Changes In T2 Relaxation Times Research Articles

Longitudinal analysis of T2 relaxation time variations following radiotherapy for prostate cancer

Aim of this paper is to evaluate short and long-term changes in T2 relaxation times after radiotherapy in patients with low and intermediate risk localized prostate cancer. A total of 24 patients were selected for this retrospective study. Each participant underwent 1.5T magnetic resonance imaging on seven separate occasions: initially after the implantation of gold fiducials, the required step for Cyberknife therapy guidance, followed by MRI scans two weeks post-therapy and monthly thereafter. As part of each MRI scan, the prostate region was manually delineated, and the T2 relaxation times were calculated for quantitative analysis. The T2 relaxation times between individual follow-ups were analyzed using Repeated Measures Analysis of Variance that revealed a significant difference across all measurements (F (6, 120) = 0.611, p << 0.001). A Bonferroni post hoc test revealed significant differences in median T2 values between the baseline and subsequent measurements, particularly between pre-therapy (M0) and two weeks post-therapy (M1), as well as during the monthly interval checks (M2 - M6). Some cases showed a delayed decrease in relaxation times, indicating the prolonged effects of therapy. The changes in T2 values during the course of radiotherapy can help in monitoring radiotherapy response in unconfirmed patients, quantifying the scarring process, and recognizing the therapy failure.

T2 mapping magnetic resonance imaging of cartilage in hemophilia

BackgroundIn hemophilia, recurrent hemarthrosis may lead to irreversible arthropathy. T2 mapping MRI may reflect cartilage changes at an earlier reversible stage of arthropathy as opposed to structural MRI. ObjectivesTo evaluate interval changes of T2 mapping compared with the International Prophylaxis Study Group (IPSG) structural MRI scores of ankle cartilage in boys with hemophilia receiving prophylaxis. MethodsEight boys with hemophilia A (median age, 13; range, 9-17 years), 7 age- and sex-matched healthy boys (controls, median age, 15; range, 7-16 years). A multiecho spin-echo T2-weighted MRI sequence at 3.0T was used to obtain T2 maps of cartilage of boys with hemophilia and controls. Structural joint status was evaluated using the IPSG MRI score. ResultsT2 relaxation times of ankle cartilage increased significantly over time in both persons with hemophilia and controls (P = .002 and P = .00009, respectively). Changes in T2 relaxation time strongly correlated with changes in IPSG cartilage scores (rs = 0.93 to rs = 0.78 [P = .0007 to P = .023]), but not with changes in age (P = .304 to P = .840). Responsiveness of T2 relaxation times were higher than that of IPSG cartilage scores, with standardized response means >1.4 for T2 mapping in all regions-of-interest compared with 0.84 for IPSG cartilage scores. Baseline T2 relaxation time strongly correlated with timepoint 2 IPSG cartilage score (rs = 0.93 to rs = 0.82 [P = .001 to P = .012]) and T2 relaxation time (rs = 0.98 to rs = 0.88 [P = .00003 to P = .004]) changes in most regions-of-interest. ConclusionT2 mapping shows sensitivity to biochemical changes in cartilage prior to detectable damage using conventional MRI, offering potential for early detection of bleed-related cartilage damage in boys with hemophilia.

Histological Findings and T2 Relaxation Time in Canine Menisci of Elderly Dogs—An Ex Vivo Study in Stifle Joints

Osteoarthritis is a chronic disease that often affects the canine stifle joint. Due to their biomechanical function, the menisci in the canine stifle play an important role in osteoarthritis. They compensate for the incongruence in the joint and distribute and minimize compressive loads, protecting the hyaline articular cartilage from damage. Meniscal degeneration favors the development and progression of stifle joint osteoarthritis. Qualitative magnetic resonance imaging (MRI) is the current golden standard for detecting meniscal changes, but it has limitations in detecting early signs of meniscal degeneration. A quantitative MRI offers new options for detecting early structural changes. T2 mapping can especially visualize structural changes such as altered collagen structures and water content, as well as deviations in proteoglycan content. This study evaluated T2 mapping and performed a histological scoring of menisci in elderly dogs that had no or only low radiographic osteoarthritis grades. A total of 16 stifles from 8 older dogs of different sex and breed underwent ex vivo magnet resonance imaging, including a T2 mapping pulse sequence with multiple echoes. A histological analysis of corresponding menisci was performed using a modified scoring system. The mean T2 relaxation time was 18.2 ms and the mean histological score was 4.25. Descriptive statistics did not reveal a correlation between T2 relaxation time and histological score. Ex vivo T2 mapping of canine menisci did not demonstrate histological changes, suggesting that early meniscal degeneration can be present in the absence of radiological signs of osteoarthritis, including no significant changes in T2 relaxation time.

