Modified look-locker inversion recovery T1 mapping indices: assessment of accuracy and reproducibility between magnetic resonance scanners

Repeatability of Open-MOLLI: An open-source inversion recovery myocardial T1 mapping sequence for fast prototyping

PURPOSE

To develop an open-source prototype of myocardial T1 mapping (Open-MOLLI) to improve accessibility to cardiac T1 mapping and evaluate its repeatability. With Open-MOLLI, we aim to enable faster implementation and testing of sequence modifications and to facilitate inter-scanner and cross-vendor reproducibility studies.

METHODS

Open-MOLLI is an inversion-recovery sequence using a balanced SSFP (bSSFP) readout, with inversion and triggering schemes based on the 5(3)3 MOLLI sequence, developed in Pulseq. Open-MOLLI and MOLLI sequences were acquired in the ISMRM/NIST phantom and 21 healthy volunteers. In 18 of those subjects, Open-MOLLI and MOLLI were repeated in the same session (test-retest).

RESULTS

Phantom T1 values were comparable between methods, specifically for the vial with reference T1 value most similar to healthy myocardium T1 (T1vial3 = 1027 ms): T1MOLLI = 1011 ± 24 ms versus T1Open-MOLLI = 1009 ± 20 ms. In vivo T1 estimates were similar between Open-MOLLI and MOLLI (T1MOLLI = 1004 ± 33 ms vs. T1Open-MOLLI = 998 ± 52 ms), with a mean difference of -17 ms (p = 0.20), despite noisier Open-MOLLI weighted images and maps. Repeatability measures were slightly higher for Open-MOLLI (RCMOLLI = 3.0% vs. RCOpen-MOLLI = 4.4%).

CONCLUSION

The open-source sequence Open-MOLLI can be used for T1 mapping in vivo with similar mean T1 values to the MOLLI method. Open-MOLLI increases the accessibility to cardiac T1 mapping, providing also a base sequence to which further improvements can easily be added and tested.

Myocardial tissue imaging with cardiovascular magnetic resonance

Alteration in myocardial tissue, such as myocardial fibrosis, edema, inflammation, or accumulation with amyloid, lipids, or iron, has an important role in the cardiac remodeling that leads to diastolic and/or systolic dysfunction and the development of chronic heart failure, increasing the risk of adverse cardiovascular events. Thus, the early detection of changes at myocardial tissue level has great diagnostic and prognostic potential. The gold standard technique to assess these myocardial alterations is endomyocardial biopsy. However, this has been limited to a few patients due to the invasive nature, sampling errors, and its inability to assess the entire myocardium. Cardiovascular magnetic resonance (CMR) has emerged as the gold standard imaging not only for assessing cardiac volume, function quantification, and viability but also for noninvasive myocardial tissue characterization over the past decade. Its ability to characterize myocardial tissue composition is unique among noninvasive imaging modalities in cardiovascular disease. Currently, multi-parametric myocardial characterization with T1, T2, and extracellular volume has the potential to identify and track diffuse pathology in various diseases. In this review article, we present the role of established and emerging CMR techniques in myocardial tissue characterization, with an emphasis on T1 and T2 mapping, in clinical practice.

A method for T1 and T2 relaxation times validation and harmonization as a support to MRI mapping

We present a proof-of-concept study focusing on a method for the intra- and inter-center validation and harmonization of data obtained from MRI T₁ and T₂ maps. The method is based on a set of MnCl₂ samples that provide in-scan ground-truth reference values regardless of the details of the MRI protocol. The relaxation times of MnCl₂ aqueous solutions were first measured by means of an NMR laboratory relaxometer, as a function of concentration and temperature. The obtained T₁ and T₂ values, once renormalized at the scanner temperature, were used as reference values for the MRI mapping measurements of the MnCl₂ relaxation times. By using different clinical MRI scanners and sequences, we found a good agreement for standard and turbo sequences (limits of agreement: 5% for IR, SE, IR-TSE; 10% for TSE), while an under-estimation and an over-estimation were found respectively for MOLLI and T₂-prep TrueFISP, as already reported in the literature. The linearity of the relaxation rates with the concentration predicted by the Solomon-Bloembergen-Morgan theory was observed for every dataset at all temperatures, except for T₂-prep TrueFISP maps results. Some preliminary results of an in vivo experiment are also presented.

Development, validation, qualification, and dissemination of quantitative MR methods: Overview and recommendations by the ISMRM quantitative MR study group

On behalf of the International Society for Magnetic Resonance in Medicine (ISMRM) Quantitative MR Study Group, this article provides an overview of considerations for the development, validation, qualification, and dissemination of quantitative MR (qMR) methods. This process is framed in terms of two central technical performance properties, i.e., bias and precision. Although qMR is confounded by undesired effects, methods with low bias and high precision can be iteratively developed and validated. For illustration, two distinct qMR methods are discussed throughout the manuscript: quantification of liver proton-density fat fraction, and cardiac T₁ . These examples demonstrate the expansion of qMR methods from research centers toward widespread clinical dissemination. The overall goal of this article is to provide trainees, researchers, and clinicians with essential guidelines for the development and validation of qMR methods, as well as an understanding of necessary steps and potential pitfalls for the dissemination of quantitative MR in research and in the clinic.

Recent Advances in Fibrosis and Scar Segmentation From Cardiac MRI: A State-of-the-Art Review and Future Perspectives

Segmentation of cardiac fibrosis and scars is essential for clinical diagnosis and can provide invaluable guidance for the treatment of cardiac diseases. Late Gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) has been successful in guiding the clinical diagnosis and treatment reliably. For LGE CMR, many methods have demonstrated success in accurately segmenting scarring regions. Co-registration with other non-contrast-agent (non-CA) modalities [e.g., balanced steady-state free precession (bSSFP) cine magnetic resonance imaging (MRI)] can further enhance the efficacy of automated segmentation of cardiac anatomies. Many conventional methods have been proposed to provide automated or semi-automated segmentation of scars. With the development of deep learning in recent years, we can also see more advanced methods that are more efficient in providing more accurate segmentations. This paper conducts a state-of-the-art review of conventional and current state-of-the-art approaches utilizing different modalities for accurate cardiac fibrosis and scar segmentation.

Extracellular volume quantification using synthetic haematocrit assessed from native and post-contrast longitudinal relaxation T1 times of a blood pool

Background

In terms of cardiovascular magnetic resonance are haematocrit values required for calculation of extracellular volume fraction (ECV). Previously published studies have hypothesized that haematocrit could be calculated from T1 blood pool relaxation time, however only native T1 relaxation time values have been used and the resulting formulae had been both in reciprocal and linear proportion. The aim of the study was to generate a synthetic haematocrit formula from only native relaxation time values first, calculate whether linear or reciprocal model is more precise in haematocrit estimation and then determine whether adding post-contrast values further improve its precision.

Methods

One hundred thirty-nine subjects underwent CMR examination. Haematocrit was measured using standard laboratory methods. Afterwards T1 relaxation times before and after the application of a contrast agent were measured and a statistical relationship between these values was calculated.

Results

Different linear and reciprocal models were created to estimate the value of synthetic haematocrit and ECV. The highest coefficient of determination was observed in the combined reciprocal model “− 0.047 + (779/ blood native) − (11.36/ blood post-contrast)”.

Conclusions

This study provides more evidence that assessing synthetic haematocrit and synthetic ECV is feasible and statistically most accurate model to use is reciprocal. Adding post-contrast values to the calculation was proved to improve the precision of the formula statistically significantly.

MRI Mapping of Renal T1: Basic Concept

In renal MRI, measurement of the T₁ relaxation time of water molecules may provide a valuable biomarker for a variety of pathological conditions. Due to its sensitivity to the tissue microenvironment, T₁ has gained substantial interest for noninvasive imaging of renal pathology, including inflammation and fibrosis. In this chapter, we will discuss the basic concept of T₁ mapping and different T₁ measurement techniques and we will provide an overview of emerging preclinical applications of T₁ for imaging of kidney disease.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.

Myocardial T1-mapping and extracellular volume in pulmonary arterial hypertension: A systematic review and meta-analysis

INTRODUCTION

Elevated myocardial T₁-mapping and extracellular volume (ECV) measured on cardiac MR (CMR) imaging is associated with myocardial abnormalities such as oedema or fibrosis. This meta-analysis aims to provide a summary of T₁-mapping and ECV values in pulmonary arterial hypertension (PAH) and compare their values with controls.

METHODS

We searched CENTRAL, MEDLINE, Embase, and Web of Science in August 2020. We included CMR studies reporting T₁-mapping or ECV values in adults with any type of PAH. We calculated the mean difference of T₁-values and ECV between PAH and controls.

