Free-breathing 2D radial cine MRI with respiratory auto-calibrated motion correction (RAMCO).

PURPOSE: To develop a free-breathing (FB) 2D radial balanced steady-state free precession cine cardiac MRI method with 100% respiratory gating efficiency using respiratory auto-calibrated motion correction (RAMCO) based on a motion-sensing camera. METHODS: The signal from a respiratory motion-sensing camera was recorded during a FB retrospectively electrocardiogram triggered 2D radial balanced steady-state free precession acquisition using pseudo-tiny-golden-angle ordering. With RAMCO, for each acquisition the respiratory signal was retrospectively auto-calibrated by applying different linear translations, using the resulting in-plane image sharpness as a criterium. The auto-calibration determines the optimal magnitude of the linear translations for each of the in-plane directions to minimize motion blurring caused by bulk respiratory motion. Additionally, motion-weighted density compensation was applied during radial gridding to minimize through-plane and non-bulk motion blurring. Left ventricular functional parameters and sharpness scores of FB radial cine were compared with and without RAMCO, and additionally with conventional breath-hold Cartesian cine on 9 volunteers. RESULTS: FB radial cine with RAMCO had similar sharpness scores as conventional breath-hold Cartesian cine and the left ventricular functional parameters agreed. For FB radial cine, RAMCO reduced respiratory motion artifacts with a statistically significant difference in sharpness scores (P < 0.05) compared to reconstructions without motion correction. CONCLUSION: 2D radial cine imaging with RAMCO allows evaluation of left ventricular functional parameters in FB with 100% respiratory efficiency. It eliminates the need for breath-holds, which is especially valuable for patients with no or impaired breath-holding capacity. Validation of the proposed method on patients is warranted.

Echo planar imaging-induced errors in intracardiac 4D flow MRI quantification.

PURPOSE: To assess errors associated with EPI-accelerated intracardiac 4D flow MRI (4DEPI) with EPI factor 5, compared with non-EPI gradient echo (4DGRE). METHODS: Three 3T MRI experiments were performed comparing 4DEPI to 4DGRE: steady flow through straight tubes, pulsatile flow in a left-ventricle phantom, and intracardiac flow in 10 healthy volunteers. For each experiment, 4DEPI was repeated with readout and blip phase-encoding gradient in different orientations, parallel or perpendicular to the flow direction. In vitro flow rates were compared with timed volumetric collection. In the left-ventricle phantom and in vivo, voxel-based speed and spatio-temporal median speed were compared between sequences, as well as mitral and aortic transvalvular net forward volume. RESULTS: In steady-flow phantoms, the flow rate error was largest (12%) for high velocity (>2 m/s) with 4DEPI readout gradient parallel to the flow. Voxel-based speed and median speed in the left-ventricle phantom were ≤5.5% different between sequences. In vivo, mean net forward volume inconsistency was largest (6.4 ± 8.5%) for 4DEPI with nonblip phase-encoding gradient parallel to the main flow. The difference in median speed for 4DEPI versus 4DGRE was largest (9%) when the 4DEPI readout gradient was parallel to the flow. CONCLUSIONS: Velocity and flow rate are inaccurate for 4DEPI with EPI factor 5 when flow is parallel to the readout or blip phase-encoding gradient. However, mean differences in flow rate, voxel-based speed, and spatio-temporal median speed were acceptable (≤10%) when comparing 4DEPI to 4DGRE for intracardiac flow in healthy volunteers.

Clinical Validation of a 3-Dimensional Ultrafast Cardiac Magnetic Resonance Protocol Including Single Breath-Hold 3-Dimensional Sequences.

