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Purpose To develop a free-breathing whole-heart isotropic-resolution 3D late gadolinium enhancement (LGE) sequence with Dixon-encoding, which provides co-registered 3D grey-blood phase-sensitive inversion-recovery (PSIR) and complementary 3D fat volumes in a single scan of Methods A free-breathing 3D PSIR LGE sequence with dual-echo Dixon readout with a variable density Cartesian trajectory with acceleration factor of 3 is proposed. Image navigators are acquired to correct both inversion recovery (IR)-prepared and reference volumes for 2D translational respiratory motion, enabling motion compensated PSIR reconstruction with 100% respiratory scan efficiency. An intermediate PSIR reconstruction is performed between the in-phase echoes to estimate the signal polarity which is subsequently applied to the IR-prepared water volume to generate a water grey-blood PSIR image. The IR-prepared water volume is obtained using a water/fat separation algorithm from the corresponding dual-echo readout. The complementary fat-volume is obtained after water/fat separation of the reference volume. Ten patients (6 with myocardial scar) were scanned with the proposed water/fat grey-blood 3D PSIR LGE sequence at 1.5 T and compared to breath-held grey-blood 2D LGE sequence in terms of contrast ratio (CR), contrast-to-noise ratio (CNR), scar depiction, scar transmurality, scar mass and image quality. Results Comparable CRs (p = 0.98, 0.40 and 0.83) and CNRs (p = 0.29, 0.40 and 0.26) for blood-myocardium, scar-myocardium and scar-blood respectively were obtained with the proposed free-breathing 3D water/fat LGE and 2D clinical LGE scan. Excellent agreement for scar detection, scar transmurality, scar mass (bias = 0.29%) and image quality scores (from 1: non-diagnostic to 4: excellent) of 3.8 ± 0.42 and 3.6 ± 0.69 (p > 0.99) were obtained with the 2D and 3D PSIR LGE approaches with comparable total acquisition time (p = 0.29). Similar agreement in intra and inter-observer variability were obtained for the 2D and 3D acquisition respectively. Conclusion The proposed approach enabled the acquisition of free-breathing motion-compensated isotropic-resolution 3D grey-blood PSIR LGE and fat volumes. The proposed approach showed good agreement with conventional 2D LGE in terms of CR, scar depiction and scan time, while enabling free-breathing acquisition, whole-heart coverage, reformatting in arbitrary views and visualization of both water and fat information.

Background Respiratory motion compensation is usually required in free-breathing thoracic MR imaging applications to remove the motion induced blur and ghosting artifacts. Most respiratory motion compensation techniques are based on gating in which data is acquired only at one respiratory state (RS) and therefore suffer from extended yet unpredictable scan time. Other techniques compensate for motion by correcting the phase of motion corrupted k-space data so that data acquired in multiple respiratory states can be used in reconstruction for improved scan efficiency. However, these methods are often limited to correcting rigid-body motion and thus not suitable for thoracic imaging with large field-ofview. In this work, we propose a technical strategy of correcting 3D non-rigid motion and apply it to ferumoxytol enhanced free-breathing thoracic MRA.

Background Mapping the longitudinal relaxation time (T1) is a promising quantitative tool for the detection of myocardial pathologies either in mouse or human. T1 maps are usually obtained in 2D in order to reduce the total scan time. However, to diagnose myocardial infarction it might be useful to obtain the T1 maps in three dimensions (3D) which require a long acquisition time. In this project a new 3D T1 mapping method based on Look-Locker protocol using continuous radio frequency (RF) excitation and spiral gradient shape has been developed. This method allowed to obtain 3D maps with high spatial (200 x 200 x 300 μm) & temporal resolution (

Background Recently developed compressed sensing (CS) SSFP sequences significantly reduce data acquisition time thereby reducing patient breath-hold and scan time relative to standard techniques. The variability of ventricular functional (VF) analysis of CS data is not known so this study investigated the inter-observer variation of left ventricular (LV) mass and volume measurements compared to standard SSFP acquisitions.

