Intelligent ultrasonic bone tissue surgery device

Abstract

This invention discloses an intelligent tissue identification ultrasonic bone surgery device, belonging to the field of medical device technology. The intelligent tissue identification ultrasonic bone surgery device includes an energy host, an ultrasonic handpiece, a tissue identification unit, a host control unit, and a pulse protection unit. This invention solves the problems of existing ultrasonic bone surgery devices lacking a real-time, objective tissue identification mechanism during bone cutting, relying on the surgeon's touch or visual judgment, which easily leads to iatrogenic injury, and the insufficient accuracy and poor anti-interference ability of single resistance parameter identification. This invention achieves high-precision automatic identification of hard and soft tissues through dual-parameter impedance vector analysis, and can immediately interrupt the ultrasonic energy output when soft tissue is detected, thereby ensuring surgical safety. Simultaneously, through the intermittent drive modulation of the pulse protection unit, the temperature rise of the surgical area during bone cutting is effectively controlled, further reducing the risk of thermal damage to surrounding normal tissues.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to an ultrasonic bone tissue surgical device for intelligent tissue assessment. Background Technology

[0002] Ultrasonic bone surgery equipment utilizes high-frequency electrical energy to drive a transducer to generate mechanical vibrations. Through the cutting, grinding, and emulsifying effects of the scalpel tip, it achieves precise processing of bone tissue. Due to its advantages such as minimal damage to surrounding soft tissues, less bleeding, and a clear surgical field, it is widely used in delicate surgeries such as neurosurgery, spinal surgery, otolaryngology, and hepatobiliary surgery. However, existing ultrasonic bone surgery equipment still faces the following technical challenges in practical clinical applications: During bone cutting, the scalpel tip may accidentally come into contact with soft tissue structures such as nerves, blood vessels, or muscles. Existing equipment largely relies on the surgeon's touch or visual judgment to distinguish between hard and soft tissues, lacking a real-time, objective tissue type identification mechanism. Improper operation can easily cause iatrogenic injury. Some solutions attempt to identify tissue through impedance changes, but these often use single resistance parameter analysis, resulting in insufficient accuracy and anti-interference capabilities for identifying different tissue interfaces. Therefore, they do not meet current needs. To address these issues, we propose an intelligent tissue identification ultrasonic bone surgery device. Summary of the Invention

[0003] The purpose of this invention is to provide an ultrasonic bone tissue surgical device for intelligent tissue identification. By extracting the resistance and capacitance components in the high-frequency electrical signal of the scalpel tip in real time, and comparing the two parameters with the preset hard / soft tissue impedance threshold range, the device automatically identifies the tissue type. This automatically controls the output and interruption of the ultrasonic drive signal, thus solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an ultrasonic bone tissue surgical device for intelligent tissue assessment, comprising: The power unit is equipped with a first ultrasound drive channel (US1) and a second ultrasound drive channel (US2), and is configured to respond to channel switching commands during surgical operations to drive the corresponding first ultrasound handpiece and second ultrasound handpiece respectively. The tissue recognition unit, integrated inside the energy host, is configured to acquire, in real time, the high-frequency electrical signal flowing through the scalpel tip attached to the ultrasonic handpiece currently in operation in bone tissue cutting mode, and extract the resistance and capacitance components in the high-frequency electrical signal. The host control unit, integrated in the energy host, is connected to the tissue identification unit and the first and second ultrasonic drive channels. It is configured to have preset hard tissue impedance threshold ranges and soft tissue impedance threshold ranges. The resistance component and capacitance component are compared with the hard tissue impedance threshold ranges and soft tissue impedance threshold ranges, respectively. When the resistance component and capacitance component fall into the hard tissue impedance threshold range, it is determined that the scalpel tip is in contact with hard tissue and the corresponding ultrasonic drive channel is controlled to output a continuous ultrasonic drive signal. When the resistance component and capacitance component fall into the soft tissue impedance threshold range, it is determined that the scalpel tip is in contact with soft tissue and the corresponding ultrasonic drive channel is controlled to interrupt the output of the ultrasonic drive signal. The pulse protection unit, integrated in the energy host, is configured to modulate the continuous ultrasonic drive signal into an intermittent pulse drive signal according to the externally selected protection level when the host control unit determines that the scalpel tip is in contact with hard tissue and controls the corresponding ultrasonic drive channel to output a continuous ultrasonic drive signal, thereby reducing the temperature of the surgical area.

[0005] Furthermore, the tissue identification unit includes: An electrical signal acquisition module is configured to acquire a high-frequency current signal flowing through the tip of the scalpel and a high-frequency voltage signal applied to the tip of the scalpel; The impedance analysis module is configured to extract the phase difference information between the high-frequency current signal and the high-frequency voltage signal, and perform vector impedance calculation based on the amplitude of the two signals and the phase difference to separate the resistance component and the capacitance component.

[0006] Furthermore, the tissue identification unit is also configured as follows: In the unloaded state where the ultrasonic handpiece is activated and the scalpel tip has not yet contacted the target tissue, the open circuit impedance value of the scalpel tip in the air medium is obtained and used as a reference value. Before determining the tissue type, the real-time extracted resistance and capacitance components are normalized using the reference value, and the normalized results are compared with the preset hard tissue impedance threshold range and soft tissue impedance threshold range.

[0007] Furthermore, the host control unit has a built-in dual-channel collaborative scheduling logic, specifically: When the first ultrasonic driving channel is activated and the tissue recognition unit determines the type of tissue contacted by the scalpel tip, the second ultrasonic driving channel is placed in the tissue sensing and holding state. In the tissue sensing and holding state, the second ultrasonic drive channel maintains a detection voltage with an amplitude lower than the soft tissue cutting threshold between itself and the corresponding scalpel tip. The tissue identification unit pre-judges the contact state of the scalpel tip based on the electrical parameters in the detection voltage circuit. When the pre-judge result is contact with hard tissue, the host control unit generates a channel ready flag. After receiving the channel switching command, the host control unit controls the second ultrasound drive channel to switch from the tissue sensing and holding state to the energy output state according to the channel ready flag.

