Fast contrast-enhanced 4D MRA and 4D flow MRI using constrained reconstruction (HYPRFlow): potential applications for brain arteriovenous malformations.

W Chang,P Turski,Y Wu,M Edjlali,M Loecher,K Johnson,C Oppenheim,C Mistretta,O Wieben,P Roca,B Aagaard-Kienitz,D Niemann,J Hald

doi:10.3174/ajnr.a4245

Abstract

HYPRFlow is a novel imaging strategy that provides fast, high-resolution contrast-enhanced time-resolved images and measurement of the velocity of the entire cerebrovascular system. Our hypothesis was that the images obtained with this strategy are of adequate diagnostic image quality to delineate the major components of AVMs. HYPRFlow and 3D TOF scans were obtained in 21 patients with AVMs with correlative DSA examinations in 14 patients. The examinations were scored for image quality and graded by using the Spetzler-Martin criteria. Mean arterial transit time and overlap integrals were calculated from the dynamic image data. Volume flow rates in normal arteries and AVM feeding arteries were measured from the phase contrast data. HYPRFlow was equivalent to 3D-TOF in delineating normal arterial anatomy, arterial feeders, and nidus size and was concordant with DSA for AVM grading and venous drainage in 13 of the 14 examinations. Mean arterial transit time on the AVM side was 0.49 seconds, and on the normal contralateral side, 2.53 seconds with P < .001. Across all 21 subjects, the mean arterial volume flow rate in the M1 segment ipsilateral to the AVM was 4.07 ± 3.04 mL/s; on the contralateral M1 segment, it was 2.09 ± 0.64 mL/s. The mean volume flow rate in the largest feeding artery to the AVM was 3.86 ± 2.74 mL/s. HYPRFlow provides an alternative approach to the MRA evaluation of AVMs, with the advantages of increased coverage, 0.75-second temporal resolution, 0.68-mm isotropic spatial resolution, and quantitative measurement of flow in 6 minutes.

Highlights

BACKGROUND AND PURPOSEHYPRFlow is a novel imaging strategy that provides fast, high-resolution contrast-enhanced timeresolved images and measurement of the velocity of the entire cerebrovascular system
Many MR angiography techniques have been used for the imaging of arteriovenous malformations with various levels of efficacy. 3D-TOF imaging is capable of imaging arterial components of AVMs with high spatial resolution.[1,2]
Recent progress in constrained reconstruction techniques has suggested that it may be possible to overcome many of the limitations in temporal resolution, spatial resolution, and signal-tonoise ratio encountered by using conventional reconstruction schemes for time-resolved contrast-enhanced MRA

Summary

Methods

HYPRFlow and 3D TOF scans were obtained in 21 patients with AVMs with correlative DSA examinations in 14 patients. Radial imaging eliminates the time-consuming phase-encoding used in Cartesian acquisitions. Fast serial 3D radial scans are obtained of the entire brain during the passage of a contrast agent by using only a small number of readouts. This dynamic acquisition is termed CE-VIPR (contract-enhanced time resolved vastly undersampled isotropic radial projection reconstruction). IC, where It is a reconstructed timeframe image from the dynamic scan, IC is the phase-contrast constraint (PC-VIPR), and K is a 10 ϫ 10 ϫ 10 (pixels) convolution kernel. The strategy of combining rapid contrast-enhanced serial 3D radial imaging (CE-VIPR), phasecontrast radial imaging (PC-VIPR), and highly constrained projection reconstruction (HYPR LR) is termed “HYPRFlow” (Fig 1).[12]

Results

Discussion

Conclusion