Preliminary Report

Slesinger J., Florian Z., Houfek L., Navrat T.

We have developed a new method of direct evaluation of bone elasticity and fragility.
The principle of the method is an application of vibrations of ascendent frequency
starting at 20 Hz on different sites of skeleton, eg. ulna, tibia, processus spinosus vertebrae etc.
We scan a change of vibrations in different distances from generator of vibrations.
The results are processed by spectral analysis.

We don‘t use an ultrasound vibrations.

Results of our measurement are not in a narrow correlation with BMD and/or laboratory tests.

In Brno, Czech Republic
16. September, 2008

Dr. Slesinger (e-mail: slesinger@osteologie.cz )

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Introduction
The goal of this methodology is to describe the methods of measurement and the acquisition of input data of bone quality measurement by mechanical oscillation. This methodology is based on the principle of behaviour of technical materials. It holds that the composition of material influences the signal passage through a component. The composition, the density and other properties of material may be deduced from the deformation of input signal into an output signal. In general, the same principle applies to bones. Changes of chemical composition are manifested in the bone structure and density and alter the signal passing through the bone.

Measuring Chain
The measuring chain consists of three parts. The first part is an exciter which produces the required vibrations. The shape of these vibrations can be expressed with the sine or cosine curve. Another possible function is so-called Dirack’s pulse. The goal of both the methods of excitation is to oscillate the bone in order to transmit clearly defined vibrations. In the first case, the technical solution consists in a core oscillating in the coil, under current of alternating frequency, placed on metal strips. In case of impulse excitation, there are several technical solutions, the most efficient of which seems to be an impulse hammer. From the patient’s viewpoint, the first type of excitation – sine-wave vibrations – is more convenient. This method is less stressing than impacts with a hammer, even if weak. However, from the viewpoint of dynamic effect, the impulse hammer is much more efficient as a much larger frequency spectrum is concentrated in one impulse. This feature can be achieved with a sine-wave exciter only in case of a fluent change of oscillation frequency within a certain frequency band. However, it is more time demanding than the impulse excitation and the frequency range is almost always narrower. The second part of the measuring chain is a vibration sensor. The task of this element is to read the response to the vibrations passing through the bone. These vibrations are not identical to those generated by exciter, but they are altered by passage through the bone, by its composition and structure. From the viewpoint of measured quantity it is not important which kinematic quantity is measured. Generally, position, velocity and/or acceleration may be used. From the viewpoint of technical performance it is advantageous to use acceleration sensors due to their simplicity and a great technical and shape variability. The last part is a recorder which records and stores the measured quantities. It may also include a frequency analyzer. Its advantage consists in the fact that a frequency spectrum for further analysis can be acquired immediately from the acquired quantities. High-quality recorders contain parts for adjusting the parameters of recorded quantities, i.e. recording time, data loading frequency, etc. They are also fitted with input/output filters which help maintain the measured quantities independent on input and/or output errors and meet the correct principles of reading of dynamic quantities. The measured data are stored in the form of data files which may be further processed after the measurement is finished, e.g. in PC. These data files may be either in the binary or text form.

Measurement Procedure
The measurement procedure can be described on the ulna. This procedure may be applied to any bone of sufficient access. Two points, in a sufficient distance from each other, are selected on the ulna. For example, one at the wrist and the other at the elbow. Excitation will be applied to one point, vibrations will be read at the other one. Generally, it does not matter which point is selected for excitation and which one is used for reading. The time of measurement, the number of recorded values and the frequency range of excitation are set on the recorder. The frequency range 20 – 100 Hz was tested. The recording time was 32 s and 16384 values were recorded. Thus, the resulting sampling frequency was 512 Hz. It is highly desirable for further signal processing that all the quantities are squares. The patient puts his arm loosely on a table. The exciter and the recorder are put on the selected points. To ensure the best possible contact with the bone, both the devices must be pressed strongly on the arm. Pointed extensions may be added to the exciter and the recorder to achieve a better contact. The points may be either semi-spherical or sharp. They should be sufficiently rigid to transmit vibrations well. Measuring starts as soon as the bone contact is achieved. Recorded data are either stored in the recorder for further processing, or displayed on the output device. The applied procedure has a 2 kHz frequency limit, time limit is not defined, but the patient should be taken into consideration. Great vibrations should not be selected. The entire procedure is represented in the following scheme.