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Although hyperpolarized (HP) 129Xe ventilation MRI can be carried out within a breath hold, it is still challenging for many sick patients. Compressed sensing (CS) is a viable alternative to accelerate this approach. However, undersampled images with identical sampling ratios differ from one another. Twenty subjects (n = 10 healthy and n = 10 patients with asthma) were scanned using a GE MR750 3 T scanner, acquiring fully sampled 2D multi‐slice HP 129Xe lung ventilation images (10 s breath hold, 128 × 80 (FE × PE—frequency encoding × phase encoding) and 16 slices). Using fully sampled data, 500 variable‐density Cartesian random undersampling patterns were generated, each at eight different sampling ratios from 10% to 80%. The parallel imaging and compressed sensing (PICS) command from BART was employed to reconstruct undersampled data. The signal to noise ratio (SNR), structural similarity index measurement (SSIM) and sidelobe to peak ratio of each were subsequently compared. There was a high degree of variation in both SNR and SSIM results from each of the 500 masks of each sampling rate. As the undersampling increases, there is more variation in the quantifying metrics, for both healthy and asthmatic individuals. Our study shows that random undersampling poses a significant challenge when applied at sampling ratios less than 60%, despite fulfilling CS's incoherency criteria. Such low sampling ratios will result in a large variety of undersampling patterns. Therefore, skipped segments of k‐space cannot be allowed to happen randomly at low sampling rates. By optimizing the sampling pattern, CS will reach its full potential and be able to be applied to a highly undersampled 129Xe lung dataset. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Cerebral small vessel disease (SVD) and amyloid beta (Aβ) pathology frequently co‐exist. The impact of concurrent pathology on the pattern of hippocampal atrophy, a key substrate of memory impacted early and extensively in dementia, remains poorly understood. METHODS: In a unique cohort of mixed Alzheimer's disease and moderate–severe SVD, we examined whether total and regional neuroimaging measures of SVD, white matter hyperintensities (WMH), and Aβ, as assessed by 18F‐AV45 positron emission tomography, exert additive or synergistic effects on hippocampal volume and shape. RESULTS: Frontal WMH, occipital WMH, and Aβ were independently associated with smaller hippocampal volume. Frontal WMH had a spatially distinct impact on hippocampal shape relative to Aβ. In contrast, hippocampal shape alterations associated with occipital WMH spatially overlapped with Aβ‐vulnerable subregions. DISCUSSION: Hippocampal degeneration is differentially sensitive to SVD and Aβ pathology. The pattern of hippocampal atrophy could serve as a disease‐specific biomarker, and thus guide clinical diagnosis and individualized treatment strategies for mixed dementia. [ABSTRACT FROM AUTHOR]

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Magnetic Resonance Imaging (MRI) is well‐suited for imaging peripheral blood flow due to its non‐invasive nature and excellent spatial resolution. Although MRI is routinely used in adults to assess physiological changes in chronic diseases, there are currently no MRI‐based data quantifying arterial flow in pediatric or adolescent populations during exercise. Therefore the current research sought to document femoral arterial blood flow at rest and following exercise in a pediatric‐adolescent population using phase contrast MRI, and to present test‐retest reliability data for this method. Ten healthy children and adolescents (4 male; mean age 14.8 ± 2.4 years) completed bloodwork and resting and exercise MRI. Baseline images consisted of PC‐MRI of the femoral artery at rest and following a 5 × 30 s of in‐magnet exercise. To evaluate test‐retest reliability, five participants returned for repeat testing. All participants successfully completed exercise testing in the MRI. Baseline flow demonstrated excellent reliability (ICC = 0.93, p = 0.006), and peak exercise and delta rest‐peak flow demonstrated good reliability (peak exercise ICC = 0.89, p = 0.002, delta rest‐peak ICC = 0.87, p = 0.003) between‐visits. All three flow measurements demonstrated excellent reliability when assessed with coefficients of variance (CV's) (rest: CV = 6.2%; peak exercise: CV = 7.3%; delta rest‐peak: CV = 7.1%). The mean bias was small for femoral arterial flow. There was no significant mean bias between femoral artery flow visits 1 and 2 at peak exercise. There were no correlations between age or height and any of the flow measurements. There were no significant differences between male and female participants for any of the flow measurements. The current study determined that peripheral arterial blood flow in children and adolescents can be evaluated using non‐invasive phase contrast MRI. The MRI‐based techniques that were used in the current study for measuring arterial flow in pediatric and adolescent patients demonstrated acceptable test‐retest reliability both at rest and immediately post‐exercise. [ABSTRACT FROM AUTHOR]

