Safety and preliminary findings with the intravascular contrast agent NC100150 injection for MR coronary angiography

In this Phase I clinical study, a novel ultrasmall superparamagnetic iron oxide contrast agent, NC100150 Injection (Nycomed Imaging, Oslo, Norway, a part of Nycomed Amersham), was used in two-dimensional magnetic resonance coronary angiography (MRCA). Safety and imaging data were acquired from 18 healthy male volunteers at both 0.5 and 1.5 T, before and after the administration of NC100150 Injection. Through-plane and in-plane images of the right coronary artery were analyzed. The postcontrast imaging sequences used prepulses and a high flip angle, to introduce T1 weighting. At 1.5 T (TE 2.6 msec), the through-plane coronary artery signal-to-noise ratio (SNR) (P = 0.04), coronary artery-to-fat signal difference-to-noise ratio (SDNR) (P = 0.001), coronary artery-to-myocardium SDNR (P<0.001), and coronary artery delineation (P<0.001) were improved by the administration of NC100150 Injection. For in-plane imaging, coronary artery delineation improved, but there were no significant changes in the SNR and SDNR. At 0.5 T, with the longer TE (6.7 msec) imaging sequence used, there was a reduction in the SNR (P = 0.01), the fat SDNR (through-plane P = 0.02; in-plane P = 0.25), and the coronary artery diameter (P<0.01 in both imaging planes). There was a trend toward improvement in the myocardial SDNR and coronary artery delineation. In conclusion, NC 100150 Injection was given safely to 18 healthy subjects, with no major adverse reactions. Coronary artery delineation was improved in both imaging planes at 1.5 T, with a trend toward improvement at 0.5 T. At 1.5 T, with a short TE imaging sequence, the marked T1 shortening effects of NC100150 Injection were dominant, leading to an improvement in the quantitative parameters for the through-plane images. At 0.5 T, with a longer TE imaging sequence, the T2* effects of the contrast agent played a role in reducing the quantitative image parameters. With further optimization of imaging sequences, to take advantage of the long-lived intravascular T1 shortening effect of NC100150 Injection, further improvements in MRCA will be possible.     

NC100150-enhanced 3D-SPGR MR angiography of the common carotid artery in a pig vascular stenosis model. Quantification of stenosis and dose optimization.

PURPOSE: NC100150 is a new type of ultra-small iron oxide (USPIO) blood pool agent. The aim of this study was to compare NC100150-enhanced MR angiography (MRA) to time-of-flight (TOF) MRA, phase-contrast (PC) MRA, and digital subtraction angiography (DSA) in experimental stenoses in pigs, and furthermore to determine the optimal dose of the contrast agent. MATERIAL AND METHODS: An experimental stenosis of the right and left common carotid artery (CCA) was applied surgically in 6 Yorkshire pigs. DSA was performed as the gold standard, followed by 3D-TOF, 3D-PC, and NC100150-enhanced MRA. RESULTS: Eleven stenoses of the CCA were successfully applied. The degree of the stenosis, determined by NC100150-enhanced MRA, did not differ significantly from DSA, whereas TOF and PC MRA underestimated it. The image quality of the NC100150-enhanced MRA was superior to both TOF and PC MRA. The optimal dose of NC100150 was 5-6 mg Fe/kg, since higher doses did not further increase signal-to-noise ratio or contrast-to-noise ratio. There was a linear relationship between blood relaxation rate and contrast dose. CONCLUSION: NC100150-enhanced MRA has the potential for quantification of carotid stenoses and provides an alternative to DSA. The optimal dose of NC100150 was 5-6 mg Fe/kg.     

Correction for heart rate variability improves coronary magnetic resonance angiography

PURPOSE: To address degradation of coronary MR angiography (MRA) image quality due to heart rate variability (HRV)-associated variations in coronary artery position and motion. MATERIALS AND METHODS: Free-breathing navigator-gated and -corrected coronary MRA using subject-specific trigger delays and acquisition windows was combined with a real-time HRV correction algorithm, such as commonly used in left ventricular wall motion studies. Ten healthy adults underwent free-breathing navigator-gated and -corrected coronary MRA with and without HRV correction. Signal-to-noise (SNR), contrast-to-noise (CNR), vessel length, diameter, sharpness, and subjective image quality (on a five-point scale) were compared in a blinded fashion. RESULTS: Vessel sharpness improved significantly for both the left (LCA) and right (RCA) coronary artery systems (P = 0.016 and P = 0.015, respectively) with the use of HRV correction. Subjective image quality also improved significantly when HRV correction was used (P = 0.003). There were no significant differences with regard to SNR and CNR (P > 0.1). CONCLUSIONS: Preliminary results suggest that HRV correction improves objective and subjective image quality in coronary MRA. Continued studies in patients with known or suspected coronary artery disease are warranted to investigate the clinical impact of this technique.     

