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Exercise intolerance is a common adverse effect of childhood cancer, contributing to impaired health and well-being. While reduced aerobic fitness has been attributed to central cardiovascular deficiencies, the involvement of peripheral musculature has not been investigated. We studied peripheral muscle function in children following cancer treatment using noninvasive phosphorus-31 magnetic resonance spectroscopy. Ten acute lymphoblastic leukemia (ALL) and 1 lymphoma patient 8 to 18 years of age who completed treatment 6 to 36 months prior and 11 healthy controls participated in the study. Phosphorus-31 magnetic resonance spectroscopy was used to characterize muscle bioenergetics at rest and following an in-magnet knee-extension exercise. Exercise capacity was evaluated using a submaximal graded treadmill test. Both analysis of variance and Cohen d were used as statistical methods to determine the statistical significance and magnitude of differences, respectively, on these parameters between the patient and control groups. The patients treated for ALL and lymphoma exhibited lower anaerobic function ( P =0.14, d =0.72), slower metabolic recovery ( P =0.08, d =0.93), and lower mechanical muscle power ( d =1.09) during exercise compared with healthy controls. Patients demonstrated lower estimated VO 2peak (41.61±5.97 vs. 47.71±9.99 mL/min/kg, P =0.11, d =0.76), lower minutes of physical activity (58.3±35.3 vs. 114.8±79.3 min, P =0.12, d =0.99) and higher minutes of inactivity (107.3±74.0 vs. 43.5±48.3 min, d =1.04, P0.05). Children treated for ALL and lymphoma exhibit altered peripheral skeletal muscle metabolism during exercise. Both deconditioning and direct effects of chemotherapy likely contribute to exercise intolerance in this population.

BACKGROUND Persons with hemophilia experience hemarthrosis, which can lead to cartilage degeneration, causing physical impairment. MRI T2 mapping has the potential to be used as a tool to evaluate early arthropathic changes and cartilage degeneration in patients with hemophilia. PURPOSE To assess the value of MRI-T2 mapping as a tool for investigating the cartilage status of children and adolescents with hemophilic arthropathy. STUDY TYPE Prospective, cross-sectional. SUBJECTS Twenty-eight boys with hemophilia (aged 5-17 years) and 23 healthy boys (aged 7-17 years). FIELD STRENGTH/SEQUENCES A multiecho spin-echo T2 -weighted gradient echo sequence was used on a 3.0T magnet. ASSESSMENT MRI-T2 maps of ankle (tibia-talus) (n = 19) or knee (femur-tibia) (n = 9) cartilage were assessed in hemophilia and healthy groups. An anatomically-based MRI score was also assigned to each ankle/knee. STATISTICAL TESTS Pearson's correlation coefficient (r), linear regression, intraclass correlation coefficient (ICC), and analysis of variance (ANOVA) test. RESULTS Negative associations between age and ankle/knee cartilage T2 relaxation times were found in hemophilia (r = -0.72 [P = 0.03] to -0.55 [P = 0.01]) and healthy (r = -0.84 [P

Background: Exercise intolerance is a common side-effect of treatment for childhood leukemia and lymphoma and contributes to adverse health and well-being during survivorship. While central, cardiovascular contributors to fitness have been shown to be impaired, the peripheral muscular factors have not been studied in this population. Therefore, peripheral muscular function in children after leukemia and lymphoma treatment remains unstudied. Procedure: Eleven leukemia and lymphoma patients aged 8-18 years old who completed treatment 6-36 months prior and 11 healthy controls were included in analysis. 31P-MRS was used to characterize muscle bioenergetic metabolism at rest and after in-magnet knee extension exercise. General exercise capacity was assessed using a submaximal graded treadmill test and overall physical activity participation was assessed using the Habitual Activity Estimation Scale (HAES). Results: The patients treated for leukemia and lymphoma exhibited lower anaerobic function (d=0.72), slower metabolic recovery (d=0.93), and lower mechanical muscle power (d=1.09) during in-magnet knee extension exercise compared with the healthy control group. Lower estimated VO2peak (41.61 ± 5.97 vs. 47.71 ± 9.99 ml.min-1.kg-1, d=0.76), lower self-reported minutes of physical activity (58.3 ± 35.3 vs. 114.8 ± 79.3 minutes, d=0.99) and higher minutes of inactivity (107.3 ± 74.0 vs. 43.5 ± 48.3 minutes, d=1.04, p