Overuse knee injuries are common in bicycling and are often attributed to poor bicycle-fit. Bicycle-fit for knee health focuses on setting saddle height to elicit a minimum knee flexion angle of 25-40°. Equations to predict saddle height include a single input, resulting in a likely suboptimal bicycle-fit. The purpose of this work was to develop an equation to predict saddle height from anthropometrics, bicycle geometry, and user-defined joint kinematics. Methods: Forty healthy adults (17 women, 23 men; mean (SD): 28.6 (7.2) years; 24.2 (2.6) kg/m2) participated. Kinematic analyses were conducted for 18 three-minute bicycling bouts including all combinations of 3 horizontal and 3 vertical saddle positions, and 2 crank arm lengths. For both minimum and maximum knee flexion, predictors were identified using Least Absolute Shrinkage and Selection Operator (LASSO) regression, and final models were fit using linear regression. Secondary analyses determined if saddle height equations were sex dependent. Results: The equation to predict saddle position from minimum knee flexion angle (R2=0.97; root mean squared error (RMSE) = 1.15 cm) was: Saddle height (cm) = 7.41 + 0.82(inseam cm) – 0.1(minimum knee flexion °) + 0.003(inseam cm)(seat tube angle °). The maximum knee flexion equation (R2=0.97; RMSE=1.15 cm) was: Saddle height (cm) = 41.63 + 0.78(inseam cm) – 0.25(maximum knee flexion °) + 0.002(inseam cm)(seat tube angle °). The saddle height equations were not dependent on sex. Conclusions: These equations provide a novel, practical strategy for bicycle-fit that accounts for rider anthropometrics, bicycle geometry and user-defined kinematics. Highlights This work developed simple equations to prescribed bicycle saddle height that elicits desired knee kinematics. Separate equations are presented for prescribing minimum or maximum knee flexion angle. Equations can be generalized to riders of both sexes, and a breadth of anthropometrics and ages. [ABSTRACT FROM AUTHOR]

Despite the technical challenges that require lengthy acquisitions to overcome poor signal‐to‐noise ratio (SNR), sodium (23Na) magnetic resonance imaging (MRI) is an intriguing area of research due to its essential role in human metabolism. Low SNR images can impact the measurement of the point‐spread function (PSF) by adding uncertainty into the resulting quantities. Here, we present methods to calculate the PSF by using the modulation transfer function (MTF), and a 3D‐printed line‐pair phantom in the context of 23Na MRI. A simulation study investigated the effect of noise on the resulting MTF curves, which were derived by direct modulation (DM) and a method utilizing Fourier harmonics (FHs). Experimental data utilized a line‐pair phantom with nine spatial frequencies, filled with different concentrations (15, 30, and 60 mM) of sodium in 3% agar. MTF curves were calculated using both methods from data acquired from density‐adapted 3D radial projections (DA‐3DRP) and Fermat looped orthogonally encoded trajectories (FLORET). Simulations indicated that the DM method increased variability in the MTF curves at all tested noise levels over the FH method. For the experimental data, the FH method resulted in PSFs with a narrower full width half maximum with reduced variability, although the improvement in variability was not as pronounced as predicted by simulations. The DA‐3DRP data indicated an improvement in the PSF over FLORET. It was concluded that a 3D‐printed line‐pair phantom represents a convenient method to measure the PSF experimentally. The MTFs from the noisy images in 23Na MRI have reduced variability from a FH method over DM. [ABSTRACT FROM AUTHOR]

