Myocardial T1 mapping: techniques and potential applications

Peripheral microvascular function is linked to cardiac involvement on cardiovascular magnetic resonance in systemic sclerosis-related pulmonary arterial hypertension

AIMS

Systemic sclerosis (SSc) is characterized by vasculopathy, inflammation, and fibrosis, and carries one of the worst prognoses if patients also develop pulmonary arterial hypertension (PAH). Although PAH is a known prognosticator, patients with SSc-PAH demonstrate disproportionately high mortality, presumably due to cardiac involvement. In this cross-sectional study, the relationship between cardiac involvement revealed by cardiovascular magnetic resonance (CMR) and systemic microvascular disease severity measured with nailfold capillaromicroscopy (NCM) in patients with SSc-PAH is evaluated and compared with patients with idiopathic PAH (IPAH).

METHODS AND RESULTS

Patients with SSc-PAH and IPAH underwent CMR, echocardiography, and NCM with post-occlusive reactivity hyperaemia (PORH) testing on the same day. CMR imaging included T2 (oedema), native, and post-contrast T1 mapping to measure the extracellular volume fraction (ECV, fibrosis) and adenosine-stress-perfusion imaging measuring the relative myocardial upslope (microvascular coronary perfusion). Measures of peripheral microvascular function were related to CMR indices of oedema, fibrosis, and myocardial perfusion. SSc-PAH patients (n = 20) had higher T2 values and a trend towards a higher ECV, compared with IPAH patients (n = 5), and a lower nailfold capillary density (NCD) and reduced capillary recruitment after PORH. NCD correlated with ECV and T2 (r = -0.443 and -0.464, respectively, P < 0.05 for both) and with markers of diastolic dysfunction on echocardiography. PORH testing, but not NCD, correlated with the relative myocardial upslope (r = 0.421, P < 0.05).

CONCLUSION

SSc-PAH patients showed higher markers of cardiac fibrosis and inflammation, compared with IPAH patients. These markers correlated well with peripheral microvascular dysfunction, suggesting that SSc-driven inflammation and vasculopathy concurrently affect peripheral microcirculation and the heart. This may contribute to the disproportionate high mortality in SSc-PAH.

Distinguishing heart failure subtypes: the diagnostic power of different cardiac magnetic resonance imaging parameters

Objectives

The aim of this retrospective study was to explore the diagnostic potential of various cardiac parameters in differentiating between heart failure with preserved ejection fraction (HFpEF) and heart failure with mid-ranged and reduced ejection fraction (HFm + rEF), and to discern their relationship with normal cardiac function.

Methods

This research encompassed a comparative analysis of heart failure subtypes based on multiple indicators. Participants were categorized into HFm + rEF, HFpEF, and control groups. For each participant, we investigated indicators of left ventricular function (LVEDVi, LVESVi, and LVEF) and myocardial strain parameters (GLS, GCS, GRS). Additionally, quantitative tissue evaluation parameters including native T1, enhanced T1, and extracellular volume (ECV) were examined.For comprehensive diagnostic performance analysis, receiver operating characteristic (ROC) curve evaluations for each parameters were conducted.

Results

HFm + rEF patients exhibited elevated LVEDVi and LVESVi and decreased LVEF compared to both HFpEF and control groups. Myocardial strain revealed significant reductions in GLS, GCS, and GRS for HFm + rEF patients compared to the other groups. HFpEF patients showed strain reductions relative to the control group. In cardiac magnetic resonance imaging (CMR) evaluations, HFm + rEF patients demonstrated heightened native T1 times and ECV fractions. Native T1 was particularly effective in distinguishing HFpEF from healthy subjects.

Conclusion

Native T1, ECV, and myocardial strain parameters have substantial diagnostic value in identifying HFpEF. Among them, native T1 displayed superior diagnostic efficiency relative to ECV, offering critical insights into early-stage HFpEF. These findings can play a pivotal role in refining clinical management and treatment strategies for heart failure patients.

Inter-scanner comparability of Z-scores for native myocardial T1 and T2 mapping

BACKGROUND

Cardiovascular Magnetic Resonance (CMR) native T1 and T2 mapping serve as robust, contrast-agent-free diagnostic tools, but hardware- and software-specific sources of variability limit the generalizability of data across CMR platforms, consequently limiting the interpretability of patient-specific parametric data. Z-scores are used to describe the relationship of observed values to the mean results as obtained in a sufficiently large normal sample. They have been successfully used to describe the severity of quantifiable abnormalities in medicine, specifically in children and adolescents. The objective of this study was to observe whether z-scores can improve the comparability of T1 and T2 mapping values across CMR scanners, field strengths, and sequences from different vendors in the same participant rather than different participants (as seen in previous studies).

METHODS

Fifty-one healthy volunteers (26 men/25 women, mean age = 43 ± 13.51) underwent three CMR exams on three different scanners, using a Modified Look-Locker Inversion Recovery (MOLLI) 5-(3)- 3 sequence to quantify myocardial T1. For T2 mapping, a True Fast Imaging with steady-state free precession (TRUFI) sequence was used on a 3 T Skyra™ (Siemens), and a T2 Fast Spin Echo (FSE) sequence was used on 1.5 T Artist™ (GE) and 3.0 T Premier™ (GE) scanners. The averages of basal and mid-ventricular short axis slices were used to derive means and standard deviations of global mapping values. We used intra-class comparisons (ICC), repeated measures ANOVA, and paired Student's t-tests for statistical analyses.

RESULTS

There was a significant improvement in intra-subject comparability of T1 (ICC of 0.11 (95% CI= -0.018, -0.332) vs 0.78 (95% CI= 0.650, 0.866)) and T2 (ICC of 0.35 (95% CI= -0.053, 0.652) vs 0.83 (95% CI= 0.726, 0.898)) when using z-scores across all three scanners. While the absolute global T1 and T2 values showed a statistically significant difference between scanners (p < 0.001), no such differences were identified using z-scores (T1z: p = 0.771; T2z: p = 0.985). Furthermore, when images were not corrected for motion, T1 z-scores showed significant inter-scanner variability (p < 0.001), resolved by motion correction.

CONCLUSION

Employing z-scores for reporting myocardial T1 and T2 removes the variation of quantitative mapping results across different MRI systems and field strengths, improving the clinical utility of myocardial tissue characterization in patients with suspected myocardial disease.

Quantitative myocardial T2 mapping adds value to Japanese circulation society diagnostic criteria for active cardiac sarcoidosis

Noninvasive identification of active myocardial inflammation in patients with cardiac sarcoidosis plays a key role in management but remains elusive. T2 mapping is a proposed solution, but the added value of quantitative myocardial T2 mapping for active cardiac sarcoidosis is unknown. Retrospective cohort analysis of 56 sequential patients with biopsy-confirmed extracardiac sarcoidosis who underwent cardiac MRI for myocardial T2 mapping. The presence or absence of active myocardial inflammation in patients with CS was defined using a modified Japanese circulation society criteria within one month of MRI. Myocardial T2 values were obtained for the 16 standard American Heart Association left ventricular segments. The best model was selected using logistic regression. Receiver operating characteristic curves and dominance analysis were used to evaluate the diagnostic performance and variable importance. Of the 56 sarcoidosis patients included, 14 met criteria for active myocardial inflammation. Mean basal T2 value was the best performing model for the diagnosis of active myocardial inflammation in CS patients (pR2 = 0.493, AUC = 0.918, 95% CI 0.835-1). Mean basal T2 value > 50.8 ms was the most accurate threshold (accuracy = 0.911). Mean basal T2 value + JCS criteria was significantly more accurate than JCS criteria alone (AUC = 0.981 vs. 0.887, p = 0.017). Quantitative regional T2 values are independent predictors of active myocardial inflammation in CS and may add additional discriminatory capability to JCS criteria for active disease.

Diagnostic Role of Native T1 Mapping Compared to Conventional Magnetic Resonance Techniques in Cardiac Disease in a Real-Life Cohort

We sought to compare native T1 mapping to conventional late gadolinium enhancement (LGE) and T2-STIR techniques in a cohort of consecutive patients undergoing cardiac MRI (CMR). CMR was performed in 323 patients, 206 males (64%), mean age 54 ± 8 years, and in 27 age- and sex- matched healthy controls. In T2-STIR images, myocardial hyperintensity suggesting edema was found in 41 patients (27%). LGE images were positive in 206 patients (64%). T1 mapping was abnormal in 171 (49%). In 206 patients (64%), a matching between LGE and native T1 was found. T1 was abnormal in 32 out of 41 (78%) with edema in T2-STIR images. Overall, LGE and/or T2-STIR were abnormal in 209 patients, whereas native T1 was abnormal in 154 (52%). Conventional techniques and T1 mapping were concordant in 208 patients (64%). In 39 patients, T1 mapping was positive despite negative conventional techniques (12%). T1 mapping was able in conditions with diffuse myocardial damage such as cardiac amyloidosis, scleroderma, and Fabry disease (additive role in 42%). In contrast, T1 mapping was less effective in cardiac disease with regional distribution of myocardial damage such as myocardial infarction, HCM, and myocarditis. In conclusion, conventional LGE/T2-STIR and T1 mapping are complementary techniques and should be used together in every CMR examination.

