Method for checking a rotary bearing of a gantry of a computed tomography system

Abstract

The invention relates to a method for checking a rotary bearing of a gantry of a computed tomography system, wherein the gantry has a support structure and the rotary bearing with a bearing ring, wherein the bearing ring is rotatably mounted relative to the support structure about an axis of rotation, the method comprising: - a rotation of the bearing ring relative to the supporting structure around the axis of rotation, wherein at least two, in particular exactly three, structure-borne sound sensors are attached to the gantry, in particular to a surface of the gantry, - the detection of structure-borne sound values ​​using at least two structure-borne sound sensors while the bearing ring rotates around the axis of rotation relative to the supporting structure, - an evaluation of the structure-borne sound values, in particular with regard to the intensity of a structure-borne sound, whereby it is determined whether disturbance noises occur outside, in particular above, a specified disturbance noise tolerance when the bearing ring is rotated.

Description

[0001] The invention relates to a method for checking a rotary bearing of a gantry of a computed tomography system.

[0002] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0003] The following documents are considered state of the art: DE 10 2011 006 125 A1, EP 3 026 414 A1, DE 10 2023 206 492 A1 and DE 103 51 698 A1.

[0004] Third-generation computed tomography (CT) scanners comprise a gantry containing an X-ray source and an X-ray detector, typically designed to rotate around an area of ​​investigation at relatively high speed during a CT scan. Typically, rotary bearings do not always behave consistently with regard to their noise emissions during operation. When manufacturing and configuring a CT scanner, it is desirable to ensure that the CT scanner does not emit noticeable and loud noises, hereinafter referred to as background noise, during subsequent operation.

[0005] To detect the occurrence of disturbances at an early stage as part of quality assurance, the rotary bearings can, for example, be measured during assembly in the gantry by recording airborne sound during rotation.

[0006] Typically, such sound measurements can be significantly affected by ambient noise, which can considerably complicate precise measurements. For example, it is often difficult and cumbersome to avoid external noise that could influence the measurement of the rotary bearing in a production hall where other assembly work is typically taking place simultaneously.

[0007] The surveying process itself is generally very complex and requires a precise procedure, which may necessitate a certain amount of training for the personnel involved, and where errors can quickly lead to inaccurate measurements. The position of the gantry in the room and the presence of other objects can also influence the measurement result, particularly through reflections.

[0008] One approach to reducing the impact of ambient noise could be to interrupt other work in the vicinity, for example, in a production hall. Surveys could also be carried out outside of normal working hours. However, these approaches often only partially eliminate ambient noise and are generally associated with increased effort and reduced work efficiency.

[0009] It is therefore an object of the present invention to provide an improved means of detecting gantry noise, particularly at an early stage, and as reliably as possible. Furthermore, it would be desirable to enable the best possible comparability and reproducibility of noise detection.

[0010] This problem is solved by a method according to claim 1. Further advantageous aspects of the invention are considered in the dependent claims.

[0011] The invention relates to a method for checking a rotary bearing of a gantry of a computed tomography system, wherein the gantry has a support structure and the rotary bearing with a bearing ring, wherein the bearing ring is rotatably mounted relative to the support structure about an axis of rotation, the method comprising: - a rotation of the bearing ring relative to the supporting structure around the axis of rotation, wherein at least two, in particular exactly three, structure-borne sound sensors are attached to the gantry, in particular to a surface of the gantry, - the detection of structure-borne sound values ​​using at least two structure-borne sound sensors while the bearing ring rotates around the axis of rotation relative to the supporting structure, - an evaluation of the structure-borne sound values, in particular with regard to the intensity of a structure-borne sound, whereby it is determined whether disturbance noises occur outside, in particular above, a specified disturbance noise tolerance when the bearing ring is rotated.

[0012] Advantageously, the method according to the invention provides a means of detecting gantry noises caused by the rotation of the bearing ring, largely independent of the surrounding environment. By identifying these noises, the method is particularly suitable for the acoustic testing of a rotary bearing. Furthermore, it has been shown that the method according to the invention can be carried out with exceptional repeatability, thus ensuring good comparability and allowing for particularly representative evaluations. For example, noise-generating activities in the vicinity, such as assembly work on other equipment, do not necessarily have to be interrupted for this method to be used.Furthermore, it was found to be advantageous that the method according to the invention is relatively inexpensive and can be carried out with relatively little effort, compared to other measurement methods, such as acoustic intensity measurement.

