Agreement between dual x-ray absorptiometers using pencil beam and fan beam: indicators of bone health and whole-body plus appendicular tissue composition in adult athletes

SUMMARY OBJECTIVE: The current study was aimed to examine intra-individual variation on indicators of bone health in addition to whole-body plus appendicular tissue measurements using two concurrent assessments based on pencil beam and fan beam dual energy X-ray absorptiometry (DXA) systems in adult athletes from several sports. METHOD: Thirty-two male participants (27.6±10.1 years) were measured on anthropometry including multifrequency bioelectric impedance and air-displacement plethysmography. Bone mineral content (BMC), bone area, fat and lean soft tissue were derived using pencil beam (Lunar DPX-MD+) and fan beam (Lunar iDXA) absorptiometry. Bone mineral density (BMD) was obtained for the femoral neck, trochanter and triangle of ward. Finally, the right thigh was defined as a region of interest (ROI). Analyses comprised intra-class correlation (ICC), Effect size (d) from mean differences of repeated measurements, coefficient of variation (CV) RESULTS: ICC were >0.900 for all measurements. Intra-individual differences were large for BMC (d=1,312; CV=2,7%), bone area (d=1,761; CV=2,7%), fat tissue (d=1,612; CV=11%) and all indicators of appendicular lean soft tissue (d=1,237-1687; CV=2,0-4,1%). A very large difference (d=4,014; CV=8.4%) was diagnosed for lean soft tissue of the ROI. CONCLUSION: Although differences among concurrent instruments for BMC and bone area, the effect size of mean differences was negligible for BMD. Fat and lean soft tissue derived from DXA should be interpreted as reference values (not criterion) due to equipment-related variation, more apparently in the ROI values.

RESUMO OBJETIVO: O presente estudo examinou a concordância entre os indicadores de saúde óssea e composição tecidual resultantes da aplicação de equipamentos concorrentes de absorciometria de raios X de dupla energia (DXA). MÉTODO: A amostra (n = 32), com 27,6 ± 10,1 anos de idade avaliados antropometricamente, inclui impedância bioelétrica com multifrequência e pletismografia de ar deslocado. O conteúdo mineral ósseo (CMO), a área de tecido ósseo, o tecido magro e o tecido gordo de corpo inteiro foram obtidos considerando o modo pencil beam (Lunar DPX-MD+) e o fan beam (Lunar iDXA). Para cada um dos equipamentos, foi efetuado um scanner proximal do fêmur, sendo produzida informação sobre a densidade mineral óssea (DMO) do colo, nomeadamente triângulo de Ward, trocanter e haste. Na fase de processamento, foi definida uma região de interesse (ROI; coxa direita). As análises compreenderam a diferença de médias de medidas repetidas com cálculo da magnitude de efeitos (d), coeficiente de correlação intraclasse (CCI), coeficiente de variação (CV). RESULTADOS: Foram obtidos CCI>0,900 para todas as medidas, com diferenças intraindividuais largas apenas para CMO (d = 1,312; CV = 2,7%), área de tecido ósseo (d = 1,761; CV = 2,7%), tecido gordo total (d = 1,612; CV = 11%) e tecido magro em todos os segmentos (d = 1,237-1,687; CV = 2,0-41%). A massa magra da ROI apresentou uma variaçāo intraindividual muito larga (d = 4,014; CV = 8,4%). CONCLUSÃO: Foram encontradas diferenças negligenciáveis para a DMO de corpo todo. As medidas de massa gorda e massa magra obtidas por DXA nāo devem ser tidas como critério, mas antes como referenda, muito especialmente quando se delimita uma ROI.

The role of moderate-to-vigorous physical activity in mediating the relationship between central adiposity and immunometabolic profile in postmenopausal women

ABSTRACT Objectives To analyze the role of moderate-to-vigorous physical activity (MVPA) in mediating the relationship between central adiposity and immune and metabolic profile in postmenopausal women. Materials and methods Cross-sectional study comprising 49 postmenopausal women (aged 59.26 ± 8.32 years) without regular physical exercise practice. Body composition was measured by dual-energy X-ray absorptiometry. Fasting blood samples were collected for assessment of nonesterified fatty acids, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), adiponectin, insulin and estimation of insulin resistance (HOMA-IR). Physical activity level was assessed with an accelerometer (Actigraph GTX3x) and reported as a percentage of time spent in sedentary behavior and MVPA. All analyses were performed using the software SPSS 17.0, with a significance level set at 5%. Results Sedentary women had a positive relationship between trunk fat and IL-6 (rho = 0.471; p = 0.020), and trunk fat and HOMA-IR (rho = 0.418; p = 0.042). Adiponectin and fat mass (%) were only positively correlated in physically active women (rho = 0.441; p = 0.027). Physically active women with normal trunk fat values presented a 14.7% lower chance of having increased HOMA-IR levels (β [95%CI] = 0.147 [0.027; 0.811]). Conclusions The practice of sufficient levels of MVPA was a protective factor against immunometabolic disorders in postmenopausal women.

