Gadolinium-enhanced, vessel-tracking, two-dimensional coronary MR angiography: single-dose arterial-phase vs. delayed-phase imaging

The purposes of our study were to investigate the benefits of using a single dose of an extracellular contrast agent for coronary magnetic resonance angiography (CMRA) and to determine the relative benefits of arterial-phase vs. delayed-phase image acquisition. The right coronary artery was imaged in 10 healthy adults using a breath-hold, two-dimensional fast gradient echo pulse sequence designed for vessel tracking (multiphase, multislice image acquisition). Pre- and postcontrast CMRA was performed. Postcontrast imaging consisted of arterial- and delayed-phase CMRA following a 15 mL bolus (single dose) of contrast media and of delayed-phase imaging following a cumulative 45 mL contrast dose (triple dose). Contrast-enhanced CMRA provided a significantly higher (P < 0.001) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than noncontrast CMRA. CNR was highest for single-dose arterial-phase CMRA (13.1 +/- 4.5) and triple-dose delayed-phase CMRA (13.0 +/- 4.8), followed by single-dose delayed-phase CMRA (8.4 +/- 3.5) and noncontrast CMRA (4.2 +/- 1.8). Single-dose arterial-phase CMRA provided the best visualization of the distal right coronary artery and was preferred for blinded physician assessments. We concluded that utilization of a single dose of extracellular contrast media improves CMRA, especially if timed for arterial-phase imaging. J. Magn. Reson. Imaging 2001;13:682-689.     

Dynamic coronary MR angiography and first-pass perfusion with intracoronary administration of contrast agent

PURPOSE: To evaluate whether dynamic imaging of the coronary arteries can be performed with intracoronary infusion of low-dose gadolinium (Gd)-based contrast agent and assess the effect of long duration and multiple infusions on the image signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). MATERIALS AND METHODS: Dynamic coronary magnetic resonance (MR) imaging (130 msec/image) and contrast agent first pass myocardial perfusion studies were performed with intracoronary infusions of low-dose Gd-based MR contrast agent on dogs (N = 4) using a fast multislice gradient recalled echo (GRE) sequence. RESULTS: Contrast-enhanced coronary arteries were clearly imaged during infusion periods as long as 2.3 minutes. The SNR and CNR of the contrast-enhanced coronary arteries remained essentially unchanged over multiple consecutive angiographic sessions. In addition, we demonstrated that first pass studies performed with intracoronary injection of MR contrast agent can be used as a means of assessing regional myocardial perfusion. CONCLUSION: These studies demonstrated that, using intracoronary infusion of Gd, coronary magnetic resonance angiography (MRA) can be performed with high temporal resolution, and multiple low-dose slow infusions of Gd-based MR contrast agent can be performed without compromise of the vessel SNR and CNR.     

Whole-heart coronary magnetic resonance angiography at 3 Tesla in 5 minutes with slow infusion of Gd-BOPTA, a high-relaxivity clinical contrast agent.

T(1)-shortening contrast agents have been used to improve the depiction of coronary arteries with breath-hold magnetic resonance angiography (MRA). The spatial resolution and coverage are limited by the duration of the arterial phase of the contrast media passage. In this study we investigated the feasibility of acquiring free-breathing, whole-heart coronary MRA during slow infusion of the contrast media (0.3 ml/s) for prolonged blood signal enhancement time. Ultrashort TR (3 ms) and parallel data acquisition were used to allow the whole-heart MRA in approximately 5 min. A newly approved gadolinium (Gd)-based high T(1) relaxivity contrast agent, gadobenate dimeglumine ([Gd-BOPTA](2-)), was used and coronary MRA was performed on a whole-body 3 Tesla (T) system to improve the signal-to-noise ratio (SNR). Results from eight volunteers demonstrate that this coronary MRA method is capable of imaging the whole heart in 4.5 +/- 0.6 min. Major coronary arteries are well depicted with high SNR (42.4 +/- 12.5) and contrast-to-noise ratio (CNR; 27.1 +/- 7.6).     