[0008] Furthermore, the host control unit executes transition state identification logic, specifically as follows: The host control unit continuously acquires the resistance and capacitance components extracted by the tissue identification unit within a preset time window, and calculates the slope of the change of the resistance and capacitance components within the preset time window. The change slope is compared with a preset set of slope thresholds, which includes critical slope values ​​of tissue interfaces that characterize tissue type changes. When the host control unit determines that the current values ​​of the resistance component and the capacitance component exceed the hard tissue impedance threshold range and the change slope reaches the critical slope value of the tissue interface, it is determined that the scalpel tip is in the edge state of transition from hard tissue to soft tissue. In the edge state, the host control unit controls the corresponding ultrasonic drive channel to smoothly reduce the output continuous ultrasonic drive signal to below the soft tissue safety threshold.

[0009] Furthermore, the host control unit embeds safety interlock logic, specifically as follows: The effectiveness of the resistance and capacitance components extracted in real time by the tissue identification unit is verified. When the resistance and capacitance components exceed the impedance boundary range of normal biological tissue, it is determined that the electrode contact is abnormal. The host control unit then interrupts the corresponding ultrasound drive channel and puts the ultrasound drive channel into an idle lock state.

[0010] Furthermore, the pulse protection unit has multiple preset protection levels, each corresponding to a set of preset pulse modulation parameters, which include the pulse period and duty cycle, specifically: Based on the externally selected protection level, the pulse period and duty cycle corresponding to the protection level are extracted, and the continuous ultrasonic drive signal is turned off during a portion of the pulse period, with the pulse period as the interval, to form the intermittent pulse drive signal. The duty cycle is the ratio of the effective output period of the intermittent pulse drive signal to the entire pulse cycle.

[0011] Furthermore, while outputting the intermittent pulse drive signal, the pulse protection unit continuously receives the resistance and capacitance components from the tissue identification unit, and determines the exit judgment time window based on the duty cycle set for the current protection level. The exit judgment time window is determined according to the following relationship: in, The duration of the exit judgment time window; The pulse cycle set for the current protection level; The duty cycle set for the current protection level, and ; The safety margin factor is an integer greater than or equal to 1. When the resistive and capacitive components are continuously and stably within the soft tissue impedance threshold range within the exit judgment time window, the host control unit controls the pulse protection unit to terminate the output of the intermittent pulse drive signal.

[0012] Furthermore, the host control unit executes the scalpel tip trajectory mapping and danger zone warning logic, specifically as follows: Acquire the patient's preoperative CT, MRI and 3D digital subtraction angiography data, and fuse the CT, MRI and 3D digital subtraction angiography image data into a unified coordinate system through rigid registration and elastic registration; A pre-trained 3D U-Net deep learning model was used to automatically segment the fused images and reconstruct bone tissue, nerve bundles, vascular plexus, dura mater, brain tissue and tumor boundaries. Mark the hazardous areas and construct a three-dimensional structural model of the hazardous areas, then import the three-dimensional structural model into the positioning coordinate system; Real-time multi-source positioning data is collected by a miniature electromagnetic sensor installed on the tip of a scalpel. Extended Kalman filtering is used to fuse the multi-source positioning data and output the scalpel tip pose sequence. The blade tip pose sequence is imported into the positioning coordinate system and aligned with the patient's preoperative image space using a spatial registration algorithm. The blade tip pose sequence is stored in chronological order to form a trajectory point column. The blade tip orientation vector at each trajectory point in the trajectory point column is determined. The blade tip cutting direction is determined based on the blade tip orientation vector. The blade tip motion state trajectory parameters and blade tip cutting state trajectory parameters are determined according to the blade tip cutting direction. Determine the statistical trajectory points corresponding to the cutting state trajectory parameters of the blade tip, and calculate the shortest Euclidean distance between each statistical trajectory point and the surface of each danger zone. The current cutting safety status is determined based on the shortest Euclidean distance. The host control unit automatically reduces the ultrasonic drive signal power to the preset safety power based on the current cutting safety status and the comparison between the shortest Euclidean distance and the preset safety distance, and highlights the target danger area. The deviation between the actual cutting range and the pre-planned path during surgery is calculated based on the parameters of the blade tip's motion trajectory and cutting trajectory. When the target deviation exceeds the preset deviation value, a direction correction prompt will be issued; When the scalpel tip is determined to have entered a dangerous area and the tissue identification unit identifies it as soft tissue, the ultrasonic drive signal is automatically interrupted and the device is locked, forcing the surgeon to perform an emergency retraction operation.