[0013] In particular, the gantry may be provided with a drive and / or the rotation of the bearing ring relative to the support structure around the axis of rotation may be driven by the drive. The drive may be a drive typically used in computed tomography systems, for example, a motor.

[0014] In particular, the supporting structure may be provided with a support frame and a tilting frame, and / or the tilting frame may be mounted to tilt relative to the support frame about a tilting axis. For example, the tilting frame may have a pivot bearing and / or a bearing ring. In particular, the bearing ring may be mounted to rotate relative to the tilting frame about the pivot axis. The tilting axis may, for example, be horizontal and / or perpendicular to the pivot axis.

[0015] In particular, the bearing ring may be designed for connection to a slewing frame, specifically such that the slewing frame is rotatably mounted about the axis of rotation together with the bearing ring relative to the supporting structure, particularly relative to the tilting frame, by means of the slewing bearing when the connection between the slewing frame and the bearing ring is established. The connection between the slewing frame and the bearing ring may, for example, be essentially non-destructively detachable, in particular non-destructively detachable. For example, the slewing frame may be bolted to the bearing ring. Alternatively, the gantry may be designed to have a slewing frame, wherein the slewing frame includes the bearing ring and / or the bearing ring forms a portion of the slewing frame.

[0016] In particular, it may be provided that the rotating frame is set up to accommodate an X-ray source and / or an X-ray detector of the computed tomography system, in particular set up in such a way that the X-ray source and the X-ray detector are fixed relative to each other when the X-ray source and the X-ray detector are accommodated in the rotating frame.

[0017] In particular, the gantry may be designed to have a tunnel-shaped opening extending along the axis of rotation. The tunnel-shaped opening may be configured such that a specimen can be inserted into it along the axis of rotation for examination using the computed tomography system. Specifically, during the examination using the computed tomography system, the specimen remains stationary within the tunnel-shaped opening relative to the supporting structure, while the bearing ring rotates around the axis of rotation relative to the supporting structure, such that the X-ray source and / or the X-ray detector of the computed tomography system rotate around the specimen. The specimen may, for example, be a patient.

[0018] The term "bearing ring" is to be interpreted broadly within the scope of this invention. In particular, it may be provided that the bearing ring is a ring-shaped body and / or that the rotary bearing is a rolling bearing. It may also be provided that the bearing ring is rotatably mounted relative to the supporting structure about the axis of rotation by means of rolling elements of the rotary bearing. Particularly in the case of an unfavorable mounting of the bearing ring, noise disturbances may occur, which can be detected using this method.

[0019] The method for inspecting a rotary bearing can, in particular, be a method for inspecting a rotary bearing during the manufacturing and / or assembly of the gantry and / or the computed tomography system. For example, the method can be a method for inspecting a rotary bearing as part of a serial production and / or incoming goods inspection of the gantry components. Preferably, the X-ray detector and the X-ray source are not yet installed on the bearing ring when the method is carried out. This allows for particularly early detection of noise, even before these components are installed. It has been shown that even without an installed X-ray source and X-ray detector, subsequent noise can be detected. However, it is also conceivable, in principle, to carry out the method with an installed X-ray detector and X-ray source.Preferably, a short warm-up phase of the bearing ring is provided before the described method. Typically, a new rotary bearing initially requires a certain break-in period, after which constant sound levels can be measured. By providing a warm-up phase, measurement results can be obtained that are more representative of later operating behavior. For example, the warm-up phase can last for a few minutes, preferably 5 to 45 minutes. However, the method does not necessarily have to be limited to a warm-up phase, and in particular not to a specific warm-up phase.

[0020] The term "structure-borne sound sensor" is to be understood broadly within the scope of the invention. It generally refers to a sensor designed to detect structure-borne sound. Structure-borne sound is understood to mean, in particular, sound propagating through a solid. The term "structure-borne sound" can also refer to corresponding measured values ​​of structure-borne sound. The structure-borne sound sensor can be configured, in particular, to detect a vibration on the surface of a body and thus to detect a structure-borne sound value.