Intraindividual comparison of 3D coronary MR angiography and coronary CT angiography

RATIONALE AND OBJECTIVES: To compare the diagnostic value of magnetic resonance (MR) and computed tomography (CT) for the detection of coronary artery disease (CAD) with special regard to calcifications. MATERIALS AND METHODS: Twenty-seven patients with known CAD were examined with a targeted, navigator-gated, free-breathing, steady-state free precession MR angiography sequence (repetition time = 5.6 milliseconds, echo time = 2.8 milliseconds, flip angle 110 degrees ) and 16-slice coronary CT angiography. Segment-based sensitivity, specificity, and accuracy for the detection of stenoses larger than 50% were determined as defined by the gold standard catheter coronary angiography along with the subjective image quality (Grade 1-4). The degree of calcifications in each segment was quantified using a standard calcium scoring tool. RESULTS: Of 115 possible segments, 7% had to be excluded in MR imaging because of poor image quality. In CT, 3% were nondiagnostic because of image quality and 15% were not evaluable because of calcifications. Values for the detection of relevant coronary artery stenoses in the evaluated segments were: sensitivity: MR imaging 85% versus CT 96%; specificity: 88% versus 96%; accuracy: 87% versus. 96%. Average subjective image quality was 1.8 for MR imaging and 1.6 for CT. Of the 15% of segments that had to be excluded from CT evaluation because of calcifications, MR imaging provided the correct diagnosis segments in 67%. CONCLUSIONS: CT provided a better image quality with superior accuracy for the detection of CAD. Despite its overall inferiority, MR imaging proved to be helpful method in interpreting coronary stenosis in severely calcified segments.     

MRA of the lower extremities in patients with pulmonary embolism using a blood pool contrast agent: initial experience

PURPOSE: To evaluate the feasibility of blood pool contrast-enhanced magnetic resonance angiography (MRA) to visualize the arterial and venous vessel tree and to detect deep venous thrombosis (DVT) of the lower extremities. MATERIALS AND METHODS: Nine consecutive patients with pulmonary embolism (mean age = 46 +/- 9) were randomized to various doses of NC100150 (between 0.75 and 6 mg of Fe/kg of body weight). A T1-weighted (T1W) 3D gradient recalled echo (GRE) sequence (TE = 2.0 msec, TR = 5.0 msec) was used. Two observers blinded to the dose of contrast agent assessed image quality, contrast attenuation, and appearance of thrombi. RESULTS: Qualitative assessment of overall MRA image quality and semiquantitative vessel scoring revealed good to excellent delineation of venous and arterial vessel segments independent of the dose of NC100150. However, quantitative region of interest analysis revealed a significantly higher signal-to-noise ratio (SNR) in the high-dose group than in the mid- and low-dose groups of NC100150 (P < 0.01). Between dose groups, the SNR was independent of vessel type (artery or vein) and vessel segment localization (proximal or distal). All seven venous thrombi (mean length = 7.2 +/- 0.95 cm) were characterized by a very low signal intensity (SI), which was only 16.6 +/- 7% of the SI in adjacent venous segments (P < 0.0001). CONCLUSION: High-quality MR angiograms of the lower extremities can be obtained using low concentrations of NC100150 in combination with a strong T1W 3D GRE sequence. The obvious delineation of venous thrombi suggests that this technique may be potentially used as a noninvasive "one-stop shopping" tool in the evaluation of thromboembolic disease.     

