Objective To evaluate the value of MRI categorization of cholesteatoma of the skull base (CSB) and its MRI diagnostic characteristic Methods The CT, MRI and pathological data of 15 patients with CSB were reviewed The CSBs were categorized into type I and type II based on the difference of signal intensity on T 1 weighted image, and the differences between the two types of CSB were compared in the aspects of CT and MRI findings and osseous encroachment of the skull base Results Extremely high signal intensity on T 2 weighted image being similar to that of cerebrospinal fluid, and unenhanced tumor parenchyma on enhanced T 1 weighted image were noted in the 15 cases of CSB Of the 15 CSBs, 6 were categorized as type I and the other 9 as type II on the basis of the difference of the signal intensity on T 1 weighted image The 6 CSBs of type I, located in the prepontine and cerebellopontine angle cisterns, appeared as homogeneous hypoattenuating on CT scan and homogeneously decreased signal intensity on T 1 weighted image coupled with unenhanced tumoral capsule and relatively normal skull base The tumor parenchyma of this type was consisted of homogeneous cholesterol crystal The 9 CSBs of type II, located in unilateral floor of middle or posterior cranial fossa, were demonstrated as mixed density on CT scan and mixed signal intensity on T 1 weighted image, of which 4 presented as decreased signal intensity scattered with increased signal intensity, 5 largely as increased signal intensity The 9 cases were noted with enhanced tumoral capsule and marked osseous encroachment of the skull base, and the parenchyma of which was mainly comprised of keratinized epithelia and proteins Conclusion The categorization of CSB into type I and type II is sensible, which reflects the distinction in both histopathology and biological behaviour between the two types of CSB and plays an important role in guiding MRI diagnosis of CSB The MRI diagnostic characteristic of CSB includes the versatile signal intensity on T 1 weighted image, marked increased signal intensity on T 2 weighted image, unenhanced tumor parenchyma and type related osseous encroachment of the skull base

Objective To summarize the types and imaging features of periosteal anomaly in osteosarcoma.Further to seek the feature of genesis and advancement of periosteal anomaly and its clinical significance.Methods One hundred and twenty-eight patients with osteosarcoma were enrolled in this study,which consisted of 76 males and 52 females aging from 5 to 66 years old with an average of 19 years.Both x-ray plain film and MR images were obtained in all patients.and DWI were done in 23 patients.CT scanning was conducted in 48 patients.which included post-contrast scanning done in 36.The pathological gross specimen,macrosection and point-to-point microsection were obtained in each of 14 cases to correlate the imaging findings of periosteal anomaly to the pathological outcome.Results The imaging and pathological finding:(1)Periosteodema,occurring in 96 patients.The sign was merely demonstratable on MR image and presented as loosened periosteal structure with no tumoral infiltration pathologically.(2)Periosteal lift and thickening,demonstratable on both CT and MR image,including 13 noted on CT and 42 on MR image.Pathologically,non-tumoral infiltration was noted in the thickened periosteum.(3)Periosteal destruction,occurring in 48 patients.Periosteal destruction was merely demonstratable on MR image and presented as localized or generalized tumoral infiltration of the periosteum.(4)Linear periosteal neo-bone formation,demonstrated in 42 cases on plain films,13 cases on CT and 22 on MR images,respectively.The linear periosteal neo-bone formation was pathologically regularly arranged periosteal neo-bone.(5)Laminar periosteal neo-bone fomarion,demonstrated in 21 cases on plain films,6 cases on CT and 21 on MR images,respectively.Pathologically,it appeared as multi-layer arrangement.(6)Radiated and spiculate periosteal neo-bone formation,demonstrated in 13 cases on plain films,7 cases on CT and 14 on MR images,respectively.On both plain film and CT,the closer to the center of the tumor,the longer and denser the spicule was.The interspiculate structure was tumoral tissue pathologically.(7)Periosteal neo-bone formation of mixed type,demonstrated in 7 cases on plain films,4 cases on CT and 8 on MR images,respectively.It was composed of 2 types or more of periosteal neo-bone.Conclusions (1)Multiform periosteal anomaly can be induced by osteosarcoma,and difierent periosteal anomaly possesses different imaging findings and different pathological basis.(2)The pathologically-based classification of periosteal anomaly generalizes the 3-modality imaging findings of various periosteal pathological alterations.(3)MR imaging enables to demonstrate periosteal anomaly more early,and periosteodema and periosteal destruction without neo-bone formation can only be demonstrated by MR imaging.MR imaging is more sensitive than CT in displaying periosteal thickening.