Free-breathing, three-dimensional coronary artery magnetic resonance angiography: comparison of sequences

PURPOSE: To compare six free-breathing, three-dimensional, magnetization-prepared coronary magnetic resonance angiography (MRA) sequences. MATERIALS AND METHODS: Six bright-blood sequences were evaluated: Cartesian segmented gradient echo (C-SGE), radial SGE (R-SGE), spiral SGE (S-SGE), spiral gradient echo (S-GE), Cartesian steady-state free precession (C-SSFP), and radial SSFP (R-SSFP). The right coronary artery (RCA) was imaged in 10 healthy volunteers using all six sequences in randomized order. Images were evaluated by two observers with respect to signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), visible vessel length, vessel edge sharpness, and vessel diameter. RESULTS: C-SSFP depicted RCA over the longest distance with high vessel sharpness, good SNR, and excellent background suppression. S-GE provided best SNR and CNR in proximal segments, but more vessel blurring and poorer background suppression, resulting in poor visualization of distal segments. R-SSFP images showed good background suppression and best vessel sharpness, but only moderate SNR. C-SGE provided good SNR and reasonable CNR, but lowest vessel sharpness. S-SGE and R-SGE visualized the RCA over the smallest distance, mostly due to vessel blurring and low SNR, respectively. CONCLUSION: Overall, Cartesian SSFP provided the best image quality with excellent vessel sharpness, visualization of long vessel segments, and good SNR and CNR.     

Improved three-dimensional free-breathing coronary magnetic resonance angiography using gadocoletic acid (B-22956) for intravascular contrast enhancement

PURPOSE: To evaluate gadocoletic acid (B-22956), a gadolinium-based paramagnetic blood pool agent, for contrast-enhanced coronary magnetic resonance angiography (MRA) in a Phase I clinical trial, and to compare the findings with those obtained using a standard noncontrast T2 preparation sequence. MATERIALS AND METHODS: The left coronary system was imaged in 12 healthy volunteers before B-22956 application and 5 (N = 11) and 45 (N = 7) minutes after application of 0.075 mmol/kg of body weight (BW) of B-22956. Additionally, imaging of the right coronary system was performed 23 minutes after B-22956 application (N = 6). A three-dimensional gradient echo sequence with T2 preparation (precontrast) or inversion recovery (IR) pulse (postcontrast) with real-time navigator correction was used. Assessment of the left and right coronary systems was performed qualitatively (a 4-point visual score for image quality) and quantitatively in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, visible vessel length, maximal luminal diameter, and the number of visible side branches. RESULTS: Significant (P < 0.01) increases in SNR (+42%) and CNR (+86%) were noted five minutes after B-22956 application, compared to precontrast T2 preparation values. A significant increase in CNR (+40%, P < 0.05) was also noted 45 minutes postcontrast. Vessels (left anterior descending artery (LAD), left coronary circumflex (LCx), and right coronary artery (RCA)) were also significantly (P < 0.05) sharper on postcontrast images. Significant increases in vessel length were noted for the LAD (P < 0.05) and LCx and RCA (both P < 0.01), while significantly more side branches were noted for the LAD and RCA (both P < 0.05) when compared to precontrast T2 preparation values. CONCLUSION: The use of the intravascular contrast agent B-22956 substantially improves both objective and subjective parameters of image quality on high-resolution three-dimensional coronary MRA. The increase in SNR, CNR, and vessel sharpness minimizes current limitations of coronary artery visualization with high-resolution coronary MRA.     

3D magnetization-prepared true-FISP: a new technique for imaging coronary arteries.

The purpose of this work was to develop an ECG-triggered, segmented 3D true-FISP (fast imaging with steady-state precession) technique to improve the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of breath-hold coronary artery imaging. The major task was to optimize an appropriate magnetization preparation scheme to permit saturation of the epicardial fat signal. An alpha/2 preparation pulse was used to speed up the approach to steady-state following a frequency-selective fat-saturation pulse in each heartbeat. The application of dummy cycles was found to reduce the oscillation of the magnetization during data acquisition. The fat saturation and magnetization preparation scheme was validated with simulations and phantom studies. Volunteer studies demonstrated substantially increased SNR (55%) and CNR (178%) for coronary arteries compared to FLASH (fast low-angle shot) with the same imaging time. In conclusion, true-FISP is a promising technique for coronary artery imaging.     