Tipos de atividades físicas e densidade mineral óssea em adultos aparentemente saudáveis / Types of physical activity and bone mineral density in apparently healthy adults

Introdução: O tipo de atividade física (AF) pode influenciar a relação entre esta e a densidade mineral óssea (DMO). Desta forma, o objetivo do presente estudo é avaliar a relação entre diferentes tipos de AF e DMO em adultos. Método: Estudo transversal realizado com amostra de conveniência (n=208 indivíduos de 20 a 59 anos) de Pelotas, RS. A DMO (g/cm2) foi avaliada por absorciometria de raios-X de dupla energia (DXA) e a prática de caminhada e AF de intensidades moderada e vigorosa no lazer foram avaliadas por meio da respectiva seção da versão longa do Questionário Internacional de Atividade Física (IPAQ). A associação entre a DMO e os diferentes tipos de AF foi avaliada por regressão linear. Resultados: Em torno de 67% dos participantes atendiam à recomendação de ≥150 min/sem de AF. Não houve diferença estatisticamente significativa nas medidas da DMO entre indivíduos com maior ou menor tempo semanal em prática de caminhada, AF de intensidade moderada e vigorosa, isoladamente. Porém, foi observado um aumento, com margem inferior do intervalo de confiança no limite da significância, na DMO de indivíduos do segundo tercil de tempo gasto em AF total ­ 160-300 min/sem (ß=0,025 IC95%=0,001; 0,049), quando comparados ao grupo menos ativo. Conclusão: O estudo não encontrou associação entre DMO e a prática de caminhada e AF de intensidade moderada e vigorosa, podendo haver uma relação com o total acumulado de AF por semana, entre indivíduos que atendem à recomendação de AF, mas não são altamente ativos.(AU)

Introduction: Type of physical activity (PA) can influence the relationship between it and bone mineral density (BMD). Thus, the aim of the current study is evaluate the relationship between different types of PA and BMD in adults. Methods: Cross-sectional study using a convenience sample (n=208 individuals from 20 to 59 years old) in Pelotas, RS. BMD (g/cm2) was measured by dual energy X-ray absorptiometry (DXA) and time spent in walking and moderate and vigorous PA during the leisure-time was evaluated by the International Physical Activity Questionnaire in the long version. Association between BMD and types of PA was evaluated by linear regression analyses. Results: About 67% out of the subjects reached the recommendation of ≥150 min/week of PA during the leisure-time. There was no statistically significant difference in the BMD among individuals with higher or lower weekly time spent in walking, moderate or vigorous PA. However, a slightly difference was observed in BMD from subjects in the second tertile of time spent in any activity ­ 160-300 min/week (ß=0.025 IC95%=0.001; 0.049), in comparison to individuals in the first tertile of PA. Conclusion: There was no statistical association of walking, moderate and vigorous PA alone with BMD. It is possible a relationship between the total amount weekly spent in any PA in individuals who reached the PA recommendation but were not highly active.(AU)

Capacidade preditiva de diferentes equipamentos de bioimpedância elétrica, com e sem preparo prévio, na avaliação de adolescentes / Predictive capacity of different bioelectrical impedance analysis devices, with and without protocol, in evaluation of adolescents

OBJETIVO: determinar a capacidade preditiva de quatro equipamentos distintos de bioimpedância elétrica (BIA) na avaliação de adolescentes, com e sem a realização de protocolo. MÉTODOS: estudo transversal realizado com 215 adolescentes de 10 a 14 anos, de ambos os sexos, avaliados através da antropometria e da composição corporal pelo DEXA e por quatro equipamentos distintos de BIA, com e sem protocolo. Foram utilizados os testes estatísticos: Kolmogorov-Smirnov, do Qui-quadrado, t-Student ou Mann-Whitney, Kruskal-Wallis, Wilcoxon e Índice Kappa. Foram construídas curvas ROC e calculados os valores de sensibilidade, especificidade e preditivos positivo e negativo. RESULTADOS: dos adolescentes, 44,2% apresentaram excesso de gordura corporal. A BIA tetrapolar, equipada com oito eletrodos táteis, demonstrou-se mais sensível e com resultados mais próximos ao DEXA (AUC = 0,964 com protocolo e AUC = 0,973 sem protocolo, p < 0,001), apresentando, também, maior concordância (k = 0,67 com protocolo, e k = 0,63 sem protocolo, p < 0,001). A avaliação sem protocolo foi semelhante ao DEXA na maioria das situações investigadas (p > 0,05). CONCLUSÃO: a BIA é um instrumento capaz de predizer distrofias relacionadas à gordura corporal de adolescentes. Na impossibilidade de realização do protocolo, seus resultados podem ser úteis em estudos populacionais.

