Volume-rendered 3D display of MR angiograms in the diagnosis of cerebral arteriovenous malformations.

PURPOSE: To determine whether application of a volume-rendered display of 3D time-of-flight (TOF) MR angiography could assist the diagnosis of cerebral arteriovenous malformations (AVMs). MATERIAL AND METHODS: Volume-rendered 3D images of postcontrast 3D time-of-flight MR angiography were compared with conventional angiograms in 12 patients. The correlation between the 3D images and the operative findings was also analyzed in 5 patients. RESULTS: The 3D-displayed images showed all of the feeders and drainers in 10 and 9 patients, respectively. In all patients, the nidus was three-dimensionally visualized. In 3 patients with hematomas, the relationship between the hematoma and the AVM was well demonstrated. The 3D images corresponded well with the operative findings in the 5 patients. CONCLUSION: This method is of help in assessing the relationship between the components of an AVM as well as that between an AVM and an associated hematoma.

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.

Diffusion-weighted MRI of the cervical spinal cord using a single-shot fast spin-echo technique: findings in normal subjects and in myelomalacia.

We have implemented a new diffusion-weighted MRI (DWI) sequence based on the single-shot fast spin-echo technique. We hypothesised that this would add information to conventional MRI for diagnosis of lesions of the cervical spinal cord. DWI was performed using a technique in which echo collection after the application of motion-probing gradients was done in the same manner as in the single-shot fast spin-echo technique. We first imaged six healthy volunteers to demonstrate the cervical spinal cord using the sequence. Then we applied the sequence to 12 patients with cervical myelomalacia due to chronic cord compression. The spinal cord was well seen in all subjects without the distortion associated with echo-planar DWI. In the patients, lesions appeared as areas of low- or isointense signal on DWI. Calculated apparent diffusion coefficients of the lesions (3.30+/-0.38x10(-3) mm(2)/s) were significantly higher than those of normal volunteers (2.26+/-0.08x10(-3) mm(2)/s). Increased diffusion in areas of cervical myelomalacia, suggesting irreversible damage, can be detected using this technique.

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.

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

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.

FLAIR MR imaging for diagnosing intracranial meningeal carcinomatosis.

OBJECTIVE: The purpose of this study was to compare unenhanced and contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging with other sequences to visualize meningeal carcinomatosis. MATERIALS AND METHODS: Unenhanced FLAIR images were compared with spin echo T2-weighted and contrast-enhanced FLAIR images in five patients with documented meningeal carcinomatosis and four patients with suspected meningeal carcinomatosis. Comparisons were also made between contrast-enhanced T1-weighted and FLAIR images. RESULTS: In six patients, the unenhanced FLAIR images showed areas of abnormal hyperintensity within the sulci that were not noted on the spin-echo T2-weighted images. In all patients, the contrast-enhanced FLAIR images also showed meningeal enhancement, periventricular enhancement, or both. The contrast-enhanced T1-weighted and FLAIR images were equivalent in their depiction of abnormal enhancement in five of the nine patients; contrast-enhanced FLAIR images were superior in three patients. CONCLUSION: Unenhanced FLAIR images are of more value than spin-echo T2-weighted images for the diagnosis of intracranial meningeal carcinomatosis. Contrast-enhanced FLAIR images can sometimes surpass contrast-enhanced T1-weighted images in their quality.

MR digital subtraction angiography of cerebral arteriovenous malformations.

BACKGROUND AND PURPOSE: Although phase-contrast MR angiography provides some information regarding hemodynamics of cerebral arteriovenous malformations (AVMs), most conventional MR angiographic techniques have not been helpful in this respect. We attempted to determine the value of MR digital subtraction angiography (DSA) in assessing AVM hemodynamics. METHODS: We developed an MR DSA technique by combining rapid thick-section T1-weighted imaging with a bolus injection of contrast material. The temporal resolution was 0.56 to 0.61 seconds per scan. MR DSA images obtained from 14 patients with AVMs were reviewed. Anatomic depiction of each component of the AVM was rated using a four-point grading scale (excellent = 3, good = 2, fair = 1, poor = 0) to compare conventional vs MR angiograms. RESULTS: We were able to obtain serial images in which passage of contrast material was evident within the AVM, although the sequence we used allowed images to be obtained in only one projection. The average score for feeders, nidi, and drainers was 1.6, 2.4, and 2.3, respectively, with an overall average of 2.1. CONCLUSION: The spatial resolution of our technique may fall below the level needed for identification of small vascular components of an AVM. Additionally, the limited slab may restrict application of the technique to assessment of large or very small AVMs. MR DSA, however, can show the hemodynamics of AVMs and may serve as a supplement to conventional MR imaging in the diagnosis of cerebral AVMs.

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.

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.

Pre- and postcontrast FLAIR MR imaging in the diagnosis of intracranial meningeal pathology.

