ABSTRACT
INTRODUCTION: No longitudinal data on the normal development of muscle thickness (MT), quantitative muscle ultrasound echo intensity (EI), and muscle force (MF) in healthy children are yet available. METHODS: Reference values of MT, EI, and MF of 4 muscles from infancy to age 16 years were established during a 4-year follow-up period and correlated with age and growth. RESULTS: For most muscles, MT and MF correlated with growth and aging, with almost equal influences of weight and height. EI increased only slightly (1% per year) with height, weight, and age. CONCLUSIONS: To use these reference values for repeated measurements, MF and MT can be corrected for either weight or height. It does not seem necessary to correct EI for these factors during follow-up of a few years. These results provide a basis for more precise detection of changes in muscle structure or force in neuromuscular disorders.
Subject(s)
Muscle Development/physiology , Muscle Strength/physiology , Muscle, Skeletal/physiology , Adolescent , Body Height , Body Weight , Child , Child Development/physiology , Child, Preschool , Female , Follow-Up Studies , Humans , Infant , Male , Muscle, Skeletal/diagnostic imaging , Reference Values , UltrasonographyABSTRACT
Muscle ultrasound is a useful technique to detect neuromuscular disorders. Quantification of muscle echo intensity (EI) using gray-scale analysis is more reliable and more sensitive compared with visual evaluation of the images. We devised a method to reliably use EI normal values established with one ultrasound device for use with another device. Based on measurements in a dedicated phantom and in 7 healthy subjects, a conversion equation was calculated to convert the mean EI. The reliability of this equation was next evaluated in a follow-up study of 22 healthy children. Mean muscle EI could be reliably converted from one ultrasound device to another. This allows for normal values obtained with one device to be used with other devices, which is an important step forward toward the use of quantitative muscle ultrasound in daily clinical care.
Subject(s)
Image Processing, Computer-Assisted/methods , Muscle, Skeletal/diagnostic imaging , Muscular Diseases/diagnostic imaging , Ultrasonography/methods , Adolescent , Animals , Child , Child, Preschool , Humans , Infant , Muscle, Skeletal/anatomy & histology , Muscle, Skeletal/physiology , Nonlinear Dynamics , Signal Processing, Computer-Assisted , Sound , Sus scrofaABSTRACT
In this study, we compared the sensitivity and specificity of visual versus quantitative evaluation of skeletal muscle ultrasound in children suspected of having a neuromuscular disorder (NMD). Ultrasonography (US) scans of four muscles (biceps brachii, forearm flexors, quadriceps femoris, anterior tibial muscle) were made in 76 children. All images were visually evaluated using the Heckmatt criteria and quantitatively evaluated with computer-assisted grey-scale analysis of muscle echo intensity. Visual evaluation could achieve a sensitivity up to 71%, with a specificity of 92%. With quantification, a sensitivity of 87% accompanied by a specificity of 67% was found, but other diagnostic values could be achieved, depending on the cut-off point. Quantification resulted in a higher interobserver agreement (kappa 0.86) compared with visual evaluation (kappa 0.53). We conclude that quantification of echo intensity is a more objective and accurate method. Because it can achieve higher sensitivities, it is better-suited for the screening task in the diagnostic phase of children with a NMD.
