Objective: To explore the changes of magnetic resonance imaging (MRI) and computed tomography (CT) after transplantation of VX2 carcinoma into lumbar vertebrae of rabbits under CT guidance and examine its relationship with the onset of paralysis.
Methods: A total of 52 rabbits were randomly divided into 4 groups. Under CT guidance, pieces of VX2 carcinoma were transplanted into the first or second lumbar vertebra in Groups A, B and C (n = 14 each) while sham operation was performed in Group D (n = 10). The anticipated endpoints of group A was natural death or Day 50 post-operation, group B Day 3 after onset of paralysis, group C Day 14 post-transplantation and group D natural death or Day 50 post-operation. CT and MR scans were performed at an interval of 7 days and hind limb functions monitored daily post-operation until endpoints. Pathohistological examinations of vertebrae were performed at endpoints.
Results: All lumbar vertebrae were successfully transplanted under CT guidance. Thirty-two rabbits with spinal tumor and 9 surviving rabbits in the control group were monitored until endpoints. Abnormal signals on target vertebrae appeared on MRI in all 41 rabbits at Day 7 post-operation while positive CT findings were absent. No abnormal MRI/CT findings were found in 9 control rabbits from Day 14 post-operation to the end of study. Significant differences (P < 0.001) existed between the rates of tumor visualization with 65.6% (21/32) on MR and 3.1% (1/32) on CT at Day 14, 100% (21/21) on MR and 42.9% (9/21) on CT at Day 21. The rates of tumor visualization were 100% on both MR and CT from Day 28 to endpoints. The average survival time of Group A was significantly shorter than Group D (40 ± 4 vs 50 days, P < 0.01). The onset time of paralysis time in Group A (22 ± 5 days) had no significant difference with Group B (22 ± 5 days) (P = 0.952).
Conclusion: A rabbit model of spinal metastasis is established with high rates of success and reproducibility. Vertebral tumor may be located earlier on MR than CT after transplantation of VX2 carcinoma. The examinations of MRI and CT after Day 7 post-operation are controversial. The survival time of rabbits with paralysis caused by spinal tumor is significantly shortened.