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.
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 populations during exercise. Our objective was to document femoral arterial blood flow at rest and following exercise in a pediatric population using phase contrast MRI, and to present test‐retest reliability data for this method.
A multimodality instrument that integrated optical or near-infrared spectroscopy into a magnetic resonance imaging (MRI) breast coil was used to perform a pilot study of image-guided spectroscopy on ...cancerous breast tissue. These results are believed to be the first multiwavelength spectroscopic images of breast cancer using MRI-guided constraints, and they show the cancer tumor to have high hemoglobin and water values, decreased oxygen saturation, and increased subcellular granularity. The use of frequency-domain diffuse tomography methods at many wavelengths provides the spectroscopy required for recovering maps of absorbers and scattering spectra, but the integration with MRI allows these data to be recovered on an image field that preserves high resolution and fuses the two data sets together. Integration of molecular spectroscopy into standard clinical MRI can be achieved with this approach to spectral tomography.
A new approach to spectroscopic imaging was developed to detect and discriminate microscopic pathologies in resected breast tissues; diagnostic performance of the prototype system was tested in 27 ...tissues procured during breast conservative surgery.
A custom-built, scanning in situ spectroscopy platform sampled broadband reflectance from a 150-μm-diameter spot over a 1 × 1 cm(2) field using a dark field geometry and telecentric lens; the system was designed to balance sensitivity to cellular morphology and imaging the inherent diversity within tissue subtypes. Nearly 300,000 broadband spectra were parameterized using light scattering models and spatially dependent spectral signatures were interpreted using a cooccurrence matrix representation of image texture.
Local scattering changes distinguished benign from malignant pathologies with 94% accuracy, 93% sensitivity, 95% specificity, and 93% positive and 95% negative predictive values using a threshold-based classifier. Texture and shape features were important to optimally discriminate benign from malignant tissues, including pixel-to-pixel correlation, contrast and homogeneity, and the shape features of fractal dimension and Euler number. Analysis of the region-based diagnostic performance showed that spectroscopic image features from 1 × 1 mm(2) areas were diagnostically discriminant and enabled quantification of within-class tissue heterogeneities.
Localized scatter-imaging signatures detected by the scanning spectroscopy platform readily distinguished benign from malignant pathologies in surgical tissues and showed new spectral-spatial signatures of clinical breast pathologies.
The feasibility of spatial frequency domain imaging (SFDI) for breast surgical margin assessment was evaluated in tissue-simulating phantoms and in fully intact lumpectomy specimens at the time of ...surgery. Phantom data was evaluated according to contrast-detail resolution, quantitative accuracy and model-data goodness of fit, where optical parameters were estimated by minimizing the residual sum of squares between the measured modulation amplitude and its solutions, modeled according to diffusion and scaled-Monte Carlo simulations. In contrast-detail phantoms, a 1.25-mm-diameter surface inclusion was detectable for scattering contrast >28%; a fraction of this scattering contrast (7%) was detectable for a 10 mm surface inclusion and at least 33% scattering contrast was detected up to 1.5 mm below the phantom surface, a probing depth relevant to breast surgical margin assessment. Recovered hemoglobin concentrations were insensitive to changes in scattering, except for overestimation at visible wavelengths for total hemoglobin concentrations <15 μM. The scattering amplitude increased linearly with scattering concentration, but the scattering slope depended on both the particle size and number density. Goodness of fit was comparable for the diffusion and scaled-Monte Carlo models of transport in spatially modulated, near-infrared reflectance acquired from 47 lumpectomy tissues, but recovered absorption parameters varied more linearly with expected hemoglobin concentration in liquid phantoms for the scaled-Monte Carlo forward model. SFDI could potentially reduce the high secondary excision rate associated with breast conserving surgery; its clinical translation further requires reduced image reconstruction time and smart inking strategies.
We sought to define the prevalence of definitive end states and their determinants in children given a diagnosis of pulmonary atresia and intact ventricular septum during the neonatal period.
Between ...1987 and 1997, 408 neonates with pulmonary atresia and intact ventricular septum were entered into a prospective study by 33 institutions. Competing risks analysis was used to demonstrate the prevalence of 6 end states. Factors predictive of attaining each end state were identified by means of multivariable analysis with bootstrap validation.
Overall survival was 77% at 1 month, 70% at 6 months, 60% at 5 years, and 58% at 15 years. Prevalence of end states 15 years after entry were as follows: 2-ventricle repair, 33%; Fontan repair, 20%; 1.5-ventricle repair, 5%; heart transplant, 2%; death before reaching definitive repair, 38%; and alive without definitive repair, 2%. Patient-related factors discriminating among end states primarily included adequacy of right-sided heart structures, degree of aberration of coronary circulation, low birth weight, and tricuspid valve regurgitation. After adjusting for these factors, 2 institutions were predictive of 2-ventricle repair, 1 of Fontan repair, and 6 of death before definitive repair. Two institutions were predictive of both 2-ventricle and Fontan repair. These 2 institutions achieved a higher risk-adjusted prevalence of definitive repair and a lower prevalence of prerepair mortality.
