Objective To explore the value of three-dimensional constructive inference in steady state sequence (3D-CISS se-quence)in case of midbrain aqueduct obstruction.Methods 46 cases with midbrain aqueduct obstruction were scanned with FLASH T1 WI、TSE T2 WI and 3D-CISS sequence at 3.0T superconductive MR scanner.The original images of the 3D-CISS sequence were reconstructed.The images of three sequences showing midbrain aqueduct obstruction were observed and analyzed.Results The de-tection rate of the midbrain aqueduct obstruction was 13% 、71.7% and 100% in FLASH T1 WI、TSE T2 WI and 3D-CISS sequence, respectively.The difference between the three sequences were significant (P <0.01 67).Conclusion 3D-CISS sequence shows mid-brain aqueduct obstruction more accurately.

Objective To observe the feasibility of PC-cine MRI for estimating the cerebrospinal fluid circulation of fistula after endoscopic third ventriculostomy (ETV)in obstructive hydrocephalus.Methods 25 cases with obstructive hydrocephalus were scanned with routine MR protocol and PC-cine sequence before and after ETV.Qualitative and quantitative evaluation of the cerebro-spinal fluid flow through the fistula were performed and the results were compared with 25 cases of healthy volunteers.Results One week after operation,the cerebrospinal fluid flow through the fistula showed obviously positive in 23 patients,while negative in the other 2 patients,and the waveform was similar to that in the normal midbrain aqueduct.The outflow and inflow peak velocity of the cerebrospinal fluid through the fistula were lower than that in normal midbrain aqueduct(P<0.05),while the quantity of outflow,inflow and netflow were much higher(P<0.05).6 patients showed ventricular narrowing one week after operation and 17 cases maintained the same finding.During follow-up of half year,the ventricular size still showed no obvious narrowing in 14 patients.Ventricular expanding was observed in 2 post-operative patients.Conclusion PC-cine MRI can provide intuitive and reliable evidences in evaluation of ETV for obstructive hydrocephalus.

Objective:To investigate the CT, magnetic resonance imaging(MRI) and clinicopathological cha-racteristics of perivascular epithelioid cell tumors (PEComas) in children, and improve the diagnostic accuracy of PEComas.Methods:The CT, MRI and clinicopathological characteristics of 6 children confirmed with PEComas by histopathology caming from Beijing Children′s Hospital, Capital Medical University during March 2019 and April 2022 were retrospectively analyzed.Results:The patients aged from 1.7 to 11.9 years old (with mean age of 7.6 years old). The male to female ratio was 1∶2.Of the 6 solitary tumors identified, 2 cases were found in the kidney, 2 cases in the abdominal cavity, 1 case in the pelvic cavity, and 1 case in the groin.The solitary tumors had well-defined borders.Five solitary tumors were shaped like an ellipse and 1 solitary tumor was multinodular-shaped.Lace-like or nodular changes were observed at tumor margins(3 cases). The maximum diameters of the tumors ranged from 4.8 to 15.9 cm (mean value: 9.3 cm). Five tumors showed peripheral invasion and 2 cases had lymph node metastasis.Two patients were complicated with tuberous sclerosis.One case suffered from tumor recurrence after operation.The tumors (6 cases) were isodensity or low density on the plain CT scan, and gradual heterogeneous enhancement was observed after injection of the contrast agent.A majority of the tumors had tortuous (5 cases) and thickened blood vessels inside, and a few of them (2 cases) underwent gravel-like calcification.Patch-like or nodule-like high signal intensity could be seen in the center of the tumors (3 cases) on MRI T1WI and T2WI, while the peripheral part of the lesions showed iso-signal intensity (equal to muscle). On diffusion weighted imaging(DWI) (b=800 s/mm 2), the lesions exhibited restricted diffusion at the peripheral part with significant enhancement, and iso-signal intensity at the central part with none or slight enhancement.Histological classification results revealed that 1 of 6 cases was a benign PEComa and 5 cases were malignant PEComas.The expression rates of Melan-A and SMA were 100.0% and 83.3%, respectively. Conclusions:The CT, MRI and pathological manifestations of PEComas in children have some distinct features.PEComas are often an oval-like mass with clear borders and nodular margins in the abdominal and pelvic cavity, and tortuous and thickened blood vessels can be seen in the tumor.The periphery of the tumor is the main region to be enhanced by the contrast agent.Local invasion and distant metastasis can be observed.Most of the tumors are malignant in pathology.Both melanocyte and muscle cell markers can be found in the expression of immunohistochemistry.