[0021] According to the invention, at least two structure-borne sound sensors are attached to the gantry, specifically to the supporting structure, for example, to the support frame and / or the tilting frame. Preferably, the structure-borne sound sensors are attached to a surface of the gantry, in particular to a surface of the supporting structure, for example, to a surface of the support frame and / or to a surface of the tilting frame. However, other connections to the gantry are also conceivable, for example, integration into the gantry, as long as structure-borne sound can be detected. Attachment to a surface is a particularly simple option.

[0022] While structure-borne sound can be measured with a single sensor, multiple sensors provide significantly better results for identifying unwanted noise. Typically, different points on the gantry exhibit varying levels of structure-borne sound, each of which can influence or correlate with subsequent unwanted noise. Generally, more sensors provide more information, leading to more precise results. However, experience has shown that even three sensors, when properly positioned (for example, through test measurements), are sufficient for highly accurate noise detection. Therefore, the need for additional sensors is often eliminated.

[0023] Preferably, the bearing ring is rotated at a speed typical for operation when measuring structure-borne sound levels. This allows for a particularly representative measurement. The structure-borne sound levels can be recorded, in particular, as a function of frequency. For example, the structure-borne sound levels can be recorded as a velocity level, especially the average velocity level. The velocity level can also be referred to as the sound velocity level. The velocity level is a logarithmic quantity derived from the sound velocity (also simply called "velocity"). For example, structure-borne sound can be recorded as an average velocity level according to DIN 45635-8 "Noise measurement on machines; airborne sound emission, structure-borne sound measurement; framework procedure" (edition 1985-06).

[0024] The intensity of structure-borne noise is to be understood broadly within the scope of this invention. In particular, it refers to a quantifiable classification of the structure-borne noise. For example, the classification can be based on the average velocity level. The classification can be based on purely physical quantities or on a quantity that takes into account human sound perception, such as a loudness level. The resulting noise is evaluated against a defined noise tolerance by determining whether noise occurs during the rotation of the bearing ring that lies outside, and especially above, the defined noise tolerance. The defined noise tolerance can be defined, for example, by a threshold value and / or a reference curve or reference value series.

[0025] According to one embodiment, the at least two structure-borne sound sensors comprise an accelerometer for detecting structure-borne sound pressure. An accelerometer can be particularly well-suited for detecting the structure-borne sound values. The at least two structure-borne sound sensors can, in particular, comprise a piezoelectric element with which the structure-borne sound is converted into an electrical signal. The piezoelectric element can be designed to convert dynamic deflections on the surface of the gantry into electrical signals. For this purpose, for example, a vibrating mass and a preload spring can be used, which transmit the deflections to the piezoelectric element.

[0026] According to one embodiment, the at least two structure-borne sound sensors are attached to the surface magnetically, by frictional connection, in particular by screw connection, and / or by material connection, in particular with an adhesive and / or with wax. For example, the structure-borne sound sensors can include a magnet for attachment to the gantry. Optionally, it can be provided that an attachment with a counter-magnet on an opposite surface of the gantry is used. Advantageously, magnetic attachment can enable particularly simple and quick, as well as precise, attachment. Wax can be advantageous in that it allows for particularly precise attachment and structure-borne sound pickup.

[0027] According to one embodiment, the evaluation includes decomposing the structure-borne sound values ​​into a frequency spectrum. In particular, the detection of unwanted noise can be carried out in a frequency-dependent manner. The method also includes assigning the values ​​directly after or during the measurement. The structure-borne sound values ​​can comprise a series of measurements of structure-borne sound values ​​that are assigned to a frequency. The frequencies can, in particular, be sound frequencies. Decomposing the values ​​into a frequency spectrum can advantageously enable a particularly good and reliable estimation of unwanted noise that occurs later. For example, the structure-borne sound values ​​can be classified in a frequency-dependent manner, taking into account human sound perception.

[0028] According to one embodiment, a velocity-level spectrum is determined. In other words, the decomposition of structure-borne sound values ​​into a frequency spectrum can include the determination of the velocity-level spectrum. The velocity-level spectrum can, in particular, be based on an average velocity level. The definition of the average velocity level is known in the prior art. In particular, the average velocity level can be determined according to a standard norm, such as DIN 45635-8. It has been shown that the use of a velocity-level spectrum, especially one based on the average velocity level, can provide particularly accurate and repeatable results for detecting disturbance noise. The structure-borne sound sensors can be designed to record a velocity-level spectrum, in particular an average velocity-level spectrum.

