Role of slice thickness in MR imaging of the internal auditory canal.

The relative efficacy of post-Gd-DTPA 5 and 3 mm axial T1-weighted images was compared in the detection of lesions in the internal auditory canal and cerebellopontine angle. One hundred twenty consecutive patients were prospectively evaluated with 5 mm axial T1-weighted slices. If these were negative or questionable. 3 mm axial slices were immediately obtained as the next sequence. Eighteen percent of cases were positive and in none of these was the 5 mm study normal. However, in 22 negative cases and two positive cases, a 3 mm study was necessary for confirmation. Five millimeter axial scanning post Gd-DTPA is recommended as the initial study for detection of masses in the internal auditory canal and cerebellopontine angle. Because this study requires fewer acquisitions than 3 mm sections and can be done satisfactorily on low and midfield systems, there are potential time- and cost-saving benefits to this approach

Comparison of radiographic quality and adverse reactions in myelography with iopamidol and metrizamide.

A randomized double-blind study was conducted to compare the radiographic quality and adverse reactions in myelography of the two nonionic water-soluble contrast media, iopamidol and metrizamide. A total of 46 myelograms were obtained, 28 with iopamidol and 18 with metrizamide. Untoward reactions consisted of nausea, headaches, back and leg pain, neuropsychiatric findings, and urinary retention. Iopamidol caused no reactions in 20 of the 28 cases, while metrizamide caused no reactions in only three of 18 cases. Film quality evaluation showed 22 of the 28 studies with iopamidol were judged excellent, whereas only 11 of the 18 metrizamide studies were judged excellent. The results of this study suggest that iopamidol produces better quality studies with fewer and milder adverse reactions than metrizamide

Glial neoplasms: dynamic contrast-enhanced T2*-weighted MR imaging

PURPOSE: To evaluate the role of T2*-weighted echo-planar perfusion imaging by using a first-pass gadopentetate dimeglumine technique to determine the association of magnetic resonance (MR) imaging-derived cerebral blood volume (CBV) maps with histopathologic grading of astrocytomas and to improve the accuracy of targeting of stereotactic biopsy. MATERIALS AND METHODS: MR imaging was performed in 29 patients by using a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence followed by conventional imaging. The perfusion data were processed to obtain a color map of relative regional CBV. This information formed the basis for targeting the stereotactic biopsy. Relative CBV values were computed with a nondiffusible tracer model. The relative CBV of lesions was expressed as a percentage of the relative CBV of normal white matter. The maximum relative CBV of each lesion was correlated with the histopathologic grading of astrocytomas obtained from samples from stereotactic biopsy or volumetric resection. RESULTS: The maximum relative CBV in high-grade astrocytomas (n = 26) varied from 1.73 to 13.7, with a mean of 5.07 +/- 2.79 (+/- SD), and in the low-grade cohort (n = 3) varied from 0.92 to 2.19, with a mean of 1.44 +/- 0.68. This difference in relative CBV was statistically significant (P <.001; Student t test). CONCLUSION: Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy