Original Research

InvitedCoronary MRA: A Clinical Experiencein the United States

Peter G. Danias, MD, PhD,1* Matthias Stuber, PhD,1,3 Robert R. Edelman, MD,2

and Warren J. Manning, MD1,2

SINCE THE LATE 1980s, when MR imaging was firstreported to visualize the ostia of the coronary arteries(1,2), tremendous progress has occurred in the field ofcoronary MR angiography (MRA). Among these earlystudies, using electrocardiographic (ECG) gating withconventional spin-echo techniques but no compensa-tion for respiratory motion, Lieberman et al. (1) wereable to visualize small portions of the coronary arteriesin approximately 30% of patients undergoing cardiacMR imaging. Paulin and colleagues (2) used similarmethodology to examine the aortic root in six patientswith angiographically documented coronary disease.MR data were acquired during systole. In all cases theinvestigators were able to visualize the left main coro-nary ostia (including up to 3 cm of the left anteriordescending coronary artery [LAD] in one case), while theright coronary artery (RCA) ostium was identified inonly four subjects. Although no coronary stenoses wereidentified in these early studies, the potential of MRimaging to assess the anatomy of the coronary vesselswas demonstrated, cultivating further interest in thisfield.

Coronary MRA has several advantages and greatpotential as a noninvasive diagnostic tool: it offers highspatial resolution; can survey in any image plane; doesnot involve exposure to potentially harmful ionizingradiation; and has no known short- or long-term sideeffects. Competing noninvasive coronary imaging tech-nologies, including echocardiography and computer-ized tomography, are more limited, due to poor penetra-tion or resolution for the former and the need forpotentially harmful ionizing radiation exposure andiodinated intravenous contrast administration for thelatter. Thus, coronary MRA has emerged as one of themost promising technologies for the noninvasive visual-

ization of the coronary circulation and as a potentialfuture noninvasive alternative to diagnostic X-ray con-trast coronary angiography.

The segmented k-space strategies revolutionized thefield of coronary MRA. By rapidly acquiring multiplephase-encoding steps during each heartbeat, the acqui-sition of one two-dimensional (2D) image during 16heartbeats became possible, thus allowing the use ofbreath-holding as a means for respiratory compensa-tion. This technique was first described in animals byBurstein (3) and subsequently in humans by Edelmanand colleagues (4). Using this strategy, the data areacquired during an acquisition window of approxi-mately 100 msec during diastole, a period of relativebulk cardiac diastasis (so that cardiac motion would beminimized), but with relatively high coronary bloodflow. Eight interleaved phase-encoding steps are ac-quired during each cardiac cycle, necessitating 16 suc-cessive heartbeats to fill a 128 3 256 matrix. Thisapproach allows each 2D image to be acquired during asingle 15–20 second breath-hold, which is employed tominimize respiratory motion artifacts. Other imagingparameters included fat suppression, 3–4 mm slicethickness, and an in-plane spatial resolution of 1.9 3

0.9 mm (4–8).The 2D approach described above takes full advan-

tage of the inflow-related contrast between coronaryblood and surrounding stationary tissues. However, 2Dapproaches are limited by the tortuous nature of thecoronary vessels: focal signal loss related to the devia-tion of the coronary artery out of the image plane may bemisinterpreted as a focal stenosis. Signal-to-noise ratio(SNR) constraints and registration errors related toinconsistency between serial breath-holds are addi-tional impediments to 2D breath-hold coronary MRA.With the development of enhanced gradient systemsand the improvement in the operating software, respira-tory compensated 3D coronary MRA approaches be-came widely available. 3D coronary MRA overcomesseveral of the limitations of 2D techniques and hassignificant advantages, including enhanced SNR andimproved slice registration. Additionally, thinner adja-cent slices can be obtained and the image data can bepost-processed in any orientation. However, 3D ap-

1Charles A. Dana Research Institute and the Harvard-Thorndike Labo-ratory, Department of Medicine, Cardiovascular Division, Beth IsraelDeaconess Medical Center and Harvard Medical School, Boston, Massa-chusetts 02215.2Department of Radiology, Beth Israel Deaconess Medical Center andHarvard Medical School, Boston, Massachusetts, 02215.3Philips Medical Systems, Best, The Netherlands.*Address reprint requests to: P.G.D., Beth Israel Deaconess MedicalCenter, 330 Brookline Avenue, Boston, MA 02215.Received June 7, 1999; Accepted June 28, 1999.

