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W2073324106 abstract "HomeCirculationVol. 100, No. 22Magnetic Resonance Angiography Free AccessOtherPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessOtherPDF/EPUBMagnetic Resonance Angiography Update on Applications for Extracranial Arteries E. Kent Yucel, Charles M. Anderson, Robert R. Edelman, Thomas M. Grist, Richard A. Baum, Warren J. Manning, Antonio Culebras and William Pearce E. Kent YucelE. Kent Yucel Search for more papers by this author , Charles M. AndersonCharles M. Anderson Search for more papers by this author , Robert R. EdelmanRobert R. Edelman Search for more papers by this author , Thomas M. GristThomas M. Grist Search for more papers by this author , Richard A. BaumRichard A. Baum Search for more papers by this author , Warren J. ManningWarren J. Manning Search for more papers by this author , Antonio CulebrasAntonio Culebras Search for more papers by this author and William PearceWilliam Pearce Search for more papers by this author Originally published30 Nov 1999https://doi.org/10.1161/01.CIR.100.22.2284Circulation. 1999;100:2284–2301Magnetic resonance angiography (MRA) has excited the interest of many physicians working in cardiovascular disease because of its ability to noninvasively visualize vascular disease. Its potential to replace conventional x-ray angiography (CA) that uses iodinated contrast has been recognized for many years, and this interest has been stimulated by the current emphasis on cost containment, outpatient evaluation, and minimally invasive diagnosis and therapy. In addition, recent advances in magnetic resonance (MR) technology resulting from fast gradients and use of contrast agents have allowed MRA to make substantial advances in many arterial beds of clinical interest. The goal of this scientific statement is to present the current state of MRA of the extracranial arteries and to suggest current as well as possible future clinical applications for MRA. For the purposes of this statement, MRA is defined as MR techniques that provide cross-sectional or projectional images of normal and diseased arterial anatomy. It does not deal with the equally important area of quantitative flow measurement with MR. The first section deals with the technical basis of MRA. Subsequent sections deal with individual vascular beds in which MRA has shown clinical promise.MRA: Technical ConsiderationsThe “gold standard” for many manifestations of vascular disease, especially arterial occlusive disease, is CA, an invasive, costly, and potentially hazardous procedure. MRA could represent an alternative, noninvasive approach. Rather than a single technique, MRA actually represents a family of different techniques. As outlined below, contrast between blood and soft tissues is derived from completely different MR mechanisms in the various MR techniques. We will consider the basic principles underlying the MR imaging (MRI) appearance of flowing blood and the techniques used to image blood flow and render angiogram-like MRI scans.Depending on the imaging technique used, blood may appear bright or dark. On traditional spin-echo MR images, blood vessels usually appear dark. With spin-echo pulse sequences, a pair (90o and 180o) of section-selective radiofrequency (RF) pulses is used to produce an MR signal. If blood flows out of the plane of the section in the time interval between successive RF pulses, the result is an absence of signal, called a flow void.1 The flow void can be emphasized by use of a thin section or a long echo time. In a fast spin-echo sequence, a long train of echoes is acquired by use of a series of 180o RF pulses; as a result, washout effects are even more substantial than with conventional spin-echo techniques. Other methods for creating a flow void include presaturation, which involves application of an additional RF pulse outside the plane of the section to suppress the signal intensity of inflowing blood; dephasing gradients; and preinversion pulses to nullify the blood signal.2To create bright blood, gradient-echo pulse sequences are used. In a gradient-echo sequence, only a single RF pulse is applied during each sequence repetition, so no signal is lost because of washout effects. Data for images on which blood is bright can be acquired as a series of overlapping thin sections (sequential 2-dimensional [2D]) or as 1 or more thick (3-dimensional [3D]) volumes. Each sequence has advantages, as discussed below. Bright-blood techniques can be subcategorized into time-of-flight (TOF)3 and phase-contrast techniques.4 The basis of TOF techniques is that positive flow contrast is generated by inflow effects, whereas the background (stationary tissue) is saturated by the rapid repeated application of RF pulses. Saturation pulses based on flow geometry can be used to eliminate unwanted vessels (eg, leg veins for lower-extremity arteriography). Use of a segmented gradient-echo sequence with