Fluid-attenuated inversion recovery and diffusion- and perfusion-weighted MRI abnormalities in 117 consecutive patients with stroke symptoms.

BACKGROUND AND PURPOSE: Diffusion-weighted MRI (DWI) is highly sensitive to early cerebral ischemia, but its dependence on lesion location, acuity, and etiology remains unknown. Furthermore, although a marked perfusion-weighted MRI (PWI)-DWI mismatch may exist in a subset of acute strokes, the frequency and distribution of these mismatches have never been methodically characterized in an unselected population. To address these 2 issues, we evaluated echo-planar imaging in 117 consecutive patients with signs and symptoms of acute stroke. METHODS: Clinical diagnoses were determined by chart review. Fluid-attenuated inversion recovery (FLAIR), DWI, and PWI sequences were scored for lesion acuity, neuroanatomy, and vascular territory. Lesion and PWI-DWI mismatch volumes were determined by image analysis. RESULTS: DWI was more sensitive than was FLAIR for the detection of stroke for all subtypes in all anatomic distributions and at all tested time intervals. Although DWI exhibited its greatest benefit over FLAIR during the first 6 hours, it was still superior to FLAIR even after 24 hours. PWI abnormalities were detected in 49% of patients with DWI abnormalities. In the majority of these cases, the PWI-DWI mismatch was substantially larger than the DWI lesion itself. Both the largest DWI lesion volumes and the largest mismatch volumes occurred in patients with carotid disease. CONCLUSIONS: DWI nearly doubles the likelihood of detecting acute ischemic stroke lesions compared with FLAIR for all etiologies and in all anatomic locations. In the hyperacute period (0 to 6 hours), DWI more than triples the likelihood of acute-stroke detection over FLAIR. PWI reveals a measurable mismatch compared with DWI nearly 50% of the time; and in more than half of these patients, the ratio of the volume of the PWI lesion to the DWI lesion is several times larger than the core ischemic lesion itself. In the final analysis, approximately one fourth of all stroke patients present with a large volume of potentially salvageable tissue at risk for infarction.

Single-and dual-energy CT with monochromatic synchrotron x-rays.

We explored the potential for clinical research of computed tomography (CT) with monochromatic x-rays using the preclinical multiple energy computed tomography (MECT) system at the National Synchrotron Light Source. MECT has a fixed, horizontal fan beam with a subject apparatus rotating about a vertical axis; it will be used for imaging the human head and neck. Two CdWO4-photodiode array detectors with different spatial resolutions were used. A 10.5 cm diameter acrylic phantom was imaged with MECT at 43 keV and with a conventional CT (CCT) at 80 kVp: spatial resolution approximately equal to 6.5 line pairs (lp)/cm for both; slice height, 2.6 mm for MECT against 3.0 mm for CCT; surface dose, 3.1 cGy for MECT against 2.0 cGy for CCT. The resultant image noise was 1.5 HU for MECT against 3 HU for CCT. Computer simulations of the same images with more precisely matched spatial resolution, slice height and dose indicated an image-noise ratio of 1.4:1.0 for CCT against MECT. A 13.5 cm diameter acrylic phantom imaged with MECT at approximately 0.1 keV above the iodine K edge and with CCT showed, for a 240 micrograms I ml-1 solution, an image contrast of 26 HU for MECT and 13 and 9 HU for the 80 and 100 kVp CCT, respectively. The corresponding numbers from computer simulation of the same images were 26, 12, and 9 HU, respectively. MECT's potential for use in clinical research is discussed.

Glucose metabolic changes in nontumoral brain tissue of patients with brain tumor following radiotherapy: a preliminary study.

