Objective To study the CT and MRI features of the chordoma in the mobile spine.Methods The CT and MRI fea-tures were retrospectively analyzed in twenty-four cases of chordoma in the mobile spine.Results In all the twenty-four cases,bone lesions were solitary in eight cases and multiple in sixteen cases,mostly occurred in cervical,occasionally occurred in thoracic or lum-bar vertebra.Both vertebral body and part appendix were involved in all cases.CT imaging showed that all the lesions mainly mani-fested as osteolytic bone destruction,peripheral osteosclerosis and the cortical bone were incomplete.Soft-tissue mass involved para-vertebral and intraspinal.Five lesions appeared vertebrae compression.Eight lesions appeared intervertebral foramen expansion.Le-sions appeared honeycomb or annular enhancement after contrast media injection.Lesions were presented as heterogeneous slightly hypo-isointensity on T1 WI,hyperintensity on T2 WI.Low signal fibrous septa within the tumors were seen.Lesions appeared hon-eycomb enhancement after Gd-DTPA injection.Conclusion CT and MRI findings of chordoma in the mobile spine can be regarded as characteristic,which are helpful for clinical diagnosis.

Objective To investigate the CT and MRI features of Langerhans cell histiocytosis (LCH) with multiple spinal involvement.Methods The CT and MRI data of 13 patients with multiple LCH lesions in spine confirmed by pathology were retrospectively analyzed.All of 13 cases underwent CT examination (1 case underwent enhanced scanning) and 12 cases underwent MR examination (6 cases underwent enhanced scanning).Results In 13 cases,there were 8 cases of single central lesions invading the adjacent vertebrae and 5 cases of multiple central lesions.There were 19 core spinal lesions and 15 adjacent invading lesions in a total of 34 vertebrae lesions.Eighteen core lesions (18/19,94.74 ％) had different degrees and shape of vertebral compression.A total of 34 abnormal vertebrae were found in 13 cases by CT,which were manifested as osteolytic bone destruction.Eighteen cortical bones of 19 core vertebrae were incomplete,and a paravertebral soft-tissue masses were observed.There were 33 vertebrae lesions in 12 patients who underwent MR examination,including 18 core spinal lesions and 15 adjacent invading lesions.The lesions displayed equal,slightly lower or low signal on T1WI,slightly higher or high signal on T2WI and high signals on fat suppression sequences.A paravertebral soft-tissue masses were observed in 17 core spinal lesions (17/18,94.44％).Conclusion CT and MRI manifestations of spinal multiple LCH have certain characteristics.The level of diagnosis and differential diagnosis should be improved by deepen understanding of the disease image performance,but the diagnosis still depends on the pathology.

Objective:To explore the value of X-ray signs with applying low dose of contrast agent to confirm successful puncture in direct shoulder MR arthrography.Methods:In total 669 patients who underwent shoulder MR arthrography in Peking University Third Hospital from January 2016 to August 2018 were retrospectively analyzed. All patients received the anterior approach puncture in shoulder arthrography. X-ray films were taken after 1-2 ml contrast agent was injected. Six X-ray signs of contrast agent distribution were recorded. MR arthrography findings were used to confirm whether the puncture was success. Kappa analysis was used to verify the consistency between each 2 signs. The accuracy rate of each X-ray sign to confirm the successful puncture was calculated. X-ray signs were paired to define the best diagnostic index of successful puncture.Results:Successful puncture was performed in arthrographies for all 669 cases .The displaying rates of six signs were as follows. Contrast agent distribution at overlapping humeral head away from the needle was 66.8% (447/669), in axillary recess was 64.7% (433/669), in glenohumeral space was 93.9% (628/669), in subscapular bursa was 69.8% (467/669), in sheath of long head tendon of biceps brachii (LHBT) was 1.9% (13/669), between LHBT and supraspinatus tendon was 17.2% (115/669). Consistency of each 2 signs was poor (Kappa<0.2), in which the poorest consistency was found between contrast agent overlapping humeral head away from the needle and contrast agent in glenohumeral space (Kappa=-0.115). With combining the above 2 signs, the accuracy rate for defining successful puncture was 100% (669/669).Conclusion:In direct shoulder arthrography by anterior approach, X-ray signs with low dose of contrast agent can be regard as the method to confirm successful puncture. The accuracy rate of the signs of contrast agent distribution at overlapping humeral head away from the needle or in glenohumeral space to define a successful puncture is 100%.