Purpose: Dynamic phosphorus MR spectroscopic imaging (31P‐MRSI) experiments require temporal resolution on the order of seconds to concurrently assess different muscle groups. A highly accelerated pulse sequence combining flyback echo‐planar spectroscopic imaging (EPSI) and compressed sensing was developed and tested in a phantom and healthy humans during an exercise‐recovery challenge of the lower leg muscles, using a clinical 3T MRI. Methods: A flyback EPSI readout designed to achieve 2.25 × 2.25 cm2 resolution over a 18 × 18 cm2 field of view (i.e., 8 × 8 matrix) was combined with compressed sensing through the inclusion of pseudorandom gradient blips to sub‐sample the ky‐kt dimensions by a factor of 2.7×, achieving a temporal resolution of 9 s. The sequence was first tested in a phantom to assess performance compared to fully sampled EPSI (fidEPSI) and phase encoded chemical shift imaging (fidCSI). Then, tests were performed in 11 healthy volunteers during an exercise‐recovery challenge of the lower leg muscles. Voxels containing tissue from different muscle groups were evaluated measuring percentage phosphocreatine (%PCr) depletion, time constant of PCr recovery (τPCr) and intracellular pH at rest and following exercise. Results: The sequence was capable to track the dynamic PCr response of multiple muscles simultaneously. No statistical differences were found in the metabolite ratio, pH or linewidth when compared with fidEPSI and fidCSI in the phantom study. Dynamic experiments showed differences in PCr depletion when comparing soleus with gastrocnemius muscles. Intracellular pH, τPCr and %PCr decrease were consistent with reported values. Conclusion: Highly accelerated 31P‐MRSI combining flyback EPSI and compressed sensing is capable of assessing concurrent energy metabolism in multiple muscle groups using a clinical 3T MR system. [ABSTRACT FROM AUTHOR]

Objectives Myofascial pain syndrome is one of the most common causes of chronic pain and is highlighted by the presence of myofascial trigger points. The current practice of diagnosing myofascial pain syndrome among clinicians involves manual detection of myofascial trigger points, which can be inconsistent. However, the detection process can be strengthened with the assistance of ultrasound (US). Therefore, this study aimed to characterize the upper trapezius by using quantitative techniques in healthy asymptomatic individuals with neck pain. Methods Study participants were recruited on the basis of the inclusion and exclusion criteria established, and US images of the trapezius, along the axial and longitudinal orientations, were obtained. Each set was obtained by 2 investigators: experienced and inexperienced personnel. Results Fifteen participants were recruited. The mean gray scale US echo intensity distribution obtained was 41.9. A paired t test of the global mean echo intensity value obtained for each image from the US operators did not show any significant difference ( P = .77). A t test was performed, comparing the echo intensity of the group of patients with neck pain and healthy control participants, and the difference was found to be significant ( P = .052). The median blob area was 2.71. The quartile range for the blob area was 1.72 for the 25th percentile to 4.90 for the 75th percentile. Conclusions This study demonstrated that quantitative analysis of the echo intensity of US images can provide important information. However, further research is necessary to explore the relationships among sex, age, blob area, count, body mass index, regional anatomy, and extent of training or exercise of the particular muscle. [ABSTRACT FROM AUTHOR]

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 < 85th percentile. Body composition, physical activity, peak aerobic capacity, cardiometabolic blood markers and insulin resistance (measured by the homeostatic model assessment of insulin resistance, HOMA‐IR), skeletal muscle mitochondrial oxidative capacity (via 31Phosphorous‐Magnetic Resonance Spectroscopy, 31P‐MRS, to assess phosphocreatine (PCr) recovery after exercise), and extramyocellular and intramyocellular lipid (IMCL) levels (via 1Hydrogen‐MRS) were assessed. Stepwise regression was performed to examine the factors associated with oxidative capacity. Results: bese 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 (rs = 0.51, p < 0.001), circulating triglycerides (rs = 0.41, p = 0.005), and HOMA‐IR (rs = 0.46, p = 0.001). In stepwise multivariate regression analysis, impaired PCr recovery was associated with a higher BMI z‐score (β = 0.47, p = 0.002), but not insulin resistance (β = 0.07, p = 0.07) or circulating triglycerides (β = 0.16 p = 0.33). Conclusion: A 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. [ABSTRACT FROM AUTHOR]