In vivo fluid transport in human intervertebral discs varies by spinal level and disc region.

BackgroundThe lumbar discs are large, dense tissues that are primarily avascular, and cells residing in the central region of the disc are up to 6–8 mm from the nearest blood vessel in adults. To maintain homeostasis, disc cells rely on nutrient transport between the discs and adjacent vertebrae. Thus, diminished transport has been proposed as a factor in age‐related disc degeneration.MethodsIn this study, we used magnetic resonance imaging (MRI) to quantify diurnal changes in T2 relaxation time, an MRI biomarker related to disc hydration, to generate 3D models of disc fluid distribution and determine how diurnal changes in fluid varied by spinal level. We recruited 10 participants (five males/five females; age: 21–30 years; BMI: 19.1–29.0 kg/m2) and evaluated the T2 relaxation time of each disc at 8:00 AM and 7:00 PM, as well as degeneration grade (Pfirrmann). We also measured disc height, volume, and perimeter in a subset of individuals as a preliminary comparison of geometry and transport properties.ResultsWe found that the baseline (AM) T2 relaxation time and the diurnal change in T2 relaxation time were greatest in the cranial lumbar discs, decreasing along the lumbar spine from cranial to caudal. In cranial discs, T2 relaxation times decreased in each disc region (nucleus pulposus [NP], inner annulus fibrosus [IAF], and outer annulus fibrosus [OAF]), whereas in caudal discs, T2 relaxation times decreased in the NP but increased in the AF.ConclusionsFluid transport varied by spinal level, where transport was greatest in the most cranial lumbar discs and decreased from cranial to caudal along the lumbar spine. Future work should evaluate what level‐dependent factors affect transport.

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 T2 and T1ρ 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. The locations and volumes susceptible to OA were compared qualitatively and quantitatively against 2-year longitudinal changes in T2 and T1ρ relaxation times. The degeneration volumes predicted by the FE models, based on excessive maximum principal stresses, were significantly correlated (r = 0.711, p < 0.001) with the degeneration volumes determined from T2 relaxation times. There was also a significant correlation between the predicted stress values and changes in T2 relaxation time (r = 0.649, p < 0.001). Absolute maximum shear strains and changes in T1ρ relaxation time were not significantly correlated. Five out of seven patients with ACL reconstruction showed excessive maximum principal stresses in either one or both tibial cartilage compartments, in agreement with follow-up information from MRI. Expectedly, for controls, the FE models and follow-up information showed no degenerative signs. Our results suggest that the presented modelling methodology could be applied to prospectively identify ACL reconstructed patients at risk of biomechanically driven OA, particularly by the analysis of maximum principal stresses of cartilage.

Longitudinal neural connection detection using a ferritin‐encoding adeno‐associated virus vector and in vivo MRI method

The investigation of neural circuits is important for interpreting both healthy brain function and psychiatric disorders. Currently, the architecture of neural circuits is always investigated with fluorescent protein encoding neurotropic virus and ex vivo fluorescent imaging technology. However, it is difficult to obtain a whole‐brain neural circuit connection in living animals, due to the limited fluorescent imaging depth. Herein, the noninvasive, whole‐brain imaging technique of MRI and the hypotoxicity virus vector AAV (adeno‐associated virus) were combined to investigate the whole‐brain neural circuits in vivo. AAV2‐retro are an artificially‐evolved virus vector that permits access to the terminal of neurons and retrograde transport to their cell bodies. By expressing the ferritin protein which could accumulate iron ions and influence the MRI contrast, the neurotropic virus can cause MRI signal changes in the infected regions. For mice injected with the ferritin‐encoding virus vector (rAAV2‐retro‐CAG‐Ferritin) in the caudate putamen (CPu), several regions showed significant changes in MRI contrasts, such as PFC (prefrontal cortex), HIP (hippocampus), Ins (insular cortex) and BLA (basolateral amygdala). The expression of ferritin in those regions was also verified with ex vivo fluorescence imaging. In addition, we demonstrated that changes in T2 relaxation time could be used to identify the spread area of the virus in the brain over time. Thus, the neural connections could be longitudinally detected with the in vivo MRI method. This novel technique could be utilized to observe the viral infection process and detect the neural circuits in a living animal.

