Device for examining materials by acoustic spectroscopy

Abstract

Device (01) for examining body tissue (02) by acoustic spectroscopy, comprising an ultrasound transmitter (03) for emitting an ultrasound transmission signal (35, 36, 37, 38, 39, 40, 41), an ultrasound receiver (04) for receiving a reflected and / or transmitted ultrasound reception signal after passing through the body tissue (02) to be examined, wherein the transmitter (03) is capable of emitting multiple ultrasound transmission signals (35, 36, 37, 38, 39, 40, 41) of different frequencies f1 to f n , where n is greater than 1, and the receiving device (04) is designed to receive corresponding ultrasound receiving signals of different frequencies, characterized by that the device (01) comprises a first processing unit (10), a second processing unit (11), a signal switch (09), a storage unit (17) and an evaluation unit (25), wherein the first processing unit (10), which includes a time-to-digital converter, can determine frequency-dependent transit time values ​​(16) of the associated ultrasound signal from each transmit and receive signal pair, wherein the second processing unit (11) can determine frequency-dependent attenuation values ​​(20) of the associated ultrasound signal from each transmit and receive signal pair, wherein the signal switch (09) is arranged between the ultrasound receiving unit (04) on the one hand and the two processing units (10, 11) on the other, and wherein the received ultrasound receiving signal can be routed to both processing units (10, 11) in parallel by means of the signal switch (09). where in the storage device (17) for each of the frequencies f1 to f n the transmission time values ​​(16) and attenuation values ​​(20) determined for the various transmit and receive signals can be stored at least temporarily as a result data set (21), and wherein a qualified value for describing the examined body tissue (02) can be derived from the result data set (21) in the evaluation device (25).

Description

[0001] The invention relates to a device for examining materials by acoustic spectroscopy according to the preamble of claim 1.

[0002] US Patent 5,433,112 A discloses a device for determining the properties of molten polymer, in which ultrasonic pulses are transmitted through the molten polymer and the signal velocity and attenuation are determined. From this information, conclusions are drawn about the viscosity, composition, or structure of the polymer.

[0003] From DE 689 29 239 T2, a device for measuring the density of the os calcis is known, in which, to determine cumulative internal damage, in particular micro-fragments or micro-fractures, the relative transit times and / or relative broadband ultrasound attenuations of an ultrasound signal transmitted through the os calcis are compared with the transit times and / or broadband ultrasound attenuations of an identically shaped ultrasound signal transmitted through a material with known properties, or the absolute attenuation of the ultrasound signal transmitted through the os calcis is determined alone.

[0004] An apparatus for examining liquid or gaseous media by acoustic spectroscopy is known, for example, from DE 103 24 990 B3. This apparatus includes a transmitter for sending multiple signals of different frequencies and a receiver for receiving corresponding signals. A processing unit can then determine the phase shift of each transmitted and received signal pair and derive a value that qualifies the medium under investigation based on the phase shift. In the apparatus described therein, signal packets of different frequencies are transmitted successively in immediate succession. The frequencies preferably range between 1 and 15 MHz, with each signal packet preferably comprising at least 100 periods.For each signal packet, and thus for each frequency level, the specific received signals are captured by the receiving device and then forwarded to a processing unit. In the processing unit, the phase shift angle between each frequency-specific transmitted and received signal pair, caused by its passage through the medium under investigation, is determined. Ultimately, this frequency-specific sampling of the medium yields a multitude of different frequency-specific phase shift values, the number of which depends on the number of transmitted and received signal pairs. In this way, information about the behavior of the medium is obtained across a very large frequency range defined by individual frequency levels, and this information allows conclusions to be drawn about the properties of the medium under investigation.By sampling the medium in a frequency-specific manner and determining the corresponding frequency-related phase angles, a much more specific investigation of the medium can be achieved, since a change in the medium has a different effect on the respective frequency-specific transmit and receive signal pair.