ObjectiveTo study MRI features and pathologic basis of various periosteal changes in rabbit VX2 bone tumor and to evaluate the role of MRI in the change of periosteum in bone tumor. MethodsBone tumor models were induced by injection of VX2 carcinoma cell suspension into the medullary cavitv of right tibias in 32 rabbits.Thirty-six positive contrast cases and 4 negative contrast cases were established.Serial plain films and MRI examinations were performed at an interval of 5 days foliowing the implantation.Every 4 rabbits were sacrificed immediately after imaging. The findings of periosteal changes were compared between imaging features and pathologic Results . ResultsFrom the 5th to 15th day after implantation of VX2 carcinoma,periosteal edema was demonstrated in 32 tibias. On the 20th day,periosteal thickening Was revealed in 19 tibias. On the 25th day,periosteal new bone with the thickened periosteum attaching to its outer Surface was found in 12 tibias. On the 30th day,periosteal new bone with the thickened Deriosteum were elevated by the tumor in 11 tibias.On the 35th to 40th day,destruction of periosteal bone and periosteum were revealed.ConclusionsThe progress of periosteal changes in rabbit VX2 bone tumor included periosteal edema,periosteal thickening,periosteal new bone,destruction of periosteal new bone and destruction of periosteum. Various periosteal changes could be demonstrated on MRI and MRI is useful in evaluating periosteal changes.

BACKGROUND:During the restoration of residual molar crown, a little part of tooth is still remained commonly. After the restoration, with various forces, stress distribution affects directly the results after restoration. Finite element method is gradually applied in stress analysis on artificial tooth.OBJECTIVE: To establish the three-dimensional (3-D) finite element model of post-inlay restoration of the first residual mandibular molar crown so as to provide experimental data for improving model establishment of complicated teeth and analysis on the property of stress distribution of restoring methods.DESIGN: Repeated observation and measurement were given.SETTING: Department of Stomatology and Department of Radiology of First Hospital affiliated to Sun Yat-sen University;Department of Solid Mechanics,College of Traffics and Communications, South China University of Technology; Department of Restoration of Guanghua College of Stomatology.MATERIALS: The experiment was performed in Department of Solid Mechanics, College of Traffics and Communications of South China University of Technology from November 2003 to December 2004. Six first mandibular molars on the right side with normal morphology in vitro were collected, and Toshiba Xpress/SX spiral CT machine, image photo synthesis software and finite element analysis software ANSYS were applied in the experiment.METHODS: 1 of the 6 first mandibular molars on the right side with normal morphology in vitro was selected for pulpectomy, which was the best in density and near to clinical requirement in morphology. With pulpectomy, the prosthesis of braking-lock post-inlay restoration was prepared. Spiral CT-cross scanning was performed in premolar crown before the restoration, the residual crown with post-inlay in main root canal after restoration and the residual crown with braking-lock second post-inlay restoration. With image photosynthesis software, 3-D digital model of residual tooth and metal part was established and the entire tooth model was prepared after adhesion of two parts. In order to provide better boundary conditions of simulated natural tooth in practice, alveolar bone was considered. Under Mesh order in ANSYS software, automatic mesh generation was performed in the model directly.MAIN OUTCOME MEASURES: Establishment of 3-D finite element models of residual tooth before restoration, post inlay, and alveolar bone and tooth after restoration and the results of mesh generation.RESULTS: By establishing 3-D finite element models of residual tooth before restoration, post inlay, alveolar bone and tooth after restoration and automatic mesh generation, there were altogether 117720 units and 20988nodes. Good geometric similarity presents between the construction model of 3-D finite element model and solid tissue.CONCLUSION: Combination of 3-D finite-element model with spiral Ctcross technology establishes complex dental models, simulates practical conditions authentically and is good in operation.

Objective To investigate the effect of imaging parameters and postprocessing methods on the quality of MR imaging of short T2 components with 3D ultrashort TE (UTE) double echo pulse sequence. Methods 3D UTE double echo pulse sequence was performed on dry human femoral specimen and the tibial diaphyses, knee joints, and tendons of ankles of a group of healthy volunteers. To investigate the effect of different trajectory delays of the imaging system(-6, -3, -2, - 1,0, 1,2, 3 s), different flip angles(4°, 8°, 12°, 16°, 20°, 24°), different TEs (0. 08, 0. 16, 0. 24, 0. 35 ms)and different postprocessing methods(difference imaging of subtracted volume and non-volume UTE)on the 3D UTE MR imaging quality, the SNR and CNR were calculated and compared, and the artifacts of the images were analysed. Results The cortical bone, periosteum, tendon and meniscus showed high signal intensity on the images of UTE pulse sequence. The best SNR was acquired with 2 s trajectory delay. The best flip angle was 8° to 12° for the human UTE imaging in vivo. The highest CNR was obtained from the TE of 0. 08 ms. The longer the TE was, the more artifacts appeared. The SNR of difference imagewas improved when image subtraction was performed afer multiplanar reconstruction (MPR) of the primary double echo images.Conclusions The short T2 components show high signal intensity on the MRI of 3D UTE double echo pulse sequence. The imaging quality can be improved by shortening TE, using appropriate flip angle and performing subtraction for difference image after MPR of the primary double echo images.

Objective To determine the optimal sequences and scan parameters of Brachial Plexus MRI.Methods Eighteen volunteers were underwent conventional MRI and echo planar imaging scanning. The images acquired were compared with the standard anatomical pictures. Results Ventral rami, ganglion, trunks, cords and some peripheral nerves of brachial plexus were demonstrated very well by echo planar imaging with the post-processing techniques such as MIP, thin slice MIP and MPR.In 18/18 cases the postganglions on both sides and 17/18 cases the preganglions of brachial plexus on both sides could be visualized in EPI pre-processed and post-processed images.Conclusion Echo planar imaging is an effective technique of accurately displaying brachial plexus and adjacent structures. It has potential value in the diagnosis and treatment of brachial plexus diseases. It is also a potential technique to demonstrate other peripheral nerves accurately.