cardiac triggering is helpful to eliminate arterial pulsation artifacts.5 The basis for phase-contrast MRA is that the flow of blood along a magnetic field gradient causes a shift in the phase of the MR signal. With phase contrast, pairs of images are acquired that have different sensitivities to flow. These are then subtracted to cancel background signal, leaving only signal from flowing blood. Phase contrast also permits flow (velocity) quantification,6 because the phase shift is proportional to the velocity.The core of MRA is the ability to portray blood vessels in a projective format similar to CA. Currently, projection images are created by postprocessing of images acquired by a 2D or 3D gradient-echo sequence. Although image processing can be postponed until after the patient has left the MR suite, it is best done while the patient is still within the magnet so that additional scans can be obtained if needed. Most commonly, the images are processed by use of a maximum-intensity projection (MIP) algorithm.78 With an MIP algorithm, the brightest pixels along a user-defined direction are extracted to create a projection image. Areas with poor flow contrast, including the edges of blood vessels and small vessels with slow flow, may be obscured by overlap with brighter stationary tissue.9 Through reduction of the pixel size and suppression of the signal of stationary tissues, the quality of the MIP can be improved substantially. The reduction in pixel size is accomplished by use of a large (eg, 256×512) acquisition matrix along with a small field of view.A variety of artifacts caused by phase or magnitude variations in the MR signal afflict MRA. Within a single image volume element (voxel), blood protons flowing at different velocities accumulate a range or dispersion of phase shifts. Complex flow can produce signal loss due to intraview phase dispersion (ie, it occurs during each repetition of the pulse sequence), ghost artifacts from view-to-view signal variations (ie, those that occur over multiple sequence repetitions), and flow-displacement errors relating to the time delay between RF excitation and frequency encoding or between phase and frequency encoding. These effects tend to falsely exaggerate the severity of a stenosis and are most pronounced with 2D MRA. They can also limit flow-based MRA imaging in areas of slow flow, such as aneurysms. A short echo time (TE) minimizes flow-displacement and phase-dispersion artifacts; phase dispersion is further decreased when the voxel size is minimized (eg, by use of thin sections). Small voxels and short TEs are most easily obtained with 3D TOF methods. The biggest drawback of the thick volumes used with 3D is that slow or recirculating flow can become saturated. The advantages of both 2D and 3D techniques are gained with a series of thin-slab 3D acquisitions. The sequential 3D (or multiple overlapping thin-slab acquisition [MOTSA]) technique gives better flow enhancement than single-slab 3D techniques and less dephasing than 2D techniques.10 The method has some drawbacks as well. For instance, the nonrectangular profile of the 3D slabs necessitates the use of substantial overlap (up to 50%) of adjacent slabs, so that total scan time is increased compared with single-slab 3D. Moreover, signal-intensity variations within the individual slabs due to saturation effects cause an annoying “venetian blind” artifact. With sequential 2D or 3D acquisitions, slight patient motion can generate discontinuities in the vessel contour that can be mistaken for focal stenosis or fibromuscular dysplasia.Recently, an increasingly preferred method for chest and abdominal MRA is the combination of breath-hold 3D gradient-echo sequences with short repetition time (TR) and short TE during administration of a gadolinium chelate, often in a double dose.1112 The contrast agent shortens the T1, or longitudinal relaxation time, of blood (to as low as 50 ms, compared with normal blood T1 of ≈1200 ms), so that the blood appears bright irrespective of flow patterns or velocities. Correct timing of the injection is important to ensure synchronization between the transit of contrast material and scanning. Methods that can be used to achieve correct timing include empirical estimation of transit time, a small test bolus of contrast agent to determine the time delay between injection and arrival of the contrast agent bolus in the target vessel,13 automated detection of contrast bolus passage,14 and MR fluoroscopy to observe contrast passage.15Contrast-enhanced MRA (CEMRA) is advantageous in displaying detailed vessel anatomy and in reducing artifacts. MIP images can be reliably rendered in multiple projections. If the patient is incapable of holding his or her breath, then a slower acquisition can be done over several minutes with a longer/slower infusion of contrast agent. However, branch vessel detail may be degraded by respiratory motion. Subtraction of a precontrast