Bone imaging is currently the best non-invasive way to assess changes to bone associated with aging or chronic disease. However, common imaging techniques such as dual energy x-ray absorptiometry are associated with limitations. Magnetic resonance imaging (MRI) is a radiation-free technique that can measure bone microarchitecture. However, published MRI bone assessment protocols use specialized MRI coils and sequences and therefore have limited transferability across institutions. We developed a protocol on a Siemens 3 Tesla MRI machine, using a commercially available coil (Siemens 15 CH knee coil), and manufacturer supplied sequences to acquire images at the tibia. We tested the reproducibility of the FSE and the GE Axial sequences and hypothesized that both would generate reproducible trabecular bone parameters. Eight healthy adults (age 25.5 ± 5.4 years) completed three measurements of each MRI sequence at the tibia. Each of the images was processed for 8 different bone parameters (such as volumetric bone volume fraction). We computed the coefficient of variation (CV) and intraclass correlation coefficients (ICC) to assess reproducibility and reliability. Both sequences resulted in trabecular parameters that were reproducible (CV 80% for all). Our study is one of the first to report that a commercially available MRI protocol can result in reproducible data, and is significant as MRI may be an accessible method to measure bone microarchitecture in clinical or research environments. This technique requires further testing, including validation and evaluation in other populations., Highlights • Trabecular bone is difficult to measure using commercial MRI techniques • Reproducibility of a MRI protocol measuring trabecular bone was assessed • Tibia trabecular bone was reproducible using a knee coil and a FSE Axial sequence • Tibia trabecular bone was reproducible using a knee coil and a GE Axial sequence

Background Malignant hyperthermia (MH), a pharmacogenetic disorder of skeletal muscle, presents with a potentially lethal hypermetabolic reaction to certain anesthetics. However, some MH-susceptible patients experience muscle weakness, fatigue, and exercise intolerance in the absence of anesthetic triggers. The objective of this exploratory study was to elucidate the pathophysiology of exercise intolerance in patients tested positive for MH with the caffeine-halothane contracture test. To this end, we used phosphorus magnetic resonance spectroscopy, blood oxygen level-dependent functional magnetic resonance imaging (MRI), and traditional exercise testing to compare skeletal muscle metabolism in MH-positive patients and healthy controls. Methods Skeletal muscle metabolism was assessed using phosphorus magnetic resonance spectroscopy and blood oxygen level-dependent functional MRI in 29 MH-positive patients and 20 healthy controls. Traditional measures of physical capacity were employed to measure aerobic capacity, anaerobic capacity, and muscle strength. Results During 30- and 60-second exercise, MH-positive patients had significantly lower ATP production via the oxidative pathway compared to healthy controls. MH-positive patients also had a longer recovery time with blood oxygen level-dependent functional MRI compared to healthy controls. Exercise testing revealed lower aerobic and anaerobic capacity in MH-positive patients compared to healthy controls. Conclusions Results of this exploratory study suggest that MH-positive patients have impaired aerobic metabolism compared to healthy individuals. This could explain the exercise intolerance exhibited in MH-susceptible patient population.

Haematopoietic stem cell transplant (HSCT) is an intensive therapy for some pediatric hematological illnesses. Survivors are at risk for adverse effects including exercise intolerance. Peripheral tissue dysfunction may contribute to exercise intolerance, therefore, we examined the feasibility of a magnetic resonance spectroscopy (MRS) protocol to evaluate skeletal muscle metabolism in children post-HSCT. We measured demographic characteristics, aerobic exercise capacity (YMCA protocol), and skeletal muscle function in response to exercise (MRS, Siemens 3T MRI) in five children post-allogeneic HSCT and five age/body mass index-matched healthy controls (HCs). The mean age (&plusmn, standard deviation) of the HSCT group and HC group were 11 &plusmn, 1.2 and 12.8 &plusmn, 2.4 years, respectively. Children post-HSCT had a lower peak aerobic exercise capacity compared to HCs (27.8 &plusmn, 3.4 vs. 40.3 &plusmn, 8.1 mL kg&minus, 1 min&minus, 1, respectively, p = 0.015). Exercise MRS testing protocols were successfully completed by all HSCT and HC participants, however, MRS-derived skeletal muscle metabolism variables were not different between the two groups. In conclusion, the use of exercise protocols in conjunction with MRS to assess peripheral skeletal muscle metabolism was achievable in children post-HSCT. In the future, larger studies should determine if skeletal muscle function is associated with exercise capacity in children post-HSCT.