JOURNAL OF MAGNETIC RESONANCE IMAGING 10:713–720 (1999)

r 1999 Wiley-Liss, Inc. 713

proaches for coronary MRA often offer a lower contrast-to-noise ratio (CNR) because of attenuated blood-infloweffect. Thus, the use of contrast agents for 3D coronaryMRA techniques may have greater potential than for 2Dapproaches. With advanced acquisition schemes, suchas spiral imaging, or more conventional free-breathingapproaches with navigator gating and prospective slicecorrection, submillimeter spatial resolution has beenachieved (9,10) (Figs. 1, 2). The addition of other en-hancements, such as spin-locking (11), magnetizationtransfer (12–14) and T2 preparation pre-pulses (15–17),and the shortening of the data acquisition window, haveoffered improved CNR and sharper vessel border defini-tion (16).

CONTRAST-ENHANCED CORONARY MRA

The use of intravenous contrast agents for coronaryMRA has several theoretical advantages. With the use ofMR contrast agents, the T1 relaxation of blood can bedrastically shortened, allowing for increased CNR forcoronary MRA (18,19). Several contrast agents havebeen used for this purpose, including extracellularagents, such as gadopentate diglumine (Magnevist;Berlex Laboratories, Wayne, NJ), gadodiamide (Omnis-can; Nycomed-Amersham, Buckinghamshire, UK), andgadotetriiol (Prohance; Bracco Diagnostics, Princeton,NJ), and intravascular agents, such as iron oxide (AMI227; Advanced Magnetics, Cambridge, MA), MS-325(Angiomark; EPIX Medical, Cambridge, MA/Mallink-rodt, St. Louis, MO), and NC100150 (Clariscan; Ny-comed-Amersham, Buckinghamshire, UK) (18–22).

Because extracellular agents quickly distribute in theextravascular space, their use requires rapid first-passimaging (when the signal from the surrounding tissuesis still low), and thus necessitates breath-holding (23).

To allow imaging with non-breath-hold equilibriumapproaches, slow infusion of gadolinium has been pro-posed (24,25). First-pass coronary MRA with extravas-cular contrast agents is also limited by the need for

Figure 1. High-resolution image (0.5 3 0.5 mm) of the RCA (arrowheads) of a normal volunteer. The reformatted image (rightlower frame) shows a long portion of the vessel (arrows) including the proximal and mid-portions of the vessel. Part of the LCx isalso visualized (arrows, left upper panel). (Reprinted with permission).

Figure 2. High-resolution coronary MRA of a normal volun-teer (resolution 0.64 3 0.64 mm2), acquired in one 14-heartbeat breath-hold with spiral imaging. Long segments ofthe first-order diagonal branches (white arrows) are visualized.The LAD (black arrow), ascending aorta (AAo), and rightventricular outflow tract (RVOT) are also labeled. (Courtesy ofDrs. McConnell, Meyer, and Hu, Stanford University, Stanford,CA.)

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repeat contrast injections when more than one slabis imaged. With each subsequent injection the CNR willbe lower, as the signal from the extracellular spacecontinuously increases following initial contrast admin-istration. Although acquisition of image data duringmultiple (different) parts of the cardiac cycle for differentslabs may provide a solution to the need for repeatinjections, the experience with such techniques is stilllimited.

The use of intravascular agents has the inherentadvantage of allowing image acquisition over longertime periods after the injection of the intravenous con-trast. Thus non-breath-hold schemes can be employed(see below), and repeat scans have similar CNRs with-out the need for repeat injections. Experience withintravascular contrast agents is still limited (18–22),and phase II clinical trials of the efficacy and safety ofthese agents are currently under way.

BREATH-HOLD CORONARY MRA

Among the major limitations of coronary MRA are theartifacts resulting from bulk cardiac motion associatedwith respiration. These result in ghosting, blurring, andimage degradation, which compromises visualization ofthe coronary arteries and assessment of focal stenoses.To compensate for respiratory motion, breath-holdingwas implemented early to allow for ‘‘freezing’’ of respira-tory motion. 2D breath-hold coronary MRA relied onacquiring contiguous images, with the goal of surveyingthe proximal segments of the coronary arteries in aseries of successive breath-holds. More recently, 3Dbreath-hold techniques for coronary MRA have alsobeen implemented (12,23,26–28) and are currently un-der investigation. Breath-hold approaches offer the ad-vantage of rapid imaging and are technically easy toimplement in compliant subjects. For coronary MRAtechniques that utilize the first-pass contrast enhance-ment of intravenously injected extracellular contrastagents, breath-holding is a requirement at the presenttime.