OBJECTIVES: This study sought to clinically validate a novel 3-dimensional (3D) ultrafast cardiac magnetic resonance (CMR) protocol including cine (anatomy and function) and late gadolinium enhancement (LGE), each in a single breath-hold. BACKGROUND: CMR is the reference tool for cardiac imaging but is time-consuming. METHODS: A protocol comprising isotropic 3D cine (Enhanced sensitivity encoding [SENSE] by Static Outer volume Subtraction [ESSOS]) and isotropic 3D LGE sequences was compared with a standard cine+LGE protocol in a prospective study of 107 patients (age 58 ± 11 years; 24% female). Left ventricular (LV) mass, volumes, and LV and right ventricular (RV) ejection fraction (LVEF, RVEF) were assessed by 3D ESSOS and 2D cine CMR. LGE (% LV) was assessed using 3D and 2D sequences. RESULTS: Three-dimensional and LGE acquisitions lasted 24 and 22 s, respectively. Three-dimensional and LGE images were of good quality and allowed quantification in all cases. Mean LVEF by 3D and 2D CMR were 51 ± 12% and 52 ± 12%, respectively, with excellent intermethod agreement (intraclass correlation coefficient [ICC]: 0.96; 95% confidence interval [CI]: 0.94 to 0.97) and insignificant bias. Mean RVEF 3D and 2D CMR were 60.4 ± 5.4% and 59.7 ± 5.2%, respectively, with acceptable intermethod agreement (ICC: 0.73; 95% CI: 0.63 to 0.81) and insignificant bias. Both 2D and 3D LGE showed excellent agreement, and intraobserver and interobserver agreement were excellent for 3D LGE. CONCLUSIONS: ESSOS single breath-hold 3D CMR allows accurate assessment of heart anatomy and function. Combining ESSOS with 3D LGE allows complete cardiac examination in <1 min of acquisition time. This protocol expands the indication for CMR, reduces costs, and increases patient comfort.

Variable anisotropic FOV for 3D radial imaging with spiral phyllotaxis (VASP).

PURPOSE: To develop a new 3D radial trajectory based on the natural spiral phyllotaxis (SP), with variable anisotropic FOV. THEORY & METHODS: A 3D radial trajectory based on the SP with favorable interleaving properties for cardiac imaging has been proposed by Piccini et al (Magn Reson Med. 2011;66:1049-1056), which supports a FOV with a fixed anisotropy. However, a fixed anisotropy can be inefficient when sampling objects with different anisotropic dimensions. We extend Larson's 3D radial method to provide variable anisotropic FOV for spiral phyllotaxis (VASP). Simulations were performed to measure distance between successive projections, analyze point spread functions, and compare aliasing artifacts for both VASP and conventional SP. VASP was fully implemented on a whole-body clinical MR scanner. Phantom and in vivo cardiac images were acquired at 1.5 tesla. RESULTS: Simulations, phantom, and in vivo experiments confirmed that VASP can achieve variable anisotropic FOV while maintaining the favorable interleaving properties of SP. For an anisotropic FOV with 100:100:35 ratio, VASP required ~65% fewer radial projections than the conventional SP to satisfy Nyquist criteria. Alternatively, when the same number of radial projections were used as in conventional SP, VASP produced fewer aliasing artifacts for anisotropic objects within the excited imaging volumes. CONCLUSION: We have developed a new method (VASP), which enables variable anisotropic FOV for 3D radial trajectory with SP. For anisotropic objects within the excited imaging volumes, VASP can reduce scan times and/or reduce aliasing artifacts.

Feasibility and Robustness of 3T Magnetic Resonance Angiography Using Modified Dixon Fat Suppression in Patients With Known or Suspected Peripheral Artery Disease.