Introduction The influence of 4 commonly used fixed orthodontic appliances on artifact formation and diagnostic quality of magnetic resonance (MR) images of the head produced by a 3-T MR scanner was studied. Methods Stainless steel brackets, ceramic brackets, combination of ceramic brackets and steel molar tubes, and multistranded steel mandibular lingual retainers were embedded into custom-made trays for each of 10 adult subjects. Head MR scans of 9 regions were acquired for each subject wearing these trays. Sagittal T1-weighted, axial T2-weighted, axial gradient-recalled, axial diffusion-weighted, noncontrast axial MR angiography, and axial fluid-attenuated inversion recovery MR sequences were included. Two neuroradiologists evaluated image distortions and diagnostic qualities of the 1314 acquired images (13860 image slices). Results The images were affected by appliance, head region, and MR sequence. Stainless steel brackets and molar tubes affected the images the most, and ceramic brackets caused minimal image distortion. Conclusions Head MR images are differentially affected by orthodontic appliances. The appliance, region imaged, and MR sequence should be considered before imaging patients wearing fixed orthodontic appliances.

Background Obesity is associated with cardiometabolic disturbances, which may have significant implications for musculoskeletal health and exercise tolerance. Objective We sought to determine the association between muscle structure, function, and metabolism in adolescents across the weight spectrum. Methods This cross-sectional case–control study included overweight and obese participants (n = 24) 8–18 years of age with a body mass index (BMI) ≥ 85th percentile for age and gender, and non-obese participants (n = 24) with a BMI

The clinimetric properties of blood oxygen level‒dependent (BOLD) magnetic resonance imaging (MRI) for assessment of musculoskeletal changes have been poorly investigated. The study objectives were to assess the interframework reliability of data acquisition of BOLD MRI and to test its convergent validity in chronic arthritis in a rabbit model of inflammatory arthritis as compared with corresponding clinical and laboratory measures.One of the knees of 12 New Zealand male white rabbits was injected with a 1% carrageenin solution, and the contralateral (control) one was not. Twelve rabbits were euthanized on day 28 of arthritis (chronic arthritis). Clinical (joint diameters), laboratory (serum amyloid A concentration), and BOLD MRI measurements were obtained on days 0, 1, and 28 of arthritis. Twenty paradigms of data acquisition and analysis were applied.The most reliable MRI parameters set, regardless of threshold values used for data analysis, was spiral technique (level 1), 40 ms of echo time (level 2), 60 seconds of on_ and off_ paradigm (level 3) and carbogen mixture of gases (95% O2 + 5% CO2) (level 4). With regard to construct validity, BOLD imaging correlated moderately (r = -.54, P.0001) with knee diameters, and weakly (r = -.35, P = .01) with laboratory indices (high threshold for analysis).BOLD MRI has a substantial or excellent interframework reliability for assessment of arthritic rabbit knees; however, it correlates only moderately or poorly with clinical and laboratory measures. Nevertheless, this study supports further validation of BOLD MRI for assessment of soft tissue changes in a rabbit model of arthritis.

Previous studies have reported differences in muscle function and metabolism between patients with cystic fibrosis (CF) and healthy controls (HC), but it is currently unknown whether these abnormalities are specific to CF or also seen in other airway diseases. In this study, we used magnetic resonance spectroscopy (MRS) during exercise to assess muscle metabolism in CF patients. Twenty patients with CF and 20 age, gender, and habitual activity-matched HCs and a respiratory disease comparison group with primary ciliary dyskinesia (PCD; n = 10) were studied. Phosphorus MRS (P-MRS) was used to characterize muscle bioenergetic metabolism at rest and after high-, moderate-, and low-intensity exercise. CF patients exhibited lower resting ATP/phosphocreatine (PCr) ratio and significantly higher end-exercise pH values compared with both HC and PCD patients. Both CF and PCD patients demonstrated significantly slower PCr recovery time constants after high-intensity exercise. Our results suggest that not only there are specific abnormalities of muscle metabolism in CF patients but also there is a nonspecific impact of respiratory disease on muscle function.