PURPOSE: Our goal was to measure the effect of radiotherapy on the brain glucose metabolism of tumoral and nontumoral tissue of patients with brain malignancies. METHOD: Fifteen patients with primary or metastatic brain tumors were studied with 2-deoxy-2-[18F]fluoro-D-glucose and PET prior to radiotherapy, and nine of them were rescanned 1 week after completing radiotherapy. RESULTS: Brain metabolism in patients (all brain regions except for tumoral and edematous tissue) was lower than that of matched controls (34.0 +/- 8.3 vs. 46.5 +/- 6.4 mumol/100 g/min; p < or = 0.0001). Five of the nine patients retested after radiotherapy showed decrements in tumor metabolism (47 +/- 10%; p < or = 0.05) and increases in brain metabolism (10 +/- 4%; p < or = 0.004), and the other four showed no changes in tumor or in brain metabolism. Radiotherapy-induced changes in tumor metabolism were negatively correlated with changes in brain metabolism (r = 0.85, p < or = 0.004), but not with changes in tumor volume (assessed with MR images). CONCLUSION: The study indicates that radiotherapy-induced increases in metabolism of nontumoral tissue are secondary to decreased tumor metabolic activity and not just due to volume reduction.

Functional importance of ventricular enlargement and cortical atrophy in healthy subjects and alcoholics as assessed with PET, MR imaging, and neuropsychologic testing.

The authors assessed the relationship between ventricular enlargement, cortical atrophy, regional brain glucose metabolism, and neuropsychologic performance in 10 alcoholics and 10 control subjects. Regional brain glucose metabolism was measured with fluorine-18 fluorodeoxyglucose (FDG) and positron emission tomography (PET). Cortical atrophy and ventricular size were evaluated quantitatively with magnetic resonance (MR) imaging. Alcoholics had decreased brain glucose metabolism and more cortical atrophy but did not have significantly greater ventricular size than did control subjects. The degree of ventricular enlargement and of cortical atrophy was associated with decreased metabolism predominantly in the frontal cortices and subcortical structures in both alcoholics and control subjects. There were no significant correlations between neuropsychologic performance and MR imaging structural changes, whereas various subtest scores were significantly correlated with frontal lobe metabolism. These data show that F-18 FDG PET is a sensitive technique for detecting early functional changes in the brain due to alcohol and/or aging before structural changes can be detected with MR imaging.

Cerebral venous thrombosis in a child with iron deficiency anemia and thrombocytosis.

We describe a 22-month-old boy with iron deficiency anemia and reactive thrombocytosis who developed vomiting, headache, mental status changes, and seizures. Computed tomography showed infarction of the basal ganglia and thalami. Magnetic resonance imaging revealed cerebral venous thrombosis, delineated the extent of the vascular and associated parenchymal involvement, showed the infarcts to be hemorrhagic (a finding not imaged by computed tomography due to our patient's depressed hemoglobin level), and obviated the need for invasive angiography.

Lyme neuroborreliosis: central nervous system manifestations.

We evaluated 85 patients with serologic evidence of Borrelia burgdorferi infection. Manifestations included encephalopathy (41), neuropathy (27), meningitis (2), multiple sclerosis (MS) (6), and psychiatric disorders (3). We performed lumbar punctures in 53, brain MRI in 33, and evoked potentials (EPs) in 33. Only patients with an MS-like illness had abnormal EPs, elevated IgG index, and oligoclonal bands in the cerebrospinal fluid. Twelve of 18 patients with encephalopathy, meningitis, or focal CNS disease had evidence of intrathecal synthesis of anti-B burgdorferi antibody, compared with no patients with either MS-like or psychiatric illnesses, and only 2/24 patients with neuropathy. MRIs were abnormal in 7/17 patients with encephalopathy, 5/6 patients with an MS-like illness, and no others. We conclude that (1) intrathecal concentration of specific antibody is a useful marker of CNS B burgdorferi infection; (2) Lyme disease causes an encephalopathy, probably due to infection of the CNS; (3) MS patients with serum immunoreactivity against B burgdorferi lack evidence of CNS infection with this organism.

Multilevel thoracic disk herniations: CT and MR studies.

Thoracic disk herniation is a disorder that can present clinically perplexing problems for physicians. The true incidence of thoracic disk herniation is difficult to assess with various authors reporting an incidence ranging between 0.15 and 1.8% of all disk herniations. Multiple thoracic disk herniations are rare and, to the best of our knowledge, have received little attention in the orthopedic, neurosurgical, and radiological literature. A retrospective review of 680 myelograms performed at our institution was carried out and only three cases of multilevel thoracic disk herniations were found. We analyze these cases, discuss the relative value of the imaging modalities used in their diagnosis, and review the literature dealing with this interesting disorder.