Background Cardiac magnetic resonance imaging has been shown to be one of the best technologies for the evaluation of cardiovascular pathologies. However, its widespread adoption has been held back by the lack of software infrastructure and specific pulse sequences that can provide a feasibly quick, comprehensive cardiac examination. We have developed an intuitive software package that can perform a comprehensive CMR examination in 30 to 45 minutes.

Background Cardiac T1 and extracellular volume fraction (ECV), derived from preand post-contrast cardiac and blood T1 measurements, are emerging imaging biomarkers of diffuse cardiac fibrosis. The most frequently used cardiac T1 mapping pulse sequence is MOLLI [1]. However, MOLLI is known to be sensitive to rapid heart rate and irregular rhythm, because it is based on inversion-recovery (IR) of magnetization preparation. In response, we developed an arrhythmia-insensitive-rapid (AIR) cardiac T1 mapping pulse sequence based on B1insensitive saturation-recovery (SR) of magnetization preparation [2]. Our prior study [2] showed that AIR (scan time = 2-3 heart beats) is faster and yields more accurate cardiac T1 measurements than MOLLI (scan time = 17 heart beats). We sought to compare ECV measurements between SR-based AIR and IR-based MOLLI cardiac T1 mapping at 3T.

Background Myocardial late gadolinium enhancement (LGE) MRI has become a standard clinical exam for characterizing myocardial viability after infarction and for assessing many nonischemic myocardial diseaseses. Typically, a 3D slab covering the myocardium is scanned within a single breath-hold. However, 3D LGE with sufficient resolution and slice coverage requires a long scan time and is challenging in cardiac patients with limited breath-hold capability. Recently, compressed sensing (CS) [1] has demonstrated the ability to further accelerate MRI on top of parallel imaging (PI) and has demonstrated promising results for 3D LGE [2]. This work intended to evaluate the feasibility of a CS-PI method based on ESPIRiT [3-5] and optimize its data acquisition for improving the robustness of 3D LGE with high acceleration.

Background A 3D Dual Cardiac Phase (3D-DCP) scan was proposed to obtain systolic and diastolic images with equivalent quality and scan time compared to the 3D single cardiac phase acquisition (Uribe et al, Radiology 2008). In this work, we propose to accelerate the acquisition and reconstruction of the 3D-DCP approach by sharing information from the outer k-space of both cardiac phases using Radial Phase Encoding (RPE) trajectories (Boubertak, et al., MRM 2009) and gridding-CLEAR reconstruction

3T MRI is advantageous to CMR as it offers higher SNR and better T1 contrast. Its slow clinical adoption is partly due to the lack of robustness in SSFP cine imaging [1]. Banding artifact in SSFP caused by main field inhomogeneity is common at 3T. Wideband SSFP [2] or prescans (shimming, frequency scout, etc.) are needed to avoid/ reduce the artifact, increasing patient scan time. We propose here to use shorter TR for SSFP through slightly reduced spatial resolution to improve the sequence’s robustness and speed for cine imaging. Its ability for LV function assessment was evaluated against the standard SSFP acquisition protocol.

Background Fat-saturation and T1-weighting are fundamental for tissue differentiation, but combining these techniques is challenging. For instance, standard chemically selective saturation (CHESS) pulses provide insufficient fatsuppression with routine delayed enhancement imaging [1]. Fat-water separation using multi-echo Dixon techniques can robustly separate fat and water into individual images, but in the fat-suppressed (water only) image, fat may retain a significant amount of signal making identification of the fat-water border difficult. We previously described a new technique (Virtual Chemical Inversion, VCI, [1]) which has the advantage of providing T1-weighted images with and without fat suppression in a single acquisition without the need for additional data acquisition, RF pulses, or increased scan time. In this study, we compare the ability of the CHESS, a multi-echo Dixon technique (VARPRO, [2]), and our new method (VCI) to completely delineate the myocardium-fat interface in patients, and the level of fat suppression in phantoms.

Background Sixty-four and more-slice cardiac CT provides rapid and high quality coronary CT angiography for the majority of clinical needs of non-invasive evaluation of coronary artery. However, the recent advance of whole-heart coronary MRA has been able to provide high-quality of coronary MRA and also myocardial image in a reasonable scan time. The purpose of this study was to evaluate the clinical indication and the feasibility of coronary MRA with 32-channel coil at 3T scanner.

