity changes. In vivo results indicate that centerline velocity waveforms in the descending aorta correlate well with conventional measurements with an average r value of 0.98 +/- 0.01.

Numerical simulation of in vitro pulsatile flow and its study using FRISK, a rapid phase contrast technique

“…In the BRISK reconstruction strategy, the sparsely sampled k‐space lines are interpolated to generate k‐space lines at intermediate points between sampled positions (11). The BRISK and turbo BRISK results compared well with conventional PC‐MR and laser Doppler velocity measurements in phantom studies (12, 13). Thompson et al (14) used data acquisition sequences similar to BRISK to investigate intracardiac pressure differences both in phantoms and in a canine model by measuring in‐plane velocities, and found excellent agreement between the transducer and PC‐MR results in all studies.…”

Numerical and experimental study of a novel phase contrast magnetic resonance (PC‐MR) imaging technique: Sparse interleaved referencing PC‐MR imaging

“…However, due to doubling the temporal resolution in systole (64 ms), the Sparse Interleaved Referencing PC-MR data maintains high fidelity, even when the VPS is set as high as 8 (Peak velocity underestimation: 16.0% versus 1.7%). This aspect of Sparse Interleaved Referencing PC-MR can be readily combined with FRISK, a fast imaging technique that can at least halve the scan time with comparable accuracy compared with Con PC-MR, to realize breathhold data sampling for cardiovascular PC-MR acquisitions with high fidelity, where breath hold data acquisition is preferred to eliminate respiratory artifacts (24,25).…”

Extension of Rapid Phase-Contrast Magnetic Resonance Imaging Using BRISK in Multidirectional Flow

“…1,2,6 One of the aims of the CFD model in this study was to simulate the complicated low magnitude high temporal/spatial gradient velocities associated with circumferential velocities and attempt to define a data acquisition sequence to improve the calculation of such structures that are frequently associated with stenosis, aneurysms, or other vascular abnormalities. The BRISK-CON-VPS method did not provide significant improvement in the representation of these velocities but has provided insights to solve this problem.…”

“…When applied to the acquisition of PCMRI datasets, BRISK and segmented BRISK (BRISK-VPS) results compared well with conventional PCMRI and with Laser Doppler Velocity measurements in phantom studies. 1,2,5,6 The biggest limitation associated with BRISK-VPS is the need for data interpolation during post-processing, which adds overhead to the scan time and requires specialized modifications to scanner reconstruction software, thus making it unsuitable for incorporation in real-time imaging applications and limiting its widespread use on commercial scanners.…”