3T高清RS-EPI DWI与SS-EPI DWI序列诊断中耳胆脂瘤的效果比较

目的比较用高清读出分段平面回波-弥散加权成像(readout-segmented-echo-planar imaging-diffusion-weighted imaging, RS-EPI DWI)与单激发回波平面-弥散加权成像(single-shot echo-planar imaging-diffusion-weighted imaging, SS-EPI DWI)技术检测中耳胆脂瘤中的效果。方法 21例临床诊断中耳胆脂瘤和7例慢性化脓性中耳炎阴性对照用于检验RS-EPI DWI序列MRI检测胆脂瘤的能力。术中根据经验判断是否有胆脂瘤,并送病理检测。每位患者分别采用T2加权快速自旋回波(T2-weighted turbo spin echo, T2W-TSE)、RS-EPI DWI和单激发回波平面-弥散加权成像(single-shot echo-planar imaging-diffusion-weighted imaging, SS-EPI DWI)序列行MRI检查。采用ImageJ软件的图像计算功能将同一层面的RS-EPI DWI的B值1000影像分别与T2W-TSE MRI和CT影像进行融合定位。测量胆脂瘤阳性信号的最小直径,将RS-EPI DWI序列与SS-EPI DWI序列获取的影像进行比较。结果胆脂瘤在RS-EPI DWI序列b值为0的影像学特征表现与T2W-TSE MRI相似,然而在RS-EPI DWI序列b值为1000的图像中,胆脂瘤表现为白色高信号,边界清晰,脑脊液等液体为黑色的低信号,脑组织为中等灰白色信号,边缘部位有较强信号,普通炎症病灶表现为黑色低信号。SS-EPI DWI序列b值为0的影像显示脑组织有较大的变形,在SS-EPI DWI序列b值为1000的图像中,胆脂瘤显示为白色高信号,其范围小于RS-EPI DWI序列b值为1000的图像显影。将RS-EPI DWI序列b值为1000的图像与T2W-TSE MRI进行融合精准地验证了前者显示的胆脂瘤的解剖定位,与CT融合显示的解剖定位更加利于识别病灶。RS-EPI DWI检测胆脂瘤的阳性率为100%,无假阴性;SS-EPI DWI检测胆脂瘤的阳性率为81.0%,假阴性率为19.0%,二者相差非常显著(P<0.05, Pearsonχ2检验)。RS-EPI DWI在对照组有1例假阳性,SS-EPI DWI在对照组无假阳性。RS-EPI DWI显示最小尺寸的平均值为1233.3μm,最小值为700μm,SS-EPI DWI显示最小尺寸的平均值为1968.8μm,最小值为1000μm,二者平均值相差非常显著(P<0.01,配对t检验)。RS-EPI DWI显示平均阳性层数为4.2,最多阳性层数为10层,SS-EPI DWI显示平均层数为3.1,最多阳性层数为11层,二者相差非常显著(P<0.01,配对t检验)。结论 RS-EPI DWI较SS-EPI DWI序列检测中耳胆脂瘤的灵敏度更高,形态结构显示更加清晰。

RS-EPI DWI and SS-EPI DWI Sequences Imaging for Diagnosis of Cholesteatoma

Objective To compare 3 T high-resolution readout-segmented-echo-planar imaging diffusion-weighted imaging(RS-EPI DWI) and single-shot EPI DWI(SS-EPI DWI) imaging in diagnosis of cholesteatoma. Method Patients diagnosed with chronic otitis media with(n=21) or without cholesteatoma(n=7, control) by otoscopy or high resolution CT were imaged using the RS-EPI DWI and SS-EPI DWI protocols. Diagnosis was later confirmed by visual examination during surgery and pathological examination. The following sequences were used in MRI imaging:T2-weighted turbo spin echo(T2 W-TSE), RS-EPI DWI and SS-EPI DWI. Areas at b value of 1000 on RS-EPI DWI images were registered to those on T2 W-TSE and CT images of the same plane to obtain anatomical information using the ImageJ software. Minimum dimensions of cholesteatoma signals were measured and compared between RS-EPI DWI and SS-EPI DWI images. Results Cholesteatoma generated similar signals on b value = 0 RS-EPI DWI and T2 W-TSE MRI images, but showing hyperintense signals with sharp borders on the former against hypointense signal dark areas of cerebrospinal fluid(CSF) and inflamed tissues and medium intensity signal grey areas of the brain(with hyperintense signal borders), although also showing noticeable distortion on the brain. Bright cholesteatoma signals were also detected on b value = 1000 SS-EPI DWI images, although smaller than those on b value = 1000 RS-EPI DWI images. The precise location of cholesteatoma was depicted by registering b value 1000 RS-EPI DWI information to T2 W-TSE MRI,and fusing RS-EPI DWI images with CT scan provided easier lesion identification. The rate of positive cholesteatoma identification was 100% on RS-EPI DWI images(with no false negative reading) and 81.0% on SS-EPI DWI images(with a false negative rate of 19.0%)(P<0.05, Pearson χ2-test). For the control cases, there was 1 false positive reading from RS-EPI DWI images and none from SS-EPI DWI images. The minimum dimension detected on RS-EPI DWI images was 700 μm(mean = 1233.3 μm) and 1000 μm on SS-EPI DWI images(mean = 1968.8 μm)(P<0.01, paired t-test). The maximum number of positive slices detected by RS-EPI DWI was 10(mean = 4.2) and 11 by SS-EPI DWI(mean = 3.1)(P<0.01, paired t-test). Conclusion The RS-EPI DWI protocol is more sensitive than SS-EPI DWI in diagnosing cholesteatoma with improved morphological information.