T2 Relaxation Values Research Articles

Outcomes Following Autologous Osteochondral Transplantation for Osteochondral Lesions of the Talus at 10-Year Follow-Up: A Retrospective Review.

The purpose of this study was to evaluate outcomes following autologous osteochondral transplantation (AOT) for the treatment of osteochondral lesions of the talus (OLT) at a minimum of 10-year follow-up. Retrospective chart review identified patients who underwent AOT for the treatment of OLT. Pre-operative magnetic resonance imaging (MRI) scans were obtained in all patients. Clinical outcomes assessed included: pre- and post-operative foot and ankle outcome score (FAOS), visual analog scale (VAS), patient satisfaction, complications, failures and secondary surgical procedures. Thirty-nine patients with a mean lesion size was 122.3 ± 64.1 mm2 and mean follow-up time of 138.9 ± 16.9 months were included. The mean FAOS scores improved from a preoperative score of 51.9 ± 16.0 to 75.3 ± 21.9 (P < 0.001). Increasing lesion size was variable associated with inferior FAOS scores (R2 = 0.2228). There was statistically significant higher mean T2 relaxation values at the superficial layer at the site of the AOT graft (42.9 ± 5.2 ms) compared to the superficial layer of the adjacent native cartilage (35.8 ± 3.8 ms) (P < 0.001). Seventeen complications (43.6%) were observed, the most common of which was anterior ankle impingement (25.6%). There were 2 failures (5.1%), both of which had a history of prior bone marrow stimulation via microfracture and post-operative cysts identified on MRI. This retrospective review found that AOT for the treatment of large OLTs produced a 94.9% survival rate at a minimum of 10-year follow-up. Increasing lesion size was associated with inferior clinical outcomes. The findings of this study indicates that AOT is a viable long-term surgical strategy for the treatment of large OLTs.

Visualizing dynamic alterations of vitreous viscosity during elevated intraocular pressure in glaucoma with a Near-infrared/Magnetic resonance imaging dual-modal nanoprobe

Glaucoma is a chronic progressive disease leading to irreversible visual impairment and blindness. High intraocular pressure (IOP) resulting from abnormally high outflow resistance is a major risk factor for glaucoma development, however, it is unclear how IOP elevation influences the structure and function of the retina and the optic nerve via vitreous humor located between the lens and retina in the eye. To understand vitreous biomechanical and stimulus response toward IOP elevation, we developed a novel near-infrared (NIR)/MRI dual-modal nanoprobe, DTA/P-NCA/17F@Co, which is composed of N, N-dimethyl-4(thien-2-yl)-aniline group (DTA) as NIR fluorophore and the fluorine-based polyamino acid cobalt nanoparticles (P-NCA/17F@Co) as T2 contrast agent. These nanoprobes exhibit good biocompatibility, low surface energy characteristics, and viscosity-responsive NIR emission and T2 relaxation values. The intrinsic viscosity-sensitivemechanismof nanoprobes was ascribed to constrained molecular motion in high-viscosity vitreous chamber, which causes enhanced fluorescence emission and shortened T2 relaxation times. By using its ability for dual-modal visualization of viscosity, we achieved non-invasive in vivo monitoring the changes in vitreous viscosity during elevated IOP in a glaucoma rat model. In vivo experiments validated that vitreous viscosity is very strongly correlated with IOP elevation induced by glaucoma, much earlier than structural and functional change in the retina. Our findings revealed that IOP elevation induced the increase of vitreous viscosity, indicating that monitoring vitreous viscosity is key to the glaucoma model. This study not only provides versatile nanoprobes for dual-modal visualization of biomechanical properties of the vitreous humor in its native environment, but also shows great potential in the early diagnosis of glaucoma.

Unveiling the Exquisite Microstructural Details in Zebrafish Brain Non-Invasively Using Magnetic Resonance Imaging at 28.2 T

Zebrafish (Danio rerio) is an important animal model for a wide range of neurodegenerative diseases. However, obtaining the cellular resolution that is essential for studying the zebrafish brain remains challenging as it requires high spatial resolution and signal-to-noise ratios (SNR). In the current study, we present the first MRI results of the zebrafish brain at the state-of-the-art magnetic field strength of 28.2 T. The performance of MRI at 28.2 T was compared to 17.6 T. A 20% improvement in SNR was observed at 28.2 T as compared to 17.6 T. Excellent contrast, resolution, and SNR allowed the identification of several brain structures. The normative T1 and T2 relaxation values were established over different zebrafish brain structures at 28.2 T. To zoom into the white matter structures, we applied diffusion tensor imaging (DTI) and obtained axial, radial, and mean diffusivity, as well as fractional anisotropy, at a very high spatial resolution. Visualisation of white matter structures was achieved by short-track track-density imaging by applying the constrained spherical deconvolution method (stTDI CSD). For the first time, an algorithm for stTDI with multi-shell multi-tissue (msmt) CSD was tested on zebrafish brain data. A significant reduction in false-positive tracks from grey matter signals was observed compared to stTDI with single-shell single-tissue (ssst) CSD. This allowed the non-invasive identification of white matter structures at high resolution and contrast. Our results show that ultra-high field DTI and tractography provide reproducible and quantitative maps of fibre organisation from tiny zebrafish brains, which can be implemented in the future for a mechanistic understanding of disease-related microstructural changes in zebrafish models of various brain diseases.