RESULTS

We included 12 studies with 674 participants. T₁-values were significantly higher in PAH with the highest mean difference (MD) recorded at the RV insertion points (RVIP) (108 milliseconds (ms), 95% confidence intervals (CI) 89 to 128), followed by the RV free wall (MD 91 ms, 95% CI 56 to 126). The pooled mean T₁-value in PAH at the RVIP was 1084, 95% CI (1071 to 1097) measured using 1.5 Tesla Siemens systems. ECV was also higher in PAH with an MD of 7.5%, 95% CI (5.9 to 9.1) at the RV free wall.

CONCLUSION

T₁ mapping values in PAH patients are on average 9% higher than healthy controls when assessed under the same conditions including the same MRI system, magnetic field strength or sequence used for acquisition. The highest T₁ and ECV values are at the RVIP. T₁ mapping and ECV values in PH are higher than the values reported in cardiomyopathies and were associated with poor RV function and RV dilatation.

Diffuse myocardial fibrosis by T1 mapping is associated with heart failure in pediatric primary dilated cardiomyopathy

BACKGROUND

In adult cardiomyopathy (CM), diffuse myocardial fibrosis is associated with adverse clinical outcome. However, its relevance in pediatric patients remains relatively unknown. The study aimed to evaluate myocardial extracellular volume (ECV) reflecting diffuse myocardial fibrosis with cardiovascular magnetic resonance (CMR) T1 mapping, and to analyze correlations with clinical and functional data in children and adolescents with different CM phenotypes.

METHODS

Patients with primary dilated (DCM), hypertrophic (HCM) or left ventricular non-compaction CM (LVNC) were prospectively enrolled and compared with healthy controls. Study participants underwent standardized CMR with modified Look-Locker Inversion recovery (MOLLI) T1 mapping.

RESULTS

In total, 33 patients (median age 12.0 years; DCM: n = 10, HCM: n = 13; LVNC: n = 10) and 7 controls (14.5 years) were included. DCM: ECV was higher than in controls (38.1 ± 7.5% vs. 27.2 ± 3.6%; p = 0.014). Patients with elevated ECV were younger than those with normal values (p = 0.044). ECV correlated with N-terminal pro brain natriuretic peptide (r = 0.66, p = 0.038), left ventricular ejection fraction (r = -0.63, p = 0.053), and stroke volume of left (r = -0.75, p = 0.013) and right ventricle (r = -0.67, p = 0.033). During a median follow-up of 25.3 months, 3 patients underwent heart transplantation (HTx), and 2 were listed for HTx. All 5 patients had elevated ECV.

HCM/LVNC

ECV was within normal range in HCM (25.5 ± 4.5%) and LVNC (29.6 ± 4.2), and was not related with clinical and/or functional parameters.

CONCLUSIONS

Our results indicate an increased burden of diffuse myocardial fibrosis in relation with younger age in pediatric DCM. ECV was associated with clinical and biventricular functional markers of heart failure in DCM.

Non-contrast myocardial T1 global and regional reference values at 3 Tesla cardiac magnetic resonance in aortic stenosis

BACKGROUND

T1 mapping using cardiac magnetic resonance (CMR) was recently proposed as a promising non-contrast imaging technique for the assessment of diffuse myocardial fibrosis (MF) in aortic stenosis (AS).

AIMS

To provide reference values for native T1 mapping at 3 Tesla magnetic field strength in subjects with moderate or severe AS and in control subjects; to identify factors associated with the presence of diffuse MF in severe AS; to assess the regional distribution of diffuse MF; and to compare the level of diffuse MF in the different types of AS, stratified by flow and gradient patterns.

METHODS

Retrospective study based on 160 consecutive patients with moderate (n=11) to severe (n=149) AS and 47 control subjects referred for CMR.

RESULTS

Mean native T1 increased progressively across controls (1221±23ms), moderate AS (1249±26ms) and severe AS (1273±43ms). T1 times correlated significantly with left ventricular (LV) remodelling (indexed LV mass and LV diastolic volume) and functional LV alterations (global longitudinal strain and LV ejection fraction). Native T1 appears to be elevated in the basal segments of the septum in moderate AS, and to extend to midventricular and apical segments in severe AS. Mean T1 time was higher in classical low-flow/low-gradient AS (1295±62ms) than in the other types of AS (P=0.006). The level of diffuse MF in paradoxical low-flow/low-gradient AS (1280±42ms) was higher than in moderate AS, but similar to that in high-gradient AS (1271±42ms) (P=0.07).

CONCLUSIONS

Assessment of diffuse MF in AS using T1 mapping is feasible and reproducible in clinical practice. T1 value increases with AS severity, along with morphological and functional LV alterations, particularly in the basal segments of the septum.

Left Ventricular Remodeling in Degenerative Aortic Valve Stenosis

Aortic stenosis was once considered a pure isolated valve obstacle challenging left ventricle driving force of contraction and flow generation. Left ventricular (LV) adaptation was merely interpreted as a uniform hypertrophic response to increased afterload. However, in these last 2 decades cardiac imaging research and some histopathology correlation studies brought insight towards the complex interaction between the vasculature, the valve and the myocardium. Verily, LV remodeling in this setting is a complex multidetermined process that goes further beyond myocardial hypertrophy. Ultrastructural changes involving both diffuse and replacement fibrosis of the myocardium take part and might explain the transition of clinical phenotypes with distinct prognosis, from compensated hypertrophy to LV maladaptive dysfunction and heart failure. Presently, the combined appropriate use of echocardiography and cardiac magnetic resonance may better assess the global LV afterload, hypertrophy and geometric remodeling, global and regional LV function, beyond ejection fraction, and structural changes that include the fibrotic burden of the myocardium. As a whole these may not only better stratify individual risk of disease progression but also identify patients benefiting from earlier valve intervention. In this paper, we review the maladaptive response of the LV to chronic pressure overload, describing the different signaling pathways and mechanisms that underly both hypertrophy and remodeling. Histomorphology changes in this setting are described and we try to make sense of the use of new imaging tools for LV characterization.

Focal scar and diffuse myocardial fibrosis are independent imaging markers in repaired tetralogy of Fallot

Aims

To identify the correlates of focal scar and diffuse fibrosis in patients with history of tetralogy of Fallot (TOF) repair.

Methods and results

Consecutive patients with prior TOF repair underwent electrocardiogram, 24-h Holter, transthoracic echocardiography, exercise testing, and cardiac magnetic resonance (CMR) including cine imaging to assess ventricular volumes and ejection fraction, T1 mapping to assess left ventricular (LV) and right ventricular (RV) diffuse fibrosis, and free-breathing late gadolinium-enhanced imaging to quantify scar area at high spatial resolution. Structural imaging data were related to clinical characteristics and functional imaging markers. Cine and T1 mapping results were compared with 40 age- and sex-matched controls. One hundred and three patients were enrolled (age 28 ± 15 years, 36% women), including 36 with prior pulmonary valve replacement (PVR). Compared with controls, TOF showed lower LV ejection fraction (LVEF) and RV ejection fraction (RVEF), and higher RV volume, RV wall thickness, and native T1 and extracellular volume values on both ventricles. In TOF, scar area related to LVEF and RVEF, while LV and RV native T1 related to RV dilatation. On multivariable analysis, scar area and LV native T1 were independent correlates of ventricular arrhythmia, while RVEF was not. Patients with history of PVR showed larger scars on RV outflow tract but shorter LV and RV native T1.

Conclusion

Focal scar and biventricular diffuse fibrosis can be characterized on CMR after TOF repair. Scar size relates to systolic dysfunction, and diffuse fibrosis to RV dilatation. Both independently relate to ventricular arrhythmias. The finding of shorter T1 after PVR suggests that diffuse fibrosis may reverse with therapy.

Systolic modified Look-Locker inversion recovery myocardial T1 mapping improves the accuracy of T1 and extracellular volume fraction measurements of patients with high heart rate or atrial fibrillation

Image data for T1 mapping are generally acquired during mid-diastole period. However, T1 mapping tends to fail for patients with high heart rate or atrial fibrillation because of short or irregular R-R interval. Focusing on the evidence that the timing of systole is more stable than that of diastole from the R wave, we compared systolic T1 mapping with conventional diastolic T1 mapping for all participants (n = 58) by visual scoring of T1 calculation error. The systolic scores were significantly better than the diastolic scores (p < 0.05). This advantage of the systolic scores was confirmed selectively for patients with atrial fibrillation (p < 0.05, n = 19). The successful number of nonrigid image registration alignment for extracellular volume fraction (ECV) analysis also increased significantly for systolic images compared with diastolic images (p < 0.05). Thus, systolic T1 mapping improves the accuracy of T1 values and ECV analysis.