To evaluate the performance of compressed sensing for motion correction (CosMo) [1] in compensating the respiratory motion of the heart in 3D late gadolinium enhancement (LGE) CMR.

Background Recent studies have shown the prognostic value of the infarct border zone of late gadolinium enhancement (LGE) images in patients with myocardial infarction [1]. This border zone has also been associated with ventricular arrhythmia [2,3]. The accuracy of the characterization of this area depends on spatial resolution of the imaging. 3D LGE allows improved spatial resolution, especially in through-plane direction. However imaging with an isotropic spatial resolution necessitates very long scan time. In this study, we sought to investigate if compressed-sensing (CS) based image acceleration method [4] allows LGE imaging with isotropic spatial resolution.

Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging.

The distribution of viable and infarcted myocardium is typically visualized using inversion recovery (IR) late gadolinium enhancement (1) or phase-sensitive inversion recovery (PSIR) sequences (2). Transitioning PSIR from breath-hold 2D to respiratory navigator-gated 3D imaging promises higher SNR and CNR, and whole heart coverage (3,4). However, the optimal method for motion compensation with 3D PSIR is undetermined. With standard PSIR, the IR-prepared volume (first heartbeat) is corrected with the phase from the reference volume (second heartbeat), (Fig ​(Fig1a).1a). Current implementations of respiratory navigated 3D PSIR accept data for the reference based solely on navigator NAV1, which takes place over a heartbeat in advance. Respiratory motion occuring between NAV1 and reference volume acquisition, potentially corrupts reference image quality and may compromise the PSIR image. We propose an independently navigated PSIR (INPSIR) sequence with a separate navigator, NAV2, dedicated to motion compensation of the reference volume (Fig ​(Fig1b1b). Figure 1 Schematic of PSIR and INPSIR acquisitions. The second independent navigator provides motion compensation for the phase reference images. Methods Imaging was performed on a 3T system (Philips Healthcare, Best, The Netherlands) using a 32-channel cardiac array coil (InVivo, Gainsville FL). Phantoms: agar gel phantoms with varying T1 values were placed on a pneumatic motor that oscillated 20 mm in the antero-posterior direction every second. Animals: Under ACUC-approved protocol, six swine underwent 2 hr LAD occlusion. Imaging took place 4-25 weeks post-infarction and 10-3 min post double-dose injection of Magnevist (Schering, Germany). A 3D GRE sequence with 1.25x1.25x4 mm3 resolution and 2.5 min scan time ( assuming 100% gating efficiency) was used.

Background Many adult patients with secundum-type atrial septal defects (ASDs) are able to have these defects fixed percutaneously. Traditionally, this has involved an assessment of ASD size, geometry and atrial septal margins by transoesophageal echocardiography (TOE) prior to percutaneous closure. This is a semi-invasive technique, and all of the information obtained could potentially be obtained by non-invasive cardiovascular magnetic resonance (CMR). We compared the assessment of ASDs in consecutive patients being considered for percutaneous ASD closure using CMR and TOE. Methods Consecutive patients with ASDs diagnosed on transthoracic echocardiography (TTE) were invited to undergo both CMR and TOE. Assessment of atrial septal margins, maximal and minimal defect dimensions was performed with both techniques. Analyses between CMR and TOE were made using simple linear regression and Bland Altman Analyses. Results Total CMR scan time was 20 minutes, and comparable to the TOE examination time. A total of 20 patients (M:F = 5:15, mean age 42.8 years ± 15.7) were included in the analyses. There was an excellent agreement between CMR and TOE for estimation of maximum defect size (R = 0.87). The anterior inferior, anterior superior and posterior inferior margins could be assessed in all patients with CMR. The posterior superior margin could not be assessed in only one patient. Furthermore, in 1 patient in whom TOE was unable to be performed, CMR was used to successfully direct percutaneous ASD closure. Conclusions CMR agrees with TOE assessment of ASDs in the work-up for percutaneous closure. Potentially CMR could be used instead of TOE for this purpose.

