FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

Abstract

Purpose:To estimate cerebral blood perfusion in areas of strong magnetic susceptibility changes with high spatial and temporal resolution using a flow-sensitive alternating inversion recovery (FAIR) arterial spin labeling (ASL) method. Materials and Methods:We implemented an ASL method that is capable of imaging perfusion in areas of high magnetic susceptibility changes by combining a FAIR spin preparation with a true fast imaging in steady precession (TrueFISP) data acquisition strategy. A TrueFISP readout sequence was applied especially in regions with magnetic field inhomogeneities and compared with corresponding FAIR measurements obtained with a standard echo-planar imaging (EPI) readout. Quantitative perfusion images were obtained at 1.5 Tesla (1.5T) from eight healthy volunteers (24 -42 years old) and one patient (23 years old). FAIRTrueFISP perfusion images were compared with FAIR echoplanar images. T1 maps, which are necessary for quantitative perfusion estimation, were obtained with inversion recovery (IR) TrueFISP and IR EPI. Additionally, high-resolution perfusion measurements were performed on four volunteers at 3T. Results:The two ASL perfusion imaging modalities yielded comparable diagnostic image quality in brain areas with low susceptibility differences at 1.5T. Cerebral perfusion of gray matter (GM) areas was 105.7 Ϯ 5.2 mL/100 g/minute for FAIR-TrueFISP and 88.8 Ϯ 14.6 mL/100 g/minute for FAIR-EPI at 1.5T, and 70.4 Ϯ 7.1 mL/100 g/minute for FAIR-TrueFISP and 63.5 Ϯ 6.9 mL/100 g/minute for FAIR-EPI at 3.0T. Higher perfusion values at 1.5T were due to more pronounced partial-volume effects from fast moving spins at lower spatial resolution. The FAIR-TrueFISP sequence showed no significant distortions and markedly reduced signal void artifacts in areas of high susceptibility changes (e.g., near brain-bone transitions and close to metallic clips) compared to FAIR-EPI. At 3T, highly resolved FAIR-TrueFISP perfusion images were acquired with an in-plane resolution of up to 1.3 mm.Conclusion: FAIR-TrueFISP allows for assessment of cerebral perfusion in areas of critically high susceptibility changes with conventional ASL methods.

Unenhanced Dynamic MR Angiography: High Spatial and Temporal Resolution by Using True FISP–based Spin Tagging with Alternating Radiofrequency

“…The technique is also inherently flow compensated, thereby minimizing sensitivity to fl ow artifacts ( 16 ). In addition, true FISP has relatively low sensitivity to susceptibility artifacts ( 17 ). The goal of our study was to present an unenhanced four-dimensional time-resolved dynamic MR angiography technique (true FISP) that is based on spin tagging with alternating radiofrequency (STAR), also called TrueSTAR ( 18 ).…”

Framingham Cardiovascular Risk Profile Correlates with Impaired Hippocampal and Cortical Vasoreactivity to Hypercapnia

“…Moreover, conventionally used 64 Â 64 echo-planar imaging matrix does not allow one to separate hippocampus from adjacent large vessels, including circle of Willis. To overcome these shortcomings, we used ASL based on true fast imaging in steady-precession (TrueFISP) sequence (Boss et al, 2007;Rusinek et al, 2010).…”

Renal Arterial Spin Labeling Magnetic Resonance Imaging

“…In this context, the use of phased array coils, which allow rapid imaging acquisitions [23], represents an advantage for ASL. Magnetic field inhomogeneities, which arise mostly at the interface between tissue types with different magnetic susceptibility, limit the choice of imaging techniques to classes that are less prone to susceptibility artifacts [24,25,26]. The use of dielectric pads, dedicated RF shimming, parallel RF transmission techniques or the reduction of the static field strength should be considered for mitigation of dielectric artifacts [27].…”