3D Coronary Magnetic Resonance Angiography Research Articles

Non-Rigid Respiratory Motion Estimation of Whole-Heart Coronary MR Images Using Unsupervised Deep Learning.

Non-rigid motion-corrected reconstruction has been proposed to account for the complex motion of the heart in free-breathing 3D coronary magnetic resonance angiography (CMRA). This reconstruction framework requires efficient and accurate estimation of non-rigid motion fields from undersampled images at different respiratory positions (or bins). However, state-of-the-art registration methods can be time-consuming. This article presents a novel unsupervised deep learning-based strategy for fast estimation of inter-bin 3D non-rigid respiratory motion fields for motion-corrected free-breathing CMRA. The proposed 3D respiratory motion estimation network (RespME-net) is trained as a deep encoder-decoder network, taking pairs of 3D image patches extracted from CMRA volumes as input and outputting the motion field between image patches. Using image warping by the estimated motion field, a loss function that imposes image similarity and motion smoothness is adopted to enable training without ground truth motion field. RespME-net is trained patch-wise to circumvent the challenges of training a 3D network volume-wise which requires large amounts of GPU memory and 3D datasets. We perform 5-fold cross-validation with 45 CMRA datasets and demonstrate that RespME-net can predict 3D non-rigid motion fields with subpixel accuracy (0.44 ± 0.38 mm) within ~10 seconds, being ~20 times faster than a GPU-implemented state-of-the-art non-rigid registration method. Moreover, we perform non-rigid motion-compensated CMRA reconstruction for 9 additional patients. The proposed RespME-net has achieved similar motion-corrected CMRA image quality to the conventional registration method regarding coronary artery length and sharpness.

A multi-scale variational neural network for accelerating motion-compensated whole-heart 3D coronary MR angiography

PurposeTo enable fast reconstruction of undersampled motion-compensated whole-heart 3D coronary magnetic resonance angiography (CMRA) by learning a multi-scale variational neural network (MS-VNN) which allows the acquisition of high-quality 1.2 × 1.2 × 1.2 mm isotropic volumes in a short and predictable scan time. MethodsEighteen healthy subjects and one patient underwent free-breathing 3D CMRA acquisition with variable density spiral-like Cartesian sampling, combined with 2D image navigators for translational motion estimation/compensation. The proposed MS-VNN learns two sets of kernels and activation functions for the magnitude and phase images of the complex-valued data. For the magnitude, a multi-scale approach is applied to better capture the small calibre of the coronaries. Ten subjects were considered for training and validation. Prospectively undersampled motion-compensated data with 5-fold and 9-fold accelerations, from the remaining 9 subjects, were used to evaluate the framework. The proposed approach was compared to Wavelet-based compressed-sensing (CS), conventional VNN, and to an additional fully-sampled (FS) scan. ResultsThe average acquisition time (m:s) was 4:11 for 5-fold, 2:34 for 9-fold acceleration and 18:55 for fully-sampled. Reconstruction time with the proposed MS-VNN was ~14 s. The proposed MS-VNN achieves higher image quality than CS and VNN reconstructions, with quantitative right coronary artery sharpness (CS:43.0%, VNN:43.9%, MS-VNN:47.0%, FS:50.67%) and vessel length (CS:7.4 cm, VNN:7.7 cm, MS-VNN:8.8 cm, FS:9.1 cm) comparable to the FS scan. ConclusionThe proposed MS-VNN enables 5-fold and 9-fold undersampled CMRA acquisitions with comparable image quality that the corresponding fully-sampled scan. The proposed framework achieves extremely fast reconstruction time and does not require tuning of regularization parameters, offering easy integration into clinical workflow.

Five-minute whole-heart coronary MRA with sub-millimeter isotropic resolution, 100% respiratory scan efficiency, and 3D-PROST reconstruction.