Evaluation of the Articular Disc Using the Magnetic Resonance Cartigram in Asymptomatic and Symptomatic Temporomandibular Disorders

Abstract Objectives The study is aimed to perform magnetic resonance (MR) cartigram of the articular disc in patients with asymptomatic and symptomatic temporomandibular disorders (TMD). Methods Thirty-nine volunteers were divided into three groups: 16 symptomatic TMD, 16 asymptomatic TMD, and 7 controls. The articular disc was divided into three segments (anterior, middle, and posterior) and analyzed using morphological magnetic resonance imaging (MRI) and T2 mapping sequences. T2 relaxation values were measured and assessed by an experienced radiologist and two observers. The T2 values in the discs were compared between the control, asymptomatic, and symptomatic groups using the Kruskal–Wallis test. The right and left discs were compared using the Wilcoxon signed rank test. Inter-examiner reliability among different examiners was evaluated. Results The controls had the highest T2 values compared with the other groups. The comparison among the right and left sides of all the groups revealed statistically significant results in the anterior portion in the asymptomatic group and the middle portion in the symptomatic group (p &lt; 0.05). The inter-examiner reliability coefficients among the three examiners were consistently high, with values of 0.921, 0.920, and 0.930. Conclusion Our study found the T2 relaxation time span was shorter than that reported in previous studies, which could be attributed to the early stage of cartilage deterioration in the individuals with TMD inferring treatment at this phase may be eventually effective with a good prognosis.

The clinical application value of 3.0T magnetic resonance T2 mapping imaging in evaluating the degree of acetabular cartilage degeneration in joint replacement surgery running title: MRI and acetabular cartilage degeneration

BackgroundTo explore and compare the values of 3.0T magnetic resonance imaging (MRI) T2 mapping in evaluating the degree of acetabular cartilage degeneration in hip replacement surgery.MethodsA total of 26 elderly patients with femoral neck fractures who were scanned in 3.0T MRI T2 mapping quantification technique were included. Basing on MRI images, the degree of acetabular cartilage degeneration was classified into Grade 0, 1, 2, 3 and 4, according to the International Cartilage Repair Society (ICRS) scores. In addition, 8 healthy volunteers were included for control group.ResultsBy comparison with health population, T2 relaxation values in the anterior, superior, and posterior regions of acetabular cartilage in patients with femoral neck fracture were obviously increased (P < 0.001). Among the patients with femoral neck fractures, there were 16 hip joint with Grade 1–2 (mild degeneration subgroup) and 10 hip joints with Grade 3–4 (severe degeneration subgroup), accounting for 61.54% and 38.46%, respectively. Additionally, T2 relaxation values in the anterior and superior bands of articular cartilage were positively related to the MRI-based grading (P < 0.05); while there was no significant difference of T2 relaxation values in the posterior areas of articular cartilage between severe degeneration subgroup and mild degeneration subgroup (P > 0.05). Importantly, acetabular cartilage degeneration can be detected through signal changes of T2 mapping pseudo-color images.Conclusion3.0T MRI T2 mapping technology can be used to determine the degree of acetabular cartilage degeneration, which can effectively monitor the disease course.

Quantitative assessment of preoperative brain development in pediatric congenital heart disease patients by synthetic MRI

