Shichiro Katase

Diffusion-weighted MRI of subdural and epidural empyemas

We reviewed diffusion-weighted images (DWI) from eight patients with subdural and four with epidural empyemas to assess the possibility of differentiating between these lesions by DWI. The signal intensities of the empyemas on DWI, and maps of the apparent diffusion coefficient (ADC) were analysed in seven patients. In seven of the eight patients with subdural empyema, the lesions appeared as areas of high signal. The ADC maps confirmed that these areas were the result of restricted diffusion. (In the remaining patient, the lesion showed a mixture of high and low signal.) The epidural empyemas contained areas of low signal in all four patients; part of the empyema was isointense or gave high signal in two. DWI may be an adjunct to conventional sequences for differentiating between subdural and epidural empyemas.

Mri of Influenza encephalopathy in children : Value of diffusion-weighted imaging

PURPOSE Our purpose was to describe the MR findings of influenza encephalopathy and assess the value of diffusion-weighted imaging for its diagnosis. METHOD We examined a total of five patients diagnosed as having influenza encephalopathy or encephalitis by MRI, including diffusion-weighted imaging. We analyzed the conventional images and compared them with diffusion-weighted images. RESULTS Abnormally hyperintense lesions of varying extent and location were noted on T2-weighted and fluid-attenuated inversion recovery images in the cortex and adjacent white matter in every case. They showed no contrast enhancement. Diffusion-weighted imaging demonstrated the lesions as areas of restricted proton diffusion more clearly than conventional imaging. CONCLUSION Influenza encephalopathy is depicted as areas of T2 elongation having a rather nonspecific distribution. Diffusion-weighted imaging can demonstrate the lesions sensitively and serve as a valuable adjunct to conventional MRI.

Application of multi-detector row helical scanning to postmyelographic CT

Abstract. The advent of a multi-detector row helical CT has made it possible to attain images over a broader area with good spatial resolution. We assessed whether postmyelographic CT scans obtained using this system provided more information than conventional imaging techniques. Postmyelographic CT scans were preoperatively obtained in 46 patients using a multi-detector row helical CT system. Reconstructed images in the sagittal and coronal planes in all patients and curved reformation images along the dural sac in 37 patients were compared with myelograms and conventional postmyelographic CT scans. In 34 patients comparison was also made with MR images. The multi-detector row CT images demonstrated deformities of the dural sac more clearly than the other modalities in 39 of the 46 patients. They also provided the best visualization of nerve root abnormalities in 24 of the 46 patients and clearly revealed the presence of spurs in all 22 patients with spinal canal stenosis. Postmyelographic CT scans made using a multi-detector row helical CT system provide more information on the dural sac, nerve sleeves, and their contents than other imaging techniques.

Preliminary evaluation of volume-rendered three-dimensional display of time-of-flight MR angiography in the diagnosis of intracranial aneurysms

Abstract We assessed the value of the volume-rendering method of displaying images of three-dimensional (3D) time-of-flight MR angiography (MRA) in the diagnosis of intracranial aneurysms. We obtained three-dimensional volume-rendered MRA from 21 patients with intracranial aneurysms. The images were evaluated in comparison with maximum-intensity-projection images (in 21 patients), conventional angiograms (in 21 ) and CT angiography (in nine). In 17 patients, 3D volume-rendered images were thought to show morphological features most clearly. They were superior to the other methods for demonstrating the precise location of the aneurysm in three patients and in showing the shape of the bleb in another three. 3D volume-rendered MRA can be effectively added to conventional imaging techniques for diagnosis of intracranial aneurysms.

Visualization of extracranial-intracranial bypass using multidetector-row helical computed tomography angiography.

Purpose The advent of multidetector-row computed tomography (MDCT) has enabled images with good spatial resolution to be obtained over a wide range in a short scanning time. Our purpose was to determine whether CT angiography using the MDCT system could effectively depict extracranial–intracranial (EC–IC) bypass routes. Method Helical CT angiography was performed using an MDCT scanner in 12 patients who had undergone EC–IC bypass surgery: 10 patients had undergone superficial temporal artery–middle cerebral artery (MCA) anastomosis, 1 patient had undergone an encephaloduroarteriosynangiosis procedure for the treatment of moyamoya disease, and 1 patient had undergone an external carotid artery–MCA anastomosis using a graft. The resulting CT angiograms were visually evaluated for their depiction of the EC–IC bypass route. Conventional angiograms were available for comparison in all 12 patients. Results The EC–IC bypass was visualized to be patent at the site of anastomosis in all 12 patients. Branches of the MCA secondary or more to those connected to a donor artery were demonstrated in 9 patients, whereas MCA branches immediately distal to the anastomosis were demonstrated in 3 patients. The CT angiography findings corresponded well with the conventional angiography findings in all patients. Conclusion Helical CT angiography using the MDCT technique is an effective method for visualizing EC–IC bypass routes.

