Technical NoteReliability and Validity of Panoramic Ultrasound for Muscle Quantification
Introduction
Quantification of skeletal muscle cross-sectional area (CSA) and volume is critical for the management of sarcopenia, cachexia and limb muscle atrophy resulting from immobilization, unloading, bed rest or spaceflight. The gold standard assessments of muscle CSA and volume require sophisticated and expensive equipment such as computerized axial tomography (CT) or magnetic resonance imaging (MRI) (Trappe et al. 2009) or values are approximated using simple and less accurate anthropometric measures such as leg circumference (Yamada et al. 2010). Consequently, there is a need for other assessment techniques that are inexpensive and portable, require little training and provide reliable, precise measures of muscle CSA.
Like MRI, ultrasonography (US) makes clear distinctions between muscle and fat tissues and can, therefore, be used to produce high-quality images of muscle morphology. Not only is this measurement technique safe (no ionizing radiation) and relatively inexpensive, but it is also suitable in austere environments and could be used for serial measurements of skeletal muscle CSA if a method is developed to locate the same muscle slice in each session (Reeves et al. 2004; Arbeille et al. 2009). Recent advances in US technology and the development of panoramic scanning allow quick and automatic construction of ready-to-analyze two-dimensional (2-D) cross-sectional images of muscles. Although panoramic US appears to be a promising method to measure CSA in large muscles such as the quadriceps (Arbeille et al. 2009; Ahtiainen et al. 2010; Noorkoiv et al. 2010), its reliability and validity for volume assessments and individual quadriceps and calf muscles have not been tested. Therefore, the aims of this study were to examine the validity of panoramic US in determining quadriceps and gastrocnemius CSA and volume in comparison with MRI and to assess the reliability of using a customized template designed to guide probe position during acquisition of US images.
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Subjects
Nine healthy individuals (8 male, 1 female; age: 34.5 ± 8.2 years; body mass: 74.7 ± 10.5 kg; height: 177.1 ± 5.5 cm) with no recent history of thigh muscle injury or inflammatory disease participated. This study was approved by the Committee for the Protection of Human Subjects at Johnson Space Center and all participants provided written informed consent prior to the experiment. This investigation was conducted in accordance with the Declaration of Helsinki.
Study design
Muscle CSAs were obtained in
Results
The inter-experimenter reliability of panoramic US ranged from a CV of 2.4%–4.1% and an ICC of 0.963–0.991, whereas the inter-experimenter reliability of MRI ranged from a CV of 2.8%–3.8% and an ICC of 0.946–0.986 (Table 1). The absolute CSA difference between MRI and US ranged from 0.3 ± 1.0 cm2 to 3.3 ± 2.1 cm2 and the absolute volume difference between MRI and US ranged from 2.5 ± 12.1 cm3 to 38.0 ± 25.2 cm3 (Table 2). No significant differences were found between bed rest days for US or
Discussion
This is the first investigation to our knowledge to assess CSA and volume in individual muscle groups in the thigh and calf using panoramic US. Our results show that panoramic US images can be reliably acquired for individual muscle groups using a customized template and that there are high limits of agreement between US and MRI as analyzed using Bland-Altman plots. Although MRI produces systematically larger values than US, these differences are within 14% for RF, MG and LG.
We designed US
Conclusions
Information characterizing skeletal muscle is of fundamental importance not only for sustaining human presence in space and extending the exploration of our solar system, but also for enhancing the understanding of disuse atrophy in bedridden patients and sarcopenia in older individuals. Results from this investigation suggest that panoramic US imaging is a reliable alternative to MRI and CT that could be used to provide important information regarding muscle CSA and volume of the upper and
Acknowledgments
The authors thank the Flight Analogs Project for the excellent organization and coordination of the Integrated Resistance and Aerobic Training Study, as well as the subjects who enthusiastically participated in the study. This work was supported by the Human Research Program of the National Aeronautics and Space Administration (NASA) and a Natural Sciences and Engineering Research Council of Canada Post Doctoral Fellowship (JMS).
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