Introduction Strain encoding(SENC) is a newly-developed MRI technique for measuring myocardial strain in the throughplane direction [1]. With conventional k-space acquisition, SENC requires two separate acquisitions to obtain two sets of images (low-tune(LT) and high-tune(HT)), which are combined to obtain the strain image. Non-Cartesian k-space trajectories are becoming more popular because they allow for data undersampling with acceptable image quality [2]. In this work, SENC was combined with undersampled radial k-space acquisition and interleaved SENC tunings to reduce scan time to one breathhold. The results were compared to conventional SENC images.

Introduction Whole-heart coronary MRA is challenging due to the long data acquisition time on the order of 8-12 minutes. Interleaved EPI using Cartesian k-space sampling has been reported for reducing the scan time of whole-heart coronary MRA [1]; however, this method suffers from an increased sensitivity to motion artifacts [2]. The purpose of this work was to optimize a radial EPI [3] technique for contrast-enhanced whole-heart coronary MRA, with the goal of combining the scan efficiency of EPI with the motion insensitivity of radial sampling.

Introduction Although infarct size by late gadolinium enhancement (LGE) CMR imaging is a robust prognostic marker in patients with recent MI, long scan times and repeated breathholds associated with the current standard, singleslice 2D multiple-breathhold (SS2D), limit clinical use of this technique. Two new techniques, whole-heart 2D single-breathhold (WHOLE) and navigator-guided 3D freebreathing (3DNAV), offer the advantages of decreased scan time and higher spatial resolution without breathholding, respectively.

Introduction: The development of contrast enhanced whole heart coronary MR angiography (CMRA) at 3T has shown promising results in clinical studies for the detection of significant coronary artery stenoses. However, the imaging time (~ 9 minutes) and spatial resolution (1.3 × 1.3 × 1.3 mm) remain major limitations. Newly available 32-channel cardiac coils allow greater acceleration factors, and thus reduced imaging time, reduced contrast agent dose and higher spatial resolution. Purpose: To evaluate the diagnostic accuracy of 3T contrast enhanced whole-heart CMRA with an optimized protocol for improved spatial resolution and reduced scan time using a 32-channel cardiac coils. Imaging time, image quality score, and diagnostic accuracy are evaluated in 32 consecutive patients with suspected coronary artery disease using conventional x-ray coronary angiography (CAG) as reference standard. Methods and Materials: 32 patients with suspected coronary artery disease who were scheduled for coronary angiography (CAG) (mean age 62 ± 12 y) underwent MRCA at 3T (MAGNETOM Tim Trio, Siemens) after informed consent was obtained. A 32-channel receiver coil was used for data acquisition (Invivo, Gainesville, FL). For image acquisition an ECG-triggered, navigator-gated, inversion-recovery prepared, segmented gradient-echo sequence was used with an acceleration factor of three in the phase-encoding direction using GRAPPA reconstruction. Imaging parameters included: voxel size 0.55x0.55x0.65 mm (interpolated from 1.1x1.1x1.3 mm), TR/TE = 3.3/1.5 msec, flip angle = 20°, bandwidth = 700 Hz/pixel, TI=200 msec. Contrast agent (0.15 mmol/kg body weight, MultiHance, Bracco, Italy) was intravenously administered at a rate of 0.3 ml/sec. For image analysis, standard 15-segment AHA classification system was used and only segments with a reference diameter of ≥ 1.5 mm were included, excluding those segments distal to complete occlusions. The diagnostic accuracy in detecting significant stenoses (≥50% of vessel lumen) was evaluated on the assessable segments only, as well as on all segments. Both non-assessable segments and the segments of the patients where the scan failed were considered to have a stenosis. Results: Whole-heart CMRA was successfully completed in 30 of 32 (94%) patients who were scheduled for CAG. The averaged imaging time was 5.9 ± 1.2 min. 40 of 392 segments (10%) with a reference luminal diameter > 1.5 mm on QCA were determined as non-assessable. On assessable segments only, the sensitivity, specificity, and accuracy of coronary MRA for detecting significant stenoses were 93% (78-99%), 99% (97-99%), 98%

Background Characterization of carotid artery morphology and plaque composition requires multiple measurements with different contrast-weightings, which are limited by long scan time, image misregistration, and expertise-dependency in image interpretation. Recently, a new method,3D Multicontrast ATherosclerosis CHaracterization (MATCH) has been developed to overcome the above drawbacks by acquiring multi-contrast weighted images in one scan [1] This study was conducted to determine the accuracy of MATCH in the characterization of plaque morphology and composition in patients.