PurposeTo enable whole‐heart 3D coronary magnetic resonance angiography (CMRA) with isotropic sub‐millimeter resolution in a clinically feasible scan time by combining respiratory motion correction with highly accelerated variable density sampling in concert with a novel 3D patch‐based undersampled reconstruction (3D‐PROST).MethodsAn undersampled variable density spiral‐like Cartesian trajectory was combined with 2D image‐based navigators to achieve 100% respiratory efficiency and predictable scan time. 3D‐PROST reconstruction integrates structural information from 3D patch neighborhoods through sparse representation, thereby exploiting the redundancy of the 3D anatomy of the coronary arteries in an efficient low‐rank formulation. The proposed framework was evaluated in a static resolution phantom and in 10 healthy subjects with isotropic resolutions of 1.2 mm3 and 0.9 mm3 and undersampling factors of ×5 and ×9. 3D‐PROST was compared against fully sampled (1.2 mm3 only), conventional parallel imaging, and compressed sensing reconstructions.ResultsPhantom and in vivo (1.2 mm3) reconstructions were in excellent agreement with the reference fully sampled image. In vivo average acquisition times (min:s) were 7:57 ± 1:18 (×5) and 4:35 ± 0:44 (×9) for 0.9 mm3 resolution. Sub‐millimeter 3D‐PROST resulted in excellent depiction of the left and right coronary arteries including small branch vessels, leading to further improvements in vessel sharpness and visible vessel length in comparison with conventional reconstruction techniques. Image quality rated by 2 experts demonstrated that 3D‐PROST provides good image quality and is robust even at high acceleration factors.ConclusionThe proposed approach enables free‐breathing whole‐heart 3D CMRA with isotropic sub‐millimeter resolution in <5 min and achieves improved coronary artery visualization in a short and predictable scan time.

Technical note: Accelerated nonrigid motion-compensated isotropic 3D coronary MR angiography.

PurposeTo develop an accelerated and nonrigid motion‐compensated technique for efficient isotropic 3D whole‐heart coronary magnetic resonance angiography (CMRA) with Cartesian acquisition.MethodsHighly efficient whole‐heart 3D CMRA was achieved by combining image reconstruction from undersampled data using compressed sensing (CS) with a nonrigid motion compensation framework. Undersampled acquisition was performed using a variable‐density Cartesian trajectory with radial order (VD‐CAPR). Motion correction was performed in two steps: beat‐to‐beat 2D translational correction with motion estimated from interleaved image navigators, and bin‐to‐bin 3D nonrigid correction with motion estimated from respiratory‐resolved images reconstructed from undersampled 3D CMRA data using CS. Nonrigid motion fields were incorporated into an undersampled motion‐compensated reconstruction, which combines CS with the general matrix description formalism. The proposed approach was tested on 10 healthy subjects and compared against a conventional twofold accelerated 5‐mm navigator‐gated and tracked acquisition.ResultsThe proposed method achieves isotropic 1.2‐mm Cartesian whole‐heart CMRA in 5 min ± 1 min (~8× acceleration). The proposed approach provides good‐quality images of the left and right coronary arteries, comparable to those of a twofold accelerated navigator‐gated and tracked acquisition, but scan time was up to about four times faster. For both coronaries, no significant differences (P > 0.05) in vessel sharpness and length were found between the proposed method and reference scan.ConclusionThe feasibility of a highly efficient motion‐compensated reconstruction framework for accelerated 3D CMRA has been demonstrated in healthy subjects. Further investigation is required to assess the clinical value of the method.

Multicenter review: role of cardiovascular magnetic resonance in diagnostic evaluation, pre-procedural planning and follow-up for patients with congenital heart disease.

The number of patients with congenital heart disease (CHD) is rapidly increasing in the adult population, mainly due to the improved long-term survival. Serial follow-up with cardiac magnetic resonance imaging (CMR) is very appealing due to its non-invasive nature. CMR exam is able to provide specific information about cardiac function, hemodynamics, anatomy and tissue characterization unlikely achievable by other diagnostic techniques. CMR in CHD plays a role both in early diagnosis and in post-operative follow-up. Black Blood T1 weighted sequences are used to acquire morphological information. Cine Steady State Free Precession sequences are mainly used to provide data about cardiac function and kinesis. Hemodynamic assessment is routinely performed using phase contrast sequences, which provide reliable information concerning vessel flow pattern, cardiac output and intracardiac shunts. Magnetic Resonance Angiography (MRA) and 3D coronary MRA of the whole thorax can provide detailed morphological information regarding great vessels and proximal coronary arteries. Presence of late gadolinium enhancement suggesting myocardial macroscopic fibrosis seems to play a prognostic and diagnostic role even in this field.