OBJECTIVE: this study was performed to determine the predictive capacity of four different bioelectrical impedance analysis (BIA) devices in the assessment of adolescents, with and without a protocol. METHODS: a cross-sectional study was performed with 215 adolescents aged 10 to 14 years, of both genders, evaluated through anthropometry and body composition by dual energy X-ray absorptiometry (DXA) and by four different BIA devices, with and without a protocol. The following tests were used: Kolmogorov-Smirnov's, chi-squared, Student's t or Mann-Whitney's, Kruskal-Wallis's, Wilcoxon's, and kappa index. The ROC curves were constructed and the sensitivity, specificity, and positive and negative predictive values were calculated. RESULTS: of the 215 adolescents, 44.2% had excessive body fat. The tetrapolar BIA device equipped with eight tactile electrodes showed more sensitivity and results that were closer to those obtained by DXA (area under the ROC curve [AUC] = 0.964 with protocol and AUC = 0.973 without protocol, p < 0.001), as well as greater agreement (k = 0.67 with protocol and k = 0.63 without protocol, p < 0.001). The evaluation without protocol was similar to that by DXA in most investigated situations (p > 0.05). CONCLUSION: BIA is capable of predicting alterations in adolescents' body composition. When it is impossible to perform the assessment with a protocol, its results may be useful in population studies.

Construction of a copper stepwedge with aluminum equivalent mean gray values

OBJECTIVES: To produce a copper (Cu) stepwedge with aluminum (Al) equivalent mean gray values (MGV). MATERIAL AND METHODS: The thicknesses of Cu steps that were equivalent to those of the Al were formulated using the X-ray attenuation properties of the materials. The Al and fabricated Cu stepwedges were radiographed, but the MGVs of the Cu stepwedge were mismatching to those of the Al. Using a mathematical function to adjust the pixel MGV of Cu stepwedge to those of the Al, new Cu stepwedges were created. In vitro iterations were performed until best approximation to Al was reached. RESULTS: The MGV of the Cu stepwedges fabricated by formularization were different than those of Al (p=0.001). Iteration method led to MGV similar to those of the Al stepwedge (p=0.207). CONCLUSIONS: Construction of a Cu stepwedge according to the basic rules of radiophysic failed to result in a stepwedge with similar radiodensity values to those of Al stepwedge. Further studies may use the formularization method only for prototype Cu wedge production, but consecutive iterations shall be compassed to obtain the best approximation to Al MGV.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

OBJECTIVE: To investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography. MATERIALS AND METHODS: For 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using kappa statistics and assessing the area under the receiver operating characteristic curve (AUC). RESULTS: Vocal cord delineation scores by DES (mean, 4.2 +/- 0.4) were significantly higher than those by conventional imaging (mean, 3.3 +/- 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (kappa = 0.60, AUC = 0.909) to that by conventional technique (kappa = 0.18, AUC = 0.852) (p = 0.038). CONCLUSION: Dual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

A modified formula for defining tissue phantom ratio of photon beams.

Tissue phantom ratio (TPR), for square fields of various dimensions has been determined at varying depths in water. The dose in water has been measured at a fixed source-to-surface distance (SSD) of 100 cm and reference depth of 5 cm for 6 MV photon beam of Siemens Linear Accelerator Primus 11 in German Cancer Research Center (DKFZ), Heidelberg, Germany. A modified formula has been developed to calculate the TPR value for isocentric treatment. The present article describes the conversion of the measured data values into a comprehensive and consistent data set by the modified formula, that gives the TPR from Percentage Depth Dose (PDD) with depth as a function of field sizes from 10 mm x 10 mm upto 300 mm x 300 mm) and depth (from 0 mm to 300 mm).

Avaliaçäo da soluçäo Kodak RP X-OMAT quando utilizada na processadora T4, da DUPONT, quanto às densidades ótica e radiográfica, analisadas pelo fotodensitômetro MRA e pelo sistema digital Digora / Evaluation of Kodak RP X-OMAT solution when utilized in the DUPONT T-4 processor to optical and radiographic densities, analysed by MRA photodensitometer and by Digora digital system

