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Objectives-The accuracy of magnetic resonance angiography (MRA) was determined in patients with recently symptomatic tight (80%-99%) carotid stenosis (on Doppler ultrasound), and the eVect of stenosis severity on the accuracy and interobserver variability of MRA was studied. Methods-Forty four consecutive patients undergoing intra-arterial angiography (IAA) before carotid endarterectomy were prospectively studied, in two centres with identical MR scanners and sequences. All patients had undergone Doppler ultrasound, showing a 70% or worse carotid stenosis on the symptomatic side. MRA and IAA were done during the same admission. The MRA films were each independently and blindly read for percentage stenosis (signal gap if present) by four observers. The IA angiograms were read separately by one observer, blind to symptoms, and Doppler and MRA results. Results-Signal gaps on MRA were seen in stenoses ranging from 67% to 99% on intraarterial angiography. Magnetic resonance angiograms consistently overestimated the percentage stenosis according to intraarterial angiography. Clinically significant misclassification of stenosis occurred according to MRA in 7% of patients, and was more frequent as carotid stenosis increased. Conclusion-Significant diagnostic errors occur with MRA in patients with tight carotid stenosis. Any morbidity occurring as a result of misclassification by MRA is likely to be oVset by the avoidance of complications; however, this could only be determined with certainty in a randomised controlled trial. (J Neurol Neurosurg Psychiatry 2001;71:155-160)

In a prospective study, spiral-acquisition computed tomography (SACT) of the thorax was evaluated in 104 patients with extrathoracic malignancy and suspected pulmonary metastases, and was directly compared with conventional computed tomography (CCT) in 23 patients. The following parameters were assessed: lesion detectability; the effect on lesion detectability of reconstruction of scans at 5 mm and 10 mm slice increments; breathing artefact and slice misregistration. The radiation dose of the two techniques was measured using thermoluminescent dosimeters placed within an anthropomorphic chest phantom, and the visibility of simulated metastases inserted into the phantom was also compared using CCT, standard SACT and SACT with pitch greater than 1.0. Where metastases were present, SACT scans showed significantly better lesion detectability than CCT scans (p < 0.001). Image reconstruction of SACT data at 5 mm increments conferred no significant advantage in lesion detectability over 10 mm increment reconstructions. Compared with CCT, SACT scans showed reduced breathing artefact, and a complete absence of slice misregistration (p < 0.01). Phantom measurements of radiation dose and resolution were similar for both techniques. Increasing the pitch of the spiral in SACT caused only a small decrease in phantom resolution, but with the advantage of a reduction in the radiation dose. Spiral-acquisition CT is superior to conventional CT for the assessment of pulmonary metastatic disease.

We describe four patients, ranging from 26-40 years of age, who presented with seizures and large, poorly circumscribed cerebral tumours on magnetic resonance imaging. The resected tumours demonstrated a histopathology similar to low-grade glioma, but with admixed mature neurones. Immunohistochemistry demonstrated expression of putative neuronal antigens in the neuronal component as well as in tumour cells which did not show neuronal morphology. These tumours did not have the usual radiological and pathological features typical of gangliogliomas, but demonstrated an infiltrative pattern of growth and subsequent progressive behaviour. The term ganglioglioma, with its implication of good prognosis, is therefore inappropriate for tumours of this type. The expression of "neuronal" antigens by astrocytomas requires further investigation.