Background Cardiac and respiratory motion artifacts are major challenges to whole-heart coronary MRA. The conventional motion suppression strategies often involve prospective gating based on motion surrogates, e.g. ECG and navigator, which complicates scan setup and prolongs scan time significantly. To address these limitations, an ECG and navigator-free 4D whole-heart coronary MRA technique was recently proposed, providing both cardiac function and coronary artery assessment from a single measurement [1]. In this work, we evaluate the 4D technique by comparing it against conventional cine and coronary MRA protocols.

Background Although using more coils may improve parallel imaging performance, it produces a burden on the amount of calibration data required for autocalibrating methods. This work investigates the use of principal component analysis (PCA) to project the original set of coils onto a smaller set of virtual coils to reduce calibration scan time for through-time radial GRAPPA [Seiberlich, et al. Magn Reson Med. 2011; 65(2):492-505].

Background A typical CMR exam includes cine, tagging, first-pass, and delayed-hyper-enhancement (DHE) imaging. The DHE image is usually acquired at a single timeframe. Nevertheless, obtaining cine DHE images would provide both viability and functional information in single set of images without misregistration problems for better image interpretation. However, repeated breath-hold scans are required to obtain cine DHE images, which increases scan-time with varying level of tissue enhancement with time. In this work, we propose a new technique for generating cine DHE images based on the acquired DHE image and motion field derived from the corresponding tagged images. Methods A mid-diastolic short-axis DHE image and the corresponding set of tagged images were acquired on 3T-MRI scanner. The corresponding cine images were acquired for reference. Image analysis has two steps: 1) apply the Lucas-Kanade optical-flow algorithm to the tagged images to extract the motion field of the myocardium through the cardiac cycle; 2) apply the measured motion field to the known (acquired) DHE image to generate the unknown DHE images. The infarcted regions were identified in the DHE images using the full-width at halfmaximum method. Radial thickening was measured from both cine and DHE images to evaluate the generated images. Infarction transmurality, circumferential strain, and radial thickening were measured from the DHE, tagged, and cine images, respectively, and the relationships between the generated parameters were studied using regression and correlation analyses. Results Figure 1 shows tagged and DHE images. Figure 2 shows transmurality and strain at different segments. Peak infarction transmurality (circumferential strain) were 91% (0%) and 0% (-14%) in the infarcted and lateral regions, respectively. Myocardial thickening, calculated from the DHE images, showed good correlation with the results from the gold-standard cine images (r = 0.72). Further, there was an excellent agreement between ED and ES infarction transmurality calculated from the DHE images (r = 0.998). Infarction transmurality showed good correlation with strain (r = 0.81; y = 0.19x+11.27). Conclusions The developed technique generates composite images that show both viability and functional information in one set of images, which is important for prognostic evaluation of the patient’s condition, e.g. determining candidates for revascularization. The generated images could be also useful for differentiating between gadolinium recess in the muscle and myocardial scar, usually conducted by comparing cine and DHE images side-by-side. Future work includes further improvement of the optical-flow algorithm to minimize error propagation with time, and implementing the algorithm on large number of patients with different degrees of infarction.