ObjectivesThis study investigated the quantitative assessment and application of Synthetic MRI (SyMRI) for preoperative brain development in children with congenital heart disease (CHD).MethodsForty-three CHD patients aged 2–24 months were prospectively included in the observation group, and 43 healthy infants were included in the control group. The SyMRI scans were processed by postprocessing software to obtain T1, T2, and PD maps. The values of T1, T2, and PD in different brain regions were compared with the scores of the five ability areas of the Gesell Development Scale by Pearson correlation analysis.ResultsIn the observation group, the T1 values of the posterior limb of the internal capsule (PLIC), Optic radiation (PTR), cerebral peduncle, centrum semiovale, occipital white matter, temporal white matter, and dentate nucleus were greater than those in the control group. In the observation group, the T2 values of the PLIC, PTR, frontal white matter, occipital white matter, temporal white matter, and dentate nucleus were greater than those in the control group. Pearson correlation analysis revealed that the observation group had significantly lower Development Scale scores. In the observation group, the T2 value of the splenium of the corpus callosum was significantly positively correlated with the personal social behavior score. The AUCs for diagnosing preoperative brain developmental abnormalities in children with CHD using T1 values of the temporal white matter and dentate nucleus were both greater than 0.60.ConclusionsQuantitative assessment using SyMRI can aid in the early detection of preoperative brain development abnormalities in children with CHD.Critical relevance statementT1 and T2 relaxation values from SyMRI can be considered as a quantitative imaging marker to detect abnormalities, allowing for early clinical evaluation and timely intervention, thereby reducing neurodevelopmental disorders in these children.Key PointsT1 and T2 relaxation values by SyMRI are related to myelin development.Evaluated development quotient markers were lower in the observation compared to the control group.SyMRI can act as a reference indicator for brain development in CHD children.Graphical

Identification of the reporter gene combination that shows high contrast for cellular level MRI.

Currently, we can label the certain cells by transducing specific genes, called reporter genes, and distinguish them from other cells. For example, fluorescent protein such as green fluorescence protein (GFP) is commonly used for cell labeling. However, fluorescent protein is difficult to observe in living animals. We can observe the reporter signals of the luciferin-luciferase system from the outside of living animals using in vivo imaging systems, although the resolution of this system is low. Therefore, in this study, we examined the reporter genes, which allowed the MRI-mediated observation of labeled cells in living animals. As a preliminary stage of animal study, we transduced some groups of plasmids that coded the protein that could take and store metal ions to the cell culture, added metal ions solutions, and measured their T1 or T2 relaxation values. Finally, we specified the best reporter gene combination for MRI, which was the combination of transferrin receptor, DMT1, and Ferritin-M6A for T1WI, and Ferritin-M6A for T2WI.

A Cross-sectional Study on Neuroimaging in Epilepsy: Diagnostic Value of T2 Relaxometry in Mesial Temporal Lobe Epilepsy

Introduction: The use of Magnetic Resonance Imaging (MRI) T2 relaxometry and spectroscopy has added new dimensions to the imaging of Temporal Lobe Epilepsy (TLE). Advanced techniques like MRI diffusion and MRI perfusion are new additions to the MRI protocol for epilepsy. Aim: To study the diagnostic value of T2 relaxation time in Electroencephalogram (EEG) confirmed seizure cases. Materials and Methods: A single-centre, cross-sectional study was conducted at Department of Radiodiagnosis, Saveetha Medical College, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India, from December 2020 to November 2022 at a tertiary care hospital. All patients were subjected to MRI with a special epilepsy protocol and T2 relaxometry. Hippocampal T2 relaxation values for each slice were measured by placing a Region of Interest (ROI) on the representative image obtained from the T2 relaxometry sequence, focusing on the hippocampus in both the control and study groups. The control group (n=30) consisted of healthy volunteers, whereas the case group (n=36) comprised patients presenting with a history of seizures with positive MRI and EEG findings. Mean T2 relaxation time was calculated in each ROI, and an average was derived. Mean and Standard Deviation (SD) were calculated for the continuous variables, while ratios and proportions were calculated for the categorical variables. To determine the association of T2 relaxometry values in the study and control groups, an unpaired t-test was used. Results: The mean age of participants was 25.14±9.35 years (ranging from 9 to 51 years). The male-to-female ratio was 1.25:1. Hippocampal atrophy (32 out of 36 cases) and T2 signal alteration (30 out of 36 cases) were the most commonly identified features in Mesial Temporal Sclerosis (MTS). MRI without T2 relaxometry had a sensitivity of 94%. In two cases, where only mild hippocampal atrophy was identified in the conventional MRI sequence, making the diagnosis dubious, T2 relaxometry revealed increased T2 relaxation time in the head of the hippocampus and guided a proper diagnosis. EEG was able to lateralise seizures in 8 out of 13 right MTS cases (61.5%), 10 out of 17 left MTS cases (58.9%), and 5 out of 6 cases of bilateral MTS (83%). Conclusion: T2 relaxometry allows quantification of hippocampal signal intensity, allowing the detection of even subtle changes in signal intensity that are difficult to perceive by visual assessment.

Gestational age-related changes in relaxation times of neonatal brain by quantitative synthetic magnetic resonance imaging.