Objective: Contrast-enhanced magnetic resonance angiography (CE-MRA) is a well-established non-invasive imaging technique for the assessment of peripheral artery disease (PAD). A subtractionless method using modified Dixon (mDixon) fat suppression showed superior image quality at 1.5T over the common subtraction method, using a three-positions stepping table approach with a single dose of contrast agent. The aim of this study was to investigate the feasibility of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD and to compare the performance in terms of vessel-to-background contrast (VBC), signal-to-noise ratio (SNR), and subjective image quality to conventional subtraction MRA. Methods: Ten patients [mean age 69 years ± 12 standard deviation (SD)] with known or suspected PAD were examined on a clinical 3T scanner (Ingenia, Philips Healthcare, Best, Netherlands) at three table positions using subtractionless and subtraction first-pass peripheral MRA. Two readers rated image quality on a four- point scale. Interobserver agreement was expressed in quadratic weighted κ values. VBC was assessed with a semi-automated process and SNR was compared in a healthy volunteer. Results: Subjective image quality was significantly better with the subtractionless method overall (mean image quality for mDixon imaging: 2.88 ± 0.32 SD vs. for subtraction imaging: 2.57 ± 0.48 SD; P < 0.001) and per table position (abdominal position: 2.88 ± 0.32 vs. 2.57 ± 0.48 SD; P < 0.001); upper leg position: (2.97 ± 0.15 SD vs. 2.68 ± 0.37 SD; P < 0.001; lower leg position: 2.60 ± 0.50 SD vs. 2.13 ± 0.60 SD; P < 0.001). Vessel-to-background contrast increased by 22% with the subtractionless method overall (mean VBC for mDixon imaging: 23.16 ± 8.4 SD vs. for subtraction imaging: 19.00 ± 8.1 SD; factor 1.22, P < 0.001). SNR was 82% higher with the subtractionless method (overall SNR gain 1.82; P < 0.001). Conclusion: This study demonstrated the feasibility and robustness of subtractionless first-pass peripheral MRA at 3T in patients with known or suspected PAD using a three- positions stepping table approach with a single dose of contrast agent. It showed increased image quality compared to the conventional subtraction method and superior performance in terms of SNR and vessel-to-background contrast.

Free-breathing non-contrast-enhanced flow-independent MR angiography using magnetization-prepared 3D non-balanced dual-echo Dixon method: A feasibility study at 3 Tesla.

In this work we aimed to investigate the feasibility of using a new pulse sequence called Relaxation-Enhanced Angiography without Contrast and Triggering (REACT) for free-breathing non-contrast-enhanced MR angiography (NCE-MRA) for multiple anatomies on 3T. Two magnetization-preparation pulses were incorporated with a three-dimensional dual-echo Dixon sequence. A T2-prep pulse, followed by a non-selective inversion pulse with a short inversion time, together suppressed tissue with short T1 and T2, while enhancing the signal of native blood with long T1 and T2. A two-point non-balanced gradient-echo Dixon method, based on dual-echo acquisition with semi-flexible echo times for water-fat separation, was used for improved fat suppression over a large field of view. General image quality, vasculature visibility, and clinical indications of the proposed method were investigated in healthy subjects and patients in both torso and extremities based on visual inspection. Preliminary results from REACT obtained in free-breathing with no cardiac triggering showed uniform suppression of background tissue over the field of view and robust blood-to-tissue contrast over multiple anatomies. Future clinical studies are warranted for further investigation of its diagnostic performance and limitations.

Fatty metaplasia quantification and impact on regional myocardial function as assessed by advanced cardiac MR imaging.

OBJECTIVE: This study aimed to investigate the advantages of recently developed cardiac imaging techniques of fat-water separation and feature tracking to characterize better individuals with chronic myocardial infarction (MI). MATERIALS AND METHODS: Twenty patients who had a previous MI underwent CMR imaging. The study protocol included routine cine and late gadolinium enhancement (LGE) technique. In addition, mDixon LGE imaging was performed in every patient. Left ventricular (LV) circumferential (EccLV) and radial (ErrLV) strain were calculated using dedicated software (CMR42, Circle, Calgary, Canada). The extent of global scar was measured in LGE and fat-water separated images to compare conventional and recent CMR imaging techniques. RESULTS: The infarct size derived from conventional LGE and fat-water separated images was similar. However, detection of lipomatous metaplasia was only possible with mDixon imaging. Subjects with fat deposition demonstrated a significantly smaller percentage of fibrosis than those without fat (10.68 ± 5.07% vs. 13.83 ± 6.30%; p = 0.005). There was no significant difference in EccLV or ErrLV between myocardial segments containing fibrosis only and fibrosis with fat. However, EccLV and ErrLV values were significantly higher in myocardial segments adjacent to fibrosis with fat deposition than in those adjacent to LGE only. CONCLUSIONS: Advanced CMR imaging ensures more detailed tissue characterization in patients with chronic MI without a relevant increase in imaging and post-processing time. Fatty metaplasia may influence regional myocardial deformation especially in the myocardial segments adjacent to scar tissue. A simplified and shortened myocardial viability CMR protocol might be useful to better characterize and stratify patients with chronic MI.