Multislice breath-hold spiral magnetic resonance coronary angiography in patients with coronary artery disease: effect of intravascular contrast medium

PURPOSE: First, to apply a breath-hold multislice 2D spiral magnetic resonance (MR) approach in patients acquiring within 16 heartbeats (acquisition window, 116 msec) a 10-mm-thick stack of four slices (resolution, 1.3 x 1.3 mm(2)); and second, to evaluate the effect of an intravascular Fe-based contrast medium (CM) on a signal-to-noise ratio (SNR) and a contrast-to-noise ratio (CNR). MATERIALS AND METHODS: In each patient one or two coronary arteries were imaged prior to and following cumulative doses of 0.25, 0.5, and 0.75 mg of Fe/kg of body weight (bw) of an intravascular CM (CLARISCAN trade mark, Nycomed-Amersham, Princeton, NJ, USA) containing ultrasmall superparamagnetic iron oxide (USPIO) particles. RESULTS: On precontrast maximum intensity projection (MIP) images generated from the stack of slices, 10 and 11 stenoses of 12 stenoses confirmed by coronary angiography were detected by readers 1 and 2, respectively. SNR and CNR in the coronary arteries peaked at 0.50 mg of Fe/kg of bw, yielding a slight increase of 15.5% and 18.4%, respectively (P < 0.05 vs. precontrast), which did not improve detection of coronary artery stenoses. CONCLUSION: The presented multislice spiral approach allows display of coronary anatomy in MIP formats for convenient display of coronary stenoses. The pulse sequence did not benefit from an intravascular USPIO-based CM, since little improvement in SNR and CNR was achieved.     

Coronary arteries at 3.0 T: Contrast-enhanced magnetization-prepared three-dimensional breathhold MR angiography

PURPOSE: To evaluate the efficacy of contrast-enhanced coronary magnetic resonance angiography (MRA) at 3.0 T. MATERIALS AND METHODS: Nine healthy human volunteers were studied on a 3.0-T whole-body MR system. A three-dimensional, breathhold, magnetization-prepared, segmented, gradient-echo sequence was used, with injection of 20 mL gadopentetate dimeglumine for each three-dimensional slab. Imaging parameters were optimized based on computer simulations. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), depicted coronary artery length, lumen diameter, and imaging sharpness with contrast agent were evaluated. SNR and CNR were compared to the results from a previous 1.5-T study. RESULTS: A 53% increment in SNR and a 305% enhancement in CNR were measured with contrast. Vessel length and sharpness depicted were higher and the lumen diameter was lower (all P values < 0.05) in postcontrast images. Compared to previous results from 1.5-T, the SNR, CNR, and vessel sharpness were enhanced at 3.0 T with higher spatial resolution. CONCLUSION: Contrast-enhanced, three-dimensional, coronary MRA at 3.0 T is a promising technique for diagnosing coronary artery diseases. Patient studies are necessary to evaluate its clinical utility.     

Comparison of gradient-echo and steady-state free precession for coronary artery magnetic resonance angiography using a gadolinium-based intravascular contrast agent

OBJECTIVES: Intravascular contrast agents may offer longer imaging times and better vessel visualization over conventional extravascular agents for magnetic resonance coronary angiography. The purpose of this study was to evaluate the effect of intravascular contrast (B-22956/1) on coronary visualization. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared in inversion-recovery (IR)-prepared FLASH (fast low-angle shot) and IR-trueFISP (true fast imaging with steady-state precession) sequences before and after contrast. MATERIALS AND METHODS: Numeric simulations were performed to compare blood signals in IR-trueFISP and IR-FLASH sequences. Coronary imaging was performed in 15 swine. RESULTS: Postcontrast CNR was improved 23% with breathhold IR-FLASH and 55% with breathhold IR-trueFISP as compared with precontrast trueFISP. With free-breathing, long TR IR-FLASH provided 131% and 55.8% higher SNR and 132% and 58.7% increased CNR compared with IR-FLASH with shorter TR and IR-trueFISP, respectively. CONCLUSION: Intravascular contrast agents improve CNR and vessel visualization in coronary magnetic resonance angiography with IR-FLASH and IR-trueFISP.     

Local excitation black blood imaging at 3T: application to the carotid artery wall.

