QRT® 250 Heel Scanner
The QRT® 250 Heel Scanner is an ultrasound
based device designed to quantitatively assess the calcaneus (heel bone) at a location which is primarily trabecular (~90-96 percent). The calcaneus
bone mass has been measured with x-rays for years and shown to be an excellent
proxy for fracture risk. The QRT® 250 makes each radiation-free
measurement in about a second, with a reproducibility of 3.1 percent. The QRT® 250 Heel
Scanner—with its extremely low cost and excellent precision—should
allow for much wider diagnosis and detection of individuals at risk of osteoporotic
The QRT® 250 is a through-transmission system
that uses two circular single element transducers, operating at 1.5 MHz.
The system is designed to measure the calcaneus at a position that depends
on the length of the foot, and the transducers are translated to adapt to
variations in foot (and calcaneus) size (U.S.
and China Patents).
The QRT® 250 incorporates CyberLogic's Net Time
Delay (NTD) technology (U.S.,China and India
The NTD parameter has been shown to be an excellent proxy for bone mass;
see for example the papers located at our Website "A
Portable Real-Time Ultrasonic Bone Densitometer" and "Ultrasound
Simulation in Bone".
These papers describe simulation data as well as clinical data obtained with
two earlier versions of the QRT® 250.
Using CyberLogic's software package for ultrasound simulation (Wave3000™),
we have shown how the NTD technology enables the bone mass, as represented
by bone volume fraction, to be accurately estimated.
For example, the figure below shows a 3D micro-CT image of
a core of a calcaneus.
Thirty (30) such images served in a study of ultrasound propagation
using 3D simulations (Wave3000, CyberLogic, Inc.). The simulated
received waveforms were processed to obtain the NTD associated with each
calcaneal image, and plotted versus the BMD. The BMD was computed directly
from the 3D micro-CT image, using an assumed constant tissue density (of
1.85 g.cm-3). As may be seen, there is excellent correspondence between the
NTD and BMD in this simulation study (this data has an R-squared value of
A clinical study was also carried out with an early handheld
version of the QRT® 250. Briefly, eighty-five (85) female
adult subjects were ultrasonically interrogated and also measured with dual-energy
x-ray absorptiometry (GE/Lunar PIXI bone densitometer) at the heel (below).
A linear multivariate regression (using age and NTD as independent
variables) was used to determine an estimate of bone mass at the heel. The
relationship between the ultrasound-based estimate of heel BMD and actual
(DXA-determined) BMD is shown below, and demonstrates a linear correlation
of 0.88 (P<0.001).
This correlation is higher than presently FDA-approved ultrasound bone assessment
devices, which have a correlation under R=0.8.
QRT® 250 Heel Scanner is an investigational device. Limited
by US Federal law to investigational use.