[0029] According to one embodiment, average velocity levels determined in the velocity level spectrum are assigned to defined frequency sections, in particular standard frequency sections. Preferably, average velocity levels determined in the velocity level spectrum are assigned to third-octave center frequencies. Third-octave center frequencies can be a particularly good way to achieve a precise gradation of the structure-borne sound values ​​and / or to break down the structure-borne sound values ​​as a function of frequency. Advantageously, each individual third-octave frequency can thus be evaluated. The structure-borne sound sensors can be designed to record a velocity level spectrum, in particular an average velocity level spectrum, in defined frequency sections, especially in third-octave center frequencies. Third-octave center frequencies can be defined in particular according to a defined standard, for example DIN EN ISO 266, "Acoustics - Standard frequencies", edition 1997-08.

[0030] According to one embodiment, determining whether noise outside the specified noise tolerance occurs during the rotation of the bearing ring is carried out by comparing the structure-borne sound values, particularly in the form of a frequency spectrum of the structure-borne sound values, with a reference curve. Preferably, a velocity-level spectrum can be compared with a reference curve. For comparing the structure-borne sound values, an average value, particularly an energy average, is calculated from the structure-borne sound values ​​of the at least two structure-borne sound sensors.

[0031] The reference curve can, for example, be created at least partially based on expert experience. It can also be created at least partially based on comparative measurements of gantries, particularly previously tested gantries. The reference curve can take into account typical deviations observed in gantries tested before and after complete assembly. Preferably, the reference curve is based at least partially on a series of measurements of a large number of recorded frequency spectra from gantries, particularly from a large number of different gantries. The reference curve need not necessarily be presented as a graphical curve. Optionally, the reference curve can be defined by its values, particularly coordinate values, and / or by a curve function. Optionally, the reference curve, together with the structure-borne sound values, can be presented to a user in an output device.The output medium can be, for example, a screen or a printed sheet.

[0032] The calibration process can, for example, include determining whether individual structure-borne sound values ​​within a sound spectrum, particularly a velocity-level spectrum, exceed the values ​​of the reference curve. For instance, a measure for exceeding individual structure-borne sound values ​​can be calculated. This exceedance can be determined as a function of frequency. In particular, the exceedance of individual structure-borne sound values ​​can be determined as a function of defined frequency bands, especially third-octave center frequencies. The measure for exceedance can be based on the difference between the exceedance and the respective value of the reference curve. For example, the difference can be a differential level. The difference, in particular the differential level, can be a measure of background noise. For example, the measure for exceedance can be defined by a relative value based on the difference between the exceedance and the respective value of the reference curve.The relative value can be, for example, a percentage value and / or a ratio value.

[0033] Determining whether noise exceeding the specified noise tolerance occurs during the rotation of the bearing ring can involve combining, and in particular adding, several measurements for exceeding multiple individual structure-borne sound values, especially all individual structure-borne sound values, to determine an overall noise level. This overall noise level can be compared to a noise tolerance threshold to classify the overall noise level. The classification can evaluate exceeding the noise threshold as exceeding the specified noise tolerance. Alternatively, the classification can evaluate falling below the noise threshold as a result that is not above the specified noise tolerance. Optionally, the classification can include further categories. For example, one of the categories could be "limit just met."

[0034] Advantageously, comparing the results to a reference curve allows for a differentiated assessment of various noise levels at different frequencies. In particular, the reference curve can be designed not as a sharp boundary, but rather as a set of all instances where it is exceeded. For example, a (minor) exceedance at a single frequency might still be acceptable if there are no other, or sufficiently few and minor, exceedances. The reference curve can be considered a curve for a typical bearing, especially a typical bearing with sufficiently low noise levels. The classification can be visually indicated in the output, for example, by a color code. This color code could, for instance, be based on a traffic light system.For example, green could indicate "good" and red could indicate that the noise level is above the specified tolerance. Optionally, yellow could indicate that the limit was just barely met. This visual indicator allows users to grasp the result more quickly, for example, without having to study and evaluate numerical values ​​in detail.