Simultaneous multi-slice T1 mapping using MOLLI with blipped CAIPIRINHA bSSFP

BACKGROUND

This study evaluates the possibility for replacing conventional 3 slices, 3 breath-holds MOLLI cardiac T1 mapping with single breath-hold 3 simultaneous multi-slice (SMS3) T1 mapping using blipped-CAIPIRINHA SMS-bSSFP MOLLI sequence. As a major drawback, SMS-bSSFP presents unique artefacts arising from side-lobe slice excitations that are explained by imperfect RF modulation rendering and bSSFP low flip angle enhancement. Amplitude-only RF modulation (AM) is proposed to reduce these artefacts in SMS-MOLLI compared to conventional Wong multi-band RF modulation (WM).

MATERIALS AND METHODS

Phantoms and ten healthy volunteers were imaged at 1.5 T using a modified blipped-CAIPIRINHA SMS-bSSFP MOLLI sequence with 3 simultaneous slices. WM-SMS3 and AM-SMS3 were compared to conventional single-slice (SMS1) MOLLI. First, SNR degradation and T1 accuracy were measured in phantoms. Second, artefacts from side-lobe excitations were evaluated in a phantom designed to reproduce fat presence near the heart. Third, the occurrence of these artefacts was observed in volunteers, and their impact on T1 quantification was compared between WM-SMS3 and AM-SMS3 with conventional MOLLI as a reference.

RESULTS

In the phantom, larger slice gaps and slice thicknesses yielded higher SNR. There was no significant difference of T1 values between conventional MOLLI and SMS3-MOLLI (both WM and AM). Positive banding artefacts were identified from fat neighbouring the targeted FOV due to side-lobe excitations from WM and the unique bSSFP signal profile. AM RF pulses reduced these artefacts by 38%. In healthy volunteers, AM-SMS3-MOLLI showed similar artefact reduction compared to WM-SMS3-MOLLI (3 ± 2 vs 5 ± 3 corrupted LV segments out of 16). In-vivo native T1 values obtained from conventional MOLLI and AM-SMS3-MOLLI were equivalent in LV myocardium (SMS1-T1 = 935.5 ± 36.1 ms; AM-SMS3-T1 = 933.8 ± 50.2 ms; P = 0.436) and LV blood pool (SMS1-T1 = 1475.4 ± 35.9 ms; AM-SMS3-T1 = 1452.5 ± 70.3 ms; P = 0.515). Identically, no differences were found between SMS1 and SMS3 postcontrast T1 values in the myocardium (SMS1-T1 = 556.0 ± 19.7 ms; SMS3-T1 = 521.3 ± 28.1 ms; P = 0.626) and the blood (SMS1-T1 = 478 ± 65.1 ms; AM-SMS3-T1 = 447.8 ± 81.5; P = 0.085).

CONCLUSIONS

Compared to WM RF modulation, AM SMS-bSSFP MOLLI was able to reduce side-lobe artefacts considerably, providing promising results to image the three levels of the heart in a single breath hold. However, few artefacts remained even using AM-SMS-bSSFP due to residual RF imperfections. The proposed blipped-CAIPIRINHA MOLLI T1 mapping sequence provides accurate in vivo T1 quantification in line with those obtained with a single slice acquisition.

Non-LGE Cardiac Magnetic Resonance Imaging in Patients with Cardiac Amyloidosis

Cardiac involvement is the leading cause of death in patients with cardiac amyloidosis. Early recognition is crucial as it can significantly change the course of the disease. Until now, the imaging modality of choice for diagnosing cardiac amyloidosis has been cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE). LGE-CMR in patients with cardiac amyloidosis reveals characteristic LGE patterns that lead to a diagnosis while also correlating well with disease prognosis. However, LGE-CMR has numerous drawbacks that the newer CMR modality, T1 mapping, aims to improve. T1 mapping can be further subdivided into native T1 mapping, which does not require the use of contrast, and ECV measurement, which requires the use of contrast. Numerous T1 mapping techniques have been developed, each one with its own advantages and disadvantages when it comes to procedure difficulty and image quality. A literature review to identify relevant published articles was performed by two authors. This review aimed to present the value of T1 mapping in diagnosing cardiac amyloidosis, quantifying the amyloid burden, and evaluating the prognosis of patients with amyloidosis with cardiac involvement.

Multimodality Imaging in the Diagnosis and Assessment of Cardiac Amyloidosis

Amyloidosis is a rare disorder where abnormal protein aggregates are deposited in tissues forming amyloid fibrils, leading to progressive organ failure. Although any organ can be affected, cardiac involvement is the main cause of morbidity and mortality associated with amyloidosis as diagnosis is often delayed due to the indolent nature of the disease in some forms. An early diagnosis of disease and knowledge of the type/subtype of cardiac amyloidosis (CA) are essential for appropriate management and better outcome. Echocardiography is often the first line of investigation for patients suspected of CA and offers superior hemodynamic assessment. Although cardiovascular magnetic resonance (CMR) imaging is not diagnostic of CA, it provides vital clues to diagnosis and has a role in disease quantification and prognostication. Radiolabeled bone seeking tracers are the mainstay of diagnosis of CA and when combined with screening of monoclonal light chains, bone scintigraphy offers high sensitivity in diagnosing transthyretin type of CA. This review aims to describe the noninvasive imaging assessment and approach to diagnosis of patients with suspected CA. Imaging features of echocardiography, nuclear scintigraphy, and CMR are described with a brief mention on computed tomography.

Role of Cardiac MRI Including LGE, T1 and T2 Mapping in the Assessment of Cardiac Involvement in Patients of Nonspecific Aorto-arteritis: A Prospective Study

Objective Nonspecific aorto-arteritis (NSAA) may involve the myocardium in the form of edema and fibrosis. We conducted this study to investigate role of cardiac MRI including late gadolinium enhancement (LGE), T1 and T2 mapping in the assessment of cardiac involvement in NSAA.

Methods and Materials Over the period between 2016 and 2019, 36 patients with NSAA presenting with uncontrolled hypertension, left ventricular dysfunction, congestive cardiac failure, or tachyarrhythmia were included in the study. We also had 16 voluntary control patients for providing normal T1 and T2 mapping values.

Results The average age of patients was 27.1 years and the majority were females. MRI is more sensitive than echocardiography in the detection of LV dysfunction and RWMA. Out of 36 patients, 10 (27.8%) had LGE. The most common pattern of midmyocardial enhancement was present in 5 out of 10 patients. Five (13.8%) patients show mid-myocardial enhancement, followed by epicardial enhancement, which was seen in four (11.11%) patients. The values of post-gad T1 mapping values were significantly lower than pre-gad T1 mapping values. At a cut-off global native T1 mapping value of 1019 milliseconds had the sensitivity of 83.3% and specificity of 81.2% in detecting an abnormal T1 map. No significant association of MRI contrast enhancement with elevated ESR and CRP levels. There was no significant relation of myocardial T2 mapping values between NSAA and control groups.

Conclusion Quantitative tissue characterization in the myocardium with native T1 mapping values help in the detection of cardiac involvement in patients with NSAA. T1 mapping may provide incremental value in the assessment of myocardial involvement in NSAA in addition to LGE imaging.

Piezo1 Channel as a Potential Target for Hindering Cardiac Fibrotic Remodeling

Fibrotic tissues share many common features with neoplasms where there is an increased stiffness of the extracellular matrix (ECM). In this review, we present recent discoveries related to the role of the mechanosensitive ion channel Piezo1 in several diseases, especially in regulating tumor progression, and how this can be compared with cardiac mechanobiology. Based on recent findings, Piezo1 could be upregulated in cardiac fibroblasts as a consequence of the mechanical stress and pro-inflammatory stimuli that occurs after myocardial injury, and its increased activity could be responsible for a positive feedback loop that leads to fibrosis progression. The increased Piezo1-mediated calcium flow may play an important role in cytoskeleton reorganization since it induces actin stress fibers formation, a well-known characteristic of fibroblast transdifferentiation into the activated myofibroblast. Moreover, Piezo1 activity stimulates ECM and cytokines production, which in turn promotes the phenoconversion of adjacent fibroblasts into new myofibroblasts, enhancing the invasive character. Thus, by assuming the Piezo1 involvement in the activation of intrinsic fibroblasts, recruitment of new myofibroblasts, and uncontrolled excessive ECM production, a new approach to blocking the fibrotic progression can be predicted. Therefore, targeted therapies against Piezo1 could also be beneficial for cardiac fibrosis.

