Cm. Langton et M. Subhan, Computer and experimental simulation of a cortical end-plate phase cancellation artefact in the measurement of BUA at the calcaneus, PHYSL MEAS, 22(3), 2001, pp. 581-587
Citations number
6
Categorie Soggetti
Research/Laboratory Medicine & Medical Tecnology",Physiology
It has been experimentally demonstrated that for the measurement of broadba
nd ultrasound attenuation (BUA) at the human calcaneus the cortical end-pla
te creates a measurement artefact of the order of 7 dB MHz(-1). It has been
suggested that the origin of this artefact may be a phase cancellation of
the ultrasound pulse resulting from inconsistencies in propagation time acr
oss the ultrasound beam.
Experimental and computer simulations were performed on samples of varying
degrees of curvature and hence varying propagation times across the ultraso
und beam. The experimental simulation incorporated Perspex samples of 35, 5
0 and 75 mm radius. The computer simulation was implemented using Matlab an
d Simulink, with the propagation time represented by a transport delay. The
wavelet-based simulation incorporated a digitized transmitted ultrasound p
ulse derived from the experimental simulation.
The experimental and computer-derived frequency spectra for the varying rad
ii samples were comparable, demonstrating, firstly, that there is a signifi
cant dependence of measured BUA upon radius of curvature and, secondly, tha
t the response in measured BUA to radius of curvature is similar in magnitu
de and trend for both experimental and computer simulations. The current st
udy suggests that the BUA artefact observed in vitro corresponds to a radiu
s of approximately 58 mm. Although the radius of curvature was not recorded
in the original in vitro study, this value appears to be reasonable.
This study indicates that the assumptions within the computer simulation we
re manifested within the experimental validation, and, hence, the observed
BUA measurement artefact is related to the presence of the calcaneal cortic
al end-plate and is due to phase cancellation of the propagating ultrasound
pulse.