Quantitative assessment of cerebral venous blood T2 in mouse at 11.7T: Implementation, optimization, and age effect

PurposeTo develop a non-contrast-agent MRI technique to quantify cerebral venous T-2 in mice. MethodsWe implemented and optimized a T-2-relaxation-under-spin-tagging (TRUST) sequence on an 11.7 Tesla animal imaging system. A flow-sensitive-alternating-inversion-recovery (FAIR) module was used to generate control and label images, pair-wise subtraction of which yielded blood signals. Then, a T-2-preparation module was applied to produce T-2-weighted images, from which blood T-2 was quantified. We conducted a series of technical studies to optimize the imaging slice position, inversion slab thickness, post-labeling delay (PLD), and repetition time. We also performed three physiological studies to examine the venous T-2 dependence on hyperoxia (N=4), anesthesia (N=3), and brain aging (N=5). ResultsOur technical studies suggested that, for efficient data acquisition with minimal bias in estimated T-2, a preferred TRUST protocol was to place the imaging slice at the confluence of sagittal sinuses with an inversion-slab thickness of 2.5-mm, a PLD of 1000 ms and a repetition time of 3.5 s. Venous T-2 values under normoxia and hyperoxia (inhaling pure oxygen) were 26.91.7 and 32.3 +/- 2.2 ms, respectively. Moreover, standard isoflurane anesthesia resulted in a higher venous T-2 compared with dexmedetomidine anesthesia (N=3; P=0.01) which is more commonly used in animal functional MRI studies to preserve brain function. Venous T-2 exhibited a decrease with age (N=5; P<0.001). ConclusionWe have developed and optimized a noninvasive method to quantify cerebral venous blood T-2 in mouse at 11.7T. This method may prove useful in studies of brain physiology and pathophysiology in animal models. Magn Reson Med 80:521-528, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.