Compact pediatric cardiac magnetic resonance imaging protocols

Cardiac MRI is in many respects an ideal modality for pediatric cardiovascular imaging, enabling a complete noninvasive assessment of anatomy, morphology, function and flow in one radiation-free and potentially non-contrast exam. Nonetheless, traditionally lengthy and complex imaging acquisition strategies have often limited its broader use beyond specialized centers. In this review, the author presents practical cardiac MRI imaging protocols to facilitate the performance of succinct yet successful exams that provide the most salient clinical data for the majority of congenital and acquired pediatric cardiac disease. In addition, the author reviews newer and evolving techniques that permit more rapid but similarly diagnostic MRI, including compressed sensing and artificial intelligence/machine learning reconstruction, four-dimensional flow acquisition and blood pool contrast agents. With the modern armamentarium of cardiac MRI methods, the goal of compact yet comprehensive exams in children can now be realized.

Liver T1 relaxation time of the 'normal liver' in healthy Asians: measurement with MOLLI and B1-corrected VFA methods at 3T

OBJECTIVES

Liver T1 is a potential magnetic resonance imaging biomarker for liver diseases. This study aimed to determine the T1 relaxation time of the normal liver (PDFF<5%) in healthy Asian volunteers using modified look-locker inversion recovery (MOLLI) and B1 inhomogeneity-corrected variable flip angle (B1-corrected VFA).

METHODS

60 healthy Asian volunteers without focal or diffuse liver disease underwent a liver scan at 3T magnetic resonance. Proton density fat fraction (PDFF) and liver stiffness measurements were applied for the quantification of liver fat and fibrosis. T1 mapping was performed with MOLLI and B1-corrected VFA sequences. Bland-Altman, linear regression, Student t-test, and one-way analysis of variance were used for statistical analysis.

RESULTS

The mean T1 relaxation times of the whole liver were 901 ± 34 ms by MOLLI, and 948 ± 29 ms by B1-corrected VFA in healthy volunteers. There was a strong correlation (r = 0.86, p < 0.0001) for liver T1 between two T1 mapping methods. There were significant differences between the right and left lobes in liver T1 relaxation times using both methods (p < 0.05). Gender and Asian ethnic disparities had no impact on liver T1 relaxation times.

CONCLUSION

T1 relaxation times of the normal liver (PDFF<5%) in healthy volunteers were established by MOLLI and B1-corrected VFA T1 mapping methods at 3T. It may provide suitable and robust baseline values for the assessment of liver diseases.

ADVANCES IN KNOWLEDGE

Gender and Asian ethnic disparities do not impact liver T1 relaxation time measurements.

Creating Interactive Three-Dimensional Applications to Visualise Novel Stent Grafts That Aid in the Treatment of Aortic Aneurysms

Three-Dimensional (3D) medical animations incorporated into applications are highly beneficial for clinical outreach and medical communication purposes that work towards educating the clinician and patient. Aortic aneurysms are a clinically important area to communicate with multiple audiences about various treatment options; both abdominal and thoracic aortic aneurysms were selected to create 3D animations and applications to educate medical professionals and patients regarding treatment options. Fenestrated endovascular aortic repair (FEVAR) and thoracic endovascular aortic repair (TEVAR) are both tried and tested minimally invasive surgical methods for treating thoracic aortic aneurysms respectively. The Terumo Aortic Custom Relay Proximal Scalloped stent graft and Fenestrated Anaconda stent graft were both designed specifically for these procedures; however, it can be difficult to visually communicate to clinicians and patients in a straightforward way how these devices work. Therefore, we have developed two interactive applications that use 3D visualisation techniques to demonstrate how these aortic devices function and are implemented. The objective of these applications is to engage both clinicians and patients, therefore demonstrating that the addition of anatomically accurate 3D visualisations within an interactive interface would have a positive impact on public engagement while also ensuring that clinicians will have the best possible understanding of the potential uses of both devices, enabling them to exploit their key features to effectively broaden the treatable patient population.Detailed anatomical modelling and animation was used to generate realistic and accurate rendered videos showcasing both products. These videos were integrated into an interactive application within a modern, professional graphic interface that allowed the user to explore all aspects of the stent device. The resulting applications were broken down into three modules: deployment, clinical performance and features. Following application development, these applications were evaluated by professionals in the field. Overall, positive feedback was received regarding the user-friendly nature of the applications and highly effective animations to showcase the products. The clinical applications and feature modules were particularly successful, while the deployment modules had a neutral response. Biomedical applications such as these show great potential for communicating the key features of medical devices and promoting discussion between clinicians and patients; further testing would need to be conducted on a larger group of participants in order to validate the learning effectiveness of the applications.

Arrhythmogenic cardiomyopathy: pathogenesis, pro-arrhythmic remodelling, and novel approaches for risk stratification and therapy

Arrhythmogenic cardiomyopathy (ACM) is a life-threatening cardiac disease caused by mutations in genes predominantly encoding for desmosomal proteins that lead to alterations in the molecular composition of the intercalated disc. ACM is characterized by progressive replacement of cardiomyocytes by fibrofatty tissue, ventricular dilatation, cardiac dysfunction, and heart failure but mostly dominated by the occurrence of life-threatening arrhythmias and sudden cardiac death (SCD). As SCD appears mostly in apparently healthy young individuals, there is a demand for better risk stratification of suspected ACM mutation carriers. Moreover, disease severity, progression, and outcome are highly variable in patients with ACM. In this review, we discuss the aetiology of ACM with a focus on pro-arrhythmic disease mechanisms in the early concealed phase of the disease. We summarize potential new biomarkers which might be useful for risk stratification and prediction of disease course. Finally, we explore novel therapeutic strategies to prevent arrhythmias and SCD in the early stages of ACM.

Influence of Fibrosis Amount and Patterns on Ventricular Arrhythmogenesis and Pumping Efficacy: Computational Study

Myocardial fibrosis is an integral component of most forms of heart failure. Clinical and computational studies have reported that spatial fibrosis pattern and fibrosis amount play a significant role in ventricular arrhythmogenicity. This study investigated the effect of the spatial distribution of fibrosis and fibrosis amount on the electrophysiology and mechanical performance of the human ventricles. Seventy-five fibrosis distributions comprising diffuse, patchy, and compact fibrosis types that contain 10-50% fibrosis amount were generated. The spatial fibrosis distribution was quantified using the fibrosis entropy (FE) metric. Electrical simulations under reentry conditions induced using the S1-S2 protocol were conducted to investigate the fibrosis arrhythmogenicity. We also performed mechanical simulations to examine the influence of the fibrosis amount and the spatial distribution of fibrosis on the pumping efficacy of the LV. We observed that the mean FE of the compact type is the largest among the three types. The electrical simulation results revealed that the ventricular arrhythmogenicity of diffuse fibrosis depends on the fibrosis amount and marginally on the spatial distribution of fibrosis. Meanwhile, the ventricular arrhythmogenicity of the compact and patchy fibrosis pattern is more reliant on the spatial distribution of fibrosis than on the fibrosis amount. The average number of phase singularities (PSs) in the compact fibrosis pattern was the highest among the three patterns of fibrosis. The diffuse type of fibrosis has the lowest average number of PSs than that in the patchy and compact fibrosis. The reduction in the stroke volume (SV) showed high influence from the electrical instabilities induced by the fibrosis amount and pattern. The compact fibrosis exhibited the lowest SV among the three patterns except in the 40% fibrosis amount. In conclusion, the fibrosis pattern is as crucial as the fibrosis amount for sustaining and aggravating ventricular arrhythmogenesis.

Multimodality Imaging Assessment of Myocardial Fibrosis

Myocardial fibrosis, seen in ischemic and nonischemic cardiomyopathies, is associated with adverse cardiac outcomes. Noninvasive imaging plays a key role in early identification and quantification of myocardial fibrosis with the use of an expanding array of techniques including cardiac magnetic resonance, computed tomography, and nuclear imaging. This review discusses currently available noninvasive imaging techniques, provides insights into their strengths and limitations, and examines novel developments that will affect the future of noninvasive imaging of myocardial fibrosis.

