Investigation of rabbit VX2 renal tumor treated by high intensity focused ultrasound with following-up contrast CT

Objective To evaluate CT images in following up rabbit VX2 renal tumor treated by HIFU and optimize the time to perform CT scanning.Methods The animals were randomly divided into two groups.The first group was consisted of 9 New Zealand rabbits bearing VX2 renal tumors that were irradiated by HIFU as treated group and the second group was 5 other tumor bearing ones as controls.CT images were used to observe the features of tumors one week,one month and two months after HIFU in treated group respectively.The controls were observed only once.They all were sacrificed in the end of the study and the CT appearances were compared with those of histopathology.Results (1) Enhancement of tumor:All the tumors showed enhancement on contrast CT images before HIFU.No change could be found on CT images of control group after HIFU.In treated group,enhancement disappeared in all the tumors which accounted for 66.7% and 88.9% respectively one week and one month later after treatment.(2) Calcification of tumor:In treated group, 77.8% of tumors showed calcification on CT images one month after treatement and no calcification was found in control group.(3) Tumor volume:Tumor volume measured by CT was compared with pathological analysis using paired T test.There was no significant difference between the treated group and the control group.(4) Treating points of HIFU and tumor volume (measured by CT) had a good correlation (Pearson correlation, r= 0.667, P 0.05).(5) Pathological analysis:Coagulating necrosis was found in HIFU treated area as well as fibrosis and calcification.The tumors of control group growed up.CT images showed good ralationship with pathological changes.Conclusion CT is a useful method in evaluating the effect of HIFU for rabbit VX2 renal tumor.The CT follow up should be done one month after HIFU treatment.