Purpose: To develop an inexpensive magnetic resonance imaging (MRI)-compatible electrical muscle stimulation (EMS) unit and test it for safety and efficacy.Materials and Methods: A simple MRI-compatible EMS device was developed using radiofrequency (RF) translucent electrodes at 3T. RF heating concerns were assessed using optical temperature measurements at electrode sites, during scanning of a phantom. EMS efficacy and consistency was investigated through in vivo (n = 5) measures of 31 P-MRS phosphocreatine (PCr) reduction, and altered blood oxygen level-dependent (BOLD) signal and the results were compared to effects from equivalent voluntary effort on the same subjects.Results: The presence of an EMS pulse did not interfere with the T2 * signal in a phantom. However, signal-to-noise ratio (SNR) was reduced by 70% at electrode sites, but only by 10% 4 cm distally. Under RF intense conditions, the temperature at the electrode site increased by only 4.7°C over a 16-minute time span. In vivo muscle stimulation resulted in 13.5 ± 1.8% reduction in PCr, which was not significantly (P < 0.195) different from voluntary contraction. Reproducible muscle BOLD signal changes following EMS were noted, with a maximal increase of 10.0 ± 2.6% seen in the central soleus. For soleus and gastrocnemius compartments, EMS produced significantly higher BOLD signal change compared to voluntary contraction (P < 0.05).Conclusion: A safe and inexpensive MRI-compatible EMS unit can be easily built for evaluating muscle function and metabolism within a 3T MRI scanner. Clinical applications might include evaluating skeletal muscle function in patients with limited or absent voluntary skeletal motor function or inadequate exercise capacity. J. Magn. Reson. Imaging 2016;44:1530-1538. [ABSTRACT FROM AUTHOR]

Purpose: To explore the effect of diffusion tensor imaging (DTI) acquisition parameters on principal and minor eigenvector stability within human lower leg skeletal muscles.Materials and Methods: Lower leg muscles were evaluated in seven healthy subjects at 3T using an 8-channel transmit/receive coil. Diffusion-encoding was performed with nine signal averages (NSA) using 6, 15, and 25 directions (NDD). Individual DTI volumes were combined into aggregate volumes of 3, 2, and 1 NSA according to number of directions. Tensor eigenvalues (λ1 , λ2 , λ3 ), eigenvectors (ε1 , ε2 , ε3 ), and DTI metrics (fractional anisotropy [FA] and mean diffusivity [MD]) were calculated for each combination of NSA and NDD. Spatial maps of signal-to-noise ratio (SNR), λ3 :λ2 ratio, and zenith angle were also calculated for region of interest (ROI) analysis of vector orientation consistency.Results: ε1 variability was only moderately related to ε2 variability (r = 0.4045). Variation of ε1 was affected by NDD, not NSA (P < 0.0002), while variation of ε2 was affected by NSA, not NDD (P < 0.0003). In terms of tensor shape, vector variability was weakly related to FA (ε1 :r = -0.1854, ε2 : ns), but had a stronger relation to the λ3 :λ2 ratio (ε1 :r = -0.5221, ε2 :r = -0.1771). Vector variability was also weakly related to SNR (ε1 :r = -0.2873, ε2 :r = -0.3483). Zenith angle was found to be strongly associated with variability of ε1 (r = 0.8048) but only weakly with that of ε2 (r = 0.2135).Conclusion: The second eigenvector (ε2 ) displayed higher directional variability relative to ε1 , and was only marginally affected by experimental conditions that impacted ε1 variability. [ABSTRACT FROM AUTHOR]

