ABSTRACT
Introduction Ultrasound biomicroscopy (UBM) is a technique for generating high-resolution images, with frequencies from 20 MHz to 100 MHz. For example, it has been used in animal research related to models of injury and diseases that mimic human conditions. With a three-dimensional ultrasound (3D) image system, an organ can be viewed at various angles and the volume estimated, contributing to an accurate diagnosis. This work refers to the generation of 3D-UBM images, employing a 35 MHz ultrasound system, from multiple two-dimensional (2D) images. Phantoms were used to validate the technique and to determine its reliability of volume measurements. Additionally, the technique was used to obtain 3D images of the rat gastrocnemius muscle. Methods Four different phantoms were used and ten acquisition sequences of 2D-images acquired for each one. Thereafter, 5 volume segmentations were performed for each acquisition sequence, resulting in 50 measured volumes for each phantom. The physical volumes of all phantoms were used to validate the technique based on the coefficient of variation (CV) and the intraclass correlation coefficient (ICC). Images of the gastrocnemius muscle were acquired and the partial volume quantified. Results The CV and ICC confirmed the reliability of volume measurements obtained by segmentation. Moreover, cross-sectional 2D images of rat hindlimb were obtained, allowing to identify the gastrocnemius muscle and to partially quantify the muscle volume from 3D images. Conclusion The results indicated that the technique is valid to generate 3D images and quantify the volume of a muscle compatible with the dimensions of a small animal.
ABSTRACT
Há, atualmente, na literatura, poucas pesquisas de confiabilidade e validação da quantificação de parâmetros de arquitetura muscular por ultrassonografia (US), relatando informações importantes como o erro típico da medida (ETM) e o coeficiente de correlação intraclasse (ICC). O objetivo do estudo foi aplicar a técnica de US para quantificar as medidas de comprimento da fibra (CF) e ângulo de penação (AP) dos músculos gastrocnêmios e determinar a confiabilidade e a reprodutibilidade dessas medidas. Duas imagens de cada gastrocnêmio de 19 indivíduos jovens e saudáveis foram adquiridas com um equipamento de ultrassom modo-B (7,5MHz), em duas visitas. CF e AP foram medidos cinco vezes nas duas imagens de cada indivíduo, totalizando vinte medidas de cada parâmetro para cada participante. A confiabilidade do total das 760 medidas foi determinada através do coeficiente de variação (CV), ICC e ETM. O CV do CF variou de 1,67 a 4,44 por cento e do AP de 3,8 a 11,62 por cento. Todos os ICC se encontram no intervalo de grande confiabilidade, com exceção do valor referente à medida interdias do AP do gastrocnêmio medial (0,67). Os dois valores mais altos de ETM (3,1º e 3,7º) correspondem aos dois valores inferiores do ICC (0,67 e 0,83), referentes às medidas repetidas interdias dos gastrocnêmios. As medidas de CF dos gastrocnêmios medial e lateral apresentaram ETM de 2,17mm e 2,25mm, respectivamente. Os resultados obtidos demonstraram que a metodologia utilizada para medição de CF e AP realizada em imagens de ultrassom apresentou alta confiabilidade.
There are few studies in the literature concerning the reliability and validity of the quantification of muscle architecture parameters using ultrasound that also report important information such as typical error of measurement (TEM) and intraclass correlation coefficient (ICC). The aim of this study was to use ultrasound imaging to quantify fiber length (FL) and pennation angle (PA) of the gastrocnemius muscle and to determine the reliability and reproducibility of these measurements. Two images of each gastrocnemius of 19 young healthy subjects were acquired using ultrasound equipment (7.5 MHz), in two visits. FL and PA were measured five times on each image, for a total of twenty measurements of each parameter. The overall reliability of the 760 measurements was determined through coefficients of variation (CV), ICC and TEM. The CV of FL ranged from 1.67 to 4.44 percent and from 3.8 to 11.62 percent for the PA. All ICC were within the high reliability range, with the exception of the between-visits PA value of the medial gastrocnemius (0.67). The two highest TEM values (3.1º and 3.7º) correspond to the two lowest ICC values (0.67 and 0.83), referring to repeated between-visit measurements of the medial and lateral gastrocnemius. FL measurements of the medial and lateral gastrocnemius had a TEM of 2.17 and 2.25 respectively. The results showed that ultrasound-based measurement of FL and PA exhibits high reliability.