This study aimed to explore the correlation between T1 and T2 relaxation times of synthetic MRI (SyMRI) and gestational age (GA) in each hemisphere of preterm and term newborns at the initial 28 days of birth. Seventy preterm and full-term infants were prospectively included in this study. All subjects completed 3.0 T routine MRI and SyMRI (MAGiC) one-stop scanning within 28 days of birth (aged 34-42 W at examination). The SyMRI postprocessing software (v8.0.4) was used to measure the T1 and T2 relaxation values of each brain region. The linear regression equations of quantitative relaxation values with GA were established to compare the variation speed in each brain region. A significant linear and negative correlation was found between relaxation times and GA in the neonate cerebral cortex and subcortical gray and white matter regions (All p<.05). The relaxation time of the left centrum semiovale decreased with maximum variance with increasing GA among all white matter regions (T1: b = -51.45, β = -0.65, p < .0001; T2: b = -8.77, β = -0.71, p < .0001), whereas the right posterior limb of internal capsule showed minimal variance (T1: b = -27.94, β = -0.60, p < .0001; T2: b = -3.25, β = -0.68, p < .0001). Among all gray matter regions, the right globus pallidus and thalamus indicated the most significant decreasing degree of T1 and T2 relaxation values with GA (right globus pallidus T1: b = -33.14, β = -0.64, p < .0001; right thalamus T2: b = -3.94, β = -0.81, p < .0001), and the right and left occipital lobes indicated the least significant decreasing degree of T1 and T2 relaxation values with GA, respectively (right occipital lobes T1: b = -11.18, β = -0.26, p = .028; left occipital lobes T2: b = -1.22, β = -0.27, p = .024). SyMRI could quantitatively evaluate the linear changes of T1 and T2 relaxation values with GA in brain gray and white matter of preterm and term neonates.

Scyllo-inositol: Transverse relaxation time constant at 3T and concentration changes associated with aging and alcohol use.

The goals of this study were to measure the apparent transverse relaxation time constant, T2 , of scyllo-inositol (sIns) in young and older healthy adults' brains and to investigate the effect of alcohol usage on sIns in young and older healthy adults' brains, using proton magnetic resonance spectroscopy (MRS) at 3T. Twenty-nine young adults (age 21 ± 1years) and 24 older adults (age 74 ± 3years) participated in this study. MRS data were acquired from two brain regions (the occipital cortex and posterior cingulate cortex) at 3T. The T2 of sIns was measured using a localization by adiabatic selective refocusing (LASER) sequence at various echo times, while the sIns concentrations were measured using a short-echo-time stimulated echo acquisition mode (STEAM) sequence. A trend towards lower T2 relaxation values of sIns in older adults was observed, although these were not significant. sIns concentration was higher with age in both brain regions and was significantly higher in the young when considering alcohol consumption of more than two drinks per week. This study shows that differences in sIns can be found in two distinct regions of the brain across two age groups, potentially reflecting normal aging. In addition, it is important to take into account alcohol consumption when reporting the sIns level in the brain.

Non-contrast cardiac magnetic resonance imaging after SARS-CoV2 infection or vaccination in asymptomatic adolescents: insights from the EnIGMA study

Abstract Background Myocarditis after SARS-CoV2 infection or vaccination is rare, but seems to be relatively more frequent in young population. Cardiac magnetic resonance (CMR) T2 weighted sequences have the potential to detect subclinical myocarditis. However, there is paucity of data on the potential myocardial involvement after SARS-CoV2 infection or vaccination in asymptomatic adolescents. Purpose To evaluate the presence of subclinical myocardial damage in adolescents who were infected with SARS-CoV2 or vaccinated against SARS-CoV2 using non-contrast CMR imaging. Methods Asymptomatic adolescents enrolled in the “Early ImaginG Markers of unhealthy lifestyles in Adolescents” (EnIGMA) project were scanned using a 3-Tesla CMR scanner between March 2021 and October 2021. CMR scans included CINE imaging and myocardial T2-mapping sequences. SARS-CoV2 IgG antibody testing was performed in capillary blood samples, and date of confirmed SARS-CoV2 infection and/or vaccination if any was collected. Participants were assigned to three different groups according to SARS-CoV2 status: Group 1 (non-infected and non-vaccinated), Group 2 (infected and non-vaccinated), and Group 3 (vaccinated, independently of past infection status). CMR images were analyzed by experienced observers blinded to adolescent's SARS-CoV2 status. ANOVA and multiple regression analysis, together with correlation coefficients, were used to study between-group differences and associations among variables of interest. Results A total of 115 adolescents with a mean age of 16.0 years (standard deviation (SD)=0.4), 54% girls, completed the CMR study and SARS-CoV2 data successfully, and were assigned to Group 1 (n=72), Group 2 (n=22), and Group 3 (n=21). Left and right ventricular ejection fraction (LVEF/RVEF) did not significantly differ among groups: mean LVEF was 62.8% (SD=4.1), 63.0% (SD=3.7) and 60.9% (SD=3.9) [p=0.12] and mean RVEF was 56.5% (SD=4.2), 56.5% (SD=5.5) and 54.5% (SD=5.1) [p=0.23] in Groups 1, 2 and 3, respectively. Similarly, there were no between-group significant differences in myocardial T2 relaxation values: mean T2 values were 44.1 ms (SD=2.2), 44.1 ms (SD=1.8) and 44.4 ms (SD=1.9) in Groups 1, 2, and 3, respectively (p=0.63) (Figure 1). No differences were found either after adjusting for age and gender. Median time (interquartile range) from date of infection or vaccination to CMR acquisition was 133 (121) days and 28 (38) days in Group 2 and Group 3, respectively. No correlation between time from infection/vaccination to CMR acquisition and T2 values was detected (Figure 2). Conclusions This observational study did not find evidence of subclinical myocardial involvement after SARS-CoV2 infection or vaccination in asymptomatic adolescents, as assessed with T2-mapping magnetic resonance imaging. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Instituto de Salud Carlos III (ISCIII)-Fondo de Investigaciόn Sanitaria.European Regional Development Fund/European Social Fund (“A way to make Europe”/“Investing in your future”.

