Minimal training is required to reliably perform quantitative ultrasound of muscle

Autor: Jim S. Wu, Sarah Wilder, Basil T. Darras, Craig M. Zaidman, Seward B. Rutkove
Rok vydání: 2014
Předmět:
Zdroj: Muscle & Nerve. 50:124-128
ISSN: 0148-639X
DOI: 10.1002/mus.24117
Popis: Muscle ultrasound can be used to evaluate children with neuromuscular disorders and is a promising adjunct to the physical examination for quantitative assessment of patients with Duchenne muscular dystrophy (DMD), one of the most common, progressive, and devastating neuromuscular disorders of childhood.1 The pathology of DMD, increased amounts of intramuscular fat and fibrosis, results in increasing reflection of ultrasonic echoes that produce a brighter ultrasound image.2,3 The degree of brightness, or echogenicity, of dystrophic muscle relates to the severity and progression of the disease. In dystrophic muscle, echogenicity increases with age more in boys and young men with DMD than in the less severe Becker muscular dystrophy. In boys with DMD, the degree of echogenicity correlates with measures of strength and function and is similarly sensitive to changes in pathology over time.4,5 As ultrasound can be performed quickly and painlessly at the bedside and with minimal patient cooperation or effort, it could be used potentially to evaluate very young or very weak patients with DMD, in whom levels of strength and function are difficult to quantify. Although the amount of brightness in the ultrasound image can be evaluated using either qualitative6,7 or quantitative2,8,9 techniques, quantification of the degree of echogenicity improves reliability and sensitivity to disease10 and is appealing as a potential outcome measure in clinical trials. One quantitative method to evaluate the ultrasound image is to measure the level of the gray scale pixels in the image using commonly available image analysis software, such as Adobe Photoshop or National Institutes of Health (NIH) ImageJ.2,11 When applied to skeletal muscle, quantitative ultrasound is sensitive to the presence of neuromuscular pathologies9 and can be measured reliably between different ultrasound systems by referencing images from muscle to a common phantom.12,13 An alternative method for standardizing gray scale level (GSL) measurements between ultrasound systems has been proposed that references the GSL from muscle to subcutaneous fat14; this approach would not require use of a common phantom, but it would require that GSLs measured from fat did not vary with disease or other subject characteristics. Prior studies of quantitative muscle ultrasound have evaluated primarily images obtained by examiners with considerable ultrasound experience and training.4,8,10,14 Having skilled ultrasonographers and radiologists perform the examination and quantification, however, is problematic because it limits the applicability of the technique in the office and in multicenter clinical trials. Thus, in this study we evaluated whether inexperienced examiners could perform ultrasound imaging reliably after only a brief training session in boys with DMD and age-matched normal subjects. We also compared the reliability of image quantification between a board-certified musculoskeletal radiologist and a research assistant with only basic training.
Databáze: OpenAIRE
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