Quantitative Ultrasonography

Quantitative ultrasonography (QUS) gives a global evaluation of both the cortical and the trabecular components of examined bones. QUS measurements can only be done at peripheral sites (calcaneus, fingers, tibia, etc.), and each instrument is designed to measure one specific site only. Only some instruments have been adapted for pediatric use, but still may lack the specific devices for smaller children. The main advantages of QUS in pediatrics are essentially two: absence of ionizing radiations and transportability (very important for mass screenings). However, what is exactly measured by QUS is still an open question.

QUS provides two main values: the "speed of sound" (SOS) and the "broadband ultrasonic attenuation" (BUA). While SOS is essentially determined by bone density, BUA depends on several structural parameters of the examined bone. BUA is often considered an index of the bone structure. QUS measurements appear to depend on bone size. So, changes of QUS values with age could possibly reflect bone size changes during growth, rather than actual changes in bone density. A crucial point, for example, for calcaneus-measuring instruments, is the difficulty of a precise repositioning, which might undermine reproducibility and longitudinal studies.

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