MR coronary vessel wall imaging: comparison between radial and spiral k-space sampling

PURPOSE: To compare radial and spiral k-space sampling in navigator-gated ECG-triggered three-dimensional (3D) coronary vessel wall imaging. MATERIALS AND METHODS: The right coronary artery (RCA) vessel walls of eight healthy subjects were imaged using a modified double-inversion prepulse in concert with radial and spiral data acquisition. For data analysis, two investigators blinded to the sequence parameters subjectively assessed image quality in terms of artifacts and vessel wall visualization. Objective measures of the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and vessel wall definition were also determined. RESULTS: Radial k-space sampling demonstrated fewer artifacts and led to improved visualization of the coronary vessel wall compared to spiral imaging (P < 0.05). This finding was also reflected in a better vessel wall definition using radial data acquisition (P < 0.05). SNR and CNR were found to be higher when spiral k-space sampling was used (n.s.). CONCLUSION: Radial k-space sampling in concert with free-breathing navigator-gated cardiac-triggered MRI of the coronary vessel wall resulted in fewer motion artifacts and improved vessel wall definition compared to spiral k-space sampling. The proposed approach therefore appears to be preferable.     

Coronary artery disease: assessment with a comprehensive MR imaging protocol--initial results

A comprehensive magnetic resonance (MR) imaging protocol for assessment of coronary artery disease (CAD) is presented. The protocol includes multiphase gradient-echo cine MR imaging for assessment of cardiac function, first-pass myocardial perfusion imaging at rest and during adenosine stress, MR imaging with delayed contrast enhancement for assessment of myocardial viability, and coronary MR angiography with a three-dimensional respiratory navigator-gated technique. In 10 patients, the protocol was completed in 61.5 minutes +/- 5.5 and yielded high image quality and diagnostic accuracy. This protocol may provide an integrated noninvasive screening tool for patients with CAD.     

Impact of navigator timing on free-breathing submillimeter 3D coronary magnetic resonance angiography.

The purpose of this study was to investigate the impact of navigator timing on image quality in navigator-gated and real-time motion-corrected, free-breathing, three-dimensional (3D) coronary MR angiography (MRA) with submillimeter spatial image resolution. Both phantom and in vivo investigations were performed. 3D coronary MRA with real-time navigator technology was applied using variable navigator time delays (time delay between the navigator and imaging sequences) and varying spatial resolutions. Quantitative objective and subjective image quality parameters were assessed. For high-resolution imaging, reduced image quality was found as a function of increasing navigator time delay. Lower spatial resolution coronary MRA showed only minor sensitivity to navigator timing. These findings were consistent among volunteers and phantom experiments. In conclusion, for submillimeter navigator-gated and real-time motion-corrected 3D coronary MRA, shortening the time delay between the navigator and the imaging portion of the sequence becomes increasingly important for improved spatial resolution.     

Navigator-gated three-dimensional MR angiography of the pulmonary arteries using steady-state free precession

PURPOSE: To assess the quality of a navigator-gated, free breathing, steady-state free precession (SSFP) technique in comparison to a single breathhold for pulmonary artery imaging in normal volunteers. MATERIALS AND METHODS: Sagittal sections of the left pulmonary arteries of 10 volunteers were obtained with a three-dimensional SSFP sequence using both a single breathhold of 30 seconds and a navigator-gated version of the same sequence. The images were compared and rated by a blinded cardiovascular radiologist for image quality, sharpness, and artifact. RESULTS: On a scale ranging from -2 to 2, in which positive numbers denote that the navigator method was favorable compared to the single breathhold method, image quality was rated 0.7+/-1.4, sharpness 0.6+/-1.5, and artifact 0.1+/-1.4. Thus, there was no statistical difference between the two methods. CONCLUSION: The navigator-gated SSFP sequence is able to acquire images equal in quality to the breathhold sequence. This may be of clinical importance for pulmonary imaging in patients who are unable to sustain a long breathhold.     

Impact of bulk cardiac motion on right coronary MR angiography and vessel wall imaging

The purpose of this study was to investigate the impact of in-plane coronary artery motion on coronary magnetic resonance angiography (MRA) and coronary MR vessel wall imaging. Free-breathing, navigator-gated, 3D-segmented k-space turbo field echo ((TFE)/echo-planar imaging (EPI)) coronary MRA and 2D fast spin-echo coronary vessel wall imaging of the right coronary artery (RCA) were performed in 15 healthy adult subjects. Images were acquired at two different diastolic time periods in each subject: 1) during a subject-specific diastasis period (in-plane velocity <4 cm/second) identified from analysis of in-plane coronary artery motion, and 2) using a diastolic trigger delay based on a previously implemented heart-rate-dependent empirical formula. RCA vessel wall imaging was only feasible with subject-specific middiastolic acquisition, while the coronary wall could not be identified with the heart-rate-dependent formula. For coronary MRA, RCA border definition was improved by 13% (P < 0.001) with the use of subject-specific trigger delay (vs. heart-rate-dependent delay). Subject-specific middiastolic image acquisition improves 3D TFE/EPI coronary MRA, and is critical for RCA vessel wall imaging.     

