MRI findings in eastern equine encephalitis: the "parenthesis" sign.

Two patients with eastern equine encephalitis (EEE) presented to a tertiary referral center. Both subjects' brain magnetic resonance imaging showed T2/FLAIR (fluid-attenuated inversion recovery) hyperintensities including linear areas of hyperintensity in the external and internal capsules with sparing of the lentiform nuclei. Single case reports of imaging findings in EEE exist with nonspecific patterns of abnormality. We propose that this "( ) parentheses sign" on T2 or FLAIR imaging may distinguish EEE from other processes.

Improvements in lumbar spine MRI at 3 T using parallel transmission.

OBJECTIVE: Parallel transmission MRI at 3 T improves image quality by reducing dielectric effects with radiofrequency shimming. The purpose of this study was to determine whether parallel transmission MRI improves signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in lumbar spine MRI at 3 T. MATERIALS AND METHODS: Ten healthy volunteers underwent T1-weighted MRI and nine healthy volunteers underwent T2-weighted MRI of the lumbar spine. Sagittal and axial T1- and T2-weighted images were acquired using parallel transmission MRI and conventional MRI. The percentage improvements in SNR and CNR were calculated, and statistical significance was determined using a two-tailed Student t test with p < 0.05 for significance. RESULTS: The CNR and SNR showed statistically significant improvements at all levels of the lumbar spine except SNR at T11 on axial T2-weighted imaging. For sagittal T1-weighted imaging, the average improvement with parallel transmission MRI was 53% in CNR and 19% in SNR. For axial T1-weighted imaging, the average improvement was 48% in CNR and 23% in SNR. For sagittal T2-weighted imaging, the average CNR improvement was 38% and the average SNR improvement, 20%. For axial T2-weighted scans, the average percentage improvement in CNR was greater than 100% and the average SNR improvement was 18% with parallel transmission MRI. CONCLUSION: The parallel transmission sequence improves image quality of lumbar spine MRI at 3 T, which is quantitatively supported by statistically significant improvements in SNR and CNR.

The misinterpretation rates of radiology residents on emergent neuroradiology magnetic resonance (MR) angiogram studies: correlation with level of residency training.

The purpose of this study was to determine the discrepancy rates of radiology residents interpreting emergent neck and Circle of Willis magnetic resonance angiography (MRA) studies and to detect any adverse clinical outcomes. Three hundred seventeen MRA studies given preliminary reading by radiology residents were retrospectively reviewed over a 2-year period. Discrepancies were classified as either false negatives (failure to diagnose abnormalities) or false positives (misinterpreting normal scans as abnormal). The overall discrepancy rate was 12.1% for Circle of Willis MRA and 7.9% for neck MRA. Fourth-year residents had the lowest discrepancy rates (7.7%), but this was not statistically significant. The most common misses were stenosis greater than 70% (n = 9) and aneurysm (n = 12). No adverse clinical outcome was detected mainly due to rapid turnaround time for final reporting.

Discrepancy rates of on-call radiology residents' interpretations of CT angiography studies of the neck and circle of Willis.

OBJECTIVE: The purpose of our study was to determine the discrepancy rates of radiology residents' interpretations of emergent CT angiography (CTA) studies of the neck and circle of Willis and to assess any adverse clinical outcomes. MATERIALS AND METHODS: Five hundred thirty-eight CTA studies (287 circle of Willis and 251 neck) ordered emergently after hours and given preliminary readings by radiology residents from January 1, 2006, through December 31, 2007, were retrospectively reviewed. Discrepancies between the interpretations of radiology residents and the final reports of neuroradiology attending physicians were classified as either false-negatives (failure to recognize abnormalities) or false-positives (misinterpreting normal scans as abnormal). Discrepancies that could affect patient care or clinical care were considered major. RESULTS: Overall, the discrepancy rate was 13.6% for circle of Willis CTA and 13.5% for neck CTA. The misinterpretation rate of first-year residents was 19.5%, which was statistically significant compared with more senior-level residents (p = 0.05). There were 57 false-negative interpretations. The most common misses were stenosis greater than 50% (n = 16) and aneurysm (n = 15), and the most common false-positive was overcalling a potential intracranial aneurysm (n = 7). No adverse clinical outcomes were detected. CONCLUSION: The discrepancy rate between interpretations by on-call radiology residents and attending physicians of neuroradiology CTA studies was higher than expected at 13.6%, with a statistically significant greater miss rate among the most junior residents, which may be mitigated by recent changes with respect to the radiology residents' overnight call. No adverse clinical outcome was detected.

