| Part I:The Application of MR Diffusion-Weighted Image in Early Evaluation of Therapeutic Effect of Local Thermal Ablation for Hepatocellular Carcinoma and Selection of Suitable b ValueObjective To investigate the application of MR diffusion-weighted image (DWI) in early evaluation of therapeutic effect of local thermal ablation for hepatocellular carcinoma and selection of suitable b value. Methods Institutional review board approval was obtained, and all patients were informed consent.21 nodules (mean diameter,2.4 cm; range,1.3-4.0 cm) histologically proved as hepatocellular carcinomas (HCCs) of 21 patients (19 men,2 women; mean age, 56.7 years; range,32-74 years) from May 2009 to January 2010 in General Hospital of PLA were enrolled. All patients received DWI with different b values before and immediately after (within 24 hours) local thermal ablation. The differences of signal to noise ratio (SNR) and contrast to noise ratio (CNR) among T2WI, DWI400, DWI600, DWI800, DWI1000 and the ADC values of each nodule with different b values were analyzed by One-way ANOVA pre- and post-ablation. The differences of ADC values with the same b values between pre- and post-ablation were tested using Paired-Samples T Test. Receiver operating characteristic curve (ROC) analysis was performed for the comparison of viable tumor and necrosis tissue. Results SNR on T2WI, DWI400, DWI600, DWI800, DWI1000 were (81.78±30.23), (72.87±30.08), (60.48±23.48), (52.53±18.03), (44.50±19.01) pre-ablation and (54.85±21.16), (40.07±18.43), (36.23±13.03), (25.57±10.01), (19.93±8.35) post-ablation. There were significant statistical differences in the SNR among different sequences pre-(P= 0.000) and post-ablation (P=0.000). There were no significant statistical differences in CNR among different sequences both pre-(P= 0.408) and post-ablation (P= 0.196). The ADC value varied with b value, and significant statistical differences were achieved in the ADC values in different b values pre-and post-ablation. The ADC value post-ablation increased significantly than pre-ablation of each b value (P< 0.01). The ADC value was an effective parameter for identifying necrosis tissue:when b value was 800 s/mm2, a threshold value of 1.24×10-3 mm2/s permitted 73.7% sensitivity and 57.9% specificity and a threshold value of 1.32×10-3 mm2/s permitted 52.6% sensitivity and 84.2% specificity; when b value was 1000 s/mm2, a threshold value of 1.09 x 10-3 mm2/s permitted 89.5% sensitivity and 63.2% specificity and a threshold value of 1.26×10-3 mm2/s permitted 52.6% sensitivity and 89.5% specificity. Conclusion DWI has the capacity of evaluating therapeutic effect of thermal ablation for HCC. Taking into account SNR, CNR, ADC measurement and the efficacy of identifying necrosis tissue, DWI with a b value of 1000 s/mm2 is recommended for monitoring early response of HCC to local thermal ablation. PartⅡ:Preliminary Study of In Vivo Proton Magnetic Resonance Spectroscopy(1H-MRS) in Evaluation of the Early Response of Hepatocellular Carcinoma to Local Thermal AblationObjective To investigate the value of in vivo proton magnetic resonance spectroscopy (1H-MRS) in monitoring the early therapeutic response of hepatocellular carcinoma (HCC) to local thermal ablation. Methods Institutional review board approval was obtained, and all patients were informed consent.17 patients (15 men,2 women; mean age,56.6 years; range,39-74 years) who were highly suspected as hepatocellular carcinoma (HCC) from May 2009 to January 2010 in General Hospital of PLA were enrolled.17 nodules (mean diameter,2.63 cm; range,1.26-3.96 cm) of all patients received MRS before and immediately after (within 24 hours) local thermal ablation. The areas of choline, lipid and water resonance peak at 3.2 ppm,1.3 ppm and 4.7 ppm of HCCs at MRS were measured and the choline-to-lipid ratio (cho/lip) was measured by dividing the area of choline by the area of lipid. Changes in choline, lipid, water and cho/lip in the tumors before and after ablation were analyzed by using the Wilcoxon signed rank test. Results The technical success rate for MRS was 70.6%(12/17), locations of them were 5 nodules in segment 5 (S5),2 in S6,3 in S7 and 2 in S2. Of 12 nodules with analyzed MRS,3 were non-HCCs and 9 were HCCs proved by pucture biopsy. The median peak area of choline, lipid, water and cho/lip in 9 HCCs were 8.06X 104(range,0～1.96×106),9.55×106(range,1.82×105～7.43×107),5.88×107 (range,3.84×107～1.05×108),0.02 (range,0～1.23) before ablation and 0 (range,0～1.42×105),3.61×106 (range,5.54×105～2.18×107), 5.89×107 (range,1.98×107～1.02×108),0 (range,0～0.04) after ablation. Significantly statistical differences (P<0.05) were achieved in the peak area of choline and cho/lip between before and after ablation whereas no significantly statistical differences in the peak area of lipid and water betweent pre-and post-ablation (P>0.05). Conclusion In vivo'H-MRS is technically feasible for the evaluation of focal hepatic lesions and has potential in the detection of early metabolite change in HCC after local thermal ablation although larger, more definitive and quantitative studies are needed.
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