from a postcontrast scan eliminates the signal from background tissue (assuming no patient motion). Additionally, it is possible to perform time-resolved 3D MRA studies to better differentiate arteries and veins.16 Recently, testing has begun in humans of intravascular MR contrast agents that are retained within blood vessels and that selectively enhance the blood pool on T1-weighted MR images.1718192021 AMI-227 (Advanced Magnetics), an ultrasmall iron particle, has been shown to enhance vessels within the abdomen and chest in the steady state.1718 Another iron particle, NC100150 (Nycomed-Amersham), has recently entered human trials.19 MS-325 (EPIX Medical, Inc and Mallinckrodt Inc), a gadolinium-chelate that binds noncovalently to plasma albumin, has been shown to enhance the lower extremity and carotid vessels in the steady state as well as to enhance the arteries of the lower extremity during the first pass in a manner comparable to the currently available extracellular gadolinium chelates.22 The potential clinical applications of these agents await the results of large-scale multicenter clinical trials.Coronary MRA is perhaps the most technically challenging area of MRA. To apply MRA techniques to the coronary arteries, additional technical obstacles had to be overcome, including compensation for respiratory and cardiac motion. Standard electrocardiographically (ECG) gated spin-echo and gradient-echo cine images only occasionally show portions of the coronary arteries, and these images are not adequate for detailed evaluation.23 Even a 1-second acquisition is too long to freeze cardiac motion. Instead, the acquisition can be “segmented” into blocks of phase-encoding steps, which are then interleaved to create an image.24 Segmentation within a single breath-hold of 10 to 20 seconds can reduce the time for data acquisition within each cardiac cycle to 100 ms or less, which is adequate to minimize cardiac motion artifacts, particularly in mid diastole or end systole. This strategy is known as segmented gradient-echo. Because the proximal coronary arteries are embedded in epicardial fat, chemical shift-selective fat saturation pulses are applied to reduce the fat signal. With this combination of techniques, the proximal portions of the left main, left anterior descending (LAD), and right coronary arteries (RCA) are routinely seen.Recently, navigator echo methods have been applied to eliminate the need for breath-holding. Navigator echo is a motion-compensation technique that relies on tracking of an MR-detectable interface by the MR scanner. In the case of coronary MRA, the diaphragm-lung interface is typically used. With navigator gating for coronary MRA, MRI data are only accepted for image reconstruction when the navigatorecho indicates that the diaphragm or lung is within a certain operator-defined range (usually 3 to 5 mm). In this respect, navigator echoes perform a function similar to the bellows used for respiratory gating but provide more consistent results. Because many data are rejected, acquisition times are typically increased by a factor of 2 or more, depending on the patient’s breathing patterns. However, if a fast imaging sequence such as segmented gradient echo is used, scan times are still reasonable, on the order of a few minutes at most. Image sharpness is as good as with breath-holding.25 Because navigator echoes permit signal averaging, the signal-to-noise ratio is increased, and higher in-plane spatial resolution can be obtained (eg, 0.5 mm). Moreover, navigator echoes ensure a consistent cardiac position from image to image, thereby minimizing misregistration artifact if one wishes to process a projection image.The navigator gating technique discards data that are acquired when the diaphragm is incorrectly positioned and thus increases scan time. Adaptive correction of image location by use of real-time navigator measurement of diaphragm position is a potential method for further reducing slice registration errors.2627 This method dynamically repositions the slice to follow the movement of the diaphragm and thus keeps the slice in a constant relation to the tissue of interest despite its motion. This technique, called navigator correction, can be combined with navigator gating to improve the efficiency of data acquisition. Navigator methods appear promising for both 2D and 3D acquisitions. Nevertheless, achievement of adequate spatial resolution, especially of small vessels, remains a challenge for MRA. Resolution below 0.5 mm may be required to achieve comparability with CA, especially in smaller (<3 mm) vessels. Motion makes this goal even more difficult to achieve, both by lengthening the scan time to compensate for respiratory motion (through navigators) and by narrowing the scanning window to a portion of the cardiac cycle. In the heart, beat-to-beat variations in cardiac position may exceed 1 mm, making submillimeter resolution even more challenging.MRA of the Carotid ArteryMRA of the carotid bifurcation may be accomplished by several different MRI techniques, including 2D TOF,28 3D TOF,29 and CEMRA.30 When the merits of these sequences are compared, several generalizations can be made. 2D TOF provides a strong vascular signal, even when the arterial velocity is low. 2D TOF should be used to differentiate near and complete internal carotid artery (ICA) occlusion. 