CONTRAST-ENHANCED MR-ANGIOGRAPHY FOR THE DIAGNOSIS OF INTRACRANIAL VASCULAR-DISEASE - OPTIMAL DOSE OF GADOPENTETATE DIMEGLUMINE

OBJECTIVE. Although contrast-enhanced MR angiography has been shown us eful in evaluating intracranial vascular lesions, particularly those w ith slow flow, the optimal dose of contrast material has not been foun d. Accordingly, we performed a study to determine the optimal dose of gadopentetate dimeglumine for contrast-enhanced MR angiography of intr acranial vascular diseases. SUBJECTS AND METHODS, In this prospective study, 152 consecutive adult patients suspected of having intracranial vascular diseases had cerebral MR angiograms. Images were obtained wi th a three-dimensional time-of-flight sequence with magnetization tran sfer saturation on a 1.5-T unit. Imaging parameters (43/8 [TR/TE], 20 degrees flip angle, 64 1-mm-thick sections) were identical in each MR angiogram. One hundred twenty-two of 152 patients were randomly assign ed to receive one of four doses (0, 5, 10, or 20 ml) of gadopentetate dimeglumine for MR angiography (36, 37, 38, and 11 patients, respectiv ely). In patients who had normal major cerebral arteries on MR angiogr ams, degree and extent of visualization of the cerebral veins and smal l intracranial arteries were rated blindly on a three-point scale, and the results were compared among the four groups given different doses of contrast material. In another 30 patients who had unenhanced and e nhanced MR angiograms, the presence or absence of artifactual narrowin g of the internal carotid artery or major cerebral arteries (caused by signal loss due to slow or turbulent flow seen only on unenhanced ima ges) and the visibility of arteriovenous malformation were determined. RESULTS. In nearly all patients, regardless of the dose of contrast m aterial, the cerebral veins were well visualized on MR images. Degree and extent of visualization of the cerebral veins appeared to depend o n the dose of contrast material. In the 20-ml injection group, venous overlap limited interpretation of the small and large arteries, wherea s in the 5- and 10-ml groups, the signal intensity of the veins was mu ch less intense, causing no difficulty in interpretation. However, no significant differences in visibility of the small arteries were appar ent between the unenhanced and enhanced MR angiograms, even though the small vessels were better visualized in some patients who received ei ther 5 or 10 ml of contrast material. In six of the 30 patients who ha d both unenhanced and enhanced MR angiograms, the unenhanced images sh owed artifactual narrowing of the internal carotid or middle cerebral arteries, which proved to be normal on contrast-enhanced MR angiograms . Venous sinuses or draining veins were better delineated on contrast- enhanced MR angiograms in all six patients with arteriovenous malforma tion. CONCLUSION. Five to 10 milliliters of gadopentetate dimeglumine appears to be an optimal dose range for contrast-enhanced cerebral MR angiography. Use of this dose can help in differentiating true stenosi s of large arteries from artifactual narrowing and in depicting small arteriovenous malformation with slow flow.