Linear longitudinal decline in fractional anisotropy in patients with amyotrophic lateral sclerosis: preliminary results.

BACKGROUND AND PURPOSE: As potential therapies aimed at halting or slowing the decline in upper motor neuron function in patients with amyotrophic lateral sclerosis (ALS) or primary lateral sclerosis (PLS) are developed, a quantitative method for monitoring response will be necessary. Measurement of fractional anisotropy (FA) using diffusion tensor imaging (DTI) over time should parallel functional decline from upper motor neuron degeneration in these patients. PATIENTS AND METHODS: Two patients with definite ALS were imaged at 3.0 T and FA values were obtained in the corticospinal tract every 3 months for 1 year. The FA values were compared to normal age-matched controls. RESULTS: Both patients showed linear decreases in FA values over time with R(2) values ranging from 0.93 to 0.99. The decline became statistically significant over the course of the study. Qualitative decreases in anisotropy were also evident on FA maps. CONCLUSION: If these trends can be validated in greater numbers of patients, DTI may serve as an objective quantitative biomarker for disease progression in patients with upper motor neuron disease.

Diffusion tensor imaging and tractography of Rasmussen encephalitis.

A 5-year-old girl presented with intractable seizures and nonfocal hemispheric slowing on EEG. Blood, urine, and CSF laboratory values were all normal. MR imaging of the brain demonstrated diffuse volume loss of the entire left hemisphere. Clinical and imaging findings were consistent with the diagnosis of Rasmussen encephalitis. Diffusion tensor imaging demonstrated increased ADC values and decreased fractional anisotropy (FA) of the affected (left) hemisphere. Tractography data showed decreased numbers of lines drawn in the affected hemisphere, with fewer lines drawn at higher FA thresholds, relative to the contralateral hemisphere, or to normal age-matched controls. Diffusion tensor imaging offers an adjunct MR imaging modality in diagnosis and monitoring of this rare condition.

Discrepancy rates of radiology resident interpretations of on-call neuroradiology MR imaging studies.

PURPOSE: To determine the discrepancy rates of radiology residents interpreting emergent neuroradiology magnetic resonance (MR) imaging studies and to assess any adverse clinical outcomes. MATERIALS AND METHODS: Three hundred sixty-one brain and spine MR imaging and MR angiographic examinations that were ordered emergently after hours and given preliminary interpretations by radiology residents were retrospectively reviewed from December 1, 2006 to May 31, 2007 with institutional review board approval. Discrepancies between the interpretations of radiology residents and the final reports of attending neuroradiologists were classified as either false-negative (FN, failure to recognize abnormalities) or false-positive (FP, misinterpreting normal images as abnormal). Discrepancies that could affect patient care or clinical outcome were considered major. RESULTS: Overall, the agreement rate was 92.8%, the overall discrepancy rate was 7.2%, the major disagreement rate was 4.2%, and the minor disagreement rate was 2.2%. Misinterpretations among 1st-year residents on call were significant (P < .04) when compared with more senior-level residents. There were 23 FN interpretations. The most common misses were acute stroke (n = 3), aneurysm (n = 3), vascular occlusion (n = 3), and disk herniation (n = 2). There were only three FP interpretations (misdiagnoses of syrinx, arachnoiditis, and acute infarct). CONCLUSION: There was no adverse clinical outcome as a result of misinterpretations, owing in part to rapid turnaround time for final reporting. Level of residency training has a significant effect on the rate of discrepancy, which may be mitigated by recent changes regarding 1st-year radiology residents' overnight call.