Early detection of heart function abnormality by native T1: a comparison of two T1 quantification methods

Objective

To compare the robustness of native T1 mapping using mean and median pixel-wise quantification methods.

Methods

Fifty-seven consecutive patients without overt signs of heart failure were examined in clinical routine for suspicion of cardiomyopathy. MRI included the acquisition of native T1 maps by a motion-corrected modified Look-Locker inversion recovery sequence at 1.5 T. Heart function status according to four established volumetric left ventricular (LV) cardio MRI parameter thresholds was used for retrospective separation into subgroups of normal (n = 26) or abnormal heart function (n = 31). Statistical normality of pixel-wise T1 was tested on each myocardial segment and mean and median segmental T1 values were assessed.

Results

Segments with normally distributed pixel-wise T1 (57/58%) showed no difference between mean and median quantification in either patient group, while differences were highly significant (p < 0.001) for the respective 43/42% non-normally distributed segments. Heart function differentiation between two patient groups was significant in 14 myocardial segments (p < 0.001–0.040) by median quantification compared with six (p < 0.001–0.042) by using the mean. The differences by median quantification were observed between the native T1 values of the three coronary artery territories of normal heart function patients (p = 0.023) and insignificantly in the abnormal patients (p = 0.053).

Conclusion

Median quantification increases the robustness of myocardial native T1 definition, regardless of statistical normality of the data. Compared with the currently prevailing method of mean quantification, differentiation between LV segments and coronary artery territories is better and allows for earlier detection of heart function impairment.

Key Points

• Median pixel-wise quantification of native T1 maps is robust and can be applied regardless of the statistical distribution of data points.

• Median quantification is more sensitive to early heart function abnormality compared with mean quantification.

• The new method yields significant native T1 value differentiation between the three coronary artery territories.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06364-9) contains supplementary material, which is available to authorized users.

Myocardial native-T1 times are elevated as a function of hypertrophy, HbA1c, and heart rate in diabetic adults without diffuse fibrosis

PURPOSE

Cardiac native-T1 times have correlated to extracellular volume fraction in patients with confirmed fibrosis. However, whether other factors that can occur either alongside or independently of fibrosis including increased intracellular water volume, altered magnetization transfer (MT), or glycation of hemoglobin, lengthen T1 times in the absence of fibrosis remains unclear. The current study examined whether native-T1 times are elevated in hypertrophic diabetics with elevated hemoglobin A1C (HbA1c) without diffuse fibrosis.

METHODS

Native-T1 times were quantified in 27 diabetic and 10 healthy adults using a modified Look-Locker imaging (MOLLI) sequence at 1.5 T. The MT ratio (MTR) was quantified using dual flip angle cine balanced steady-state free precession. Gadolinium (0.2 mmol/kg Gd-DTPA) was administered as a bolus and post-contrast T1-times were quantified after 15 min. Means were compared using a two-tailed student's t-test, while correlations were assessed using Pearson's correlations.

RESULTS

While left ventricular volumes, ejection fraction, and cardiac output were similar between groups, left ventricular mass and mass-to-volume ratio (MVR) were significantly higher in diabetic adults. Mean ECV (0.25 ± 0.02 Healthy vs. 0.25 ± 0.03 Diabetic, P = 0.47) and MTR (125 ± 16% Healthy vs. 125 ± 9% Diabetic, P = 0.97) were similar, however native-T1 times were significantly higher in diabetics (1016 ± 21 ms Healthy vs. 1056 ± 31 ms Diabetic, P = 0.00051). Global native-T1 times correlated with MVR (ρ = 0.43, P = 0.008) and plasma HbA1c levels (ρ = 0.43, P = 0.0088) but not ECV (ρ = 0.06, P = 0.73). Septal native-T1 times correlated with septal wall thickness (ρ = 0.50, P = 0.001).

CONCLUSION

In diabetic adults with normal ECV values, elevated native-T1 times may reflect increased intracellular water volume and changes secondary to increased hemoglobin glycation.

Deep Learning for Diagnosis of Chronic Myocardial Infarction on Nonenhanced Cardiac Cine MRI

Background Renal impairment is common in patients with coronary artery disease and, if severe, late gadolinium enhancement (LGE) imaging for myocardial infarction (MI) evaluation cannot be performed. Purpose To develop a fully automatic framework for chronic MI delineation via deep learning on non-contrast material-enhanced cardiac cine MRI. Materials and Methods In this retrospective single-center study, a deep learning model was developed to extract motion features from the left ventricle and delineate MI regions on nonenhanced cardiac cine MRI collected between October 2015 and March 2017. Patients with chronic MI, as well as healthy control patients, had both nonenhanced cardiac cine (25 phases per cardiac cycle) and LGE MRI examinations. Eighty percent of MRI examinations were used for the training data set and 20% for the independent testing data set. Chronic MI regions on LGE MRI were defined as ground truth. Diagnostic performance was assessed by analysis of the area under the receiver operating characteristic curve (AUC). MI area and MI area percentage from nonenhanced cardiac cine and LGE MRI were compared by using the Pearson correlation, paired t test, and Bland-Altman analysis. Results Study participants included 212 patients with chronic MI (men, 171; age, 57.2 years ± 12.5) and 87 healthy control patients (men, 42; age, 43.3 years ± 15.5). Using the full cardiac cine MRI, the per-segment sensitivity and specificity for detecting chronic MI in the independent test set was 89.8% and 99.1%, respectively, with an AUC of 0.94. There were no differences between nonenhanced cardiac cine and LGE MRI analyses in number of MI segments (114 vs 127, respectively; P = .38), per-patient MI area (6.2 cm² ± 2.8 vs 5.5 cm² ± 2.3, respectively; P = .27; correlation coefficient, r = 0.88), and MI area percentage (21.5% ± 17.3 vs 18.5% ± 15.4; P = .17; correlation coefficient, r = 0.89). Conclusion The proposed deep learning framework on nonenhanced cardiac cine MRI enables the confirmation (presence), detection (position), and delineation (transmurality and size) of chronic myocardial infarction. However, future larger-scale multicenter studies are required for a full validation. Published under a CC BY 4.0 license. Online supplemental material is available for this article. See also the editorial by Leiner in this issue.

Quantification in cardiovascular magnetic resonance: agreement of software from three different vendors on assessment of left ventricular function, 2D flow and parametric mapping

BACKGROUND

Quantitative results of cardiovascular magnetic resonance (CMR) image analysis influence clinical decision making. Image analysis is performed based on dedicated software. The manufacturers provide different analysis tools whose algorithms are often unknown. The aim of this study was to evaluate the impact of software on quantification of left ventricular (LV) assessment, 2D flow measurement and T1- and T2-parametric mapping.

METHODS

Thirty-one data sets of patients who underwent a CMR Scan on 1.5 T were analyzed using three different software (Circle CVI: cvi42, Siemens Healthineers: Argus, Medis: Qmass/Qflow) by one reader blinded to former results. Cine steady state free precession short axis images were analyzed regarding LV ejection fraction (EF), end-systolic and end-diastolic volume (ESV, EDV) and LV mass. Phase-contrast magnetic resonance images were evaluated for forward stroke volume (SV) and peak velocity (Vmax). Pixel-wise generated native T1- and T2-maps were used to assess T1- and T2-time. Forty-five data sets were evaluated twice (15 per software) for intraobserver analysis. Equivalence was considered if the confidence interval of a paired assessment of two sofware was within a tolerance interval defined by ±1.96 highest standard deviation obtained by intraobserver analysis.

RESULTS

For each parameter, thirty data sets could be analyzed with all three software. All three software (A/B, A/C, B/C) were considered equivalent for LV EF, EDV, ESV, mass, 2D flow SV and T2-time. Differences between software were detected in flow measurement for Vmax and in parametric mapping for T1-time. For Vmax, equivalence was given between software A and C and for T1-time equivalence was given between software B and C.

CONCLUSION

Software had no impact on quantitative results of LV assessment, T2-time and SV based on 2D flow. In contrast to that, Vmax and T1-time may be influenced by software. CMR reports should contain the name and version of the software applied for image analysis to avoid misinterpretation upon follow-up and research examinations.

TRIAL REGISTRATION

ISRCTN12210850 . Registered 14 July 2017, retrospectively registered.

Reference range determination for imaging biomarkers: Myocardial T1

BACKGROUND

Imaging biomarkers, such as the T₁ relaxation time of the myocardium using MRI, can be valuable in cardiac medicine if they are properly validated. Consensus statements recommend that for myocardial T₁ , each investigator should establish a reference range.