Characteristics of neonates with pulmonary atresia and intact ventricular septum predict type of definitive repair. A morphologically driven institutional protocol emphasizing both 2-ventricle and Fontan pathways might mitigate the negative effect of unfavorable morphology. In the current era, 85% of neonates are likely to reach a definitive surgical end point, with 2-ventricle repair achieved in an estimated 50%.
We sought to determine whether a 9-day remote ischemic preconditioning (IPC) causes improvements in exercise performance, energetics, and blood pressure. Ten participants (mean age 24 ± 4 years) had ...no changes in aerobic capacity (preintervention: 38 ± 10 mL/(kg·min)
–1
vs. postintervention: 38 ± 10 mL/(kg·min)
–1
), blood pressure (preintervention: 112 ± 7/66 ± 6 mm Hg vs. postintervention: 112 ± 10/62 ± 5 mm Hg), cardiac phosphocreatinine-to-adenosine–triphosphate ratio (preintervention: 2.1 ± 0.5 vs. postintervention: 2.3 ± 0.4), and postexercise skeletal muscle phosphocreatine recovery (preintervention: 34 ± 11 s vs. postintervention: 31 ± 11 s). Short-term remote IPC may be ineffective in improving these outcomes.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A method for estimating Mie theory scattering parameters from diffuse light tomography measurements in breast tissue is discussed. The approach provides an estimate of the mean particle size and ...number density given assumptions about the index of refraction change expected in lipid-membrane-bound scatterers. When using a sparse number of wavelengths in the reduced scattering spectra, the parameter extraction technique is limited to representing a continuous distribution of scatterer sizes that appears to be dominated by an exponential decrease with increasing particle size. The fitting method is tested on simulated data and then on Intralipid-based tissue-phantom data, giving a mean particle size of 93+/-17 nm, which is in excellent agreement with expectations. The approach is also applied retrospectively to breast tissue spectra acquired from normal healthy volunteers, where the average particle size and number density were found to be in the range of 20 to 1400 nm. Grouping of the data based on radiographic breast density, as a surrogate measure of tissue composition yielded values of 20 to 65, 25 to 200, 140 to 1200, and 150 to 1400 nm, respectively, for the four BI-RADS (American College of Radiology Breast Imaging Reporting and Data System) density classifications of extremely dense, heterogeneously dense, scattered, and fatty. These results are consistent with the microscopic characteristics of each breast type given the expected progression from predominantly collagenous connective tissue (extremely dense category) to increasing proportions of glandular epithelium and fat (intermediate density categories) to predominantly fat (fatty category).
31
Phosphorus Magnetic Resonance Spectroscopy (
31
P MRS) is a well-validated, noninvasive magnetic resonance imaging technique that has been used to determine cardiac and skeletal muscle energy ...metabolism in vivo. Few studies have documented cardiac energy metabolism in adolescents and young adult cohorts. This cross-sectional study sought to explore the association among cardiac energy metabolism, skeletal muscle energy metabolism, moderate-to-vigorous physical activity (MVPA), and age in adolescents and young adults. Ten healthy, active participants (40% male) with a mean ± SD age of 18.6 ± 4.9 years, body mass index of 21.1 ± 2.4 kg·m
−2
, and median MVPA level of 83 min per weekday (lower quartile: 45 min per weekday; upper quartile: 114 min per weekday) completed the following study assessments: a
31
P MRS scan to determine cardiac and skeletal muscle energy metabolism, cardiopulmonary exercise testing to determine aerobic power, and accelerometry to determine MVPA over 7 days. Resting cardiac energy metabolism, as measured by the ratio of phosphocreatine to adenosine triphosphate (PCr/ATP
β
, mean ± SD: 2.76 ± 0.65), was positively associated with skeletal muscle aerobic oxidative function (Estimate (SE): −0.1(0.01), p < 0.001), as measured by PCr recovery half-time following 60 s of exercise (34 ± 9 s). This association, which was adjusted for peak aerobic power, MVPA, age, and sex, suggests the development of an association between cardiac and skeletal muscle health at any early age. Larger studies are needed to establish normative data for both physically active and sedentary males and females that may be used for comparison in future studies involving clinical cohorts.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
39.
Structured light scatteroscopy Krishnaswamy, Venkataramanan; Elliott, Jonathan T; McClatchy, David M ...
Journal of biomedical optics,
07/2014, Letnik:
19, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A new imaging approach, structured light scatteroscopy (SLS), is demonstrated, which offers rapid wide-field imaging of microscopic morphological variations in bulk tissue surfaces. Elastic ...scattering of light offers exquisite sensitivity to ultrastructural changes at multiple size scales ranging from nanometers to millimeters, but in bulk tissues the confounding effects of molecular absorption and strong multiple scattering of light often lead to a dramatic reduction in scatter contrast and specificity. It is demonstrated that the SLS using structured high spatial frequency illumination and detection to probe the tissue achieves direct, absorption-independent, high-resolution maps of the scattering response. The scattering response is observed to be dependent on both the wavelength and spatial frequency of choice, indicating a potential for multiscale probing of ultrastructural changes in superficial tissue layers. This methodology can be easily applied in most wide-field imaging systems.
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.
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