Experiments And Clinical Study Of Cryoablation For Tumors Under MRI Guidance And Real-Time Monitoring

PART ONEEXPERIMENTAL STUDY OF CRYOABLATION ON RABBIT'S VX2 BRAIN TUMOR UNDER MRI GUIDANCE AND REAL-TIME MONITORINGObjective: To improve rabbit's VX₂ model of brain tumor for MRI study, evaluate the feasibility of cryoablation on rabbit brain tumor under interventional MRI guidance, analysis correlation among MRI,pathology, and therapeutic effect.Methods: The procedures were performed under a general anaesthetic. Twenty-two New Zealand white rabbit's brains were inoculated with VX₂ tumor tissue through cranioaural hole (two rabbits were infected). Six rabbits were divided into A, B group and cryoablated when diameter of brain tumor grew up to 8mm in size.Cryoablation lasted two cycles in 5 minuts, 10 minuts respectively. In each group one rabbit was exacuted after procedure and MR scanning immediately, 7 days, 14 days. Specimens of rabbit's brain were examined pathologically, and then compared with its MR appearance. The other 14 rabbits were divided into C, D group. Rabbits of C group were cryoablated with 2 cycles of lasting 10 mimutes while tumors grew up to 8mm in diametet, and rabbits of group D were not treated. Under MRI scanning in Rabbits of C, D group, the ablative area and the residue was observed. The survival time were recorded, while survival time of rabbits not died 2 months later after VX₂ tumor tissue inoculation was censored value.Results: Brain tumor could be found in all New Zealand white rabbits after inoculation except two suffered from inflammation, the size and form of brain tumor uniformity. The correlation between MRI and pathologic appearance of tumors are corresponding. All procedures were performed successfully.Tumor tissue died partly in Group A and died completely in Group B. The survival time of C group was longer than that of D group.Conclusion: The animal models of brain tumor with VX₂ tumor tissue inoculation are stable. It is an ideal model fitting MRI study and interventional therapy. Cryoablation for brain tumor is a safe and feasible therapy. Two cycles cryoablation in 10 minutes can induce complete necrosis of brain tumor cells and ice ball matches the shape and size of necrotic area. Cryoablative therapy can improve survival time of rabbit with brain tumor. PART TWOTHE CLINICAL APPLICATION RESEARCH OF OPEN MRI GUIDANDANCE AND MONITORING CRYOABLATION OF TUMOURSObjective: To assess the feasibility and safety of the percutaneous cryoablations for tumors under the intraprocedural open-configuration magnetic resonance imaging guidance and real-time monitoring, mounted with optical tracking system, then to explore the clinical curative effect with local ¹²⁵I particles insertion, 5-FU insertion.Methods: Total 51 tumors in 40 patients, confirmed histologically or clinically, were treated with percutaneous cryoablation, including liver malignant tumors: 17 cases (9 cases with primary hepatic tumors; 5 cases with cholangiocellular carcinoma; 1 cases with metastasis of lung cancers; 2 cases with metastasis of gastric cancer); intracranial tumors: 5 cases(1 cases with metastasis of breast cancer, 1 cases with metastasis of lung cancer, 2 cases with glioma, 1 cases with meningioma); lung tumors: 13 cases(12 cases with primary lung cancer: IIIa 9 cases,IIIb 1case,IV 2cases, and 1 cases with metastasis); skeletal musculature tumors: 4 cases(1 case with osteoid osteoma, 2 cases with metastasis of lung cancer, 1 case with hemangiopericytoma); maxillofacial neoplasm: 1 cases(ameloblastoma). The largest diameter of tumors ranged from 1.5cm to 12.0cm. Cryoablation was performed using a high-pressure argon system(Cryo-Hit system)with a double freeze/thaw cycle. A 2mm or 3mm MR-compatible cryoprobe was advanced into the target according to the size of tumors. Changed cryoprobe angle or multiple sites probing were performed if necessary.Totally 106 cryoablation were performed in 40 cases. For depicting cryonecrosis areas, Gd-DTPA enhance MRI were acquired on 1.5T MR scanner within 1 week after cryoablation. ¹²⁵I particles and 5-FU particles insertion were performed in partial patients. MR-guided biopsy was performed before treatment for intracranial tumors, lung tumors and skeletal musculature tumors. For intracranial tumors, fMRI was necessary before cryoablation. The evaluation of clinical curative effect of the procedures was done according to the standard of short term curative effect for argon-helium system.Results: All procedures were carried out safely and accurately. Intraprocedural MRI enabled clear visualization of the cryoprobe and iceballs as band-like and ellipsoid-like regions of signal losses, respectively. Intraprocedural MR imaging demonstrated sharply marginated iceballs engulfed and expanded out of 0.5～1.0cm tumors. ¹²⁵I particles and 5-FU particles were peripherally inserted masses under MRI guidance. One hundred and six cryoablations were performed for 51 tumors in 40 patients. The curative effect rate was 82.5%.1. Thirty-nine cryoablations were performed for 27 hepatic tumors in 17 patients. One or two cryoprobes were used during the procedures. Meanwhile ¹²⁵I particles and 5-FU particles were inserted. The procedure was performed without serious complication. 1 patient suffered from mild hydrothorax without treatment. During 3 months follow-up, the curative effect rate was 82.35% (14/17).2. Fifteen cryoablations were performed during 9 procedures in 5 brain tumor's cases. After 6 month follow-up, there were no recurrent tumors.3. Twenty-six cryoablations were performed for 13 lung tumors in 13 cases. Two cryoprobes were used during the procedure in 2 cases. At the same time ¹²⁵I particles and 5-FU particles were inserted peripherally. 1 patient had pneumothorax recovering after closed drainage. The curative effect rate was 69.2%.4. Fifteen cryoablations were performed during 4 treatments procedures for 1 large tumor in 1 patient with ameloblastoma. After 7 months follow-up, there was no recurrent.5. Eleven cryoablations were performed for 4 patients with bone tumors. The pain was significantly relief after the therapy.Conclusions: On the basis of the present study MRI-guided percutaneous targeting intervention is an accurate procedure. We conclude that MRI-guidance and monitoring cryoablation is safe, feasible, and easy to perform. Combined with insertion of ¹²⁵I and 5-FU particles, MRI-guided cryoablation can be used to substitute more invasive procedures in selected patient groups.