[0005] A disadvantage of the device described in DE 103 24 990 B3 is that it relies on evaluating the phase shift values ​​caused by the transmission of the signal through the feature under investigation and documented by the received signal. This is because evaluating the phase shift between the transmitted and received signals can lead to undesirable information losses, significantly distorting the evaluation result. These information losses arise because the phase shift value is limited to a range between 0 and 360°. If the phase shift between the transmitted and received signals exceeds 360°, the method described in the publication yields a phase shift value that cannot be uniquely assigned.If the phase shift between the transmitted and received signals is, for example, 400°, the evaluation device described in the publication will deliver a phase shift value of 40°. The resulting evaluation results are therefore significantly distorted and unusable, since the evaluation yields results corresponding to a phase shift of 40° and not a phase shift of 400° (= 360° + 40°).

[0006] To solve the problem of ambiguous results when evaluating the phase shift between the transmitted and received signals, DE 198 41 154 A1 proposes generating transmitted signals with different frequencies. These different frequencies act like a vernier scale in the evaluation of the phase shifts. This makes it possible to unambiguously assign the measured phase shift values ​​to the actual phase shift between the transmitted and received signals. However, this method has the disadvantage that the sound waves are transmitted at different speeds of sound in the medium under investigation, depending on the respective transmission frequency. These varying transmission speeds can lead to significant measurement errors. The dependence of the propagation speed of the transmitted signal on the respective transmission frequency is described by the Kramers-Kronig equation.Therefore, the measurement method according to DE 198 41 154 A1 has proven to be unsuitable, since the measurement errors due to the non-uniform propagation speed of the sound waves depending on the respective transmission frequency cannot be taken into account.

[0007] The fundamentals of acoustic spectroscopy, which underlie the device according to the invention, are described, for example, but by no means exclusively, in the following textbooks: Textbook 1: Molecular Acoustics, Werner Schaaffs, Springer Verlag, 1963 (ISBN-10:3642491413, ISBN-13:978-3642491412). Textbook 2: Molecular Acoustics / Molekularakustik, K.-H. Hellwege, AM Hellwege, W. Schaaffs, Springer Verlag, 1967 (ISBN-10:3540038973, ISBN-13:978-3540038979). Textbook 3: Molecular Acoustics, AJ Matheson, John Willy & Sons Publishing, 1971 (ISBN-10:1861561857, ISBN-13:978-1861561855).

[0008] Based on this generic device, a device for the non-invasive examination of materials using acoustic spectroscopy is proposed. When examining body tissue, particularly, but by no means exclusively, for diagnostic purposes, the problem often arises that the tissue cannot be readily obtained for examination, meaning that only non-invasive examination methods can be used. For example, if examinations of the human brain are to be carried out, obtaining body tissue is, in most cases, impossible due to the significant side effects of opening the human skull.

[0009] The object of the present invention is to propose a device for the non-invasive examination of materials, in particular body tissue, by acoustic spectroscopy, in which the sources of error described above are excluded.

[0010] This problem is solved by a device according to the teaching of claim 1.

[0011] Advantageous embodiments of the invention are the subject of the dependent claims.

[0012] The device according to the invention comprises, by its generic nature, an ultrasonic transmitter for emitting ultrasonic signals and an ultrasonic receiver for receiving the reflected or transmitted ultrasonic signals. Both the transmitter and the receiver are suitable for transmitting and receiving ultrasonic signals of different frequencies, respectively.

[0013] In contrast to the teaching in DE 103 24 990 B3, the phase shift for each transmit and receive signal pair with different frequencies f1 to f1 is not taken into account during signal evaluation. n, where n is greater than 1. Instead, in a first processing unit, the frequency-dependent propagation time of the associated ultrasound signal is determined from each transmit and receive signal pair. In addition, in a second processing unit, the frequency-dependent attenuation of the associated ultrasound signal as it passes through the material under investigation is determined from each transmit and receive signal pair. In other words, this means that with the device according to the invention, the frequency-dependent attenuation of the associated ultrasound signal as it passes through the material under investigation is determined from each transmit and receive signal pair of a specific frequency f1 to f1. n As a result, a data pair consisting of the respective transit time and the respective attenuation is determined and stored in a memory device at the respective frequency f1 to f nThe data is stored. According to the invention, it is not necessary to record all data required to describe a pair of transmitted and received signals. For example, it is not necessary to know the phase of the transmitted signal, since the phase of the transmitted signal is not required for determining the propagation time and attenuation of the transmitted signal as it passes through the material under investigation. Therefore, only the data required to determine the propagation time and attenuation need to be recorded.

