Murilo Foppa

Accuracy, Precision, and Reproducibility of Four T1 Mapping Sequences: A Head-to-Head Comparison of MOLLI, ShMOLLI, SASHA, and SAPPHIRE

PURPOSEnTo compare accuracy, precision, and reproducibility of four commonly used myocardial T1 mapping sequences: modified Look-Locker inversion recovery (MOLLI), shortened MOLLI (ShMOLLI), saturation recovery single-shot acquisition (SASHA), and saturation pulse prepared heart rate independent inversion recovery (SAPPHIRE).nnnMATERIALS AND METHODSnThis HIPAA-compliant study was approved by the institutional review board. All subjects provided written informed consent. Accuracy, precision, and reproducibility of the four T1 mapping sequences were first compared in phantom experiments. In vivo analysis was performed in seven healthy subjects (mean age ± standard deviation, 38 years ± 19; four men, three women) who were imaged twice on two separate days. In vivo reproducibility of native T1 mapping and extracellular volume (ECV) were measured. Differences between the sequences were assessed by using Kruskal-Wallis and Wilcoxon rank sum tests (phantom data) and mixed-effect models (in vivo data).nnnRESULTSnT1 mapping accuracy in phantoms was lower with ShMOLLI (62 msec) and MOLLI (44 msec) than with SASHA (13 msec; P < .05) and SAPPHIRE (12 msec; P < .05). MOLLI had similar precision to ShMOLLI (4.0 msec vs 5.6 msec; P = .07) but higher precision than SAPPHIRE (6.8 msec; P = .002) and SASHA (8.7 msec; P < .001). All sequences had similar reproducibility in phantoms (P = .1). The four sequences had similar in vivo reproducibility for native T1 mapping (∼25-50 msec; P > .05) and ECV quantification (∼0.01-0.02; P > .05).nnnCONCLUSIONnSASHA and SAPPHIRE yield higher accuracy, lower precision, and similar reproducibility compared with MOLLI and ShMOLLI for T1 measurement. Different sequences yield different ECV values; however, all sequences have similar reproducibility for ECV quantification.

Adaptive registration of varying contrast-weighted images for improved tissue characterization (ARCTIC): Application to T1 mapping

To propose and evaluate a novel nonrigid image registration approach for improved myocardial T1 mapping.

Right Ventricular Volumes and Systolic Function by Cardiac Magnetic Resonance and the Impact of Sex, Age, and Obesity in a Longitudinally Followed Cohort Free of Pulmonary and Cardiovascular Disease: The Framingham Heart Study.

Background—Cardiac magnetic resonance is uniquely well suited for noninvasive imaging of the right ventricle. We sought to define normal cardiac magnetic resonance reference values and to identify the main determinants of right ventricular (RV) volumes and systolic function using a modern imaging sequence in a community-dwelling, longitudinally followed cohort free of clinical cardiovascular and pulmonary disease. Methods and Results—The Framingham Heart Study Offspring cohort has been followed since 1971. We scanned 1794 Offspring cohort members using steady-state free precession cardiac magnetic resonance and identified a reference group of 1336 adults (64±9 years, 576 men) free of prevalent cardiovascular and pulmonary disease. RV trabeculations and papillary muscles were considered cavity volume. Men had greater RV volumes and cardiac output before and after indexation to body size (all P<0.001). Women had higher RV ejection fraction than men (68±6% versus 64±7%; P<0.0001). RV volumes and cardiac output decreased with advancing age. There was an increase in raw and height-indexed RV measurements with increasing body mass index, but this trend was weakly inverted after indexation of RV volumes to body surface area. Sex, age, height, body mass index, and heart rate account for most of the variability in RV volumes and function in this community-dwelling population. Conclusions—We report sex-specific normative values for RV measurements among principally middle-aged and older adults. RV ejection fraction is greater in women. RV volumes increase with body size, are greater in men, and are smaller in older people. Body surface area seems to be appropriate for indexation of cardiac magnetic resonance–derived RV volumes.

Subcutaneous fat thickness, but not epicardial fat thickness, parallels weight reduction three months after bariatric surgery: A cardiac magnetic resonance study

with no significant change in CTR group weight (BMI: 27.2 ± 4.5 kg/m 2 to 27.0 ± 4.7 kg/m 2 ; �0.9 ± 1.4% of body mass; p = 0.06). The absolute and relative changes in fat thicknesses in the BS group were SUBFAT = � 10.1 ±4 .7 mm; 31 ±1 4% (pb 0.001), PARAFAT = �0.7 ± 1.4 mm; 4 ± 11% (p = 0.1), and EPIFAT = +0.2 ± 0.9 mm; �4 ± 11%(p = 0.2),whiletheCTRgroupshowednosignificantchange in any fat component (all p N 0.1). Importantly, there was a significant association between the relative changes inweight (Fig. 2) and SUBFAT (r 2 = 0.52; p = 0.008) and with PARAFAT (r 2 = 0.41; p = 0.02), but not with EPIFAT (r 2 = 0.05; p = 0.5) in the BS group, partially mirroring the baseline associations. These data demonstrate a close relationship between thoracic subcutaneous fat thickness and body weight, with an association that parallels the short term reductions in body weight seen, while epicardial fat thickness did not showan associationwith BMI, or with body weight change. Moreover, the paracardial fat, which might share abdominal visceral fat characteristics, showed an intermediate behavior compared to the other two fat components. Our findings suggest that epicardial fat may have a more subtle or delayed response to weight reduction than that seen in subcutaneous fat.