O presente trabalho teve o objetivo de analisar a utilizaçäo das Densidade Radiográfica (DR), e Densidades Radiográfica invertidas (DRi), como substituto das Densidades Oticas (DO). As diferentes medidas foram executadas a partir da utilizaçäo de tiras de filmes extra-bucais XK-1, que foram expostas no sensitômetro MRA com 0,5 segundo. As tiras foram processadas em soluçöes processadoras RP X-OMAT da Kodak, na processadora automática DU PONT T-4, nas temperaturas de 27ºC, 29ºC, 31ºC e 34ºC. Para se avaliar a DO utilizou-se o fotodensitômetro MRA e para a avaliaçäo das Densidades Radiográficas escaneou-se as tiras de filmes com o escaner Scanjet da HP 4C/T e utilizou-se o software Digora for Windows 1.51 que forneceu os dados que puderam ser comparados para avaliaçäo da soluçäo de processamento radiográfico quanto a atividade, uso e degradaçäo da mesma em diferentes processamentos. Os resultados mostraram que a DO teve maior número de processamentos superiores a média nas temperaturas de 31ºC e 34ºC, mostrando que os processamentos foram mais eficientes. A avaliaçäo da DR e DRi revelou que em todas as temperaturas os processamentos apresentaram um equilíbrio de resultados e que foram menos discrepantes na variaçäo dos resultados...

Comparaçäo das densidades ópticas e radiográficas analisadas pelo fotodensitômetro M.R.A. e pelo software Adobe Photoshop 4.0 dos filmes Kodak TMS-1 processados na soluçäo Kodak RP X-OMAT, a diferentes temperaturas na processadora CRONEX T4 / Comparation of optical and radiographic densities analised by photodensitometer M.R.A. and by Adobe Photoshop 4.0 software of films KODAK TMS-1 processed in the solution RP X-OMAT of Kodak, at different temperatures in the processor CRONEX T4

Este trabalho teve o objetivo de analisar a utilizaçäo das Densidades Radiográfica (D.R) e Radiográfica invertida (D.Ri), obtidas pelo uso do "software"de imagem Adobe Photoshop 4.0, para substituir a Densidade Óptica (D.O) na avaliaçäo dos filmes e soluçöes de processamento. Utilizamos tiras de filmes extrabucais TMS-1 que após serem expostas no sensitômetro MRA por 0,5 segundo, foram processadas na soluçäo RP X-OMAT da Kodak na processadora automática CRONEX T4 da DU PONT, nas temperaturas de 27ºC, 29ºC, 31ºC e 34ºC. Utilizamos o fotodensitômetro M R A para avaliar a Densidade Óptica (D.O). Para analisar a Densidade Rdaiográfica (D.R) e Densidade Radiográfica invertida (D.Ri), as tiras de filmes foram escaneadas (Scanjet HP 4C/T), e utilizamos o "software" Adobe Photoshop 4.0, para a obtençäo dos resultados (D.R e D.Ri). Esses dados serviram para avaliar a soluçäo de processamento radiográfica, quanto a sua atividade, degradaçäo e uso em diferentes temperaturas. A análise dos resultados demonstrou que os processamentos foram mais eficientes nas temperaturas de 31º e 34ºC. Em relaçäo à Densidade Óptica quando comparada à Densidade Radiográfica e Densidade Radiográfica invertida, observamos que estas demonstraram maior equilíbrio e resultados menos discrepantes. A análise estatística dos resultados obtidos pela correlaçäo de Pearson, demonstrou em relaçäo à Densidade Óptica, alta correlaçäo em todas as temperaturas avaliadas e uma correlaçäo ainda maior nas temperaturas de 31ºC e 34ºC quando comparamos com a Densidade Radiográfica e Densidade Radiográfica invertida...

Control de calidad de la densitometría ósea: precisión reproductibilidad y aplicación clínica / Quality control of bone densitometry: accuracy, precision and clinical application

Dual energy x-ray absorptiometry (DEXA) is one of the most widely used methods for bone mineral density (BMD), total body mass (TBM), total body fat (TBF), percentage of total body ft (TBF) and total body fat-free mass (TBFFM) measurements. We investigated the in vitro and vivo accuracy and precision of DEXA in repeated measurements of a lumbar espine phantom and in 30 healthy volunteers. Based on precision, the minimal significant variability (MSV) at 95 por ciento confidence level between 2 measurement of the same object or subject was calculated. In vitro accuracy and MSV were 99.8 and 0.9 por ciento respectively. In vivo indexes were 99.4 and 0.9 percent for whole-body BMD. 98.6 and 2 percent for lumbar spine BMD, 96.6 and 4.8 percent for femoral neck BMD, 98 and 2.8 percent for major trochanter BMD, 96 and 5,7 percent for Ward's triangle BMD, 99.5 and 0.7 percent for TBM, 98 and 2.9 percent for TBF, 97.9 and 3 percent for TBF and 99 and 1.4 percent for TBFFM. Our fIndings indicate that DEXA is a very reliable instrument and in order to be 95 percent confident of a real change between 2 scans a difference of at least the calculated MSV must be measured