However, breath-holding strategies have several limi-tations. Patients with cardiac or pulmonary diseasefrequently have difficulty sustaining adequate breath-holds, particularly when the duration exceeds a fewseconds. Alternative breath-holding techniques, includ-ing multiple brief breath-holds (29) and coached breath-holding with visual or audible feedback (30,31) havebeen used to minimize respiratory motion artifacts andpatient inconvenience but are only useful for well-motivated subjects. Similarly, the use of respiratorymaneuvers (hyperventilation, oxygen supplementation)to facilitate and prolong breath-holding has been exam-ined but may not be applicable to all patients (32).Additionally, it has been shown that during a sustainedbreath-hold there is cranial diaphragmatic drift (32),which may contribute to image degradation. Amongserial breath-holds, the diaphragmatic and cardiac po-sition frequently vary by up to 1 cm, resulting inregistration errors (30,31). Misregistration results inapparent gaps between the segments of the visualizedcoronary arteries, which could be misinterpreted as

signal voids from coronary stenoses. Finally, theuse of signal enhancements, such as signal averag-ing, is significantly restricted from the durationof breath-holding. Thus, while breath-hold strategiesare often successful with motivated volunteers, theirapplicability to the broad range of patients, and espe-cially those with cardiovascular disease, is more lim-ited.

NON-BREATH-HOLD APPROACHES

To overcome limitations associated with breath-hold-ing, methods have been developed to allow for free-breathing coronary MRA. Respiratory belts/bellows havebeen used to monitor chest wall expansion and therebygate image acquisition to end-expiratory (minimal expan-sion) position. Coronary MRA using such devices hasbeen shown to be both feasible and practical(7,31,33,34). As the dwell time of the diaphragms islongest during expiration (35), typically the expiratoryphase is utilized for image data acquisition. How-ever, respiratory gating with respiratory belts is notconsistently reliable, and the temporal relationshipbetween chest wall expansion and diaphragmatic mo-tion may not be constant, thereby introducing motionartifacts.

As an alternative for respiratory gating, MR naviga-tors, which provide positional information about mov-ing structures, have been implemented for cardiac MRimaging and coronary MRA. With vertical positioning ofthe navigator on the dome of the right hemidiaphragm(lung-liver interface), the diaphragmatic craniocaudaldisplacement can be monitored. These data can be usedto gate coronary MRA acquisitions, assuming a goodcorrelation between coronary and diaphragmatic posi-tion throughout the respiratory cycle. Alternate loca-tions for navigator positioning, such as the left hemidia-phragm or the base of the heart have been investigated,but no significant advantages have been demonstrated(36,37). Because of ease of identification and implemen-tation, positioning of the navigator on the dome of theright hemidiaphragm is currently the preferred ap-proach. Similar to bellows gating, data are typicallyacquired during expiration, and the gating process canbe either prospective (ie, before data acquisition) orretrospective (ie, following data acquisition, but beforeimage reconstruction). Although navigator approachesgreatly improve patient comfort and do not requiresignificant subject motivation, obtaining high-qualityimages requires the use of a narrow gating respiratorywindow, thereby accepting data at a very narrow rangeof diaphragmatic (and presumably cardiac) displace-ment. This inadvertently prolongs the scan duration.During long scans, the diaphragm tends to drift, usuallyto a more cranial position (35), resulting in both adecrease in scan efficiency and image degradation. Toovercome problems associated with narrow gating win-dows and prolonged scans, coronary MRA with prospec-tive navigator correction has been implemented and hasbeen shown to maintain or improve image quality bothfor 2D and 3D approaches of coronary MRA (9,38,39). Other approaches to compensate for respiratory

Coronary MRA 715

motion and improve scan efficiency have also beendescribed and include the diminishing variance algo-rithm (40,41), phase reordering (42,43), and linearphase shift (44).

FAST IMAGING APPROACHES

An alternative method to compensate for respiratorymotion, and thus to allow for free breathing coronaryMR imaging, would be to decrease the acquisition timeso that the entire data set is obtained in two to fourcardiac cycles. The development of such rapid strate-gies is an active field of research in cardiac MRA.Although only preliminary data were recently reportedfor fast coronary MRA (45), these approaches, which arebased on parallel acquisition schemes, have been shownto decrease image time by a factor of up to 7 (46) andhold a great potential. Parallel acquisition utilizes thevariable sensitivities of component coils, which dependon the individual coil position, to render spatial imageinformation (47,48).