PURPOSE

To describe a statistically valid method for determining and reporting the reference range in each center, which simultaneously minimizes the twin risks of undersampling, leading to a uselessly uncertain range, and oversampling, which exposes volunteers to unnecessary scanning and wastes resources.

STUDY TYPE

Cohort.

POPULATION

In all, 278 normal human subjects without cardiac disease from two cardiac MR centers.

FIELD STRENGTH/SEQUENCE

1.5 T and 3 T; Modified Look-Locker Inversion recovery sequence.

ASSESSMENT

The T₁ relaxation time was estimated from multiple samples of tissue magnetization after inversion. A valid method for calculating a reference range was used.

STATISTICAL TESTS

Shapiro-Wilk test for normality; Tukey robust approach for identification of outliers; reference range calculation with confidence intervals.

RESULTS

Reference ranges for measurement of myocardial T₁ were calculated, with confidence intervals, enabling comparison with clinically important differences. At 3 T: 1129 to 1301 msec at site 1 (n = 21) and 1160 to 1309 msec at site 2 (n = 59), and at 1.5 T at site 2: 933 to 1020 msec (male, n = 130) and 965 to 1054 msec (female, n = 68). The 3 T reference range from site 1 was successfully benchmarked against the 3 T reference range at site 2.

DATA CONCLUSION

Myocardial T₁ reference ranges can be properly characterized, enabling clinical comparison to a valid reference range with known confidence intervals, using methodology similar to that described in this report.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:771-778.

Accuracy, repeatability, and interplatform reproducibility of T1 quantification methods used for DCE-MRI: Results from a multicenter phantom study

PURPOSE

To determine the in vitro accuracy, test-retest repeatability, and interplatform reproducibility of T₁ quantification protocols used for dynamic contrast-enhanced MRI at 1.5 and 3 T.

METHODS

A T₁ phantom with 14 samples was imaged at eight centers with a common inversion-recovery spin-echo (IR-SE) protocol and a variable flip angle (VFA) protocol using seven flip angles, as well as site-specific protocols (VFA with different flip angles, variable repetition time, proton density, and Look-Locker inversion recovery). Factors influencing the accuracy (deviation from reference NMR T₁ measurements) and repeatability were assessed using general linear mixed models. Interplatform reproducibility was assessed using coefficients of variation.

RESULTS

For the common IR-SE protocol, accuracy (median error across platforms = 1.4-5.5%) was influenced predominantly by T₁ sample (P < 10^-6 ), whereas test-retest repeatability (median error = 0.2-8.3%) was influenced by the scanner (P < 10^-6 ). For the common VFA protocol, accuracy (median error = 5.7-32.2%) was influenced by field strength (P = 0.006), whereas repeatability (median error = 0.7-25.8%) was influenced by the scanner (P < 0.0001). Interplatform reproducibility with the common VFA was lower at 3 T than 1.5 T (P = 0.004), and lower than that of the common IR-SE protocol (coefficient of variation 1.5T: VFA/IR-SE = 11.13%/8.21%, P = 0.028; 3 T: VFA/IR-SE = 22.87%/5.46%, P = 0.001). Among the site-specific protocols, Look-Locker inversion recovery and VFA (2-3 flip angles) protocols showed the best accuracy and repeatability (errors < 15%).

CONCLUSIONS

The VFA protocols with 2 to 3 flip angles optimized for different applications achieved acceptable balance of extensive spatial coverage, accuracy, and repeatability in T₁ quantification (errors < 15%). Further optimization in terms of flip-angle choice for each tissue application, and the use of B₁ correction, are needed to improve the robustness of VFA protocols for T₁ mapping. Magn Reson Med 79:2564-2575, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Absence of Fibrosis and Inflammation by Cardiac Magnetic Resonance Imaging in Rheumatoid Arthritis Patients with Low to Moderate Disease Activity

OBJECTIVE

The prevalence of heart failure is increased 2-fold in patients with rheumatoid arthritis (RA); this is not explained by ischemic heart disease or other risk factors for heart failure. We hypothesized that in patients with RA without known heart disease, cardiac magnetic resonance imaging (cMRI) would detect altered cardiac structure, function, and fibrosis.

METHODS

We performed 1.5-T cMRI in 59 patients with RA and 56 controls frequency-matched for age, race, and sex, and compared cMRI indices of structure, function, and fibrosis [late gadolinium enhancement (LGE), native T1 mapping, and extracellular volume (ECV)] using Mann-Whitney U tests and linear regression, adjusting for age, race, and sex.

RESULTS

Most patients with RA had low to moderate disease activity [28-joint count Disease Activity Score-C-reactive protein median 3.16, interquartile range (IQR) 2.03-4.05], and 49% were receiving anti-tumor necrosis factor agents. Left ventricular (LV) mass, LV end-diastolic and -systolic volumes indexed to body surface area, and LV ejection fraction and left atrial size were not altered in RA compared to controls (all p > 0.05). Measures of fibrosis were not increased in RA: LGE was present in 2 patients with RA and 1 control subject; native T1 mapping was similar comparing RA and control subjects, and ECV (median, IQR) was lower (26.6%, 24.7-28.5%) in patients with RA compared to control subjects (27.5%, 25.4-30.4%, p = 0.03).

CONCLUSION

cMRI measures of cardiac structure and function were not significantly altered, and measures of fibrosis were similar or lower in RA patients with low to moderate disease activity compared to a matched control group.

Age and Gender Impact the Measurement of Myocardial Interstitial Fibrosis in a Healthy Adult Chinese Population: A Cardiac Magnetic Resonance Study

Background: Diffuse myocardial fibrosis is a common pathological process in many cardiovascular diseases. In order to determine disease, we must have standard normal imaging values. We investigated myocardial interstitial fibrosis of the left ventricle (LV) in a healthy population of Chinese adults and explored the impact of gender, age, and other physiological factors using a T1 mapping technique of cardiac magnetic resonance imaging (CMR).

Materials and Methods: We recruited 69 healthy adult Chinese subjects (35 males; age 18–76). LV function and global strain were obtained from functional imaging. T1 mapping was performed using a modified look-locker sequence. Global and segmental native T1 and extracellular volume (ECV) were calculated using dedicated software. Gender, age, and segmental variation of both native myocardial T1 and ECV of the LV were analyzed.

Results: The global myocardial native T1 and ECV of the LV in this Chinese adult healthy population was 1,202 ± 45 ms and 27 ± 3% at 3T field strength, respectively. Females had a higher myocardial native T1 and ECV of the LV compared to males [1,210 (1,188–1,264) ms vs. 1,182 (1,150–1,211) ms, P < 0.001; 28 ± 3 vs. 26 ± 3%, P = 0.027, respectively]. ECV in older group was higher than younger group [27 (26–29)% vs. 25 (24–29), P = 0.019]. The multi-variate linear regression analysis showed that only gender (Beta = −0.512, P < 0.001) was independently related with global native T1 of LV while gender (Beta = −0.278, P = 0.017) and age (Beta = 0.303, P = 0.010) were independently related with global ECV of LV. From the base to apex of the LV, myocardial native T1 (P = 0.020) and ECV (P < 0.001) significantly increased. Within the same slice of the LV, there were significant segmental variations of both myocardial native T1 (P < 0.001) and ECV (P < 0.001) values.

Conclusion: Gender and age have significant impacts on the imaging markers of myocardial interstitial fibrosis in healthy adult Chinese volunteers. Segmental variation of myocardial interstitial fibrosis was also observed.

Variability of cardiovascular magnetic resonance (CMR) T1 mapping parameters in healthy volunteers during long-term follow-up

Background

Myocardial T1 and extracellular volume (ECV) derived from cardiovascular MRIs are more and more widely accepted as important markers for diagnosis, risk prediction and monitoring of cardiac disease. Yet data regarding long-term stability of myocardial T1 mapping are lacking. The aim of this study was to investigate the long-term stability of native and postcontrast T1 mapping values in healthy volunteers.

Methods

18 strictly selected healthy volunteers (52±10 years, 12 men) were studied on a Philips Achieva 1.5 Tesla scanner. T1 relaxation times were measured before and 15 min after a bolus contrast injection of gadolinium diethylenetriamine penta-acetic acid (DTPA) (0.2 mmol/kg) using a single-breath-hold modified Look-Locker inversion recovery 3(3)3(3)5 sequence. ECV was calculated using native and postcontrast T1 times of myocardium and blood correcting for blood haematocrit. Exams were repeated 3.6±0.5 years later under the same conditions and using the same scan protocols.