3D late gadolinium enhancement in a single prolonged breath-hold using supplemental oxygenation and hyperventilation

To evaluate the feasibility of three‐dimensional (3D) single breath‐hold late gadolinium enhancement (LGE) of the left ventricle (LV) using supplemental oxygen and hyperventilation and compressed‐sensing acceleration.

Localized spatio-temporal constraints for accelerated CMR perfusion.

To develop and evaluate an image reconstruction technique for cardiac MRI (CMR) perfusion that uses localized spatio‐temporal constraints.

Subcutaneous fat thickness, but not epicardial fat thickness, parallel weight reduction after bariatric surgery: a cardiac magnetic resonance study

Background Bariatric surgery is a very effective treatment for morbid obesity, generally improving the obesity related metabolic derangements. Epicardial fat (EPIFAT) is a visceral fat depot measurable in cardiac magnetic resonance. Changes in EPIFAT after bariatric surgery has been described, but it is not well characterized. We hypothesized that the reduction of the thoracic fat components after bariatric surgery is heterogeneous.

Diffuse myocardial fibrosis in patients with mitral valve prolapse and ventricular arrhythmia

Objective We aimed to investigate the association of diffuse myocardial fibrosis by cardiac magnetic resonance (CMR) T1 with complex ventricular arrhythmia (ComVA) in mitral valve prolapse (MVP). Methods A retrospective analysis was performed on 41 consecutive patients with MVP referred for CMR between 2006 and 2011, and 31 healthy controls. Arrhythmia analysis was available in 23 patients with MVP with Holter/event monitors. Left ventricular (LV) septal T1 times were derived from Look-Locker sequences after administration of 0.2u2005mmol/kg gadopentetate dimeglumine. Late gadolinium enhancement (LGE) CMR images were available for all subjects. Results Patients with MVP had significantly shorter postcontrast T1 times when compared with controls (334±52 vs 363±58u2005ms; p=0.03) despite similar LV ejection fraction (LVEF) (63±7 vs 60±6%, p=0.10). In a multivariable analysis, LV end-diastolic volume, LVEF and mitral regurgitation fraction were all correlates of T1 times, with LVEF and LV end-diastolic volume being the strongest (p=0.005, p=0.008 and p=0.045, respectively; model adjusted R2=0.30). Patients with MVP with ComVA had significantly shorter postcontrast T1 times when compared with patients with MVP without ComVA (324 (296, 348) vs 354 (327, 376) ms; p=0.03) and only 5/14 (36%) had evidence of papillary muscle LGE. Conclusions MVP may be associated with diffuse LV myocardial fibrosis as suggested by reduced postcontrast T1 times. Diffuse interstitial derangement is linked to subclinical systolic dysfunction, and may contribute to ComVA in MVP-related mitral regurgitation, even in the absence of focal fibrosis.

Whole heart coronary imaging with flexible acquisition window and trigger delay

Coronary magnetic resonance imaging (MRI) requires a correctly timed trigger delay derived from a scout cine scan to synchronize k-space acquisition with the quiescent period of the cardiac cycle. However, heart rate changes between breath-held cine and free-breathing coronary imaging may result in inaccurate timing errors. Additionally, the determined trigger delay may not reflect the period of minimal motion for both left and right coronary arteries or different segments. In this work, we present a whole-heart coronary imaging approach that allows flexible selection of the trigger delay timings by performing k-space sampling over an enlarged acquisition window. Our approach addresses coronary motion in an interactive manner by allowing the operator to determine the temporal window with minimal cardiac motion for each artery region. An electrocardiogram-gated, k-space segmented 3D radial stack-of-stars sequence that employs a custom rotation angle is developed. An interactive reconstruction and visualization platform is then employed to determine the subset of the enlarged acquisition window for minimal coronary motion. Coronary MRI was acquired on eight healthy subjects (5 male, mean age = 37 ± 18 years), where an enlarged acquisition window of 166–220 ms was set 50 ms prior to the scout-derived trigger delay. Coronary visualization and sharpness scores were compared between the standard 120 ms window set at the trigger delay, and those reconstructed using a manually adjusted window. The proposed method using manual adjustment was able to recover delineation of five mid and distal right coronary artery regions that were otherwise not visible from the standard window, and the sharpness scores improved in all coronary regions using the proposed method. This paper demonstrates the feasibility of a whole-heart coronary imaging approach that allows interactive selection of any subset of the enlarged acquisition window for a tailored reconstruction for each branch region.

Accelerated cardiac MR stress perfusion with radial sampling after physical exercise with an MR-compatible supine bicycle ergometer

To evaluate the feasibility of accelerated cardiac MR (CMR) perfusion with radial sampling using nonlinear image reconstruction after exercise on an MR‐compatible supine bike ergometer.