Characteristics and pathological mechanism on magnetic resonance diffusion-weighted imaging after chemoembolization in rabbit liver VX-2 tumor model.
OBJECTIVE
To investigate dynamic characteristics and pathological mechanism of signal in rabbit VX-2 tumor model on diffusion-weighted imaging (DWI) after chemoembolization.


METHODS
Forty New Zealand rabbits were included in the study and forty-seven rabbit VX-2 tumor models were raised by implanting directly and intrahepatically after abdominal cavity opened. Forty VX-2 tumor models from them were divided into four groups. DWI was performed periodically and respectively for each group after chemoembolization. All VX-2 tumor samples of each group were studied by pathology. The distinction of VX-2 tumors on DWI was assessed by their apparent diffusion coefficient (ADC) values. The statistical significance between different time groups, different area groups or different b-value groups was calculated by using SPSS12.0 software.


RESULTS
Under b-value of 100 s/mm(2), ADC values were lowest at 16 h after chemoembolization in area of VX-2 tumor periphery, central, and normal liver parenchyma around tumor, but turned to increase with further elongation of chemoembolization treatment. The distinction of ADC between different time groups was significant respectively (F = 7.325, P < 0.001; F = 2.496, P < 0.048; F = 6.856, P < 0.001). Cellular edema in the area of VX-2 tumor periphery or normal liver parenchyma around tumor, increased quickly in sixteen h after chemoembolization but, from the 16th h to the 48th h, cellular edema in the area of normal liver parenchyma around tumor decreased gradually and that in the area of VX-2 tumor periphery decreased lightly at, and then increased continually. After chemoembolization, Cellular necrosis in the area of VX-2 tumor periphery was more significantly high than that before chemoembolization. The areas of dead cells in VX-2 tumors manifested low signal and high ADC value, while the areas of viable cells manifested high signal and low ADC value.


CONCLUSIONS
DWI is able to detect and differentiate tumor necrotic areas from viable cellular areas before and after chemoembolization. ADC of normal liver parenchyma and VX-2 tumor are influenced by intracellular edema, tissue cellular death and microcirculation disturbance after chemoembolization.
Yuan
You-Hong
YH
Department of Radiology, Hunan Province People's Hospital, Changsha 410005, Hunan Province, China. heyuanyouhong@yahoo.com.cn
Xiao
En-Hua
EH
Liu
Jian-Bin
JB
He
Zhong
Z
Jin
Ke
K
Ma
Cong
C
Xiang
Jun
J
Xiao
Jian-Hua
JH
Chen
Wei-Jian
WJ
D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000098:blood supply / Q000473:pathology* / Q000628:therapy*; D016461:Chemoembolization, Therapeutic; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004195:Disease Models, Animal; D004487:Edema / Q000473:pathology; D005260:Female; D008113:Liver Neoplasms / Q000098:blood supply / Q000473:pathology* / Q000628:therapy*; D008297:Male; D008833:Microcirculation / Q000473:pathology; D009336:Necrosis / Q000175:diagnosis / Q000473:pathology; D011817:Rabbits; D012984:Software; D013997:Time Factors