Selection of magnetization catalyzation and readout methods for modified Look-Locker inversion recovery: a T1 mapping primer.

BACKGROUND: The purpose of this work was to evaluate different magnetization preparation and readout sequences for modified Look-Locker inversion recovery (MOLLI) toward improved T1 mapping in the heart. Elements investigated include: catalyzation sequences to prepare the magnetization before readout, alternate k-space trajectories, a spoiled gradient recalled echo readout, and a 5b(3b)3b MOLLI sampling scheme ('b' denoting beats). METHODS: Conventional 3b(3b)3b(3b)5b MOLLI with a linear k-space trajectory was compared to four variants in simulations, in vitro and in vivo (at 3T). Variants were centric conventional MOLLI, centric-paired conventional MOLLI, linear 5b(3b)3b MOLLI and spoiled gradient recalled echo MOLLI. Each of these was applied with three magnetization catalyzation methods, and T1 measurement accuracy and precision were evaluated in simulations via a Monte Carlo algorithm, in a set of calibrated phantoms, and in ten healthy volunteers. Contrast-to-noise, heart rate dependence and B1+ dependence were also evaluated. RESULTS: A linear k-space trajectory was superior in vitro to centric and centric-paired trajectories. Of the catalyzation methods, preparation of transverse magnetization only-using a linearly increasing flip angle catalyzation-improved MOLLI T1 measurement accuracy, precision, and map quality versus methods that include catalyzation of the longitudinal magnetization. The 5b(3b)3b MOLLI scheme offered comparable native T1 measurement accuracy and precision to conventional MOLLI, despite its shortened acquisition. CONCLUSIONS: MOLLI T1 measurement accuracy, precision, and map quality depend on the method of catalyzation of magnetization prior to image acquisition, as well as on the readout method and MOLLI sampling scheme used.

High-dose dobutamine stress steady-state free precession (SSFP) cine MRI at 3T with patient adaptive local radiofrequency (RF) shimming using dual-source RF transmission.

PURPOSE: To prospectively assess the feasibility, image quality, and diagnostic accuracy of high-dose dobutamine stress magnetic resonance imaging (DSMR) using steady-state free precession (SSFP) cine imaging at 3T applying a dual-source radiofrequency (RF) excitation magnetic resonance imaging (MRI) system with parallel transmission and patient adaptive local RF shimming. MATERIALS AND METHODS: DSMR using SSFP cine imaging was performed in 44 patients at 3T scheduled for a clinically indicated coronary angiography. The effect of conventional versus dual-source RF transmission was assessed regarding homogeneity of the B1 field, contrast-to-noise ratios (CNRs) at rest, image quality, and diagnostic accuracy of DSMR using long and short axis. RESULTS: The mean percentage of the intended flip angle within the heart increased from 88 ± 9.1% with single-source to 103 ± 5.6% (P < 0.001) dual-source RF transmission. CNR increased for dual-source particularly at the apex (63.4 ± 24.2 vs. 36.5 ± 16.5, P < 0.001) but also at the base of the left ventricle (LV) (50.1 ± 14.8 vs. 39.3 ± 15.8, P < 0.001). Image quality of dual-source was higher both at rest (2.8 ± 0.5 vs. 2.6 ± 0.7, P < 0.001) and stress (2.5 ± 0.7 vs. 2.0 ± 1.0, P < 0.001). The number of segments with severe artifacts or nondiagnostic image quality at stress was lower with dual-source RF transmission (8% vs. 27%, P < 0.001). The diagnostic accuracy of DSMR in coronary territories using dual-source RF transmission was significantly higher (77% vs. 65%, P = 0.04). CONCLUSION: Patient adaptive local RF shimming using dual-source RF transmission provided significantly improved image quality and higher diagnostic accuracy of SSFP during DSMR at 3T compared to conventional RF transmission.

Robust myocardial T2 and T2 * mapping at 3T using image-based shimming.

