Evaluating contrast kinetics by acquiring 2D images during 3D contrast‐enhanced MR angiography

Abstract

Purpose: To monitor contrast kinetics by acquiring multiple 2D images during 3D contrast-enhanced magnetic resonance angiography (CE MRA). Materials and Methods:A 2D real-time autotriggering tool was integrated into a 3D sequence, enabling it to run multiple times during 3D acquisition. Several dummy scans were applied after each transition to maintain the steady state condition of both sequences. The number of the acquired 2D images and their distribution can be adjusted. Each 2D image was saved along with its associated timing. Contrast signal variations over time were plotted, reflecting selective signal measurement over an artery and vein from the saved 2D images.Results: Different contrast kinetics timings were calculated from the resulting plot. Contrast arrival time to the internal cerebral artery was 13.2 Ϯ 1.2 seconds and the peak arterial to peak venous (at the confluence of sinuses) enhancement was 6.7 Ϯ 0.6 seconds. The observed timing could be used for 3D sequence optimization; the saved 2D images are useful in detecting and characterizing vascular abnormalities. Conclusion:Integrating 2D and 3D sequences into one sequence to monitor contrast kinetics through the neurovasculature is feasible without the need for extra injections or reduced spatial resolution. The technique can also be used in different parts of the body to extract useful clinical information. THREE-DIMENSIONAL (3D) contrast-enhanced (CE) magnetic resonance angiography (MRA) is a valuable tool for the evaluation of various intracranial vascular diseases (1,2), where it could provide high resolution images that improve the depiction of vessel anatomy. The final 3D data set provides clear and comprehensive images for both arteries and veins under investigation, but no information about the contrast agent dynamics is observed. Contrast kinetics are important for understanding the nature of intracranial arteriovenous (AV) malformations (AVM) (3) or the formation of AV fistula, where early filling of some veins takes place. These indications have a substantial diagnostic value to direct the clinical management.Several techniques have been published that extract in vivo contrast kinetics. Time-resolved imaging (4) regularly acquires portions of k-space, allowing multiple 3D images to be generated at short intervals. Another technique for temporal monitoring of contrast concentration is also available with fast MR projection imaging (5), which provides temporal and spatial enhancement information. However, both techniques have pitfalls, particularly for imaging the head, where high spatial resolution is needed to visualize small blood vessels.A previous study (6) embedded multiple 2D projection images during 3D data acquisition to monitor contrast behavior. In this case, the 2D scan parameters were identical to the 3D scan parameters, to preserve the steady state condition of the MR signal while switching between both scans. This selection presents some limitations. First, slice thickness of the 2D image is relatively large (around 70 mm) a...

High‐resolution imaging of the intracranial arterial and venous systems following a single contrast injection

“…To verify this outcome, another study was implemented, in which multiple 2D images were collected during contrast injection (11). Signal intensity of the arterial and venous enhancement was measured from the 2D images.…”