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Vibration Acoustical Equipment for Medical Diagnostic

#3432


Development of Advanced Sensor Equipment for Medical Diagnostics through the Vibration Acoustic Channel (Auscultation, Phonocardiography, Percussion, etc.)

Tech Area / Field

  • INF-SIG/Sensors and Signal Processing/Information and Communications
  • INF-OTH/Other/Information and Communications
  • INF-SOF/Software/Information and Communications

Status
3 Approved without Funding

Registration date
19.12.2005

Leading Institute
VNIIEF, Russia, N. Novgorod reg., Sarov

Supporting institutes

  • St Petersburg State Polytechnical University, Russia, St Petersburg\nRussian Academy of Sciences / Institute of Applied Physics, Russia, N. Novgorod reg., N. Novgorod

Collaborators

  • Hokkaido University / Graduate School of Engineering, Japan, Sapporo\nSungkyunkwan University / Department of Physics, Korea, Suwon\nTransnationale Universiteit Limburg / Universiteit Hasselt, Belgium, Diepenbeek

Project summary

Such a popular sound method of diagnostics as auscultation (listening to murmur) has been known even since the second century B.C. Starting with R. Laennec (1818) /Big Medical Encyclopedia, v. 7. T.: Sov. Encyclopedia, 1977, pp.532-534/, auscultation of respiratory organs has entered practical medicine as one of the most important noninvasive methods for diagnostics of respiratory organs. During auscultation of breathing bronchial and vesicular murmurs, different kinds of crepitation peculiar to various pathologies of respiratory organs are examined. Similarly, the cardiac activity may be judged from the change in heart tones and appearance of cardiac murmurs. Using the method of auscultation, the presence of stomach and intestines peristalsis may be detected, beating of the fetus heart may be listened, diastolic and systolic pressure may be measured, etc. To diagnose the cardiac activity, the method similar to auscultation is applied, which is called phonocardiogram (PCG). This method consists in graphic registration of heart tones and murmur and their diagnostic interpretation. The problem of separating respiration and heart murmurs arises almost at all times. Percussion (it also may include a vibration resonance method) differs fundamentally from the above two sound methods. According to this method, sounding of independent body parts is examined during their percussion (or applying various inducers of sound vibrations). Judging by the tone of percussion sounds (resonance response of the examined inner human organs), it is possible to determine the state and tonography of such inner organs as a liver, kidneys, etc.), which are not sound sources on their own. In the late 90s, a new method of percussion was proposed. This is a locaphony (V.D. Svet, N.S. Nikolaev et al.), which allows two-dimensional acoustic images of the inner human body pathologies to be made. The spatial accuracy of detection of pathology image in the plane is 2-3 mm (it depends on the acoustic sound vibration detector dimensions). The frequency range of the inducing acoustic signal varies within 300 Hz - 3000 Hz. Application of acoustic and vibration sensors designed for reliable and correct parameter measurement of sound waves on the outside skin surface at different human body points is common to all these methods. Clearly the sensor characteristics will be a bit different for each method (because higher quality sensors are required to measure heart murmurs). However, these differences are not great. Development of some advanced acoustic and vibration sensors for the above medical diagnostics methods will also allow their application for other types of diagnostics. For example, accelerometric registration of mechanical vibrations on the chest surface, which are caused by the cardiac output, forms the basis for the seismocardiography method (Korzeniowska-Kubacka I, et al. 2002; Koch A. Et al. 2003; Jerosch-Herold M et al. 1999). Accelerometric registration of involuntary microvibrations of various body parts, first of all, of limbs, is at the basis of various methods for studies into locomotor and neuromuscular systems. They may be conventionally called tremorography (Spiegel J, et al. 2004; Israel Z 2003, Kumar R. Et al. 2003; Navan P., et al. 2003). The methods of studies into the human neuromuscular system based on registration of the noises (acoustic emission) generated by a contractile muscle are conceptually close. These methods have come to be known as mechanomiography (MMG). They have been actively developing in the last few years (Hemmerling TM et al. 2004; Gregori B et al. 2003; Bajaj P et al 2002; Silva J et al. 2003). To record muscle surface microvibrations, miniature accelerometers made by the ICP technology are generally used here. However, these methods may be also implemented based on less sophisticated and expensive sensors. The method of studies into the human neuromuscular system called impedance mechanomiography (IMMG) is close to percussion. It is based on inducing forced (nonresonance) vibrations of the surface tissue layers and on recording mechanical impedance characteristics indicating elastic and tensile properties of these tissues (Timanin E.Ì. 1998; Timanin E.M., Eremin E.V. 2002). For recording, the impedance heads consisting of an accelerometer and a force sensor are used. This method is being studied at the IAP RAS. The technique based on the analysis of accelerograms taken from various human body parts while studying a persons gait may be used as an independent method of determining the locomotorium pathology. This technique is proposed by the SPSPU.