Methods Cohorts and Acquisition: 41 volunteers (HV, 25 ± 5 y.), 14 STEMI (63 ± 7 y.), 12 DCM (54 ± 17 y.), and 5 DCM+LBBB (47 ± 8 y.) patients were investigated. Acquisition parameters were: Philips Achieva 3 T, 32 channel cardiac coil, velocity encoded (Tissue Phase Mapping, TPM) segmented black-blood gradient echo with VENC = 30 cm/s, TR/TE = 6.1/4.6 ms, FOV adapted to patient size, resolution = 2x8 mm, 3 k-lines/segment, SENSE = 2, phase interval = 30 ms, and nominal scan time = 5:51 min:sec for 3 short axis slices. Parameters (see [1]): a) velocity-based: Standard Deviation of Times to Peak [SD(TTP)], Asynchrony Correlation Coefficient [ACC], Temporal Uniformity of Velocity [TUV], and Velocity Ranges (difference: maximum-minimum velocity). b) strain-based: Base Apex Rotation Correlation [BARC], Temporal Uniformity of Strain [TUS], Standard Deviation of Onset/Peak Time [SD(T)], Coefficient of Variation [CV], Difference between Septal and Lateral Peak Circumferential Strain [DiffSLpeakCS], Onset/Peak Of Shortening Delay [Delay], Regional Variance of Strain [RVS], and Regional Variance Vector of Strain [RVVPS]. Analysis: The significance of resulting differences between the different groups was assessed via non-parametric Kruskal-WallisTest.

Background Through-Time non-Cartesian GRAPPA, a novel parallel imaging method for non-Cartesian trajectories, has recently been shown to provide real-time, free-breathing cardiac images with temporal resolutions of less than 35 ms per frame [Seiberlich N, et al. MRM 2011 Dec;66 (6):1682-8]. The drawback to this method is the need for several fully-sampled datasets for calibration stemming from the non-Cartesian nature of the data, which leads to a longer overall scan time. By acquiring interleaved spiral datasets and combining them to form fully-sampled datasets for the generation of the GRAPPA weights, as in TGRAPPA [Breuer FA, et al. MRM 2005 Apr;53(4):9815.], there is no need for additional calibration data. However, this interleaved calibration method poses the risk of increased artifacts if the temporal footprint of the calibration data is too long. The goal of this study is to test the extent to which self-calibrating through-time spiral GRAPPA can be used for real-time free-breathing CMR.

Background Pulmonary arterial hypertension (PAH) is characterized by progressive increase in pulmonary vascular resistance (PVR), leading to right ventricular (RV) failure [1]. PVR is calculated using right heart catheterization (RHC), from the trans-pulmonary pressure gradient (ΔP) and pulmonary flow (QPA). Doppler echocardiography can estimate PVR from the ratio of peak tricuspid regurgitation velocity (TRV) to main pulmonary artery velocity time-integral (MPA flow) [2]. MRI is increasingly used to assess right ventricular (RV) function in PAH. Determining PVR from MRI could enable a more complete characterization of RV and PA interactions in PAH. The purpose of this study was to non-invasively estimate PVR from TRV/QPA using a 4D flow-sensitive MRI sequence in humans [3]. Methods Six PAH patients referred for right heart catheterization (RHC) and six healthy volunteers were scanned according to an IRB-approved protocol. In patients, RHC was performed clinically within 1 week of the MRI in patients with PAH. PVRRHC was calculated as follows: PVR=ΔP/QPA. 4D flow MRI (Phase Contrast with Vastly undersampled Isotropic Projection Reconstruction - PC VIPR) was performed on 3T clinical scanners (GE Healthcare, Waukesha, WI) after the administration of gadolinium-based contrast agents. PC VIPR parameters: FOV=32 x 32 x 22 cm, isotropic 1.3 mm spatial resolution, TR/TE = 6.3/2.1 ms, Venc=150 cm/s, scan time: ~10 min using respiratory and retrospective ECG gating. Post-processing was done using Ensight (CEI, Apex, NC) and MatLab (The Mathworks, Natick, MA) to measure peak TRV and QPA. Statistical analysis included regression analysis to evaluate the correlation between TRV/QPA and PVRRHC. Ar egression equation was derived to calculate PVRMRI. Differences between PVRMRI and PVRRHC were assessed using Bland-Altman analysis. TRV/QPA ratios in healthy controls were compared to those in PAH patients using Student t-test. Results Average (± standard deviation) PVRRHC was 7.15 ± 3.56 UW. The Pearson correlation coefficient between TRV/QPA and PVRRHC was 0.94. The equation derived from linear regression was PVRMRI = 0.69*PVRRHC 2.84 UW. Using this equation, the average (± standard deviation) PVRMRI was 7.15 ± 3.35 (p=0.99). The mean difference between PVRMRI and PVRRHC was 0 with positive and negative levels of agreement of 2.4 and -2.4, respectively. Differences in TRV/QPA in healthy controls and PAH patients were statistically significant (p=0.0003).