Comparison Between Time-Resolved Magnetic Resonance Angiography and Diagnostic Digital Subtraction Angiography in the Vascular Assessment of Nonspecific Aorto-Arteritis Patients: A Prospective Study

PURPOSE

Nonspecific aortoarteritis (NSAA) is a chronic inflammatory vasculitis involving aorta and its branches. We conducted a study prospectively to compare time resolved magnetic resonance angiography (MRA) with diagnostic digital subtraction angiography (DSA) for the vascular assessment in the patients of NSAA.

MATERIALS AND METHODS

Seventeen patients of NSAA were recruited in the study over the period of 3 years. Contrast enhanced MRA using Time-resolved angiography With Interleaved Stochastic Trajectories (TWIST) sequence and diagnostic DSA were performed in these 17 patients.

RESULTS

The majority of the patients were young (median age was 25 years, range 8 to 46 years) and 11 patients were females. Erythrocyte sedimentation rate (ESR) was elevated in 9 patients and C-reactive protein (CRP) was elevated in 6 patients. Most commonly involved vessels in our patients were right renal artery (14 patients), abdominal aorta (12 patients) and left renal artery (11 patients). Left and right subclavian arteres were involved in 10 and 6 patients respectively. The sensitivity and specificity of time-resolved MRA using TWIST sequence is 100% as compared to DSA in the assessment of major vessels such as aorta, arch vessels, celiac artery and superior mesenteric artery. However, the sensitivity and specificity of time resolved MRA in the evaluation of renal arteries and vertebral arteries were 100%, 71.4% and 85.7%, 33.3% respectively. No significant association of MRI contrast enhancement with erythrocyte sedimentation rate (p = 1.00) and C-reactive protein (p = 0.600).

CONCLUSION

Time resolved MRA images obtained using TWIST sequence were as qualitative as DSA images and can noninvasively evaluate the vascular involvement in NSAA patients.

The diagnostic value of non-contrast magnetic resonance coronary angiography in the assessment of coronary artery disease: A systematic review and meta-analysis

Purpose

The current literature reports a wide range of diagnostic accuracy of non-contrast magnetic resonance coronary angiography (NC-MRCA) for the assessment of coronary artery disease (CAD). We aimed to compare the clinical effectiveness of NC-MRCA with that of invasive coronary angiography (ICA) in patients with suspected CAD using a systematic review and meta-analysis.

Methods

Two investigators independently extracted 36 published manuscripts between 2010 and 2019. Databases including Medline, Web of Knowledge, Google Scholar, Scopus, and Cochrane were searched using pre-established keywords. Analysis of the data followed the PRISMA statement for reporting systematic reviews and meta-analyses and primary analysis followed the Mantel-Hansel methodology. Correctness of classification for detecting coronary artery stenosis ≥50% (CAS) was measured using ICA as the gold standard.

Results

A total of five studies met inclusion criteria, with a total of 417 patients and 2883 coronary segments. The pooled per patient sensitivity and specificity of NC-MRCA for CAS in suspected patients was 90.3% (95% CI 85.6–95.1%) and 77.9% (95% CI 69.5–86.3%). Pooled per vessel assessment of NC- MRCA revealed a sensitivity of 83.7% (95%CI 79.7–87.8%) and specificity of 90.0% (95%CI 86.7–93.4%). Per-segment assessment of NC-MRCA showed a pooled sensitivity of 81.6% (95% CI 76.8–86.4) and specificity of 97.0% (95% CI 95.5–98.5). Mild to moderate heterogeneity was noted in most diagnostic parameters with larger heterogeneity noted in the per-segment analyses. There was less heterogeneity in sensitivity and NPV than specificity and PPV.

Conclusion

According to this meta-analysis, non-contrast coronary MRA resulted in adequate screening in patients with suspected CAD with high sensitivity and specificity. This result was true for per-patient, per-vessel, and per-segment assessment.

The association of secondary hyperparathyroidism and myocardial damages in hemodialysis end-stage renal disease patients: assessed by cardiovascular magnetic resonance native T1 mapping

BACKGROUND

Secondary hyperparathyroidism is a common complication of end-stage renal disease (ESRD), which may be associated with cardiovascular diseases. Thus, this study aimed to explore myocardial damage using non-contrast cardiovascular magnetic resonance (CMR) in ESRD patients undergoing hemodialysis and further investigate its relationship with parathyroid hormone (PTH) toxicity.

METHODS

Seventy-two adult ESRD patients receiving regular hemodialysis and 30 healthy subjects underwent CMR examination. Continuous CMR cine sections from the mitral valve level to the left ventricular (LV) apex in the short-axis plane, cine series of vertical two-chamber long-axis plane, and horizontal four-chamber plane were acquired. Native T1 mapping was obtained using modified Look-Locker inversion recovery (MOLLI) sequences. Native T1 values and myocardial strain were analyzed.  Immunoreactive parathyroid hormone (iPTH) was obtained from all enrolled patients.

RESULTS

Forty (55.6%) hemodialysis ESRD patients were found to have increased iPTH levels. LV ejection fraction (LVEF) of both ESRD patients with targeted and increased iPTH levels was decreased compared with healthy subjects (55.9 ± 12.0% vs. 65.0 ± 4.5%; 51.7 ± 12.8 vs. 65.0 ± 4.5%, both P < 0.05). The mean peak radial strain (PRS), peak circumferential strain (PCS), and peak longitudinal strain (PLS) were lowest in ESRD patients with increased iPTH; however, no significant difference was observed among these three groups. Segmentally, from base to apex, the native T1 of ESRD patients with increased iPTH levels tended to be higher than those with targeted iPTH and healthy subjects (all P < 0.05). In ESRD patients with targeted iPTH, both native T1 of basal and middle segments were significantly higher than normal subjects (basal, 1304 ± 41 ms vs. 1238 ± 36 ms, P = 0.001; middle, 1300 ± 43 ms vs. 1242 ± 50 ms, P < 0.001). Comparing global native T1 values in the three groups, ESRD patients with targeted and increased iPTH level showed increased native T1 (1305 ± 41 ms vs. 1251 ± 49 ms, P = 0.001; 1334 ± 40 ms vs. 1251 ± 49 ms, P < 0.001, respectively). Native T1 values of the basal segment and global native T1 were moderately associated with iPTH (r = 0.4, P < 0.001; r = 0.5, P < 0.001). Multiple linear regression analysis showed that global native T1 values (beta = 1.0, P = 0.01) were independently associated with iPTH.

CONCLUSIONS

Elevated iPTH level was associated with and was an independent risk factor for myocardial damage in ESRD patients undergoing maintenance hemodialysis.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn/index.aspx ) ChiCTR-DND-17012976, 13/12/2017, retrospectively registered.

CT and MR Imaging Findings of Structural Heart Diseases Associated with Sudden Cardiac Death

급성 심장사는 증상이 시작된 후 한 시간 이내에 발생하는 심장 원인으로 인한 사망이다. 급성 심장사의 원인은 주로 부정맥이지만 동반할 수 있는 기저 심질환들을 사전에 진단하는 것은 장기적 위험을 예측하는 데 중요하다. 심장 CT와 심장 MR은 구조적 심질환을 진단하고 평가하는데 중요한 정보를 제공하여 급성 심장사의 위험을 예측하고 대비할 수 있게 한다. 따라서 임상적으로 중요한 급성 심장사의 위험을 증가시키는 다양한 원인과 영상 소견의 중요성에 대하여 중점적으로 살펴보고자 한다.

Evaluation of fully automated myocardial segmentation techniques in native and contrast-enhanced T1-mapping cardiovascular magnetic resonance images using fully convolutional neural networks

PURPOSE

T1-mapping cardiac magnetic resonance (CMR) imaging permits noninvasive quantification of myocardial fibrosis (MF); however, manual delineation of myocardial boundaries is time-consuming and introduces user-dependent variability for such measurements. In this study, we compare several automated pipelines for myocardial segmentation of the left ventricle (LV) in native and contrast-enhanced T1-maps using fully convolutional neural networks (CNNs).

