HIGH RES DYNAMIC-SUSCEPTIBILITY CONTRAST PWI USING MULTI-ECHO PARALLEL EPI

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。简介：在基于动态敏感性对比的MRI （DSC-MRI）中，在血管内示踪剂第一次通过时获得时间序列，由此可以估计脑血容量（CBV）。用动脉输入函数（AIF）进行像素反卷积得到脑血流量（CBF）和平均传递时间（MTT）图。DSC-MRI多回波（ME）方法的好处是：1)？R2*可以不受t1增强干扰地测量；2)不需要丸前基线信号；3)可根据第一回波自动选择动脉输入功能；4)如果动态范围使用？所有回波的R2*太小。与平行成像（PI）相结合，可以获得较高的空间和时间分辨率。PI还减少了与EPI相关的图像伪影。这种ME与PI的结合称为PERMEATE。方法和讨论：所有扫描均在1.5 T Signa扫描仪（GE Medical Systems）上进行，该扫描仪带有8单元头部阵列。PI取还原因子R =3, R =4。PERMEATE参数为：15片（5 mm厚，1 mm间隙），24 cm FOV， 96¿96分辨率，TE = 13.8, 31.6, 49.4 ms （R=3）和TE = 12.4, 27.3, 42.2, 57.1 ms (R= 4)， 100次重复，TR = 1225 ms，带宽为¿100 kHz，翻转角度= 70。回波数等于r，采用GRAPPA算法进行重建。单次给药0.1 mmol/kg Gd-DTPA，以4 ml/s的速度给药，随后冲洗20 ml生理盐水。灌注图由块循环SVD计算，用于示踪剂到达时间不敏感的反卷积（PSVD= 10%），使用从第一次回波中自动选择的AIF。脑灰质和脑白质之间的CBF/CBV比率通过手动绘制的ROI内的值估计。灌注图能很好地描绘灰质和白质。AIF表明，第一次回波具有最佳的AIF选择动态范围，可用于进一步的CBV/CBF分析。2名受试者的灰质/白质比值与先前报道的值吻合良好。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: In dynamic-susceptibility contrast-based MRI (DSC-MRI), time series are acquired during the first pass of an intravascular tracer from which it is possible to estimate cerebral blood volume (CBV). Pixelwise deconvolution with an arterial input function (AIF) yields maps of cerebral blood flow (CBF) and mean transit time (MTT). The benefits of a multi-echo (ME) approach for DSC-MRI are: 1) ?R2*can be measured undisturbed from T1enhancement; 2) no pre-bolus baseline signal is required; 3) automatic selection of arterial input function can be based on the first echo; 4) analysis can be limited to the first echo(es) if the dynamic range using ?R2* of all echoes is too small. In combination with parallel imaging (PI), a high spatial and temporal resolution can be achieved. PI also reduces image artifacts related to EPI. This combination of ME with PI, is termed PERMEATE. Methods and Discussion: All scans were performed on a 1.5 T Signa scanner (GE Medical Systems) with an 8-element head array. PI was performed with reduction factors R =3 and R =4. The PERMEATE parameters were: 15 slices (5-mm thick, 1-mm gap), 24-cm FOV, 96 ¿ 96 resolution, TE = 13.8, 31.6, 49.4 ms (R=3) and TE = 12.4, 27.3, 42.2, 57.1 ms (R =4), 100 repetitions with TR = 1225 ms, ¿100 kHz bandwidth, and flip angle = 70. The number of echoes equals R. A GRAPPA algorithm was used for reconstruction. A single dose of 0.1 mmol/kg Gd-DTPA was administered at 4 ml/s followed by 20-ml saline flush. Perfusion maps were calculated by a block-circulant SVD for tracer arrival timing-insensitive deconvolution (PSVD= 10%) using an automatically selected AIF from the first echo. The ratio of CBF/CBV between gray and white matter was estimated by values within a manually-drawn ROI. Gray and white matter could be well delineated in the perfusion maps. The AIFs demonstrate that the first echo has the best dynamic range for AIF selection and was used for further CBV/CBF analysis. Gray/white matter ratios of 2 subjects were in good agreement with previously reported values.