Larger and stronger muscles are positively associated with bone strength in the growing skeleton; however, less is known about the role of muscle properties on bone strength later in life. The primary objective of this study was to examine the relationship between muscle cross sectional area (MCSA), muscle force and rate of torque development (RTD) with bone strength indices (bone strength index (BSI) and strength strain index (SSI)) in the radius of healthy middle-aged adults. All bone and muscle measurements were determined in the non-dominant forearm in a sample of 40 healthy adults (23 men, 17 women: mean age 49.5, SD 2.3 yrs). Peripheral quantitative computer tomography (pQCT) was used to scan the distal and shaft sites of the radius bone in the forearm. MCSA was determined from the forearm shaft scan. Forearm muscle force was measured by hand grip dynamometry and RTD was obtained from isometric wrist flexion from an isokinetic dynamometry protocol. Hierarchical regression analyses were used to identify whether muscle properties (MCSA, grip force, and RTD) independently predicted radius bone strength indices (BSI and SSI), after adjusting for the confounders of sex, height and weight. Steps of the regression models that included sex, height, weight and a muscle property explained between 66% and 71% of variance in distal radius BSI and between 74% and 78% variance of estimated bone strength (SSI) at the shaft site (all steps p<0.001). MCSA explained a significant amount of variance in BSI (R2=0.08; p<0.01) and SSI (R2=0.04; p<0.05) at the radius. Grip force was also a significant predictor of SSI (R2=0.05; p<0.01) but not distal radius BSI (R2=0.03; p=0.07). Conversely, RTD explained a significant amount of variance in bone strength at the distal radius (R2=0.04; p<0.05), but not at the shaft (R2=0.01; p=0.17). These cross sectional findings support the theory that regional muscle size, force, and rate of torque development are related to estimated bone strength in the forearm at midlife. Further research should focus on targeted interventions to help determine which muscle property elicits a greater osteogenic response to optimize bone strength at distal and shaft sites of the radius.

Larger and stronger muscles are positively associated with bone strength in the growing skeleton; however, less is known about the role of muscle properties on bone strength later in life. The primary objective of this study was to examine the relationship between muscle cross sectional area (MCSA), muscle force and rate of torque development (RTD) with bone strength indices (bone strength index (BSI) and strength strain index (SSI)) in the radius of healthy middle-aged adults. All bone and muscle measurements were determined in the non-dominant forearm in a sample of 40 healthy adults (23 men, 17 women: mean age 49.5, SD 2.3 yrs). Peripheral quantitative computer tomography (pQCT) was used to scan the distal and shaft sites of the radius bone in the forearm. MCSA was determined from the forearm shaft scan. Forearm muscle force was measured by hand grip dynamometry and RTD was obtained from isometric wrist flexion from an isokinetic dynamometry protocol. Hierarchical regression analyses were used to identify whether muscle properties (MCSA, grip force, and RTD) independently predicted radius bone strength indices (BSI and SSI), after adjusting for the confounders of sex, height and weight. Steps of the regression models that included sex, height, weight and a muscle property explained between 66% and 71% of variance in distal radius BSI and between 74% and 78% variance of estimated bone strength (SSI) at the shaft site (all steps p<0.001). MCSA explained a significant amount of variance in BSI (R2=0.08; p<0.01) and SSI (R2=0.04; p<0.05) at the radius. Grip force was also a significant predictor of SSI (R2=0.05; p<0.01) but not distal radius BSI (R2=0.03; p=0.07). Conversely, RTD explained a significant amount of variance in bone strength at the distal radius (R2=0.04; p<0.05), but not at the shaft (R2=0.01; p=0.17). These cross sectional findings support the theory that regional muscle size, force, and rate of torque development are related to estimated bone strength in the forearm at midlife. Further research should focus on targeted interventions to help determine which muscle property elicits a greater osteogenic response to optimize bone strength at distal and shaft sites of the radius.