Evaluation of liver function in patients with chronic hepatitis B using Gd-EOB-DTPA-enhanced T1 mapping at different acquisition time points: a feasibility study.

This study aimed to explore the impact of different acquisition times on the evaluation of liver function levels in chronic hepatitis B using Gd-EOB-DTPA-enhanced T1 positioning technology under 3.0 Tesla magnetic resonance imaging (MRI). A total of 146 patients with chronic hepatitis B (CHB) were classified into four groups as follows: chronic hepatitis B without liver cirrhosis (CH, 22 cases), liver cirrhosis with Child-Pugh classification A (LCA 63 cases), Child-Pugh B (LCB 47 cases) and Child-Pugh C (LCC 14 cases). Normal liver function (NLF) group was composed of 23 persons who had healthy liver and no medical histories of hepatitis. T1 mapping images were performed before and after administration of Gd-EOB-DPTA using Look-Locker sequence. Changes in T1 relaxation time (T1rt), the reduction rate of T1 relaxation time (ΔT1) and the increase in T1 relaxation rate (ΔR1) of liver over time (at 5, 10, 15 and 20min) were investigated and compared among all five groups using a one-way analysis of variance (ANOVA). The Spearman's rank correlation coefficient (r) was used to show the correlations of these parameters in different liver function groups. In the NLF, CH, LCA and LCB groups, postT1 gradually decreased, while the ΔT1 and ΔR1 gradually increased with time. The parameters were compared between different liver function levels at the same time point, and the differences were statistically significant except for NLF-CH, NLF-LCA and CH-LCA. There was no significant difference in the area under the ROC curve of other parameters at 10, 15 and 20min. At each time point, no correlation was found between preT1rt and the degrees of liver function. PostT1rt was positively correlated with liver function classification, while ΔT1 and ΔR1 were negatively correlated with liver function classification. Gd-EOB-DTPA-enhanced T1 mapping magnetic resonance imaging is beneficial to assess liver function. Using the Gd-EOB-DTPA to enhance T1 mapping imaging to assess liver function can shorten the observation time of the hepatobiliary period and 10min after enhancement may be the best time point.

POS0277 ANABOLIC EFFECT OF LNA043, A NOVEL DISEASE-MODIFYING OSTEOARTHRITIS DRUG CANDIDATE: RESULTS FROM AN IMAGING-BASED PROOF-OF-CONCEPT TRIAL IN PATIENTS WITH FOCAL ARTICULAR CARTILAGE LESIONS

Background:LNA043 is a modified, recombinant version of the human angiopoietin-like 3 (ANGPTL3) protein acting directly on cartilage-resident cells to transmit its cartilage anabolic effect. A first-in-human study previously demonstrated the favourable safety profile and the modulation of several pathways involved in cartilage homeostasis and osteoarthritis (OA)1. A previous proof-of-mechanism imaging study used high field (7 Tesla) magnetic resonance imaging (MRI) to show formation of hyaline-like tissue after a single injection of 20 mg LNA043 (unpublished data).Objectives:To evaluate non-invasively the chondro-regenerative capacity of multiple intra-articular (i.a.) injections of LNA043 in patients with articular cartilage lesions in the knee (NCT03275064).Methods:This was a randomised, double-blind, placebo (PBO)-controlled, proof-of-concept study in patients with a partial thickness cartilage lesion. In total, 58 patients (43 [20 mg LNA043]; 15 [PBO]), stratified by lesion type (condylar or patellar) were treated with 4 weekly i.a. injections. The primary endpoint was T2 relaxation time measurement as a marker of collagen fiber network, and cartilage lesion-volume was a secondary endpoint, both using 3-Tesla MRI. Assessments were performed at baseline, weeks (wks) 8, 16, 28 and 52 (the latter in 23/58 patients). While lesion-volume for the secondary endpoint was determined from manually segmented images, the cartilage volume of 21 sub-regions spanning the entire knee was also measured from 3D isotropic MR images employing an automated segmentation prototype software (MR Chondral Health 2.1 [MRCH], Siemens Healthcare)2. An exploratory analysis evaluated the treatment effect for the additive volume of the 3 subregions in the weight-bearing area of the medial femur.Results:No change in T2 relaxation time was detected between treatment and PBO groups. Manual segmentation showed continuous filling of the cartilage lesions up to wk 28 in LNA043-treated patients with femoral lesions (p=0.08, vs PBO) while no effect was detected for patients with patellar lesions. Given the limitations of measuring small, irregularly shaped lesions with manual image-analysis, the MRCH approach was used (Figure 1). In the medial femoral weight-bearing region, refilling was detected over time (Δ=123 mm3 at wk 28, N= 37, p= 0.05). No overgrowth was detected in the lateral femoral condyles without cartilage damage. The overall safety profile was favourable; only mild/moderate local reactions were reported, including a higher incidence of joint swelling (9.3% vs 0%) and arthralgia (11.6% vs 6.7%) for LNA043 vs PBO resolving spontaneously or with paracetamol/NSAIDs. No anti-drug antibodies were detected.Conclusion:Treatment with 4 weekly i.a. injections of 20 mg LNA043 resulted in regeneration of damaged cartilage in patients with femoral articular cartilage lesions. Automated measurement of cartilage volume in the femoral index region was able to detect a relevant treatment effect and was found to be more sensitive than the manual segmentation method. No sign of cartilage overgrowth was observed in healthy femoral regions. A Phase 2b study in patients with mild to moderate knee OA is in preparation.