[0014] The device is suitable for the non-invasive examination of body tissue. In this case, the body tissue of the body part to be examined is subjected to ultrasound transmission signals, and the ultrasound reception signals are recorded after passing through the body tissue. Investigations of human body tissue during exposure to ultrasound signals, and the determination of the transit time and attenuation for each individual transmission and reception signal pair, have shown that changes in the material are significantly reflected in the resulting data pairs of transit time and attenuation. Conventional acoustic spectroscopy, in which signal attenuation is measured, is thus extended according to the invention in such a way that not only for each frequency f1 to f1, but also for each frequency f1 to f1, the transmission time and attenuation are also measured. nThe specific and frequency-dependent attenuation (ATN) is determined, as well as the specific and frequency-dependent transit time (Time of Flight, ToF). Measuring the transit time allows for the determination of the dispersivity of the material under investigation. Combining the measurements of attenuation and dispersivity enables a highly differentiated characterization of the material.

[0015] Studies of numerous subjects have shown, for example, that tissue changes in the human brain are associated with changes in the dispersive nature of the brain tissue, which can be detected using the device according to the invention. Thus, a patient's risk of stroke as a consequence of tissue changes in the brain can be recorded and quantitatively estimated. Tissue changes in the brain also occur in Alzheimer's disease and Parkinson's disease, which are associated with significant changes in transit time and attenuation when exposed to ultrasound signals and can be detected using the device according to the invention. Therefore, the device according to the invention provides a tool with which pathological changes in body tissue can be detected and quantitatively estimated using non-invasive acoustic spectroscopy.

[0016] To achieve high resolutions in measuring transit time, particularly in the range of less than 10 picoseconds, the device according to the invention comprises a time-to-digital converter (TDC). These TDCs are electronic modules capable of measuring time intervals in the range of less than 100 picoseconds and converting them into a digital output. The time measurement is based on the known transit time of an electrical signal through the modules of the TDC. The transit time is determined by how many of the electronic circuits with known transit times are traversed between the transmission of the sent signal and the reception of the input signal.This number of passes of electronic assemblies with known throughput time is then counted, whereby the measured throughput time then corresponds to the multiplication of the known throughput time of a single circuit by the number of passes.

[0017] For the correct evaluation of the result data sets, it is crucial that the transit time and attenuation values ​​are determined using the same transmit and receive signal pair. Even the slightest changes in the properties of the material under investigation, for example, due to fluctuating blood pressure in body tissue, can distort the results if attenuation and transit time are determined sequentially rather than using the same transmit and receive signal pair. To achieve this, the device according to the invention includes a signal switch that routes each received ultrasound signal identically to the first processing unit for determining the transit time and the second processing unit for determining the attenuation, allowing for parallel processing.

[0018] To enable an evaluation of the result data sets obtained by means of the device according to the invention, or the reduced result data sets derived therefrom, which yields a value qualifying the body tissue, the device includes an evaluation unit. By frequency-specific sampling of the medium and the corresponding determination of the attenuation on the one hand and the transit time on the other, a specific examination and the derivation of values ​​qualifying the material under investigation can be easily achieved, since a change in the medium has a very significant effect on the respective result data sets.

[0019] When using the device according to the invention for the non-invasive examination of materials, very large result data sets are generated, since a result data set with the respective transit time and attenuation is determined and stored for each frequency and the associated transmit and receive signal pair. If a large number of examinations are carried out and an evaluation of this data is to be carried out by comparing the result data with data from a previously established result database, processing problems can easily arise due to the large data volumes. It is therefore particularly advantageous if a reduced result data set can be derived from the determined result data set in a data reduction device, wherein the reduced result data set characteristically represents the determined result data set and has a smaller data volume.This reduction of the result data can significantly accelerate data processing during the evaluation of the result data.

