Quantitative magnetic resonance imaging of the atrioventricular conduction axis based on the rotating-frame relaxation maps: Comparison with T, T, and magnetization transfer.

Background: Noninvasive visualization and characterization of the atrioventricular conduction axis (AVCA) can help avoid iatrogenic injury and improve the accuracy of heart rhythm therapy guidance.

Objective: This study aimed to identify the AVCA structure using noninvasive rotating-frame relaxation-time mappings (relaxation along a fictitious field in the second rotating-frame relaxation time [T] and longitudinal rotating-frame relaxation time [T]) in ex vivo swine hearts.

Methods: Ex vivo swine heart tissue blocks were scanned on a 3T clinical magnetic resonance imaging system.

Orientation-Independent T2 Mapping Enhances MRI-Based Cartilage Characterization.

Purpose: Quantitative T2 mapping is an important MRI method for assessing degenerative changes in articular cartilage. Recently, in a measurement setup with automated sample re-orientation, it was demonstrated that T2 can be split into its orientation-independent components. This quantitative MRI study aims to assess the diagnostic significance of the automated approach with ex vivo human cartilage.

Compressed sensing acceleration of radial 3-D alternating Look-Locker mapping.

Purpose: To determine how various compressed sensing (CS) models can accelerate alternating Look-Locker mapping.

Methods: An alternating Look-Locker acquisition was retrospectively accelerated by factors of 1-12. The data was reconstructed into 12 images with multiple CS models, which utilized combinations of spatial total variation, locally low-rank regularization, and subspace constraints.

Correlations of T1ρ With Properties of Articular Cartilage Depend on the Spin-Lock Amplitude and Orientation of the Sample.

Various findings on the correlations of the continuous wave (CW-) T1ρ relaxation with properties of articular cartilage have been reported, suggesting its potential for cartilage diagnostics. The aim of the study was to combine all the previously reported aspects and investigate the association of CW-T1ρ relaxation time in healthy bovine cartilage to different properties of cartilage with a range of spin-lock amplitudes and cartilage orientations. Bovine cartilage-bone plugs (n = 11) were imaged in four orientations at 9.

Effects of collagen and chondroitin sulfate on relaxation at multiple magnetic field strengths.

Purpose: To elucidate the connection between MRI relaxation properties of articular cartilage and tissue composition, in terms of collagen and chondroitin sulfate (CS). Additional aims were to determine the effect of different magnetic field strengths, as well as the effect of concentrations of the components on relaxation properties.

Methods: A series of MRI phantoms consisting of gels containing collagen and chondroitin sulfate were prepared with final concentrations of collagen in the range 20-60 mg/g and the CS concentration in the range 0-40 mg/g.

imaging of subacute myocardial infarction with ultra-short echo time 3D quantitative T- and T -mapping magnetic resonance imaging in mice.

Aims: The aim of this study was to develop an ultra-short echo time 3D magnetic resonance imaging (MRI) method for imaging subacute myocardial infarction (MI) quantitatively and in an accelerated way. Here, we present novel 3D T- and T -weighted Multi-Band SWeep Imaging with Fourier Transform and Compressed Sensing (MB-SWIFT-CS) imaging of subacute MI in mice hearts .

Methods And Results: Relaxation time-weighted and under-sampled 3D MB-SWIFT-CS MRI were tested with manganese chloride (MnCl) phantom and mice MI model.

An Automated and Robust Tool for Musculoskeletal and Finite Element Modeling of the Knee Joint.

Objective: To develop and assess an automatic and robust knee musculoskeletal finite element (MSK-FE) modeling pipeline.

Methods: Magnetic resonance images (MRIs) were used to train nnU-Net networks for auto-segmentation of knee bones (femur, tibia, patella, and fibula), cartilages (femur, tibia, and patella), menisci, and major knee ligaments. Two different MRI sequences were used to broaden applicability.

Anisotropy of T and T relaxation time in articular cartilage at 3 T.

Purpose: The anisotropy of R and R relaxation rates in articular cartilage contains information about the collagenous structure of the tissue. Here we determine and study the anisotropic and isotropic components of T and T relaxation parameters in articular cartilage with a clinical 3T MRI device. Furthermore, a visual representation of the topographical variation in anisotropy is given via anisotropy mapping.

Non-invasive assessment and visualization of Phytophthora cactorum infection in strawberry crowns using quantitative magnetic resonance imaging.

Phytophthora cactorum is an oomycete species that causes enormous losses on horticultural crops, including strawberries. The purpose of this work was to investigate the alterations caused by P. cactorum inoculation in hydroponically grown strawberry plantlets (Fragaria × ananassa Duch.

Epiphyseal cartilage vascular architecture at the distal humeral osteochondritis dissecans predilection site in juvenile pigs.

Failure of endochondral ossification due to interruption of the vascular supply to the epiphyseal cartilage is a critical step in the development of osteochondritis dissecans (OCD). Herein we describe the vascular architecture of the distal humeral epiphyseal cartilage in pigs and identify characteristic features that have been associated with sites predisposed to OCD development across species. Distal humeral specimens were harvested from pigs (n = 5, ages = 1, 10, 18, 30, and, 42 days old) and imaged at 9.

Fast Compressed Sensing of 3D Radial T Mapping with Different Sparse and Low-Rank Models.

Knowledge of the relative performance of the well-known sparse and low-rank compressed sensing models with 3D radial quantitative magnetic resonance imaging acquisitions is limited. We use 3D radial T relaxation time mapping data to compare the total variation, low-rank, and Huber penalty function approaches to regularization to provide insights into the relative performance of these image reconstruction models. Simulation and ex vivo specimen data were used to determine the best compressed sensing model as measured by normalized root mean squared error and structural similarity index.