3D coronary MR angiography at 1.5 T: Volume‐targeted versus whole‐heart acquisition

To compare volume-targeted acquisition with whole-heart acquisition in 1.5-T free-breathing 3D coronary magnetic resonance angiography (MRA) with parallel imaging. The major coronary arteries were imaged in 36 subjects using the whole-heart and volume-targeted acquisitions with comparable imaging parameters. The quantitative and semiquantitative data derived from these two acquisition methods were analyzed statistically, with P < 0.05 considered significant. Both the right coronary artery (RCA) / left circumflex artery (LCX)- and the left main (LM) / left anterior descending (LAD)-targeted acquisitions had similar results in navigator efficiencies and apparent signal-to-noise ratio (SNR) in comparison with whole-heart acquisition. Apparent contrast-to-noise ratio (CNR) of the volume-targeted imaging was significantly higher than that of the whole-heart imaging. The imaging time required for a whole-heart scan was significantly longer than each of the RCA/LCX- and LM/LAD-targeted acquisitions. However, the sum of scanning times derived from volume-targeted imaging was significantly longer than that of whole-heart acquisition. Both RCA/LCX- and LM/LAD-targeted acquisition yield higher vessel sharpness and overall image quality in comparison with whole-heart acquisition. The lengths of the major coronary arteries were not significantly different for the whole-heart and volume-targeted approaches. The whole-heart method was obviously superior to the volume-targeted method in terms of visualization of the posterior descending artery. For current 1.5-T navigator coronary MRA, volume-targeted and whole-heart acquisitions have their own advantages and the choice of methods may vary in accordance with the different aims of clinical practice.

A study of in vitro and in vivo MR of free-breathing whole-heart 3D coronary angiography using parallel imaging

To evaluate parallel-imaging methods in free-breathing whole-heart 3D coronary magnetic resonance angiography and assess the navigator techniques and visualization rates of the major coronary arteries. We compared key parameters of the generalized autocalibrating partially parallel acquisition and modified sensitive encoding images in vitro phantom MRI; performed the MRA with GRAPPA parallel imaging in healthy volunteers; compared 1D- and 2D-prospective acquisition correction and analyzed the differences; and evaluated the visualization of major coronary arterial branches. GRAPPA images had higher signal-to-noise ratio and contrast-to-noise ratio and fewer aliasing artifacts. The coronary arteries were adequately visualized in 38 volunteers. 2D-PACE had a higher navigator efficiency, shorter scan time, and gave clearer reconstructed images in comparison with 1D-PACE. GRAPPA images were superior to mSENSE images. Whole-heart 3D coronary MRA along with parallel-imaging technique is a potential clinical method, and 2D-PACE is a better navigation technique than 1D-PACE.

Intraindividual Comparison of 3D Coronary MR Angiography and Coronary CT Angiography

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. 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. 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%. 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.

Performance of a new gadolinium-based intravascular contrast agent in free-breathing inversion-recovery 3D coronary MRA.