PURPOSE: Few reports address the use of fluid-attenuated inversion-recovery (FLAIR) images of the brain in the diagnosis of extraaxial lesions. Our purpose was to assess the value of FLAIR images, including postcontrast ones, in the diagnosis of intracranial meningeal diseases. METHODS: We reviewed precontrast (n=24) and postcontrast (n=20) FLAIR images obtained from 25 patients with infectious meningitis (n=13), carcinomatous meningitis or dissemination of primary brain tumor (n=7), dural metastasis (n=3), and others (n=2) in comparison with fast spin-echo T2-weighted and postcontrast T1-weighted images. RESULTS: In lesion detectability, precontrast FLAIR images were significantly superior to fast spin-echo T2-weighted images but inferior to postcontrast T1-weighted images. There was no significant difference between postcontrast T1-weighted and FLAIR images. CONCLUSION: Precontrast FLAIR images can substitute for conventional fast spin-echo T2-weighted images. Postcontrast FLAIR images have diagnostic potential equivalent to conventional postcontrast T1-weighted images.

Diffusion-weighted MR imaging of encephalitis.

OBJECTIVE: Our purpose was to evaluate how well diffusion-weighted MR imaging shows viral or bacterial encephalitis in comparison with conventional MR imaging that includes T1- and T2-weighted spin-echo and fluid-attenuated inversion-recovery sequences. CONCLUSION: In nine of the 13 patients examined, diffusion-weighted imaging was superior to other diagnostic imaging sequences (fluid-attenuated inversion-recovery sequences in eight patients and a T2-weighted spin-echo sequence in one patient). Diffusion-weighted imaging can serve as a method of detecting early encephalitic changes.

Fast dynamic MRI of aortic dissection: flow assessment by subsecondal imaging.

PURPOSE: The aim of this study was to evaluate fast dynamic MRI, which consists of a subsecondal MRI sequence combined with a rapid contrast medium infusion technique, in examining clinical cases of aortic dissection. MATERIALS AND METHODS: The subjects consisted of 27 patients with aortic dissection. Turbo-FLASH imaging of the aorta was conducted to obtain 50 image frames within 40 seconds. RESULTS: Recognition of the intimal flap and differentiation of the true channel from the false channel was easily accomplished in all 15 patients with a patent false channel. The entry site was detected in 13 of 15 patients. Differentiation of slow flow from thrombus in the false channel was possible in all 27 cases, and the relationship between the lesion and the main branches of the aortic arch was identified in 26 of 27 cases. CONCLUSION: Fast dynamic MRI may provide a large amount of information that is useful for the diagnosis of aortic dissection.

A new technique of surface anatomy MR scanning of the brain: its application to scalp incision planning.

BACKGROUND AND PURPOSE: Surface anatomy scanning (SAS) is an established technique for demonstrating the brain's surface. We describe our experience in applying SAS with superposition of MR venograms to preoperative scalp incision planning. METHODS: In 16 patients, scalp incision planning was done by placing a water-filled plastic tube at the intended incision site when we performed SAS using half-Fourier single-shot fast spin-echo sequences. Two-dimensional phase-contrast MR angiograms were obtained to demonstrate the cortical veins and then superimposed upon the SAS images. The added images were compared with surgical findings using a four-point grading scale (0 to 3, poor to excellent). RESULTS: In each case, neurosurgeons could easily reach the lesion. Surgical findings correlated well with MR angiogram-added SAS images, with an average score of 2.56. CONCLUSION: Our simple technique is a useful means of preoperatively determining brain surface anatomy and can be used to plan a scalp incision site.

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.

Short communication: MR imaging of fetal brain abnormalities using a HASTE sequence.

HASTE (half-Fourier acquisition single-shot turbo spin echo) is a sequence that enables T2 weighted magnetic resonance (MR) images to be obtained in a few seconds. The purpose of this study was to evaluate the usefulness of this sequence in the diagnosis of fetal cerebral abnormalities. Five fetuses suspected of having cerebral abnormalities on ultrasound examination were studied by MR imaging using the HASTE sequence in utero. We compared the images with post-natal MR images or computed tomography (CT) scans. In four fetuses, the abnormality was diagnosed correctly, and the diagnosis was almost correct in the remaining fetus. This sequence is useful because it provides images of diagnostic quality in a very short scanning time.

[Clinical application of magnetic resonance angiography for coronary arteries: correlation with conventional angiography and evaluation of imaging time].

Magnetic resonance angiography (MRA) of the coronary arteries is a particularly difficult task because of the small size of the vessels and cardio-respiratory motion. The authors describe a method of performing of ultrafast MRA of the coronary arteries with a standard MR system and body coil. Each image was obtained within a single breath hold by "segmented Turbo FLASH" sequences using an electrocardiography gate. Clinical application was performed in 20 patients with ischemic heart disease, and a comparison was made with conventional coronary angiography. The imaging time was shortened significantly by our methods. The diagnosis was made by at least two different images to avoid false positives. The results indicated a good correlation between MRA and conventional angiography.