[0035] According to one embodiment, individual exceedances of the reference curve are weighted according to their influence on the overall noise level. A sum of all weighted exceedances can be compared with at least one noise threshold, comprising a noise tolerance threshold, so that the sum of all weighted exceedances is classified. Exceeding the noise threshold can be evaluated as exceeding the defined noise tolerance. Advantageously, higher proportions can thus be weighted more heavily. For example, an energetic summation of the exceedances can be provided. For example, the structure-borne sound values ​​can be logarithmic values, particularly decibel values. For example, the exceedances can be weighted such that the weighted exceedances describe a relative proportion of the total defined noise tolerance.For example, the weighted exceedances can be defined as percentages of the specified noise tolerance. However, another notation, such as an absolute level, is also possible. In this case, the specified noise tolerance could, for example, be a defined maximum level sum.

[0036] According to one embodiment, evaluating the structure-borne sound values ​​includes converting them to expected airborne sound values ​​and / or comparing them with reference values ​​from an airborne sound measurement. Advantageously, it has been shown that the structure-borne sound values ​​can be representative of airborne sound values. In particular, by comparing or converting to airborne sound values, direct information about subsequently audible airborne noise can be obtained.

[0037] According to one embodiment, the at least two structure-borne sound sensors are attached to measuring points whose positions are adapted to ensure good comparability of the structure-borne sound values ​​with the reference values ​​of the airborne sound measurement. Additionally or alternatively, the measuring points are specifically positioned so that they correspond to reference measuring points used to determine the reference curve.

[0038] At least three, and preferably exactly three, structure-borne sound sensors are preferably attached to the gantry. At least three sensors offer the advantage of providing sufficient comparability with ambient noise in the air, as has been demonstrated. Three sensors have generally proven sufficient in this regard, i.e., in all tests, provided suitable measurement positions are chosen. Furthermore, the relatively small number of sensors (only three) keeps both the installation effort and the associated costs relatively low. For example, two sensors can be placed on the back and one on the front of the gantry, or vice versa. Similarly, two sensors mounted on the same side of the gantry can be positioned on opposite sides of the ring.For example, a structure-borne sound sensor can be arranged offset by 70° to 135°, preferably 80° to 110°, particularly preferably substantially 90°, to a structure-borne sound sensor on the opposite side of the ring shape of the gantry.

[0039] Using the same measurement points as for determining the reference curve allows for particularly good comparability. It has been shown that with relatively little effort, the structure-borne sound sensors, especially at least three, can be positioned in such a way that structure-borne sound values ​​can be determined that correspond very well to the airborne sound. The exact placement may depend on the specific gantry or its type. Factors such as the material used and / or the geometric properties of the gantry can influence this. The measurement points can be determined by comparing a measured structure-borne sound spectrum with an airborne sound spectrum from the same gantry. In particular, averaged structure-borne sound values ​​from the sensors can be used for this comparison.

[0040] According to one embodiment, the structure-borne sound values ​​are evaluated according to a defined human perception of loudness and / or A-weighted. A-weighting is based on an internationally standardized frequency weighting curve. Advantageously, this allows a human perception of loudness to be taken into account.

[0041] According to one embodiment, a method for evaluating structure-borne sound values ​​as described herein, in particular below, is used to evaluate the structure-borne sound values.

[0042] This further discloses a method for evaluating structure-borne sound values ​​for checking a rotary bearing of a gantry of a computed tomography system, the method comprising: - setting up a velocity level spectrum, wherein velocity level values, in particular mean velocity level values, are each assigned to a frequency value, in particular a third-octave center frequency; - comparing the values ​​of the speed level spectrum with reference values ​​and registering any exceedances of the reference values; - a weighting of the exceedances of the reference values ​​according to their influence on overall background noise and summation of the weighted exceedances; - a comparison of the sum of all weighted exceedances with at least one noise threshold, including a noise tolerance threshold, - performing a classification of the sum of all weighted exceedances, whereby exceeding the noise tolerance threshold is evaluated as exceeding a defined noise tolerance.

[0043] All the advantages and features of the method for checking a rotary bearing can be applied analogously to the method for evaluating structure-borne sound values ​​of a rotary bearing, and vice versa. The structure-borne sound values ​​can, in particular, be velocity level values, which, for example, are recorded as frequency-dependent.

