Cardiac MRI Techniques Research Articles

MRI monitoring of myocardial iron overload: use of cardiac MRI combined with hepatic MRI in a cohort of multi-transfused patients with thalassaemia.

We report the results of combining cardiac and hepatic MRI in the same examination to monitor 48 multi-transfused patients presenting iron overload secondary to their transfusions. This cardiac MRI technique uses acquisition sequences and calculation software that are readily available for 1.5 T systems, and it has been validated to screen for patients at risk of cardiac complications who present myocardial iron overload (T2*<20milliseconds). A total of 176 combined MRI examinations were performed between May 2006 and January 2012 in 48 patients who had received transfusions due to thalassaemia. This monocentric retrospective study brings together all of the imaging examinations carried out. There was a positive correlation between the cardiac T2* values and left ventricular ejection fraction, which were measured in the same examination. At the first assessment 23/48 patients had a T2*<20ms. These patients showed a significant improvement in cardiac T2* over time while their iron chelation therapy was being intensified. This study validates the application of the cardiac MRI technique used to monitor cardiac iron overload in patients who have undergone multiple transfusions.

Non–ECG‐gated myocardial perfusion MRI using continuous magnetization‐driven radial sampling

Establishing a high-resolution non-ECG-gated first-pass perfusion (FPP) cardiac MRI technique may improve accessibility and diagnostic capability of FPP imaging. We propose a non-ECG-gated FPP imaging technique using continuous magnetization-driven golden-angle radial acquisition. The main purpose of this preliminary study is to evaluate whether, in the simple case of single-slice two-dimensional imaging, adequate myocardial contrast can be obtained for accurate visualization of hypoperfused territories in the setting of myocardial ischemia. A T1-weighted pulse sequence with continuous golden-angle radial sampling was developed for non-ECG-gated FPP imaging. A sliding-window scheme with no temporal acceleration was used to reconstruct 8 frames/s. Canines were imaged at 3T with and without coronary stenosis using the proposed scheme and a conventional magnetization-prepared ECG-gated FPP method. Our studies showed that the proposed non-ECG-gated method is capable of generating high-resolution (1.7 × 1.7 × 6 mm(3) ) artifact-free FPP images of a single slice at high heart rates (92 ± 21 beats/min), while matching the performance of conventional FPP imaging in terms of hypoperfused-to-normal myocardial contrast-to-noise ratio (proposed: 5.18 ± 0.70, conventional: 4.88 ± 0.43). Furthermore, the detected perfusion defect areas were consistent with the conventional FPP images. Non-ECG-gated FPP imaging using optimized continuous golden-angle radial acquisition achieves desirable image quality (i.e., adequate myocardial contrast, high spatial resolution, and minimal artifacts) in the setting of ischemia.

Abstract 18181: Real-Time Non-ECG-Gated First-Pass Perfusion MRI Enabling Concurrent Assessment of Myocardial Function and Perfusion Abnormalities

Introduction: Combined assessment of wall motion and perfusion abnormalities from cardiac MRI (CMRI) has been shown to have a high performance for diagnosis of coronary artery disease (CAD). CMRI acquisition, however, is hindered by study length, presence of arrhythmias, and the need for synchronization with cardiac cycle via ECG gating. We developed a new non-ECG-gated CMRI technique capable of simultaneously capturing perfusion and wall motion abnormalities in a single 1-minute scan. Hypothesis: Real-time (non-ECG-gated) CMRI can detect perfusion abnormalities with high image quality and enables assessment of wall motion from the same data. Methods: A novel real-time MRI method was developed for ungated first-pass perfusion (FPP) imaging (continuous T1-weighted scan). Canines (n=5) with reversible ischemia (severe LAD stenosis) were studied using both the real-time and gated (conventional) methods. Six normal subjects and 1 patient (suspected CAD) had stress/rest real-time FFP CMRI. The patient also underwent Rb-82 stress/rest myocardial perfusion PET. Results: The real-time FPP stress/rest human studies were all of high quality. The 6 normal subjects demonstrated normal perfusion and function. In the patient, stress-induced hypoperfusion was observed, corresponding to a reversible defect on PET (Figure). In animals, real-time FPP achieved high contrast-to-noise ratio between hypoperfused/remote territories (real-time: 5.2, gated: 4.8). Wall thickening abnormalities (17 frames/s) were observed in hypoperfused areas. Conclusions: A novel approach to FPP CMRI has been developed that does not use ECG gating. Preliminary results in animals with ischemia and at stress/rest in humans were of high quality and showed expected perfusion findings. The real-time method is an attractive alternative to conventional CMRI with the advantage of simplicity (no gating), speed (concurrent MRI of function and perfusion), and potentially improved reliability.