We report a unique case of cobblestone complex using post-mortem MR and diffusion tensor imaging to assess the laminar organization of the fetal cerebrum. The imaging findings were correlated with autopsy findings. Abnormal cortical development in cobblestone complex resulted in disruption of normal laminar organization of the fetal brain, which was seen as interruption and nodularity of the high-signal T1 cortical band with increased anisotropy and medium diffusivity extending beyond the cortical band into the cerebral mantle on post-mortem MR and diffusion tensor imaging.

Obesity is associated with cardiometabolic disturbances, which may have significant implications for musculoskeletal health and exercise tolerance.We sought to determine the association between muscle structure, function, and metabolism in adolescents across the weight spectrum.This cross-sectional case-control study included overweight and obese participants (n = 24) 8-18 years of age with a body mass index (BMI) ≥ 85th percentile for age and gender, and non-obese participants (n = 24) with a BMI 85bese and overweight patients had similar age, height, and physical activity to non-obese controls, but obese and overweight participants exhibited higher insulin resistance. Obese and overweight participants had longer PCr recovery than non-obese controls following 5x30s of moderate-intensity exercise (51.2 ± 20.1 s vs. 23.9 ± 7.5 s, p = 0.004). In univariate correlation analysis, impaired PCr recovery was associated with a higher BMI z-score (rA slower phosphocreatine recovery following aerobic exercise is strongly associated with increasing adiposity. A slower metabolic recovery following aerobic exercise stress suggests that endurance exercise training in obese adolescents may be an optimal strategy to target exercise intolerance in this cohort.

Our aim was to test the feasibility of blood oxygen level dependent magnetic resonance imaging (BOLD MRI) and dynamic contrast-enhanced (DCE) MRI to monitor periarticular hypoxic/inflammatory changes over time in a juvenile rabbit model of arthritis. We examined arthritic and contralateral nonarthritic knees of 21 juvenile rabbits at baseline and days 1,14, and 28 after induction of arthritis by unilateral intra-articular injection of carrageenin with BOLD and DCE MRI at 1.5 Tesla (T). Nine noninjected rabbits served as controls. Associations between BOLD and DCE-MRI and corresponding intra-articular oxygen pressure (PO2) and blood flow [blood perfusion units (BPU)] (polarographic probes, reference standards) or clinical–histological data were measured by correlation coefficients. Percentage BOLD MRI change obtained in contralateral knees correlated moderately with BPU on day 0 (r = −0.51, p = 0.02) and excellently on day 28 (r = −0.84, p = 0.03). A moderate correlation was observed between peak enhancement DCE MRI (day 1) and BPU measurements in arthritic knees (r = 0.49, p = 0.04). In acute arthritis, BOLD and DCE MRI highly correlated (r = 0.89, p = 0.04; r = 1.0, p

BOLD MRI contrast results from changes in the microvascular ratio of oxyhemoglobin (oxyHb) to deoxyhemoglobin (deoxyHb) (1). DeoxyHb is paramagnetic, which results in a local bulk magnetic susceptibility effect and subsequent MRI signal change in T(2)*-weighted functional MRI scans (1). Although BOLD contrast has been studied extensively in functional MRI studies of the brain, limited investigation has been performed in other tissues. Juvenile idiopathic arthritis (JIA) is the most common rheumatic disorder of childhood (2), with the knee being the most frequently affected joint (3). With the increasing availability and use of disease-modifying and antirheumatic biologic drugs for the treatment of JIA (4), the early determination of joint abnormality has become extremely important. Given the lack of clinical and laboratory tests that enable the functional evaluation of perisynovial oxygenation in JIA, the use of BOLD MRI to measure early soft tissue physiological imbalances due to hypoxia is appealing (5). In inflammatory arthritis, the increased metabolic demand of the inflamed synovium and the inadequate delivery of oxygen caused by poor perfusion through the inflamed synovium (5) result in hypoxia within the inflamed joint in the acute stage of arthritis. Consequently, the synovial blood flow increases to compensate for the hypoxic status of the joint. In JIA, despite the local hyperemia, the synovial capillaries develop an abnormal oxygen transportation capability (5,6), which may result in abnormal concentrations of oxyHb and deoxyHb at the capillary level. To date, no single imaging assay or surrogate marker has been demonstrated to adequately reflect the spectrum of metabolic events involved in inflammatory arthritis. We hypothesized that BOLD MRI would be able to reflect the state of oxygenation in the microcirculation of periarticular tissues in JIA children at 1.5 Tesla as previously shown for other pathological states (7). Previous studies of our group in rabbit models of inflammatory arthritis demonstrated the feasibility (8), criteria validity (9), interframework reliability for data acquisition (10), combination of region-of-interest (ROI)-related reading parameters that provide the highest accuracy for discrimination of the presence or absence of arthritis in acute and subacute stages of the disease (11), and responsiveness of the technique to short-term joint temperature changes (12). However, no previous study has demonstrated whether the BOLD MRI technique is able to differentiate inflammatory from healthy perisynovial tissue at 1.5 Tesla and determine interval soft tissue changes as a result of intraarticular corticosteroid injections in the knees of JIA patients. In the present paper, we describe the BOLD MRI methodology and preliminary results on the feasibility of using BOLD MRI at 1.5 Tesla to measure the responsiveness (sensitivity to change) of the interval of soft-tissue changes in JIA patients with unilateral knee arthritis following intraarticular injection of corticosteroids as a proof of concept. We knew in advance the expected effectiveness of the injection procedure, which reduces synovial inflammation in JIA in approximately 76% of cases at 6 weeks after the injection (13).