[0020] The method used by the data reduction device to reduce the result data sets is essentially arbitrary. According to one approach, the maximum and minimum propagation time, as well as the maximum and minimum attenuation, are determined from a result data set containing all transmission frequencies and all transmit and receive signal pairs for the investigation of a material. These two maximum and two minimum values ​​then form a reduced result data set. This data reduction can be considered characteristic of the original data set, since the rectangular data quadrant spanned by the two maximum and two minimum values ​​encompasses all other result data.

[0021] Even greater data reduction can be achieved if the data reduction mechanism combines not just the results from a single dataset, but the results from multiple datasets. For example, if studies were conducted on a large number of individuals, the results from the datasets of all male participants and, separately, the results from the datasets of all female participants can be combined. The reduced datasets then represent the results from both the male and female participants. Similarly, datasets from different age groups can also be combined.Which classes are grouped together during result data reduction is essentially arbitrary and depends solely on the desired outcome of the investigation. To combine the result data from multiple collected datasets, the data reduction tool can determine the maximum and minimum throughput time values ​​and the maximum and minimum damping values ​​in all result datasets representing a given class. These two maximum and two minimum values ​​then define a result data space that encompasses and represents the result data from all combined result datasets.

[0022] Another possibility for data reduction is to determine at least one quantile of the throughput time values ​​in a determined result data set, as well as at least one quantile of the damping values ​​in this result data set, within the data reduction device. These quantiles are then stored as a reduced result data set. For the purposes of the invention, a quantile is understood to be a statistical threshold value within the set of throughput time values ​​or the set of damping values ​​of one or more result data sets.

[0023] For the assessment, classification and modulation during the evaluation of the result data sets or during the evaluation of the reduced result data sets, the following methods are available, for example: - Multiple Linear Regression (MLR) - Principle Component Regression (PCR) - Partial Least Square Regression (PLSR) - L-shaped Partial Least Square Regression (L-PLSR) - Support Vector Machine Regression (SVM-R)

[0024] The method used in the evaluation unit to derive the qualifying value for describing the material under investigation from the result data sets or the reduced result data sets is, in principle, arbitrary. It is particularly advantageous if this is done by means of a pattern comparison, in which the result data sets are compared with reference result data sets from a database. These reference result data sets represent measurements on reference materials with known properties. These could be body tissue from patients with known diseases, such as Alzheimer's, Parkinson's, or hypertension.

[0025] It is also conceivable that the comparative result data sets were representative of measurements taken on cell tissue with special markings in the cells.

[0026] This type of pattern comparison leads to highly differentiated test results, since the result data sets obtained with the device according to the invention provide a kind of fingerprint for each material, depending on its specific properties. The result data pairs of transit time and damping for the various frequencies form a data pattern that can characteristically describe the material under investigation and its properties. Any change in the material under investigation is accompanied by a change in this fingerprint represented by the result data set. By comparing the fingerprint represented by the result data set with the fingerprints of the comparison result data sets in the database, this pattern comparison method allows for a very differentiated statement about the material under investigation.Such pattern comparisons very often require the classification of the result data sets, for which the following methods can be used:. - Principle Component Analysis (PCA) - Partial Least Square Analysis (PLSA) - Linear Discriminant Analysis (LDA) - Support Vector Machine Classification (SVM-C) - Partial Least Square Discriminant Analysis (PLS-DA) - Soft Independent Modeling of Class Analogy (SIMCA)

[0027] In contrast to previous investigation methods, the device according to the invention determines the transit time of the ultrasound signal itself, rather than the phase shift. To determine the properties of the material under investigation with sufficient resolution, it is particularly advantageous if the transit time can be determined in the first processing unit with a resolution of at least 100 picoseconds. Preferably, the transit time should be determined with a resolution of at least 10 picoseconds.