[0013] Furthermore, the tissue identification unit can also determine hard tissue from soft tissue in the following ways: Obtain the maximum index value, mean index value, and standard deviation of the resistance and capacitance components respectively, and calculate the fusion score based on the index values ​​using a preset weighted fusion scoring function: in, This is represented as a fusion score. This is represented as a resistance adaptive calculation weight. This is represented as the maximum index value corresponding to the resistance component. Represented as the average value of the index corresponding to the resistance component. This is expressed as the standard deviation of the index corresponding to the resistance component. This is represented as a capacitor adaptive weight calculation. This is represented as the maximum index value corresponding to the capacitance component. This is represented by the average value of the index corresponding to the capacitance component. This is expressed as the standard deviation of the index corresponding to the capacitance component; The fusion score is mapped to an organization type probability using a preset logical function: in, This represents the probability of organization type, and e represents the natural constant with a value of 2.72. This is expressed as the mapping sensitivity coefficient. This is expressed as a decision bias. When P is greater than the preset probability, it is determined to be soft tissue; when 1-P is greater than the preset probability, it is determined to be hard tissue.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention overcomes the subjective defects of existing technologies that rely on the surgeon's touch or visual judgment by simultaneously extracting the resistance and capacitance components from high-frequency electrical signals and comparing them with preset hard / soft tissue impedance threshold ranges. Compared with single resistance parameter analysis, the tissue identification mechanism based on resistance-capacitance dual dimensions significantly improves the identification accuracy and anti-interference ability of different tissue interfaces, thereby effectively reducing the risk of iatrogenic damage caused by accidental cutting of soft tissues such as nerves and blood vessels during surgery. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the module of the ultrasonic bone tissue surgical device for intelligent tissue judgment according to the present invention. Figure 2 This is a flowchart illustrating the execution process of the ultrasonic bone tissue surgical device for intelligent tissue judgment according to the present invention. Figure 3 This is a schematic diagram of the structure of the ultrasonic bone tissue surgical device for intelligent tissue judgment according to the present invention.

[0016] In the diagram: 1. Energy source; 2. First ultrasonic handpiece; 3. Second ultrasonic handpiece; 4. Control foot pedal. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] To address the shortcomings of existing ultrasonic bone surgery equipment, such as the lack of a real-time, objective tissue discrimination mechanism during bone cutting, reliance on surgeon's touch or visual judgment which can easily lead to iatrogenic injury, and the insufficient accuracy and poor anti-interference capability of single resistance parameter identification, please refer to [the relevant documentation / reference]. Figures 1-3 This embodiment provides the following technical solution: An intelligent tissue assessment ultrasound bone tissue surgical device, comprising: The energy host 1 is equipped with a first ultrasound drive channel (US1) and a second ultrasound drive channel (US2). At the same time, the energy host 1 is connected to an ultrasound handle and a control foot pedal 4 via lines. The ultrasound handles are a first ultrasound handle 2 and a second ultrasound handle 3. The energy host 1 responds to the channel switching command during the surgical operation and drives the corresponding first ultrasound handle 2 and second ultrasound handle 3 respectively. The tissue recognition unit, integrated inside the energy host 1, is configured to acquire, in real time, the high-frequency electrical signal flowing through the scalpel tip attached to the ultrasonic handpiece currently in operation in bone tissue cutting mode, and extract the resistance and capacitance components in the high-frequency electrical signal. The host control unit, integrated in the energy host 1, is connected to the tissue identification unit and the first and second ultrasonic drive channels. It is configured to preset hard tissue impedance threshold range and soft tissue impedance threshold range. The resistance component and capacitance component are compared with the hard tissue impedance threshold range and soft tissue impedance threshold range, respectively. When the resistance component and capacitance component fall into the hard tissue impedance threshold range, it is determined that the scalpel tip is in contact with hard tissue and the corresponding ultrasonic drive channel is controlled to output a continuous ultrasonic drive signal. When the resistance component and capacitance component fall into the soft tissue impedance threshold range, it is determined that the scalpel tip is in contact with soft tissue and the corresponding ultrasonic drive channel is controlled to interrupt the output of the ultrasonic drive signal. The pulse protection unit, integrated in the energy host 1, is connected to the main control unit and the ultrasonic drive channel. It is configured to modulate the continuous ultrasonic drive signal into an intermittent pulse drive signal according to the externally selected protection level when the host control unit determines that the scalpel tip is in contact with hard tissue and controls the corresponding ultrasonic drive channel to output a continuous ultrasonic drive signal, thereby reducing the temperature of the surgical area.

[0019] As a further extension of the configuration of the ultrasonic handle and scalpel tip, at least two ultrasonic handles are provided, with different resonant frequencies, namely a first ultrasonic handle 2 and a second ultrasonic handle 3. For example, the first ultrasonic handle 2 is a straight skull cutting handle with a resonant frequency of 40kHz, and its scalpel tip is configured to remove hard tissue with ultrasonic impact effect as the main mechanism. The second ultrasonic handle 3 is a curved suction handle with a resonant frequency of 25kHz, and its scalpel tip is configured to emulsify and suction soft tissue with ultrasonic cavitation effect as the main mechanism. Each ultrasonic handpiece is equipped with a universal interface for detachably mounting various surgical blade tips. The energy host 1 automatically matches the drive signal parameters output to the ultrasonic handpiece to the preset parameter range corresponding to the surgical blade tip by identifying the electrical characteristic parameters of the surgical blade tip mounted on the ultrasonic handpiece. By adopting an operation that allows selection of a suitable blade tip according to the surgery, it can meet the stringent requirements of complex neurosurgery, spinal and ENT surgery, hepatobiliary surgery, etc., and is suitable for a variety of applications.

[0020] As a further optimization of the control method, this ultrasonic bone tissue surgery device provides both wireless and wired control foot pedals 4 for surgeons to choose from according to their usage habits. Among them, the wireless control foot pedal 4 provides a more flexible user experience, allowing surgeons to easily switch the power level and perfusion flow rate of the ultrasonic drive by stepping on it, reducing the constraints of cables in the surgical area. The wired control foot pedal 4 serves as a basic control component, also enabling precise control of power and flow rate. It is highly reliable and has a direct response. The configuration of the two foot pedals allows the ultrasonic bone tissue surgery device to adapt to different operating room layouts and surgeons' operating preferences.