METHODS

Sixty patients with known MF across three distinct cardiomyopathy states (20 ischemic (ICM), 20 dilated (DCM), and 20 hypertrophic (HCM)) underwent a standard CMR imaging protocol inclusive of cinematic (CINE), late gadolinium enhancement (LGE), and pre/post-contrast T1 imaging. Native and contrast-enhanced T1-mapping was performed using a shortened modified Look-Locker imaging (shMOLLI) technique at the basal, mid-level, and/or apex of the LV. Myocardial segmentations in native and post-contrast T1-maps were performed using three state-of-the-art CNN-based methods: standard U-Net, densely connected neural networks (Dense Nets), and attention networks (Attention Nets) after dividing the dataset using fivefold cross validation. These direct segmentation techniques were compared to an alternative registration-based segmentation method, wherein spatially corresponding CINE images are segmented automatically using U-Net, and a nonrigid registration technique transforms and propagates CINE contours to the myocardial regions of T1-maps. The methodologies were validated in 125 native and 100 contrast-enhanced T1-maps using standard segmentation accuracy metrics. Pearson correlation coefficient r and Bland-Altman analysis were used to compare the computed global T1 values derived by manual, U-Net, and CINE registration methodologies.

RESULTS

The U-Net-based method yielded optimal results in myocardial segmentation of native, contrast-enhanced, and CINE images compared to Dense Nets and Attention Nets. The direct U-Net-based method outperformed the CINE registration-based method in native T1-maps, yielding Dice similarity coefficient (DSC) of 82.7 ± 12% compared to 81.4 ± 6.9% (P < 0.0001). However, in contrast-enhanced T1-maps, the CINE-registration-based method outperformed direct U-Net segmentation, yielding DSC of 77.0 ± 9.6% vs 74.2 ± 18% across all patient groups (P = 0.0014) and specifically 73.2 ± 7.3% vs 65.5 ± 18% in the ICM patient group. High linear correlation of global T1 values was demonstrated in Pearson analysis of the U-Net-based technique and the CINE-registration technique in both native T1-maps (r = 0.93, P < 0.0001 and r = 0.87, P < 0.0001, respectively) and contrast-enhanced T1-maps (r = 0.93, P < 0.0001 and r = 0.98, P < 0.0001, respectively).

CONCLUSIONS

The direct U-Net-based myocardial segmentation technique provided accurate, fully automated segmentations in native and contrast-enhanced T1-maps. Myocardial borders can alternatively be segmented from spatially matched CINE images and applied to T1-maps via deformation and propagation through a modality-independent neighborhood descriptor (MIND). The direct U-Net approach is more efficient in myocardial segmentation of native T1-maps and eliminates cross-technique dependence. However, the CINE-registration-based technique may be more appropriate for contrast-enhanced T1-maps and/or for patients with dense regions of replacement fibrosis, such as those with ICM.

Identifying myocardial injuries in "normal-appearing" myocardium in pediatric patients with clinically suspected myocarditis using mapping techniques

Background

Mapping techniques using cardiac magnetic resonance imaging have significantly improved the diagnostic accuracy for myocarditis with focal myocardial injuries. The aim of our study was to determine whether T1 and T2 mapping techniques could identify diffuse myocardial injuries in "normal-appearing" myocardium in pediatric patients with clinically suspected myocarditis and to evaluate the associations between diffuse myocardial injuries and cardiac function parameters.

Methods

Forty-six subjects were included in this study: 20 acute myocarditis patients, 11 subacute/chronic myocarditis patients and 15 control children. T2 values, native T1 values and the extracellular volume (ECV) of "normal-appearing" myocardium were compared among the three groups of patients. Associations between diffuse myocardial injuries and cardiac function parameters were also evaluated.

Results

The ECV of "normal-appearing" myocardium was significantly higher in the subacute/chronic myocarditis group than in the control group (30.1 ± 0.9 vs 27.0 ± 0.6, P =0.004). No significant differences in T1 and T2 values between the acute myocarditis and control groups were found. In the subacute/chronic myocarditis group, a significant association between ECV and left ventricle ejection fraction was found (P=0.03).

Conclusions

Diffuse myocardial injuries are likely to occur in subacute/chronic myocarditis patients with prolonged inflammatory responses. Mapping techniques have great value for the diagnosis and monitoring of myocarditis.

The Dynamic Interplay Between Cardiac Inflammation and Fibrosis

Heart failure is a leading cause of death worldwide. While there are multiple etiologies contributing to the development of heart failure, all cause result in impairments in cardiac function that is characterized by changes in cardiac remodeling and compliance. Fibrosis is associated with nearly all forms of heart failure and is an important contributor to disease pathogenesis. Inflammation also plays a critical role in the heart and there is a large degree of interconnectedness between the inflammatory and fibrotic response. This review discusses the cellular and molecular mechanisms contributing to inflammation and fibrosis and the interplay between the two.

Clinical assessment of adenosine stress and rest cardiac magnetic resonance T1 mapping for detecting ischemic and infarcted myocardium

Cardiac magnetic resonance (CMR) spin-lattice relaxation time (T1) may be influenced by pathologic conditions due to changes in myocardial water content. We aimed to validate the principle and investigate T1 mapping at rest and adenosine stress to differentiate ischemic and infarcted myocardium from controls. Patients with suspected coronary artery disease who underwent CMR were prospectively recruited. Native rest and adenosine stress T1 maps were obtained using standard modified Look-Locker Inversion-Recovery technique. Among 181 patients included, T1 values were measured from three groups. In the control group, 72 patients showed myocardium with a T1 profile of 1,039 ± 75 ms at rest and a significant increase during stress (4.79 ± 3.14%, p < 0.001). While the ischemic (51 patients) and infarcted (58 patients) groups showed elevated resting T1 compared to controls (1,040 ± 90 ms for ischemic; 1,239 ± 121 ms for infarcted, p < 0.001), neither of which presented significant T1 reactivity (1.38 ± 3.02% for ischemic; 1.55 ± 5.25% for infarcted). We concluded that adenosine stress and rest T1 mapping may be useful to differentiate normal, ischemic and infarcted myocardium.

Myocardial T1 and T2 quantification and water-fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

PURPOSE

This work aims to develop an approach for simultaneous water-fat separation and myocardial T₁ and T₂ quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

METHODS

Two 15-heartbeat cMRF sequences with different rosette trajectories designed for water-fat separation at 3T and 1.5T were implemented. Water T₁ and T₂ maps, water image, and fat image were generated with B₀ inhomogeneity correction using a B₀ map derived from the cMRF data themselves. The proposed water-fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.

RESULTS

Water T₁ and T₂ values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T₁ but 2~3 ms higher T₂ values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

CONCLUSION

Rosette cMRF provides fat images along with myocardial T₁ and T₂ maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.

Emerging role of cardiovascular magnetic resonance imaging in the management of pulmonary hypertension

Pulmonary hypertension (PH) is a clinical condition characterised by elevation of pulmonary arterial pressure (PAP) above normal range due to various aetiologies. While cardiac right-heart catheterisation (RHC) remains the gold standard and mandatory for establishing the diagnosis of PH, noninvasive imaging of the heart plays a central role in the diagnosis and management of all forms of PH. Although Doppler echocardiography (ECHO) can measure a range of haemodynamic and anatomical variables, it has limited utility for visualisation of the pulmonary artery and, oftentimes, the right ventricle. Cardiovascular magnetic resonance (CMR) provides comprehensive information about the anatomical and functional aspects of the pulmonary artery and right ventricle that are of prognostic significance for assessment of long-term outcomes in disease progression. CMR is suited for serial follow-up of patients with PH due to its noninvasive nature, high sensitivity to changes in anatomical and functional parameters, and high reproducibility. In recent years, there has been growing interest in the use of CMR derived parameters as surrogate endpoints for early-phase PH clinical trials. This review will discuss the role of CMR in the diagnosis and management of PH, including current applications and future developments, in comparison to other existing major imaging modalities.

Prognostic significance of T1 mapping parameters in heart failure with preserved ejection fraction: a systematic review

Heart failure with preserved ejection fraction (HFpEF) accounts for almost one-half of all heart failure (HF) patients and continues to increase in prevalence. While mortality with heart failure with reduced ejection fraction (HFrEF) has decreased over the past few decades with use of evidence-based HFrEF therapy, mortality related to heart failure with HFpEF has not changed significantly over the same time period. The combination of poor prognosis and lack of effective treatment options creates a pressing need for novel strategies for better patient characterization. We conducted a systematic review to evaluate the prognostic value of cardiac magnetic resonance (CMR)-derived T1 relaxation time and extracellular volume fraction (ECV) in HFpEF patients. PubMed, Embase, and Cochrane Central were searched for relevant studies. The primary outcomes of interest were hospitalization for HF and all-cause mortality. Five studies with 2741 patients were included. Four studies reported correlation of outcomes with ECV, 2 studies reported correlation of outcomes with native T1 time, and 1 study reported correlation of outcomes with post-contrast T1 time. All five studies showed significant correlation of CMR-derived parameters with adverse outcomes including event-free survival to cardiac event, all cause, and cardiac mortality. CMR-determined ECV is strongly correlated with adverse outcomes in HFpEF cohorts.