PURPOSE: Intramyocardial hemorrhage and area at risk are both prognostic markers in acute myocardial infarction (AMI). Myocardial T2 and T2 * mapping have been used to detect such tissue changes at 1.5T but these techniques are challenging at 3.0T due to additional susceptibility variation. We studied T2 and T2 * myocardial mapping techniques at 3.0T on a system employing B1 shimming and compared two different methods of B0 shimming. MATERIALS AND METHODS: Fifteen volunteers and six AMI patients were scanned on a 3T system. Volume and image-based (IB) B0 shimming techniques were implemented. Single breath-hold, multiecho gradient, and spin echo sequences were employed from which T2 * and T2 maps were calculated. RESULTS: In volunteers, there was no significant difference in mean values obtained with volume or IB shimming for T2 mapping (39.1 ± 6.0 msec vs. 39.4 ± 6.1 msec; P > 0.05) or for T2 * mapping (24.2 ± 6.7 msec vs. 24.1 ± 5.2 msec; P > 0.05). There were no significant regional differences in mean T2 values between septal, anterior, and posterior segments with either shimming technique (all P > 0.05); but there were significant regional differences in mean T2 * values using volume shimming (27.8 ± 5.2 msec vs. 28.4 ± 5.8 msec vs. 15.9 ± 8.3 msec; P < 0.05)-but not with IB shimming (25.7 ± 5.4 msec vs. 25.3 ± 5.9 msec vs. 18.7 ± 4.6 msec; P > 0.05). CONCLUSION: At 3.0T, cardiac T2 mapping is robust. Although T2 * mapping is prone to more regional heterogeneity this can be reduced by using IB instead of conventional volume B0 shimming.

Three-dimensional balanced steady state free precession myocardial perfusion cardiovascular magnetic resonance at 3T using dual-source parallel RF transmission: initial experience.

BACKGROUND: The purpose of this study was to establish the feasibility of three-dimensional (3D) balanced steady-state-free-precession (bSSFP) myocardial perfusion cardiovascular magnetic resonance (CMR) at 3T using local RF shimming with dual-source RF transmission, and to compare it with spoiled gradient echo (TGRE) acquisition. METHODS: Dynamic contrast-enhanced 3D bSSFP perfusion imaging was performed on a 3T MRI scanner equipped with dual-source RF transmission technology. Images were reconstructed using k-space and time broad-use linear acquisition speed-up technique (k-t BLAST) and compartment based principle component analysis (k-t PCA). RESULTS: In phantoms and volunteers, local RF shimming with dual source RF transmission significantly improved B1 field homogeneity compared with single source transmission (P=0.01). 3D bSSFP showed improved signal-to-noise, contrast-to-noise and signal homogeneity compared with 3D TGRE (29.8 vs 26.9, P=0.045; 23.2 vs 21.6, P=0.049; 14.9% vs 12.4%, p=0.002, respectively). Image quality was similar between bSSFP and TGRE but there were more dark rim artefacts with bSSFP. k-t PCA reconstruction reduced artefacts for both sequences compared with k-t BLAST. In a subset of five patients, both methods correctly identified those with coronary artery disease. CONCLUSION: Three-dimensional bSSFP myocardial perfusion CMR using local RF shimming with dual source parallel RF transmission at 3T is feasible and improves signal characteristics compared with TGRE. Image artefact remains an important limitation of bSSFP imaging at 3T but can be reduced with k-t PCA.

Evaluation of a subject specific dual-transmit approach for improving B1 field homogeneity in cardiovascular magnetic resonance at 3T.