[0021] The technical effects of the above-mentioned technical solution are as follows: The energy host 1, by configuring first and second ultrasonic drive channels, can drive handles with different resonant frequencies in response to channel switching commands. For example, the straight-head bone cutting handle and the curved suction handle are optimized for bone cutting and soft tissue emulsification suction, respectively. The dual-channel design meets various surgical needs. The tissue recognition unit extracts the resistance and capacitance components from the high-frequency electrical signal at the scalpel tip in real time during cutting mode, using dual-parameter analysis to replace traditional single-resistance judgment, thereby improving the identification accuracy and anti-interference capability of different tissue interfaces. The host control unit compares the extracted resistance and capacitance components with preset hard and soft tissue impedance threshold ranges. When both... When all parameters fall within the hard tissue region, a continuous ultrasonic drive signal is automatically output; when they fall within the soft tissue region, the output is immediately interrupted. This achieves objective, real-time tissue identification and automatic response without relying on the surgeon's touch or visual judgment, thus avoiding accidental injury to nerves, blood vessels, and other soft tissues. In the continuous drive state in hard tissue, the pulse protection unit can modulate the continuous signal into an intermittent pulse drive signal according to the externally selected protection level, thereby reducing the temperature of the surgical area and preventing thermal damage. In addition, the universal handle interface, in conjunction with the energy host 1, automatically identifies and matches the electrical characteristic parameters of the scalpel tip, enabling the ultrasonic bone tissue surgery device to be compatible with various scalpel tip types and expanding its clinical applicability.

[0022] Organizational identification unit, including: The electrical signal acquisition module is configured to acquire the high-frequency current signal flowing through the tip of the scalpel and the high-frequency voltage signal applied to the tip of the scalpel, and to perform pre-filtering and programmable gain amplification on the high-frequency current signal and the high-frequency voltage signal to eliminate common-mode interference in the electrosurgical environment. The impedance analysis module is configured to extract the phase difference information between the high-frequency current signal and the high-frequency voltage signal, and perform vector impedance calculation based on the amplitude of the two signals and the phase difference to separate the resistance component and the capacitance component. Furthermore, the impedance analysis module is equipped with a temperature compensation mechanism, which collects the temperature parameters inside the handle in real time and dynamically compensates the calculated resistance component and capacitance component according to the preset temperature-impedance drift curve, and outputs the compensated resistance component and capacitance component as the final tissue discrimination basis.

[0023] The technical effects of the above solution are as follows: By synchronously acquiring the high-frequency current signal flowing through the scalpel tip and the high-frequency voltage signal applied to it through the electrical signal acquisition module, complete amplitude and phase raw data can be provided for impedance calculation. Through the pre-filtering and programmable gain amplification processing of the electrical signal acquisition module, common-mode noise interference in the high-frequency electrosurgical environment is effectively suppressed, thereby improving the signal-to-noise ratio and dynamic range of the raw signal, thus ensuring the signal quality of subsequent impedance analysis. On this basis, the impedance analysis module extracts the phase difference information between the two signals and performs vector impedance calculation in combination with the amplitude, accurately separating the composite impedance into resistance and capacitance components. The dual-parameter joint characterization of tissue electrical properties can more comprehensively reflect the essential differences in conductivity and dielectric properties between hard and soft tissues compared with single resistance parameter analysis, thereby effectively improving the identification accuracy and anti-interference ability of different tissue interfaces. The introduction of the temperature compensation mechanism can dynamically correct the temperature drift error of resistance and capacitance components according to the real-time temperature of the handle, ensuring that the tissue identification criteria remain stable and reliable during long-term and high-power surgical operations, avoiding tissue misjudgment caused by temperature changes.

[0024] The organization identification unit is also configured as follows: In the unloaded state where the ultrasonic handpiece is activated and the scalpel tip has not yet contacted the target tissue, the open circuit impedance value of the scalpel tip in the air medium is obtained, and the fluctuation amplitude of the open circuit impedance value is monitored within a preset series of sampling cycles. When the fluctuation amplitude is less than the preset stability threshold, the open circuit impedance value is locked as the reference value. Before determining the tissue type, the real-time extracted resistance and capacitance components are normalized using the reference value, and the normalized result is compared with the preset hard tissue impedance threshold range and soft tissue impedance threshold range. If the fluctuation of the open-circuit impedance value exceeds the preset stability threshold during the no-load self-calibration process, the tissue identification unit will generate a calibration anomaly prompt and prohibit entry into the tissue discrimination process until a valid reference value is obtained.

[0025] The technical effects of the above solution are as follows: By monitoring the fluctuation range of the open-circuit impedance value under no-load conditions and locking the reference value only when the signal is stable, the tissue identification unit can eliminate the reference value acquisition deviation caused by signal oscillation at the moment of handle start-up or environmental parasitic parameter drift, thereby ensuring the accuracy and consistency of the normalized reference. The normalization processing method converts the resistance and capacitance components into the rate of change relative to the reference value, which can automatically offset the fixed offset introduced by factors such as individual differences of the scalpel tip, cable parasitic parameters, and electrode surface aging. This makes the tissue impedance characteristic criterion highly universal, so there is no need to set a threshold for each scalpel tip separately. At the same time, when the fluctuation exceeds the limit, a calibration anomaly prompt is generated and the tissue identification process is blocked, which can eliminate the risk of tissue misjudgment caused by invalid reference values, thereby improving the reliability of the entire device's intelligent identification.

[0026] The host control unit has a built-in dual-channel collaborative scheduling logic, specifically: When the first ultrasonic driving channel is activated and the tissue recognition unit determines the type of tissue contacted by the scalpel tip, the second ultrasonic driving channel is placed in the tissue sensing and holding state. In the tissue sensing and holding state, the second ultrasonic drive channel maintains a detection voltage with an amplitude lower than the soft tissue cutting threshold between itself and the corresponding scalpel tip. The tissue identification unit pre-judges the contact state of the scalpel tip based on the electrical parameters in the detection voltage circuit. When the pre-judge result is contact with hard tissue, the host control unit generates a channel ready flag. After receiving the channel switching command, the host control unit controls the second ultrasound drive channel to switch from the tissue sensing and holding state to the energy output state according to the channel ready flag.