[0028] The device according to the invention offers particularly significant advantages in examinations of the human brain, since such examinations, especially molecular or cellular studies, are otherwise either impossible or yield very limited results. Because opening the human skull to examine brain tissue is, in most cases, not feasible due to the considerable side effects, brain tissue examinations can generally only be performed using imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT). However, these imaging techniques typically do not provide differentiated diagnoses for most brain diseases.In particular, diseases such as Alzheimer's or Parkinson's can often only be detected using imaging techniques at a stage when effective treatment is no longer possible in most cases. To enable the examination of brain tissue with the device according to the invention, the ultrasound transmitter and / or receiver should be suitable for temporary and / or permanent placement on the outer surface of the patient's scalp. This placement of the ultrasound transmitter and receiver on the scalp typically does not require a physician; rather, it can be performed by appropriately trained nursing staff or even by laypersons.

[0029] The type of ultrasound waves used for the examination with the device according to the invention is, in principle, arbitrary. Longitudinal ultrasound waves in the lower MHz range are particularly suitable.

[0030] Furthermore, it is conceivable that the ultrasound transmission signals have different frequencies f1 to f n They are emitted individually one after the other or as groups one after the other by the ultrasound transmitter.

[0031] Alternatively, the ultrasound transmission signal can be used for the different frequencies f1 to f n The ultrasound signals can also be superimposed onto a common carrier signal and transmitted using the ultrasound transmitter. It is also possible for the ultrasound signals of different frequencies to be superimposed onto a common carrier signal within the ultrasound transmitter and transmitted together.

[0032] According to the invention, the transmitting device generates signals with different frequencies in order to determine a transmit and receive signal pair for each of these frequencies and to evaluate them for characterizing the material under investigation. In addition to changing the frequency, it can also be useful to transmit ultrasound signals with different amplitudes using the transmitting device. This allows for even more differentiated data analysis.

[0033] The invention will now be explained by way of example using an embodiment schematically depicted in the drawings.

[0034] It shows: Fig. 1 a device according to the invention with its various functional modules as a schematic diagram; Fig. 2. A schematic diagram to explain the operation of a first data reduction device; Fig. 3. A schematic diagram to explain the structure of a database with comparison result data sets; Fig. 4. A schematic diagram to explain the operation of an evaluation unit of the device according to Fig. 1 using a database according to Fig. 3; Fig. 5 the signal waveform and signal frequencies of an ultrasound transmission signal; Fig. 6 the signal waveform and signal frequencies of a second ultrasound transmission signal; Fig. 7 the signal waveform and signal frequencies of a third ultrasound transmission signal; Fig. 8 the signal waveform and signal frequencies of a fourth ultrasound transmission signal; Fig. 9 the signal waveform and signal frequencies of a fifth ultrasound transmission signal; Fig. 10 the signal waveform and signal frequencies of a sixth ultrasound transmission signal; Fig. 11 the signal waveform and signal frequencies of a seventh ultrasound transmission signal.

[0035] Fig. Figure 1 shows a schematic diagram illustrating the basic structure of a device 01 according to the invention, which can be used for the non-invasive examination of body tissue 02, for example a brain or skull, using acoustic spectroscopy methods. The device 01 comprises, firstly, an ultrasound transmitter 03 and, secondly, an ultrasound receiver 04. Furthermore, the device 01 comprises, for generating the ultrasound signals to be emitted by the ultrasound transmitter 03, a signal preparation module 05, a signal generator 06, and a signal amplifier 07.

[0036] After passing directly or indirectly (via reflection) through body tissue 02, the ultrasound signals are received at the ultrasound receiver 04 and amplified by a signal amplifier 08. The amplified received signals are then split in a signal splitter 09 and distributed to a first processing unit 10 and a second processing unit 11 for parallel processing. The first processing unit 10 determines the transit times required for the ultrasound signal to pass through body tissue 02 at the respective set frequency. After passing through a signal conditioning module 12, the received signal enters a time-to-digital converter 13, which measures the transit time of the ultrasound signal, i.e., the time between its emission at the ultrasound transmitter 03 and its reception at the ultrasound receiver 04.The function of the time-to-digital converter 13 is based on the fact that the transit time of an electrical signal through a multitude of electronic circuits 14 contained in the time-to-digital converter 13 is known.