Bone health in the context of two common maladies, osteoporosis and obesity, has spurred research in the area of physical activity (PA) and bariatric surgery (BarS). Objectives: To examine: 1) relationships between PA and the skeleton utilizing the peripheral Quantitative Computed Tomography (pQCT) and Dual-energy X-ray Absorptiometry (DXA) in pre-menopausal women; 2) effects of adjustable gastric banding (AGB) vs. Roux-en-Y gastric bypass (RYGB) surgeries on pQCT and DXA measures; 3) 6-month time course changes on serum biomarkers of bone turnover and associated adipokines induced by AGB vs. RYGB. Methods: Standard DXA and pQCT measurements were taken for all subjects. PA tertiles (PA-L, PA-M, PA-H) were based on a calculated average MET-min/day determined from 4-d self-reported PA and pedometer step counts. For BarS subjects, bone measurements were taken pre-surgery, 3- and 6-months post-surgery along with serum (or plasma) from fasting blood draws, with ELISA assays for total OC, undercarboxylated OC, CTx, adiponectin, and leptin. Results: Minimal DXA differences between the highest and lowest PA tertiles were seen, while pQCT tibial measures and polar strength-strain index (SSIp) indicated differences along the tibial shaft. Comparing the two instruments and adjusting for BMI, the DXA leg and hip BMD and BMC showed differences (p<0.05) between PA-M and PA-L as well as PA-H and PA-L. Similarly, the pQCT tibial cortical area, BMC, and SSIp were progressively greater for the different levels of PA (p<0.05). 3- and 6-months post-BarS weight, fat-free mass, fat mass, central body fat, tibial and radial subcutaneous fat, and radial MCSA decreased (p<0.05). Comparing the AGB and RYGB and adjusting for weight, DXA BMC showed decreases (p<0.01) at both time points for RYGB. RYGB demonstrated differences (p<0.05) in bone measures at 3- and 6-months post-surgery along the tibial shaft that are indicative of increases in bone strength, and at 6-months, total OC, undercarboxylated OC, and HMW adiponectin increased, while leptin decreased. Conclusions: PA is associated with increases in bone, but pQCT data are more discriminatory and sensitive. 6-months post-RYGB, pQCT measures indicate increases in bone strength parameters, and greater bone adaptation was evidenced by biomarkers of increased osteoblastic activity. / Ph. D.

A asma é uma doença crônica das vias aéreas, cuja fisiopatologia compreende inflamação, hiper-responsividade e remodelação. As características clínicas e a espirometria são usadas para avaliar o controle da doença. Alguns asmáticos não conseguem controlar tomando altas doses de medicações de controle (asma de difícil controle). A tomografia computadorizada quantitativa de tórax (TCQ) é pouco usada na asma, mas pode fornecer biomarcadores da doença. Objetivos: Comparar os achados de TCQ de indivíduos sem doenças respiratórias (grupo controle - GC), com asma controlada (ABC) e com asma de difícil controle (ADC), visando prioritariamente parâmetros substitutivos do remodelamento das vias aéreas. Investigar se há correlações entre os parâmetros QCT e espirometria. Materiais e Métodos: Recrutamos sujeitos com ADC e ABC em um hospital terciário. Usamos registros médicos e convite pessoal para obter dados de CG. Todos os indivíduos foram submetidos a tomografia computadorizada de alta resolução e espirometria. Um software (Yacta) foi usado para obter dados de TCQ. O teste t de Student, o one-way ANOVA e o teste exato de Fisher foram realizados para comparar os dados dos grupos. Os coeficientes de correlação de Pearson foram calculados para avaliar as correlações entre os parâmetros espirométricos e TCQ. Resultados: O GC foi composto por 21 sujeitos; ABC, de 28 e ADC, de 27. Estes últimos eram mais idosos que GC e ABC (50,85 (10,11); 41,27 (11,57); 42,04 (10,11) anos; p = 0,002). A espessura relativa das vias aéreas (ERP3-8) foi significativamente diferente entre GC e ADC (45,31% (3,71); 