Vascular topology and blood flow are acutely impacted by experimental febrile status epilepticus

Febrile status epilepticus (FSE) is an important risk factor for temporal lobe epilepsy and early identification of those at high risk for epilepsy is vital. In a rat model of FSE, we identified an acute (2 hrs) novel MRI signal where reduced T2 relaxation values in the basolateral amygdala (BLA) predicted epilepsy in adulthood; this T2 signal remains incompletely understood and we hypothesized that it may be influenced by vascular topology. Experimental FSE induced in rat pups reduced blood vessel density of the cortical vasculature in a lateralized manner at 2 hrs post FSE. Middle cerebral artery (MCA) exhibited abnormal topology in FSE pups but not in controls. In the BLA, significant vessel junction reductions and decreased vessel diameter were observed, together with a strong trend for reduced vessel length. Perfusion weighted MRI (PWI) was acutely increased cerebral blood flow (CBF) in cortex, amygdala and hippocampus of FSE pups that correlated to decreased T2 relaxation values compared to controls. This is consistent with increased levels of deoxyhemoglobin associated with increased metabolic demand. In summary, FSE acutely modifies vascular topological and CBF in cortex and BLA that may underlie acute MRI signal changes that predict progression to future epilepsy.

Structural differences between immature and mature articular cartilage of rabbits by microscopic MRI and polarized light microscopy.

This study aimed to determine the structural features between immature and mature articular cartilage from the humeral and femoral joints of rabbits. Specimens of articular cartilage (n = 6 for immature tissue, n = 6 for mature tissue) that were still attached to the underlying bone from a humerus (shoulder joint) or femur (knee joint) were imaged using microscopic MRI (µMRI) and polarized light microscopy (PLM). Quantitative µMRI data with a pixel resolution of 11.7-13.2µm revealed a number of differences between the immature and mature cartilage, including total thickness, and T2 and T1ρ relaxation values. Quantitative PLM data with a pixel resolution of 0.25-1µm confirmed the µMRI results and revealed additional differences in cellular features between the tissues. The mature cartilage had a clearly defined tidemark, which was absent in the immature tissue. The ability to differentiate specific maturation-related cartilage characteristics could be beneficial to translational studies of degenerative diseases such as osteoarthritis.

