Study Of Founctional Magnetic Resonance Imaging On Monitoring Hepatic Carcinoma Response To Transcatheter Arterial Chemoembolization

Partâ… Study of functional MR imaging in a rabbit model bearing VX2 liver tumorObjective To develope a rabbit model of liver tumor and investigate the feasibility of diffusion MR(DWI),perfusion(PWI) and magnetic resonance spectroscopy(MRS) in this animal model.Methods Sixteen adult male New Zealand White rabbits were selected as carrier rabbits,the VX2 tumor cells were implanted into the left lobe of the liver,and thus developed the implanted model of hepatic carcinoma.Two weeks later,15 rabbits bearing VX2 tumors successfully underwent conventional MRI(including T2WI and T1WI),DWI,PWI and MRS examination. All the raw data were transferred to the post processing workstation for further analysis.DSA and pathological examination were performed subsequently, immunohistochemical staining of CD31,VEGF and p53 were also performed. Resultsâ‘ Fifteen rabbits(93.8%) were implanted successfully,18 tumors were detected on MRI,most of them were solitary(12/15,80%).â‘¡All tumors were detected on DWI,manifested as a hyper-intense lesion,whereas hypo-intense on ADC map.Quality of DWI degraded as the b value increasing.The tumor was red on rHBV map,the perfusion curves were satisfactory.MRS was successfully conducted in all tumors,the quality of MRS was:2 spectra scored 1;3 scored 2;9 scored 3;4 scored 4.â‘¢DSA showed the tumor was hypervascular,and the left hepatic artery exclusively supplies blood flow to the tumor.â‘£CD31 expression was detected in the vascular endothelial cells,VEGF and p53 expression was revealed in the tumor cells. Conclusion The rabbit model bearing VX2 liver carcinoma is hypervascular and can be easily developed.It's technically feasible to perform the diffusion-,perfusion-weighted MR and MRS study in the rabbit liver tumor. Partâ…¡Monitoring hepatic tumor response to TACE in rabbits by diffusion-weighted magnetic resonance imagingObjective To evaluate diffusion-weighted MR in assessing tumor response to transarterial chemoembolization(TACE) in a rabbit model,and to explore the diffusion gradient b-factor that optimizes both the measurement of apparent diffusion coefficient(ADC) and contrast-to-noise(CNR).Methods VX2 carcinoma cells were implanted in the livers of 12 healthy New Zealand white rabbits.All 12 rabbits beating VX2 tumors were treated with TACE.Conventional and diffusion-weighted MRI with various b values(0,200,400,600,1000,2000s/mm²) was performed using the same protocol before and 3 d after being treated with TACE. ADC values and contrast-to-noise ratio(CNR) of each tumor pre- and post-treatment with different b factors were compared.Percentage of necrotic area in each rabbit at histological specimen was calculated.The ADCs and CNRs of the same tumor on different b values were analyzed by ANOVA;the ADCs and CNRs between pre- and post-treatment were compared by Paired-sample T Test;and the correlation between ADC values and extent of necrosis was analyzed by a Pearson's correlation test. Results The quality of diffusion-weighted images diminished as the b value increased. ADCs and CNRs of the same lesion measured on different b-value DWI were significantly different(P＜0.05);ADC values between pre- and post-treatment were significantly different when b=600,1000,2000s/mm²(P＜0.05);CNRs between preand post-treatment were significantly different when b= 600,1000 s/mm²(P＜0.05).The mean percentage of necrotic cells present within the tumor was(89.1±10.6)%.A significant positive correlation was found between ADC values and the extent of necrosis with all b values except for b200,a higher relative coefficient between ADC values and percentage of necrosis was found on DWI with b1000 and b2000(P＜0.01).Conclusion DWI can early evaluate the tumor necrosis after TACE by measuring ADC values.Taking into account both CNR and ADC measurement,b value of 1000s/mm² is recommended. Partâ…¢Monitoring hepatic tumor response to TACE in rabbits by perfusion-weighted magnetic resonance imagingObjective To evaluate the value of perfusion-weighted MR on assessing tumor response to TACE in a rabbit model by measurement of PWI parameters,with comparison of MVD and VEGF expression in the tumor.Methods VX2 carcinoma cells were implanted in the livers of 24 healthy New Zealand white rabbits.Conventional and perfusion-weighted MRI was performed 2 weeks later.All 24 rabbits bearing VX2 tumors in the livers were divided randomly into two groups: group A underwent TACE treatment,while group B untreated.Three days after treatment,both groups performed MRI study using the same protocol as before,rHBV map was developed on the post processing workstation,ROI was placed on the tumor and the signal intensity-time curve was obtained.The following parameters were measured:time to peak(TTP),the maximal signal reduction ratio(SRR_max) and steepest slope(SS).The tumors were dissected and sliced,and MVD and the staining intensity of VEGF were evaluated.The perfusion parameters and VEGF,MVD between pre- and post-treatment were compared by Paired-sample T Test;and the correlation between perfusion parameters and VEGF,MVD was analyzed by a Pearson correlation test.Results The peripheral area of the tumor was hyperperfusioned, which was red on rHBV map.SRR_max,SS of the tumors in TACE group were significantly lower than those of control group(P＜0.05);TTP was prolonged without significant difference(P＞0.05).MVD of the tumors in TACE group were significantly lower than those of control group;while VEGF was higher without significant difference.There was a positive correlation between SRR_max,SS and MVD both in group A and B,and there was no correlation between VEGF and all perfusion parameters.Conclusion SRR_max,SS are closely correlated with MVD,PWI can evaluate the change of the tumor perfusion after TACE treatment. Partâ…£Early assessing hepatic tumor response to TACE in rabbits by ¹H magnetic resonance spectroscopyObjective To evaluate the feasibility of ¹H-MRS on quantitative assessment of tumor response to TACE.Methods VX2 carcinoma cells were implanted in the livers of 16 healthy New Zealand white rabbits.All 16 rabbits bearing VX2 tumors were treated with TACE.Conventional MRI and ¹H-MRS was performed using the same protocol before and 3 d after being treated with TACE.Raw data were transferred to the post processing workstation,and the quality of the MRS was scored.The spectra scored 3 or 4 were analyzed quantitatively by SAGE,and Cho/Lip ratios were calculated.Percentage of necrotic area in each rabbit at histological specimen was evaluated.The Cho/Lip ratios between pre- and post-treatment were compared by Paired-sample T Test.Results ¹H-MRS was performed successfully in 15 tumors pre-treatment whereas 13 tumors post-treatment. Ten of all the MR spectroscopic data could be analyzed further.The Cho/Lip ratios decreased significantly post-treatment by comparison with those of pre-treatment(P＜0.05).The mean percentage of necrotic cells present within the tumor was(82.5±12.4)%.Conclusion ¹HMRS has the potential of evaluation of early metabolite change in hepatic tumor by measuring the change of Cho/Lip,but its reproducibility and stability need to be improved.