Cardiac Mri of Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a major cause of morbidity and mortality worldwide. New serological biomarkers, such as troponins, have improved the diagnosis of ACS; however, the diagnosis of ACS can still be difficult as there is marked heterogeneity in its presentation and significant overlap with other disorders presenting with chest pain. Evidence is accumulating that cardiac MRI provides information that can aid the detection and differential diagnosis of ACS, guide clinical decision-making and improve risk-stratification after an event. In this review, we present the relevant cardiac MRI techniques that can be used to detect ACS accurately, provide differential diagnosis, identify the sequelae of ACS, and determine prognostication after ACS.

Concentric rings with k-t acceleration enables rapid and effective fat-water-separated cardiac cine MRI at 3 T

Background Cine imaging is the core technique for cardiac MRI studies. Often times, it is also essential to have information identifying fat signal in the heart to characterize masses, detect fatty infiltration and ARVD, discern fat from fibrosis in LGE imaging, and improve visualization of the pericardium. However, such information traditionally requires additional scans that obtain fat-suppressed images for comparison. This prolongs the examination time, is susceptible to mis-registration between the fatsuppressed and fat-visible images, and does not directly utilize positive contrast from fat. In this work, we present an integrated cardiac MRI technique that produces coregistered cines of both water and fat signal from a rapid single-breath-hold scan.

134 MRI Detection and Quantitative T2 Measurement of Cardiac Involvement in Systemic Sarcoidosis: Initial Results

Cardiac involvement (CI) in patients with systemic sarcoidosis is a major risk factor for sudden cardiac death. The incidence of CI on autopsy can be up to 40% although it is only observed in 5-10% patients diagnosed clinically with systemic sarcoidosis. Early detection of CI may therefore potentially alter prognosis and treatment options. In this study, we investigated the prevalence of CI in a cohort of biopsy proven sarcoid patients using quantitative cardiac MRI techniques of late-gadolinium-enhancement (LGE) and T2 mapping. 28 patients with systemic sarcoidosis, but without overt cardiac involvement [17 males (60%), ages of 50±10 years] had undergone an MRI study on a 1.5T magnet system. Pre-contrast MRI included left ventricular (LV) and right ventricular (RV) function and quantitative T2 measurements using T2 maps derived from a Multi-echo fast-spin-echo sequence (MEFSE) or T2 preparation spiral scan. Post-contrast LGE-MRI included inversion recovery fast-gradient-echo (IR-FGRE) and multi-contrast late-enhancement (MCLE) imaging. CMR42 was used for ventricular function measurement, LGE determination and quantitative T2 calculation. LV functional parameters in 28 patients were normal while the RV function was decreased (mean LVEF: 61.2±8.5%; mean RVEF 48.0±6.6%). 21.4% of subjects (6/28) had CI showing patchy or multiple focal hyper-enhancement patterns in LV free wall, papillary muscles (PM) or inter-ventricular septum. In two cases with PM involvement, the PM abnormal LGE foci were only observed on MCLE. The LV systolic function was preserved in patients with CI (n=6, LVEF=59.4±12.1%). For pre-contrast T2 measurements at the mid-LV level, there was no significant difference in T2 averaged over the myocardium between LGE negative (n=22) and positive group (n=6) (LGE negative vs. positive: 53.0±2.6 ms vs.53.4±2.4 ms, p=0.76). However, a significant decrease in T2 was observed in LGE-positive regions, compared to the LGE negative group (focal LGE-positive regions vs. negative: 40.0±2.4 ms vs. 53.0±2.6 ms, p<0.0001). Extra-cardiac MRI findings were documented in 63.4% of patients, primarily hilar and mediastinal lymph node enlargement. In three LGE-positive patients, follow-up MRI at 15-26 months demonstrated LGE foci were stable in 2 subjects whilst one subject demonstrated new transmural LGE. LGE-MRI especially MCLE method can detect cardiac involvement in sarcoidosis. In focal areas of LGE, there is a decrease in T2. This may be secondary to asteroid bodies containing calcified proteins - suggesting chronic stable disease. Changes in T2 might therefore reflect different phases of cardiac sarcoid, thus providing a non-invasive method for monitoring disease and therapy.

