Myocardial T1 values in healthy volunteers measured with saturation method using adaptive recovery times for T1 mapping (SMART1Map) at 1.5 T and 3 T

A Framework for Simulating Cardiac MR Images With Varying Anatomy and Contrast

One of the limiting factors for the development and adoption of novel deep-learning (DL) based medical image analysis methods is the scarcity of labeled medical images. Medical image simulation and synthesis can provide solutions by generating ample training data with corresponding ground truth labels. Despite recent advances, generated images demonstrate limited realism and diversity. In this work, we develop a flexible framework for simulating cardiac magnetic resonance (MR) images with variable anatomical and imaging characteristics for the purpose of creating a diversified virtual population. We advance previous works on both cardiac MR image simulation and anatomical modeling to increase the realism in terms of both image appearance and underlying anatomy. To diversify the generated images, we define parameters: 1)to alter the anatomy, 2) to assign MR tissue properties to various tissue types, and 3) to manipulate the image contrast via acquisition parameters. The proposed framework is optimized to generate a substantial number of cardiac MR images with ground truth labels suitable for downstream supervised tasks. A database of virtual subjects is simulated and its usefulness for aiding a DL segmentation method is evaluated. Our experiments show that training completely with simulated images can perform comparable with a model trained with real images for heart cavity segmentation in mid-ventricular slices. Moreover, such data can be used in addition to classical augmentation for boosting the performance when training data is limited, particularly by increasing the contrast and anatomical variation, leading to better regularization and generalization. The database is publicly available at https://osf.io/bkzhm/ and the simulation code will be available at https://github.com/sinaamirrajab/CMRI.

Diffuse Myocardial Fibrosis at Cardiac MRI in Young Adults Born Prematurely: A Cross-sectional Cohort Study

Purpose

To measure native T1 values, a marker of diffuse fibrosis, by using cardiac MRI (CMR) in young adults born prematurely.

Materials and Methods

This secondary analysis of a prospective cohort study included young adults born moderately to extremely preterm and age-matched, term-born participants. CMR was performed with a 3.0-T imager that included cine imaging for the quantification of left ventricular (LV) and right ventricular (RV) volumes and function and native saturation recovery T1 mapping for the assessment of diffuse myocardial fibrosis. Values between preterm and term were compared by using the Student t test. Associations between T1 values and other variables were analyzed by using linear regression and multivariate regression.

Results

Of the 50 young-adult participants, 32 were born preterm (mean age, 25.8 years ± 4.2 [SD]; 23 women) and 18 were born at term (mean age, 26.2 years ± 5.4; 10 women). Native T1 values were significantly higher in participants born preterm than in participants born at term (1477 msec ± 77 vs 1423 msec ± 71, respectively; unadjusted P = .0019). Native T1 values appeared to be positively associated with indexed LV end-diastolic and end-systolic volumes (β = 2.1, standard error = 0.7 and β = 3.8, standard error = 1.2, respectively), the RV end-diastolic volume index (β = 1.3, standard error = 0.6), and the LV mass index (β = 2.5, standard error = 0.9). Higher T1 values may be associated with reduced cardiac systolic strain measures and diastolic strain measures. Five-minute Apgar scores were inversely associated with native T1 values.

Conclusion

Young adults born moderately to extremely preterm exhibited significantly higher native T1 values than age-matched, term-born young adults.

Keywords: MRI, Cardiac, Heart, Left Ventricle, Cardiomyopathies

Clinical trial registration no. NCT03245723

Published under a CC BY 4.0 license

Supplemental material is available for this article.

The Combination of MR Elastography and Proton Density Fat Fraction Improves Diagnosis of Nonalcoholic Steatohepatitis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is rapidly increasing worldwide. It is subdivided into nonalcoholic fatty liver (NAFL) and the more aggressive form, nonalcoholic steatohepatitis (NASH), which carries a higher risk of developing fibrosis and cirrhosis. There is currently no reliable non-invasive method for differentiating NASH from NAFL.