A novel approach for imaging large sections of the carotid artery wall at isotropic spatial resolution is presented. Local excitation by means of 2D excitation pulses was combined with a diffusion-prepared segmented steady-state black-blood gradient echo technique enabling the assessment of the carotid arterial wall over a range of up to 15 cm. The carotid arteries of five healthy volunteers were imaged with the proposed technique. Signal-to-noise ratio (SNR), wall-lumen contrast-to-noise ratio (CNR), and vessel dimensions were assessed and compared to conventional excitation techniques. In all experiments black-blood contrast could be realized over the covered carotid arteries with similar SNR and CNR as the conventional technique covering the region of the bulbus only. The proposed technique enables the time-efficient coverage of the carotid arteries without compromising wall-lumen CNR and geometrical accuracy. Furthermore, the proposed technique appears to be less sensitive to motion and swallowing artifacts due to the local character of the excitation.     

Catheter-directed contrast-enhanced coronary MR angiography in swine using magnetization-prepared True-FISP.

Contrast-enhanced (CE) coronary magnetic resonance angiography (MRA) following intraarterial (IA) injection of contrast agent was compared using two sequences in swine: magnetization-prepared fast imaging with steady-state precession (True-FISP), and magnetization-prepared fast low-angle shot (FLASH). Thick-slice projection images were acquired with submillimeter in-plane spatial resolution (0.9 x 0.8 mm(2)). The magnetization-preparation scheme provided a clear delineation of the major coronary arteries with excellent background suppression. The True-FISP acquisition resulted in an increase in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) by approximately a factor of 2 over FLASH (P < 0.05). Magnetization-prepared True-FISP is a promising technique for catheter-directed CE thick-slice projection coronary MRA.     

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.     

Shoulder MR arthrography: in vitro determination of optimal gadolinium dilution as a function of field strength

PURPOSE: To find the optimal contrast agent dilution to maximize signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in shoulder MR arthrography using MR systems operating at different magnetic field strengths. MATERIALS AND METHODS: Autoptic human glenohumeral ligaments were inserted in eight egg-shaped 20-mL phantoms filled with saline and gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd-DTPA-BMA) in different dilutions of 0.5, 1, 2, 2.5, 5, 12.5, 50 mmol/liter, to simulate the shoulder articular capsule. These phantoms were inserted inside two plastic 240-mL phantoms filled with water. MRI was performed on 0.2-, 0.5-, 1.0-, 1.5-, and 3.0-T MR systems using a three-dimensional gradient echo (GRE)-T1-weighted pulse sequence. SI, SNR, and CNR were determined. RESULTS: Peak SI and SNR were found at 5 mmol/liter, with the exception of the 0.2-T scanner, where the maximum was at 2 mmol/liter. Peak CNR was observed at 1 mmol/liter for the 3-T scanner, at 2 mmol/liter for the 0.2- and 0.5-T scanners, and at 5 mmol/liter for the remaining scanners. CONCLUSION: The optimal SI and SNR are provided by 5 mmol/liter contrast agent dilution. Peak CNR was found in a range between 1 and 5 mmol/liter dilutions, depending on the strength of the magnetic field.     

Coronary arteries: magnetization-prepared contrast-enhanced three-dimensional volume-targeted breath-hold MR angiography

A volume-targeted contrast agent-enhanced breath-hold coronary magnetic resonance angiographic technique was optimized and evaluated in 16 volunteers. Substantial increases in coronary signal-to-noise ratio, contrast-to-noise ratio, lengths of depiction, and vessel sharpness were observed on enhanced images. The imaging approach with two 20-mL injections of contrast agent covers the left and right coronary arteries in two breath holds and is a promising method for coronary imaging.     

Improvement of image quality of non-invasive coronary artery imaging with magnetic resonance by the use of the intravascular contrast agent Clariscan (NC100150 injection) in patients with coronary artery disease