3D TOF provides superior, submillimeter resolution but at the expense of sensitivity to flow. The weak vascular signal of 3D TOF in slow-flow situations may be improved by the use of MOTSA.31 The original slices from a 3D TOF acquisition may allow one to see some features of plaque directly. CEMRA is quick and robust and is not impaired by slow-flow situations. CEMRA is a good choice for those patients who cannot maintain a position for prolonged periods. Unfortunately, it can only be effectively performed on MRI systems with enhanced gradient hardware.There is currently no agreement as to which of these techniques is best. In part, this results from the fact that MRI instruments of different age and from different vendors have slightly different imaging characteristics. However, most experts use the MOTSA sequence for their primary interpretation. CEMRA is a very promising technique, but its diagnostic role awaits further validation. The aortic arch is best imaged by CEMRA, which has proven effective for the study of stenoses, aneurysms, and dissections.3233 The carotid siphons and intracranial arteries are best imaged with MOTSA.As a result of time constraints, only the cervical carotid artery is studied usually. A full study of the brain, intracranial vessels, bifurcation, and aortic arch requires one to position the patient 3 times (in the head, neck, and body coils) and necessitates that the patient spend more than 1 hour in the magnet. Such a comprehensive examination should be reserved for those with suspected tandem pathology on the basis of a prior duplex ultrasound (DUS) or MRA examination.A typical study might begin with a low-resolution 2D TOF to locate the bifurcation. Sections should be acquired as high as the base of the skull so that patency of the ICA can be positively established in the carotid canal of the temporal bone. Lack of flow at this level implies an occlusion at the bifurcation, because the ICA lacks branches between these points. If a vertebral artery or other vessel is absent on the 2D images, the sequence should be repeated without presaturation bands to exclude reversal of flow. Then, a MOTSA acquisition can be acquired of the bifurcation or at any other level identified as stenotic on the 2D series. A MOTSA acquisition of the bifurcation takes ≈10 minutes, whereas 2D TOF of the entire length of the carotid artery takes ≈6 minutes. Technical factors that may affect MRA are excessive patient motion and the presence of ferromagnetic metal in the neck.When carotid MRA is interpreted, special care should be taken to avoid overestimation of the stenosis severity in an area of turbulent flow.34 This phenomenon is encountered within the decelerating jet distal to a critical lesion. The tendency to overestimate stenosis severity is greatly reduced if one interprets the study from source images or reformations rather than from calculated projections.353637 Overestimation is also reduced in 3D acquisitions, presumably because the more gradient structure and submillimeter voxels of 3D acquisition result in less phase dispersion, although many practitioners of 2D TOF have shown an excellent ability to properly grade severe lesions. Finally, the tendency to overestimate stenoses is reduced if one quantitatively measures the vessel diameters formally with a calibrated jeweler’s loupe rather than by “eyeball estimation.”Table 1 summarizes many of the recent prospective comparisons of MRA and CA for the evaluation of the carotid bifurcation.37383940414243444546474849 The median sensitivity for a high-grade lesion was 93%, whereas the median specificity was 88%. These studies assumed CA to be the gold standard. A problem with this assumption is that many CA errors are considered errors in MRA. Because the reproducibility of CA itself is no better than 94%,485051 one can conclude that the actual sensitivities and specificities may be better than those reported in these studies. In fact, preliminary data suggest that noninvasive imaging may be more sensitive than CA in some instances.40 A comparison of CA, MRA, and DUS, with surgical specimens rather than CA used as the gold standard,52 found that DUS and MRA each correlate better with the endarterectomy specimen than does CA. This discrepancy can be attributed to the fact that the smallest diameter is often not appreciated by CA when the stenosis is elliptical or complex in shape. When CA and DUS are compared, it is particularly important to remember that the stenotic lumen is usually not circular, because