Diffusion-weighted MR imaging of Carmofur-induced leukoencephalopathy

Carmofur (1-hexylcarbamyl-5-fluorouracil), a derivative of 5-fluorouracil (5-FU), has been widely used in Japan as a postoperative adjuvant chemotherapy agent for colorectal and breast cancer. Periventricular hyperintensity on T2-weighted MR images in carmofur-induced leukoencephalopathy confront the physician with a broad range of differential diagnoses. We describe two cases of carmofur-induced leukoencephalopathy in which diffusion-weighted MR imaging revealed periventricular hyperintensity. We compared their findings with those of age-related periventricular hyperintensity in five patients and found discrepancies in signal intensity of periventricular areas. Our results suggest that diffusion-weighted MR imaging may be useful to differentiate carmofur-induced leukoencephalopathy from age-related periventricular hyperintensity.

MR digital subtraction angiography in the diagnosis of meningiomas.

OBJECTIVE MR digital subtraction angiography (DSA) is a technique for demonstrating the vasculature combining a rapid two-dimensional T1-weighted sequence with a bolus injection of gadolinium. We attempted to determine its contribution to the diagnosis of intracranial meningiomas. METHODS AND PATIENTS MR DSA was performed in 18 patients with meningioma as well as in 28 patients with other tumors. The findings were analyzed regarding demonstration of tumor stain and tumor-related vessels. RESULTS All meningiomas except one were visualized as a homogeneous and intense stain. Feeding arteries were visualized in 2 patients, and draining or abnormal veins in three. In 21 of the 28 patients with other tumors, tumor stains of varying degrees were demonstrated. CONCLUSION MR DSA can serve as an adjunct to routine MR imaging, because it enables assessment of the hemodynamics of meningiomas and facilitates its differential diagnosis from other tumors.

Cerebral perfusion MRI with arterial spin labeling technique at 0.5 Tesla.

PURPOSE Our aim was to evaluate the feasibility of cerebral perfusion MRI using an arterial spin labeling technique at 0.5 T. METHOD We performed perfusion imaging with a flow-sensitive alternating inversion recovery (FAIR) sequence in a total of 37 patients with cerebral infarction. RESULTS FAIR perfusion images demonstrated areas of pathological perfusion corresponding (13 patients) or not corresponding (15 patients) to the infarcted area on MR images. Among 19 patients in whom comparison between FAIR perfusion imaging and regional cerebral blood flow single photon emission CT was available, the two studies correlated well in 15 patients. CONCLUSION Our results indicate that the FAIR technique allows reliable cerebral perfusion imaging at 0.5 T.

MR Myelography of Sacral Meningeal Cysts

Purpose: To describe the findings of sacral meningeal cysts (SMCs) on MR myelography and assess its value for the diagnosis of SMCs. Material and Methods: We evaluated the MR images and MR myelograms obtained from 10 patients with SMC. MR myelograms were obtained using a 2D or 3D single-shot fast spin-echo sequence. In 5 patients, X-ray myelograms and postmyelographic CT images were compared with the MR myelograms. Results: A total of 33 SMCs were diagnosed within the spinal canal and/or sacral foramen. MR myelograms clearly revealed each cyst as a well-defined mass showing hyperintensity (10 cysts) or isointensity (23 cysts) compared to cerebrospinal fluid. MR myelograms demonstrated SMCs better than X-ray myelograms and postmyelographic CT images in 3 of the 5 patients. Conclusion: MR myelography can be an adjunct to conventional imaging techniques when surgical treatment is indicated, because it can precisely delineate the extent of SMCs.

MR-angiogram-added surface anatomy scanning of superficial cerebral arteriovenous malformations.

Abstract.Our purpose was to evaluate the utility of surface anatomy scanning (SAS) of the brain with superimposition of MR angiograms in the diagnosis and presurgical planning of superficial cerebral arteriovenous malformations (AVMs). We performed SAS in 15 patients with superficial cerebral AVMs. Two-dimensional phase-contrast MR angiograms were then obtained in the same section and superimposed on the SAS images. The images were assessed regarding the visualization of each AVM component using a four-point grading scale (3=excellent to 0=poor). In 13 of the patients, the assessment was made comparing with conventional angiograms. The images were also compared with the surgical findings in 5 patients. The added images agreed well with the angiographic findings and demonstrated the relationships between the AVM components and the adjacent brain surface. The average scores of the feeder(s), nidus, and drainer(s) were 2.27, 2.33, and 2.67, respectively. The surgical findings also correlated well with the added images. Our technique can noninvasively demonstrate superficial AVMs along with the brain surface and provide information useful for planning surgery.