The impact of physiological loading on immune cell infiltration and myocardial function evaluated by cardiac MRI: a comparison between non-working heart and working heart transplant models

Summary Rodent models of heterotopic cardiac transplantation are important for gaining a better understanding of heart allograft rejection. This study compared a working heart (WkHt) transplant model, which have developed by our laboratory, with the traditional non-working heart (Non-WkHt) model using cardiac MRI (CMRI) and pathological evaluation. Our results indicate that the physiological hemodynamic loading significantly impacts graft immune cell infiltration and myocardial function. Our WkHt transplant model with intact pulmonary circulation, retains hemodynamic loading close to that of native heart, and is thus more appropriate for both functional and immunological studies, especially for developing the clinically relevant CMRI techniques for comprehensive evaluation of the heart graft. Background The traditional heterotopic heart transplantation rodent model [1,2] lacks blood flow toward left ventricle (LV) and the graft does not pump blood, and therefore is a non-working heart (Non-WkHt). We have developed a new heterotopic working heart (WkHt) transplant model with intact pulmonary circulation to study cardiac allograft rejection.[3] In this study, we used combinations of pathology and multi-parameter CMRI, such as cine, Tagging, and T1/T2, to comprehensively evaluate the impact of physiological loading on the myocardial function, immune cell infiltration and graft pathophysiological condition of these 2 models.

Cardiac MRI for the Assessment of Cardiac Function in the Newborn

While many aspects of neonatal care have progressed rapidly in recent decades, circulatory management remains at a virtual standstill. The wide variation in intervention to treat low blood pressure and ductal patency between different neonatal units highlights how little evidence is available to guide management decisions. The paucity of biomarkers to assess key elements of circulatory function perpetuates this clinical uncertainty. While echocardiography has undoubtedly produced some advances in understanding, the method is limited by poor repeatability and user-dependency of measurements. Cardiac MRI techniques have produced significant advances in understanding of adult circulatory physiology and are the gold standard for adult cardiac function assessments. Our group has now implemented cardiac MRI techniques in newborn term and preterm infants. Scans can be performed safely, without the need for sedation/anaesthesia, and with maintenance of cardiorespiratory and thermal stability. We acknowledge that cardiac MRI will not be used as a cotside tool for circulatory assessment in the foreseeable future. However in this talk we present our initial experience with the technique, and how we believe the technique could (i) - increase understanding of circulatory pathophysiology in the newborn, (ii) - guide development of emerging echocardiographic techniques and (iii) - act as a powerful biomarker in clinical trials of therapeutic intervention.