Non-ischemic dilated cardiomyopathy and cardiac fibrosis

Cardiac fibrosis is associated with non-ischemic dilated cardiomyopathy, increasing its morbidity and mortality. Cardiac fibroblast is the keystone of fibrogenesis, being activated by numerous cellular and humoral factors. Macrophages, CD4+ and CD8+ T cells, mast cells, and endothelial cells stimulate fibrogenesis directly by activating cardiac fibroblasts and indirectly by synthetizing various profibrotic molecules. The synthesis of type 1 and type 3 collagen, fibronectin, and α-smooth muscle actin is rendered by various mechanisms like transforming growth factor-beta/small mothers against decapentaplegic pathway, renin angiotensin system, and estrogens, which in turn alter the extracellular matrix. Investigating the underlying mechanisms will allow the development of diagnostic and prognostic tools and discover novel specific therapies. Serum biomarkers aid in the diagnosis and tracking of cardiac fibrosis progression. The diagnostic gold standard is cardiac magnetic resonance with gadolinium administration that allows quantification of cardiac fibrosis either by late gadolinium enhancement assessment or by T1 mapping. Therefore, the goal is to stop and even reverse cardiac fibrosis by developing specific therapies that directly target fibrogenesis, in addition to the drugs used to treat heart failure. Cardiac resynchronization therapy had shown to revert myocardial remodeling and to reduce cardiac fibrosis. The purpose of this review is to provide an overview of currently available data.

Prognostic value of heart failure in hemodialysis-dependent end-stage renal disease patients with myocardial fibrosis quantification by extracellular volume on cardiac magnetic resonance imaging

Background

End-stage renal disease (ESRD) patients are at high cardiovascular risk, and myocardial fibrosis (MF) accounts for most of their cardiac events. The purpose of this study is to investigate the prognostic value and risk stratification of MF as measured by extracellular volume (ECV) on cardiac magnetic resonance (CMR) for heart failure (HF) in patients with hemodialysis-dependent ESRD.

Methods

Sixty-six hemodialysis ESRD patients and 25 matched healthy volunteers were prospectively enrolled and underwent CMR to quantify multiple parameters of MF by T1 mapping and late gadolinium enhancement (LGE). All ESRD patients were followed up for 11–30 months, and the end-point met the 2016 ESC guidelines for the definition of HF.

Results

Over a median follow-up of 18 months (range 11–30 months), there were 26 (39.39%) guideline-diagnosed HF patients in the entire cohort of ESRD subjects. The native T1 value was elongated, and ECV was enlarged in the HF cohort relative to the non-HF cohort and normal controls (native T1, 1360.10 ± 50.14 ms, 1319.39 ± 55.44 ms and 1276.35 ± 56.56 ms; ECV, 35.42 ± 4.42%, 31.85 ± 3.01% and 26.97 ± 1.87%; all p<0.05). In the cardiac strain analysis, ECV was significantly correlated with global radial strain (GRS) (r = − 0.501, p = 0.009), global circumferential strain (GCS) (r = 0.553, p = 0.005) and global longitudinal strain (GLS) (r = 0.507, p = 0.008) in ESRD patients with HF. Cox proportional hazard regression models revealed that ECV (hazard ratio [HR] = 1.160, 95% confidence interval: 1.022 to 1.318, p = 0.022) was the only independent predictor of HF in ESRD patients. It also had a higher diagnostic accuracy for detecting MF (area under the curve [AUC] = 0.936; 95% confidence interval: 0.864 to 0.976) than native T1 and post T1 (all p ≤ 0.002). Kaplan-Meier analysis revealed that the high-ECV group had a shorter median overall survival time than the low-ECV group (18 months vs. 20 months, log-rank p = 0.046) and that ESRD patients with high ECV were more likely to have HF.

Conclusions

Myocardial fibrosis quantification by ECV on CMR T1 mapping was shown to be an independent risk factor of heart failure, providing incremental prognostic value and risk stratification for cardiac events in ESRD patients.

Trial registration

Chinese Clinical Trial Registry ChiCTR-DND-17012976, 13/12/2017, Retrospectively registered.

Improved Regularized Reconstruction for Simultaneous Multi-Slice Cardiac MRI T 1 Mapping

Myocardial T ₁ mapping is a quantitative MRI technique that has found great clinical utility in the detection of various heart disease. These acquisitions typically require three breath-holds, leading to long scan durations and patient discomfort. Simultaneous multi-slice (SMS) imaging has been shown to reduce the scan time of myocardial T ₁ mapping to a single breath-hold without sacrificing coverage, albeit at reduced precision. In this work, we propose a new reconstruction strategy for SMS imaging that combines the advantages of two different k-space interpolation strategies, while allowing for regularization, in order to improve the precision of accelerated mycordial T ₁ mapping.

Cardiovascular magnetic resonance: contribution to the exploration of cardiomyopathies

Background and aims

Magnetic resonance imaging is a non-invasive and non-irradiating imaging method, complementary to cardiac ultrasound in the assessment of cardiovascular disease and implicitly of cardiomyopathies. Although it is not a first intention imaging method, it is superior in the assessment of cardiac volumes, left ventricular ejection fraction, in the analysis of cardiac wall dyskinesia and myocardial tissue characteristics with and without using a contrast agent. The purpose of this paper is to review the current knowledge regarding cardiovascular magnetic resonance imaging (CMR) and its applications in cardiomyopathy analysis.

Methods

In order to create this review, relevant articles were searched and analyzed by using MeSH terms such as: “cardiac magnetic resonance imaging”, “cardiomyopathy”, “myocardial fibrosis”. Three main international databases PubMed, Web of Science and Medscape were searched. We carried out a narrative review focused on the current indications of cardiovascular magnetic resonance imaging in cardiomyopathies, both common and raret, of ischemic and nonischemic types.

Results

Cardiac magnetic resonance imaging has a very important role in the diagnosis, assessment and prognosis of common cardiomyopathies (the dilated, hypertrophic and inflammatory types) or other more rare ones such as (amyloidosis, arrhythmogenic right ventricular, non-compaction or Takotsubo cardiomyopathy), as it represents the gold standard for evaluating the ejection fraction, ventricular volumes and mass. CMR techniques, such as late gadolinium enhancement, T1 and T2 mapping have proven their usefulness, helping differentiate between ischemic (subendocardial enhancement) and nonischemic cardiomyopathy (varied pattern) or also establish the etiology. Another important feature of this imaging technique is that it can establish the myocardial viability, thus the chance of contractile recovery after revascularization. This feature is based on the transmural extent of LGE, left ventricle wall thickness and the assessment of the contractile reserve after administration of low dose dobutamine.

Conclusions

Cardiovascular magnetic resonance imaging is an indispensable tool, with proven efficiency, capable of providing the differential diagnosis between ischemic and nonischemic cardiomyopathy or establishing the etiology in the nonischemic type. In addition, these findings have a prognostic value, they may guide the patient management plan and, if necessary, can evaluate treatment response. Therefore, this technique should be part of any routine investigation of various cardiomyopathies.

Mapping versus source methods for quantifying myocardial T1 in controls and in repaired tetralogy of Fallot: interchangeability and reproducibility in children

BACKGROUND

Myocardial T1 relaxometry can be performed by contouring on individual T1-weighted source images (source method) or on a single T1 map (mapping method).

OBJECTIVE

This study compares (a) agreement between native T1 and extracellular volume results of the two methods and (b) interobserver reproducibility of the two methods in children without heart disease and those with tetralogy of Fallot (TOF).

MATERIALS AND METHODS

We retrospectively analyzed pediatric patients (controls and those with repaired TOF) with cardiac magnetic resonance examinations including extracellular volume quantification using the modified Look-Locker inversion recovery (MOLLI) sequence. We compared native T1 and extracellular volume of the entire left ventricle and interventricular septum derived using the source and the mapping approaches.