Objective To analyze the MRI characters of Charcot joint, and to evaluate the diagnostic value of X-ray, CT, and MRI on Charcot joint. Methods Eight patients with 8 Charcot joints underwent X-ray, CT, and MR examinations. 6 of them had syringomyelia, 1 patient had injury of the spinal cord, and 1 case had diabetes. All 8 patients had sensory reduction or deficit in the sick extremities. Results There were two types of Charcot joint, hypertrophic and atrophic. Radiographic and CT features of hypertrophic joint (n=3) showed hyperostotic osteosclerosis and mammoth osteophytes in the sick bones, periarticular ossification,and articular disorganization. Radiographic and CT features of atrophic joint (n=5) showed extensive bone resorption (destruction), periarticular debris, and articular disorganization. Main MRI features of Charcot joint included hydrarthrosis within joint capsule, thickened, loose, and elongated joint capsule with para-joint, peri-diaphysis, and inter-muscular extension in a pseudopodia pattern. The irregular joint capsule wall was presented as mild hypointensity on T 1WI, slight hyper-intensity on T 2WI, and was markedly enhanced after Gd-DTPA was administrated, which was considered as a characteristic manifestation of the lesion. Soft tissue mass containing hypo-intense stripes on both T 1WI and T 2WI was commonly noted adjacent to the involved joint. Conclusion X-rays plain film is the first choice for the diagnosis of Charcot joint, and MRI is pretty useful in the diagnosis of Charcot joint.

Objective To analyze the X -ray, CT, and MR imaging findings in osteoid osteoma. Methods Forty-eight cases of osteoid osteoma proved by surgical pathology were collected, including 33 males and 15 females. Among the 48 cases, all patients had plane films, 32 were imaged with CT scanning, 10 with MR imaging, and 8 with all three techniques. The imaging findings of osteoid osteoma and the ability of X-ray, CT, and MRI in demonstrating the nidus and the surrounding reaction were analyzed. Results The imaging manifestations of osteoid osteoma revealed a circular or oval nidus with different bone sclerosis around the nidus. The diameters ranged from 0.4 cm to 1.7 cm, with the average of 9.7 cm. There were also soft tissue and bone morrow edema around the nidus or distinct effusion of joint on MR imaging in all 10 cases. Among 48 cases, only 37 cases showed nidus on plane film. All 32 cases with CT scanning showed nidus. The display ratios of nidus were 77% for X-ray and 100% for CT, respectively. 10 cases with MR imaging could be diagnosed correctly. But the nidus could be affirmed in only 8 cases, and the nidus was affirmed by comparing with plane film or CT in the other 2 cases. Conclusion Nidus is the key in diagnosing the osteoid osteoma correctly. Plane film is still an important checking method for osteoid osteoma. CT scan is the best method to demonstrate the nidus. MRI can demonstrate the soft tissue and bone morrow edema around the nidus sensitively, but probably lead to an incorrect diagnosis. Combining with X-ray or CT, MRI can make an accurate diagnosis.

Objective To probe the imaging diagnostic characteristics of skull base-type pituitary adenoma (SBPA). Methods CT, conventional MRI, dynamic MRI, and pathological data of 16 patients with SBPA were analyzed. The manifestations of both CT and conventional MRI, the dynamic time-signal curve, time of peak enhancement, and average enhancement rate were compared between SBPA in the 16 patients and chordoma of the skull base (CSB) in another 9 patients. Results The CT appearances of both tumors were quite similar, offering no differential value. Both tumors were slightly hypointense on T 1 weighted images, but SBPA was mildly hyperintense and CSB was markedly hyperintense on T 2 weighted images. The T 2 weighted signal intensity between both tumors differed significantly (P5 min, (40?5) /min for CSB, respectively (P

Twenty eight patients with multiple organ dysfunction syndrome (MODS) underwent continuous venovenous hemofiltration (CVVH)in ICU from June 2003 to June 2008, including 13 cases treated with predilution mode and 15 with postdilution mode. The changes of oxygenate index( PaO2/FiO2 )during CVVH were retrospectively analyzed. The total case fatality rate of this group of patients was 46%(13/28). There was a significant increase in PaO2/FiO2 of 28 cases during the first 48 h of CVVH (P ＜0. 05);the levels of PaO2/FiO2 in predilution group had increased significantly within 48 h during CVVH (P＜0. 05), while those in postdilution group had not significantly changed (P ＞ 0. 05). There was a significant increase in Pa02/FiO2 for the survival patients during the first 48h CVVH( P ＜ 0. 05 ), while no significantly change in the fatal cases(P ＞0. 05 ). In summary, oxygenate function and outcome of patients with MODS can be improved by CVVH, and predilution may be a more effective mode.