Results

Cardiac biomarkers (high-sensitivity troponin T and N terminal pro-brain natriuretic peptide) remained unchanged, as well as left ventricular mass, and global and longitudinal function. No significant change occurred regarding native T1 times (1017±24 ms vs 1015±21 ms; P=0.6), postcontrast T1 times (426±38 ms vs 413±20 ms; P=0.13) or ECV (22%±2% vs 23%±2%; P=0.3). Native T1 time and ECV appeared to be better reproducible than postcontrast T1, resulting in lower coefficients of variation (ECV: 3.5%, native T1: 1.3%, postcontrast T1: 6.4%) and smaller limits of agreement (ECV: 2%/−2%, native T1: 39 ms/−35 ms, postcontrast T1: 85 ms/−59 ms).

Conclusions

During long-term follow-up, native T1 and ECV values are very robust markers, whereas postcontrast T1 results appear less stable.

Carotid Intraplaque Hemorrhage Imaging with Quantitative Vessel Wall T1 Mapping: Technical Development and Initial Experience

Purpose To develop a three-dimensional (3D) high-spatial-resolution time-efficient sequence for use in quantitative vessel wall T1 mapping. Materials and Methods A previously described sequence, simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) imaging, was extended by introducing 3D golden angle radial k-space sampling (GOAL-SNAP). Sliding window reconstruction was adopted to reconstruct images at different inversion delay times (different T1 contrasts) for voxelwise T1 fitting. Phantom studies were performed to test the accuracy of T1 mapping with GOAL-SNAP against a two-dimensional inversion recovery (IR) spin-echo (SE) sequence. In vivo studies were performed in six healthy volunteers (mean age, 27.8 years ± 3.0 [standard deviation]; age range, 24-32 years; five male) and five patients with atherosclerosis (mean age, 66.4 years ± 5.5; range, 60-73 years; five male) to compare T1 measurements between vessel wall sections (five per artery) with and without intraplaque hemorrhage (IPH). Statistical analyses included Pearson correlation coefficient, Bland-Altman analysis, and Wilcoxon rank-sum test with data permutation by subject. Results Phantom T1 measurements with GOAL-SNAP and IR SE sequences showed excellent correlation (R² = 0.99), with a mean bias of -25.8 msec ± 43.6 and a mean percentage error of 4.3% ± 2.5. Minimum T1 was significantly different between sections with IPH and those without it (mean, 371 msec ± 93 vs 944 msec ± 120; P = .01). Estimated T1 of normal vessel wall and muscle were 1195 msec ± 136 and 1117 msec ± 153, respectively. Conclusion High-spatial-resolution (0.8 mm isotropic) time-efficient (5 minutes) vessel wall T1 mapping is achieved by using the GOAL-SNAP sequence. This sequence may yield more quantitative reproducible biomarkers with which to characterize IPH and monitor its progression. ^© RSNA, 2017.

The influence of microvascular injury on native T1 and T2* relaxation values after acute myocardial infarction: implications for non-contrast-enhanced infarct assessment

Objectives

Native T1 mapping and late gadolinium enhancement (LGE) imaging offer detailed characterisation of the myocardium after acute myocardial infarction (AMI). We evaluated the effects of microvascular injury (MVI) and intramyocardial haemorrhage on local T1 and T2* values in patients with a reperfused AMI.

Methods

Forty-three patients after reperfused AMI underwent cardiovascular magnetic resonance imaging (CMR) at 4 [3-5] days, including native MOLLI T1 and T2* mapping, STIR, cine imaging and LGE. T1 and T2* values were determined in LGE-defined regions of interest: the MI core incorporating MVI when present, the core-adjacent MI border zone (without any areas of MVI), and remote myocardium.

Results

Average T1 in the MI core was higher than in the MI border zone and remote myocardium. However, in the 20 (47%) patients with MVI, MI core T1 was lower than in patients without MVI (MVI 1048±78ms, no MVI 1111±89ms, p=0.02). MI core T2* was significantly lower in patients with MVI than in those without (MVI 20 [18-23]ms, no MVI 31 [26-39]ms, p<0.001).

Conclusion

The presence of MVI profoundly affects MOLLI-measured native T1 values. T2* mapping suggested that this may be the result of intramyocardial haemorrhage. These findings have important implications for the interpretation of native T1 values shortly after AMI.

Key points

• Microvascular injury after acute myocardial infarction affects local T1 and T2* values.

• Infarct zone T1 values are lower if microvascular injury is present.

• T2* mapping suggests that low infarct T1 values are likely haemorrhage.

• T1 and T2* values are complimentary for correctly assessing post-infarct myocardium.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-017-5010-x) contains supplementary material, which is available to authorized users.

Effect of cellular and extracellular pathology assessed by T1 mapping on regional contractile function in hypertrophic cardiomyopathy

BACKGROUND

Regional contractile dysfunction is a frequent finding in hypertrophic cardiomyopathy (HCM). We aimed to investigate the contribution of different tissue characteristics in HCM to regional contractile dysfunction.

METHODS

We prospectively recruited 50 patients with HCM who underwent cardiovascular magnetic resonance (CMR) studies at 3.0 T including cine imaging, T1 mapping and late gadolinium enhancement (LGE) imaging. For each segment of the American Heart Association model segment thickness, native T1, extracellular volume (ECV), presence of LGE and regional strain (by feature tracking and tissue tagging) were assessed. The relationship of segmental function, hypertrophy and tissue characteristics were determined using a mixed effects model, with random intercept for each patient.

RESULTS

Individually segment thickness, native T1, ECV and the presence of LGE all had significant associations with regional strain. The first multivariable model (segment thickness, LGE and ECV) demonstrated that all strain parameters were associated with segment thickness (P < 0.001 for all) but not ECV. LGE (Beta 2.603, P = 0.024) had a significant association with circumferential strain measured by tissue tagging. In a second multivariable model (segment thickness, LGE and native T1) all strain parameters were associated with both segment thickness (P < 0.001 for all) and native T1 (P < 0.001 for all) but not LGE.

CONCLUSION

Impairment of contractile function in HCM is predominantly associated with the degree of hypertrophy and native T1 but not markers of extracellular fibrosis (ECV or LGE). These findings suggest that impairment of contractility in HCM is mediated by mechanisms other than extracellular expansion that include cellular changes in structure and function. The cellular mechanisms leading to increased native T1 and its prognostic significance remain to be established.

Cardiac MOLLI T1 mapping at 3.0 T: comparison of patient-adaptive dual-source RF and conventional RF transmission

To prospectively compare image quality and myocardial T₁ relaxation times of modified Look-Locker inversion recovery (MOLLI) imaging at 3.0 T (T) acquired with patient-adaptive dual-source (DS) and conventional single-source (SS) radiofrequency (RF) transmission. Pre- and post-contrast MOLLI T₁ mapping using SS and DS was acquired in 27 patients. Patient wise and segment wise analysis of T₁ times was performed. The correlation of DS MOLLI measurements with a reference spin echo sequence was analysed in phantom experiments. DS MOLLI imaging reduced T₁ standard deviation in 14 out of 16 myocardial segments (87.5%). Significant reduction of T₁ variance could be obtained in 7 segments (43.8%). DS significantly reduced myocardial T₁ variance in 16 out of 25 patients (64.0%). With conventional RF transmission, dielectric shading artefacts occurred in six patients causing diagnostic uncertainty. No according artefacts were found on DS images. DS image findings were in accordance with conventional T₁ mapping and late gadolinium enhancement (LGE) imaging. Phantom experiments demonstrated good correlation of myocardial T₁ time between DS MOLLI and spin echo imaging. Dual-source RF transmission enhances myocardial T₁ homogeneity in MOLLI imaging at 3.0 T. The reduction of signal inhomogeneities and artefacts due to dielectric shading is likely to enhance diagnostic confidence.

Role of T1 Mapping in Inherited Cardiomyopathies

T1 mapping by cardiovascular magnetic resonance is a rapidly evolving method for the quantitative assessment of tissue characteristics in cardiac disease. The myocardial T1 time can be measured without contrast (native T1) or following the administration of intravenous gadolinium-based contrast agent (post-contrast T1). By combining both of these measures, the myocardial extracellular volume fraction can be approximated. This value has been validated histologically in various inherited cardiomyopathies. Due to overlapping phenotypes, the diagnosis of inherited cardiomyopathy can at times be challenging. In this article we discuss when T1 mapping may be a useful tool in the differential diagnosis of cardiomyopathy. We also present evidence of when T1 mapping provides incremental risk stratification over other biomarkers.