RESULTS

In the control group (n=25, median age 14.0 years, interquartile range [IQR] 11.5-16.5 years), the mapping method produced lower native T1 values than the source method in the interventricular septum (mean difference ± standard deviation [SD] = 12±15 ms, P<0.001). In the TOF group (n=50, median age 13.3 years, IQR 9.9-15.0 years), the mapping method produced lower values for native T1 and extracellular volume in the interventricular septum (mean difference 9±14 ms and 0.6±1.1%, P<0.001). In 6-12% of the children, differences were >3 standard deviations from the mean difference. Interobserver reproducibility between the two methods by intraclass correlation coefficients were clinically equivalent.

CONCLUSION

T1 and extracellular volume values generated by the source and mapping methods show systematic differences and can vary significantly in an individual child, and thus cannot be used interchangeably in clinical practice. The source method might allow for easier detection and, in some cases, mitigation of artifacts that are not infrequent in children and can be difficult to appreciate on the T1 map.

"Dark-blood" dual-energy computed tomography angiography for thoracic aortic wall imaging

OBJECTIVES

To assess the capability of a newly developed material decomposition method from contrast-enhanced dual-energy CT images, aiming to better visualize the aortic wall and aortic intramural hematoma (IMH), compared with true non-contrast (TNC) CT.

MATERIALS AND METHODS

Twenty-two patients (11 women; mean age, 61 ± 20 years) with acute chest pain underwent 25 dual-layer non-contrast and contrast-enhanced CT. CT-angiography images were retrospectively processed using two-material decomposition analysis, where we defined the first material as the content of a region of interest placed in the ascending aorta for each patient, and the second material as water. Two independent radiologists assessed the images from the second material termed "dark-blood" images and the TNC images regarding contrast-to-noise ratio (CNR) between the wall and the lumen, diagnostic quality regarding the presence of aortic wall thickening, and the inner/outer vessel wall conspicuity.

RESULTS

Diagnostic quality scores in normal aortic segments were 0.9 ± 0.3 and 2.7 ± 0.6 (p < 0.001) and wall conspicuity scores were 0.7 ± 0.5 and 1.8 ± 0.3 (p < 0.001) on TNC and dark-blood images, respectively. In aortic segments with IMH, diagnostic quality scores were 1.7 ± 0.5 and 2.4 ± 0.6 (p < 0.001) and wall conspicuity scores were 0.7 ± 0.7 and 1.8 ± 0.3 (p < 0.001) on TNC and dark-blood images, respectively. In normal aortic segments, CNRs were 0.3 ± 0.2 and 2.8 ± 0.9 on TNC and dark-blood images, respectively (p < 0.001). In aortic segments with IMH, CNRs were 0.3 ± 0.2 and 4.0 ± 1.0 on TNC and dark-blood images, respectively (p < 0.001).

CONCLUSIONS

Compared with true non-contrast CT, dark-blood material decomposition maps enhance quantitative and qualitative image quality for the assessment of normal aortic wall and IMH.

KEY POINTS

• Current dual-energy CT-angiography provides virtual non-contrast and bright-blood images. • Dark-blood images represent a new way to assess the vascular wall structure with dual-energy CT and can improve the lumen-to-wall contrast compared with true non-contrast CT. • This dual-energy CT material decomposition method is likely to improve contrast resolution in other applications as well, taking advantage of the high spatial resolution of CT.

Quantification of Myocardial Enhancement on Cine-MRI: Diagnostic Value in Cardiac Amyloidosis

RATIONALE AND OBJECTIVES

Diagnosis of cardiac amyloidosis (CA) on cardiac magnetic resonance (CMR) can be challenging and quantitative indexes are relevant to further characterize the myocardium. We hypothesize that the relative myocardial enhancement measured from pre and post contrast cine imaging provides diagnostic information for CA in the setting of left ventricular hypertrophy (LVH).

MATERIALS AND METHODS

Patients with LVH referred to our center and control subjects with normal CMR were retrospectively included. Percentage of myocardial enhancement (percentage ME) was obtained from pre and post contrast (5 minutes) cine sequences. Post contrast myocardial T1 and LGE extent were also recorded.

RESULTS

Twenty-one patients with CA, 25 patients with non-amyloid left ventricular myocardial hypertrophy (CH) and 20 controls with normal CMR were analyzed. Percentage ME was significantly higher in CA patients (200% (174-238)) than in CH patients (122% (88-151); p = 0.0001) and control patients (104% (90-149); p = 0.0001). Percentage ME was significantly correlated with the LGE extent (Rho Spearman coefficient = 0.66; p = 0.0001) and with the post contrast myocardial T1 (Rho Spearman coefficient = -0.61; p = 0.0001). With a cutoff value of 152%, the sensitivity and specificity of percentage ME for detection of CA were 90% and 80%, respectively.

CONCLUSION

Percentage ME obtained from pre and post contrast cine imaging is correlated to LGE extent and myocardial T1 and may represent an additional diagnostic parameter to consider CA in patients with LVH.

Comparison of native myocardial T1 and T2 mapping at 1.5T and 3T in healthy volunteers : Reference values and clinical implications

Background

Myocardial native T1 and T2 mapping are promising techniques for quantitative assessment of diffuse myocardial pathologies; however, due to conflicting data regarding normal values, routine clinical implementation of this method is still challenging.

Methods

To evaluate this situation during daily clinical practice the characteristics of normal values obtained in 60 healthy volunteers who underwent magnetic resonance imaging (MRI) scans on 1.5T and 3T scanners were studied. The T1 modified look-locker inversion recovery (MOLLI; 5(3)3; modified for higher heart rates) and T2 navigator gated black-blood prepared gradient-spin-echo (GraSE) sequences were used.

Results

While age and body mass index did not affect relaxation times, a gender and heart rate dependency was found showing higher T1 and T2 values in females, whereas at higher heart rates a prolongation of T1 and a shortening of T2 relaxation times was found. Particularly prone to artifacts were T2 measurements at 3T and the inferolateral wall. In the individual setting mean relaxation times for T1 were 995.8 ± 30.9 ms at 1.5T and 1183.8 ± 37.5 ms at 3T and 55.8 ± 2.8 ms at 1.5T and 51.6 ± 3 ms at 3T for T2 indicating a high dependency of reference values on MRI protocol when compared to the literature. Furthermore, as presumed mean T1 and T2 values correlated in the same individual.

Conclusions

The T1 and T2 relaxation times depend on physiological factors and especially on MRI protocols. Therefore, reference values should be validated individually in every radiological institution before implementing mapping protocols in daily clinical practice. Correlation of mean T1 and T2 values in the same proband at both field strengths indicates intraindividual reproducibility.

Cardiac Magnetic Resonance Fingerprinting: Technical Overview and Initial Results

Cardiovascular magnetic resonance is a versatile tool that enables noninvasive characterization of cardiac tissue structure and function. Parametric mapping techniques have allowed unparalleled differentiation of pathophysiological differences in the myocardium such as the delineation of myocardial fibrosis, hemorrhage, and edema. These methods are increasingly used as part of a tool kit to characterize disease states such as cardiomyopathies and coronary artery disease more accurately. Currently conventional mapping techniques require separate acquisitions for T1 and T2 mapping, the values of which may depend on specifics of the magnetic resonance imaging system hardware, pulse sequence implementation, and physiological variables including blood pressure and heart rate. The cardiac magnetic resonance fingerprinting (cMRF) technique has recently been introduced for simultaneous and reproducible measurement of T1 and T2 maps in a single scan. The potential for this technique to provide consistent tissue property values independent of variables including scanner, pulse sequence, and physiology could allow an unbiased framework for the assessment of intrinsic properties of cardiac tissue including structure, perfusion, and parameters such as extracellular volume without the administration of exogenous contrast agents. This review seeks to introduce the basics of the cMRF technique, including pulse sequence design, dictionary generation, and pattern matching. The potential applications of cMRF in assessing diseases such as nonischemic cardiomyopathy are also briefly discussed, and ongoing areas of research are described.

Medical Imaging: From Roentgen to the Digital Revolution, and Beyond

Today medical imaging is an essential component of the entire health-care continuum, from wellness and screening, to early diagnosis, treatment selection, and follow-up. Patient triage in both acute care and chronic disease, imaging-guided interventions, and optimization of treatment planning are now integrated into routine clinical practice in all subspecialties. This paper provides a brief review of major milestones in medical imaging from its inception to date, with a few considerations regarding future directions in this important field.

A vectorized Levenberg-Marquardt model fitting algorithm for efficient post-processing of cardiac T1 mapping MRI

PURPOSE

T₁ mapping is an emerging MRI research tool to assess diseased myocardial tissue. Recent research has been focusing on the image acquisition protocol and motion correction, yet little attention has been paid to the curve fitting algorithm.