Blood-brain barrier breakdown in non-enhancing multiple sclerosis lesions detected by 7-Tesla MP2RAGE ΔT1 mapping.

Although the blood-brain barrier (BBB) is altered in most multiple sclerosis (MS) lesions, gadolinium enhancement is seen only in acute lesions. In this study, we aimed to investigate gadolinium-induced changes in T1 relaxation time in MS lesions on 7-tesla (7T) MRI as a means to quantify BBB breakdown in non-enhancing MS lesions. Forty-seven participants with MS underwent 7T MRI of the brain with a magnitude-prepared rapid acquisition of 2 gradient echoes (MP2RAGE) sequence before and after contrast. Subtraction of pre- and post-contrast T1 maps was used to measure T1 relaxation time change (ΔT1) from gadolinium. ΔT1 values were interrogated in enhancing white matter lesions (ELs), non-enhancing white matter lesions (NELs), and normal appearing white matter (NAWM) and metrics were compared to clinical data. ΔT1 was measurable in NELs (median: -0.139 (-0.304, 0.174) seconds; p < 0.001) and was negligible in NAWM (median: -0.001 (-0.036, 0.155) seconds; p = 0.516). Median ΔT1 in NELs correlated with disability as measured by Expanded Disability Status Scale (EDSS) (rho = -0.331, p = 0.026). Multiple measures of NEL ΔT1 variability also correlated with EDSS. NEL ΔT1 values were greater and more variable in patients with progressive forms of MS and greater in those not on MS treatment. Measurement of the changes in T1 relaxation time caused by contrast on 7T MP2RAGE reveals clinically relevant evidence of BBB breakdown in NELs in MS. This data suggests that NEL ΔT1 should be evaluated further as a biomarker for disease severity and treatment effect in MS.

Experience of application of T2-mapping MRI assessment of inflammatory myopathies

Specialized quantitative MRI techniques allow identifying structural changes in individual muscles in inflammatory myopathies.Aim. To evaluate the role of T2 mapping MRI and to evaluate specific changes in T2 relaxation time in patients with inflammatory myopathies at different stages of the disease process.Methods. T2 mapping technique for assessing structural changes in muscle tissues was optimized for the Philips “Ingenia” 3.0T MR scanner. T2 relaxation (T2rt) time of the thigh and lower leg muscles (muscule rectus femoris, m. vastus lateralis, m. adductor magnus, m. soleus, m. tibialis anterior, medial and lateral head of m. gastrocnemius) was assessed in the control group (n = 9) and the study group (n = 6). Patients recruited in the study group suffered from dermatomyositis and polymyositis of various severity.Results. The following values of T2rt were obtained in the control group: m.rectus femoris – 78.2±6.9 ms, m.vastus lateralis – 79.5±4.8 ms, m.adductor magnus – 77.1±4.4 ms, m. soleus – 92.9±4.3 ms, m. tibialis anterior – 89.4±1.3 ms, m.gastrocnemius medial head – 93.7±2.4 ms, m.gastrocnemius lateral head – 92.9±3.5 ms. Patients with polymyositis and dermatomyositis showed an increase in the signal intensity on STIR and PD-SPAIR in the structure of m.soleus, m. gastrocmenius, m.rectus femoris, as well as a significant increase in T2rt of 40–49% (p&lt;0.01). T2rt values did not differ in patients with polymyositis who received drug therapy and had clinical remission. Patients with dermatomyositis who had laboratory remission along with the deterioration reported an increase in T2rt in the structure of long spine muscles, m. rectus femoris and m. vastus lateralis equal to 15–25% (p&lt;0.05). However, none significant changes in the signal characteristics on STIR and PDSPAIR were reported.Conclusion. The sensitivity of the reported technique in the detection of sub-acute swelling of muscle tissue in the absence of significant changes in signal characteristics on routine MR sequences had been shown.