In three-dimensional (3D) coronary magnetic resonance angiography (MRA), the in-flow contrast between the coronary blood and the surrounding myocardium is attenuated as compared to thin-slab two-dimensional (2D) techniques. The application of a gadolinium (Gd)-based intravascular contrast agent may provide an additional source of signal and contrast by reducing T(1blood) and supporting the visualization of more distal or branching segments of the coronary arterial tree. In six healthy adults, the left coronary artery (LCA) system was imaged pre- and postcontrast with a 0.075-mmol/kg bodyweight dose of the intravascular contrast agent B-22956. For imaging, an optimized free-breathing, navigator-gated and -corrected 3D inversion recovery (IR) sequence was used. For comparison, state-of-the-art baseline 3D coronary MRA with T(2) preparation for non-exogenous contrast enhancement was acquired. The combination of IR 3D coronary MRA, sophisticated navigator technology, and B-22956 allowed for an extensive visualization of the LCA system. Postcontrast, a significant increase in both the signal-to-noise ratio (SNR; 46%, P < 0.05) and contrast-to-noise ratio (CNR; 160%, P < 0.01) was observed, while vessel sharpness of the left anterior descending (LAD) artery and the left coronary circumflex (LCX) were improved by 20% (P < 0.05) and 18% (P < 0.05), respectively.

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

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). 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. 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). Real-time adaptive motion correction objectively and subjectively improves image quality in 3D navigator-gated free-breathing double-oblique submillimeter right coronary MRA.

"Soap-Bubble" visualization and quantitative analysis of 3D coronary magnetic resonance angiograms.

In order to compare coronary magnetic resonance angiography (MRA) data obtained with different scanning methodologies, adequate visualization and presentation of the coronary MRA data need to be ensured. Furthermore, an objective quantitative comparison between images acquired with different scanning methods is desirable. To address this need, a software tool ("Soap-Bubble") that facilitates visualization and quantitative comparison of 3D volume targeted coronary MRA data was developed. In the present implementation, the user interactively specifies a curved subvolume (enclosed in the 3D coronary MRA data set) that closely encompasses the coronary arterial segments. With a 3D Delaunay triangulation and a parallel projection, this enables the simultaneous display of multiple coronary segments in one 2D representation. For objective quantitative analysis, frequently explored quantitative parameters such as signal-to-noise ratio (SNR); contrast-to-noise ratio (CNR); and vessel length, sharpness, and diameter can be assessed. The present tool supports visualization and objective, quantitative comparisons of coronary MRA data obtained with different scanning methods. The first results obtained in healthy adults and in patients with coronary artery disease are presented.

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.

The impact of navigator timing parameters and navigator spatial resolution on 3D coronary magnetic resonance angiography.

The impact of navigator spatial resolution and navigator evaluation time on image quality in free-breathing navigator-gated 3D coronary magnetic resonance angiography (MRA), including real-time motion correction, was investigated in a moving phantom. Objective image quality parameters signal-to-noise ratio (SNR) and vessel sharpness were compared. It was found that for improved mage quality a short navigator evaluation time is of crucial importance. Navigator spatial resolution showed minimal influence on image quality.

Retrospective adaptive motion correction for navigator-gated 3D coronary MR angiography.

Retrospective adaptive motion correction (AMC) was developed for reducing effects of residual respiration in real-time navigator-gated three-dimensional (3D) coronary magnetic resonance (MR) angiography. In both motion phantom and in vivo experiments, AMC improved image sharpness of coronary arteries. This navigator-based technique combining adaptive correction and real-time gating is potentially an efficient and effective motion reduction method for 3D coronary MR angiography.

A fast 3D approach for coronary MRA.

