3D contrast‐enhanced MR angiography of the run‐off vessels: Value of image subtraction

Abstract

The diagnostic gain associated with image subtractions was assessed regarding contrast-enhanced 3D magnetic resonance angiography (MRA) image sets of the pelvic and lower extremity arteries. The MRA strategy combined a dedicated vascular coil with a single injection, two-station protocol. Voxel-by-voxel signal intensity subtraction was performed on MRA image sets obtained before and during dynamic infusion of a para-magnetic contrast agent. Nonsubtracted and subtracted MRA image sets were assessed for the presence of occlusive (four grades) disease, using DSA as the standard of reference. In addition, SNR and CNR were recorded for each vascular segment on both the non-subtracted and subtracted images. Index terms: magnetic resonance angiography; peripheral vascular disease; image subtraction; contrast media; magnetic resonance imagery CONTRAST-ENHANCED 3D MRA combines fast 3D gradient echo imaging with the intravenous administration of a para-magnetic contrast agent. Collected during the intra-arterial phase of the intravenously administered para-magnetic contrast agent (1-3), the images provided by this technique display arteries containing the T1-shortening contrast agent, thereby eliminating saturation-and turbulence-induced artifacts which limit time-of-flight and phase-contrast MRA (4 -6). Contrast-enhanced 3D MRA has thus emerged throughout the world as the modality of choice for assessing the thoracic and abdominal aorta (1,(7)(8)(9)(10)(11)(12), and the renal, pelvic and carotid arteries (13-17).Contrast-dose limitations initially curtailed the technique to the display of the vascular territory contained within a single 40 cm-48 cm field of view. The development of "bolus chase" techniques has extended coverage to the entire run-off vasculature, encompassing the pelvic, femoral, popliteal and trifurcation arteries. Based on intermittent rapid table motion during a slow intravenous injection of a para-magnetic contrast agent, the technique allows for the acquisition of several slightly overlapping 3D data sets (18,19).To compensate for enhancement of surrounding tissues due to capillary leakage associated with the slow infusion of the extra-cellular agents, some investigators recommend the use of a subtraction technique (18 -22). Image subtraction, however, prolongs and complicates the MRA exam; the time for data acquisition and image reconstruction is doubled, due to collection and reconstruction of baseline images at identical locations prior to administration of the contrast agent. Furthermore, the actual subtraction process is time-consuming. To avoid partial volume effects related to the phase differences between the flowing and stationary magnetization within a voxel, complex subtractions have been proposed (23). In contrast to the more commonly employed magnitude subtractions, complex subtractions can be performed either by subtracting the raw or Fourier-transformed data, followed by magnitude image calculation or subtraction of phase-corrected, real-part images.The purpose of this study was to det...

Gadobutrol-enhanced moving-table magnetic resonance angiography in patients with peripheral vascular disease: a prospective, multi-centre blinded comparison with digital subtraction angiography

“…Furthermore, phase-array coils, which boost SNR by a factor of 4-5 over the body coil and which improve accuracy of stenosis depiction in calf vessels [26], were available for only 22 patients in this study and most centres used the body coil, with resultant diminished SNR for signal reception. Although the advantage of mask subtraction is still disputed [22,27,28,29], this was impossible owing to manufacturer-specific limitations at some centres.…”

Fusion and subtraction post-processing in body MRI

“…A subtraction algorithm performs this task to create images that can be manually adjusted in all the standard ways to suit the user [9]. Dynamic subtraction imaging has been thoroughly described in the literature [10][11][12] and is a well-established technique, particularly in MR angiography [13] and MR urography [14]. The use of subtraction as a postprocessing tool for quantitative analysis is beyond the scope of this article.…”

MR Angiography and Development: Review of Clinical Applications

“…An alternative approach to increasing SNR and CNR with standard doses of gadolinium without further www.intechopen.com limiting spatial resolution would be to use contrast agents with preferential vascular contrasting properties. Gadobenate dimeglumine (Gd-BOPTA, MultiHance™; Bracco Imaging SpA, Milan, Italy) is a gadolinium based contrast agent that possesses increased T1 relaxivity in vivo compared to other available gadolinium agents (9.7 mM -1 second -1 compared to between 4.3 and 5.0 mM -1 second -1 ) due to a capacity for weak and transient interaction with serum albumin [59][60][61]. Preliminary investigations in healthy volunteers revealed that the vascular signal intensity of the abdominal aorta is higher and longerlasting following administration of Gd-BOPTA than following administration of Gd-DTPA at the same dose and injection rate.…”