3D T relaxation time measurements in an equine model of subtle post-traumatic osteoarthritis using MB-SWIFT.

The aim of this study is to assess whether articular cartilage changes in an equine model of post-traumatic osteoarthritis (PTOA), induced by surgical creation of standard (blunt) grooves, and very subtle sharp grooves, could be detected with ex vivo T relaxation time mapping utilizing three-dimensional (3D) readout sequence with zero echo time. Grooves were made on the articular surfaces of the middle carpal and radiocarpal joints of nine mature Shetland ponies and osteochondral samples were harvested at 39 weeks after being euthanized under respective ethical permissions. T relaxation times of the samples (n = 8 + 8 for experimental and n = 12 for contralateral controls) were measured with a variable flip angle 3D multiband-sweep imaging with Fourier transform sequence.

Axon fiber orientation as the source of T relaxation anisotropy in white matter: A study on corpus callosum in vivo and ex vivo.

Purpose: Recent studies indicate that T in white matter (WM) is influenced by fiber orientation in B . The purpose of the study was to investigate the interrelationships between axon fiber orientation in corpus callosum (CC) and T relaxation time in humans in vivo as well as in rat brain ex vivo.

Methods: Volunteers were scanned for relaxometric and diffusion MRI at 3 T and 7 T.

Correction: A musculoskeletal finite element model of rat knee joint for evaluating cartilage biomechanics during gait.

[This corrects the article DOI: 10.1371/journal.pcbi.

orientation anisotropy mapping of articular cartilage using qMRI.

To provide orientation-independent MR parameters potentially sensitive to articular cartilage degeneration by measuring isotropic and anisotropic components ofrelaxation, as well as 3D fiber orientation angle and anisotropy via multi-orientation MR scans.. Seven bovine osteochondral plugs were scanned with a high angular resolution of thirty-seven orientations spanning 180° at 9.

Assessing post-traumatic changes in cartilage using T dispersion parameters.

Degeneration of cartilage can be studied non-invasively with quantitative MRI. A promising parameter for detecting early osteoarthritis in articular cartilage is T, which can be tuned via the amplitude of the spin-lock pulse. By measuring T at several spin-lock amplitudes, the dispersion of T is obtained.

New methods for robust continuous wave T relaxation preparation.

Measurement of the longitudinal relaxation time in the rotating frame of reference (T ) is sensitive to the fidelity of the main imaging magnetic field (B ) and that of the RF pulse (B ). The purpose of this study was to introduce methods for producing continuous wave (CW) T contrast with improved robustness against field inhomogeneities and to compare the sensitivities of several existing and the novel T contrast generation methods with the B and B field inhomogeneities. Four hard-pulse and four adiabatic CW-T magnetization preparations were investigated.

Machine Learning Prediction of Collagen Fiber Orientation and Proteoglycan Content From Multiparametric Quantitative MRI in Articular Cartilage.

Background: Machine learning models trained with multiparametric quantitative MRIs (qMRIs) have the potential to provide valuable information about the structural composition of articular cartilage.

Purpose: To study the performance and feasibility of machine learning models combined with qMRIs for noninvasive assessment of collagen fiber orientation and proteoglycan content.

Study Type: Retrospective, animal model.

Relaxation anisotropy of quantitative MRI parameters in biological tissues.

Quantitative MR relaxation parameters vary in the sensitivity to the orientation of the tissue in the magnetic field. In this study, the orientation dependence of multiple relaxation parameters was assessed in various tissues. Ex vivo samples of each tissue type were prepared either from bovine knee (tendon, cartilage) or mouse (brain, spinal cord, heart, kidney), and imaged at 9.

Embedded Quantitative MRI T Mapping Using Non-Linear Primal-Dual Proximal Splitting.

Quantitative MRI (qMRI) methods allow reducing the subjectivity of clinical MRI by providing numerical values on which diagnostic assessment or predictions of tissue properties can be based. However, qMRI measurements typically take more time than anatomical imaging due to requiring multiple measurements with varying contrasts for, e.g.

A musculoskeletal finite element model of rat knee joint for evaluating cartilage biomechanics during gait.

Abnormal loading of the knee due to injuries or obesity is thought to contribute to the development of osteoarthritis (OA). Small animal models have been used for studying OA progression mechanisms. However, numerical models to study cartilage responses under dynamic loading in preclinical animal models have not been developed.

Dipolar Relaxation of Water Protons in the Vicinity of a Collagen-like Peptide.

Quantitative magnetic resonance imaging is one of the few available methods for noninvasive diagnosis of degenerative changes in articular cartilage. The clinical use of the imaging data is limited by the lack of a clear association between structural changes at the molecular level and the measured magnetic relaxation times. In anisotropic, collagen-containing tissues, such as articular cartilage, the orientation dependency of nuclear magnetic relaxation can obscure the content of the images.

Subject-specific biomechanical analysis to estimate locations susceptible to osteoarthritis-Finite element modeling and MRI follow-up of ACL reconstructed patients.

The aims of this case-control study were to: (1) Identify cartilage locations and volumes at risk of osteoarthritis (OA) using subject-specific finite element (FE) models; (2) Quantify the relationships between the simulated biomechanical parameters and T and T relaxation times of magnetic resonance imaging (MRI). We created subject-specific FE models for seven patients with anterior cruciate ligament (ACL) reconstruction and six controls based on a previous proof-of-concept study. We identified locations and cartilage volumes susceptible to OA, based on maximum principal stresses and absolute maximum shear strains in cartilage exceeding thresholds of 7 MPa and 32%, respectively.