[0027] The technical effects of the above solution are as follows: Through dual-channel collaborative scheduling logic, the second ultrasound drive channel is in a tissue sensing and holding state when the main channel is working. It continuously monitors the contact state of the scalpel tip using a detection voltage lower than the soft tissue cutting threshold. Without damaging the soft tissue, it can pre-determine whether it has contacted the hard tissue and generate a channel ready flag. After the surgeon issues a channel switching command, the host control unit can immediately switch the second channel from the sensing state to the energy output state based on this flag, thereby eliminating the delay of secondary contact judgment after switching. This significantly improves the response speed and surgical continuity when multiple ultrasound handpieces are used alternately, while avoiding the safety risk of accidental cutting caused by sudden energy output when an idle handpiece accidentally touches the soft tissue.

[0028] The host control unit executes the transition state identification logic, specifically as follows: The host control unit continuously acquires the resistance and capacitance components extracted by the tissue identification unit within a preset time window, and calculates the slope of the change of the resistance and capacitance components within the preset time window. The change slope is compared with a preset set of slope thresholds, which includes critical slope values ​​of tissue interfaces that characterize tissue type changes. When the host control unit determines that the current values ​​of the resistance component and the capacitance component exceed the hard tissue impedance threshold range and the change slope reaches the critical slope value of the tissue interface, it is determined that the scalpel tip is in the edge state of transition from hard tissue to soft tissue. In the edge state, the host control unit controls the corresponding ultrasonic drive channel to smoothly reduce the output continuous ultrasonic drive signal to below the soft tissue safety threshold.

[0029] The technical effects of the above solution are as follows: The transition state recognition logic continuously monitors the slope of the change in resistance and capacitance components and compares it with the preset critical slope value of the tissue interface. It can immediately capture the dynamic change trend of impedance parameters at the moment when the blade tip transitions from hard tissue to soft tissue, rather than waiting for the parameters to fall completely into the soft tissue area before responding. This allows for early control of the ultrasonic drive signal to smoothly decrease to below the safety threshold in the edge state. This not only avoids the discrimination lag and brief energy overshoot that may occur at the tissue interface in the traditional threshold comparison method, but also prevents uneven cutting surfaces or tissue traction damage caused by sudden stalling by gradually reducing energy rather than turning it off. Thus, it ensures the safety of soft tissue while taking into account the precision and continuity of the surgical operation.

[0030] The host control unit embeds safety interlock logic, specifically as follows: The effectiveness of the resistance and capacitance components extracted in real time by the tissue identification unit is verified. When the resistance and capacitance components exceed the impedance boundary range of normal biological tissue, it is determined that the electrode contact is abnormal. The host control unit then interrupts the corresponding ultrasound drive channel and puts the ultrasound drive channel into an idle lock state.

[0031] The technical effects of the above solution are as follows: the safety interlock logic verifies in real time whether the resistance and capacitance components are within the normal biological tissue impedance boundary range. When abnormal conditions such as electrode short circuit, open circuit or contact with metal instruments occur at the tip of the scalpel, it can immediately identify the abnormal electrode contact and automatically interrupt the output of the ultrasonic drive channel and lock it in an unloaded state. This avoids tissue misjudgment and uncontrolled energy release caused by sensor failure or accidental contact, and also protects the ultrasonic handle and the tip itself from electrical damage under abnormal load conditions.

[0032] The pulse protection unit has multiple preset protection levels, each corresponding to a set of preset pulse modulation parameters. These pulse modulation parameters include the pulse period and duty cycle, specifically: Based on the externally selected protection level, the pulse period and duty cycle corresponding to the protection level are extracted, and the continuous ultrasonic drive signal is turned off during a portion of the pulse period, with the pulse period as the interval, to form the intermittent pulse drive signal. The duty cycle is the ratio of the effective output period of the intermittent pulse drive signal to the entire pulse cycle.

[0033] The technical effects of the above-mentioned solution are as follows: The pulse protection unit, through the preset of multiple independent protection levels and their corresponding pulse period and duty cycle parameters, allows the surgeon to flexibly select the energy modulation strategy according to the actual working conditions such as the thermal sensitivity of the cutting site, the density of bone tissue, and the perfusion conditions. In this way, while maintaining efficient cutting of hard tissue, the periodic energy shut-off interval promotes heat dissipation and coolant perfusion in the surgical area, effectively inhibiting heat accumulation at the blade tip and bone interface, thereby reducing the risk of thermal necrosis of bone cells and thermal damage to adjacent soft tissues. Furthermore, the tissue recognition unit can continue to detect the tissue status during the shut-off period.

[0034] While outputting the intermittent pulse drive signal, the pulse protection unit continuously receives the resistance and capacitance components from the tissue identification unit, and determines the exit judgment time window based on the duty cycle set for the current protection level. The exit judgment time window is determined according to the following relationship: in, The duration of the exit judgment time window; The pulse cycle set for the current protection level; The duty cycle set for the current protection level, and ; The safety margin factor is an integer greater than or equal to 1. When the resistive and capacitive components are continuously and stably within the soft tissue impedance threshold range within the exit judgment time window, the host control unit controls the pulse protection unit to terminate the output of the intermittent pulse drive signal.

[0035] The technical effect of the above solution is as follows: By introducing a dynamic time window that is linked to the pulse period, duty cycle, and safety margin coefficient, the pulse protection unit can adaptively match the identification and exit judgment of soft tissue contact with the current energy modulation rhythm in the intermittent output state. The lower the duty cycle and the longer the pulse period, the longer the observation time required for continuous and stable soft tissue contact is. This effectively avoids premature exit misjudgment caused by the instantaneous return of the signal to the soft tissue region during the pulse turn-off gap. It ensures that continuous drive output is only restored after the blade tip has been stably detached from the hard tissue, thereby eliminating the distortion of the tissue state sampling window caused by pulse intermittency from the timing mechanism.