T2 MAPPING OF THE ARTICULAR CARTILAGE AS A BIOMARKER FOR OA IN A POPULATION BASED COHORT: THE ROTTERDAM STUDY

While quantitative T2 mapping has been well established as a non-invasive tool for assessing (early) OA progression, there have been a limited number of studies investigating this in large population-based cohorts, other than the OAI. The objectives of the current study were to evaluate 1) the relationship between T2 relaxation times and patient characteristics age and BMI, and 2) the relationship between T2 relaxation times and MRI-based OA status, in a population-based study. We included 1327 knees from 665 females (mean age 59.8 years;SD:3.7 and mean BMI 26.9 kg/m2; SD:4.7) from a subcohort of the population based Rotterdam Study. All knees underwent 1.5 Tesla MRI at two different time-points (mean time between scans 5.1 years; SD: 0.4) comprising sagittal dual-echo FSE proton density–weighted, spoiled gradient echo with fat suppression, and fast imaging employing steady-state acquisition (FIESTA) sequences. The second time-point included an additional sagittal T2-weighted FSE sequence with fat suppression (4 echo times (15, 30, 45, 60 ms), repetition time 4100ms, field of view 160 x 160mm; slice thickness 3.2mm; matrix 256 x 256) for the purpose of T2 mapping. T2 relaxation times were calculated in six femoral and tibial regions of interest of full-thickness tibiofemoral cartilage: LF, LT, pLF, MF, MT, and pMF. Differences between groups were calculated using Student's t-tests for continuous data. Associations between T2 relaxation times and MRI Osteoarthritis Knee Score (MOAKS)-based tibiofemoral OA were analyzed using logistic regression with age and BMI adjustments. We defined early OA as OA developed between time-points, and late OA as OA established at the first time-point, prior to T2 mapping sequencing. Statistical analyses were performed using R (version 3.6.3). One hundred thirty-six knees had MRI defined OA at baseline, and 235 knees had OA at follow-up, meaning 99 knees developed OA the follow-up. T2 relaxation times were positively correlated with BMI, which was most pronounced in the lateral compartment (R 2 range: 0.38-0.44, all p-values <0.001). Very weak associations were found between T2 relaxation times and age for both compartments (R 2 range: 0.01-0.08). Knees with OA at follow-up had higher T2 values compared to knees without OA in the LF weight-bearing cartilage (35.7 vs. 35.3 ms, p=0.04), LT weight-bearing cartilage (35.8 vs. 34.8 ms, p<0.001), pLF cartilage (37 vs. 35.6 ms, p<0.001), MT weight-bearing cartilage (35.1 vs. 34.7, p=0.02), and pMF cartilage (37.9 vs. 36.9 ms, p<0.001). At the first time-point the LT (OR:1.11; 95%CI:1.04-1.18), pLF (OR:1.32; 95%CI:1.21-1.45), MF (OR:1.12; 95%CI:1.03-1.22), MT (OR:1.12; 95%CI:1.02-1.22), and pMF (OR:1.18; 95%CI:1.08-1.29) cartilage were significantly associated with OA after adjustments. At follow-up, LT (OR:1.08; 95%CI: 1.02-1.14), pLF (OR:1.27; 95%CI: 1.18-1.37) and pMF (OR:1.17; 95%CI:1.09-1.26) were associated with OA. In knees that developed OA during follow-up, T2 values of the pLF cartilage (OR:1.16; 95%CI:1.04-1.29) were associated with OA development. In this population-based cohort, early OA was associated with T2 values of the pLF, whereas advanced OA was associated with LT, pLF, MF, MT, and pMF cartilage segments. T2 values had very weak correlations with age, whereas weak to moderate correlations were observed between T2 relaxation values and BMI. none none. The authors are grateful to the participants and staff of the Rotterdam Study CORRESPONDENCE ADDRESS: e.oei@erasmusmc.nl

T2 Mapping Refined Finite Element Modeling to Predict Knee Osteoarthritis Progression.

This paper presents a novel method for informing cartilage material properties in finite element models from T2 relaxometry. In the developed pipeline, T2 relaxation values are mapped to elements in subject-specific finite element models of the cartilage and menisci. The Young's modulus for each element within the cartilage is directly calculated from its corresponding T2 relaxation voxel value. Our model was tested on a single subject (Subject ID 9932809, Kellgren-Lawrence grade 2) from the Osteoarthritis Initiative dataset at baseline imaging. For comparison, an identical finite element model was built with homogeneous material properties. Kinematics of the stance phase of a standard gait cycle were used as model constraints. Simulation results were compared qualitatively to the MRI Osteoarthritis Knee Score (MOAKS) from the same baseline timepoint. Our T2-refined material model showed higher maximum shear strain in regions with moderate cartilage loss as compared to the homogeneous material model, and the homogeneous model showed higher maximum principal stress and maximum shear strain in regions with no cartilage loss. These results show that a homogeneous material model likely underestimates tissue strains in regions with cartilage damage while overestimating strains in regions with healthy cartilage. This preliminary study demonstrates that T2-refined material properties are more appropriate than assumptions of homogeneity in predictive models of cartilage damage.Clinical relevance- The proposed pipeline demonstrates a computationally efficient way to improve the subject-specificity of finite element models used for evaluation of osteoarthritis.