49,38% (3,38); p = 0,001) e entre GC e ABC (45,31%, 71); 48,25 (4,51); p = 0,001). A espessura normalizada das vias aéreas (Pi10) foi significativamente diferente entre ADC e ABC (0,51 (0,10); 0,44 (0,10); p = 0,0001) e entre ADC e CG (0,51 (0,10), 0,39 (0,08), p = 0,0001). A área da parede das vias aéreas (AP/ASC-mm2) da terceira geração brônquica foi significativamente diferente entre o ADC e o GC (37,14 (9,70); 30,18 (5,06); p = 0,005) e entre ABC e GC (35, 54 (6,37); 30,18 (5,06); p = 0,005). A área da luz da via aérea da terceira geração brônquica (LA/ASC-mm2) foi significativamente diferente entre ADC e ABC (28,81 (10,08); 35,88 (7,12); p = 0,002) e entre ADC e GC (28 81 (10,08); 36,14 (7,29); p = 0,002). A atenuação máxima média (MMA-Hounsfield Units) da terceira geração brônquica foi significativamente diferente entre ADC e GC (-128,68 (67,15); -232,01 (75,20); p = 0,0001) e entre ABC e CG (-147,81 (75,31); -232,01 (75,20); p = 0,0001). Encontramos correlações negativas entre o volume expiratório forçado no primeiro segundo (VEF1) e a ERP na terceira, quarta e quinta gerações brônquicas; entre o índice Tiffeneau e a ERP nessas gerações; entre fluxo expiratório forçado (FEF25-75%) e ERP nas mesmas gerações. Encontramos correlações negativas entre VEF1 e AMMna terceira e quarta gerações e entre o índice de Tiffeneau e AMM nessas gerações. Encontramos correlações negativas entre o FEF(25-75%) e o AMM nessas gerações. Conclusões: Mesmo os asmáticos com doença controlada apresentaram evidências radiológicas de comprometimento da parede das vias aéreas; as evidências foram maiores em asma de difícil controle. Características tomográficas podem ser devido a inflamação ou remodelação. Encontramos correlações entre os parâmetros espirométricos e TCQ. Nossos achados reforçam a utilidade potencial dos parâmetros do TCQ como biomarcadores do controle da asma e da resposta ao tratamento, em pesquisa e em bases clínicas / Asthma is a chronic airway disease whose pathophysiology comprises inflammation, hyperresponsivenes and remodelling. Clinical characteristics and spirometry are used to assess disease control. Some asthmatics do not achieve control taking high doses of controller therapy (difficult to control asthma). Quantitative lung computed tomography (QCT) is seldom used in asthma but may provide asthma biomarkers. Objectives: To compare QCT findings of subjects without respiratory diseases (control group - CG), with controlled asthma (CA) and with difficult to control asthma (DCA), aiming primarily at surrogate parameters of airway remodelling. To investigate whether there are correlations between QCT and spirometry parameters. Materials and Methods: We recruited subjects with DCA and CA from a tertiary hospital. We used medical records and personal invitation to obtain CG data. All subjects underwent high resolution computed tomography and spirometry. A software (Yacta) was used to obtain QCT data. Student\'s t-test, one-way ANOVA and Fisher\'s exact test were performed to compare data from the groups. Pearson correlation coefficients were calculated to assess correlations between spirometric and QTC parameters. Results: The CG was comprised of 21 subjects; CA, of 28 and DCA, of 27. The latter had older subjects than CG and CA (50,85 (10,11); 41,27 (11,57); 42,04 (10,11) years; p=0,002). Relative airway thickness (RT) was significantly different between CG and DCA (45,31% (3,71); 49,38% (3,38); p=0,001) and between CG and CA (45,31% (3,71); 48,25 (4,51); p=0,001). Normalised airway thickness (Pi10) were significantly different between DCA and CA (0,51 (0,10); 0,44 (0,10); p=0,0001) and between DCA and CG (0,51 (0,10); 0,39 (0,08); p=0,0001). Airway wall area (AWAmm2) of the third bronchial generation was significantly different between DCA and CG (37,14 (9,70); 30,18 (5,06); p=0,005) and between CA and CG (35,54 (6,37); 30,18 (5,06); p=0,005). Airway lumen area of the third bronchial generation (ALA-mm2) was