Routine clinical brain MRI sequences for use at 3.0 Tesla

Abstract

Purpose: To establish image parameters for some routine clinical brain MRI pulse sequences at 3.0 T with the goal of maintaining, as much as possible, the well-characterized 1.5-T image contrast characteristics for daily clinical diagnosis, while benefiting from the increased signal to noise at higher field. Materials and Methods:A total of 10 healthy subjects were scanned on 1.5-T and 3.0-T systems for T 1 and T 2 relaxation time measurements of major gray and white matter structures. The relaxation times were subsequently used to determine 3.0-T acquisition parameters for spin-echo (SE), T 1 -weighted, fast spin echo (FSE) or turbo spin echo (TSE), T 2 -weighted, and fluid-attenuated inversion recovery (FLAIR) pulse sequences that give image characteristics comparable to 1.5 T, to facilitate routine clinical diagnostics. Application of the routine clinical sequences was performed in 10 subjects, five normal subjects and five patients with various pathologies.Results: T 1 and T 2 relaxation times were, respectively, 14% to 30% longer and 12% to 19% shorter at 3.0 T when compared to the values at 1.5 T, depending on the region evaluated. When using appropriate parameters, routine clinical images acquired at 3.0 T showed similar image characteristics to those obtained at 1.5 T, but with higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), which can be used to reduce the number of averages and scan times. Recommended imaging parameters for these sequences are provided. Conclusion:When parameters are adjusted for changes in relaxation rates, routine clinical scans at 3.0 T can provide similar image appearance as 1.5 T, but with superior image quality and/or increased speed.

Visualization of Altered Neurovascular Coupling in Chronic Stroke Patients using Multimodal Functional MRI

“…where 1=T 1;app ¼ 1=T 1;GM þf =l, c ¼ðf =lÞð1=T 1;app À 1=T 1;a Þ À1 , f is the CBF (mL per gram per milliseconds), M 0 is the equilibrium magnetization of blood water, aE1 is the inversion efficiency, t a E600 milliseconds and t d E1,500 milliseconds are the times for the leading and trailing edge of the bolus in motor cortex, respectively (Gallichan and Jezzard, 2009;MacIntosh et al, 2010a), T 1,GM E1,200 milliseconds (Lu et al, 2005) and T 1,a E1,600 milliseconds (Lu et al, 2004) are the tissue and arterial blood water T 1 , respectively, and lE0.9 mL blood/g brain is the whole-brain blood/tissue water partition coefficient (Herscovitch and Raichle, 1985). Upon stimulation, the CBF will increase, and the ATT has been shown to reduce by approximately an equal amount (Gonzalez-At et al, 2000).…”

No advantage of time-of-flight magnetic resonance angiography at 3 Tesla compared to 1.5 Tesla in the follow-up after endovascular treatment of cerebral aneurysms

“…The study was performed against the background of an increasing number of 3 T MR scanners used in routine diagnostic imaging worldwide [10]. Therefore, we used optimized but comparable diagnostic sequences that should be easily reproducible at any MR scanner.…”

A Functional Magnetic Resonance Imaging Technique Based on Nulling Extravascular Gray Matter Signal

“…Water proton densities (C) of arteriole, capillary, and venule blood were all assumed to be 0.87 (Lu et al, 2002) and water proton densities of GM and CSF were estimated as 0.89 and 1, respectively (Lu et al, 2002). T 1 values were set to be equal at rest and under activation and taken to be 1,122 ms for GM, 3,817 ms for CSF, 1,627 ms for arteriole, capillary, and venule blood, respectively (Lu et al, 2004a(Lu et al, , 2005aDonahue et al, 2006a).…”

“…A spatially nonselective IR pulse was applied with TI set for nulling GM and blood signal, respectively. Typical GM T 1 = 1,122 ms (Lu et al, 2005a) and blood T 1 = 1,627 ms (Lu et al, 2004a) at 3T were adopted for the determination of appropriate TI values. The corresponding TIs for TR = 2,000, 3,000, 4,000, and 5,000 ms were 603, 703, 746, and 765 ms for GMN, and 710, 889, 994 and 1,054 ms for VASO, respectively.…”