Changes of tumor microcirculation after transcatheter arterial chemoembolization: First pass perfusion MR imaging and Chinese ink casting in a rabbit model

Aim: To observe the change of tumor microcirculation after transcatheter arterial chemoembolization (TACE) with bletilla microspheres by using first pass perfusion MR imaging (FP) and Chinese ink casting. Methods: VX2 carcinoma cells were surgically implanted into the left and right lobes of liver of 30 New Zealand white rabbits, which were divided into 3 groups at random. Emulsion of lipiodol mixed with mitomycin C, and 5-FU bletilla microspheres were injected into the hepatic artery respectively, and saline was used as control agent. MR imaging was performed with turbo-flash sequence 14 d after tumor implantation and 7 d after interventional therapy. The steepest slopes (SS) of the signal intensity versus time curves were created for quantitative analysis, 7.5% Chinese ink gelatin solution was injected through ascending artery (17 cases) or portal vein (2 cases) for lesion microvessel area (MVA) measurement after the last MRI examination. The correlation between perfusion imaging and MVA was studied blindly. Results: The SS values at the rim of tumor in lipiodol group (mean, 49% per second) and bletilla group (mean, 35% per second) were significantly decreased (P<0.05) as compared with control group (mean, 124% per second), no difference was found between lipiodol and bletilla groups (P>0.05). In lipiodol group, the MVAs (24 974±11 836 μm²) in the center of the tumor were significantly smaller than those of the control group (35 510±15 675 μm²) (P<0.05), while the MVAs (80 031±22 745 μm² ) around the tumor were significantly increased because small and dense plexuses appeared around the tumor which correlated to intense reaction of granulation tissue. None of the vessels was seen in the tumor in bletilla group, the peripheral MVAs of the tumor were significantly smaller than those of the control group (P<015) and lipiodol group (P<0.05). There was a good correlation between SS and MVAs in control group (r_s, 0.985, P<0.0001) and bletilla group (r_s, 0.743, P<0.05), the correlation was not significant in lipiodol group (r_s, 0.527, P>0.05). Conclusion: TACE with bletilla micropheres may enhance its anti-tumor effect by inhibiting the angiogenesis, and FP-MRI provides useful information to assess the TACE effect by depicting tumor vascularization and perfusion.