Objective To verify the feasibility of eryoablation on rabbit brain tumor under interventional MRI guidance.Methods The procedures were performed under general anaesthesia.Twenty-two New Zealand white rabbit'S brains were inoculated with VX,tumor tissue through cranial holes. MR-guided cryoablation were conducted as preliminary experiment when diameter of brain tumor grew up to 0.8 cm in size.Cryoablation lasted two cycles of 5 minutes freezing, in 2 rabbits.and of 10 minutes freezing in another 2 rabbits.After procedure and MR scanning.rabbits were executed.Specimens of rabbit'S brain showed complete necrosis pathologically after cryoablation of cycles of 10 minutes freezing.The optimal parameters of eryoablation were defined.Except for the two rabbits that died of infection,the other 16 rabbits were divided into control group and therapeutic group.According to the optimal parameters of cryoablation,cryoablation of 10 minutes freezing were performed for rabbit brain tumors in therapeutic group.Venous injeetion of 20%mannitol and subcutaneous injection of dexamethasone were used for dehydration.None of rabbit brain tumors in the control group were treated.After cryoablation,MRI scanning Was performed immediately,7 days later,14 days later and 60 days later,to observe the ablative area and the pathologic changes.The survival time wag recorded.Resuits Brain tumors could be found in all New Zealand white rabbits after inoculation except two died of inflammation.The maximum diameter of brain tumors Was from 0.7 to 1.0 elEL The tumors showed slight low signal on T1WI and slight high signal on T2WI as well as comrast enhancement after injection of Gd-DTPA.Pathologically coagulative necrosis were observed after cryoablation immediately,7 days and 14 days later,and liquefactive necrosis was found 60 days later.The correlation between MRI and pathologic appearance of tmnors are consistent.The therapeutic area ranged from 1.0 to 1.5 em.,The maximium diameter of ice ball ranged from 1.5 to 2.0 cm Conclusion CiToablation for brain tumor iS a safe and feasible therapy.

Objective To investigate the relationship between cerebral white matter fractional anisotropy(FA)and metabolite con-centrations measured by 1 H magnetic resonance spectroscopy(1 H-MRS)in healthy adults.Methods Diffusion tensor imaging(DTI) and 1 H-MRS were acquired from thirty-one healthy adults at 3.0 T MR system.The concentrations of N-acetylaspartate(NAA), choline(Cho),creatine(Cr),the ratios of NAA/Cr and FA values of DTI were measured in 353 voxels,covering the bilateral medium corona radiata.According to the age,all voxels were divided into two groups:the senior group (mean age=29 years),and the senior group(mean age=5 6 years).The correlations between FA values and age were analyzed using Pearson’s correlation coefficients.The correlations between FA values and metabolite concentrations were estimated using partial correlations test controlling for the age re-lated bias.Results Pearson’s correlation analysis revealed a negative correlation between FA values and age in 353 voxels(r=-0.146,P<0.05),senior group(r=-0.204,P<0.05)and senior group(r=-0.162,P<0.05).Only the correlation between NAA and FA values were significant(r=0.339,P<0.05;r=0.213,P<0.05;r=0.430,P<0.05).There were positive relation-ships between FA values and NAA/Cr among 353 voxels (r=0.166,P<0.05)and senior group(r=0.305,P<0.05).Conclusion There are correlations between cerebral white matter FA values and metabolite concentrations measured by 1 H-MRS .Combining 1 H-MRS with DTI can reveal the relationship between microscopic white matter integrity and metabolic characteristics of the white matter.