[0036] Working Principle: This invention achieves intelligent tissue identification and safety control through real-time dual-parameter impedance analysis. The tissue identification unit simultaneously acquires high-frequency current and voltage signals from the scalpel tip, extracting resistance and capacitance components. Compared to a single resistance parameter, this provides a more precise reflection of the dielectric differences between bone and soft tissues, thereby improving identification accuracy and anti-interference capabilities. The main control unit compares these two data points with preset hard and soft tissue impedance threshold ranges. When contact with hard tissue is detected, continuous ultrasonic drive signals are allowed to be output for cutting. Once the parameters fall within the soft tissue range, the drive output is immediately interrupted, preventing damage to nerves, blood vessels, and other structures. During hard tissue cutting, the pulse protection unit can modulate the continuous drive into intermittent pulse output at a selected level, reducing energy accumulation and lowering the temperature rise in the surgical area through periodic shutdown. This invention, through real-time identification of resistance and capacitance components, distinguishes between hard and soft tissues more accurately and reliably, reducing the surgeon's reliance on touch. The automatic energy cut-off upon contact with soft tissue significantly improves safety, thus achieving more precise and safer intelligent control of the surgical process.

[0037] In one embodiment, the host control unit executes the scalpel tip trajectory mapping and danger zone warning logic, specifically as follows: Acquire the patient's preoperative CT, MRI and 3D digital subtraction angiography data, and fuse the CT, MRI and 3D digital subtraction angiography image data into a unified coordinate system through rigid registration and elastic registration; A pre-trained 3D U-Net deep learning model was used to automatically segment the fused images and reconstruct bone tissue, nerve bundles, vascular plexus, dura mater, brain tissue and tumor boundaries. Mark the hazardous areas and construct a three-dimensional structural model of the hazardous areas, then import the three-dimensional structural model into the positioning coordinate system; Real-time multi-source positioning data is collected by a miniature electromagnetic sensor installed on the tip of a scalpel. Extended Kalman filtering is used to fuse the multi-source positioning data and output the scalpel tip pose sequence. The blade tip pose sequence is imported into the positioning coordinate system and aligned with the patient's preoperative image space using a spatial registration algorithm. The blade tip pose sequence is stored in chronological order to form a trajectory point column. The blade tip orientation vector at each trajectory point in the trajectory point column is determined. The blade tip cutting direction is determined based on the blade tip orientation vector. The blade tip motion state trajectory parameters and blade tip cutting state trajectory parameters are determined according to the blade tip cutting direction. Determine the statistical trajectory points corresponding to the cutting state trajectory parameters of the blade tip, and calculate the shortest Euclidean distance between each statistical trajectory point and the surface of each danger zone. The current cutting safety status is determined based on the shortest Euclidean distance. The host control unit automatically reduces the ultrasonic drive signal power to the preset safety power based on the current cutting safety status and the comparison between the shortest Euclidean distance and the preset safety distance, and highlights the target danger area. The deviation between the actual cutting range and the pre-planned path during surgery is calculated based on the parameters of the blade tip's motion trajectory and cutting trajectory. When the target deviation exceeds the preset deviation value, a direction correction prompt will be issued; When the scalpel tip is determined to have entered a dangerous area and the tissue identification unit identifies it as soft tissue, the ultrasonic drive signal is automatically interrupted and the device is locked, forcing the surgeon to perform an emergency retraction operation.

[0038] In this embodiment, rigid registration refers to aligning medical images of different modalities to a unified coordinate system through rigid body transformations such as rotation and translation, while maintaining the internal geometry of the images. Elastic registration, on the basis of rigid registration, allows local nonlinear deformation to eliminate differences caused by soft tissue or organ deformation, thereby achieving more accurate alignment.

[0039] In this embodiment, the pre-trained 3D U-Net deep learning model refers to a 3D convolutional neural network based on the U-Net architecture, which is pre-trained on a large-scale medical image segmentation dataset and is used to automatically segment bone tissue, nerve bundles, vascular plexuses, dura mater, brain tissue and tumor boundaries from fused images.

[0040] In this embodiment, the danger zone refers to key anatomical structures that should be avoided during surgery, including: nerve bundles, vascular plexuses, dura mater, brain tissue, and tumor boundaries (if the tumor is adjacent to an important functional area). These are automatically marked based on preoperative image segmentation results or manually marked by the surgeon.

[0041] In this embodiment, the miniature electromagnetic sensor refers to a miniature electromagnetic tracking sensor that can be installed on the tip of a scalpel. By receiving the alternating magnetic field generated by an external electromagnetic field generator, it outputs the six-degree-of-freedom pose data of the scalpel tip in space in real time.

[0042] In this embodiment, the extended Kalman filter is used to fuse multi-source localization data, suppress noise and drift, and output a smooth and accurate blade tip pose sequence.

[0043] In this embodiment, the scalpel tip pose sequence refers to the continuous record of the position (three-dimensional spatial coordinates) and orientation (orientation angle or rotation matrix) of the scalpel tip in a time sequence. Each sampling point contains a timestamp and the corresponding six-degree-of-freedom pose data.

[0044] In this embodiment, the blade tip orientation vector refers to the direction vector from the tail of the blade tip to the tip of the blade tip. It is usually calculated by combining the blade tip attitude data (such as Euler angles or quaternions) with the direction of the blade tip geometric axis, and is used to determine the cutting direction.

[0045] In this embodiment, the tool tip motion trajectory parameters refer to a set of parameters describing the tool tip motion behavior, including: moving speed, acceleration, rate of change of the angle of motion direction, jitter amplitude, etc., which are used to analyze whether the tool tip moves according to the planned path.