BACKGROUND: Radiofrequency (RF) shading artifacts degrade image quality while performing cardiovascular magnetic resonance (CMR) at higher field strengths. In this article, we sought to evaluate the effect of local RF (B1 field) shimming by using a dual-source-transmit RF system for cardiac cine imaging and to systematically evaluate the effect of subject body type on the B1 field with and without local RF shimming. METHODS: We obtained cardiac images from 37 subjects (including 11 patients) by using dual-transmit 3T CMR. B1 maps with and without subject-specific local RF shimming (exploiting the independent control of transmit amplitude and phase of the 2 RF transmitters) were obtained. Metrics quantifying B1 field homogeneity were calculated and compared with subject body habitus. RESULTS: Local RF shimming across the region encompassed by the heart increased the mean flip angle (µ) in that area (88.5 ± 15.2% vs. 81.2 ± 13.3%; P = 0.0014), reduced the B1 field variation by 42.2 ± 13%, and significantly improved the percentage of voxels closer to µ (39% and 82% more voxels were closer to ± 10% and ± 5% of µ, respectively) when compared with no RF shimming. B1 homogeneity was independent of subject body type (body surface area [BSA], body mass index [BMI] or anterior-posterior/right-left patient width ratio [AP/RL]). Subject specific RF (B1) shimming with a dual-transmit system improved local RF homogeneity across all body types. CONCLUSION: With or without RF shimming, cardiac B1 field homogeneity does not depend on body type, as characterized by BMI, BSA, and AP/RL. For all body types studied, cardiac B1 field homogeneity was significantly improved by performing local RF shimming with 2 independent RF-transmit channels. This finding indicates the need for subject-specific RF shimming.

Dual-source radiofrequency transmission with patient-adaptive local radiofrequency shimming for 3.0-T cardiac MR imaging: initial experience.

PURPOSE: To evaluate the effect of dual-source parallel radiofrequency (RF) transmission with patient-adaptive local RF shimming on image quality, image contrast, and diagnostic confidence at routine clinical cardiac magnetic resonance (MR) imaging with use of a 3.0-T dual-channel transmit whole-body MR system. MATERIALS AND METHODS: Written informed consent was obtained from all patients, and the study protocol was approved by the local institutional review board. Cardiac MR imaging was performed in 28 patients by using a 3.0-T MR unit equipped with a dual-source RF transmission system. The effect of conventional versus dual-source RF transmission on steady-state free precession (SSFP) cine sequences and turbo spin-echo (TSE) black-blood (BB) sequences was evaluated. The homogeneity of the B1 field and contrast-to-noise ratios (CNRs) were measured and tested for statistical significance with the paired t test. Images were analyzed qualitatively for homogeneity, the presence of off-resonance artifacts, and diagnostic confidence independently by two readers. Statistical significance was assessed with the Wilcoxon signed rank test. Inter- and intraobserver agreement was assessed with κ statistics. RESULTS: Quantitative image analysis revealed that B1 homogeneity and CNR were significantly improved for images acquired with dual-source RF transmission compared with conventional RF transmission (P = .005). The quality of SSFP and TSE BB images of the left and the right ventricles showed a significant improvement with respect to image homogeneity and diagnostic confidence as evaluated by the readers (P = .0001, κ > 0.74). As a side effect, off-resonance artifacts were significantly reduced on SSFP images (P = .0001, κ > 0.76). CONCLUSION: Dual-source parallel RF transmission significantly improves image homogeneity, image contrast, and diagnostic confidence compared with conventional RF transmission of cardiac SSFP and TSE BB sequences.

Fully automatic geometry planning for cardiac MR imaging and reproducibility of functional cardiac parameters.

PURPOSE: To establish operator-independent, fully automated planning of standard cardiac geometries and to determine the impact on interstudy reproducibility of cardiac functional parameters. MATERIALS AND METHODS: Cardiac MR imaging was done in 50 patients referred for left-ventricular function assessment. In all patients, first standard manual planning was performed followed by automatic planning (AUTO1) and repeat automatic planning (AUTO2) after repositioning the patient to investigate interstudy reproducibility. Cardiac functional parameters were assessed and cine scans were visually graded on a 4-point scale from nondiagnostic to excellent. RESULTS: Overall success rate of AUTO was 94% with good to excellent geometry planning in >94% of cine standard views. Comparing manual versus fully automated planning, a high agreement of cardiac functional parameters (Lin's concordance correlation coefficient, 0.91 to 0.99) with minimal percent bias (0.24 to 3.84%) was found. In addition, a high interstudy reproducibility of automatic planning was demonstrated (Lin's concordance correlation coefficient, 0.89 to 0.99; percent bias, 0.38 to 5.04%; precision, 3.46 to 9.09%). CONCLUSION: Fully automated planning of cardiac geometries could reliably be performed in patients showing a variety of cardiovascular pathologies. Standard cardiac geometries were precisely replicated and functional parameters were highly accurate.