Navigator-gated free-breathing three-dimensional balanced fast field echo (TrueFISP) coronary magnetic resonance angiography

RATIONALE AND OBJECTIVES: Recent developments of MR imaging equipment enabled high-quality steady state-free-precession (Balanced FFE, True-FISP) MR-imaging with a substantial 'T2 like' contrast, resulting in a high signal intensity of the blood-pool without the application of exogenous contrast agents. It is hypothesized that Balanced-FFE may be valuable for contrast enhancement in 3D free-breathing coronary MRA. MATERIALS AND METHODS: Navigator-gated free-breathing cardiac triggered coronary MRA was performed in 10 healthy adult subjects and three patients with radiograph defined coronary artery disease using a segmented k-space 3D Balanced FFE imaging sequence. RESULTS: High contrast-to-noise ratio between the blood-pool and the myocardium (29 +/- 8) and long segment visualization of both coronary arteries could be obtained in about 5 minutes during free breathing using the present navigator-gated Balanced-FFE coronary MRA approach. First patient results demonstrated successful display of coronary artery stenoses. CONCLUSION: Balanced FFE offers a potential alternative for endogenous contrast enhancement in navigator-gated free-breathing 3D coronary MRA. The obtained results together with the relatively short scanning time warrant further studies in larger patient collectives.     

Real-time motion correction in navigator-gated free-breathing double-oblique submillimeter 3D right coronary artery magnetic resonance angiography

RATIONALE AND OBJECTIVES: The purpose of this study was the investigation of the impact of real-time adaptive motion correction on image quality in navigator-gated, free-breathing, double-oblique three-dimensional (3D) submillimeter right coronary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Free-breathing 3D right coronary MRA with real-time navigator technology was performed in 10 healthy adult subjects with an in-plane spatial resolution of 700 x 700 microm. Identical double-oblique coronary MR-angiograms were performed with navigator gating alone and combined navigator gating and real-time adaptive motion correction. Quantitative objective parameters of contrast-to-noise ratio (CNR) and vessel sharpness and subjective image quality scores were compared. RESULTS: Superior vessel sharpness, increased CNR, and superior image quality scores were found with combined navigator gating and real-time adaptive motion correction (vs. navigator gating alone; P < 0.01 for all comparisons). CONCLUSION: Real-time adaptive motion correction objectively and subjectively improves image quality in 3D navigator-gated free-breathing double-oblique submillimeter right coronary MRA.     

Stress functional MRI: detection of ischemic heart disease and myocardial viability.

Breath-hold gradient-echo magnetic resonance imaging (MRI) in conjunction with pharmacologic dobutamine stress has become a practical tool to investigate patients with chest pain. The presence of high-grade coronary artery stenoses can be detected more accurately than with stress echocardiography. The main diagnostic advantage of MRI is in patients with suboptimal echocardiographic image quality. Depiction of left ventricular anatomy and function at rest and during low-dose dobutamine stress is also clinically useful for evaluating patients with severely impaired left ventricular function for the presence of residual myocardial viability. Recovery of regional and global left ventricular function can be accurately predicted by stress functional MRI. J. Magn. Reson Imaging 1999;10:667-675, 1999.     

Coronary MR angiography with steady-state free precession: individually adapted breath-hold technique versus free-breathing technique