Histologic validation of myocardial fibrosis measured by T1 mapping: a systematic review and meta-analysis

BACKGROUND

Myocardial fibrosis is being increasingly recognised as a common final pathway of a wide range of diseases. Thus, the development of an accurate and convenient method to evaluate myocardial fibrosis is of major importance. Although T1 mapping is a potential alternative for myocardial biopsy, validation studies are limited to small numbers and vary regarding technical facets, and include only a restricted number of disease. A systematic review and meta-analysis was conducted to objectively and comprehensively evaluate the performance of T1 mapping on the quantification of myocardial fibrosis using cardiovascular magnetic resonance (CMR).

METHODS

PubMed, EMBASE and the Cochrane Library databases were searched for studies applying T1 mapping to measure myocardial fibrosis and that validated the results via histological analysis. A pooled correlation coefficient between the CMR and histology measurements was used to evaluate the performance of the T1 mapping.

RESULTS

A total of 15 studies, including 308 patients who had CMR and myocardial biopsy were included and the pooled correlation coefficient between ECV measured by T1 mapping and biopsy for the selected studies was 0.884 (95% CI: 0.854, 0.914) and was not notably heterogeneous chi-squared = 7.44; P = 0.489 for the Q test and I^2 = 0.00%).

CONCLUSIONS

The quantitative measurement of myocardial fibrosis via T1 mapping is associated with a favourable overall correlation with the myocardial biopsy measurements. Further studies are required to determine the calibration of the T1 mapping results for the biopsy findings of different cardiomyopathies.

Accuracy, precision, and reproducibility of myocardial T1 mapping: A comparison of four T1 estimation algorithms for modified look-locker inversion recovery (MOLLI)

PURPOSE

To compare the accuracy and precision of four different T1 estimation algorithms for modified Look-Locker inversion recovery (MOLLI).

METHODS

Four T1 estimation algorithms, including the original fit, inversion group (IG) fit, instantaneous signal loss simulation (InSiL), and Bloch equation simulation with slice profile correction (BLESSPC) were studied. T1 estimation accuracy, precision, reproducibility, and sensitivity to heart rate (HR), flip angle (FA), and acquisition scheme (AcS) variations were compared in simulation, phantom, and volunteer studies.

RESULTS

T1 estimation accuracy of IG (-2.4% ± 3.9%) and original fit (-3.2% ± 1.4%) were worse than BLESSPC (0.2% ± 1.5%) and InSiL (-0.7% ± 2.1%). The original fit had the best precision for T1 from 409-1884 ms for the same FA (0.67% ± 0.16% versus 0.90% ± 0.23% using IG, 0.78% ± 0.11% using InSiL, 0.77% ± 0.12% using BLESSPC). BLESSPC generated the most consistent in vivo T1 values over different FAs and AcS, and the T1 estimation reproducibility was similar (P > 0.3) among the four methods when FA = 35°. When using FA = 50°, the reproducibility was significantly improved only when using BLESSPC (1.6% ± 0.9 versus 2.6% ± 1.9%, P < 0.05).

CONCLUSION

BLESSPC has superior accuracy and is the least sensitive to FA, HR, and AcS variations. T1 estimation using BLESSPC and FA = 50° is superior to conventional MOLLI with FA = 35° in accuracy and precision. Further clinical studies in varying pathological conditions are warranted to confirm our findings. Magn Reson Med 78:1746-1756, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Myocardial T1-mapping at 3T using saturation-recovery: reference values, precision and comparison with MOLLI

BACKGROUND

Myocardial T1-mapping recently emerged as a promising quantitative method for non-invasive tissue characterization in numerous cardiomyopathies. Commonly performed with an inversion-recovery (IR) magnetization preparation at 1.5T, the application at 3T has gained due to increased quantification precision. Alternatively, saturation-recovery (SR) T1-mapping has recently been introduced at 1.5T for improved accuracy. Thus, the purpose of this study is to investigate the robustness and precision of SR T1-mapping at 3T and to establish accurate reference values for native T1-times and extracellular volume fraction (ECV) of healthy myocardium.

METHODS

Balanced Steady-State Free-Precession (bSSFP) Saturation-Pulse Prepared Heart-rate independent Inversion-REcovery (SAPPHIRE) and Saturation-recovery Single-SHot Acquisition (SASHA) T1-mapping were compared with the Modified Look-Locker inversion recovery (MOLLI) sequence at 3T. Accuracy and precision were studied in phantom. Native and post-contrast T1-times and regional ECV were determined in 20 healthy subjects (10 men, 27 ± 5 years). Subjective image quality, susceptibility artifact rating, in-vivo precision and reproducibility were analyzed.

RESULTS

SR T1-mapping showed <4 % deviation from the spin-echo reference in phantom in the range of T1 = 100-2300 ms. The average quality and artifact scores of the T1-mapping methods were: MOLLI:3.4/3.6, SAPPHIRE:3.1/3.4, SASHA:2.9/3.2; (1: poor - 4: excellent/1: strong - 4: none). SAPPHIRE and SASHA yielded significantly higher T1-times (SAPPHIRE: 1578 ± 42 ms, SASHA: 1523 ± 46 ms), in-vivo T1-time variation (SAPPHIRE: 60.1 ± 8.7 ms, SASHA: 70.0 ± 9.3 ms) and lower ECV-values (SAPPHIRE: 0.20 ± 0.02, SASHA: 0.21 ± 0.03) compared with MOLLI (T1: 1181 ± 47 ms, ECV: 0.26 ± 0.03, Precision: 53.7 ± 8.1 ms). No significant difference was found in the inter-subject variability of T1-times or ECV-values (T1: p = 0.90, ECV: p = 0.78), the observer agreement (inter: p > 0.19; intra: p > 0.09) or consistency (inter: p > 0.07; intra: p > 0.17) between the three methods.

CONCLUSIONS

Saturation-recovery T1-mapping at 3T yields higher accuracy, comparable inter-subject, inter- and intra-observer variability and less than 30 % precision-loss compared to MOLLI.

Quantitative T1, T2, and T2* Mapping and Semi-Quantitative Neuromelanin-Sensitive Magnetic Resonance Imaging of the Human Midbrain

Purpose

Neuromelanin is a dark pigment granule present within certain catecholamine neurons of the human brain. Here, we aimed to clarify the relationship between contrast of neuromelanin-sensitive magnetic resonance imaging (MRI) and MR relaxation times using T₁, T₂, and T₂* mapping of the lower midbrain.

Methods

The subjects were 14 healthy volunteers (11 men and 3 women, mean age 29.9 ± 6.9 years). Neuromelanin-sensitive MRI was acquired using an optimized T₁-weighted two-dimensional (2D)-turbo spin-echo sequence. To quantitatively evaluate the relaxation time, 2D-image data for the T₁, T₂, and T₂* maps were also acquired. The regions of interest (substantia nigra pars compacta [SNc], superior cerebellar peduncles [SCP], cerebral peduncles [CP], and midbrain tegmentum [MT]) were manually drawn on neuromelanin-sensitive MRI to measure the contrast ratio (CR) and on relaxation maps to measure the relaxation times.

Results

The CR in the SNc was significantly higher than the CRs in the SCP and CP. Compared to the SCP and CP, the SNc had significantly higher T₁ relaxation times. Moreover, the SNc had significantly lower T₂ and T₂* relaxation times than the other three regions (SCP, CP, and MT). Correlation analyses showed no significant correlations between the CRs in the SNc, SCP, and CP and each relaxation time.

Conclusions

We demonstrated the relationship between the CR of neuromelanin-sensitive MRI and the relaxation times of quantitative maps of the human midbrain.

A medical device-grade T1 and ECV phantom for global T1 mapping quality assurance-the T1 Mapping and ECV Standardization in cardiovascular magnetic resonance (T1MES) program

BACKGROUND

T1 mapping and extracellular volume (ECV) have the potential to guide patient care and serve as surrogate end-points in clinical trials, but measurements differ between cardiovascular magnetic resonance (CMR) scanners and pulse sequences. To help deliver T1 mapping to global clinical care, we developed a phantom-based quality assurance (QA) system for verification of measurement stability over time at individual sites, with further aims of generalization of results across sites, vendor systems, software versions and imaging sequences. We thus created T1MES: The T1 Mapping and ECV Standardization Program.

METHODS

A design collaboration consisting of a specialist MRI small-medium enterprise, clinicians, physicists and national metrology institutes was formed. A phantom was designed covering clinically relevant ranges of T1 and T2 in blood and myocardium, pre and post-contrast, for 1.5 T and 3 T. Reproducible mass manufacture was established. The device received regulatory clearance by the Food and Drug Administration (FDA) and Conformité Européene (CE) marking.