Background: Small vessel disease (SVD) often co‐exists with Alzheimer's disease (AD) pathology (up to 60%) and may facilitate AD progression. However, SVD is currently not integrated as a pathological factor within the ATN research criteria. Up to now, the majority of studies that investigated effects of SVD on brain atrophy and cognition were limited to either AD cohorts with low SVD burden (e.g., ADNI) or cognitively normal elderly with high SVD burden. Thus, there is a need to investigate the effects of SVD in a cohort spanning low to severe SVD and amyloid‐beta pathology. Method: Our study included 118 subjects in total. Fifty‐nine subjects were recruited in a multi‐site study (MITNEC) from dementia and SVD‐stroke clinics (64% amyloid‐beta+) who had severe SVD burden as quantified by white matter hyperintensity volumes [WMH; median(IQR): 30.2(22.2)cm3] and Fazekas score 2.5‐3. In addition, we included 59 cognitively normal/early‐MCI subjects from ADNI (44% amyloid‐beta+) with low‐to‐moderate WMH [median(IQR): 5.8(9.1)cm3]. We performed vertex‐wise regressions, investigating associations of cortical thickness with amyloid‐beta (18F‐florbetapir‐SUVRpons) or vascular burden (WMH), corrected for WMH or amyloid‐beta, respectively, and age, sex, education. Further, mediation analyses investigated whether the effects of amyloid‐beta or vascular burden on cognition (MMSE, MoCA, Trails‐B, semantic fluency, ANART, and Boston‐naming) were mediated by cortical thickness. Result: We observed a significant effect of vascular burden on cortical thickness independent of amyloid‐beta. This effect was stronger than the vascular‐independent effect of amyloid‐beta on thickness (Fig. 1). Furthermore, we observed additive effects of vascular burden and amyloid‐beta on cognition (semantic fluency: ß=‐0.29 [p=0.002] and ß=‐0.27 [p=0.001], respectively; Trails‐B: ß=+0.18 [p=0.03] and ß=+0.22 [p=0.02], respectively). Here, the effects on semantic fluency were significantly mediated by cortical thickness (vascular→thickness→semantic: 35% mediation, 95%CI[‐0.19,‐0.02]; amyloid‐beta→thickness→semantic: 19% mediation, 95%CI[‐0.11,‐0.003]) (Fig. 1). Conclusion: In our study of mixed AD/SVD and control subjects, the effect of SVD burden (WMH) exceeded the effect of amyloid‐beta on neurodegeneration alone. Furthermore, vascular burden contributed to semantic loss both directly and through its impact on neurodegeneration. As such, the presence of cerebrovascular comorbidities supports the idea of combinational therapeutic approaches where SVD factors may be targeted alongside amyloid‐beta to halt neurodegeneration and cognitive decline. [ABSTRACT FROM AUTHOR]

Objective Decline in cognitive function begins by the 40s, and may be related to future dementia risk. We used data from a community-representative study to determine whether there are age-related differences in simple cognitive and gait tests by the 40s, and whether these differences were associated with covert cerebrovascular disease on magnetic resonance imaging (MRI). Methods Between 2010 and 2012, 803 participants aged 40 to 75 years in the Prospective Urban Rural Epidemiological (PURE) study, recruited from prespecified postal code regions centered on 4 Canadian cities, underwent brain MRI and simple tests of cognition and gait as part of a substudy (PURE-MIND). Results Mean age was 58 ± 8 years. Linear decreases in performance on the Montreal Cognitive Assessment, Digit Symbol Substitution Test (DSST), and Timed Up and Go test of gait were seen with each age decade from the 40s to the 70s. Silent brain infarcts were observed in 3% of 40- to 49-year-olds, with increasing prevalence up to 18.9% in 70-year-olds. Silent brain infarcts were associated with slower timed gait and lower volume of supratentorial white matter. Higher volume of supratentorial MRI white matter hyperintensity was associated with slower timed gait and worse performance on DSST, and lower volumes of the supratentorial cortex and white matter, and cerebellum. Interpretation Covert cerebrovascular disease and its consequences on cognitive and gait performance and brain atrophy are manifest in some clinically asymptomatic persons as early as the 5th decade of life. Ann Neurol 2015;77:251-261 [ABSTRACT FROM AUTHOR]

Introduction: Structural evidence of exercise-induced muscle disruption has traditionally involved histological analysis of muscle tissue obtained by needle biopsy, however, there are multiple limitations with this technique. Recently, diffusion tensor magnetic resonance imaging (DT-MRI) has been successfully demonstrated to noninvasively assess skeletal muscle abnormalities induced by traumatic injury. Methods: To determine the potential for DT-MRI to detect musculoskeletal changes after a bout of eccentric exercise, 10 healthy men performed 300 eccentric actions on an isokinetic dynamometer. DT-MRI measurements and muscle biopsies from the vastus lateralis were obtained before and 24 h post-exercise. Results: Z-band streaming was higher 24 h post-exercise compared with baseline ( P < 0.05). The histological indices of damage coincided with changes in DT-MRI parameters of fractional anisotropy (FA) and apparent diffusion coefficient; reflecting altered skeletal muscle geometry ( P < 0.05). Z-band streaming quantified per fiber correlated with FA (r = −0.512; P < 0.05). Conclusions: DT-MRI can detect changes in human skeletal muscle structure following eccentric exercise. Muscle Nerve 46: 42-50, 2012 [ABSTRACT FROM AUTHOR]