Rapid assessment of regional and global left ventricular function using three-dimensional k-t BLAST imaging.

OBJECTIVE: To test if three-dimensional (3D) cine spatial frequency-temporal frequency Broad-use Linear Acquisition Speed-up Technique (k-t BLAST) is suitable for rapid evaluation of global and regional left ventricular (LV) functional parameters and to evaluate the influence of gadolinium administration. MATERIALS AND METHODS: Parameters describing global and regional LV function were evaluated in 50 subjects using a two-dimensional (2D) steady-state free precession (SSFP) and pre- and postcontrast 3D k-t BLAST techniques. Data analyses included contrast-to-noise ratio analyses, and statistical evaluations included Bland-Altman, Cohen's kappa and analysis of variance techniques. RESULTS: Bland-Altman analyses revealed that the ejection fraction computed using the 3D k-t BLAST sequences before (bias+/-2S.D., 2.2+/-8.8) and after contrast administration (bias+/-2S.D., 2.7+/-7.6 mol) was comparable to the 2D SSFP technique. Similar agreement was noted for other global LV parameters. The myocardium-to-blood contrast in the apical slices was better in the 3D k-t BLAST sequence after contrast administration than before. Cohen's kappa values demonstrated good agreement between the sequences for evaluating regional wall motion. CONCLUSIONS: 3D k-t BLAST can yield global and regional LV functional parameters comparable to those of the 2D SSFP technique in substantially shorter scan times. In 3D k-t BLAST images, myocardium-to-blood contrast in the apical slices is better after contrast administration.

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.

Improved visualization of coronary arteries using a new three-dimensional submillimeter MR coronary angiography sequence with balanced gradients.

OBJECTIVE: The goal of our study was to evaluate a new three-dimensional real-time navigator MR coronary angiography sequence to noninvasively visualize the coronary arteries. SUBJECTS AND METHODS: Fifteen healthy volunteers underwent MR coronary angiography with a new balanced turbo field-echo sequence in comparison with the standard turbo field-echo sequence. Signal-to-noise, blood-to-myocardium, blood-to-fat, and blood-to-pericardial fluid contrast ratios of the left and right coronary artery systems were measured. Image quality was graded, the length and diameter of the coronary arteries were measured, and the number of visible side branches was assessed. RESULTS: The balanced turbo field-echo images yielded a higher blood-to-myocardium and blood-to-pericardial fluid contrast ratio, a similar blood-to-fat contrast ratio, and a lower signal-to-noise ratio than the turbo field-echo images. On a 5-point grading scale (1, nondiagnostic or unreadable; 2, poor; 3, moderate; 4, good; 5, excellent), image quality was rated significantly better for the balanced turbo field-echo sequence than for the turbo field-echo sequence (left coronary artery, 4.0 +/- 0.6 vs 3.6 +/- 0.5 [p = 0.015]; right coronary artery, 4.4 +/- 0.4 vs 3.6 +/- 0.4 [p < 0.0001], respectively), resulting in a significantly longer segment of the three major coronary arteries visualized (left anterior descending coronary artery, 92 +/- 21 mm vs 79 +/- 24 mm; left circumflex coronary artery, 70 +/- 7 mm vs 60 +/- 18 mm; right coronary artery, 112 +/- 28 mm vs 95 +/- 27 mm) and a significantly higher number of side branches visualized (left anterior descending coronary artery, 2.9 +/- 1.3 vs 1.5 +/- 1.3; left circumflex coronary artery, 2.1 +/- 1.7 vs 1.0 +/- 1.2; right coronary artery, 3.7 +/- 1.7 vs 2.6 +/- 1.5). Mean imaging time per coronary artery was significantly shorter for the balanced turbo field-echo sequence (5.7 +/- 1.0 min) than for the turbo field-echo sequence (8.4 +/- 1.4 min) (p < 0.0001). CONCLUSION: Compared with standard turbo field-echo MR coronary angiography, optimized balanced turbo field-echo MR coronary angiography improves the visualization of the coronary arteries and their side branches within a significantly shorter imaging time.