PURPOSE: To assess the feasibility of Clariscan, an intravascular contrast agent, for free breathing, navigator assisted, high resolution, three-dimensional-magnetic resonance coronary angiography (MRCA) in patients, as extracellular contrast agents are unfavorable for the improvement of image quality. MATERIALS AND METHODS: MRCA was performed in 10 patients with known coronary artery disease (CAD) with (1-5 mg Fe/kg body weight) and without contrast agent. RESULTS: Compared to unenhanced images, Clariscan did not improve signal-to-noise (SNR) or contrast-to-noise ratios (CNR) compared to fat or myocardium in the proximal parts of the coronary arteries. However, when analyzing the peripheral parts (>4 cm from origin), CNR(fat) and CNR(myo) improved up to a factor of 1.81 and 5.85, respectively, at a dose of 3 mg Fe/kg body weight, while SNR did not reach statistical significance. The visible length of the coronary arteries was improved from 49 +/- 18 mm to 73 +/- 33 mm. The proximal diameter was reduced from 3.6 +/- 0.8mm to 3.2 +/- 0.8 mm, representing more closely the diameter of 3.1 +/- 0.7 mm measured by quantitative coronary angiography. Of 11 significant stenoses (>50%), eight were identified in the enhanced compared to six in the unenhanced images. CONCLUSION: The use of Clariscan at a dose of 2-3 mg Fe/kg body weight improves image quality of three-dimensional-MRCA, especially in the peripheral segments, and, thus, the diagnostic accuracy for the detection of CAD.     

Navigator-gated coronary magnetic resonance angiography using steady-state-free-precession: comparison to standard T2-prepared gradient-echo and spiral imaging

RATIONALE AND OBJECTIVES: Recent developments of magnetic resonance imaging enabled free-breathing coronary MRA (cMRA) using steady-state-free-precession (SSFP) for endogenous contrast. The purpose of this study was a systematic comparison of SSFP cMRA with standard T2-prepared gradient-echo and spiral cMRA. METHODS: Navigator-gated free-breathing T2-prepared SSFP-, T2-prepared gradient-echo- and T2-prepared spiral cMRA was performed in 18 healthy swine (45-68 kg body-weight). Image quality was investigated subjectively and signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel sharpness were compared. RESULTS: SSFP cMRA allowed for high quality cMRA during free breathing with substantial improvements in SNR, CNR and vessel sharpness when compared with standard T2-prepared gradient-echo imaging. Spiral imaging demonstrated the highest SNR while image quality score and vessel definition was best for SSFP imaging. CONCLUSION: Navigator-gated free-breathing T2-prepared SSFP cMRA is a promising new imaging approach for high signal and high contrast imaging of the coronary arteries with improved vessel border definition.     

Blood pool agent strongly improves 3D magnetic resonance coronary angiography using an inversion pre-pulse.

The ability of a blood pool contrast agent to enhance MR coronary angiography was defined. The proximal coronary vessels of pigs were imaged before and after administration of Gd-DTPA bound covalently to bovine serum albumin (0.2 mmol/ kg). The contrast agent resulted in a reduction of the blood T1 value to 33+/-5 msec, as determined in vivo with a Look-Locker technique. Both 2D and 3D imaging techniques were performed. An inversion pulse suppressed the signal of nonblood tissue postcontrast. After contrast agent administration, in the 3D data set the signal-to-noise ratio (SNR) of blood and contrast-to-noise ratio (CNR) of blood to myocardium were improved by factors of 2.0+/-0.2 and 15+/-8, respectively (P < 0.05). Postcontrast, the 3D acquisition was superior to the 2D technique in terms of spatial resolution, SNR of blood, and CNR of blood to myocardium. The high contrast of the 3D data set allowed for direct and rapid display of coronary arteries using a "closest vessel projection."     

Gadolinium-enhanced phase-contrast magnetic resonance portography.

PURPOSE: The purpose of this study was to investigate the effect and usefulness of gadolinium-chelated contrast medium in phase-contrast magnetic resonance (MR) portography. METHODS: Twenty-six patients (21 men, 5 women; aged 34 to 79 years, mean 62 years) underwent respiratory-triggered 3-dimensional phase-contrast portography before and after administration of gadolinium in a 1.5T MR unit. Coronal maximum intensity projection (MIP) images of the portal vein were reconstructed and compared to conventional arterial portograms regarding visualization. Signal-to-noise ratio (SNR) and portal vein-to-liver contrast-to-noise ratios (CNR) of main, right, right anterior, right posterior, left portal veins, and umbilical portion were measured on both non-enhanced and gadolinium-enhanced images and compared. RESULTS: Portal veins and branches were more clearly visualized on the gadolinium-enhanced than on the non-enhanced images. Compared to arterial portography, gadolinium-enhanced portography showed similar performances in visualization, except in the right posterior branch and left portal vein. No severe image degradation from respiration was experienced. SNR was significantly higher on the gadolinium-enhanced than on non-enhanced images except in the right anterior branch. CNR was significantly higher on the gadolinium-enhanced than on the non-enhanced images at all measured locations. CONCLUSIONS: Administration of gadolinium improves the SNR and CNR of phase-contrast portography and visualization of the portal vein. The phase-contrast technique with gadolinium enhancement can be used to evaluate the portal vein as a supplemental technique.     