Regional brain tissue changes in patients with cystic fibrosis

BackgroundCystic fibrosis (CF) patients present with a variety of symptoms, including mood and cognition deficits, in addition to classical respiratory, and autonomic issues. This suggests that brain injury, which can be examined with non-invasive magnetic resonance imaging (MRI), is a manifestation of this condition. However, brain tissue integrity in sites that regulate cognitive, autonomic, respiratory, and mood functions in CF patients is unclear. Our aim was to assess regional brain changes using high-resolution T1-weighted images based gray matter (GM) density and T2-relaxometry procedures in CF over control subjects.MethodsWe acquired high-resolution T1-weighted images and proton-density (PD) and T2-weighted images from 5 CF and 15 control subjects using a 3.0-Tesla MRI. High-resolution T1-weighted images were partitioned to GM-tissue type, normalized to a common space, and smoothed. Using PD- and T2-weighted images, whole-brain T2-relaxation maps were calculated, normalized, and smoothed. The smoothed GM-density and T2-relaxation maps were compared voxel-by-voxel between groups using analysis of covariance (covariates, age and sex; SPM12, p < 0.001).ResultsSignificantly increased GM-density, indicating tissues injury, emerged in multiple brain regions, including the cerebellum, hippocampus, amygdala, basal forebrain, insula, and frontal and prefrontal cortices. Various brain areas showed significantly reduced T2-relaxation values in CF subjects, indicating predominant acute tissue changes, in the cerebellum, cerebellar tonsil, prefrontal and frontal cortices, insula, and corpus callosum.ConclusionsCystic fibrosis subjects show predominant acute tissue changes in areas that control mood, cognition, respiratory, and autonomic functions and suggests that tissue changes may contribute to symptoms resulting from ongoing hypoxia accompanying the condition.

Open Source Software for Automatic Subregional Assessment of Knee Cartilage Degradation Using Quantitative T2 Relaxometry and Deep Learning.

We evaluated a fully automated femoral cartilage segmentation model for measuring T2 relaxation values and longitudinal changes using multi-echo spin-echo (MESE) magnetic resonance imaging (MRI). We open sourced this model and developed a web app available at https://kl.stanford.edu into which users can drag and drop images to segment them automatically. We trained a neural network to segment femoral cartilage from MESE MRIs. Cartilage was divided into 12 subregions along medial-lateral, superficial-deep, and anterior-central-posterior boundaries. Subregional T2 values and four-year changes were calculated using a radiologist's segmentations (Reader 1) and the model's segmentations. These were compared using 28 held-out images. A subset of 14 images were also evaluated by a second expert (Reader 2) for comparison. Model segmentations agreed with Reader 1 segmentations with a Dice score of 0.85 ± 0.03. The model's estimated T2 values for individual subregions agreed with those of Reader 1 with an average Spearman correlation of 0.89 and average mean absolute error (MAE) of 1.34 ms. The model's estimated four-year change in T2 for individual subregions agreed with Reader 1 with an average correlation of 0.80 and average MAE of 1.72 ms. The model agreed with Reader 1 at least as closely as Reader 2 agreed with Reader 1 in terms of Dice score (0.85 vs. 0.75) and subregional T2 values. Assessments of cartilage health using our fully automated segmentation model agreed with those of an expert as closely as experts agreed with one another. This has the potential to accelerate osteoarthritis research.

The feasibility of T2 mapping in the assessment of hepatic steatosis, inflammation, and fibrosis in patients with non-alcoholic fatty liver disease: a preliminary study

To determine the feasibility of magnetic resonance imaging T2 mapping in the quantification of liver steatosis in patients with biopsy-proven non-alcoholic fatty liver disease (NAFLD), and to assess the effect of inflammation and fibrosis on T2 values of the liver. Twenty-three consecutive patients with biopsy-proven NAFLD who underwent T2 mapping between December 2013 and September 2014 were included in this study. All patients underwent fast spin echo multi-echo sequence with eight echoes for T2 measurements. The mean liver T2 value and percentage of histological steatosis was 64.9±7.4 ms and 46.5±27.6%, respectively. There was a good correlation between the liver T2 value and histology-determined steatosis (r = 0.780, p<0.001) and grade of steatosis (rs=0.779, p<0.001). The mean T2 value in patients with definitive non-alcoholic steatohepatitis (NASH) was significantly higher in comparison with patients without NASH (69±7.37 versus 61.73±5.99 ms, p=0.016). The correlation between T2 value and NAFLD activity score (NAS) was significant (rs=0.443, p=0.034); however, the correlation disappeared after adjustment for hepatic steatosis and fibrosis (r=0.131, p=0.572). There was a close inverse correlation between T2 value and fibrosis stage after adjusting for hepatic steatosis (r=-0.536, p=0.012). T2 mapping can be used for quantification of hepatic steatosis, as there is a close correlation between T2 relaxation values and histology-determined steatosis. Patients with definite NASH have increased T2 values and there is an inverse correlation between the T2 value and fibrosis stage of the liver. T2 mapping in NAFLD may be a useful clinical tool for disease assessment and prognostication.

Quantitative imaging metrics derived from magnetic resonance fingerprinting using ISMRM/NIST MRI system phantom: An international multicenter repeatability and reproducibility study.