Purpose: To measure interindividual, repositioning, and time-of-day effects of single voxel PRESS ( Point RESolved Spectroscopy) proton magnetic resonance spectroscopy (1H-MRS) acquisition of the anterior cingulate cortex (AC) in healthy human subjects. Materials and Methods: AC 1H-MRS measurements were performed in 15 healthy adult volunteers using a short echo PRESS sequence (GE Healthcare 3 Tesla, TE/TR = 30/2500 ms, 192 acquisitions, 6 cm3 voxels). For each individual, a total of eight spectra were obtained during two identical scanning sessions separated by 3.5 h. In each, two consecutive AC spectra were acquired. After the first two scans, the subject left the scanner, then immediately returned for repositioning and acquisition of two more consecutive spectra. The subject then left the imaging centre to return 3.5 h later for a repeated procedure. Spectroscopic postprocessing was done using LCmodel. Interindividual, repositioning and time-of-day effects were measured using restricted maximum likelihood (REML) models of variance components analysis, where response variables were levels of creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), myo-inositol (mI), choline (Cho), and the glutamate-glutamine complex (Glx). Results: Interindividual effects were markedly higher than time-of-day and repositioning effects for all metabolites. Conclusion: Our findings show that 1H-MRS measurements of the AC are sensitive to interindividual differences, while time of day and repositioning are markedly less important. J. Magn. Reson. Imaging 2010;32:276-282. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

MRI phase and magnitude images provide information about local magnetic field variation (ΔB0), which can consequently be used to understand tissue properties. Often, phase information is discarded. However, corrected phase images are able to produce contrast as a result of magnetic susceptibility differences and local field inhomogeneities due to the presence of diamagnetic and paramagnetic substances. Three-dimensional (3D) susceptibility weighted imaging (SWI) can be used to probe changes in MRI phase evolution and, subsequently, result in an alternate form of contrast between tissues. For example, SWI has been useful in the assessment of negative phase induced ΔB0 modulation due to the presence of paramagnetic substances such as iron. Very little, however, has been done to assess positive phase induced contrast changes resulting from the presence of diamagnetic substances such as precipitated calcium. As ductal carcinoma in situ, which is the precursor of invasive ductal cancer, is often associated with breast microcalcification, the authors proposed using SWI as a possible visualization technique. In this study, breast phantoms containing calcifications (0.4–1.5 mm) were imaged using mammography, computed tomography (CT), and SWI. Corrected phase and magnitude images acquired using SWI allowed identification and correlation of all calcifications seen on CT. As the approach is a 3D technique, it could potentially allow for more accurate localization and biopsy and maybe even reduce the use of gadolinium contrast. Furthermore, the approach may be beneficial to women with dense breast tissue where the ability to detect microcalcification with mammography is reduced. [ABSTRACT FROM AUTHOR]