significantly different between DCA and CA (28,81 (10,08); 35,88 (7,12); p=0,002) and between DCA and CG (28,81 (10,08); 36,14 (7,29); p=0,002). Mean maximum attenuation (MMA-Hounsfield Units) of the third bronchial generation was significantly different between DCA and CG (-128,68 (67,15); -232,01 (75,20); p=0,0001) and between CA and CG (-147,81 (75,31); -232,01 (75,20); p=0,0001). We found negative correlations between forced expiratory volume on the first second (FEV1) and RT on the third, fourth and fifth bronchial generations ; between the Tiffeneau index and RT on those generations; between forced expiratory flow (FEF25-75) and RT on the same generations. We found negative correlations between FEV1 and MMA on the third and fourth generations and between the Tiffeneau index and MMA on those geneations. We found negative correlations between FEF25-75 and MMA on those generations.Conclusions: Even asthmatics with controlled disease had radiological evidence of airway wall involvement; the evidences were greater in difficult to control asthma. Tomographic features can be due to inflammation or remodelling. We found correlations between spirometric and QTC parameters. Our findings reinforce the potential usefulness of QTC parameters as biomarkers of asthma control and of response to treatment, on research and clinical grounds

The aim of this study is to investigate the functional and structural differences between normal subjects and asthmatics via image registration and computational fluid dynamics (CFD), together with pulmonary function test's (PFT) and one-image-based variables. We analyzed three populations of CT images: 50 normal, 42 non-severe asthmatic and 52 severe asthmatic subjects at total lung capacity (TLC) and functional residual capacity (FRC). A mass preserving image registration technique was employed to match CT images at TLC and FRC for assessments of regional volume change and anisotropic deformation. Instead of existing threshold-based air-trapping measure, a fraction-based air-trapping measure was proposed to account for inter-site and inter-subject variations of CT density. We also analyzed structural alterations of asthmatic airways, including bifurcation angle, hydraulic diameter, luminal area and wall area. CFD and particle tracking simulations are employed with physiologically-consistent boundary condition. As compared with normal subjects, severe asthmatics exhibit reduced air volume change (consistent with air-trapping) and more isotropic deformation in the basal lung regions, but increased air volume change associated with increased anisotropic deformation in the apical lung regions. In the multi-center study, the traditional air-trapping measure showed the significant site-variability due to the differences of scanners and coaching methods. The proposed fraction-based air-trapping measure is able to overcome the inter-site and inter-subject variations, allowing analysis of large data sets collected from multiple centers. We further demonstrate alterations of bifurcation angle, constriction, wall thickness and non-circularity at local branch level in severe asthmatics. The bifurcation angle, non-circularity and especially reduced hydraulic diameter significantly affect the increase of particle deposition in severe asthmatics. In summary, the two-image registration-based deformation provides a tool for distinguishing differences in lung mechanics among populations. The new fraction-based air-trapping measure significantly improves the association of air-trapping with the presence and severity of asthma and the correlation with forced expiratory volume in 1 second over forced vital capacity (FEV1/FVC) than existing approaches. The altered functions and structures such as air-volume change, branching angles, non-circular shapes, wall thickness and hydraulic diameters that found in asthmatics are strongly associated with the flow structures and particle depositions.

