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Preliminary Results of the Sunlight OmnisenseTM Bone Sonometer: In-vivo and In-vitro Precision and Correlation with DXA.
Quantitative ultrasound systems to date have concentrated on single site measurements using transmission mode ultrasound. A new type of quantitative ultrasound system, the OmnisenseTM, has been developed (Sunlight Ltd) which is capable of measurements at multiple sites using shortest propagation time ultrasound technology and a hand held probe. This has enabled measurements of sites previously inaccessible using ultrasound. A preliminary evaluation of the recently upgraded Omnisense was made, assessing the in-vivo and in-vitro precision and the correlation of the distal radius and the mid shaft tibia with dual x-ray absorptiometry (DXA) measurements of the lumbar spine, neck of femur and total hip. The in-vitro precision was assessed by performing daily scans on a perspex phantom. A group of 20 subjects (8 male, 12 female, age 23-55, BMI 17-40) were measured 5 times each on the same day. Measurements were taken at the distal radius and mid shaft tibia with repositioning between measurements to evaluate the intra-operator in-vivo short term precision. Finally, a group of 40 subjects of varying osteoporotic status were measured on both the Omnisense and DXA. After correction for temperature variation the in-vitro CV was 0.03%. The in-vivo root mean square CV for the distal radius was 0.54% and the mid shaft tibia 0.58%. The correlation’s between the Omnisense speed of sound (SOS) measurements and DXA bone mineral density (BMD) are shown in the table.
|SOS Radius - BMD L1-L4||0.466||0.006|
|SOS Radius - BMD NOF||0.299||0.092|
|SOS Radius - BMD Total hip||0.304||0.086|
|SOS Tibia - BMD L1-L4||0.322||0.068|
|SOS Tibia - BMD NOF||0.270||0.117|
|SOS Tibia - BMD Total hip||0.242||0.163|
|SOS Radius - SOS Tibia||0.457||0.008|
In conclusion, the in-vitro precision demonstrates an extremely stable system, with the in-vivo short-term precision results also showing good precision. Only weak to fair correlation’s with DXA were found. This may be explained by the fact that SOS is a function of both the density and the elasticity of bone.