Fulminant myocarditis owing to high-dose interleukin-2 therapy for metastatic melanoma

High-dose interleukin-2 (IL-2) therapy may cause acute myocarditis characterised by diffuse myocardial involvement and occasionally fulminant heart failure. Cardiac MRI (CMRI) provides a comprehensive assessment of myocardial function, inflammation and injury in a single examination and has shown value in the diagnosis of myocarditis. We report a case of a 54-year-old male with metastatic melanoma who developed acute severe myocarditis with fulminant heart failure after high-dose IL-2 therapy. CMRI using a combination of T(2) weighted imaging and T(1) weighted late post-gadolinium enhancement techniques played a key role in establishing the diagnosis. To our knowledge we present the first case report of the combined use of T(1) and T(2) weighted CMRI techniques to diagnose IL-2 induced myocarditis.

Right ventricular function by MRI

For years, the right ventricle (RV) has been deemed 'unnecessary', as shown by procedures such as Fontan surgery. More recently, right ventricular dysfunction has been recognized as a prognostic factor in many cardiovascular diseases. Supported by advances in echocardiography and MRI, assessment of right ventricular function and morphology has gained interest. The goal of this review is to offer a current clinical perspective on right ventricular function as assessed by MRI. MRI has progressed towards a fast and reliable technique for assessing right ventricular morphology, volumes and function. Strain-encoded techniques and single breath-hold four-dimensional acquisition techniques are promising, but need to be confirmed in patient studies. Continuous improvement in postprocessing software has further reduced analysis time and effort. Our understanding of right ventricular behavior even in complex heart disease has taken substantial benefit from modern cardiac MRI techniques. MRI imaging of the RV is patient-tailored, integrating right ventricular volumetric and functional analysis in a comprehensive approach, including assessment of cardiac morphology, myocardial tissue characteristics, flow patterns and great vessel anatomy. This approach provides the clinician a complete view, not only of the RV as such, but also of the RV being an essential part of the cardiopulmonary system.

Acute Myocarditis: Noninvasive Evaluation with Cardiac MRI and Transthoracic Echocardiography

The diagnosis of acute myocarditis is challenging. Nonspecific clinical presentation and an overlap with the diagnosis of acute myocardial infarction present a diagnostic dilemma. The purpose of this article is to describe the role of cardiac MRI and transthoracic echocardiography (TTE) in the diagnosis of acute myocarditis. Thirty-two sequential patients (all male; average age, 33 years) with clinically suspected myocarditis were included. All patients underwent cardiac MRI with sequences dedicated for the evaluation of myocardial delayed enhancement and TTE for the evaluation of wall motion abnormalities (WMAs). Nine patients were excluded because of diagnosis of acute myocardial infarction (n=2) or inadequate cardiac MRI technique (n=7). Retrospective analysis of the images of the remaining 23 patients was performed. An epicardial pattern of abnormal patchy myocardial delayed enhancement was seen on cardiac MRI in 21 of 23 (91%) patients. WMAs were seen on TTE in eight of 23 (35%) patients. Regional rather than global involvement was seen mainly in the inferolateral segments, with a predominance in the midventricular portion. Cardiac MRI might have a greater impact than TTE in confirming the presence of acute myocarditis and evaluating the extent of myocardial involvement. Cardiac MRI provides noninvasive imaging that may obviate invasive procedures such as coronary catheter angiography or endomyocardial biopsy.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy is recognized as an important cause of death in young patients, particularly athletes. In the past 5 years, cardiac MRI techniques have evolved rapidly in an attempt to improve the noninvasive diagnosis of this disorder. Steady-state free precession sequences and more rapid fat saturation techniques have permitted a comprehensive and well-tolerated examination. The first formal testing of diagnostic accuracy among a broad range of readers has recently been completed. Despite these advances, limited spatial resolution and interobserver variability have prevented successful implementation of these methods. Future approaches may include high-field imaging at 3 Tesla, and viability imaging to improve diagnostic accuracy.