PURPOSE

To investigate the ability of magnetic resonance imaging (MRI)-based imaging biomarkers to diagnose NASH and moderate fibrosis as well as assess their repeatability.

STUDY TYPE

Prospective.

SUBJECTS

Sixty-eight participants (41% women) with biopsy-proven NAFLD (53 NASH and 15 NAFL). Thirty participants underwent a second MRI in order to assess repeatability.

FIELD STRENGTH/SEQUENCE

3.0 T; MR elastography (MRE) (a spin-echo echo-planar imaging [SE-EPI] sequence with motion-encoding gradients), MR proton density fat fraction (PDFF) and R2* mapping (a multi-echo three-dimensional gradient-echo sequence), T1 mapping (a single-point saturation-recovery technique), and diffusion-weighted imaging (SE-EPI sequence).

ASSESSMENT

Quantitative MRI measurements were obtained and assessed alone and in combination with biochemical markers (cytokeratin-18 [CK18] M30, alanine transaminase [ALT], and aspartate transaminase [AST]) using logistic regression models. Models that could differentiate between NASH and NAFL and between moderate to advanced fibrosis (F2-4) and no or mild fibrosis (F0-1), based on the histopathological results, were identified.

STATISTICAL TESTS

Independent samples t-test, Pearson's chi-squared test, area under the receiver operating characteristic curve (AUROC), Spearman's correlation, intra-individual coefficient of variation, and intraclass correlation coefficient (ICC). Statistical significance was set at P < 0.05.

RESULTS

There was a significant difference between the NASH and NAFL groups with liver stiffness assessed with MRE, CK18 M30, and ALT, with an AUROC of 0.74, 0.76, and 0.70, respectively. Both MRE and PDFF contributed significantly to a bivariate model for diagnosing NASH (AUROC = 0.84). MRE could significantly differentiate between F2-4 and F0-1 (AUROC = 0.74). A model combining MRE with AST improved the diagnosis of F2-4 (AUROC = 0.83). The ICC for repeatability was 0.94 and 0.99 for MRE and PDFF, respectively.

DATA CONCLUSION

MRE can potentially diagnose NASH and differentiate between fibrosis stages. Combining MRE with PDFF improves the diagnosis of NASH.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Preliminary study: myocardial T1 relaxation time in patients with ischemic findings and normal findings on coronary angiography

OBJECTIVE

The aim of this study is to evaluate the myocardium structure in patients with chest pain who were determined to have moderate and/or high risk for cardiac ischemic heart disease (IHD) but who had normal findings on conventional coronary angiography by using native cardiac magnetic resonance imaging (CMRI) T1 mapping and comparing with healthy volunteers.

METHODS

A total of 50 patients and 30 healthy volunteers who underwent CMRI were included in our prospective study. Patients whose clinical findings were compatible with stable angina pectoris, with moderate and/or high risk for IHD, but whose conventional coronary angiography was normal, were our patient group. Native T1 values were measured for 17 myocardial segments (segmented based on American Heart Association recommendations) by two radiologists independently. The data obtained were statistically compared with the sample t-test.

RESULTS

Myocardial native T1 values were found to be significantly prolonged in the patient group compared with the control group (p<0.05). Inter-observer reliability for native T1 value measurements of groups was high for both patient and control groups (α = 0.92 for the patient group and 0.96 for the control group).

CONCLUSION

Findings suggestive of ischemia were detected by T1 mapping in the myocardium of our patients. For this reason, it is recommended that this patient group should be included in early diagnosis and close follow-up assessments for IHD.

Myocardial T1 mapping using SMART1 Map and MOLLI mapping in asymptomatic patients with recent extracardiac sarcoidosis

INTRODUCTION

Sarcoidosis is a systemic granulomatous disease affecting in particular the respiratory tract. Cardiac magnetic resonance (CMR), including a measurement of T₁ relaxation time, could potentially detect early stadia of sarcoidosis of the heart. The study aims to assess T₁ mapping in the detection of early cardiac involvement in asymptomatic patients with sarcoidosis.