[0044] This further discloses a computer program product comprising instructions that, when executed by a computer, cause the computer to perform the steps of the method for evaluating structure-borne sound values ​​for checking a rotary bearing of a gantry of a computed tomography system. All advantages and features of the method for checking a rotary bearing and the method for evaluating structure-borne sound values ​​of a rotary bearing can be transferred analogously to the computer program product and vice versa. The computer program product can, for example, be stored on a computer-readable storage medium, in particular a non-volatile storage medium.

[0045] This document further discloses a computer-readable storage medium, in particular a non-volatile storage medium, on which the computer program product as described herein is stored. The storage medium may be, for example, a hard drive, an SSD, flash memory, an online server, etc.

[0046] All the advantages and features of the method for checking a rotary bearing, the method for evaluating structure-borne sound values ​​of a rotary bearing, and the computer program product can be transferred analogously to the computer-readable storage medium and vice versa.

[0047] All embodiments described herein can be combined with one another, unless explicitly stated otherwise.

[0048] The following examples, with features that may be helpful for understanding the invention and / or the technical problem to be solved, are explained with reference to the accompanying figures. Fig. Figure 1 shows a flowchart of a procedure for checking a rotary bearing of a gantry of a computed tomography system. Fig. Figure 2 shows a flowchart of a procedure for evaluating structure-borne sound values ​​for checking a rotary bearing of a gantry of a computed tomography system. Fig. Figure 3 shows another example of a flowchart of a procedure for checking a rotary bearing of a gantry of a computed tomography system. Fig. Figure 4 shows an example of the placement of three structure-borne sound sensors on a gantry from a front view. Fig. Figure 5 shows an example of the placement of the three structure-borne sound sensors on the [unclear text]. Fig. 4 Gantry shown from a rear view. Fig. Figure 6 shows an example of an evaluation of structure-borne sound values. Fig. Figure 7 shows another example of an evaluation of structure-borne sound values. Fig. Figure 8 shows another example of an evaluation of structure-borne sound values. Fig. Figure 9 shows another example of an evaluation of structure-borne sound values.

[0049] Fig. Figure 1 shows a flowchart of a method for checking a rotary bearing D of a gantry 1 of a computed tomography system, wherein the gantry 1 has a support structure T and the rotary bearing D with the bearing ring L, wherein the bearing ring L is rotatably mounted relative to the support structure T about a rotational axis A, the method comprising: - a rotation 110 of the bearing ring L relative to the support structure T about the axis of rotation A, wherein at least two, in particular exactly three, structure-borne sound sensors 2 are attached to the gantry 1, in particular to a surface of the gantry 1, - a recording of 120 structure-borne sound values ​​by means of at least two structure-borne sound sensors 2, while the bearing ring L rotates relative to the supporting structure T around the axis of rotation A, - an evaluation of 130 of the structure-borne sound values, in particular with regard to the intensity of a structure-borne sound, whereby it is determined whether, when rotating the bearing ring L, disturbance noises occur outside, in particular above, a specified disturbance noise tolerance.

[0050] During the evaluation, the structure-borne sound values ​​can optionally be broken down into a frequency spectrum, so that the detection of disturbance noise can preferably be carried out in a frequency-dependent manner. In particular, a velocity level spectrum 11 can be determined. Accordingly, the measurement of the structure-borne sound values ​​would already be frequency-dependent.

[0051] Fig. Figure 2 shows a flowchart of a method for evaluating structure-borne sound values ​​for checking a rotary bearing D of a gantry 1 of a computed tomography system. In a first step 231, a velocity level spectrum 11 is established. In this step, velocity level values, preferably mean velocity level values ​​14, are each assigned to a frequency value. The assignment can be performed, in particular, frequency-section by frequency, i.e., the velocity level values ​​of a defined frequency range are each assigned to a frequency value of the frequency range. The frequency value can, in particular, be a mean frequency value of the frequency range. Particularly preferably, the frequency value can be a third-octave center frequency. In a further step 232, the values ​​of the velocity level spectrum 11 are compared with reference values, and exceedances of the reference values ​​are recorded.In a further step 233, the exceedances of the reference values ​​are weighted according to their influence on the overall noise level, and the weighted exceedances 15 are summed. This weighted summation can, in particular, include an energetic addition of the exceedances. For example, relative exceedances in a loud area (e.g., high dB(A) value) can be weighted more heavily than exceedances in a quiet area (e.g., low dB(A) value). In a further step 234, the sum 16 of all weighted exceedances 15 is compared with at least one noise tolerance threshold 17. Optionally, further noise thresholds 18 can be provided. These further noise thresholds 18 can, for example, characterize different quality levels with regard to the occurrence of noise. In a further step, the sum 16 of all weighted exceedances 15 is classified.Exceeding the noise tolerance threshold of 17 is considered an exceedance of a defined noise tolerance.

