软组织肿瘤MR扩散成像与灌注成像的比较研究

目的 通过分析一组软组织肿瘤同一病例相同ROI的MR DWI及PWI的影像信息,比较这2种MR功能成像技术用于软组织肿瘤的定性诊断价值.方法 对50例软组织肿瘤(良性24例,恶性26例)同时行DWI及PWI.通过扩散及灌注软件分析DWI及PWI参数在良、恶性肿瘤中的表现,进行差异的t检验,对所获两法的诊断符合率进行x2检验.采用受试者操作特征曲线(ROC曲线)分析曲线下面积(AUC),确定诊断阈值并对2种诊断方法进行评价.结果 良、恶性软组织肿瘤的ADC值(良、恶性分别为(2.03±0.36)和(1.52±0.39)×10-3mm2/s]、首过灌注(FP)期信号强度丢失率良、恶性分别为(13.54±3.37)%和(47.57±5.21)%]的差异均有统计学意义(t值分别为2.515和2.938,P值均<0.05),时间-信号强度曲线(TIC)最大线性斜率良、恶性分别为(5.51±2.54)%和(7.94±3.33)%]的差异无统计学意义(t值为1.272,P>0.05);以ADC值1.866×10-3mm2/s为阈值,DWI诊断恶性肿瘤的敏感度为84.6%(22/26),特异度为83.3%(20/24);以FP期最大信号丢失率40.33%为阈值,PWI诊断恶性肿瘤的敏感度为88.5%(23/26),特异度为75.0%(18/24);TIC类型的Ⅰa型在良性肿瘤中占3/24,在恶性肿瘤中占20/26;Ⅰb型在良性肿瘤中占14/24,在恶性肿瘤中占3/26;Ⅰc型在恶性肿瘤中占3/26.Ⅱ型TIC在良性肿瘤中占7/24.在DWI上用ADC值、PWI上用FP期最大信号强度丢失率作诊断,诊断符合率分别为84.0%(42/50)和82.0%(41/50),两者的差异无统计学意义(x2=0.8,P>0.05);AUC测得的准确度分别为81.7%和83.6%,PWI诊断恶性软组织肿瘤的敏感度高.结论 以DWI和PWI的ADC值、FP期信号强度丢失率分别为1.866×10-3mm2/s和40.33%为阈值时,均有利于软组织肿瘤良、恶性的鉴别;TIC最大线性斜率对于软组织肿瘤良、恶性的鉴别意义不大;软组织肿瘤的TIC形态有助于肿瘤良、恶性的鉴别.DWI和PWI用于诊断恶性软组织肿瘤的准确性均为中等,在DWI与PWI用于诊断恶性软组织肿瘤的准确性相近时,应选择诊断敏感度较高的PWI.

The comparative study of MR diffusion-weighted imaging and MR perfusion-weighted imaging in diagnosing soft tissue tumors

Objective To evaluate MR diffusion-weighted imaging (DWI)and MR perfusion-weighted imaging(PWI) in differentiating benign from malignant soft tissue tumors by comparing the related parameters. Methods Fifty patients with soft tissue tumors verified by pathology( benign 24, malignant 26) underwent DWI and dynamic contrast-enhanced T2 * -weighted PWI. DWI and PWI data of benign and malignant soft tissue tumors were acquired at the workstation and their difference was analyzed with t-test. The diagnostic accordance rate was verified with x2-test. Subjective overall performance of two techniques were evaluated with receiver operating characteristic (ROC) analysis. Results ADC values of benign and malignant tumors were (2. 03±0. 36) × 10-3 mm2/s, ( 1.52±0. 39) × 10-3 mm2/s,respectively. The signal intensity decrease of them during the first-pass perfusion (SIdecrease ) were ( 13.54 ± 3.37 )%, (47. 57 ± 5. 21 ) % ,respectively. The maximum linearity slope rate of TIC ( SSmax ) of them were ( 5.51 ± 2. 54 ) %, (7.94 ± 3. 33) %, respectively. There were significant differences between benign and malignant tumors of ADC value and SIdecrease ( t = 2. 515,2. 938 ;P < 0. 05 ), while there was no significant difference in SSmax (t = 1. 272,P >0. 05). When the threshold of ADC value was 1. 866 × mm2/s, sensitivity and specificity for determining malignant tumors were 84. 6% (22/26)and 83.3% (20/24). When the threshold of SIdecrease was 40. 33% ,sensitivity and specificity for determining malignant tumors were 88. 5% (23/26)and 75.0% (18/24). In type Ⅰa of TIC,the proportion of benign soft tissue tumor was 3/24 and malignant tumor was 20/26. In type Ⅰb , benign tumor was 14/24 and malignant tumor was 3/26. In type Ⅰc, malignant tumor was 3/26. In type Ⅱ ,benign tumor was 7/24. The diagnostic accordance rate of DWI and PWI were 84. 0% (42/50) and 82. 0% (41/50), respectively. There was no significant difference between them ( x2 = 0. 8, P >0. 05). The accuracies of them were 81.7% , 83. 6% respectively by the area under the ROC curve (AUC). The sensitivity of PWI in diagnosing malignant soft tissue tumors was higher. Conclusions ADC value and SIdecrease are Valllable diagnostic parameters in differentiating benign and malignant soft tissue tumors. The threshold of these parameters for diagnosing malignant soft tissue tumors are 1. 866 × 10-3 mm2/s and 40. 33%, respectively. The type of TIC can help to distinguish malignant tumors from benign tumors, while the SSmax can not. The accuracies of DWI and PWI in the diagnosis of malignant soft tissue tumors are moderate. Compared with DWI, PWI should be selected firstly because of its higher sensitivity in diagnosing malignant tumors.