Arterial-phase three-dimensional contrast-enhanced MR angiography of the carotid arteries.

OBJECTIVE: The purpose of this study was to evaluate IV injection of a single dose of gadopentetate dimeglumine for three-dimensional (3D) arterial phase MR angiography of the carotid arteries. SUBJECTS AND METHODS: Nine adult patients were serially imaged after IV injection of a single-dose bolus of gadopentetate dimeglumine at 1.5 T with a coronal single-slice spoiled two-dimensional (2D) gradient-echo acquisition encompassing the common carotid arteries and internal jugular veins. Region-of-interest measurements for the nine patients generated a composite arteriovenous signal versus time profile. The time interval of maximum arteriovenous signal difference was subsequently matched to the center of K-space in a 3D spoiled gradient-echo coronal MR angiography sequence (field of view, 24 or 26 cm; matrix size, 256 x 128; slice thickness, 3 mm; number of slices, 12; one excitation; bandwidth, 16 kHz; and scan time, 29 sec). This protocol allowed us to selectively enhance the arterial phase for carotid angiography. The protocol was then tested in 20 adult patients, after which we graded the degree of coincidental venous enhancement and the presence of artifacts.
RESULTS: On the 2D dynamic images, we identified a 10-sec window of selective arterial enhancement that began 20 sec after the start of the injection of the bolus of gadopentetate dimeglumine. With 3D MR angiography, we saw selective enhancement during the arterial phase of carotid MR angiography in nine of 20 patients. In seven of the remaining 11 patients, we saw the signal intensity of the arterial phase exceed a threshold greater than two standard deviations from venous signal. In the final four patients, we saw arterial signal equal to venous signal. We saw no ghosting artifact (from intravascular signal changing too rapidly during phase encoding) in any patient.
CONCLUSION: By precisely timing the infusion of a single dose of gadopentetate dimeglumine, we were able to selectively enhance the arterial phase on 3D MR angiograms of the carotid arteries.