Osteoporosis is a major public health concern with origins in childhood and is potentially linked to childhood obesity. This study used novel approaches in bone imaging to characterize skeletal development in girls and to assess the influence of whole body and regional soft tissue composition on bone material, structural and geometric properties, the primary determinants of bone strength, controlling for important covariates such as maturation, diet and physical activity. Prospective analyses were conducted to assess associations between measures of total body fat (TBFM) and android fat masses (AFM) and skeletal muscle fat (SMF) content on bone mineral content, density and strength. The results showed that higher TBFM and AFM were inversely associated with changes in cortical bone sites of the femur and tibia. These findings suggest that gains in abdominal adiposity during the pre- and early- pubertal years may contribute to suboptimal bone development and skeletal fragility later in life. The analyses also showed inverse associations between baseline muscle density of the thigh and calf with 2-year changes in bone strength and bone density of the metaphyseal and diaphyseal sites of the femur and tibia. This paradoxical relationship between SMF and bone outcomes was explained by subsequent analyses showing that girls exhibiting larger gains in muscle density experienced larger increases in bone density and strength compared to girls who did not significantly increase muscle density. These findings suggest that fatty infiltration of skeletal muscle contributes to suboptimal bone development in peri-pubertal girls. Further longitudinal analyses were conducted to examine the individual effects of the muscle-bone unit components on 2-year changes in bone strength. These results showed that muscle size contributed to gains in bone strength, independent of its mechanostat effect on BMC. These results underscore the importance of muscle size for promoting bone development and bone strength during growth. A final set of analyses were conducted to examine the effects of dietary fatty acids on bone development. The results of these analyses suggest that while decreasing intakes of AA n-6 FA may benefit bone health, higher intakes n-3 FAs may benefit tibia bone density development in young girls.

Background/Objectives: Individuals with a spinal cord injury (SCI) experience reductions in lower-extremity muscle mass and increased fatty-infiltration of skeletal muscle, predisposing them to an increased risk of specific secondary health conditions. To date, few investigations have prospectively examined changes in muscle in the chronic stage of SCI. Peripheral quantitative computed tomography (pQCT) is an imaging technique capable of measuring lower-extremity skeletal muscle cross-sectional area (CSA) and muscle density, the latter is a surrogate measure of muscle fatty infiltration. The purpose of this project was to a) determine the magnitude of muscle CSA and muscle density reduction in a chronic-SCI population with diverse impairments; b) identify demographic and injury characteristics associated with muscle CSA and density status; and c) determine if muscle CSA and muscle density change over a two-year period following chronic-paralysis and if so, what factors are associated with the changes. Materials and Methods: Seventy individuals [50/20 m/f, mean (± SD) age 48.9 ± 11.5 years; duration of injury 15.5 ± 10.0 years] with chronic (>2 years post-injury) SCI (C1-T12, AIS A-D) were enrolled in a two-year cohort study. Muscle CSA and muscle density values were calculated from pQCT scans of the 66%-site of the calf obtained at baseline and two follow-up visits separated by one year. Possible correlates of muscle CSA and density selected a priori included: gender, age, height, weight, waist circumference, age at injury, level of injury, injury duration, leg spasm frequency and severity scale score (SFSS), ISNCSCI calf-muscle lower-extremity motor score (cLEMS), wheelchair use, serum vitamin D level, and physical activity level. Dependent t-tests were used to compare muscle CSA and muscle density values of participants with complete and