METHODS

After nonrigid registration of the image series, a vectorized Levenberg-Marquardt (LM) technique is proposed to improve the robustness of the curve fitting algorithm by allowing spatial regularization of the parametric maps. In addition, a region-based initialization is proposed to improve the initial guess of the T₁ value. The algorithm was validated with cardiac T₁ mapping data from 16 volunteers acquired with saturation-recovery (SR) and inversion-recovery (IR) techniques at 3T, both pre- and post-injection of a contrast agent. Signal models of T₁ relaxation with 2 and 3 parameters were tested.

RESULTS

The vectorized LM fitting showed good agreement with its pixel-wise version but allowed reduced calculation time (60 s against 696 s on average in Matlab with 256 × 256 × 8(11) images). Increasing the spatial regularization parameter led to noise reduction and improved precision of T₁ values in SR sequences. The region-based initialization was particularly useful in IR data to reduce the variability of the blood T₁.

CONCLUSIONS

We have proposed a vectorized curve fitting algorithm allowing spatial regularization, which could improve the robustness of the curve fitting, especially for myocardial T₁ mapping with SR sequences.

Structural and Functional Correlates of Myocardial T1 Mapping in 321 Patients With Hypertrophic Cardiomyopathy

OBJECTIVE

The aim of this study was to evaluate the structural and functional correlates of T1 mapping in 321 patients with hypertrophic cardiomyopathy (HCM).

METHODS

Three hundred twenty-one patients with HCM who underwent cardiac magnetic resonance from 2003 to 2013 were retrospectively identified from our institution's HCM registry. Left ventricular volume, function, late gadolinium enhancement (LGE), and Look-Locker T1 time were quantified. T1 time was normalized to blood pool to calculate T1 ratio. Correlations between LGE%, T1 ratio, and structural and functional features were performed using Pearson correlation coefficient.

RESULTS

Late gadolinium enhancement showed stronger correlation with left ventricular mass index (r = 0.41, P < 0.001) compared with T1 ratio (r = -0.17, P = 0.004). Both LGE% and T1 ratio correlated with ejection fraction (r = -0.18 and P = 0.002 vs r = 0.21 and P < 0.001, respectively). E/e' showed correlation with LGE% but not with T1 ratio.

CONCLUSIONS

Late gadolinium enhancement was more strongly correlated with the phenotypic expression of HCM compared with T1 ratio.

Simultaneous multislice imaging for native myocardial T1 mapping: Improved spatial coverage in a single breath-hold

PURPOSE

To develop a saturation recovery myocardial T1 mapping method for the simultaneous multislice acquisition of three slices.

METHODS

Saturation pulse-prepared heart rate independent inversion recovery (SAPPHIRE) T1 mapping was implemented with simultaneous multislice imaging using FLASH readouts for faster coverage of the myocardium. Controlled aliasing in parallel imaging (CAIPI) was used to achieve minimal noise amplification in three slices. Multiband reconstruction was performed using three linear reconstruction methods: Slice- and in-plane GRAPPA, CG-SENSE, and Tikhonov-regularized CG-SENSE. Accuracy, spatial variability, and interslice leakage were compared with single-band T1 mapping in a phantom and in six healthy subjects.

RESULTS

Multiband phantom T1 times showed good agreement with single-band T1 mapping for all three reconstruction methods (normalized root mean square error <1.0%). The increase in spatial variability compared with single-band imaging was lowest for GRAPPA (1.29-fold), with higher penalties for Tikhonov-regularized CG-SENSE (1.47-fold) and CG-SENSE (1.52-fold). In vivo multiband T1 times showed no significant difference compared with single-band (T1 time ± intersegmental variability: single-band, 1580 ± 119 ms; GRAPPA, 1572 ± 145 ms; CG-SENSE, 1579 ± 159 ms; Tikhonov, 1586 ± 150 ms [analysis of variance; P = 0.86]). Interslice leakage was smallest for GRAPPA (5.4%) and higher for CG-SENSE (6.2%) and Tikhonov-regularized CG-SENSE (7.9%).

CONCLUSION

Multiband accelerated myocardial T1 mapping demonstrated the potential for single-breath-hold T1 quantification in 16 American Heart Association segments over three slices. A 1.2- to 1.4-fold higher in vivo spatial variability was observed, where GRAPPA-based reconstruction showed the highest homogeneity and the least interslice leakage. Magn Reson Med 78:462-471, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Hypertrophic cardiomyopathy and left ventricular hypertrophy in hypertensive heart disease with mildly reduced or preserved ejection fraction: insight from altered mechanics and native T1 mapping

AIM

To explore the relationship between extracellular volume (ECV), native T1, and systolic strain in hypertrophic cardiomyopathy (HCM) and hypertensive patients with left ventricular hypertrophy (HTN LVH) with mildly reduced or preserved ejection fraction.

MATERIALS AND METHODS

T1 mapping was performed in 45 patients with late gadolinium enhancement positive (LGE+) HCM (mean age, 53±6 years), 11 patients with LGE- (LGE-) HCM (mean age, 56±5 years), and 20 patients with HTN LVH (mean age, 55±6 years) on at 3 T magnetic resonance imaging (MRI) using the modified look-locker inversion-recovery (MOLLI) pulse sequence. Mean T1 value, ECV and circumferential strain parameters were determined for each patient.

RESULTS

Overall, the HCM patients had higher native T1 values (1242.92±68.94) and ECV (0.31±0.05) in comparison to those of the HTN LVH patients (1197±46.80, 0.27±0.04; p<0.05). In the subgroup analysis, the HCM LGE+ patients had the highest native T1 values among the three groups. The HCM LGE+ patients had higher ECV than the LGE- patients. HCM LGE- patients had higher ECV than HTN LVH patients (p<0.05). Peak systolic circumferential strain and early diastolic strain rates were reduced in the HCM LGE+ patients in comparison to the HCM LGE- and HTN LVH patients (p<0.05). Reduced peak systolic and early diastolic circumferential strain rates were associated with increased levels of ECV and native T1 values among all the patients.

CONCLUSION

HCM LGE+ patients had higher native T1 values, higher ECV, and an associated reduction in early diastolic strain rates and peak systolic circumferential strains when compared to the HCM LGE- and HTN LVH patients with mildly reduced or preserved ejection fraction.

Current Understanding of the Pathophysiology of Myocardial Fibrosis and Its Quantitative Assessment in Heart Failure

Myocardial fibrosis is an important part of cardiac remodeling that leads to heart failure and death. Myocardial fibrosis results from increased myofibroblast activity and excessive extracellular matrix deposition. Various cells and molecules are involved in this process, providing targets for potential drug therapies. Currently, the main detection methods of myocardial fibrosis rely on serum markers, cardiac magnetic resonance imaging, and endomyocardial biopsy. This review summarizes our current knowledge regarding the pathophysiology, quantitative assessment, and novel therapeutic strategies of myocardial fibrosis.

3D myocardial T1 mapping using saturation recovery

Purpose

To propose a 3D quantitative high‐resolution T₁ mapping technique, called 3D SASHA (saturation‐recovery single‐shot acquisition), which combines a saturation recovery pulse with 1D‐navigator‐based‐respiratory motion compensation to acquire the whole volume of the heart in free breathing. The sequence was tested and validated both in a T₁ phantom and in healthy subjects.

Materials and Methods

The 3D SASHA method was implemented on a 1.5T scanner. A diaphragmatic navigator was used to allow free‐breathing acquisition and the images were acquired with a resolution of 1.4 × 1.4 × 8 mm³. For assessment of accuracy and precision the sequence was compared with the reference gold‐standard inversion‐recovery spin echo (IRSE) pulse sequence in a T₁ phantom, while for the in vivo studies (10 healthy volunteers) 3D SASHA was compared with the clinically used 2D MOLLI (3‐3‐5) and 2D SASHA protocols.

Results

There was good agreement between the T₁ values measured in a T₁ phantom with 3D SASHA and the reference IRSE pulse sequences (1111.6 ± 31 msec vs. 1123.6 ± 8 msec, P = 0.9947). Mean and standard deviation of the myocardial T₁ values in healthy subjects measured with 2D MOLLI, 2D SASHA, and 3D SASHA sequences were 881 ± 40 msec, 1181.3 ± 32 msec, and 1153.6 ± 28 msec respectively.

Conclusion

The proposed 3D SASHA sequence allows for high‐resolution free‐breathing whole‐heart T₁‐mapping with T₁ values in good agreement with the 2D SASHA and improved precision.

Level of Evidence: 2

Technical Efficacy: Stage 1

J. MAGN. RESON. IMAGING 2017;46:218–227