[0052] Fig. Figure 3 shows another example of a flowchart for a method for checking the rotary bearing D of the gantry 1 of a computed tomography system. In step 310, the bearing ring L of the gantry 1 is rotated relative to the supporting structure T about the axis of rotation A, with at least two, preferably three, structure-borne sound sensors 2 attached to the gantry 1. In step 320, structure-borne sound values ​​of the bearing ring L are recorded by the structure-borne sound sensors 2 attached to the gantry 1 during the rotation of the bearing ring L. The structure-borne sound values ​​include velocity level values, in particular mean velocity level values ​​14, each recorded with respect to a frequency value, in particular a third-octave center frequency. In step 330, the structure-borne sound values ​​are evaluated with respect to the intensity of the structure-borne sound. The further step 330 comprises several substeps 331-335, which correspond to steps 231-235 of the procedure with respect to Fig. 2 described procedures.

[0053] The Fig. 4 and Fig. Figure 5 shows an example of the placement of three structure-borne sound sensors 2 on a gantry 1. The structure-borne sound sensors 2 are attached to fixed measuring points. The measuring points are fixed in such a way that they are adapted to the reference values ​​of the airborne sound measurement to ensure good comparability of the structure-borne sound values ​​measured by the structure-borne sound sensors 2. In addition, they correspond to reference measuring points that were used to determine a reference curve. In this embodiment, the front of the gantry 1 ( Fig. 4) A structure-borne sound sensor 2 is mounted centrally at the bottom. Two further structure-borne sound sensors 2 are arranged on the rear side, each approximately 130° offset from the structure-borne sound sensor 2 on the front. The two structure-borne sound sensors 2 on the rear side are mounted on opposite sides of the ring shape of the gantry 1 relative to each other. The exact measurement positions can be adjusted depending on the gantry 1 used in order to optimize the measurement of the structure-borne sound values.

[0054] Gantry 1 has a tunnel-shaped opening 9, the tunnel-shaped opening 9 extending along the axis of rotation A. The tunnel-shaped opening 9 is designed such that an object under investigation can be inserted into the tunnel-shaped opening 9 along the axis of rotation A for examination using the computed tomography system. In particular, it can be provided that, during the examination using the computed tomography system, the object under investigation remains stationary within the tunnel-shaped opening 9 relative to the support structure T, while the bearing ring L rotates relative to the support structure T about the axis of rotation A, so that, in particular, the X-ray source and the X-ray detector of the computed tomography system rotate around the object under investigation.

[0055] The Fig. Figures 6 to 9 each show examples of an evaluation of structure-borne sound values. The structure-borne sound values ​​are each frequency-dependent mean velocity levels 14. On the left is a list of mean velocity levels 14, each assigned to a third-octave center frequency 12. For each third-octave center frequency 12, a reference value 13 from a reference curve is also assigned. Whether noise occurs during the rotation of the bearing ring L of the gantry 1 is determined by comparing the measured mean velocity levels 14 with the reference values ​​13 of the reference curve. On the right of the table are the weighted exceedances 15, which indicate a relative noise level. The weighted exceedances 15 are given as a percentage of the noise tolerance threshold 17, which defines the maximum permissible noise level (corresponding to 100%). Below the table is the sum 16 of all weighted exceedances 15.

[0056] At 37%, this sum is 16 in Fig. 6 below the noise tolerance threshold 17 and also below another noise threshold 18, which here is a warning threshold. On the right is in the Fig. Figures 6 to 9 each show a plot of the velocity level spectrum 11 together with a reference curve (shown as a dashed line). The mean velocity levels 14 (in dB(A)) are plotted against the third-octave center frequencies 12. The measurement points are marked by circles, with solid circles indicating a exceedance of the reference curve. As in Fig. As can be seen in Figure 6, although some measurement points exceed the reference curve, the classification 19 is still positive because the sum 16 of all weighted exceedances 15 is both below the noise tolerance threshold 17 of 100% and below the further noise threshold 18 of 80%.