PURPOSE: To compare image quality and coronary artery stenosis detection with breath-hold (BH) and free-breathing navigator-gated (NAV) coronary magnetic resonance (MR) angiography performed with the same imaging sequence (steady-state free precession) and identical spatial resolution in patients suspected of having coronary artery disease. MATERIALS AND METHODS: Forty consecutive patients suspected of having coronary artery disease underwent steady-state free precession MR imaging of the left or the right coronary artery twice. Correction of breathing motion was performed once with NAV and again with BH. Maximal BH duration and coronary artery rest period were individually determined, and duration of data acquisition was adapted (parallel imaging with different sensitivity encoding factors was used). Quantitative analysis of coronary MR angiography data was performed with multiplanar reformatting software to determine visual score for image quality, vessel sharpness, visible vessel length, and number of visible side branches. Diagnostic accuracy for detection of coronary stenosis of 50% or greater was determined in comparison with results of conventional invasive angiography. The two techniques were compared regarding differences in angiographic parameters with paired Student t testing. chi(2) or Fisher exact testing was used when appropriate. RESULTS: More coronary artery segments were assessable with NAV than with BH MR angiography (254 [79.4%] vs 143 [44.7%] of 320 segments). Overall sensitivity and specificity with NAV were 72% (26 of 36 segments) and 91.7% (200 of 218 segments), versus 63% (12 of 19 segments) and 82.3% (102 of 124 segments) with BH; NAV enabled correct diagnosis in 13% more segments. BH yielded nondiagnostic images in 14 patients, while NAV yielded diagnostic images in all patients. When these 14 patients were excluded, there was a significant increase in visual score for left (3.0 vs 2.4, P <.01) and right (3.3 vs 3.0, P <.05) coronary arteries and no significant difference in vessel sharpness but significant improvement in visible vessel length in left coronary artery (85.9 vs 71.4 mm, P =.003) and number of visible side branches in left (4.9 vs 3.9, P =.04) and right (2.8 vs 2.4, P =.04) coronary arteries on NAV images as compared with BH images. CONCLUSION: Free-breathing NAV was superior to BH coronary MR angiography in terms of image quality and diagnostic accuracy of stenosis detection.     

Single breath-hold extended free-breathing navigator-gated three-dimensional coronary MRA

PURPOSE: To acquire the center of k-space while extending three-dimensional free-breathing navigator-gated coronary magnetic resonance (MR) angiography by an initial single breath-hold. MATERIALS and METHODS: This approach was successfully applied in eight healthy adult subjects. Resulting images were compared with conventionally acquired free-breathing navigator-gated MR angiograms. RESULTS: The acquisition of k-space center during the single breath-hold resulted in a 26% increase (P < 0.05) of signal-to-noise ratio. Visible length of the right coronary artery, as well as contrast-to-noise ratio between the blood and the myocardial muscle, were identical. CONCLUSION: The breath-hold extension was shown to be a valuable technique that may be combined with first-pass contrast-enhanced MR imaging.     

Comparison of 3D segmented gradient-echo and steady-state free precession coronary MRI sequences in patients with coronary artery disease

OBJECTIVE: Our objective was to compare two state-of-the-art coronary MRI (CMRI) sequences with regard to image quality and diagnostic accuracy for the detection of coronary artery disease (CAD). SUBJECTS AND METHODS: Twenty patients with known CAD were examined with a navigator-gated and corrected free-breathing 3D segmented gradient-echo (turbo field-echo) CMRI sequence and a steady-state free precession sequence (balanced turbo field-echo). CMRI was performed in a transverse plane for the left coronary artery and a double-oblique plane for the right coronary artery system. Subjective image quality (1- to 4-point scale, with 1 indicating excellent quality) and objective image quality parameters were independently determined for both sequences. Sensitivity, specificity, and accuracy for the detection of significant (> or = 50% diameter) coronary artery stenoses were determined as defined in invasive catheter X-ray coronary angiography. RESULTS: Subjective image quality was superior for the balanced turbo field-echo approach (1.8 +/- 0.9 vs 2.3 +/- 1.0 for turbo field-echo; p < 0.001). Vessel sharpness, signal-to-noise ratio, and contrast-to-noise ratio were all superior for the balanced turbo field-echo approach (p < 0.01 for signal-to-noise ratio and contrast-to-noise ratio). Of the 103 segments, 18% of turbo field-echo segments and 9% of balanced turbo field-echo segments had to be excluded from disease evaluation because of insufficient image quality. Sensitivity, specificity, and accuracy for the detection of significant coronary artery stenoses in the evaluated segments were 92%, 67%, 85%, respectively, for turbo field-echo and 82%, 82%, 81%, respectively, for balanced turbo field-echo. CONCLUSION: Balanced turbo field-echo offers improved image quality with significantly fewer nondiagnostic segments when compared with turbo field-echo. For the detection of CAD, both sequences showed comparable accuracy for the visualized segments.     

