Objective To establish a novel chronic compressive cervical spinal cord injury rat model,to validate the chronic pathological characteristic.Methods Fifty-four SD rats were randomly divided into 3 groups,including control group(n =6),acute compressive group(4 h,24 h,respectively.n =6),and chronic compressive group(4 h,12 h,24 h,48 h,72 h and 1week,respectively.n =6).Two sizes of water-absorbing polyurethane polymer sheets were implanted into C5～6 epidural space on postero-lateral side in acute and chronic compressive group respectively,to induce a consistent compression in the cord after expanded.While a laminectomy on C5～6 was performed only in control group.The neurological integrity,MRI signal change in the cords,large motoneuron number in the ventral horn,and myelin staining intensity on posterior funiculus were studied.Results In the acute group at 4-24 h,the compression was confirmed significantly on T2WI image,as well as hypointense signal change intramedullary.These changes were consisted with intramedullary bleeding,tissue necrosis.Large motoneuron number(P ＜ 0.05),rather than myelin staining intensity (P ＞ 0.05),was significantly decreased compared with the control group and chronic compressive group.BBB score was 6.0 at 24 h.In the chronic group:cord distortion with progressive compression was observed on T2WI image,but without intramedullary bleeding signal change.At 4-12 h,intramedullary edema,central canal distortion were seen in the cords.Large motoneuron number and myelin staining intensity decrement were not significant(P ＞0.05).BBB score was 20.6.At 24-72 h,central canal enlargement,venous congestion,and edema were observed.Large motoneuron number was less than that in the control group.In the compressive epicenter,nerve fiber disorganization or rupture was observed.Myelin staining intensity decreased significantly after 48 h and 72 h compression (P ＜0.05).BBB score was 19.3.At lweek,vacuolation changes were noted and large motoneuron decreased (P ＜ O.05),as well as myelin density and staining intensity (P ＜ 0.05),suggesting nerve fiber demyelination.BBB score was 17.5.In the control group,there was no neurological deficit and pathological change in the cords.Conclusion The pathology and MRI characteristic consistent with chronic compressive injury change,which proved this method is able to induce a chronic course on the rat model,and established a reliable model foundation for cervical myelopathy.

Objective To elucidate the spectrum of lipid peaks in 1H-MRS of skeletal muscle and it's interpretation,to investigate the utility of 1H-MRS in evaluating intramyecellular lipid (IMCL).Methods 1H-MRS was acquired in vivo on tibialis anterior muscle (TA) and soleus muscle (S) on 5 healthy volunteers.The spectrum of the lipid peak between 0.80 and 1.80 ppm was observed with different angle between the long axis of the calf and B0.Ex vivo phantom was an cluster of capillary tubers filled with soybean oil and fat emulsion,simulating the extramyecellular lipid (EMCL) and IMCL,respectively.The spectra of the lipid peaks were compared using different angles between the phantom and Bo field.Results The lipid spectrum split to 3 to 4 peaks between 0.80 and 1.80 ppm on calf muscles,with 0.20 to 0.30 ppm interval between each neighbouring peak.The methylene peak of EMCL shifted to the right when the angle between long axis of the calf and B0 increased.The phantom could simulate the spectrum of 1H-MRS of the muscle,presenting two peaks with 0.20 to 0.30 ppm chemical shift difference between 0.80 and 1.80 ppm.They are methyl triglyceride and methylene,representing IMCL and EMCL,respectively.The peak splitting could be attributed to the high ordered muscle fibers and their chemical shift difference between inta-and extra-cellular distribution.The interval of IMCL and EMCL peaks attenuated when the angle between the muscle fiber and B0 increased from 0 to the magic angle(54.7°).Conclusion On 1H- MRS spectrum,the peak of the EMCL and IMCL splits.This indicated that 1H-MRS is an applicable method to detect IMCL noninvasively.TA is an optimizing muscle for 1H-MRS study.

Objective To demonstrate the feasibility of DTI in human calf with body phased-array coil and surface coil of spine as receiving coil on 3 T system, and to optimize the parameters of sequence, including slice thickness and b-value. Methods Fifteen healthy volunteers were recruited in this study and randomly divided into three groups. The DTI sequence for head was performed on calf in the first group (5 cases), and the sequence parameters were optimized based on the deficits of the raw and the post-processed DTI images. Then, different slice thickness were applied in the senond group (5 eases) to optimize the slice thickness, and this optimized parameter with the highest score based on quality of the post-processed DTI images was applied in the next step. Finally, different b values were applied in the last group to optimize this parameters. The b value with the highest score based on the quality of the pest-processed was the proper one. Results Three problems existed in the raw and the pest-processed images, when the DTI sequence for brain was used for the calf. First, the SNR of raw images is extremely low. Second, the muscle were unclear on the image with parts of signal lose, especially in the anterior tibialis muscle. Finally, the artifacts due to chemical shift and ghost are quite serious. The scores for muscle display quality with slice thickness of 4 mm , 5 mm and 6 mm were (7.0±0. 0), (8.6±0. 9) and (9.0±0. 0) score respectively, the signal less scores were (5.0±0. 0) and ( 12. 8±2. 6) and ( 13. 8±2. 2) score respectively, and the general score were (22. 0±0. 0) and (30. 1±3.8) and (31.0±4. 1 ) score respectively. The differences of above scores were significant among different slice thickness (F-value were 21. 000 and 30. 544 and 12. 390 respectively, P <0. 05 ). The muscle displaying quality, signal loss and general scores were lowest in group with 4 mm slice thickness (q-value were 4. 896.6. 120,6. 327,7. 138,3. 863 and 4. 043, P < 0. 05 ) o The scores of muscle display quality, signal loss and general for b =400 s/mm2 were (9. 0±0. 0), ( 14. 0± 2. 2 ) and ( 33.0±2. 2 ) score respectively, which were lower than those with b = 800 s/ram2 [(7.0±0.0), (6.2±2.2), (21.8±3.4) score] and b=1000 s/mm2[(7.0±0.0), (5.0±0.0), (20.6±2.2) score] (q-value were 3.873,3.873,6.650,7.672,7. 101 and 5.917, P <0.05)o The scores of muscle displaying quality, signal loss and general for b =600 s/mm2 were (8.2±1.1 ), ( 13.0± 2. 3) and ( 30. 8±3. 8 ) score respectively, which were higher than those with b = 800 s/mm2 and b= 1000 s/nun2 (q-value were 3.873, 3.873, 5.797, 6.820, 5.326 and 5.917, P <0.05).There is no significant difference between b = 600 s/ram2 and 400 s/ram2 ( q-value were 2. 582 and 0. 852 and 1. 775, P > 0. 05 ). Conclusion Our preliminary findings indicate that it is feasible to perform DTI on human calf with 3 T MR. With body phased-array coil and surface coil of spine as receiving coil, the DTI sequence were optimized to acquire enough SNB with slice thickness of 5 mm and b-value of 400 s/mm2.