incomplete-SCI to age, gender, and height matched able-bodied controls. Multiple linear regression models were used to determine correlates of muscle CSA and muscle density. Repeated measures analysis of variance (rANOVA) were used to examine change in muscle CSA and density over the two-year study duration and multiple linear regression models were created to determine correlates of muscle CSA and density change from baseline. Results: Individuals with motor-complete SCI had a 45% reduction in muscle CSA and a 32% reduction in muscle density relative to controls. Participants with motor-incomplete SCI had a 17% reduction in muscle CSA and a 14% reduction in muscle density relative to controls. A reduced height, waist circumference, cLEMS, and wheelchair use were associated with a smaller muscle CSA in the best-fitting regression model (R2 = 0.66; p<0.0001). In the best-fitting regression model for muscle density, increased age, a lower cLEMS, reduced SFSS, fewer minutes of daily vigorous physical activity, and wheelchair use were associated with a lower muscle density (R2= 0.37; p<0.001). A high degree of individual variability in muscle CSA change (mean ± SD: -1.9 ± 6.2cm2; range: -22.6 to 8.5 cm2) and muscle density change (mean ± SD: -1.2 ± 3.28mg/cc; range: -8.6 to 6.4 mg/cc) was observed in those with both complete and incomplete SCI over the two-year study duration. rANOVA indicated a significant reduction in both muscle CSA and density after controlling for individual variability. A greater waist circumference at baseline was weakly associated with a reduction in muscle CSA (R2 = 0.14, p<0.05), and a lower weight and waist circumference at baseline were associated with a reduction in muscle density (R2 = 0.26, p < 0.001 and R2 = 0.20, p < 0.01, respectively). Conclusion: Age, completeness of injury, spasticity, physical activity participation, and ambulation ability were identified as potential clinical predictors of muscle status in individuals with chronic-SCI. Muscle CSA and density does not reach a “steady-state” after chronic-SCI. Further investigation is needed to determine the mechanisms responsible muscle CSA and density change in order to prevent continued reductions after chronic-SCI.

No description available.

Das Auftreten pulmonaler Belüftungsstörungen nach Injektion von Xylazin beim Schaf ist in der wissenschaftlichen Literatur an Einzeltieren beschrieben. Der dabei noch ausstehende Nachweis eines postulierten Lungenödems anhand objektiver Parameter in statistisch relevanter Anzahl wurde in der hier vorliegenden Arbeit angestrebt. Weiterhin wurden ein Einfluss der wiederholten Exposition und eine Dosisabhängigkeit überprüft. Zur Bearbeitung dieser Fragen wurden 16 weibliche Merinolandschafe dreimalig in einem Abstand von 8 Wochen untersucht. Nach Prämedikation mit Midazolam (0,25 mg/kg) und Sufentanil (0,6 µg/kg) erfolgte die Allgemeinanästhesie mit Propofol (5-10 mg/kg/h). Zu den ersten beiden Versuchsabschnitten wurde Xylazin in einer Dosis von 0,15 mg/kg, im dritten Versuchsdurchgang in Höhe von 0,3 mg/kg intravenös verabreicht. Jeweils 10 Minuten vor und 5, 15, 30 Minuten nach Applikation von Xylazin wurden computertomographische Untersuchungen durchgeführt. Mit Hilfe der quantitativen computertomographischen Analyse konnte das totale Lungengewicht, der Anteil nicht belüftetes Lungengewicht und das totale Lungenvolumen ermittelt werden. Zusätzlich wurden mittels arterieller Blutgasanalysen der arterielle Sauerstoff- und Kohlenstoffdioxidpartialdruck bestimmt. In der dieser Arbeit zu Grunde liegenden Annahme nimmt im Falle eines Lungenödems das totale Lungengewicht bei konstantem Lungenvolumen zu. Eine Zunahme des totalen Lungengewichts war in allen drei Versuchsdurchgängen statitisch signifikant nachweisbar. Im Vergleich zu den Angaben in der Literatur wurden dabei jedoch keine Zunahmen in Höhe eines klinisch relevanten Lungenödems erreicht. Unerwartet konnte zusätzlich ein signifikanter Rückgang des totalen Lungenvolumens detektiert werden. Weiterhin waren bereits 5 Minuten nach Xylazininjektion bis zu einem Drittel des totalen Lungengewichts nicht belüftet. Diese pulmonalen Belüftungsstörungen nach