| Objective To evaluate the value of diffusion-weighted imaging and dynamiccontrast-enhanced MRI in the diagnosis of focal hepatic lesions.Materials and Methods108cases with focal hepatic lesions were collected from theFirst Affiliated Hospital of Soochow University during the period of December2010toJanuary2012. All the lesions were proved by operation or puncture pathology, or incombination with ultrasound，MRI and（or） CT, or clinical outcome. The research sampleconsisted of73males and35cases of females. In addition,30healthy volunteers wereinvited as a control group. All the patients and volunteers had been the implementation ofMR examination, including conventional sequences and diffusion-weighted sequence.LAVA dynamic contrast enhanced scan were performed in all patients. Observed thecharacteristics of the lesions in conventional sequences and diffusion-weighted imaging.After dynamic contrast-enhanced scan, analyzed the contrast patterns and drew time-signalintensity curve （TIC）. Workstation processing software had been used to generate ACDmaps from diffusion-weighted imagings and measure the apparent diffusion coefficient（ADC） values in the regions of interest （ROI） when b value was800s/mm2. Statisticalanalysis was performed by SPSS17.0statistical software to determine statistical differences（when P<0.05, the difference was statistically significant）.Results⑴All the cases were high or slightly high signal on DWI except2caseswas different, which didn’t display clear because of the same signal with liver ondiffusion-weighted imagings. In all the lesions, necrotic areas of abscess appeared thehighest signal, followed by hepatic hemangiomas and mucinous metastases. However, the signal intensity of hepatocellular carcinomas, cholangiocarcinomas and solid metastaseshad no significant difference.⑵When b=800s/mm2,the mean ADC values ofhepatocellular carcinomas, cholangiocarcinomas, metastases, hepatic hemangiomas,hepatic abscess abnormal liver were respectively:（1.20±0.22）×10-3mm2/s,（1.67±0.37）×10-3mm2/s,（1.28±0.24）×10-3mm2/s,（2.13±0.25）×10-3mm/s,（0.87±0.14）×10-3mm2/s and（1.31±0.16）×10-3mm2/s. Five values, which were the upper limits of the95%confidenceinterval of the ADC values of hepatocellular carcinoma, cholangiocarcinoma, metastases,three malignant tumors and the lower limit of hepatic hemangiomas, were selected asthresholds to judge benign or malignant tumors, while abscess cases were ruled outbecause they were inflammatory lesions. If the ADC value of one occupying lesion wasgreater than the threshold, the lesion was benign; If lower, then it was considered to bemalignant, and supposed as positive results. The diagnostic sensitivity, specificity, accuracy,positive predictive value and negative predictive value were calculated. Results showedthat with the increase of the threshold, sensitivity was of an upward trend while specificityappeared a downward trend. When ADC threshold value was1.78×10-3mm2/s, thediagnostic accuracy, sensitivity, specificity, positive predictive value and negativepredictive value were respectively93.2%,93.0%,93.5%,96.4%and87.9%, whichachieved preferable test effect.⑶Hepatocellular carcinomas presented three kinds ofenhanced ways after dynamic contrast:①19lesions showed mark enhancement in earlyand （or） late arterial phase, and low signal in portal venous phase and venous phase. Thetime-signal intensity curve appeared classic form，that was sped-ascend and sped-descendpattern.②12lesions with sped-ascent and slow-descent time-signal intensity curvepresented slight enhancement in arterial phase, and peaked in the portal venous phase, kepthigh contrast or slightly weakened in venous phase.③3cases slightly enhanced duringthe first three phases and showed ring enhancement at the edge of the lesions in the delayperiod. The time-signal intensity curve displayed as slow-ascend and flat type.Cholangiocarcinoma showed mild enhancement in arterial phase, and continued to enhancegradually during portal venous phase and venous phase, in the delay period appeared mark enhancement. The time-signal intensity curve also displayed as slow-ascend and flat type.Hepatic hemangiomas had two enhanced patterns:①Small lesions which diameter lessthan1.5cm usually found almost entirely enhanced in arterial phase, and remainedenhanced during portal venous phase and venous phase, and a small region with highperfusion often could been find around the lesions. The time-signal intensity curvedisplayed as sped-ascend-flat type.②Lesions enhanced apparently from the periphery tothe center, contrast agent filled the lesions with progressive way. The time-signal intensitycurve displayed as slow-ascend and flat type. The enhanced characteristic of metastasesvaried. Typical enhancement of metastases was "Bull’s-eye sign". Most appeared ring orlace enhancement. Some were sped-ascend and sped-descend type. Lace enhancementappeared in the arterial phase of abscess while necrosis area in the lesions wasn’t enhanced.Large patchy of hypertransfusion could be seen in the peripheral hepatic parenchymal. Itwas difficult to locate the solid portion of metastases and abscess, so time-signal intensitycurves were omitted in this study.⑷In this group, MIP reconstruction was performedusing LAVA image of32patients, with a total of34hepatocellular carcinoma lesions.11lesions could be seen fed by hepatic artery, and2-3grade branches of the hepatic arterywere abnormal thickening. The best period to observe feeding artery was the early arterialphase. MIP reconstruction of large primary carcinomas presented obvious staining of tumor.In addition, five cases displayed clearly adjacent vessel invasion by tumor well.Conclusion⑴Different focal hepatic lesions display different features， ADCvalues also have varying degrees of differences. The ADC values of malignant l occupyinglesions, benign occupying lesions and inflammatory lesions are statistically significantdifference. But it is not proper to consider that the ADC value of malignant focal hepaticlesions is lower than benign lesions’ ADC value simply （in this study, the lowest group ofADC value is hepatic abscess）.⑵Combining with conventional scanning sequences,hepatic hemangioma and hepatic abscess can be confirmed on DWI.⑶Although thedetection rate of lesions is very high on DWI, differential diagnosis of some occupyinglesions also can be implemented, but DWI can not replace the role of dynamic contrast-enhanced sequence in the diagnosis and differential diagnosis of focal hepaticlesions. Only together with DWI and DCE-MRI can make a more comprehensive andaccurate diagnosis of focal hepatic lesions.⑷Compared with other sequences, LAVAdynamic contrast enhanced MRI has higher detection rate and diagnostic accuracy. |
PDF Full Text Request