[0037] To measure the transit time, the trigger signal of the ultrasound transmission signal is simultaneously routed to the time-to-digital converter 13 at the ultrasound transmitter 03 to initiate the timing process. The trigger signal of the ultrasound transmission signal then passes through the sequentially arranged circuits 14 in the time-to-digital converter 13. Each cycle of an electronic circuit 14, corresponding to a predetermined transit time, is recorded by a counter 15. As soon as the received signal is routed to the electronic circuits 14, the counter 15 switches off and multiplies the number of recorded cycles by the known transit time of each individual electronic circuit 14. This yields the total transit time 16 for a transmit and receive signal pair.For each transmission frequency, a transit time 16 results, which is stored in a storage device 17 corresponding to the respective transmission frequency.

[0038] In parallel, the signal attenuation of the ultrasound transmission signal as it passes through body tissue 02 is determined in the second processing unit 11. For this purpose, a signal processing module 18 is provided in the second processing unit 11, which processes the signal and determines the amplitude of the ultrasound reception signal. Subsequently, the amplitude of the ultrasound reception signal is compared with the amplitude of the ultrasound transmission signal in an evaluation module 19. This comparison allows the corresponding attenuation 20 to be determined for each frequency of a transmission and reception signal pair in the second processing unit 11 and stored in the storage unit 17.

[0039] During an examination of body tissue 02, a controller defines 42 predefined signal profiles with different transmission frequencies, which are then emitted by the ultrasound transmitter 03. For each individual frequency, the propagation time 16 and the attenuation value 20 are determined by evaluating the generated transmit and receive signal pair and stored in the storage device 17. At the end of the measurement process on body tissue 02, a result data set 21 is stored in the storage device 17. The result data set 21 contains the following values ​​for each of the frequencies f1 to f2: n the associated transit time 16 and the associated damping value 20, so that the result data set 21 represents a fingerprint of the material properties of the body tissue 02 determined by acoustic spectroscopy.

[0040] A data reduction device 22 is subordinate to the storage device 17, the operation of which is described below using the schematic diagram in Fig. 2 will be explained.

[0041] Fig. Figure 2 represents an example of a result data set 21, in which for each transmission frequency f1 to f n The associated transit times (ToF) and attenuation values ​​(ATN) are stored. The result data set 21 can contain a very large number of data points, for example, if the respective transit time and attenuation were determined for several hundred frequencies on a body tissue 02. To facilitate the evaluation of the result data set 21, data reduction can be performed in the data reduction unit 22 as follows. The maximum and minimum values ​​are determined from the transit time values ​​16 and the attenuation values ​​20 stored in the result data set 21. In the Fig. In the example shown, the damping value ATN3 represents the minimum damping value and the damping value ATN n-2 This represents the maximum damping value. Furthermore, the transit time value ToF2 represents the maximum transit time, and the transit time value ToF n-1 represents the minimum throughput time.

[0042] These two minimum values ​​and the two maximum values, each for transit time and damping, constitute a reduced result data set 23, which, when plotted in a coordinate system 24, is represented by a rectangle. Since the reduced result data set 23 was derived from the two minimum and two maximum values ​​of the various damping and transit time values, it can be said that the rectangle 23 representing the reduced result data set encompasses and thus represents all other data of the result data set 21 with its inner surface.

[0043] As from Fig. As can be seen in Figure 1, the data reduction unit 22 is followed by an evaluation unit 25, which interacts with a database 26 in the evaluation of the reduced result data sets 23. The database 26 stores a large number of comparative result data sets 27, which were determined by measurements on reference body parts with known properties. The operation of the evaluation unit 25 in conjunction with the database 26 will be explained below using the schematic diagrams in Figure 1. Fig. 3 and Fig. 4 will be explained in more detail.

