Comparison of matched‐filtered two‐dimensional projection and elliptical centric‐ordered three‐dimensional contrast‐enhanced magnetic resonance angiography

Abstract

Purpose:To compare the image quality of matched-filtered two-dimensional projection magnetic resonance angiography (MRA) and elliptical centric-ordered (EC) three-dimensional MRA. Materials and Methods:Signal-to-noise ratios (SNRs) of matched-filtered two-dimensional projection and EC threedimensional MRA are developed theoretically and compared by clinical studies, in which 10 -20 mL of gadolinium (Gd) was injected at 1.5 mL/second. The artery-vein contrast in twodimensional projection MRA was managed by manually selecting specific templates for the matched filters. Results:The SNR of matched-filtered two-dimensional projection MRA is superior to that of EC three-dimensional MRA for vessels wider than one pixel due to the integral effect. The artery-vein contrast can be managed flexibly in two-dimensional projection MRA by choosing different templates for the matched filter, while the artery-vein contrast in EC three-dimensional MRA is solely determined by the timing to start the acquisition. Conclusion:Matched-filtered two-dimensional projection MRA provides comparable image quality and is a flexible alternative to EC three-dimensional MRA in applications where contrast timing is difficult and temporal information is of interest. ELLIPTICAL CENTRIC-ORDERED (EC) three-dimensional contrast-enhanced magnetic resonance angiography (MRA) has become established as a minimally invasive vascular imaging modality in clinical practice (1). It provides a three-dimensional visualization of the arterial vasculature with good venous suppression and high signal-to-noise ratio (SNR) due to the centric k-space ordering and an extended acquisition time. An accurate timing of the acquisition relative to the peak contrast enhancement is crucial for optimal SNR and artery-vein contrast (2). The timing is usually measured either by a test bolus (3) or by a real-time triggering tool (4). In any case, there could be errors due to the complex blood flow patterns among the patient populations (5), which may cause venous contamination and/or loss of SNR. The other concern of EC three-dimensional MRA is that the signal intensities of small vessels and vessel edges are lower than those of large vessels (6). This is due to their relatively higher signal contribution from the high frequencies in k-space, which are scanned at reduced contrast concentration following first pass.Alternatively, two-dimensional projection MRA has been applied in the situations where timing is difficult, such as for imaging the runoff arteries of ankles and feet (7). Two-dimensional projection images are acquired repeatedly at a high temporal resolution. The arterial conspicuity and SNR can be improved by subtraction and matched filtering (8). However, the work on two-dimensional projection MRA has focused primarily on acquiring the high temporal information (9). The image quality is usually thought to be inferior to that of EC three-dimensional MRA even after postprocessing.In this study, we compare the image quality of EC three-dimensional MRA and two-dimension...

Three‐dimensional reconstruction of limited‐view projections for contrast‐enhanced magnetic resonance angiography at high temporal and spatial resolution

“…Recessed EC sequences (4) were developed to minimize artifacts associated with timing errors and successfully improved the robustness of contrast-enhanced MRA in clinical applications. However, in some particular situations, such as among patients with arteriovenous fistula or arteriovenous malformations, the blood flow pattern may be significantly altered by irregular pathways and the time for artery-vein contrast passage may be shortened to only a few seconds (5). In such circumstances, venous contamination cannot be avoided even with an accurate timing of the contrast arrival.…”

“…However, due to the lack of depth information in the third dimension and the lower SNR and image contrast of the time-resolved projection images compared to that of 3D MRA, its applications are limited in clinical practice. It has been suggested that SNR and image contrast can be improved to be comparable to 3D MRA by appropriate matched filtering (5,11). The depth information can be perceived by acquiring and viewing projections from multiple angles.…”