Higher Body Mass Index Is Associated With Biochemical Changes in Knee Articular Cartilage After Marathon Running: A Quantitative T2-Relaxation MRI Study

Background:More than 30 million individuals participate in marathon running every year worldwide. As the popularity of marathon running continues to increase, it is essential for the purposes of injury prevention to understand the effects of marathon running on the knee cartilage.Purpose:To investigate the immediate effects of marathon running on knee articular cartilage and to determine the relationship between body mass index and cartilage biochemical composition.Study Design:Descriptive laboratory study.Methods:T2-relaxation magnetic resonance imaging (MRI) of knees in 18 nonprofessional marathoners (mean age, 35.6 ± 6.4 years) was performed before and after a full-length marathon. Three-dimensional models of the knee articular cartilage were reconstructed and divided into different regions of interest. The 3-dimensional models were then applied to corresponding T2-relaxation MRI maps to calculate T2 values in each region of interest. The mean values of the T2-relaxation times in each region of interest before and after the marathon were compared by use of the paired Student t test. The Pearson correlation coefficient between T2 change and runner body mass index (BMI) was calculated.Results:Postmarathon T2-relaxation times were significantly higher than premarathon values for patellofemoral cartilage (32.6 ± 12.1 vs 34.1 ± 10.9 ms; P < .01) and medial tibial cartilage (35.6 ± 11.7 vs 34.6 ± 12.0 ms; P = .01). The greatest increase was observed in the anterior part of the medial tibial cartilage. No statistically significant changes were seen in the T2-relaxation times of the lateral tibial and femoral cartilage. Postmarathon T2-relaxation elevation in the anteromedial knee tibiofemoral joint cartilage strongly correlated with body weight (R = 0.6746; P = .03) and BMI (R = 0.6989; P = .001). Changes in T2-relaxation times did not correlate with marathon time, height, age, or sex in any regions of interest.Conclusion:Marathon running leads to immediate postmarathon elevated T2-relaxation values within knee articular cartilage, suggesting biochemical content alteration. Additionally, runners with higher BMI may have greater changes in cartilage biochemical composition after a marathon. Further studies should investigate whether these changes are sustained over time to determine the relationship between immediate biochemical changes in cartilage composition and cartilage degeneration.Clinical Relevance:Runners with a higher BMI may carry a higher risk of anteromedial tibiofemoral cartilage degeneration compared with runners with lower BMI.

A novel MRI analysis for assessment of microvascular vasomodulation in low-perfusion skeletal muscle

Compromised microvascular reactivity underlies many conditions and injuries, but its assessment remains difficult, particularly in low perfusion tissues. In this paper, we develop a new mathematical model for the assessment of vasomodulation in low perfusion settings. A first-order model was developed to approximate changes in T1 relaxation times as a result of vasomodulation. Healthy adult rats (N = 6) were imaged on a 3-Tesla clinical MRI scanner, and vasoactive response was probed on gadofosveset using hypercapnic gases at 20% and 5% CO2 to induce vasoconstriction and vasodilation, respectively. MRI included dynamic 3D T1 mapping and T1-weighted images during gas challenge; heart rate was continuously monitored. Laser Doppler perfusion measurements were performed to corroborate MRI findings. The model was able to identify hypercapnia-mediated vasoconstriction and vasodilation through the partial derivative frac{partial {T}_{1}}{partial t}. MRI on animals revealed gradual vasoconstriction in the skeletal muscle bed in response to 20% CO2 followed by gradual vasodilation on transitioning to 5% CO2. These trends were confirmed on laser Doppler perfusion measurements. Our new mathematical model has the potential for detecting microvascular dysfunction that manifests in the early stages across multiple metabolic and ischemic pathologies.