RESULTS

The T1MES phantom is an agarose gel-based phantom using nickel chloride as the paramagnetic relaxation modifier. It was reproducibly specified and mass-produced with a rigorously repeatable process. Each phantom contains nine differently-doped agarose gel tubes embedded in a gel/beads matrix. Phantoms were free of air bubbles and susceptibility artifacts at both field strengths and T1 maps were free from off-resonance artifacts. The incorporation of high-density polyethylene beads in the main gel fill was effective at flattening the B 1 field. T1 and T2 values measured in T1MES showed coefficients of variation of 1 % or less between repeat scans indicating good short-term reproducibility. Temperature dependency experiments confirmed that over the range 15-30 °C the short-T1 tubes were more stable with temperature than the long-T1 tubes. A batch of 69 phantoms was mass-produced with random sampling of ten of these showing coefficients of variations for T1 of 0.64 ± 0.45 % and 0.49 ± 0.34 % at 1.5 T and 3 T respectively.

CONCLUSION

The T1MES program has developed a T1 mapping phantom to CE/FDA manufacturing standards. An initial 69 phantoms with a multi-vendor user manual are now being scanned fortnightly in centers worldwide. Future results will explore T1 mapping sequences, platform performance, stability and the potential for standardization.

Joint myocardial T1 and T2 mapping using a combination of saturation recovery and T2 -preparation

PURPOSE

To develop a heart-rate independent breath-held joint T1 -T2 mapping sequence for accurate simultaneous estimation of coregistered myocardial T1 and T2 maps.

METHODS

A novel preparation scheme combining both a saturation pulse and T2 -preparation in a single R-R interval is introduced. The time between these two pulses, as well as the duration of the T2 -preparation is varied in each heartbeat, acquiring images with different T1 and T2 weightings, and no magnetization dependence on previous images. Inherently coregistered T1 and T2 maps are calculated from these images. Phantom imaging is performed to compare the proposed maps with spin echo references. In vivo imaging is performed in ten subjects, comparing the accuracy and precision of the proposed technique to existing myocardial T1 and T2 mapping sequences of the same duration.

RESULTS

Phantom experiments show that the proposed technique provides accurate quantification of T1 and T2 values over a wide-range (T1 : 260 ms to 1460 ms, T2 : 40 ms to 200 ms). In vivo imaging shows that the proposed sequence quantifies T1 and T2 values similar to a saturation-based T1 mapping and a conventional breath-hold T2 mapping sequence, respectively.

CONCLUSION

The proposed sequence allows joint estimation of accurate and coregistered quantitative myocardial T1 and T2 maps in a single breath-hold. Magn Reson Med 76:888-896, 2016. © 2015 Wiley Periodicals, Inc.

Myocardial Mapping With Cardiac Magnetic Resonance: The Diagnostic Value of Novel Sequences

Cardiac magnetic resonance has evolved into a crucial modality for the evaluation of cardiomyopathy due to its ability to characterize myocardial structure and function. In the last few years, interest has increased in the potential of "mapping" techniques that provide direct and objective quantification of myocardial properties such as T1, T2, and T2* times. These approaches enable the detection of abnormalities that affect the myocardium in a diffuse fashion and/or may be too subtle for visual recognition. This article reviews the current state of myocardial T1 and T2-mapping in both health and disease.

Myocardial T1 mapping for patients with implanted cardiac devices using wideband inversion recovery spoiled gradient echo readout

PURPOSE

To develop and validate a technique for myocardial T1 mapping in patients with implantable cardioverter defibrillators (ICDs).

METHODS

A MOLLI-based pulse sequence, named Wideband-FLASH-MOLLI, was developed by incorporating a fast low angle shot (FLASH) readout and a wideband inversion pulse. The performance of Wideband-FLASH-MOLLI was evaluated using phantom studies and validated in eight healthy volunteers and ten patients with ICDs at 1.5 Tesla. Comparisons were made between Wideband-FLASH-MOLLI, FLASH-MOLLI, and bSSFP-MOLLI sequences.

RESULTS

In phantom studies, the maximum T1 estimation errors using Wideband-FLASH-MOLLI with and without an ICD were less than 3% for T1 range from 212 to 1673 ms. In all healthy volunteers, there was no significant native myocardial T1 estimation difference using Wideband-FLASH-MOLLI before and after the external attachment of an ICD to the body coil (1178 ± 27 ms versus 1174 ± 33 ms; P = 0.41). Due to the presence of an ICD, the magnitude images acquired using bSSFP-MOLLI and FLASH-MOLLI showed severe artifacts within the myocardium. In contrast, no or negligible device-induced artifacts were noted within the myocardial regions of the healthy volunteers or the patients with ICDs when using Wideband-FLASH-MOLLI.

CONCLUSION

This study demonstrates the feasibility of using Wideband-FLASH-MOLLI to mitigate image artifacts and to produce accurate myocardial T1 maps in patients with ICDs. Magn Reson Med 77:1495-1504, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Systolic MOLLI T1 mapping with heart-rate-dependent pulse sequence sampling scheme is feasible in patients with atrial fibrillation

BACKGROUND

T1 mapping enables assessment of myocardial characteristics. As the most common type of arrhythmia, atrial fibrillation (AF) is often accompanied by a variety of cardiac pathologies, whereby the irregular and usually rapid ventricle rate of AF may cause inaccurate T1 estimation due to mis-triggering and inadequate magnetization recovery. We hypothesized that systolic T1 mapping with a heart-rate-dependent (HRD) pulse sequence scheme may overcome this issue.

METHODS

30 patients with AF and 13 healthy volunteers were enrolled and underwent cardiovascular magnetic resonance (CMR) at 3 T. CMR was repeated for 3 patients after electric cardioversion and for 2 volunteers after lowering heart rate (HR). A Modified Look-Locker Inversion Recovery (MOLLI) sequence was acquired before and 15 min after administration of 0.1 mmol/kg gadopentetate dimeglumine. For AF patients, both the fixed 5(3)3/4(1)3(1)2 and the HRD sampling scheme were performed at diastole and systole, respectively. The HRD pulse sequence sampling scheme was 5(n)3/4(n)3(n)2, where n was determined by the heart rate to ensure adequate magnetization recovery. Image quality of T1 maps was assessed. T1 times were measured in myocardium and blood. Extracellular volume fraction (ECV) was calculated.

RESULTS

In volunteers with repeated T1 mapping, the myocardial native T1 and ECV generated from the 1st fixed sampling scheme were smaller than from the 1st HRD and 2nd fixed sampling scheme. In healthy volunteers, the overall native T1 times and ECV of the left ventricle (LV) in diastolic T1 maps were greater than in systolic T1 maps (P < 0.01, P < 0.05). In the 3 AF patients that had received electrical cardioversion therapy, the myocardial native T1 times and ECV generated from the fixed sampling scheme were smaller than in the 1st and 2nd HRD sampling scheme (all P < 0.05). In patients with AF (HR: 88 ± 20 bpm, HR fluctuation: 12 ± 9 bpm), more T1 maps with artifact were found in diastole than in systole (P < 0.01). The overall native T1 times and ECV of the left ventricle (LV) in diastolic T1 maps were greater than systolic T1 maps, either with fixed or HRD sampling scheme (all P < 0.05).

CONCLUSION

Systolic MOLLI T1 mapping with heart-rate-dependent pulse sequence scheme can improve image quality and avoid T1 underestimation. It is feasible and with further validation may extend clinical applicability of T1 mapping to patients with atrial fibrillation.

Myocardial T1 mapping at 3.0 tesla using an inversion recovery spoiled gradient echo readout and bloch equation simulation with slice profile correction (BLESSPC) T1 estimation algorithm

BACKGROUND

To develop an accurate and precise myocardial T1 mapping technique using an inversion recovery spoiled gradient echo readout at 3.0 Tesla (T).

THEORY AND METHODS

The modified Look-Locker inversion-recovery (MOLLI) sequence was modified to use fast low angle shot (FLASH) readout, incorporating a BLESSPC (Bloch Equation Simulation with Slice Profile Correction) T1 estimation algorithm, for accurate myocardial T1 mapping. The FLASH-MOLLI with BLESSPC fitting was compared with different approaches and sequences with regards to T1 estimation accuracy, precision and image artifact based on simulation, phantom studies, and in vivo studies of 10 healthy volunteers and three patients at 3.0 Tesla.