[0057] In Fig. 7, the classification 19 is also positive. In the case of the Fig. In fact, all measured mean velocity levels are below the reference values ​​of the reference curve, so the sum of all weighted exceedances is 0%. Fig. 8. The sum of all weighted exceedances (15) is above the further noise threshold (18) but still below the noise tolerance threshold (17). The sum of all weighted exceedances (15) is 89% here, and thus below 100%, but above 80% of the further noise threshold. Therefore, an average classification (20) is given, indicating that the specified noise tolerance is just barely met. In the example of Fig.In contrast, the noise tolerance threshold 17 is also significantly exceeded by the sum of all weighted exceedances 15. The sum of all weighted exceedances 15 is 379%, and thus exceeds 100% of the noise tolerance threshold 17.

Claims

[1] Method for checking a rotary bearing (D) of a gantry (1) of a computed tomography system, wherein the gantry (1) has a support structure (T) and the rotary bearing (D) with a bearing ring (L), wherein the bearing ring (L) is rotatably mounted relative to the support structure (T) about an axis of rotation (A), the method comprising: - a rotation (110) of the bearing ring (L) relative to the support structure (T) about the axis of rotation (A), wherein at least two structure-borne sound sensors (2) are attached to the gantry (1), wherein the at least two structure-borne sound sensors (2) are attached to the support structure (T), - a detection (120) of structure-borne sound values ​​by means of at least two structure-borne sound sensors (2) while the bearing ring (L) rotates relative to the supporting structure (T) about the axis of rotation (A), - an evaluation (130) of the structure-borne sound values, whereby it is determined whether disturbance noises outside a specified disturbance noise tolerance occur when the bearing ring (L) rotates. [2] Method according to claim 1, - where the evaluation (130) includes breaking down the structure-borne sound values ​​into a frequency spectrum. [3] Method according to claim 1 or 2, - whereby it is determined, depending on the frequency, whether disturbance noises outside the specified disturbance noise tolerance occur when rotating (110) the bearing ring (L). [4] Method according to any one of claims 1 to 3, - where a velocity level spectrum (11) is determined based on the structure-borne sound values. [5] Method according to claim 4, - where, based on the speed level spectrum (11), it is determined whether disturbance noises outside the specified disturbance noise tolerance occur during the rotation (110) of the bearing ring (L). [6] Method according to claim 5, - wherein mean speed levels (14) determined in the speed level spectrum (11) are assigned to specified frequency sections, in particular third-octave center frequencies. [7] Method according to any one of the preceding claims, - where, based on a comparison of the structure-borne sound values, in particular in the form of the velocity level spectrum (11), with a reference curve, it is determined whether disturbance noises outside the specified disturbance noise tolerance occur when the bearing ring is rotated. [8] Method according to claim 7, - where individual exceedances of the reference curve are weighted according to their influence on the overall background noise, - wherein a sum (16) of all weighted exceedances (15) is compared with at least one noise threshold, comprising a noise tolerance threshold (17), so that a classification of the sum (16) of all weighted exceedances (15) is carried out, and - where exceeding the noise threshold is considered to exceed the specified noise tolerance. [9] Method according to claim 7 or 8, - wherein the at least two structure-borne sound sensors (2) are attached to measuring points that correspond to reference measuring points used to determine the reference curve. [10] Method according to any one of the preceding claims, - where the evaluation (130) of the structure-borne sound values ​​includes a conversion of the structure-borne sound values ​​to expected airborne sound values. [11] Method according to any one of the preceding claims, - wherein the evaluation (130) of the structure-borne sound values ​​includes a comparison of the structure-borne sound values ​​with reference values ​​of an airborne sound measurement. [12] Method according to claim 11, - wherein the at least two structure-borne sound sensors (2) are attached to measuring points whose positions are adapted to ensure good comparability of the structure-borne sound values ​​with the reference values ​​of the airborne sound measurement. [13] Method according to any one of the preceding claims, - wherein at least two structure-borne sound sensors (2) are attached to a surface of the supporting structure (T).

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