[0044] Fig. Figure 3 first shows the database 26 with the various comparison result data sets 27. Each comparison result data set 27 was determined by an acoustic spectroscopy investigation on a comparison body part with known properties.

[0045] To enable pattern comparison of the reduced result dataset 21, which was determined during measurements on body tissue 02, with the data of the comparison datasets 27 in database 26, a data reduction is first performed for each of the comparison result datasets, as described above. Fig. 2 is explained. In other words, for each comparison result data set, a reduced result data set 28, 29, 30, 31, 32 and 33 is determined, each of which is represented by a rectangle in the coordinate system of transit time and damping.

[0046] As from Fig. As can be seen in Figure 1, a pattern comparison of the reduced result data set 23, which represents body tissue 02, is then performed in the evaluation unit 25 with the reduced comparison result data sets 28 to 30. As in Fig. As illustrated in Figure 1, the reduced result data set 23 of body tissue 02 shows the greatest similarities with the reduced comparison result data set 29. Therefore, in the evaluation unit 25, body tissue 02 can be classified as comparable in its properties to those of the reference body part represented by the reduced result data set 29. In other words, after performing the pattern comparison, the evaluation unit 25 can indicate that body tissue 02 corresponds significantly to the body tissue represented by the reduced comparison result data set 29.

[0047] Fig. Section 4 serves to explain a further variant for data reduction in the device according to the invention. This will be illustrated by way of example using the data reduction of the data in database 26 with the comparison data sets 27. As already explained above, each result data set 27 of database 26 can be mapped onto a reduced result data set, which is represented as a rectangle in the coordinate system of throughput time and damping. Now, let us further assume, by way of example, that the first three result data sets 27 in database 26 belong to patients of a specific property class, for example, patients with elevated blood pressure, and all other result data sets in database 26 belong to patients without elevated blood pressure.If an additional reduced result data set 34 is to be determined for patients in the class with elevated blood pressure, this can be done by determining the two minimum and maximum values ​​for transit time and damping from the corresponding result data sets 27 of the three result data sets representing the class. This class of patients with elevated blood pressure can then be represented by the reduced result data set 34.

[0048] Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10 to Fig. Figure 11 shows the signal waveforms 35 to 41 in the time domain, which can be used as examples of ultrasound transmission signals on device 01. The frequency of each signal waveform 35 to 41 is given in Hertz.

[0049] As in signal curve 35, the ultrasound transmission signal can each have sections with increasing frequency, whereby the frequency difference between the individual sections is equidistant.

[0050] As from Fig. As can be seen in Figure 6, the frequency difference between the individual frequency sections of the signal waveform 36 cannot be chosen to be equidistant.

[0051] As from Fig. As can be seen in Figure 7, the signal profile 37 can also be varied with regard to the amplitude of the ultrasound transmission signal, depending on the respective transmission frequency.

[0052] Fig. Figure 8 represents a signal profile 38 of the ultrasound transmission signal with an equidistantly increasing transmission frequency, whereby the duration of the individual transmission segments becomes increasingly shorter, so that a constant number of cycles are present in each segment.

[0053] As in Fig. As explained in section 9, the signal waveform 39 of the ultrasound transmission signal can also be emitted with a continuously increasing transmission frequency, for example a linear FM-modulated transmission signal.

[0054] Fig. Figure 10 represents a transmission signal profile 40 with four superimposed transmission frequencies.

[0055] The signal waveform 41 of the ultrasound transmission signal is generated by adding different transmission frequencies to a common transmission signal (superposition), whereby individual frequencies can be added or omitted in the different sections.