To compare the bias and inherent reliability of the quantitative (T1 and T2 ) imaging metrics generated from the magnetic resonance fingerprinting (MRF) technique using the ISMRM/NIST system phantom in an international multicenter setting. ISMRM/NIST MRI system phantom provides standard reference T1 and T2 relaxation values (vendor-provided) for each of the 14 vials in T1 and T2 arrays. MRF-SSFP scans repeated over 30days on GE 1.5 and 3.0T scanners at three collaborative centers. MRF estimated T1, and T2 values averaged over 30days were compared with the phantom vendor-provided and spin-echo (SE) based convention gold standard (GS) method. Repeatability and reproducibility were characterized by the within-case coefficient of variation (wCV) of the MRF data acquired over 30days, along with the biases. For the wide ranges of MRF estimated T1 values, vials #1-8 (T1 relaxation time between 2033 and 184ms) exhibited a wCV less than 3% and 4%, respectively, on 3.0 and 1.5T scanners. T2 values in vials #1-8 (T2 relaxation, 1044-45ms) have shown wCV to be <7% on both 3.0 and 1.5T scanners. A stronger linear correlation overall for T1 (R2 =0.9960 and 0.9963 at center-1 and center-2 on 3.0T scanner, and R2 =0.9951 and 0.9988 at center-1 and center-3 on 1.5T scanner) compared to T2 (R2 =0.9971 and 0.9972 at center-1 and center-2 on 3.0T scanner, and R2 =0.9815 and 0.9754 at center-1 and center-3 on 1.5T scanner). Bland-Altman (BA) analysis showed MRF based T1 and T2 values were within the limit of agreement (LOA) except for one data point. The mean difference or bias and 95% lower bound (LB) and upper bound (UB) LOA are reported in the format; mean bias: 95% LB LOA: 95% UB LOA. The biases for T1 values were 21.34: -50.00: 92.69, 21.32: -47.29: 89.94ms, and for T2 values were -19.88: -42.37: 2.61, -19.06: -43.58: 5.45ms on 3.0T scanner at center-1 and center-2, respectively. Similarly, on 1.5T scanner biases for T1 values were 26.54: -53.41: 106.50, 9.997: -51.94: 71.94ms, and for T2 values were -23.84: -135.40: 87.76, -37.30: 134.30: 59.73ms at center-1 and center-3, respectively. Additionally, the correlation between the SE based GS and MRF estimated T1 and T2 values (R2 =0.9969 and 0.9977) showed a similar trend as we observed between vendor-provided and MRF estimated T1 and T2 values (R2 =0.9963 and 0.9972). In addition to correlation, BA analysis showed that all the vials are within the LOA between the GS and vendor-provided for the T1 values and except one vial for T2 . All the vials are within the LOA between GS and MRF except one vial in T1 and T2 array. The wCV for reproducibility was <3% for both T1 and T2 values in vials #1-8, for all the 14 vials, wCV calculated for reproducibility was <4% for T1 values and <5% for T2 . This study shows that MRF is highly repeatable (wCV <4% for T1 and <7% for T2 ) and reproducible (wCV < 3% for both T1 and T2 ) in certain vials (vials #1-8).

T2-based area-at-risk and edema are influenced by ischemic duration in acute myocardial infarction

The purpose of our study was to assess whether T2 MRI identifies the infarcted myocardium or the true area-at-risk (AAR) and whether edema is present in the salvageable region following acute myocardial infarction (MI). The study involved a porcine model of MI with a coronary occlusion model of either 60 min or 90 min. Imaging was performed on a 3T MRI pre-occlusion and at day 3 post-MI. Prior-MI, myocardial perfusion territory (MPT) maps were obtained under MRI via direct intracoronary injection of contrast agent. Post-MI, edema extent was quantified by T2 mapping while infarction and microvascular obstruction (MVO) were assessed by late gadolinium enhancement (LGE). Anatomically registered short-axis slices were analyzed for MPT, T2-AAR and infarct areas and T2 relaxation values. Animals were divided into groups with (MVO+) and without MVO (MVO-). T2-AAR area was significantly greater than infarct area in both groups. In the MVO+ group, T2-AAR and MPT were comparable and highly correlated, whereas, in the MVO- group, T2-AAR significantly underestimated MPT without any trend. T2 values in the salvageable myocardium were found to be significantly higher than those in remote myocardium. Our methodology offers the advantage that all images are acquired within the same MRI reference as opposed to complex co-registration with gross pathology. Our study suggests that edema may expand beyond the infarct zone over the entire ischemic bed. T2-AAR may be more clinically relevant than true AAR by perfusion territory since it identifies the “salvageable” myocardium.