Role of T1 mapping to evaluate brain aging in a healthy population

PurposeTo investigate the relationship between healthy brain aging and T1 relaxation time obtained by T1 mapping. Materials and methodsA total of 211 (102 males, 109 females; age range: 20–89 years; mean age: 54 years) healthy volunteers underwent T1 mapping between July 2018 and January 2019. Regions of interest (ROIs) were placed on T1 maps in different anatomical regions, including the thalamus, putamen, globus pallidus, head of the caudate nucleus, nucleus accumbens, genu of the corpus callosum, and frontal lobe white matter (WM). Additionally, linear and quadratic regression analyses of ROIs were performed. ResultsThere were significant quadratic and negative linear correlations between T1 relaxation times in the thalamus, putamen, and age (p < .001). Although the nucleus accumbens did not show a significant relationship between T1 relaxation times and age by linear regression (p = .624), a statistically significant relationship was obtained by quadratic regression (p < .001). For the globus pallidus, head of the caudate nucleus, genu of the corpus callosum and frontal lobe WM the quadratic regression analysis showed a better relationship than the linear correlation analysis. ConclusionAge-related changes in T1 relaxation time vary by location in GM and WM.

Dorsal hippocampal changes in T2 relaxation times are associated with early spatial cognitive deficits in 5XFAD mice

T2 relaxation time (T2) alterations may serve as markers for early detection and disease progression monitoring by reflecting brain microstructural integrity in Alzheimer’s disease (AD). However, the characteristics of T2 alterations during the early stage of AD remain elusive. We explored T2 alterations and their possible correlations with cognitive function in 5XFAD mice at early ages (1, 2, 3, and 5 months of age). Voxel-based analysis (VBA) and region of interest (ROI) analysis showed a decreased T2 in the hippocampus of 2-, 3-, and 5-month-old 5XFAD mice compared to those of controls. The dorsal hippocampal T2 decreased earlier than the ventral hippocampus T2. A significant correlation was observed between Morris water maze (MWM) test cognitive behavior and the dorsal hippocampus T2 in 5XFAD mice. These results indicated that the microstructural integrity of brain tissues, particularly the hippocampus, was impaired early and the impairment became more extensive and severe during disease progression. Furthermore, the dorsal hippocampus is a crucial component involved in spatial cognition impairment in young 5XFAD mice.

Longitudinal preclinical magnetic resonance imaging of diffuse tumor burden in intramedullary myeloma following bortezomib therapy.

Multiple myeloma (MM) is a largely incurable, debilitating hematologic malignancy of terminally differentiated plasma cells in the bone marrow (BM). Identification of therapeutic response is critical for improving outcomes and minimizing costs and off-target toxicities. To assess changes in BM environmental factors and therapy efficacy, there is a need for noninvasive, nonionizing, longitudinal, preclinical methods. Here, we demonstrate the feasibility of preclinical magnetic resonance imaging (MRI) for longitudinal imaging of diffuse tumor burden in a syngeneic, immunocompetent model of intramedullary MM. C57Bl/KaLwRij mice were implanted intravenously with 5TGM1-GFP tumors and treated with a proteasome inhibitor, bortezomib, or vehicle control. MRI was performed weekly with a Helmholtz radiofrequency coil placed on the hind leg. Mean normalized T1-weighted signal intensities and T2 relaxation times were quantified for each animal following manual delineation of BM regions in the femur and tibia. Finally, tumor burden was quantified for each tissue using hematoxylin and eosin staining. Changes in T2 relaxation times correlated strongly to cell density and overall tumor burden in the BM. Median T2 relaxation times and regional T1-weighted contrast uptake were shown to be most relevant in identifying posttherapy disease stage in this model of intramedullary MM. In summary, our results highlighted potential preclinical MRI markers for assessing tumor burden and BM heterogeneity following bortezomib therapy, and demonstrated the application of longitudinal imaging with preclinical MRI in an immunocompetent, intramedullary setting.

Assessing effects of scanner upgrades for clinical studies.