Doppler velocities are determined by cross-sectional area rather than by diameter.53 Potentially important information about the shape of the plaque, available by MRA but not by CA, was not considered in the validation studies. The role of CA as a modality for assessing carotid stenosis has been established by its use in the large, multicenter clinical trials that have established endarterectomy as a successful stroke-prevention intervention. Multicenter clinical trials like the North American Symptomatic Carotid Endarterectomy Trial (NASCET) have never been undertaken with MRA rather than CA used to quantify stenosis. Therefore, MRA and DUS are assumed to be effective only to the degree that they agree with CA diameter measurements.Kent et al45 examined the cost-effectiveness of various imaging strategies for a population of patients with symptomatic carotid artery disease. Use of DUS alone resulted in a quality-adjusted life expectancy (QALE) of 9.619 years. CA alone resulted in a QALE of 9.632 years, with an excessive incremental cost-effectiveness ratio of $99 200 per quality-adjusted life year (QALY). The combination of DUS and MRA, followed by CA in the event of disparate results, maximized clinical outcome to 9.639 years at an incremental cost-effectiveness ratio of just $22 400 and was considered the optimum strategy. Obuchowski et al54 assumed a 20% prevalence of stenosis requiring surgery in patients who presented with a neck bruit. Three imaging strategies were examined: DUS followed in selected cases by MRA, DUS followed in selected cases by CA, and MRA alone. The QALE of the 3 strategies was virtually identical, whereas the incremental cost per QALY was $2922, $7470, and $7700, respectively. DUS alone was not examined. These data again argue for the use of a combined noninvasive approach.55 When asymptomatic patients are being screened, the advantages of noninvasive imaging are even greater. Kuntz et al56 concluded that use of CA in this population actually resulted in a greater incidence of stroke (7.12% in 5 years) than did DUS alone (6.35%), MRA alone (6.17%), or a combination of DUS and MRA followed by CA if necessary (6.34%).Currently, it appears that the workup of suspected carotid artery stenosis should begin with DUS, performed by an experienced and preferably accredited laboratory. Although it has been suggested that the detection of >70% stenosis on DUS alone might be sufficient to recommend carotid endarterectomy, it may be appropriate to confirm this diagnosis with an additional imaging study to minimize the possibility of erroneous management. If so, a technically adequate MRA at an imaging facility with substantial experience in the performance and interpretation of carotid MRA can fulfill this role at the lowest cost and risk to the patient.5758 CA should be considered when the results of DUS and MRA are discrepant, in cases of possible hairline patency (angiographic string sign), or where lesions are so atypical that they can only be understood by use of the high-resolution, selective vascular contrast of a catheter study.59 Supplementary imaging is especially advisable when results of DUS are technically limited. Typical limitations that necessitate additional imaging include the presence of a shadowing plaque, a deep course of the ICA, discordant gray-scale and Doppler measurements, and evidence of tandem lesions in cases in which these would alter patient management. Tandem lesions are suggested by the presence of a dampened and delayed waveform60 or unusually low diastolic velocities. To detect disease outside the ultrasonic window, MRA should also be considered in patients with atypical symptoms of cerebral ischemia and a DUS showing no disease or only mild disease. In some situations, the evaluation might begin with MRA (for example, when the MRA is performed as part of a brain MRI in patients with neurological symptoms).MRA of the Thoracic and Abdominal AortaStandard T1-weighted MR techniques provide detailed anatomic information about the dimensions of the thoracic and abdominal aorta in multiple planes, can identify the presence of intraluminal thrombus within aneurysms or intimal flaps associated with aortic dissection, and can locate the main aortic branches, such as the iliac, main renal, and brachiocephalic arteries, in relation to aortic pathology. However, for projectional angiographic imaging and for detection of branch vessels and branch vessel disease, MRA is essential.Abdominal aortic aneurysms (AAAs) have been an important focus of studies with MRA because of the desirability of replacing CA for preoperative evaluation. AAAs are typically diagnosed by physical examination, ultrasound, or computed tomography (CT), but angiographic imaging is often desired before preoperative evaluation. The important information that angiography must provide includes the upper extent of the aneurysm (including the relationship of the aneurysm to the renal