[0046] In this embodiment, the blade tip cutting trajectory parameters refer to parameters directly related to the cutting action, including: cutting depth, number of cutting blades, contact force estimation between the blade tip and bone tissue (indirectly calculated through impedance changes), effective cutting path length, etc., which are used to distinguish between a simple movement trajectory and the actual bone cutting process.

[0047] In this embodiment, statistical trajectory points refer to representative or key trajectory points selected from the cutting state trajectory parameters of the blade tip.

[0048] In this embodiment, the shortest Euclidean distance refers to the minimum straight-line distance between each statistical trajectory point and the surface of the 3D model of the danger zone.

[0049] In this embodiment, the preset safety distance refers to the safe buffer distance that the blade is allowed to be closest to the danger zone during surgical planning, and is set according to the importance level of the danger zone.

[0050] In this embodiment, the target deviation refers to the spatial deviation between the actual cutting range and the preoperative planned path, including: path tracking error (the vertical distance between the actual position of the blade tip and the planned path), directional deviation angle (the angle between the actual cutting direction and the planned direction), cutting depth deviation, etc.

[0051] In this embodiment, the preset deviation value refers to the maximum allowable deviation threshold between the cutting path and the planned path, for example: a positional deviation tolerance of 3mm and a directional deviation tolerance of 15°.

[0052] In this embodiment, the emergency retraction operation includes: when the blade tip has entered the danger zone (i.e., the shortest Euclidean distance ≤ 0) and the tissue identification unit determines it to be soft tissue, the device automatically locks the ultrasonic output and issues a clear audible and visual alarm to the operator, forcing the operator to manually retract the blade tip at least 5mm (or to a safe distance) along the entry path.

[0053] The beneficial effects of the above technical solution are as follows: the three-dimensional structure of the danger zone is reconstructed through preoperative multimodal image fusion and deep learning segmentation, and the scalpel tip pose is acquired in real time using a miniature electromagnetic sensor. Combined with extended Kalman filtering and spatial registration, the scalpel tip trajectory is dynamically mapped to the image space. Then, the shortest Euclidean distance between the scalpel tip and the danger zone is calculated, the deviation between the cutting path and the planned path is detected, and graded response measures such as power reduction warning, direction prompt, and even emergency energy cut-off and equipment locking are automatically taken according to different safety states. This realizes preoperative identification, real-time warning and automated safety braking of dangerous areas such as key nerves and blood vessels, which significantly reduces the risk of iatrogenic injury caused by the scalpel tip accidentally entering the danger zone or the cutting path deviating. At the same time, the forced emergency return operation logic further ensures the safe handling after accidental contact with soft tissue, improving the safety and controllability of complex and delicate surgery.

[0054] In one embodiment, the tissue identification unit can also determine hard tissue from soft tissue in the following way: Obtain the maximum index value, mean index value, and standard deviation of the resistance and capacitance components respectively, and calculate the fusion score based on the index values ​​using a preset weighted fusion scoring function: in, This is represented as a fusion score. This is represented as a resistance adaptive calculation weight. This is represented as the maximum index value corresponding to the resistance component. Represented as the average value of the index corresponding to the resistance component. This is expressed as the standard deviation of the index corresponding to the resistance component. This is represented as a capacitance-adaptive weight calculation. This is represented as the maximum index value corresponding to the capacitance component. This is represented by the average value of the index corresponding to the capacitance component. This is expressed as the standard deviation of the index corresponding to the capacitance component; The fusion score is mapped to an organization type probability using a preset logical function: in, This represents the probability of organization type, and e represents the natural constant with a value of 2.72. This is expressed as the mapping sensitivity coefficient. This is expressed as a decision bias. When P is greater than the preset probability, it is determined to be soft tissue; when 1-P is greater than the preset probability, it is determined to be hard tissue.

[0055] In this embodiment, the resistance adaptive calculation weights and capacitance adaptive calculation weights are determined by measuring the inter-class separability of the voltage and capacitance components in historical hard and soft tissue samples.

[0056] In this embodiment, the mapping sensitivity coefficient refers to the parameter that controls the steepness of the logic function curve. The larger γ is, the steeper the curve is and the higher the sensitivity to changes in the fusion score. It is usually set to a value of 1 to 5.

[0057] In this embodiment, the bias parameter of the decision bias logic function corresponds to the fusion score value when probability P=0.5. When = At that time, P=0.5. The optimal threshold for classifying hard and soft tissues can be determined based on the balance point for tissue type discrimination, for example, by obtaining the optimal threshold for classifying hard and soft tissues through statistical analysis of a large number of samples.

[0058] In this embodiment, the preset probability refers to the probability threshold used to determine the tissue type, which is usually set to 0.6.