Objective To evaluate the feasibility, accuracy and its clinical value of MRI-guided needle biopsy of lung lesions. Methods A total of 137 patients with pulmonary nodules or masses underwent lung biopsy in low-field open MRI equipped with iPath 200 optical tracking systems. Among them, 103 cases had solitary pulmonary lesion; the other 34 cases had multiple foci. The maximum diameter of the lesion was not smaller than 3.5 cm ( ≥ 3.5 cm) in 57 patients, between 1.5 cm and 3.4 cm( 1.5-3.4 cm) in 71 patients, not greater than 1.4 cm ( ≤ 1.4 cm) in 9 patients. Results The puncture success rate was 100.0% (57/57) for lesions ≥3.5 cm, 98.6% (70/71) for lesions 1.5-3.4 cm,77.8% (7/9) for lesions ≤1.4 cm and 97. 8% (134/137) for total cases, respectively. According to the pathological results, pulmonary lesions were malignant in 98 cases and benign in 39 cases. The sensitivity,specificity, accuracy, positive predictive value and negative predictive value of MRI-guided lung biopsy were 94.2%(98/104), 100.0% (33/33), 95.6% (131/137), 100.0% (98/98) and 84.6% (33/39),respectively. Conclusion MRI-guided needle biopsy of lung lesion can be performed precisely in a lowfield open MRI with a low risk of complications. As a supplement to US or CT-guided biopsy, it is worth further promotion and application.

Objective To explore the value of MR imaging-guided percutaneous lumbar discectomy and discolysis with oxygen-ozone mixture for treatment of posterolateral lumbar disc herniation via a new puncture approach of facet joint medial route. Methods All 114 lumbar intervertebral discs in 103 patients were diagnosed as posterolateral lumber disc herniation by CT or MRI, which were located at the levels of L3-4 in 5 cases, LA-5 in 87 cases and L5-S1 in 22 cases. The procedure was guided under 0. 23 T open magnetic resonance with iPath 200 optical tracking system. A 14 G MR-compatible needle was punctured into the disc center via a new puncture approach of facet joint medial route. The therapy steps were as follows: firstly, cut nucleus pulposus and inject 6 ml oxygen-ozone mixture of 60 μg/ml in the disc center;secondly, retreat the needle to the local prominence, cut prominent part and inject 6 ml oxygen-ozone mixture of 60 μg/ml. Thirdly, retreat the needle to the periradicular nerve root, inject 15 ml oxygen-ozone mixture of 40 μg/ml and 4 ml pain-block liquid. All patients were followed up at 3 days, 1 month, 3 months and 6 months after operation, evaluated for the effect of treatment with the modified Macnab criteria, and the results were compared with the χ2 test. Results All procedures were successfully performed. Intraoperative dural injury occurred in 5 cases. Postoperative infection of intervertebral space occurred in 2 cases. The clinical effective rate was 96. 1% (99/103), 84.5% (87/103), 94.2% (97/103), 95.1% (98/103)respectively at 3 days, 1 month, 3 months and 6 months after operation, and the differences were signifieant (χ2 = 12. 942, P = 0. 005 ) . Conclusion MR imaging-guided percutaneous lumbar discectomy and discolysis with oxygen-ozone mixture via facet joint medial route is a minimally invasive, safety and effective method for the treatment of posterolateral lumbar disc herniation.

Objective To explore the value of MR imaging-guided percutaneous cervical discectomy and discolysis with oxygen-ozone mixture for treatment of cervical disc herniation.Methods Eight herniated cervical discs in 7 patients were diagnosed by MRI, including 5 discs of lateral protruding type, 2 discs of paramedian protruding type and one disc of central protruding type.All patients underwent MR imaging-guided percutaneous cervical discectomy and discolysis with oxygen-ozone mixture.The procedures were guided by a set of 0.23 T open MR system mounted with iPath 200 optical tracking system.The herniated portion of the disc was punctured with a 14 G MR-compatible needle in the healthy side via anterolateral oblique route.The interventional steps were as follows; firstly, cut herniated part with percutaneous discectomy probe and inject 2ml oxygen-ozone mixture of 60 μg/ml; secondly, retreat the needle to the disc center, resect nucleus pulposus, and inject 2 ml oxygen-ozone mixture of 60 μg/ml.All patients were followed up for 6 months, with 4 patients by telephone and 3 patients in outpatient clinic.The effect of treatment was evaluated according to Williams postoperative assessment standard.Results All procedures were performed successfully.The clinical outcome was evaluated as excellent in 5 cases, good in 1 case and fair in 1 case.The total ratio of excellent and good was 85.7%.No serious complication occurred expect 1 case with intraoperative paroxysmal pain.Conclusion MR imaging-guided percutaneous cervical discectomy and discolysis with oxygen-ozone mixture was a safe, effective and minimally invasive method for the treatment of cervical disc herniation.