Two-dimensional (2D)-breath-hold coronary magnetic resonance angiography (MRA) has been shown to be a fast and reliable method to depict the proximal coronary arteries. Recent developments, however, allow for free-breathing navigator gated and navigator corrected three-dimensional (3D) coronary MRA. These 3D approaches have potential for improved signal-to-noise ratio (SNR) and allow for the acquisition of adjacent thin slices without the misregistration problems known from 2D approaches. Still, a major impediment of a 3D acquisition is the increased scan time. The purpose of this study was the implementation of a free-breathing navigator gated and corrected ultra-fast 3D coronary MRA technique, which allows for scan times of less than 5 minutes. Twelve healthy adult subjects were examined in the supine position using a navigator gated and corrected ECG triggered ultra-fast 3D interleaved gradient echo planar imaging sequence (TFE-EPI). A 3D slab, consisting of 20 slices with a reconstructed slice thickness of 1.5 mm, was acquired with free-breathing. The diastolic TFE-EPI acquisition block was preceded by a T2prep pre-pulse, a diaphragmatic navigator pulse, and a fat suppression pre-pulse. With a TR of 19 ms and an effective TE of 5.4 ms, the duration of the data acquisition window duration was 38 ms. The in-plane spatial resolution was 1.0-1.3 mm*1.5-1.9 mm. In all cases, the entire left main (LM) and extensive portions of the left anterior descending (LAD) and right coronary artery (RCA) could be visualized with an average scan time for the entire 3D-volume data set of 2:57 +/- 0:51 minutes. Average contiguous vessel length visualized was 53 +/- 11 mm (range: 42 to 75 mm) for the LAD and 84 +/- 14 mm (range: 62 to 112 mm) for the RCA. Contrast-to-noise between coronary blood and myocardium was 5.0 +/- 2.3 for the LM/LAD and 8.0 +/- 2.9 for the RCA, resulting in an excellent suppression of myocardium. We present a new approach for free-breathing 3D coronary MRA, which allows for scan times superior to corresponding 2D coronary MRA approaches, and which takes advantage of the enhanced SNR of 3D acquisitions and the post-processing benefits of thin adjacent slices. The robust image quality and the short average scanning time suggest that this approach may be useful for screening the major coronary arteries or identification of anomalous coronary arteries. J. Magn. Reson. Imaging 1999;10:821-825.

Coronary MR angiography-a clinical experience in Japan.

Magnetic resonance angiography (MRA) has been expected to provide a useful noninvasive means of assessing coronary artery disease as this disease continues to increase due to westernization of life style. Several Japanese investigators have assessed the diagnostic value of two-dimensional (2D) and 3D coronary MRA in clinical patients evaluated for ischemic heart disease. Almost all reports indicate a high correlation between findings on 2D MRA and findings on conventional coronary angiography (CAG) in patients with severe stenosis of proximal arteries. However, in our study involving 153 patients with ischemic heart disease, 2D MRA tended to underestimate lesions in patients with moderate stenotic lesions. Furthermore, this method could not be applied successfully in approximately 15% of our patients due to difficulty with breath-holding. These findings indicate some of the limitations associated with breath-holding in the 2D method. Recently, several reports have described high diagnostic accuracy using respiratory-gated 3D MRA with navigator echo. Effective use of a suitable contrast agent with better spatial and time resolution and better image reconstruction methods will enable 3D MRA to serve a useful role, even in screening for coronary artery disease. J. Magn. Reson. Imaging 1999;10:709-712.

Three-dimensional coronary magnetic resonance angiography with injection of extracellular contrast medium.

To evaluate serial changes of the signal intensity and the contrast-to-noise ratios of the coronary arteries on three-dimensional (3D) coronary magnetic resonance angiography (MRA) after an injection of extracellular contrast medium, and to demonstrate the feasibility of this method for the diagnosis of coronary artery abnormalities. Five healthy volunteers and two patients with Kawasaki disease and an anomalous coronary artery were studied. Coronary MRAs of the left anterior descending artery and the right coronary artery were obtained using a fat-suppressed 3D MRA sequence before and 0 to 5, 10 to 15, 20 to 25, and 30 to 35 minutes after administration of Gd-DTPA-BMA. Administration of the contrast agent provided a significant increase in the signal intensity and contrast-to-noise ratio. Aneurysm of the left anterior descending artery in Kawasaki disease and the proximal course of the anomalous right coronary artery, which were not well depicted on precontrast 3D MRA, were clearly demonstrated after contrast injection. The current study demonstrated that the use of an extracellular gadolinium contrast agent can significantly improve the clinical usefulness of 3D coronary MRA.

