Combined Low-Dose Contrast-Enhanced MR Angiography and Perfusion for Acute Ischemic Stroke at 3T: A More Efficient Stroke Protocol

Abstract

BACKGROUND AND PURPOSE There is need to improve image acquisition speed for MR imaging in evaluation of patients with acute ischemic stroke. The purpose of this study was to evaluate the feasibility of a 3T MR stroke protocol that combines low-dose contrast-enhanced MRA and dynamic susceptibility contrast perfusion, without additional contrast. METHODS Thirty patients with acute stroke who underwent 3T MR imaging followed by DSA were retrospectively enrolled. TOF-MRA of the neck and brain and 3D contrast-enhanced MRA of the craniocervical arteries were obtained. A total of 0.1 mmol/kg of gadolinium was used for both contrast-enhanced MRA (0.05 mmol/kg) and dynamic susceptibility contrast perfusion (0.05 mmol/kg) (referred to as half-dose). An age-matched control stroke population underwent TOF-MRA and full-dose (0.1 mmol/kg) dynamic susceptibility contrast perfusion. The cervicocranial arteries were divided into 25 segments. Degree of arterial stenosis on contrast-enhanced MRA and TOF-MRA was compared with DSA. Time-to-maximum maps (>6 seconds) were evaluated for image quality and hypoperfusion. Quantitative analysis of arterial input function curves, SNR, and maximum T2* effects were compared between half- and full-dose groups. RESULTS The intermodality agreements (k) for arterial stenosis were 0.89 for DSA/contrast-enhanced MRA and 0.63 for DSA/TOF-MRA. Detection specificity of >50% arterial stenosis was lower for TOF-MRA (89%) versus contrast-enhanced MRA (97%) as the result of overestimation of 10% (39/410) of segments by TOF-MRA. The DWI-perfusion mismatch was identified in both groups with high interobserver agreement (r = 1). There was no significant difference between full width at half maximum of the arterial input function curves (P = .14) or the SNR values (0.6) between the half-dose and full-dose groups. CONCLUSIONS In patients with acute stroke, combined low-dose contrast-enhanced MRA and dynamic susceptibility contrast perfusion at 3T is feasible and results in significant scan time and contrast dose reductions.

Six-Minute Magnetic Resonance Imaging Protocol for Evaluation of Acute Ischemic Stroke

“…23,24 Finally, our results suggest that combined CE-MRA and DSC perfusion is feasible, resulting in significant reduction in scan time as previously suggested. 28,29 We used a modified 2-phase contrast injection scheme 29 to perform both CE-MRA and DSC perfusion imaging, without the need for additional contrast.…”

Validation of MRI Determination of the Penumbra by PET Measurements in Ischemic Stroke

“…Recently, several methods for improving the reliability of the assessment of perfusion with MRI methods were proposed (38)(39)(40), but they all need to be validated by quantitative measures. Therefore, PET-validated and -calibrated thresholds of the most predictive MRI perfusion maps must be implemented for optimal mismatch detection.…”

Comparison of extracranial artery stenosis and cerebral blood flow, assessed by quantitative magnetic resonance, using digital subtraction angiography as the reference standard

“…In the last few years, CE-MRA has become required simultaneously to the contrast used for DSC perfusion imaging. [19] With the introduction of new magnetic resonance technology, the speed and spatial resolution of CE-MRA have significantly improved. [25,26] …”

“…[17,18] Previous study has suggested that combining low-dose CE-MRA and dynamic susceptibility contrast (DSC) perfusion imaging is feasible in the evaluation without the need for additional contrast. [19] …”