arteries), the number and patency of the renal arteries, the patency of the mesenteric arteries, the inferior extent of the aneurysm (including the distance from the aneurysm to the aortic bifurcation), and aneurysmal or atherosclerotic disease of the iliac arteries. CA has been the standard approach for such preoperative evaluation. However, several studies of MRA for preoperative evaluation of AAAs have been published. Initial studies used noncontrast TOF MRA, often in conjunction with T1-weighted MRI. Although classification of aneurysms as suprarenal or infrarenal was good, detection of accessory renal arteries, renal artery stenosis, and iliac vascular disease was not adequate to justify replacement of CA. Limitations included the poor resolution in the slice-selection direction obtainable with 2D techniques and poor signal associated with slow flow in the ectatic aorta.616263More recently, interest has focused on CEMRA for AAA evaluation.64656667 The use of contrast enhancement both enables higher-resolution 3D imaging and provides high blood signal without the need for fast flow. In an initial study of 27 patients,66 CEMRA in combination with spin-echo and precontrast 3D TOF detected 7 of 9 accessory renal arteries, 8 of 9 renal artery stenoses, 4 of 4 celiac stenoses, and all iliac aneurysmal and stenotic disease. Interestingly, MRA correlated with surgical findings as well as CA for defining the proximal extent of the aneurysm. In a subsequent publication by the same group,67 MRA accurately defined the proximal extent of aneurysm in 87% of 38 patients. Sensitivities for iliofemoral occlusive and aneurysmal disease were 83% and 79%, respectively. Sensitivities for renal artery stenosis and accessory renal arteries were each 71%. In terms of surgical planning, MRA correctly predicted the cross-clamp site in 87%, the proximal anastomotic site in 95%, the need for renal revascularization in 91%, and the use of a bifurcated aortic prosthesis in 75%.In a study of 43 subjects64 that used CEMRA in combination with noncontrast techniques, MRA correctly defined the maximum aneurysm diameter, as well as its proximal and distal extent, in all patients. For detection of aortic branch artery stenosis involving the celiac, superior mesenteric, renal, or iliac arteries, sensitivity was 94%, with specificity of 98%. Potential limitations of the CEMRA technique included the inability to define the severity of branch vessel stenosis and inadequate visualization of the inferior mesenteric artery. The latter can often be adequately evaluated at the time of surgery. The results suggest that performance of CEMRA is adequate to allow the treatment decision to be made between aortic tube graft and aorto-bifemoral graft. With the imminent introduction of aortic stent-graft devices, additional clinical study will be needed to determine whether MRA can substitute for CA in the decision making process with regard to their use. Current resolution appears adequate to screen the renal arteries for disease. However, additional study is indicated before MRA can be relied on for evaluation of the mesenteric circulation. Recent improvements in scanner speed that allow contrast-enhanced aortography to be performed in <30 seconds, or within a breath-hold interval,13686970 and new blood-pool contrast agents currently under investigation21 may allow additional improvements in this area.For the thoracic aorta, evaluation of aortic dissection in addition to aneurysmal disease has been another important focus of thoracic MRA. Conventional spin-echo and gradient-echo cine MRI have been shown to be quite effective modalities for evaluation of thoracic aortic disease.7172737475 Hartnell et al,76 using noncontrast MRA, suggested that MRA allowed better demonstration of branch vessel stenoses, intimal flaps, and communications into false aneurysms than standard MRI of the aorta. CEMRA was used for evaluation in a range of disease of the thoracic aorta in another study77 ; in 30 patients with angiographic or surgical correlation, MRA successfully demonstrated dissection in 8 (including the correct type), coarctation in 3, and aneurysm in 10, as well as identifying 1 aberrant subclavian artery. Sensitivity for branch vessel stenosis in that study was 90%. MRA must be combined with conventional MRI to detect intramural hematoma or extravascular fluid collections.72Renal MRARecent developments in renal MRA have led to a significant improvement in technical success rate and diagnostic accuracy. Specifically, 3D CEMRA methods have been shown to provide a more reliable depiction of renal artery morphology than noncontrast MRA techniques. In addition, preliminary work with adjunctive MRA techniques suggests that it is possible to determine the hemodynamic significance of renal artery disease by use of MRA and MRI. MRA methods will therefore likely play an important clinical role in the evaluation of patients with renova" @default.