Double-oblique free-breathing high resolution three-dimensional coronary magnetic resonance angiography

OBJECTIVESThe goal of the present study was to develop a strategy for three-dimensional (3D) volume acquisition along the major axes of the coronary arteries.BACKGROUNDFor high-resolution 3D free-breathing coronary magnetic resonance angiography (MRA), coverage of the coronary artery tree may be limited due to excessive measurement times associated with large volume acquisitions. Planning the 3D volume along the major axis of the coronary vessels may help to overcome such limitations.METHODSFifteen healthy adult volunteers and seven patients with X-ray angiographically confirmed coronary artery disease underwent free-breathing navigator-gated and corrected 3D coronary MRA. For an accurate volume targeting of the high resolution scans, a three-point planscan software tool was applied.RESULTSThe average length of contiguously visualized left main and left anterior descending coronary artery was 81.8 ± 13.9 mm in the healthy volunteers and 76.2 ± 16.5 mm in the patients (p = NS). For the right coronary artery, a total length of 111.7 ± 27.7 mm was found in the healthy volunteers and 79.3 ± 4.6 mm in the patients (p = NS). Comparing coronary MRA and X-ray angiography, a good agreement of anatomy and pathology was found in the patients.CONCLUSIONSDouble-oblique submillimeter free-breathing coronary MRA allows depiction of extensive parts of the native coronary arteries. The results obtained in patients suggest that the method has the potential to be applied in broader prospective multicenter studies where coronary MRA is compared with X-ray angiography.

Breathhold three-dimensional coronary magnetic resonance angiography using real-time navigator technology.

The acquisition duration of most three-dimensional (3D) coronary magnetic resonance angiography (MRA) techniques is considerably prolonged, thereby precluding breathholding as a mechanism to suppress respiratory motion artifacts. Splitting the acquired 3D volume into multiple subvolumes or slabs serves to shorten individual breathhold duration. Still, problems associated with misregistration due to inconsistent depths of expiration and diaphragmatic drift during sustained respiration remain to be resolved. We propose the combination of an ultrafast 3D coronary MRA imaging sequence with prospective real-time navigator technology, which allows correction of the measured volume position. 3D volume splitting using prospective real-time navigator technology, was successfully applied for 3D coronary MRA in five healthy individuals. An ultrafast 3D interleaved hybrid gradient-echoplanar imaging sequence, including T2Prep for contrast enhancement, was used with the navigator localized at the basal anterior wall of the left ventricle. A 9-cm-thick volume, with in-plane spatial resolution of 1.1 x 2.2 mm, was acquired during five breathholds of 15-sec duration each. Consistently, no evidence of misregistration was observed in the images. Extensive contiguous segments of the left anterior descending coronary artery (48 +/- 18 mm) and the right coronary artery (75 +/- 5 mm) could be visualized. This technique has the potential for screening for anomalous coronary arteries, making it well suited as part of a larger clinical MR examination. In addition, this technique may also be applied as a scout scan, which allows an accurate definition of imaging planes for subsequent high-resolution coronary MRA.

Improved Coronary Artery Definition With T2-Weighted, Free-Breathing, Three-Dimensional Coronary MRA

Three-dimensional (3D) navigator-gated and prospectively corrected free-breathing coronary magnetic resonance angiography (MRA) allows for submillimeter image resolution but suffers from poor contrast between coronary blood and myocardium. Data collected over >100 ms/heart beat are also susceptible to bulk cardiac and respiratory motion. To address these problems, we examined the effect of a T2 preparation prepulse (T2prep) for myocardial suppression and a shortened acquisition window on coronary definition. Eight healthy adult subjects and 5 patients with confirmed coronary artery disease (CAD) underwent free-breathing 3D MRA with and without T2prep and with 120- and 60-ms data-acquisition windows. The T2prep resulted in a 123% (P<0. 001) increase in contrast-to-noise ratio (CNR). Coronary edge definition was improved by 33% (P<0.001). Acquisition window shortening from 120 to 60 ms resulted in better vessel definition (11%; P<0.001). Among patients with CAD, there was a good correspondence with disease. Free-breathing, T2prep, 3D coronary MRA with a shorter acquisition window resulted in improved CNR and better coronary artery definition, allowing the assessment of coronary disease. This approach offers the potential for free-breathing, noninvasive assessment of the major coronary arteries.