Experimental Study Of Radiation Induced Liver Injury On Rabbit By3.0Tesla Magnetic Resonance Imaging

Part I: Experimental Study on Rabbit Liver by3.0Teslamagnetic resonance diffusion-weighted imagingObjective To explore the methodology，characters，quantificational index and referencestandard of3.0Tesla MR difusion—weighted imaging on the normal rabbit’s liver.Methods Twenty New Zealand white rabbits were enrolled and DWI was performedafter anaesthetics with multi-b values at3T MRI scanner. ADC values（including thedifference between maximum and minimum ADC values）, signal strengths （SH）, noise（SD）, SNR, and quality index （QI） were recorded and analyzed. Results With b valueincreasing, the ADC values decreased at the same time （P<0.01）. The differencebetween maximum and minimum ADC values with b＝1000s/mm2is the least （goodstability）, b＝600s/mm2is the second least and b=300s/mm2is greatest（bad stability）.The SH decreased at the same time （P<0.01），but the difference among DWI withb=600,800, and1000s/mm2was insignificant （P>0.05）. The SD decreased at the sametime （P<0.01）, but the difference among DWI with b=800s/mm2or b=1000s/mm2wasinsignificant （P>0.05）. The SNR decreased at the same time （P<0.01）, but there were nosignificant differences between both DWI with b=600s/mm2and b=800s/mm2orb=1000s/mm2（P>0.05）. And SNR of DWI with b=800s/mm2and b=1000s/mm2waslower. The QI decreased at the same time （P<0.01）, but the difference among DWI withb=800s/mm2or b=1000s/mm2was insignificant （P>0.05）. Conclusion In the magneticresonance diffusion-weighted imaging of rabbit liver on3T MR machine，it is better touse b=600s/mm2for reducing scanner time, assuring better diffusion weights, quantityof images and stability of measuring ADC value. Part Ⅱ: Experimental Study Of Radiation Induced Liver Injuryon Rabbit by3.0Tesla Magnetic Resonance Diffusion-WeightedImagingObjective To evaluate the diagnostic value of magnetic resonance diffusion-weightedimaging （DWI） technique in radiation-induced liver injury and its capability ofresponding hepatic pathology change at different time of post-irradiation. MethodsSixty male New Zealand white rabbits were randomly divided into six groups （tenrabbits in each group）．Control group（C0） was control group without any irradiation; Allrabbits in C1to C5group accepted virtual three dimensional conformal radiotherapy（3D-CRT）（prescribed dose:50Gy/10F,once every other day） and received DWIexamination and pathologic study on the first day，third day，second week，first mouthand second mouth after radiation respectively. The ADC values of all60rabbits in sixgroups were measured in non-irradiated and irradiated liver with different b values at50,300,600,800, and1000s/mm2respectively. Results In liver HE stain study, GroupC3,C4and C5showed characteristically veno-occlusive disease（VOD）. DWIexamination showed that the ADC values of the irradiated liver in Group C2,C3,C4andC5were significantly lower than those of the non-irradiated liver with b values at300,600,800, and1000s/mm2（P<0.05）. When the b value was600s/mm2, ADC values andpathological stage of the irradiated liver showed best negative correlation（SpearmanCorrelation Analysis，r=-0.459，p<0.01）. The threshold value of ADC value todistinguish normal group（C0）and irradiated group（≥C1） was1.955×10^-3mm²/s at600s/mm2b value; When b values was1000s/mm², the threshold value of ADC value topredict normal H-E stain group（≤C1）and abnormal H-E stain group（≥C2） was1.5250×10^-3mm²/s, and the threshold value was1.5150×10^-3mm²/s to predict GroupsC0-2and Groups C3-5. Conclusion DWI examination has high sensitivity to detectradiation-induced liver injury three days after irradiation with proper b values, and ADCvalue is feasible in estimating pathology evolutionary process of some period of RILIaccurately. In conclusion, DWI can play important role in the detection of earlypathology change in RILI.