Three-dimensional cardiac cine magnetic resonance imaging with an ultrasmall superparamagnetic iron oxide blood pool agent (NC100150)

The purpose of this study was to assess image quality of three-dimensional (3D) cardiac cine magnetic resonance (MR) imaging before and after administration of a T1-shortening ultrasmall superparamagnetic iron oxide blood pool agent (NC100150). 3D cardiac cine MR imaging was performed in 13 volunteers using a radiofrequency-spoiled cardiac-gated 3D cine gradient-echo sequence with short repetition and echo times. Compared with precontrast images, postcontrast images showed no enhancement in fat and skeletal muscle, moderate enhancement in myocardium, and significant enhancement in ventricular cavity. After contrast injection, the signal ratio of the ventricular chamber to the myocardium significantly increased, and dramatic improvements were seen in the quality of the cineangiographic images and the depiction of cardiac valves. This quantitative study has shown that 3D cardiac cine MR imaging using a blood pool agent provided MR ventriculography and cineangiography with excellent image quality.     

High in-plane resolution T2-weighted magnetic resonance imaging of acute myocardial ischemia in pigs using the intravascular contrast agent NC100150 injection

RATIONALE AND OBJECTIVES: The intravascular contrast agent NC100150 injection was tested for its ability to demarcate nonperfused myocardium in a porcine model of coronary occlusion. MATERIALS AND METHODS: A T2-weighted fast spin echo sequence was acquired ex vivo and in vivo during first pass and steady-state circulation of the contrast agent in 2 dosages (2 and 5 mg Fe/kg bw) or saline. RESULTS: Ex vivo, in the high-dose group, the volume of nonperfused myocardium determined from T2-weighted images was 99% of that determined from photographs where perfused myocardium stained with fluorescein. A significantly higher contrast to noise ratio between perfused and nonperfused myocardium was found (both ex and in vivo in steady state) compared with the control group. During first pass, a significant reduction in signal intensity (74 +/- 18%) was found in perfused myocardium after contrast injection. CONCLUSION: NC100150 injection, combined with T2-weighted turbo spin echo imaging, allowed detailed visualization of non-perfused myocardium in the steady state, which corresponded to the area at risk as determined by fluorescein.     

64排螺旋CT冠状动脉成像的前瞻性与回顾性心电门控技术的图像质量及辐射剂量的比较研究

目的 研究前瞻性心电门控触发(prospective ECG-triggering)与回顾性心电门控(retrospective ECG gating)两种技术方法行冠状动脉CTA检查时,对冠状动脉图像质量及辐射剂量的比较。方法 33名疑似冠状动脉疾病的患者分两组进行对比研究。前瞻组16例为前瞻性心电门控成像,心率小于65次/min;回顾组17例为回顾性心电门控成像,心率小于75次/min。记录两组的辐射剂量并统计分析,同时进行图像质量评价。结果 两组图像质量比较,差异无统计学意义(P＞0.05)。前瞻性心电门控冠状动脉CTA的平均DLP 234.4mGy·cm,占回顾性心电门控冠状动脉CTA的平均DLP974.4mGy·cm的24.1%。前瞻性心电门控冠状动脉CTA的患者的平均有效剂量为3.2mSv,回顾心电门控冠状动脉CTA患者的为13.6mSv,降低76.47%。结论 64排螺旋CT在前瞻性心电门控冠状动脉CTA与回顾性心电门控冠状动脉CTA比较可以获得相似的图像质量,可大幅降低患者的有效剂量对于不能接受高辐射剂量且心率较低的受检人群具有重要的临床价值。     

Evaluation of free-breathing three-dimensional magnetic resonance coronary angiography with hybrid ordered phase encoding (HOPE) for the detection of proximal coronary artery stenosis.

We evaluated free-breathing, prospective navigator-gated, three-dimensional (3D) magnetic resonance coronary angiography (MRCA) with hybrid ordered phase-encoding (HOPE), in the detection of proximal coronary artery stenosis. The coronary arteries were imaged in 46 patients undergoing cardiac catheterization. The mean scan time was 48 minutes. The mean arterial length (mm) visualized was left main stem (LMS) 11.7 (SD 4.5), left anterior descending (LAD) 30.1 (SD 11.1), circumflex (LCx) 15.5 (SD 8.6), and right (RCA) 56.2 (SD 20.8). Twenty-three patients had coronary artery disease with 47 significant stenoses on cardiac catheterization. All LMS were normal on both catheterization and MRCA. MRCA sensitivity was highest for the LAD (89% CI 65%-99%) and RCA (76% CI 50%-93%), but lower for the LCx (50% CI 21%-79%). Specificity ranged from 72%-100%. Improvements in image quality, length of vessel seen, and specific imaging of the LCx are required for MRCA to become an alternative to cardiac catheterization.