METHODS

One hundred and twenty patients with extracardiac sarcoidosis and without any heart disease history were included. One hundred and thirteen of them underwent a CMR examination. The mean time from the diagnosis of sarcoidosis was 0.8 (0.2-3.3) years. Cine images for the assessment of left ventricular (LV) functional parameters and pre- and post-contrast saturation method using adaptive recovery times for cardiac T₁ mapping (SMART₁ Map) and modified Look-Locker inversion recovery (MOLLI) images were acquired for the assessment of native T₁ relaxation time and extracellular volume (ECV). The measured parameters were compared between sarcoidosis patients and 22 controls.

RESULTS

The sarcoidosis patients had normal global and regional systolic LV function-LV ejection fraction 65 ± 5% versus 66 ± 7% (p NS). The mean native T₁ relaxation times were not prolonged-1465 ± 93 ms versus 1480 ± 88 ms (p NS) measured by SMART₁ Map and 1317 ± 60 ms versus 1313 ± 83 ms (p NS) measured using a MOLLI sequence. Similarly, the mean ECV values did not increase-16.9 ± 3.9% versus 17.9 ± 3.7% (p NS) measured by SMART₁ Map and 30.9 ± 2.9% versus 31.6 ± 8.3% (p NS) measured using a MOLLI sequence.

CONCLUSION

Myocardial native T₁ relaxation times were not prolonged and ECV was not increased in asymptomatic patients with extracardiac sarcoidosis.

Normal myocardial native T1 values in children using single-point saturation recovery and modified look-locker inversion recovery (MOLLI)

BACKGROUND

T₁ mapping is useful to quantify diffuse myocardial processes such as fibrosis, edema, storage disorders, or hemochromatosis. Normal pediatric myocardial T₁ values are scarce using modified Look-Locker inversion recovery (MOLLI) sequences and unavailable using Smart1Map, a single-point saturation recovery sequence that measures true T₁ .

PURPOSE/HYPOTHESIS

To establish normal pediatric myocardial T₁ values by Smart1Map and to compare them with T₁ by MOLLI.

STUDY TYPE

Prospective cohort study.

SUBJECTS

Thirty-four children and adolescents aged 8-18 years (14 males) without cardiovascular or inflammatory diseases.

FIELD STRENGTH/SEQUENCES

1.5T, MOLLI, Smart1Map.

ASSESSMENT

Mean T₁ values of the left ventricular myocardium, the interventricular septum, and the blood pool were measured with MOLLI and Smart1Map in basal, mid-ventricular, and apical short axis slices.

STATISTICAL TESTS

T₁ values were compared between locations and methods by paired samples t-tests, Wilcoxon signed ranks test, repeated-measures analysis of variance (ANOVA), or Friedman's test. Pearson's correlation coefficient was calculated. For interobserver variability, intraclass correlation coefficients and coefficients of variation were calculated, and Bland-Altman analyses were performed.

RESULTS

T₁ values were longer by Smart1Map than by MOLLI in all measured locations (myocardium: 1191-1221 vs. 990-1042 msec; all P < 0.001). T₁ in basal vs. mid-ventricular slices differed both by MOLLI and by Smart1Map for myocardium and for blood (all P < 0.001). Myocardial T₁ did not correlate with age, heart rate, right or left ventricular ejection fraction (all P > 0.05) by either method. Septal vs. total myocardial T₁ values in each slice did not differ by MOLLI (basal P = 0.371; mid-ventricular P = 0.08; apical P = 0.378) nor by Smart1Map (basal P = 0.056; mid-ventricular P = 0.918; apical P = 0. 392), after artifacts had been carefully excluded.

DATA CONCLUSION

We established pediatric normal native T₁ values using the Smart1Map sequence and compared the results with T₁ mapping with MOLLI. Septal T₁ values did not differ from total myocardial T₁ values in each of the myocardial slices.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:897-903.