Cardiac Sarcoidosis in a Patient With Hypertrophic Cardiomyopathy Demonstrated by Magnetic Resonance Imaging and Single Photon Emission Computed Tomography Dual-Isotope Scintigraphy

41-year-old man, who had been diagnosed with stage 2 pulmonary sarcoidosis 3 years earlier, was referred to the cardiac clinic complaining of palpitations, dyspnea, and atypical chest pain. Except for central obesity (body mass index of 37 kg/m 2 ) and hypertension, no abnormalities were found on physical examination. The 12-lead ECG demonstrated apical and inferolateral ST-segment elevation, whereas multiple polymorphic premature ventricular beats were found during exercise testing and 24-hour ambulatory ECG. Coronary angiography showed no abnormalities. Because of the man’s obesity, the image quality of the transthoracic echocardiography was suboptimal. Cardiac MRI revealed severe asymmetric hypertrophy of the left ventricle, a finding that points to hypertrophic cardiomyopathy. T2-weighted cardiac MRI revealed increased signal in the apical region (Figure 1), and contrast-enhanced cardiac MRI (0.1 mmol/kg gadolinium-diethylenetriamine pentaacetic acid [Gd-DTPA]) showed late enhancement of the same region (Figures 2 through 5). A dual-isotope 99m Tc-Hexamibi (Cardiolite, DuPont) and 111 In-pentetreotide (OctreoScan, Tyco Healthcare, Mallinckrodt Medical BV; dose 190 MBq) SPECT was performed during exercise (dose 280 MBq) and rest (dose 870 MBq), revealing a reversible apical perfusion defect and apical uptake of 111 Inpentetreotide (Figure 6). The presence of somatostatin receptors in the apical region suggests active apical cardiac sarcoidosis. The SPECT and cardiac MRI images were fused (Figures 7 and 8) by rigid-body transformations based on anatomic landmarks (apex and basal interventricular septum) and the geometric dimensions identified in the different types of images. The spatial image transformations were computed in the MatLab (MathWorks) programming environment. 111 Inpentetreotide binds to somatostatin receptors on macrophages and has been reported to be useful in the management of sarcoidosis. It is possible to differentiate between active inflammation and fibrosis with different cardiac MRI techniques (eg, T2-weighted versus contrast-enhanced T1weighted cardiac MRI). This case demonstrates the usefulness of matching different imaging techniques to visualize inflammation and the different stages of this process in the myocardium.

Novel revascularization therapies--TMLR and growth factor-induced angiogenesis monitored with cardiac MRI.

Employment of cardiac MRI techniques (cine MRI, wall thickening analysis, quantitative MRFPP, MR tissue tagging) allowed non-invasive localization and assessment of early and late changes in myocardial function and perfusion produced by these new approaches of myocardial revascularization. With its precision in assessment of myocardial perfusion and collateral-dependent territories, cardiac MRI techniques may be of excellent use for the evaluation of effects on myocardial function and perfusion as well as longitudinal outcomes in clinical trials with TMLR and angiogenesis therapies in patients with CAD. As growth factor therapies approach phase III clinical trials, such vital questions as the most effective delivery system, dosages and techniques used for treatment-monitoring parameters remain unanswered. In addition, better definitions of patient selection criteria for TMLR and angiogenesis therapies for both short- and long-term maximum benefits are needed at this time. Large-scale clinical trials with cardiac MRI techniques are needed to reliably assess functional and perfusion reserves of the myocardium pre and post TMLR and angiogenesis therapies. MR-based outcome parameters may aid in answering questions pertinent to the new revascularization treatments.

MRI techniques for cardiovascular imaging.

Over the last several years, cardiovascular MRI has benefited from a number of technical advances which have improved routine clinical imaging techniques. As a result, MRI is now well positioned to realize its longstanding promise of becoming the comprehensive cardiac imaging test of choice in many clinical settings. This may be achieved using a combination of basic advanced techniques. In this overview, the basic cardiac MRI techniques which are clinically useful are reviewed, and the recent technical advances which are clinically promising are described. These advances include routine black blood and cine bright blood techniques that are high speed (<10s per black blood image or cine slice), multislice whole heart perfusion imaging methods, and recently emerging real-time imaging methodologies. J Magn. Reson. Imaging 1999;10:590-601.