Scanner upgrades due to software and hardware changes are an inevitable part of MR research and, without quality assurance protocols, can jeopardize studies. To evaluate changes in T1 relaxation time by inversion recovery (IR) and variable flip angle (VFA) measurements on a 3T system that underwent an "everything but the magnet" upgrade. Longitudinal. An International Society of Magnetic Resonance in Medicine / National Institute of Standards and Technology (ISMRM/NIST) system phantom with repeated measurements across multiple (n = 3) days. T1 IR, VFA at 3T. The T1 measurements by IR and VFA were compared with the nuclear magnetic resonance (NMR) measurements, which constitute the known values for the ISMRM/NIST system phantom, to determine the measurement error. Descriptive. The T1 VFA measurement errors were distributed around zero (-15% to +10%) on the original system and then the errors were distributed entirely above zero post-upgrade (+5% to 30%). The T1 IR results had a dramatic increase in error distribution (±5% original, ±20% post-upgrade) prior to the identification of signal saturation as an issue. Once the signal saturation was accounted for, the T1 IR errors decreased to ±10% post-upgrade. The T1 VFA measurement differences between the original and post-upgrade systems can be entirely attributed to contributions from B1 . The T1 IR measurements demonstrate the need for quantitative quality assurance (QA) processes. The site under study passed the QA protocols in place, which did not identify the increased T1 error, nor the signal saturation issue. To improve on this study, we would make systematic, quantitative measurements at intervals less than a year and following any hardware or software upgrade. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2019;50:1948-1954.

Quantifying T2 relaxation time changes within lesions defined by apparent diffusion coefficient in grey and white matter in acute stroke patients

The apparent diffusion coefficient (ADC) of cerebral water, as measured by diffusion MRI, rapidly decreases in ischaemia, highlighting a lesion in acute stroke patients. The MRI T2 relaxation time changes in ischaemic brain such that T2 in ADC lesions may be informative of the extent of tissue damage, potentially aiding in stratification for treatment. We have developed a novel user-unbiased method of determining the changes in T2 in ADC lesions as a function of clinical symptom duration based on voxel-wise referencing to a contralateral brain volume. The spherical reference method calculates the most probable pre-ischaemic T2 on a voxel-wise basis, making use of features of the contralateral hemisphere presumed to be largely unaffected. We studied whether T2 changes in the two main cerebral tissue types, i.e. in grey matter (GM) and white matter (WM), would differ in stroke.Thirty-eight acute stroke patients were accrued within 9 h of symptom onset and scanned at 3 T for 3D T1-weighted, multi b-value diffusion and multi-echo spin echo MRI for tissue type segmentation, quantitative ADC and absolute T2 images, respectively. T2 changes measured by the spherical reference method were 1.94 ± 0.61, 1.50 ± 0.52 and 1.40 ± 0.54 ms h−1 in the whole, GM, and WM lesions, respectively. Thus, T2 time courses were comparable between GM and WM independent of brain tissue type involved. We demonstrate that T2 changes in ADC-delineated lesions can be quantified in the clinical setting in a user unbiased manner and that T2 change correlated with symptom onset time, opening the possibility of using the approach as a tool to assess severity of tissue damage in the clinical setting.

MRI assessment of changes in adipose tissue parameters after bariatric surgery.

Bariatric surgery and other therapeutic options for obese patients are often evaluated by the loss of weight, reduction of comorbidities or improved quality of life. However, little is currently known about potential therapy-related changes in the adipose tissue of obese patients. The aim of this study was therefore to quantify fat fraction (FF) and T1 relaxation time by magnetic resonance imaging (MRI) after Roux-en-Y gastric bypass surgery and compare the resulting values with the preoperative ones. Corresponding MRI data were available from 23 patients (16 females and 7 males) that had undergone MRI before (M0) and one month after (M1) bariatric surgery. Patients were 22–59 years old (mean age 44.3 years) and their BMI ranged from 35.7–54.6 kg/m2 (mean BMI 44.6 kg/m2) at M0. Total visceral AT volumes (VVAT-T, in L) were measured by semi-automatic segmentation of axial MRI images acquired between diaphragm and femoral heads. MRI FF and T1 relaxation times were measured in well-defined regions of visceral (VAT) and subcutaneous (SAT) adipose tissue using two custom-made analysis tools. Average BMI values were 45.4 kg/m2 at time point M0 and 42.4 kg/m2 at M1. Corresponding VVAT-T values were 5.94 L and 5.33 L. Intraindividual differences in both BMI and VVAT-T were highly significant (p<0.001). Average relaxation times T1VAT were 303.7 ms at M0 and 316.9 ms at M1 (p<0.001). Corresponding T1SAT times were 283.2 ms and 280.7 ms (p = 0.137). Similarly, FFVAT differences (M0: 85.7%, M1: 83.4%) were significant (p <0.01) whereas FFSAT differences (M0: 86.1, M1: 85.9%) were not significant (p = 0.517). In conclusion, bariatric surgery is apparently not only related to a significant reduction in common parameters of adipose tissue distribution, here BMI and total visceral fat volume, but also significant changes in T1 relaxation time and fat fraction of visceral adipose tissue. Such quantitative MRI measures may potentially serve as independent biomarkers for longitudinal and cross-sectional measurements in obese patients.