VISUALIZATION OF NORMALCORONARY ARTERIES

Coronary MRA is challenging because of the complex3D structure of the coronary tree, the surroundingepicardial fat, and the adjacent large blood pools (car-diac atria and ventricles). Additionally, the heart is a‘‘moving target,’’ as it changes position and shape dur-ing ventricular contraction and is subject to bulk mo-tion with unrestricted respiration.

The identification of the native coronary vessels isnow feasible in the vast majority of compliant individu-als. A summary of recently published papers from U.S.centers validating 2D and 3D techniques for visualiza-tion of coronary arteries in healthy volunteers andpatients with CAD is presented in Table 1. A largenumber of abstracts have also recently been reported,indicating ongoing interest in this field. Several non-U.S. (mostly European) centers have also reportedsimilar data. In general, the LAD and the RCA arerelatively easier to image compared with the left circum-flex artery (LCx), due to their less tortuous and morepredictable course and their closer proximity to thereceiver coil. Consequently, the length of the LAD andRCA visualized in several studies is typically longer thanthat of the LCx, ranging from 24 to 116 mm for the LAD,34 to 126 mm for the RCA, and 11 to 97 mm for the LCx(5,6,8,14,49,50).

In normal subjects, the diameter of the coronaryvessels as determined by coronary MRA is similar toX-ray angiographic and reference anatomic data (5,51–53). Thus, at the present time coronary MRA has beenshown to visualize reliably the proximal coronary arter-ies, and their course and relationship with surroundingstructures, and to render information about normalvessel diameter, suggesting possible utility for assess-ment of coronary artery disease (CAD).

CORONARY MRA FOR ANOMALOUSCORONARY ARTERIES

Identification of coronary anomalies and definition ofthe course of these anomalous vessels is easily obtain-able by current coronary MRA methods. Coronaryanomalies occur in 1% of the population. Most are notassociated with adverse events or decreased survival.However, certain types of coronary anomalies have beenassociated with premature sudden cardiac death ormyocardial infarction. These ‘‘malignant’’ anomaliesoccur when the anomalous vessel (left or right coronaryartery) courses between the aorta and the main pulmo-nary artery. It has been hypothesized that coronaryblood flow can be compromised when the anomalousvessel is compressed by these great thoracic vessels,resulting in ischemia, infarction, arrhythmias, andeven sudden death (54). The ability of coronaryMRA to identify the proximal coronary vessels reliably,coupled with the inherent 3D nature of MR imagingand the ability to generate tomographic images in anyorientation, renders this technique uniquely suitedfor the noninvasive study of anomalous coronaryarteries. For example, in the case of origin of theleft coronary artery from the right sinus of Valsalvawith subsequent passage of the vessel between theaorta and right ventricular infundibulum, the definitionof the subsequent course of the coronary artery (ante-rior or posterior to the right ventricular outflow tract) isreadily available by coronary MRA but may often bechallenging and difficultwith conventional X-ray angio-graphic methods. Our group (55) has reported on aseries of 16 patients with coronary anomalies, in whomcoronary MRA consistently demonstrated the anatomicrelationships of these vessels. Other European centershave also reported similar findings and have validatedcoronary MRA as the current noninvasive gold-stan-dard for assessment of this uncommon abnormality(56,57).

IDENTIFICATION OF CORONARY ARTERYSTENOSES BY MRA

Although current breath-hold coronary MRA tech-niques have relatively limited in-plane spatial resolu-tion, the technique has been shown to identify proximalcoronary stenoses in several clinical series. Gradient-echo techniques depict focal stenoses as signal voids. Inone of the earliest studies, we reported on the clinicalapplication of coronary MRA in a cohort of 39 patientsreferred for elective coronary angiography, who alsounderwent coronary MRA either immediately before, orafter conventional X-ray contrast angiography (58). Forthis study, a segmented k-space 2D breath-hold ECG-gated gradient-echo sequence was used. Individual epi-cardial coronary arteries were qualitatively graded in ablinded fashion as either having or not having signifi-cant disease. Coronary MRA images of 98% of the majorepicardial arteries were adequate for evaluation. Overallsensitivity and specificity of the 2D coronary MRAtechnique for correctly classifying individual vessels ashaving or not having significant CAD (.50% diameter

716 Danias et al.

stenosis on conventional contrast angiography as-sessed visually) were 90% and 92%, respectively. Subse-quent studies in the United States (59,60) and abroad(50,61–63) have reported variable sensitivity and speci-ficity values for the detection of significant CAD. Expla-nations for this variability include differences in MRsequence, inadequate patient cooperation with breath-holding, or irregular rhythms, all of which contribute toimage degradation. Finally, coronary MRA has beenshown to identify correctly infarct-related coronary ar-tery patency and presence of collateral blood flow lateafter myocardial infarction (34). Newer non-breath-holdapproaches for 3D coronary MRA have demonstrated

the ability of this technique to detect coronary stenoses(9,16) (Fig. 3).