Claims

[1] Device (01) for examining body tissue (02) by acoustic spectroscopy, comprising an ultrasound transmitter (03) for emitting an ultrasound transmission signal (35, 36, 37, 38, 39, 40, 41), an ultrasound receiver (04) for receiving a reflected and / or transmitted ultrasound reception signal after passing through the body tissue (02) to be examined, wherein the transmitter (03) is capable of emitting multiple ultrasound transmission signals (35, 36, 37, 38, 39, 40, 41) of different frequencies f1 to f n , where n is greater than 1, and the receiving device (04) is designed to receive corresponding ultrasound receiving signals of different frequencies, characterized by , that the device (01) comprises a first processing unit (10), a second processing unit (11), a signal switch (09), a storage unit (17) and an evaluation unit (25), wherein the first processing unit (10), which includes a time-to-digital converter, can determine frequency-dependent transit time values ​​(16) of the associated ultrasound signal from each transmit and receive signal pair, wherein the second processing unit (11) can determine frequency-dependent attenuation values ​​(20) of the associated ultrasound signal from each transmit and receive signal pair, wherein the signal switch (09) is arranged between the ultrasound receiving unit (04) on the one hand and the two processing units (10, 11) on the other, and wherein the received ultrasound receiving signal can be routed to both processing units (10, 11) in parallel by means of the signal switch (09). where in the storage device (17) for each of the frequencies f1 to f n the transmission time values ​​(16) and attenuation values ​​(20) determined for the various transmit and receive signals can be stored at least temporarily as a result data set (21), and wherein a qualified value for describing the examined body tissue (02) can be derived from the result data set (21) in the evaluation device (25). [2] Device (01) according to claim 1, characterized by , that a reduced result data set (23, 34) can be derived from a result data set (21) or several result data sets (27) using a data reduction device (22) included by the device (01), wherein the reduced result data set (23, 34) characteristically represents the determined result data set (21) or the various result data sets (27) and has a smaller data volume. [3] Device (01) according to claim 2, characterized by, that in the data reduction device (22) the maximum and minimum throughput time value (16) in a determined result data set (21) as well as the maximum and minimum damping value (20) in this result data set (21) can be determined, wherein these maximum and minimum values ​​are stored as a reduced result data set (23). [4] Device (01) according to claim 2, characterized by , that in the data reduction device (22) the maximum and minimum throughput time value (16) of several determined result data sets (27), as well as the maximum and minimum damping value (20) in these result data sets (27) can be determined, wherein these maximum and minimum values ​​are stored as a reduced result data set (34). [5] Device (01) according to claim 2, characterized by, that in the data reduction device (22) at least one quantile of the throughput time values ​​(16) in a determined result data set (21) and at least one quantile of the damping values ​​(20) in this result data set (21) can be determined, wherein these quantiles are stored as a reduced result data set (23). [6] Device (01) according to any one of claims 1 to 5, characterized by , that the derivation of the qualifying value in the evaluation unit (25) is based on a pattern comparison of determined or reduced result data sets (21, 23) with comparison result data sets (27, 34) stored in a database (26), wherein the comparison result data sets (27, 34) were determined by measurement on comparison materials with known properties. [7] Device (01) according to any one of claims 1 to 6, characterized by, that in the first processing unit (10) the throughput time (16) can be determined with a resolution, in particular of at least 10 picoseconds. [8] Device (01) according to any one of claims 1 to 7, characterized by that the ultrasound transmitting device (03) and the ultrasound receiving device (04) are suitable for temporary and / or permanent placement on the outside of a patient's scalp. [9] Device (01) according to any one of claims 1 to 8, characterized by , that the ultrasound transmitting device (03) can generate longitudinal ultrasound waves in the lower MHz range. [10] Device (01) according to any one of claims 1 to 9, characterized by , that the ultrasound transmission signals (35, 36, 37, 38, 39, 40, 41) of different frequencies f1 to f n are emitted one after the other by the ultrasound transmitter (03). [11] Device (01) according to any one of claims 1 to 9, characterized by, that the ultrasound transmission signals (35, 36, 37, 38, 39, 40, 41) of different frequencies f1 to f n in the ultrasound transmitting device (03) are modulated or added to a common carrier signal and then transmitted together. [12] Device (01) according to any one of claims 1 to 9, characterized by , that the transmitting device (03) is designed to give the ultrasound transmission signals (35, 36, 37, 38, 39, 40, 41) with different amplitudes.

Images