In the early 90s many researchers generally used the sensors at hand. They most often applied accelerometers produced by “Bruel & Kjer” and “Hewlett Packard” companies, which are primarily not meant for recording human body surface vibrations. Independently made sensors were less frequently used and the data on their design and structural features were not quoted. Therefore, the idea to unify to some extent both sensors and the recording technique itself is reasonable /Mussel M.J. The Need for Standards in Recording and Analysis Respiratory Sounds //Med. & Biol. Eng. & Comput. 1992. V.30, pp. 129-139/. This idea realization would simplify the experimental data exchange between various schools and researchers. Drawing in the development of acoustic and vibration sensors of specialists engaged in design of such sensors would promote solution of other problems such as optimization of sensor characteristics to produce minimum frequency, space and time distortions; increased signal/noise ratio; matching of the sensor specific acoustic impedance (wave resistance) with the human body wave resistance at the sensor mounting site; a multichannel character of measurements; reduced prices for sensors; settlement of the whole set of structural and technological matters, etc. Thus, to solve the set problem, it is necessary to create some high-sensitivity accelerometers, acoustic probes and/or specialized microphones. Currently, piezoelectric accelerometers and capacitor microphones (as well as acoustic probes based on them) have received the widest recognition. Piezoelectric microphones and piezoelectric pressure sensors are less popular. A number of the above advanced vibration acoustic techniques that enable early diagnosing pathologies of almost all human organs (respiratory organs, a heart, brain blood vessels, a locomotorium, etc.) require development of the vibro-acoustic equipment and methodical software. Creation of the advanced vibration acoustic equipment for medical diagnostics is impossible without solving the problem of simulation of the diagnostics process: the diagnosed organ – propagation of the vibration acoustic wave through a human body (to the skin surface) – the measurement sensor – the vibration acoustic signal analysis and diagnostics instrumentation. Based on the specific diagnostic task requirements and using simulation, it is possible to optimize parameters of vibration acoustic sensors.

The SPSPU department of biomechanics applies modern virtual simulation and prototyping technologies such as MSC.ADAMS and ANSYS program packages that in many cases make it possible to replace long-term and large-scale design stage experiments. Thanks to the possibility of presenting a wide range of kinematic links, elastic and dissipative components, loads and kinematic interactions these packages may be used to rather quickly create a fully parameterized model of a random complexity mechanism (including that having a complicated geometry of parts and their connections) by means of a handy graphic package interface or by import from other CAD systems, to specify the model component links, to apply loads and as a result of calculations to generate the data similar to that produced in the course of large-scale tests as well as a lot of additional information about operation of the item under development (critical load values at the contact points or hinges), which is suitable for processing. In particular, application of virtual simulation instruments allows creating morphologically grounded models of both inpidual biomechanical systems (models of joints, muscles and ligaments) and a human locomotorium as a whole, enables studying a desired motion of a human being, establishing interrelations in the “human being-machine” system. Thus, an extensive basis is available at the department, which may be used to develop various types of acoustic and vibration sensors as well as to construct dynamic interaction models in the “human being-sensor” system at the design stage, whereupon the pilot sensor samples may be subjected to clinical tests.

The analysis of the existing developments in the field of various acoustic and vibration sensors (including piezoelectric) made by the world leading companies such as “Bruel & Kjer” (Denmark”), “Endevco” (USA), “Kistler” (Switzerland), “ÐCB Piezotronics” (USA) and others shows that these companies have developed almost nothing for medical diagnostics. For example, “Bruel & Kjer” specialists have only developed vibration sensors (specially designed human body fit accelerometers of 4392 and 4322 type measuring parameters of the vibration affecting arms and the whole human body (machine operator, mechanic driver, pilot, etc.). The sensor of 356B40 type similar to 4322 sensor is available at “PCB Piezotronics” company. This measured vibration is a harmful production effect and it must meet the existing standards. However, these sensors are not medicine-purpose and therefore different requirements are specified to them. In the field of methodical software there are no reliable programs and techniques applicable to medical practice either.

The main project objective is to coordinate and combine the research efforts of various specialists from VNIIEF, SPSPU and IAP RAS (dynamics and instrument-making scientists, designers, computer engineers, programmers and technologists) as well as medical workers to develop advanced sensor equipment, methodical software and specific techniques for performing medical diagnostics through the vibration acoustic channel. The following probably standard set of medical sensors for vibration acoustic channel is proposed for development. They have the below tabulated approximate specifications (see the table). In the course of the project activities the possibilities for creating other sensor equipment such as impedance heads will be considered. The sensors under development will be tested in the latest medical diagnostics techniques using a vibration acoustic channel (two techniques: 1) determination of the muscular tension (through the vibration acoustic channel) in pediatrics; 2) determination of the locomotorium pathology through the vibration channel).

At the end of the project activities the plan of implementing the developed technologies in medical practice will be made.

The project participants have some publications and patents for the inventions in this field (section 12 “Supporting information”).

In the course of the project the participants are supposed to file invention applications for the new technical approaches to the sensor equipment under development.

Table

Sensor parameters

Piezoaccelerometer

Piezoaccelerometer

Intensity probe

Voltage transformation factor

200 mV/g

50 mV/g

50 mV/g

10 mV/Pa

Operating frequency range, Hz

20-1000

20-3000

20-3000

Weight, no more, g

50

50

50


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