MRA OF STENTED CORONARY ARTERIESAND CORONARY ARTERY BYPASS GRAFTSAND AFTER OTHER CARDIAC SURGERY

The presence of metallic objects in the imaging fieldresults in local susceptibility artifacts. Imaging of coro-nary stents has been shown to be safe, as neithermotion (64) nor local tissue warming (65) are of particu-lar concern. However, the image artifact from currentcoronary stents makes the visual assessment of steno-

Table 1Current U.S. Experience (Peer-Reviewed Publications) of Coronary MRA in Humans*

Investigator Technique Resp. comp.Subjects

(no.)Sensitivity[% (range)]

Specificity[% (range)]

Paulin et al, 1987 (2) 2D spin echo None P (6) — —Edelman et al, 1991 (4) 2D GRE BH V (22) N/A N/ACho et al, 1991 (33) 2D TOF Resp. belt V N/A N/AWang et al, 1991 (75) 2D IR BH V N/A N/ADoyle et al, 1993 (29) 2D GRE Coached BH V N/A N/AMeyer et al, 1992 (76) 2D spiral BH V, P N/A N/AManning et al, 1993 (5) 2D GRE BH V (19), P (6) — —Manning et al, 1993 (58) 2D GRE BH P (39) 90 (71–100) 92 (78–100)Pascal et al, 1993 (14) 3D TOF MT None V (7), P (7) — —Li et al, 1993 (13) 3D GRE MT None V (14) N/A N/ALiu et al, 1993 (30) 2D GRE BH V (6) N/A N/ASakuma et al, 1994 (77) 2D GRE BH V (18) N/A N/ADuerinckx and Urman, 1994 (60) 2D GRE BH P (20) 63 (0–73) (37–82)Brittain et al, 1995 (15) Spiral BH N/A N/AHofman et al, 1995 (8) 2D GRE BH V (10) N/A N/A

3D GRE Retro. Nav. G3D GRE None

Hundley et al, 1995 (34) 2D GRE cine Resp. belt P (18) s/p MI 100 (artery patency) —McConnell et al, 1995 (55) 2D GRE BH P (16) 88 (anomalous cor.) N/AWang et al, 1995 (31) 2D GRE Resp. bellows V (11) N/A N/AWang et al, 1995 (26) 3D GRE Coached BH V (6) N/A N/ADavis et al, 1996 (78) 2D GRE BH V (16), P (18) s/p OHT 78 —Li et al, 1996 (49) 3D GRE Retro. Nav. G V (12) P (1) N/A N/AOshinski et al, 1996 (7) 2D GRE Prosp. Nav. G V (20) P (11) — —

Resp. bellowsBH

Wang et al, 1996 (79) 3D GRE Resp. Nav. G V (6) N/A N/ACoached BHNone

Duerinkcx, 1997 (80) 2D GRE BH V (8) N/A N/AMcConnell et al, 1997 (36) 2D GRE BH V (10) N/A N/A

Prosp. Nav. GDanias et al, 1997 (38) 2D GRE Prosp. Nav. G V (12) N/A N/A

Prosp. Nav. G/CProsp. Nav. C

Oshinski et al, 1998 (39) 2D GRE Prosp. Nav. G/C P (13) — —Woodard et al, 1998 (81) 3D GRE Retro. Nav. G P (10) 70–73 —Duerinckx, 1998 (82) 2D GRE BH P (16) s/p stent — —Stuber et al, 1999 (9) 3D GRE Prosp. Nav. G/C V (15), P (7) — —Stuber et al, 1999 (83) 3D GRE Prosp. Nav. G/C V (8) N/A N/AStuber et al, 1999 (28) 3D GRE BH 1 Prosp. Nav. G/C V (5) N/A N/ABotnar et al, 1999 (16) 3D GRE Prosp. Nav. G/C V (8), P (5) — —Stillman et al, 1996 (20) 3D TOF/iron oxide (AMI 227) P (9) — —Goldfarb et al, 1998 (23) 3D GRE/Gd-DTPA BH V (4) N/A N/A

*GRE 5 gradient echo, TOF 5 time of flight, MT 5 magnetization transfer, IR 5 inversion recovery, Resp. 5 respiratory, Comp 5

compensation, Prosp. 5 prospective, Retro 5 retrospective, Nav. 5 navigator, G 5 gating, C 5 correcting, BH 5 breath-hold, V 5 volunteer,P 5 patient, N/A 5 not applicable, s/p 5 status post, MI 5 myocardial infarction, OHT 5 orthotopic heart transplantation, cor 5 coronary.