Summary To investigate the performance of a novel algorithm for correcting respiratory-induced heart motion for wholeheart coronary MRI. Background A right hemi-diaphragm (RHD) respiratory navigator is commonly used to suppress the respiratory motion of the heart in coronary MRI [1]. Typically, a small 5mm end expiratory gating window (GW) is used to gate data. While this technique successfully suppresses respiratory motion, it prolongs scan time due to navigator efficacies of only 30-50%. Increasing the GW to 15mm would increase the navigator efficiency. In this study, we present a novel respiratory motion correction algorithm which allows increasing the GW to 15mm. Methods Whole-heart coronary MRI with isotropic 1.3mm 3 resolution was acquired using partial Fourier and a navigator with 15mm GW on a 1.5T Philips CMR scanner from 10 healthy subjects (4 males; 29 ± 13 yr). The navigator RHD positions were used to sort the acquired k-space segments into 15 separate 1mm bins (based on their displacement). To compensate for the respiratory motion of the heart, all k-space segments acquired in each bin were assigned a 3D translation parameter. The 3D translation parameter was estimated using an iterative gradient descent optimization algorithm to correct the kspace segments such that the sharpness of the image, reconstructed using the corrected k-space segments, is maximized. The variance of the gradient of the image was used as the measure for the image sharpness [2]. For comparison, another whole-heart coronary MRI dataset was acquired using the same sequence and a navigator with a 5mm GW.

Background Evaluation of cardiac function is clinically performed using multi-slice breath-hold (BH) acquisition, in which patient breathes for a period of 40-60 seconds between a BH of 10-12 seconds. This results in suboptimal data acquisition efficiency. In this study, we propose to take advantage of the time between multiple BHs to acquire additional free-breathing (FB) data that can be used in the reconstruction of undersampled BH acquisition without increasing the total scan time.

Background Parallel imaging can reduce scan time with typical reduction factors of ~2, often not sufficient to reduce scan time to breath hold duration. Spatiotemporal parallel imaging such as k-t-GRAPPA allows for a significantly higher speed-up in data acquisition, but previous studies mostly acquired full k-space data while removing data retrospectively. Here, aortic flow scans were acquired during breath-hold using kt-GRAPPA based reconstruction [1,2] and compared to conventional protocols using GRAPPA and navigator respiration gating.

Background and objective The Modified Look-Locker Inversion-Recovery (MOLLI) sequence (Messroghli, et al, JMRI, 2007) was optimized for myocardial T1 mapping on 1.5T. However, little data exists on T1 mapping at 3T. The standard MOLLI sequence uses three inversion-recovery blocks to acquire 11 images over 17 heartbeats (HB). The long breath hold could limit its clinical application in patients with cardiorespiratory compromise. A new 11 HB MOLLI protocol with two inversion-recovery blocks was introduced recently, which reduces scan time by 35%. This aim of this study is to verify both 17 HB and 11 HB MOLLI sequences at 3T.

Background Balanced steady-state free precession (bSSFP) imaging [1] has developed as the method of choice for coronary MRA at 1.5T. The bSSFP acquisition, however, is especially susceptible to static magnetic field (B0) inhomogeneities and radio frequency transmit field (B1+) distortions, both of which are more pronounced at higher field strengths, resulting in degraded and variable image quality at 3.0T compared to 1.5T. Although modified bSSFP sequences have been recently developed [2], these modified implementations too come with notable drawbacks such as longer scan time and lower SNR compared with conventional bSSFP. Therefore, the adoption of bSSFP at 3.0T is still quite limited and it has led to reutilization of spoiled gradient echo techniques at 3.0T, sometimes at the expense of using contrast agents [3]. Recent advances in hardware and software, such as 32-channel receive coils, multitransmit systems, and localized shimming, may however improve the performance of bSSFP at 3.0T. The purpose of this work was to develop an accelerated single breathhold bSSFP sequence at 3.0T taking advantage of these advances, and to test reproducibility of the implemented sequence.