Context: Turner syndrome (TS) is a chromosomal disorder occurring in approximately 1 in 2500 live births. Individuals with TS report lower levels of physical activity than healthy control (HC) subjects. Cardiorespiratory limitations may contribute to the observed reduction in physical activity. Objective: The objective of this study was to compare muscle metabolism of patients with TS vs HC subjects before and after exercise using exercise testing, magnetic resonance imaging, and magnetic resonance spectroscopy techniques. Design: We hypothesized that girls and adolescents with TS would have muscle metabolic abnormalities not present in the HC population. Setting: The research was conducted at the Hospital for Sick Children in Toronto, Ontario, Canada. Participants: Fifteen participants with TS were age-, activity-, and body mass index Z-score–matched with 16 HC subjects. Main Outcome Measures: 31P magnetic resonance spectroscopy was used to characterize muscle metabolism at rest and after 30 seconds of high-intensity exercise, 60 seconds of moderate-intensity exercise, and 5 minutes of low-intensity exercise. Results: While achieving the same workloads, participants with TS exhibited a greater difference between rest and end-exercise pH compared with HC subjects after 30 seconds (TS, 0.29 ± 0.04; HC, 0.21 ± 0.08; P = .03) and 90 seconds (TS, 0.47 ± 0.22; HC, 0.32 ± 0.13; P = .02) of exercise. During the 5-minute exercise test, similar workloads were achieved between groups; however, ATP production was greater in participants with TS vs the HC subjects via all 3 bioenergetic pathways (total ATP: TS, 0.90 ± 0.34; HC, 0.60 ± 0.25; P = .01). Conclusions: The results of this study suggest that patients with TS exhibit greater anaerobic stress during exercise than HC subjects, which may lead to symptoms of increased muscle fatigue with short bursts of activity. Recovery metabolism after exercise appears to be similar between participants with TS and HC subjects, which is suggestive of normal mitochondrial metabolism and oxygen transport.

Blood-oxygen-level-dependent (BOLD) MRI has the potential to identify regions of early hypoxic and vascular joint changes in inflammatory arthritis. There is no standard protocol for analysis of BOLD MRI measurements in musculoskeletal disorders. To optimize the following BOLD MRI reading parameters: (1) statistical threshold values (low, r > 0.01 versus high, r > 0.2); (2) summary measures of BOLD contrast (percentage of activated voxels [PT%] versus percentage signal difference between on-and-off signal intensities [diff_on_off]); and (3) direction of BOLD response (positive, negative and positive + negative). Using BOLD MRI protocols at 1.5 T, arthritic (n = 21) and contralateral (n = 21) knees of 21 juvenile rabbits were imaged at baseline and on days 1, 14 and 28 after a unilateral intra-articular injection of carrageenan. Nine non-injected rabbits served as external control knees (n = 18). By comparing arthritic to contralateral knees, receiver operating characteristic curves were used to determine diagnostic accuracy. Using diff_on_off and positive + negative responses, a threshold of r > 0.01 was more accurate than r > 0.2 (P = 0.03 at day 28). Comparison of summary measures yielded no statistically significant difference (P > 0.05). Although positive + negative (AUC = 0.86 at day 28) and negative responses (AUC = 0.90 at day 28) for PT% were the most diagnostically accurate, positive + negative responses for diff_on_off (AUC = 0.78 at day 28) also had acceptable accuracy. The most clinically relevant reading parameters included a lower threshold of r > 0.01 and a positive + negative BOLD response. We propose that diff_on_off is a more clinically relevant summary measure of BOLD MRI, while PT% can be used as an ancillary measure.