Noncontrast 3D steady-state free-precession magnetic resonance angiography of the whole chest using nonselective radiofrequency excitation over a large field of view: comparison with single-phase 3D contrast-enhanced magnetic resonance angiography

OBJECTIVES: To evaluate the feasibility of three-dimensional (3D) steady-state free-precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation in the assessment of cardiac morphology, thoracic aorta, main pulmonary, and proximal coronary arteries. MATERIAL AND METHODS: Thirty consecutive patients (19 males; 11 females; age range, 20-74) with various cardiac and thoracic vascular diseases underwent free-breathing respiratory navigator-gated electrocardiogram-triggered noncontrast SSFP MRA and conventional high-resolution 3D contrast-enhanced MRA (CE-MRA) of the thorax at 1.5 T. Two readers evaluated both datasets for findings, vascular delineation and sharpness (from 0, not visualized to 3, excellent definition), artifacts, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in 14 vascular segments including aorta, supra-aortic, pulmonary, and coronary arteries, and in cardiac chambers. Statistical analysis was performed using Wilcoxon test for vessel delineation, and [kappa] coefficient for interobserver variability. RESULTS: 3D SSFP and CE-MRA were successfully performed in all patients. Scan time for SSFP MRA ranged from 5 to 10 minutes (mean +/- standard deviation, 7 +/- 2 minutes). On SSFP MRA, readers 1 and 2 graded 233 (97.1%) and 234 (97.5%) coronary arterial segments and cardiac chambers, and 275 (91.7%) and 278 (92.7%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.86). On conventional CE-MRA, readers 1 and 2 graded 10 (4.2%) and 12 (5%) coronary arterial segments and cardiac chambers, and 272 (90.7%) and 270 (90%) noncoronary arterial segments with diagnostic definition (grades 2 and 3) (k = 0.89). Segmental visibility was higher for aortic root, pulmonary trunk, proximal coronary arteries, and heart chambers (P < 0.001), and lower for supra-aortic arteries (P < 0.001) on SSFP MRA for each reader. SNR and CNR values were higher for aortic root and aorta on SSFP MRA (P < 0.001 for both). No significant difference existed between SNR and CNR values for the other vascular segments and cardiac chambers on SSFP and CE-MRA (P > 0.05 for all). The 2 readers demonstrated vascular stenosis and dilatation/aneurysm in 7 and 35 segments on both datasets, respectively. CONCLUSION: Noncontrast 3D SSFP MRA with nonselective radiofrequency excitation provides high image quality and sufficient SNR and CNR for confident assessment of cardiac and thoracic vascular diseases including congenital heart diseases. Our results suggest that noncontrast SSFP MRA outperforms CE-MRA in visualization of cardiac chambers, proximal coronary arteries, pulmonary trunk, and aortic root.     

Comparison of image quality in contrast-enhanced coronary-artery visualization by electron beam tomography and retrospectively electrocardiogram-gated multislice spiral computed tomography

RATIONALE AND OBJECTIVES: To compare the image quality of electron beam tomography (EBT) and multislice spiral CT (MSCT) for coronary artery visualization. MATERIALS AND METHODS: Two groups of 30 patients without coronary stenoses were studied by MSCT (4 x 1 mm collimation) or EBT (3 mm slice thickness). Contrast-to-noise ratio (CNR), overall length of the visualized arteries and vessel length free of motion artifacts were measured. RESULTS: Length of visualized arteries was equal in MSCT and EBT. In EBT, longer segments were depicted free of motion artifacts (MSCT: 73%, EBT: 92% of visualized length, P< 0.001) and CNR was significantly higher than in MSCT (15.4 vs. 9.0; P< 0.001). In both modalities, vessel diameters correlated closely to quantitative coronary angiography. CONCLUSIONS: EBT and MSCT permit reliable coronary artery visualization and measurement of vessel diameters. For the used scan protocol, MSCT images had a lower CNR and were more frequently affected by motion.