常规Gd-DTPA增强后脑DWI检查的可行性研究

目的探讨常规增强扫描之后行DWI检查的可行性。方法采用西门子1．5T超导型MR扫描系统对86例颅内病变患者进行检查，先行常规T1WI、T2WI及DWI（b=0、1000s／mm^2）横断面扫描，然后行常规增强T1WI扫描，对比剂为钆喷替酸葡甲胺（Gd—DTPA），剂量为0．1mmol／kg，注药速度为1ml／s，注入对比剂4min后以相同的参数再行一次DWI扫描，将增强前后的DWI原始图像均输入工作站获得表观弥散系数图。分别计算出肿瘤强化实质区、坏死囊变区、脑梗死区、正常脑灰质区、正常脑白质区，正常神经核团区域增强前后的DWI信号噪声比（SNR）、对比噪声比（CNR）、ADC值。采用配对t检验比较不同区域增强前、后SNR、CNR及ADC值的差别。结果正常脑组织DWI的SNR和ADC值于增强前后均无明显差别，P〉0．05；增强前后肿瘤强化实质区、囊变坏死区、脑梗死DWI的SNR、CNR以及ADC值的差别也无统计学意义（P〉0．05）。结论常规Gd—DTPA增强4min后，正常脑组织和不同的病变组织的DWI（b=0、1000s／mm。）SNR、CNR及ADC值无明显改变，常规Gd—DTPA增强4min后行脑DWI（b=0、1000s／mm^2）扫描是可行的。

Feasibility of diffusion-weighted imaging on brain after conventional Gd-DTPA enhancement

Objective To assess the feasibility of diffusion-weighted imaging (DWI) on brain after conventional Gd-DTPA enhancement scanning. Methods Eighty-six patients who were verified various brain lesion were examined. DWI was obtained using single-shot echo-planar imaging with b value of 0, 1000 s/mm2 before enhancement scanning. Patients were injected with Gd-DTPA (0.1 mmol/kg body weight; 1 ml/s). Repetition of DWI was obtained 4 minutes later when conventional enhancement scanning was finished. We examined the signal-to-noise ratio (SNR) of the normal brain tissues and various brain lesions and evaluated the contrast-to-noise ratio (CNR) of each lesion. In addition, the ADC values calculated from the DWI images were compared before and after administration of Gd-DTPA. The statistical significance of differences between precontrast and postcontrast administration was determined by use of a paired t test. Results The SNR and CNR of the DWI were not significantly different before and after administration of Gd-DTPA (P>0.05). There were no significant differences of ADC value before and after administration of Gd-DTPA in the normal brain tissues, and even in lesions with enhancing parenchymatou tissues or necrosis/cyst regions, infarct regions (P>0.05). Conclusion There was no significant difference before and after administration of Gd-DTPA in the SNR or CNR of DWI and ADC value. This indicates the feasibility of DWI (b=0, 1000 s/mm2) on brain after conventional enhancement scanning in clinical practice.