Because of the ability of blood-oxygen-level-dependent (BOLD) MRI to assess blood oxygenation changes within the microvasculature, this technique holds potential for evaluating early perisynovial changes in inflammatory arthritis. To evaluate the feasibility of BOLD MRI to detect interval perisynovial changes in knees of rabbits with inflammatory arthritis. Rabbit knees were injected with albumin (n = 9) or saline (n = 6) intra-articularly, or were not injected (control knees, n = 9). Except for two rabbits (albumin-injected, n = 2 knees; saline-injected, n = 2 knees) that unexpectedly died on days 7 and 21 of the experiment, respectively, all other animals were scanned with BOLD MRI on days 0, 1, 7, 14, 21 and 28 after induction of arthritis. T2*-weighted gradient-echo MRI was performed during alternate 30 s of normoxia/hyperoxia. BOLD MRI measurements were compared with clinical, laboratory and histological markers. Percentage of activated voxels was significantly greater in albumin-injected knees than in contralateral saline-injected knees (P = 0.04). For albumin-injected knees (P

Parallel imaging provides faster scanning at the cost of reduced signal-to-noise ratio (SNR) and increased artifacts.To compare the diagnostic performance of two parallel MRI protocols (PPs) for assessment of pathologic knees using an 8-channel knee coil (reference standard, conventional protocol [CP]) and to characterize the SNR losses associated with parallel imaging.Two radiologists blindly interpreted 1.5 Tesla knee MRI images in 21 children (mean 13 years, range 9-18 years) with clinical indications for an MRI scan. Sagittal proton density, T2-W fat-saturated FSE, axial T2-W fat-saturated FSE, and coronal T1-W (NEX of 1,1,1) images were obtained with both CP and PP. Images were read for soft tissue and osteochondral findings.There was a 75% decrease in acquisition time using PP in comparison to CP. The CP and PP protocols fell within excellent or upper limits of substantial agreement: CP, kappa coefficient, 0.81 (95% CIs, 0.73-0.89); PP, 0.80-0.81 (0.73-0.89). The sensitivity of the two PPs was similar for assessment of soft (0.98-1.00) and osteochondral (0.89-0.94) tissues. Phantom data indicated an SNR of 1.67, 1.6, and 1.51 (axial, sagittal and coronal planes) between CP and PP scans.Parallel MRI provides a reliable assessment for pediatric knees in a significantly reduced scan time without affecting the diagnostic performance of MRI.

Our objective was to analyze MRI contrast-enhancement patterns in arthritic and nonarthritic knees and the relationship of those patterns with clinical, laboratory, and histologic synovium markers.Dynamic contrast-enhanced MRI was performed in nine arthritic and three nonarthritic knees of juvenile rabbits. A two-compartment pharmacokinetic model of signal intensity-time data was implemented to generate parametric maps of signal slope, maximal percentage of signal change, capillary permeability, leakage space volume, and time-to-peak. MRI values were compared with clinical, laboratory, and histologic markers for evaluation of synovial changes during the progression of arthritis.Parametric maps of capillary permeability and signal slope depicted significant differences between arthritic and nonarthritic knees. Arthritic knees showed increased capillary permeability (p = 0.006) and signal slope (p = 0.01) with time after onset of disease as opposed to nonarthritic knees (permeability, p = 0.65; slope, p = 0.56). Significant correlations were found between temporal changes in capillary permeability (p = 0.002), signal slope (p = 0.003), and serum concentrations of amyloid A. No relationship was noted between any MRI parameters and histologic scores. The discriminative power of MRI indexes varied according to the stage of arthritis: time-to-peak was most accurate for differentiation of presence versus absence of arthritis in early arthritis (day 1, p = 0.0002), and signal slope was most accurate in midterm arthritis (day 14, p = 0.001).In vivo capillary permeability and signal slope have distinctive dynamic MRI properties. The accuracy of MRI parameters for diagnostic evaluation of experimental arthritis differs according to the stage of disease.