Applikation von Xylazin beim Schaf wurden aufgrund der vorliegenden Ergebnisse nicht ausschließlich der Entstehung eines Lungenödems zugeordnet. Die detektierte Reduktion des totalen Lungenvolumens bei konstanter Beatmung kann nur durch Atelektasen begründet werden. Entsprechend dem Ausmaß der detektierten pulmonalen Reaktionen nach Xylazingabe wurden eine schwere Hypoxämie sowie eine Hyperkapnie festgestellt. Durch die mehrfache Exposition von Xylazin erfolgte der Nachweis der Wiederholbarkeit dieser Ergebnisse. Eine Dosisabhängigkeit des Ausprägungsgrades der pulmonalen Befunde hingegen konnte nicht statistisch signifikant bestätigt werden. Anhand der hier vorliegenden Ergebnisse muss die Ätiologie der pulmonalen Veränderungen nach Injektion von Xylazin beim Schaf neu durchdacht und in weiteren Studien verfolgt werden. Einflussfaktoren wie die Form der Applikation oder eine genetische Prädisposition gilt es in Zukunft zu analysieren. Neben der klinischen Anwendung von Xylazin sind die erarbeiteten Resultate relevant für humanmedizinische Fragestellungen in der Pulmologie. Dort sollte in der häufigen Verwendung des Schafes als Tiermodell in Hinblick auf mögliche Interaktionen mit den experimentellen Ergebnissen auf die Applikation von Xylazin verzichtet werden.

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that affects the feet in up to 90% of patients, and can result in bone erosions. Little is known about disease activity at the metatarsophalangeal joints (MTPJs). Magnetic resonance imaging is used to visualize erosions, but does not provide quantification. Quantitative computed tomography (QCT) allows for differentiation between bone layers and quantifies volumetric bone mineral density (vBMD). We used a peripheral QCT (pQCT) scanner in MTPJs 2-5 in RA patients to determine reliability of a pQCT protocol, and then we determined the variability in vBMD between RA patients and controls. Patients (n=25) diagnosed with RA (2010 ACR criteria) were recruited from an academic Rheumatology clinic. Controls (n=27) were also recruited and matched for sex, age and ethnicity. Baseline MR data demonstrated that 80%, 64%, 40% and 20% of patients had erosions at MTPJs 2-5, respectively. One year later, MTPJs 2-5 were scanned using pQCT (XCT 2000); 2 transaxial slices were acquired per joint. A trained pQCT operator acquired 2 scans per participant with repositioning. Test-retest, intra- and inter-rater reliability were assessed blindly for total and cortical subcortical densities (mg/cm3). Reliability was reported as root mean square coefficients of variation (%RMSCV) and RMS standard deviation (RMSSD). The mean (SD) age and disease duration were 57.8 (10.2) years and 5.0 (0.9) years, respectively. Test-retest reliability was better for MTPJs 2 and 3, than MTPJs 4 and 5. Inter- and intra-rater reliability demonstrated high reproducibility. Total and cortical subcortical vBMD appeared lower in RA patients than controls. We have reliably determined vBMD using pQCT in MTPJs 2 and 3 in RA patients. The lower vBMD in MTPJ 3 suggests that RA patients may have true erosions at this joint. This research is in the early phases, but we hope to explore the correspondence between pQCT and other RA assessment tools. / Thesis / Master of Science (MSc) / Rheumatoid arthritis (RA) affects joints in the hands and feet. The bones of these joints are affected by periarticular bone loss leading to bone erosions. Magnetic resonance imaging (MRI) and X-ray are used to visualize erosions. Since erosions are characterized by a decrease in bone mineral density (BMD) leading to holes in the bone, we tested the reliability of a peripheral quantitative computed tomography (pQCT) scanner, to measure volumetric BMD (vBMD) in 25 RA patients and compared vBMD to healthy controls. The vBMD measures appeared lower in RA patients than healthy individuals in some joints. As well, there was agreement between bone erosions detected by MRI and reduced vBMD measured by pQCT. Although we could not monitor the change over time, we are hopeful that this scanner will be able to better characterize RA disease activity, with vBMD as a surrogate marker for erosion presence.