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Objective To delineate the MR imaging features of intramedullary subependymoma. Methods The MR imaging features of 4 cases of pathologically proved intramedullary subependymomas were analyzed retrospectively and correlated with operative reports, and the differential diagnosis was discussed. Results MR appearances of intramedullary subependymoma were as follows: (1) Intramedullary subependymoma often involved the cervical region or the extensive portions of the cervical and thoracic cord in 3 out of 4 cases, mainly affected adults, and was eccentric within the spinal cord. The tumor was in the thoracic-lumbar cord in 1 case. (2) They were heterogeneously hypointense relative to the normal spinal cord on T 1-weighted images and hyperintense on T 2-weighted images, occasionally with hemorrhagic foci (2 cases). (3) No enhancement or minimal enhancement was revealed on T 1-weighted images following Gd-DTPA administration (3 out of 4). Conclusion Intramedullary subependymoma are best delineated by MR imaging. The diagnosis of intramedullary subependymoma should be considered when above findings are confronted.

Objective To investigate the applicative value in stages of pre-infarction period using dynamic perfusion CT. Methods Dynamic perfusion CT was performed in 32 cases of cerebral hypoperfusion. The ratios of side-to-side were measured at hypoperfusion areas in the regional cerebral ischemia. The stages of pre-infarction period were made as the following: (Ⅰ 1) TTP was delayed, MTT, rCBF and rCBV were normal; (Ⅰ 2) TTP and MTT were delayed, rCBF was normal, and rCBV was normal or slightly increased; (Ⅱ 1) TTP and MTT were delayed, rCBF was decreased, and rCBV was normal or slightly decreased; (Ⅱ 2) TTP and MTT were delayed, rCBF and rCBV were decreased. Results There were 4 cases in stage Ⅰ 1. Regional hypoperfusion was revealed only by TTP map. The mean ratios of rCBF, rCBV, MTT, and TTP were 1.00, 1.00, 1.00, and 1.30, respectively. In stage Ⅰ 2, the areas of delayed TTP and MTT were found in all 13 cases. The rCBF and rCBV maps appeared normal in 8 cases. Another 5 cases showed normal rCBF and slightly increased rCBV areas. The mean ratios of rCBF, rCBV, MTT, and TTP were 1.00, 1.03, 1.38, and 1.30, respectively. In stage Ⅱ 1, the areas of delayed TTP and MTT were revealed in all 8 cases. The depiction of decreased rCBF was also found in 8 cases. The areas of decreased rCBV were showed in 5 cases, and normal rCBV maps were revealed in 3. The mean ratios of rCBF, rCBV, MTT, and TTP were 0.56, 0.94, 1.49, and 1.47, respectively. In stage Ⅱ 2, the areas of delayed TTP and MTT were revealed in all 4 cases, in whom depiction of decreased rCBF and rCBV was also found. The mean ratios of rCBF, rCBV, MTT, and TTP were 0.42, 0.59, 1.57, and 1.55, respectively. Conclusion CT perfusion imaging and its parameters' analysis may play an increasing role to delineate the depiction of cerebral hypoperfusion in pre-infarction period. Analyzing the relationship of rCBF, rCBV, MTT, and TTP is very helpful to know the status of the capillary vessels in regional cerebral hypoperfusion area and to provide functional information with our stages of pre-infarction period.

Objective To preliminarily compare accuracy of magnetic resonance elastography (MRE) and T2WI in assessing stiffness of tissue.Methods Agar gel phantoms of 23 different concentrations ranging from 0.8％-3.0％ were produced.All the phantoms were examined with MRE and T2 map scanning respectively.After the raw images were processed by using local wavelength estimation (LEF),shear modulus of scan slice was measured,and T2 value of the same slice was measured with GE ADW4.3 workstation.Pearson correlation analysis was used to test the correlation between shear modulus and agar concentration,as well as T2 value and concentration.Rank sum test was used to compare the correlation coefficients of them.Results All the shear modulus and T2 values of the phantoms were successfully obtained,which were (49.1 ± 23.5) kPa and (57.8 ± 21.8) ms respectively.Shear modulus was positively correlated with concentration of agar gel(r1 =0.985,r1 2 =0.970,P ＜ 0.01),while T2 value was negatively correlated with concentration of agar gel (r2 =-0.901,r22 =0.812,P ＜ 0.01).The differences of these two correlation coefficients were statistically significant (Z =5.459,P ＜ 0.01).Conclusion MRE is more accurate to reflect stiffness of tissues relative to T2WI,and shows great clinical prospect.

Objective To intruduce a method of making cerebral perfusion mapping and measurement using dynamic CT with a personal computer. Methods We generated the cerebral perfusion mapping and measurement from a series dynamic CT images with a personal computer. The theoretic basis of our technique is central volume principle. The application software was made using visual C++ language with Windows 98 platform. Results This method was applied to a case of transient ischemic attack (TIA). The cerebral perfusion mapping contributed to display the abnormal area of ischemia, which showed as normal imaging appearances in routine CT and MR images. Conclusion Personal computer aided mapping and measurement of cerebral perfusion with dynamic CT is a simple and accessible technique for delineating the hemodynamic response, including abnormal regional cerebral blood flow, blood volume, mean transit time, and time to peak in cases of hyperacute ischemic stroke which was viewed as normal imaging findings in routine CT and MR examination. This method is more suitable to examine emergency cases than MR perfusion imaging and may be used in any facility where CT scanner and personal computer are available.