Maturation-Related Changes in T2 Relaxation Times of Cartilage and Meniscus of the Pediatric Knee Joint at 3 T.

The objective of our study was to use a T2 mapping sequence performed at 3 T to investigate changes in the composition and microstructure of the cartilage and menisci of the pediatric knee joint during maturation. This retrospective study was performed of MRI examinations of 76 pediatric knees without internal derangement in 72 subjects (29 boys [mean age, 12.5 years] and 43 girls [mean age, 13.0 years]) who were evaluated with a sagittal T2 mapping sequence. T2 relaxation time values were quantitatively measured in eight cartilage subregions and in the medial and lateral menisci. Wilcoxon rank sum and Kruskal-Wallis tests were used to analyze the relationship between cartilage and meniscus T2 relaxation time values and sex and skeletal maturation, respectively. A multivariate linear regression model was used to investigate the independent association between cartilage T2 relaxation time values and age, weight, and body mass index (BMI [weight in kilograms divided by the square of height in meters]). There were no significant sex differences (p = 0.26-0.91) in T2 relaxation time values for cartilage or meniscus. T2 relaxation time values in each individual cartilage subregion significantly decreased (p < 0.001) with progressive maturation. T2 relaxation time values in the lateral meniscus significantly increased (p = 0.001) with maturation, whereas T2 relaxation time values in the medial meniscus did not significantly change (p = 0.82). There was a significant association (p < 0.001) between cartilage T2 relaxation time values and age independent of weight and BMI, but no significant association between cartilage T2 relaxation time values and weight (p = 0.06) and BMI (p = 0.20) independent of age. Cartilage T2 relaxation time values significantly decreased in all cartilage subregions and meniscus T2 relaxation time values significantly increased in the lateral meniscus during maturation. These changes in T2 relaxation time values reflect age-related changes in tissue composition and microstructure.

Value of gadoxetate disodium-enhanced magnetic resonance on hepatobiliary phase T1 mapping for predicting liver injury

Objective: To evaluate the measured value of gadoxetic disodium - enhanced T1-weighted magnetic resonance for the prediction of liver damage (LD) including liver fibrosis and inflammation. Methods: Retrospectively analyzed laboratory data of 115 patients with pathological results including prothrombin time (PT), albumin, serum total bilirubin level (TBil), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and magnetic resonance measurements (T1 measurement before and after enhancement and hepatobiliary specific phase T1pre, T1post, and changes in T1 relaxation time before and after enhancement were measured). The correlation between LD and magnetic resonance measurements was assessed by Spearman's correlation. All cases were divided into two groups: LD < 1 and LD≥1 (n1 = 26, n2 = 89), and the mean value of both groups was compared by t-test or Mann-Whitney U test. The independent influence factors of LD were obtained by binary logistic regression model. The area under receiver operating characteristics (AUROC) curve was performed on T1pre, T1post, and variation values. Results: Spearman's correlation test showed that T1post and variation values ​​were significantly associated with LD, and the correlation coefficients were 0.435, -0.353 and P < 0.05, respectively. The mean values ​​of T1post, variation values, PT, albumin, ALT and AST were statistically significant (P < 0.05). Binary logistic regression model showed T1post (P = 0.006), PT (P = 0.003), and AST (P = 0.032) were independent influencing factors of LD. T1- post contrast was good predictor of liver damage (AUC = 0.800). Conclusion: T1-post contrast predicts the existence of liver damage and provides useful information for clinical diagnosis and treatment.