Sarma M K, Nagarajan R, Macey P M, Kumar R, Villablanca J P, Furuyama J, Thomas M A
From the Departments of Radiological Sciences (M.K.S., R.N., R.K., J.P.V., J.F., M.A.T.).
School of Nursing (P.M.M.), University of California, Los Angeles, Los Angeles, California.
AJNR Am J Neuroradiol. 2014 Jun;35(6 Suppl):S81-9. doi: 10.3174/ajnr.A3846. Epub 2014 Feb 6.
Echo-planar J-resolved spectroscopic imaging is a fast spectroscopic technique to record the biochemical information in multiple regions of the brain, but for clinical applications, time is still a constraint. Investigations of neural injury in obstructive sleep apnea have revealed structural changes in the brain, but determining the neurochemical changes requires more detailed measurements across multiple brain regions, demonstrating a need for faster echo-planar J-resolved spectroscopic imaging. Hence, we have extended the compressed sensing reconstruction of prospectively undersampled 4D echo-planar J-resolved spectroscopic imaging to investigate metabolic changes in multiple brain locations of patients with obstructive sleep apnea and healthy controls.
Nonuniform undersampling was imposed along 1 spatial and 1 spectral dimension of 4D echo-planar J-resolved spectroscopic imaging, and test-retest reliability of the compressed sensing reconstruction of the nonuniform undersampling data was tested by using a brain phantom. In addition, 9 patients with obstructive sleep apnea and 11 healthy controls were investigated by using a 3T MR imaging/MR spectroscopy scanner.
Significantly reduced metabolite differences were observed between patients with obstructive sleep apnea and healthy controls in multiple brain regions: NAA/Cr in the left hippocampus; total Cho/Cr and Glx/Cr in the right hippocampus; total NAA/Cr, taurine/Cr, scyllo-Inositol/Cr, phosphocholine/Cr, and total Cho/Cr in the occipital gray matter; total NAA/Cr and NAA/Cr in the medial frontal white matter; and taurine/Cr and total Cho/Cr in the left frontal white matter regions.
The 4D echo-planar J-resolved spectroscopic imaging technique using the nonuniform undersampling-based acquisition and compressed sensing reconstruction in patients with obstructive sleep apnea and healthy brain is feasible in a clinically suitable time. In addition to brain metabolite changes previously reported by 1D MR spectroscopy, our results show changes of additional metabolites in patients with obstructive sleep apnea compared with healthy controls.
回波平面J分辨波谱成像（Echo-planar J-resolved spectroscopic imaging）是一种用于记录脑内多个区域生化信息的快速波谱技术，但对于临床应用而言，时间仍是一个限制因素。对阻塞性睡眠呼吸暂停患者神经损伤的研究已揭示了脑结构的变化，但要确定神经化学变化则需要对多个脑区进行更详细的测量，这表明需要更快的回波平面J分辨波谱成像。因此，我们扩展了前瞻性欠采样4D回波平面J分辨波谱成像的压缩感知重建技术，以研究阻塞性睡眠呼吸暂停患者和健康对照者多个脑区的代谢变化。
在4D回波平面J分辨波谱成像的1个空间维度和1个波谱维度上进行非均匀欠采样，并使用脑部体模测试非均匀欠采样数据的压缩感知重建的重测信度。此外，使用3T磁共振成像/磁共振波谱扫描仪对9例阻塞性睡眠呼吸暂停患者和11名健康对照者进行了研究。
在多个脑区观察到阻塞性睡眠呼吸暂停患者与健康对照者之间代谢物差异显著降低：左侧海马体中的NAA/Cr；右侧海马体中的总Cho/Cr和Glx/Cr；枕叶灰质中的总NAA/Cr、牛磺酸/Cr、异肌醇/Cr、磷酸胆碱/Cr和总Cho/Cr；内侧额叶白质中的总NAA/Cr和NAA/Cr；以及左侧额叶白质区域中的牛磺酸/Cr和总Cho/Cr。
在阻塞性睡眠呼吸暂停患者和健康对照者中，使用基于非均匀欠采样采集和压缩感知重建的4D回波平面J分辨波谱成像技术在临床合适的时间内是可行的。除了先前1D磁共振波谱报告的脑代谢物变化外，我们的结果显示与健康对照相比，阻塞性睡眠呼吸暂停患者的其他代谢物也发生了变化。
