Characteristics and pathological mechanism on magnetic resonance diffusion-weighted imaging after chemoembolization in rabbit liver VX-2 tumor model

Abstract

AIM: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/mm2 , 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.

Diffusion-weighted imaging of the liver: Current applications

“…Cysts can be distinguished from solid lesions easily. The cut-off ADC was reported to be approximately 2.5 × 10 -3 mm 2 /s for distinguishing cysts from other solid liver tumors[70]. Hemangioma is also relatively easy to distinguish from malignant lesions.…”

Robust estimation of the apparent diffusion coefficient (ADC) in heterogeneous solid tumors

“…Diffusion MR is currently a key area of clinical research due to its proposed ability to characterize properties such as cellularity in tumor (1–6) and normal tissues (7), architecture of the interstitium (8, 9), tumor histological type (10), and to elucidate tissue structure (for example, mapping the paths of white matter fibers in the brain (11)). In cancer, the apparent diffusion coefficient (ADC) is of particular interest due to observations of its reduced value in tumors relative to surrounding, radiologically normal tissues (12–21), its ability to detect and characterize regional necrosis (22–26), and increases in ADC resulting from successful response to treatment of cancer (27–37).…”

Role of diffusion-weighted imaging in evaluating therapeutic efficacy after transcatheter arterial chemoembolization for hepatocellular carcinoma

“…The usefulness of DWI in the evaluation of therapeutic efficacy after TACE for hepatic tumors has already been reported in some animal and human studies. Some researchers have reported that areas of dead cells in VX-2 tumors in rabbits display high ADC, while areas of viable cells show low ADC after TACE (30,31). ADC values also correlated with pathological percentage of necrosis after TACE in a human study (32).…”