We examined the neural substrate of motor response inhibition and performance monitoring in the stop signal task (SST) using event-related functional magnetic resonance imaging (fMRI). The SST involves a go task and the occasional requirement to stop the go response. We posit that both the go and the stop phases of the SST involve components of inhibition and performance monitoring. The goal of this study was to determine whether inhibition and performance monitoring during go and stop phases of the task activated different networks. We isolated go-phase activities underlying response withholding, monitoring, and sensorimotor processing and contrasted these with successful inhibition to identify the substrate of response inhibition. Error detection activity was isolated using trials in which a stop signal appeared but the response was executed. These trials were modeled as a hand-specific go trial followed by error processing. Cognitive go-phase processes included response withholding and monitoring and activated right prefrontal and midline networks. Response withdrawal additionally activated right inferior frontal gyrus and basal ganglia (caudate). Error detection invoked by failed inhibition activated dorsal anterior cingulate cortex (dACC) and right middle frontal Brodmann's area 9. Our results confirm that there are distinct aspects of inhibition and performance monitoring functions which come into play at various phases within a given trial of the SST, and that these are separable using fMRI. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To evaluate whether the BOLD signal from skeletal muscle can be modulated by exercise and ingestion of vasoactive substances. Materials and Methods The right calf muscles of healthy adult volunteers were imaged using a GE 1.5-Tesla scanner and a gradient-echo sequence with spiral readout. Time-varying changes in the BOLD signal were induced through cyclic phases of normoxia (90 seconds of 20.8% O2) and hyperoxia (45 seconds of 100% O2 at 22 L/minute). Superimposed on this paradigm were pre- and post-exercise regimes, with and without ingestion of caffeine (100 mg) or antihistamine (4 mg chlorpheniramine). The numbers of voxels within slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles that significantly responded to the paradigms were scored and compared using the AFNI software (NIMH). Results Cycling-inspired O2 produced a corresponding BOLD modulation that increased in magnitude with exercise. Chlorpheniramine significantly ( P < 0.01) prevented the overall increase in exercise-induced soleus muscle BOLD signal, while caffeine accentuated the increase ( P < 0.05) in the gastrocnemius relative to control (no vasomodulator) conditions. Conclusion BOLD signal changes with exercise can be modulated by standard doses of chlorpheniramine (antihis-tamine) and caffeine. We suggest that chlorpheniramine may act detrimentally on slow-twitch muscle contractility, while caffeine appears to improve fast-twitch muscle function. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To explore the capability and reliability of diffusion tensor magnetic resonance imaging (DTI) in the evaluation of human skeletal muscle injury. Materials and Methods DTI of four patients with gastrocnemius and soleus muscles injuries was compared to eight healthy controls. Imaging was performed using a GE 3.0T short-bore scanner. A diffusion-weighted 2D spin echo echo-planar imaging (EPI) pulse sequence optimized for skeletal muscle was used. From a series of axially acquired diffusion tensor images the diffusion tensor eigenparameters (eigenvalues and eigenvectors), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were calculated and compared for injured and healthy calf muscles. Two dimensional (2D) projection maps of the principal eigenvectors were plotted to visualize the healthy and pathologic muscle fiber architectures. Results Clear differences in FA and ADC were observed in injured skeletal muscle, compared to healthy controls. Mean control FA was 0.23 ± 0.02 for medial and lateral gastrocnemius (mg and lg) muscles, and 0.20 ± 0.02 for soleus (sol) muscles. In all patients FA values were reduced compared to controls, to as low as 0.08 ± 0.02. The ADC in controls ranged from 1.41 to 1.31 × 10-9 m2/second, while in patients this was consistently higher. The 2D projection maps revealed muscle fiber disorder in injured calves, while in healthy controls the 2D projection maps show a well organized (ordered) fiber structure. Conclusion DTI is a suitable method to assess human calf muscle injury. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

In this study, the development of white matter was studied using an optimized diffusion tensor imaging (DTI) protocol in 20 normal subjects (10–40 years old). The normal development of white matter tracts was addressed by comparing the diffusion anisotropy results between two sub–groups: eight adults (26–38 years old) and eight adolescents (13–15 years old). The difference in myelination extent between these two groups as indexed by the fractional anisotropy was identified by conducting a student t–test of the measured diffusion anisotropy maps. Significant differences (p <0.01) were detected in the gyrus frontalis medialis (GFM), gyrus temporalis medialis (GTM) and gyrus cinguli (GC), in addition to the developmental changes in corpus callosum. A brief overview of previous published DTI studies in developmental science and current progress in DTI techniques is also given at the end of this paper. It may be useful for readers interested in using DTI to study developmental problems but who are not familiar with the various technical aspects. [ABSTRACT FROM AUTHOR]

We aimed to determine the effectiveness of low volume resistance exercise, alone or in combination with a whey protein supplement, on muscle mass and strength after unilateral leg immobilization in humans. Sixteen recreationally active participants (23.9±5.0 yr; BMI = 25.4±3.6 kg·m-2) were divided into three groups: exercise (EX; n=6), whey protein supplementation with exercise (WHY+EX; n=6), and control (CON; n=4). All subjects wore a knee-immobilization brace and were non-weight bearing for 14 days. Exercise was one set of ten repetitions of leg press, knee extension, and seated calf raises every other day, at 80% of one repetition maximum. WHY+EX consumed 60g of whey protein daily while EX and CON consumed an isocaloric carbohydrate beverage. Immobilization induced a significant reduction (p<0.05) in thigh cross-sectional area (CSA), knee extensor strength, and plantar flexion strength in CON but not in EX and WHY+EX. There were significant losses in lower leg CSA for all three groups, with losses tending to be lower in both the EX and WHY+EX groups versus CON (p=0.065). We conclude that a low volume of resistance exercise is an effective countermeasure against atrophy and strength loss during immobilization. There was no additional benefit of a daily whey protein supplement in maintaining muscle mass or strength. [ABSTRACT FROM AUTHOR]