Ohashi Toshio, Naganawa Shinji, Kanou Mai, Ikeda Mitsuru
Department of Radiology, Kamiiida Daiichi General Hospital.
Magn Reson Med Sci. 2017 Apr 10;16(2):123-128. doi: 10.2463/mrms.mp.2016-0031. Epub 2016 Jul 13.
Diffusion-weighted imaging (DWI) using readout-segmented EPI (rs-EPI) can minimize distortion and blurring artifacts; however, we sometimes encounter cerebrospinal fluid (CSF) pulsation artifacts on apparent diffusion coefficient (ADC) maps, especially when the number of readout segments (NRS) is increased. The purpose of this study was to evaluate the effect of the NRS on the CSF pulsation artifacts in the ADC maps of healthy volunteers.
In 10 healthy volunteers, we obtained DWI from rs-EPI with a b-value of 0 and 1000 s/mm. The NRS was set to 5, 7, or 9. An ADC map was generated from the trace image and the b = 0 image. Each scan was performed twice. A circular region of interest (ROI) was drawn in the pons and bilateral thalami. The standard deviation (SD) of the ROI was measured to assess the artifacts. Bilateral SD values were averaged for the ROIs in the thalami. The SD values from two successive scans of each NRS were averaged for the pons and thalami, respectively. For the qualitative analysis, the CSF pulsation artifacts on each ADC map were graded by two observers independently as 0, no artifact; 1, mild artifact; 2, moderate artifact; or 3, severe artifact.
In the quantitative analysis, the SD values tend to increase with the increasing of NRS in both thalami and pons; however, the difference in the SD values from each NRS did not reach a statistically significant level. In the qualitative analysis, there was a statistically significant difference in the scores between 5 and 9 segments and between 7 and 9 segments with both the observers, respectively (P < 0.05).
The CSF pulsation artifacts on ADC maps obtained with rs-EPI are affected by the NRS.
采用读出分段回波平面成像（rs-EPI）的扩散加权成像（DWI）可将畸变和模糊伪影降至最低；然而，我们有时会在表观扩散系数（ADC）图上遇到脑脊液（CSF）搏动伪影，尤其是当读出分段数（NRS）增加时。本研究的目的是评估NRS对健康志愿者ADC图中CSF搏动伪影的影响。
对10名健康志愿者，我们采用b值为0和1000 s/mm的rs-EPI获得DWI。NRS设置为5、7或9。从迹图像和b = 0图像生成ADC图。每次扫描进行两次。在脑桥和双侧丘脑绘制圆形感兴趣区（ROI）。测量ROI的标准差（SD）以评估伪影。丘脑ROI的双侧SD值进行平均。每个NRS的两次连续扫描的SD值分别对脑桥和丘脑进行平均。对于定性分析，两名观察者分别对每个ADC图上的CSF搏动伪影进行分级，分为0级，无伪影；1级，轻度伪影；2级，中度伪影；或3级，重度伪影。
在定量分析中，丘脑和脑桥的SD值均倾向于随NRS的增加而增加；然而，每个NRS的SD值差异未达到统计学显著水平。在定性分析中，两位观察者分别在5段和9段之间以及7段和9段之间的评分存在统计学显著差异（P < 0.05）。
rs-EPI获得的ADC图上的CSF搏动伪影受NRS影响。