Objective To study the MRI findings of spinal hemangioblastomas.Methods The MRI findings of spinal hemangioblastomas proved pathologically in 29 cases (20 males,9 females) were retrospectively reviewed.Results The lesions were single in 12 cases (41.4%) and multiple in 17 cases(58.6%).Seven patients combined with intracranial hemangioblastomas.On unenhanced MRI,36 tumors were isointense on T 1WI and T 2WI,16 were mixed iso-hypointense on T 1WI and mixed iso-hyperintense on T 2WI,one was hypointense on T 1WI and hyperintense on T 2WI.Small hemangioblastomas tended to be isointense on T 1WI and T 2WI.After contrast injection,all tumors enhanced markedly and homogenously with clear borders.21 tumors in 17 patients had associated vascular flow voids on T 2WI.40 tumors in 27 patients were associated with syringes or cysts.Conclusion Hemangioblastomas of the spinal cord are often multiple and in company with intracranial hemangioblastomas.The marked contrast enhancements with clear borders and associated vascular flow voids are the most important signs on MRI.

Objective To study the imaging findings of cerebral venous sinus occlusion and to improve the knowledge of this disease.Methods CT,MRI and DSA data in thirty six cases with cerebral venous sinous occlusion were retrospectively reviewed.There were 15 male and 21 female,ranged in age from 23 to 59 years old.Results On T_1WI and T_2WI,abnormal signals in cerebral parenchyma were found in 26 cases,of that there were brain hemorrhage with abnromal long T_1 and long T_2 signal in 16 cases,only abnromal long T_1 and long T_2 signal in 6 cases,cerebral ventrical enlargment in 4 cases and brain swelling in 4 cases.The abnormal venous enhancement was found in 25 cases on contrast-enhanced MRI.On CT scan,low density in cerebral parenchyma was found in 10 cases,it might be edema or ischemia,astime goes by,the density of cerebral venous sinus became slightly high density to isodensity.DSA showed dural sinus occlusion includingsuperior sagittal sinus in 15 cases,transverse sinus in 8 cases,sigmoid sinus in 7 cases,straight sinus in 4 cases and inferior sagittal sinus in 2 cases.Conclusion The venous sinus occlusive disease is distinctively different from arterial occlusive disease.CT and MR imaging is very important in diagnosing the cerebral venous sinus occlusive disease,but DSA is still the gold standard.

Objective To establish a stable and reproducible experimental method of dynamic CT perfusion imaging in measurements of perihematomal cerebral blood flow after intracerebral hemorrhage (ICH) in rats, and to study its validation. Methods Seventy male Sprague-Dawley rats were randomly divided into ICH groups and sham-operated groups. ICH was produced by microinjection of 40 ?l fresh autologous blood or saline into the right caudatum. Dynamic CT perfusion imaging in measurements of regional cerebral blood flow adjacent to hematomas was performed. Then, rats were sacrificed, and the TTC stain and histopathological examination were carried out. The ratios of side-to-side were measured at the regions around the hematomas by personal computer aided mapping. Results The gradient of perihematomal hypoperfusion was revealed by regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) maps in ICH groups. The alternation of rCBF around the hematomas were fluctuated, and rCBF reduction was most pronounced at 1 hour after ICH, then, the rCBF gradually returned, and returned to the peaks at 6 hours and 24 hours after ICH respectively. TTC stain did not show infarction around the hematoma. Histopathological study demonstrated there was a transitional zone between ICH and the normal brain tissue, and the astrocytic swelling and neuronal degeneration were observed in the peri-ICH regions. The inflammatory cell infiltration and capillaries hyperplasia were also seen around the ICH. Conclusion The method of dynamic CT perfusion imaging in measurements of perihematomal cerebral blood flow after intracerebral hemorrhage in rats is stable and accurate. Perfusion CT and its parameter analysis may play an increasing role in delineating the hypoperfusion around hematomas. The experimental method is suitable and validated to the study of secondly injury after ICH in vivo.

Objective To summarize the clinical and imaging characteristics of primary Rosai-Dorfman disease (RDD)in central nervous system in order to understand well its features and improve the diagnosis.Methods The clinical and imaging features in 3 patients with RDD in CNS proved by pathology were retrospectively analyzed in combination with the related literatures.Results The lesions in 2 patients occurred in brain and other lesion in 1 occurred outside the brain.Iso-or slight hyperintensity on T1 WI and marked enhancement of the lesion were found.Single lesion was found in 2 patients near the dura mater and located near the superior sagittal sinus or cervical spinal cord.Multiple lesions in 1 patient were located in the lateral ventricle.Conclusion It’s suggested that single or multiple lesions in dural or spinal meninges located in the midline or near the intracephalic venous system would be considered as RDD in CNS.

Objective 　To evaluate the clinical measurement of cerebral perfusion by dynamic CT. Methods　 Thirteen normal adults were examined by dynamic CT for the measurement of cerebral blood flow (CBF). Another dynamic CT scans with the measurement of CBF were performed separately to rule out cerebral ischemia in 5 cases and secondary Parkinson disease in 2. Results　 Normal cerebral cortical perfusion was measured at 59.3～96.8 ml*min-1*100g-1 with the　mean value 76.2 ml*min-1*100g-1. Normal white matter perfusion was measured at 27.1～43.1 ml*min-1*100g-1 with the mean value 33.9 ml*min-1*100g-1. In 5 cases of suspending cerebral ischemia, one showed increase of CBF and 4 presented decrease of CBF. In 2 cases of suspending secondary Parkinson disease, one appeared decrease of CBF and other one was normal. Conclusion　 Dynamic CT scan with the measurement of CBF can demonstrate the hemodynamic status of normal brain and pathological lesion. Combined with routine CT scan, measurement of cerebral perfusion by dynamic CT is an ideal method to show the morphological and functional changes of brain tissue simultaneously.