RESULTS

The FLASH-MOLLI with BLESSPC fitting yields accurate T1 estimation (average error = -5.4 ± 15.1 ms, percentage error = -0.5% ± 1.2%) for T1 from 236-1852 ms and heart rate from 40-100 bpm in phantom studies. The FLASH-MOLLI sequence prevented off-resonance artifacts in all 10 healthy volunteers at 3.0T. In vivo, there was no significant difference between FLASH-MOLLI-derived myocardial T1 values and "ShMOLLI+IE" derived values (1458.9 ± 20.9 ms versus 1464.1 ± 6.8 ms, P = 0.50); However, the average precision by FLASH-MOLLI was significantly better than that generated by "ShMOLLI+IE" (1.84 ± 0.36% variance versus 3.57 ± 0.94%, P < 0.001).

CONCLUSION

The FLASH-MOLLI with BLESSPC fitting yields accurate and precise T1 estimation, and eliminates banding artifacts associated with bSSFP at 3.0T.

Review of Journal of Cardiovascular Magnetic Resonance 2014

There were 102 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2014, which is a 6% decrease on the 109 articles published in 2013. The quality of the submissions continues to increase. The 2013 JCMR Impact Factor (which is published in June 2014) fell to 4.72 from 5.11 for 2012 (as published in June 2013). The 2013 impact factor means that the JCMR papers that were published in 2011 and 2012 were cited on average 4.72 times in 2013. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality papers to JCMR for publication.

Histological Validation of measurement of diffuse interstitial myocardial fibrosis by myocardial extravascular volume fraction from Modified Look-Locker imaging (MOLLI) T1 mapping at 3 T

BACKGROUND

Gadolinium (Gd) Extracellular volume fraction (ECV) by Cardiovascular Magnetic Resonance (CMR) has been proposed as a non-invasive method for assessment of diffuse myocardial fibrosis. Yet only few studies used 3 T CMR to measure ECV, and the accuracy of ECV measurements at 3 T has not been established. Therefore the aims of the present study were to validate measurement of ECV by MOLLI T1 mapping by 3 T CMR against fibrosis measured by histopathology. We also evaluated the recently proposed hypothesis that native-T1 mapping without contrast injection would be sufficient to detect fibrosis.

METHODS

31 patients (age = 58 ± 17 years, 77% men) with either severe aortic stenosis (n = 12) severe aortic regurgitation (n = 9) or severe mitral regurgitation (n = 10), all free of coronary artery disease, underwent 3 T-CMR with late gadolinium enhancement (LGE) and pre- and post-contrast MOLLI T1 mapping and ECV computation, prior to valve surgery. LV biopsies were performed at the time of surgery, a median 13 [1-30] days later, and stained with picrosirius red. Pre-, and post-contrast T1 values, ECV, and amount of LGE were compared against magnitude of fibrosis by histopathology by Pearson correlation coefficients.

RESULTS

The average amount of interstitial fibrosis by picrosirius red staining in biopsy samples was 6.1 ± 4.3%. ECV computed from pre-post contrast MOLLI T1 time changes was 28.9 ± 5.5%, and correlated (r = 0.78, p < 0.001) strongly with the magnitude of histological fibrosis. By opposition, neither amount of LGE (r = 0.17, p = 0.36) nor native pre-contrast myocardial T1 time (r = -0.18, p = 0.32) correlated with fibrosis by histopathology.

CONCLUSIONS

ECV determined by 3 T CMR T1 MOLLI images closely correlates with histologically determined diffuse interstitial fibrosis, providing a non-invasive estimation for quantification of interstitial fibrosis in patients with valve diseases. By opposition, neither non-contrast T1 times nor the amount of LGE were indicative of the magnitude of diffuse interstitial fibrosis measured by histopathology.

Quantification and significance of diffuse myocardial fibrosis and diastolic dysfunction in childhood hypertrophic cardiomyopathy

The purpose of this study was to evaluate the presence of diffuse myocardial fibrosis in children and adolescents with hypertrophic cardiomyopathy (HCM) and to assess associations with echocardiographic and clinical parameters of disease. While a common end point in adults with HCM, it is unclear whether diffuse myocardial fibrosis occurs early in the disease. Cardiac magnetic resonance (CMR) estimation of myocardial post-contrast longitudinal relaxation time (T1) is an increasingly used method to estimate diffuse fibrosis. T1 measurements were taken using standard multi-breath-hold spoiled gradient echo phase-sensitive inversion-recovery CMR before and 15 min after the injection of gadolinium. The tissue-blood partition coefficient was calculated as a function of the ratio of T1 change of myocardium compared with blood. An echocardiogram and blood brain natriuretic peptide (BNP) levels were obtained on the day of the CMR. Twelve controls (mean age 12.8 years; 7 male) and 28 patients with HCM (mean age 12.8 years; 21 male) participated. The partition coefficient for both septal (0.27 ± 0.17 vs. 0.13 ± 0.09; p = 0.03) and lateral walls (0.22 ± 0.09 vs. 0.07 ± 0.10; p < 0.001) was increased in patients compared with controls. Eight patients had overt areas of late gadolinium enhancement (LGE). These patients did not show increased partition coefficient compared with those without LGE (0.27 ± 0.15 vs. 0.27 ± 0.19 and 0.22 ± 0.09 vs. 0.22 ± 0.09; p = 0.95 and 0.98, respectively). However, patients who were symptomatic (dyspnea, arrhythmia and/or chest pain) had higher lateral wall partition coefficient than asymptomatic HCM patients (0.27 ± 0.08 vs. 0.17 ± 0.08; p = 0.006). Similarly, patients with raised BNP (>100 pg/ml) had raised lateral wall coefficients (0.27 ± 0.07 vs. 0.20 ± 0.07; p = 0.03), as did those with traditional risk factors for sudden death (0.27 ± 0.06 vs. 0.18 ± 0.08; p = 0.007). Diffuse fibrosis, measured by the partition coefficient technique, is demonstrable in children and adolescents with HCM. Markers of fibrosis show an association with symptoms and raised serum BNP. Further study of the prognostic implication of this technique in young patients with HCM is warranted.

Myocardial T1 and T2 mapping in diastolic and systolic phase

The aim of this study was to evaluate the regional (i.e. myocardial segments) variability as well as the overall image quality of cardiac T1 and T2 maps obtained in diastole and in systole. In 22 healthy subjects (group-1), diastolic T1 and T2 maps were obtained at 1.5 T in short-axis view at basal, mid-ventricular and apical level, as well as in 4-chamber (4 ch) and in 2-chamber (2 ch) views. In another group of 25 patients (group-2), the maps were obtained in both diastole and systole. In the group-1, 15.4% of myocardial segments in T1 maps and 0.8% of myocardial segments in T2 maps, mainly located at apical level, showed relevant artifacts and/or partial-volume effect and had to be discarded. We found no significant difference in T1 values among basal, mid-ventricular and apical segments. T2 values at apical level were significantly higher than at basal and mid-ventricular level (short-axis, p < 0.0001; 4 ch, p < 0.009; 2 ch, p = 0.0002 at ANOVA tests). In the group-2, 21.1%/5.3% and 4.0%/0.8% of segments showed relevant artifacts in diastolic/systolic T1 and T2 maps, respectively. Apical T2 values were significantly lower in systole than in diastole. In systole, there were no significant differences in T1/T2 among basal, mid-ventricular and apical segments. The overall quality of T1 and T2 maps drops in apical segments. This could be problematic when evaluating focal myocardial changes. The acquisition in systole increases the number of evaluable segments.

Review of Journal of Cardiovascular Magnetic Resonance 2013

There were 109 articles published in the Journal of Cardiovascular Magnetic Resonance (JCMR) in 2013, which is a 21% increase on the 90 articles published in 2012. The quality of the submissions continues to increase. The editors are delighted to report that the 2012 JCMR Impact Factor (which is published in June 2013) has risen to 5.11, up from 4.44 for 2011 (as published in June 2012), a 15% increase and taking us through the 5 threshold for the first time. The 2012 impact factor means that the JCMR papers that were published in 2010 and 2011 were cited on average 5.11 times in 2012. The impact factor undergoes natural variation according to citation rates of papers in the 2 years following publication, and is significantly influenced by highly cited papers such as official reports. However, the progress of the journal's impact over the last 5 years has been impressive. Our acceptance rate is <25% and has been falling because the number of articles being submitted has been increasing. In accordance with Open-Access publishing, the JCMR articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. For this reason, the Editors have felt that it is useful once per calendar year to summarize the papers for the readership into broad areas of interest or theme, so that areas of interest can be reviewed in a single article in relation to each other and other recent JCMR articles. The papers are presented in broad themes and set in context with related literature and previously published JCMR papers to guide continuity of thought in the journal. We hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.