A respiratory motion correction method (SEGMO) is proposed for whole-heart coronary MRA. It eliminates the need for a diaphragm navigator, reduces imaging setup time, and has more accurate respiratory motion detection using an affine model. Its inherent 100% gating efficiency ensures a shorter and more fixed scan time compared to conventional navigator gated schemes.

Background Assessment of fibrosis in thinner myocardial structures such as the right ventricular (RV) and left atrial walls would be valuable in disorders such as pulmonary hypertension, congenital heart disease, and atrial fibrillation. We recently developed a novel technique, termed ANGIE, which provides high-resolution 2D T1 mapping for assessment of thin structures such as the wall of the RV. However, high resolution 2D imaging is limited by lower SNR and time efficiency. A 3D image acquisition provides higher SNR and complete coverage of the heart. However standard 3D navigated techniques have prohibitively long scan times. Thus, the aim of the present study was to extend ANGIE to perform high-resolution three-dimensional (3D) T1 mapping of the whole heart within a clinically acceptable scan time.

The feasibility of using spiral readouts to reduce the scan time of 4D flow MRI without sacrificing data quality was investigated.

Background Despite being the gold standard for left ventricular function evaluation, traditional SSFP sequences still require multiple breath-holds and a relatively long scan time. This extends total duration of the exam, especially in children or adults with impaired cardiopulmonary capacity. We sought to compare a technique employing a prototype sparse sampling with iterative reconstruction (SSIR) for rapid evaluation of the left ventricle (Liu J et al. ISMRM; 2012) in a single breath-hold and freebreathing (FB) compared to traditional SSFP sequences and temporal parallel imaging methods.

Background PVM is an established technique for measuring blood [1] and myocardial velocities [2]. However, long scan times can restrict its application. Peak-GRAPPA has been used to accelerate Cartesian PVM up to a factor of 6 (R = 6) without degrading peak velocity measurements [3], however use of efficient k-space trajectories could allow higher temporal resolution (TR) in similar scan time. Through-time spiral GRAPPA allows highly accelerated spiral data to be reconstructed using throughtime calibration information [4]. By collecting multiple repetitions of fully sampled calibration data, which can be collected without gating during free breathing, through-time information can be used to generate GRAPPA weights specific to the local undersampling in the non-Cartesian data. This abstract presents preliminary work on a single volunteer to apply this reconstruction to myocardial spiral PVM data.

Introduction Limited temporal resolution underestimates peak velocities assessed by phase contrast MRI (PC-MRI) [1]. Segmented EPI with partial Fourier as previously proposed [2] has relatively long TE, and is prone to chemical-shift artifact. We propose centric reordered water-excitation EPI for PC-MRI with short TE and fat suppression. It improves temporal resolution by twofold while halving scan time compared with turboFLASH.

Background The dual bolus method is conventionally used for quantification of myocardial blood flow (MBF). The method necessitates an additional scan for each first-pass measurement, which increases total scan time and is sensitive to change in heart rates between the two scans. A single scan method to measure the arterial input function (AIF) using highly constrained back projection (HYPR) reconstruction for integrated T1 mapping was previously developed [1]. Mistriggering due to arrhythmias, changing heart rates, and poor electrocardiogram (ECG) signal may cause motion artifacts in HYPR reconstructed images because data is shared across multiple cardiac cycles. We propose using a non-ECG-triggered acquisition with cardiac motion self-triggering for integrated T1 mapping derived AIF for MBF quantification.

Background In conventional prospective respiratory navigator (NAV) acquisitions, 40-60% of the acquired data are discarded resulting in low efficiency and long scan times [1,2]. Compressed-sensing Motion Compensation (CosMo) has a shorter fixed scan time by acquiring the full inner k-space and estimating the NAV-rejected outer k-space lines [3]. Respiratory motion will mainly manifest itself as phase variation in the acquired k-space data. We sought to determine if the addition of the magnitude of the rejected k-space lines as a constraint in image reconstruction will improve the performance of CosMo.