Observation of magnetic structural universality and jamming transition with NMR.

Nuclear magnetic resonance (NMR) has been instrumental in deciphering the structure of proteins. Here we show that transverse NMR relaxation, through its time-dependent relaxation rate, is distinctly sensitive to the structure of complex materials or biological tissues at the mesoscopic scale, from micrometers to tens of micrometers. Based on the ideas of universality, we show analytically and numerically that the time-dependent transverse relaxation rate approaches its long-time limit in a power-law fashion, with the dynamical exponent reflecting the universality class of mesoscopic magnetic structure.

Cardiac Magnetic Resonance Strain in Beta Thalassemia Major Correlates with Cardiac Iron Overload.

Background: Beta thalassemia major (Beta-TM) is an inherited condition which presents at around two years of life. Patients with Beta-;TM may develop cardiac iron toxicity secondary to transfusion dependence. Cardiovascular magnetic resonance (CMR) T2*, a technique designed to quantify myocardial iron deposition, is a driving component of disease management.

Cardiac MRI Myocardial Functional and Tissue Characterization Detects Early Cardiac Dysfunction in a Mouse Model of Chemotherapy-Induced Cardiotoxicity.

Background: Doxorubicin and doxorubicin-trastuzumab combination chemotherapy have been associated with cardiotoxicity that eventually leads to heart failure and may limit dose-effective cancer treatment. Current diagnostic strategies rely on decreased ejection fraction (EF) to diagnose cardiotoxicity.

Purpose: The aim of this study is to explore the potential of cardiac MR (CMR) imaging to identify imaging biomarkers in a mouse model of chemotherapy-induced cardiotoxicity.

Autocalibrated cardiac tissue phase mapping with multiband imaging and k-t acceleration.

Purpose: To develop an autocalibrated multiband (MB) CAIPIRINHA acquisition scheme with in-plane k-t acceleration enabling multislice three-directional tissue phase mapping in one breath-hold.

Methods: A k-t undersampling scheme was integrated into a time-resolved electrocardiographic-triggered autocalibrated MB gradient-echo sequence. The sequence was used to acquire data on 4 healthy volunteers with MB factors of two (MB2) and three (MB3), which were reconstructed using a joint reconstruction algorithm that tackles both k-t and MB acceleration.

Evaluating Biventricular Myocardial Velocity and Interventricular Dyssynchrony in Adult Patients During the First Year After Heart Transplantation.

Background: Magnetic resonance tissue phase mapping (TPM) measures three-directional myocardial velocities of the left and right ventricle (LV, RV). This noninvasive technique may supplement endomyocardial biopsy (EMB) in monitoring grafts post-heart transplantation (HTx).

Purpose: To assess biventricular myocardial velocity alterations in grafts and investigate the relationship between velocities and acute cellular rejection (ACR) episodes.

Altered regional myocardial velocities by tissue phase mapping and feature tracking in pediatric patients with hypertrophic cardiomyopathy.

Background: Hypertrophic cardiomyopathy (HCM) is associated with heart failure, atrial fibrillation and sudden death. Reduced myocardial function has been reported in HCM despite normal left ventricular (LV) ejection fraction. Additionally, LV fibrosis is associated with elevated T1 and might be an outcome predictor.

Myocardial velocity, intra-, and interventricular dyssynchrony evaluated by tissue phase mapping in pediatric heart transplant recipients.

Background: Endomyocardial biopsy (EMB) is the standard method for detecting allograft rejection in pediatric heart transplants (Htx). As EMB is invasive and carries a risk of complications, there is a need for a noninvasive alternative for allograft monitoring.

Purpose: To quantify left and right ventricular (LV & RV) peak velocities, velocity twist, and intra-/interventricular dyssynchrony using tissue phase mapping (TPM) in pediatric Htx compared with controls, and to explore the relationship between global cardiac function parameters and the number of rejection episodes to these velocities and intra-/interventricular dyssynchrony.

Larmor frequency dependence on structural anisotropy of magnetically heterogeneous media.

The effect of anisotropic magnetic microstructure on the measurable Larmor frequency offset is investigated in media with heterogeneous magnetic susceptibility using Monte Carlo simulations. The focus is on the transition between the regimes of fast and slow diffusion of NMR-reporting molecules. Simulations demonstrate a perfect agreement with the previously developed analytic theory for fast diffusion.

Comprehensive MR Analysis of Cardiac Function, Aortic Hemodynamics and Left Ventricular Strain in Pediatric Cohort with Isolated Bicuspid Aortic Valve.

Bicuspid aortic valve (BAV) disease demonstrates a range of clinical presentations and complications. We aim to use cardiac MRI (CMR) to evaluate left ventricular (LV) parameters, myocardial strain and aortic hemodynamics in pediatric BAV patients with and without aortic stenosis (AS) or regurgitation (AR) compared to tricuspid aortic valve (TAV) controls. We identified 58 pediatric BAV patients without additional cardiovascular pathology and 25 healthy TAV controls (15.

Impact of age and cardiac disease on regional left and right ventricular myocardial motion in healthy controls and patients with repaired tetralogy of fallot.

The assessment of both left (LV) and right ventricular (RV) motion is important to understand the impact of heart disease on cardiac function. The MRI technique of tissue phase mapping (TPM) allows for the quantification of regional biventricular three-directional myocardial velocities. The goal of this study was to establish normal LV and RV velocity parameters across a wide range of pediatric to adult ages and to investigate the feasibility of TPM for detecting impaired regional biventricular function in patients with repaired tetralogy of Fallot (TOF).

Autocalibrated multiband CAIPIRINHA with through-time encoding: Proof of principle and application to cardiac tissue phase mapping.

Purpose: In conventional multiband (MB) CAIPIRINHA, additional reference scans are acquired to allow the separation of the excited slices. In this study, an acquisition-reconstruction technique that makes use of the MB data to calculate these reference data is presented. The method was integrated into a 2D time-resolved phase-contrast MR sequence used to assess velocities of the myocardium.

The larmor frequency shift in magnetically heterogeneous media depends on their mesoscopic structure.

Purpose: Recent studies have addressed the determination of the NMR precession frequency in biological tissues containing magnetic susceptibility differences between cell types. The purpose of this study is to investigate the dependence of the precession frequency on medium microstructure using a simple physical model.

Theory: This dependence is governed by diffusion of NMR-visible molecules in magnetically heterogeneous microenvironments.