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W2073324106 date "1999-11-30" @default.
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W2073324106 title "Magnetic Resonance Angiography" @default.
W2073324106 cites W113174209 @default.
W2073324106 cites W1805173252 @default.
W2073324106 cites W1966204305 @default.
W2073324106 cites W1968324647 @default.
W2073324106 cites W1968706760 @default.
W2073324106 cites W1969148378 @default.
W2073324106 cites W1969726042 @default.
W2073324106 cites W1972862844 @default.
W2073324106 cites W1973346882 @default.
W2073324106 cites W1974945302 @default.
W2073324106 cites W1975833367 @default.
W2073324106 cites W1976692190 @default.
W2073324106 cites W1977196741 @default.
W2073324106 cites W1978637492 @default.
W2073324106 cites W1979304134 @default.
W2073324106 cites W1979643712 @default.
W2073324106 cites W1980078704 @default.
W2073324106 cites W1980684680 @default.
W2073324106 cites W1981488317 @default.
W2073324106 cites W1982081844 @default.
W2073324106 cites W1982689976 @default.
W2073324106 cites W1982735321 @default.
W2073324106 cites W1983053149 @default.
W2073324106 cites W1983521220 @default.
W2073324106 cites W1985781394 @default.
W2073324106 cites W1986719695 @default.
W2073324106 cites W1986813566 @default.
W2073324106 cites W1987995022 @default.
W2073324106 cites W1990714346 @default.
W2073324106 cites W1991010288 @default.
W2073324106 cites W1991131275 @default.
W2073324106 cites W1992867305 @default.
W2073324106 cites W1993508802 @default.
W2073324106 cites W1994587523 @default.
W2073324106 cites W1994827578 @default.
W2073324106 cites W1995249512 @default.
W2073324106 cites W1999352786 @default.
W2073324106 cites W1999544547 @default.
W2073324106 cites W2000838560 @default.
W2073324106 cites W2000882429 @default.
W2073324106 cites W2001784133 @default.
W2073324106 cites W2002258363 @default.
W2073324106 cites W2002502676 @default.
W2073324106 cites W2007210919 @default.
W2073324106 cites W2008436708 @default.
W2073324106 cites W2014007935 @default.
W2073324106 cites W2015379937 @default.
W2073324106 cites W2016038096 @default.
W2073324106 cites W2016875983 @default.
W2073324106 cites W2017731186 @default.
W2073324106 cites W2018709552 @default.
W2073324106 cites W2020868753 @default.
W2073324106 cites W2021396393 @default.
W2073324106 cites W2023056908 @default.
W2073324106 cites W2024949718 @default.
W2073324106 cites W2025953917 @default.
W2073324106 cites W2026771009 @default.
W2073324106 cites W2027290984 @default.
W2073324106 cites W2028405962 @default.
W2073324106 cites W2031054493 @default.
W2073324106 cites W2032041905 @default.
W2073324106 cites W2033576795 @default.
W2073324106 cites W2033754211 @default.
W2073324106 cites W2034085527 @default.
W2073324106 cites W2034656093 @default.
W2073324106 cites W2035652758 @default.
W2073324106 cites W2036951583 @default.
W2073324106 cites W2037467582 @default.
W2073324106 cites W2037574592 @default.
W2073324106 cites W2042092356 @default.
W2073324106 cites W2043250934 @default.
W2073324106 cites W2043638187 @default.
W2073324106 cites W2043957304 @default.
W2073324106 cites W2044772202 @default.
W2073324106 cites W2044808063 @default.
W2073324106 cites W2045374854 @default.
W2073324106 cites W2046136144 @default.
W2073324106 cites W2046315021 @default.
W2073324106 cites W2047398096 @default.
W2073324106 cites W2047503384 @default.
W2073324106 cites W2048271099 @default.
W2073324106 cites W2049231585 @default.
W2073324106 cites W2050588153 @default.
W2073324106 cites W2051132670 @default.
W2073324106 cites W2051691654 @default.