Coronary MRA 717

ses within the stented segment impossible. Recentreports have used blood flow velocity information toderive stent patency but until MR-‘‘friendly’’ stents areavailable, the presence of coronary stents will remain animpediment for evaluation of coronary stenoses in thispopulation.

Coronary artery bypass grafts including saphenousvein and internal mammary grafts are relatively easy toimage, due to their relatively stationary position andlarger vessel diameter. Furthermore, their predictableand less convoluted course has allowed imaging ofbypass grafts even with conventional MR techniques.Both ECG-gated spin-echo (66–69) and gradient-echo(69–71) techniques have been used to assess bypassgraft patency. By visualizing the graft in at least twolocations along its expected course (presenting as signalvoid for spin-echo techniques and bright signal forgradient-echo approaches), one can conclude that thereis flow present through the bypass graft, and thereforethat it is patent. If (for spin-echo techniques) a signalvoid is seen at only one level, a graft is considered‘‘indeterminate,’’ and if no signal voids are identified thegraft is considered to be occluded. Contrast-enhancedcoronary MRA has also been described for the assess-ment of graft patency (72–74). An overview of the clinicalstudies in the United States assessing bypass graftpatency is presented in Table 2.

Limitations of bypass graft imaging include the localsignal loss/artifact associated with implanted metallicobjects such as hemostatic clips, graft locating rings,sternal wires, coexistent prosthetic valves, and support-ing struts or rings. In addition, the presence of a severe

stenosis may impede blood flow through the graft tosuch a degree that the MR contrast could be insufficientto suggest patency (66). The evaluation of focal stenosesof either the bypass graft itself or of the anastomotic siteto the native coronary artery is also subject to the samelimitations described earlier for imaging of native coro-nary vessels.

SUMMARY

Coronary MRA is an evolving technology and at thepresent time allows the visualization of the proximalcoronary arteries. It is becoming an accepted clinicaltechnology for the identification and definition of anoma-lous coronary arteries and compares favorably withother noninvasive and invasive approaches. The utilityof coronary MRA for assessment of native coronaryartery stenoses is still the focus of intense investigationand evolution. Several competing approaches have beendescribed and are being evaluated for diagnosis of CADin native coronary arteries, and coronary bypass grafts.Technical and methodological improvements and a moreeducated application of our knowledge regarding car-diac and respiratory physiology will allow for improvedspatial resolution and ultimately better visualization ofthe coronary arteries. Multicenter trials are currentlyunder way to investigate the clinical utility of severalimaging strategies. As a clinical tool, coronary MRA willhave to prove that it is fast, robust, and easily acceptedby patients and physicians.

Figure 3. Coronary MRA (A,B) and correspond-ing X-ray angiogram (C) in a patient with RCAdisease. Focal stenoses present in the proximaland mid-portion of the vessel (arrows) arereadily detected as signal loss on the coronaryMRA. (Reprinted with permission).

Table 2Current U.S. Experience (Peer-Reviewed Publications) of Coronary MRA in Patients With Coronary Artery Bypass Grafts*

Investigator TechniqueRespiratory

compensationSubjects/

graftsSensitivity

(%)Specificity

(%)

Rubinstein et al, 1987 (66) SE Respiratory bellows 20/47 90 72White et al, 1987 (67) SE None 25/72 86 72White et al, 1988 (70) 2D GRE None 28/28 93 86Aurigemma et al, 1989 (71) Cine GRE None 20/45 88 100Vrahliotis et al, 1997 (73) 3D GRE/gadopentate Breath-holding 15/45 93 97

*The sensitivity/specificity values reflect graft patency. Abbreviations: SE 5 spin echo, GRE 5 gradient echo.

718 Danias et al.

ACKNOWLEDGMENTS

Dr. Danias is supported in part by the Clinical Investiga-tor Training Program at the Beth Israel DeaconessMedical Center and Harvard Medical School/Massachu-setts Institute of Technology, Boston, MA. Dr. Manningis supported in part by an Established InvestigatorGrant of the American Heart Association, Dallas, TX(9740003N).

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