[0059] The beneficial effects of the above technical solution are as follows: By extracting the maximum index value, mean, and standard deviation of the resistance and capacitance components respectively, and using an adaptive weighted fusion scoring function to integrate the statistical characteristics of the two parameters into a fusion score, which is then mapped to tissue type probability through a logical function, automatic determination of hard and soft tissues is achieved based on probability thresholds. Compared with the comparison of instantaneous values ​​at a single moment, the use of statistical features effectively reduces the interference of signal noise and instantaneous fluctuations on the discrimination results. At the same time, the weighted fusion and nonlinear mapping make tissue discrimination more stable and probabilistically interpretable, thereby significantly improving the robustness and accuracy of ultrasonic bone tissue surgical equipment in the identification of different tissue interfaces.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. An ultrasonic bone tissue surgical device for intelligent tissue assessment, characterized in that, include: The energy host (1) is equipped with a first ultrasound drive channel and a second ultrasound drive channel. At the same time, the energy host (1) is connected to an ultrasound handle and a control foot pedal (4) via lines. The ultrasound handles are the first ultrasound handle (2) and the second ultrasound handle (3). The energy host (1) responds to the channel switching command during the surgical operation and drives the corresponding first ultrasound handle (2) and second ultrasound handle (3) respectively. The tissue identification unit is integrated inside the energy host (1) and is configured to acquire, in real time, the high-frequency electrical signal flowing through the scalpel tip attached to the ultrasonic handpiece currently in working state in bone tissue cutting mode, and extract the resistance component and capacitance component in the high-frequency electrical signal. The host control unit is integrated in the energy host (1) and connected to the tissue identification unit and the first and second ultrasonic drive channels. It is configured to preset hard tissue impedance threshold range and soft tissue impedance threshold range. The resistance component and capacitance component are compared with the hard tissue impedance threshold range and soft tissue impedance threshold range respectively. When the resistance component and capacitance component fall into the hard tissue impedance threshold range, it is determined that the scalpel tip is in contact with hard tissue and the corresponding ultrasonic drive channel is controlled to output a continuous ultrasonic drive signal. When the resistance component and capacitance component fall into the soft tissue impedance threshold range, it is determined that the scalpel tip is in contact with soft tissue and the corresponding ultrasonic drive channel is controlled to interrupt the output of the ultrasonic drive signal. The pulse protection unit, integrated in the energy host (1), is configured to modulate the continuous ultrasonic drive signal into an intermittent pulse drive signal according to the externally selected protection level when the host control unit determines that the scalpel tip is in contact with hard tissue and controls the corresponding ultrasonic drive channel to output a continuous ultrasonic drive signal, thereby reducing the temperature of the surgical area.

2. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The tissue identification unit includes: An electrical signal acquisition module is configured to acquire a high-frequency current signal flowing through the tip of the scalpel and a high-frequency voltage signal applied to the tip of the scalpel; The impedance analysis module is configured to extract the phase difference information between the high-frequency current signal and the high-frequency voltage signal, and perform vector impedance calculation based on the amplitude of the two signals and the phase difference to separate the resistance component and the capacitance component.

3. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The tissue identification unit is also configured to: In the unloaded state where the ultrasonic handpiece is activated and the scalpel tip has not yet contacted the target tissue, the open circuit impedance value of the scalpel tip in the air medium is obtained and used as a reference value. Before determining the tissue type, the real-time extracted resistance and capacitance components are normalized using the reference value, and the normalized results are compared with the preset hard tissue impedance threshold range and soft tissue impedance threshold range.

4. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The host control unit has a built-in dual-channel collaborative scheduling logic, specifically: When the first ultrasonic driving channel is activated and the tissue recognition unit determines the type of tissue contacted by the scalpel tip, the second ultrasonic driving channel is placed in the tissue sensing and holding state. In the tissue sensing and holding state, the second ultrasonic drive channel maintains a detection voltage with an amplitude lower than the soft tissue cutting threshold between itself and the corresponding scalpel tip. The tissue identification unit pre-judges the contact state of the scalpel tip based on the electrical parameters in the detection voltage circuit. When the pre-judge result is contact with hard tissue, the host control unit generates a channel ready flag. After receiving the channel switching command, the host control unit controls the second ultrasound drive channel to switch from the tissue sensing and holding state to the energy output state according to the channel ready flag.

5. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The host control unit executes the transition state identification logic, specifically as follows: The host control unit continuously acquires the resistance and capacitance components extracted by the tissue identification unit within a preset time window, and calculates the slope of the change of the resistance and capacitance components within the preset time window. The change slope is compared with a preset set of slope thresholds, which includes critical slope values ​​of tissue interfaces that characterize tissue type changes. When the host control unit determines that the current values ​​of the resistance component and the capacitance component exceed the hard tissue impedance threshold range and the change slope reaches the critical slope value of the tissue interface, it is determined that the scalpel tip is in the edge state of transition from hard tissue to soft tissue. In the edge state, the host control unit controls the corresponding ultrasonic drive channel to smoothly reduce the output continuous ultrasonic drive signal to below the soft tissue safety threshold.

6. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The host control unit incorporates security interlock logic, specifically: The effectiveness of the resistance and capacitance components extracted in real time by the tissue identification unit is verified. When the resistance and capacitance components exceed the impedance boundary range of normal biological tissue, it is determined that the electrode contact is abnormal. The host control unit then interrupts the corresponding ultrasound drive channel and puts the ultrasound drive channel into an idle lock state.

7. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The pulse protection unit has multiple preset protection levels, each corresponding to a set of preset pulse modulation parameters. These pulse modulation parameters include the pulse period and duty cycle, specifically: Based on the externally selected protection level, the pulse period and duty cycle corresponding to the protection level are extracted, and the continuous ultrasonic drive signal is turned off during a portion of the pulse period, with the pulse period as the interval, to form the intermittent pulse drive signal. The duty cycle is the ratio of the effective output period of the intermittent pulse drive signal to the entire pulse cycle.

8. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, While outputting the intermittent pulse drive signal, the pulse protection unit continuously receives the resistance and capacitance components from the tissue identification unit, and determines the exit judgment time window based on the duty cycle set for the current protection level. The exit judgment time window is determined according to the following relationship: in, The duration of the exit judgment time window; The pulse cycle set for the current protection level; The duty cycle set for the current protection level, and ; The safety margin factor is an integer greater than or equal to 1. When the resistive and capacitive components are continuously and stably within the soft tissue impedance threshold range within the exit judgment time window, the host control unit controls the pulse protection unit to terminate the output of the intermittent pulse drive signal.

9. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The host control unit executes the scalpel tip trajectory mapping and danger zone warning logic, specifically as follows: Acquire the patient's preoperative CT, MRI and 3D digital subtraction angiography data, and fuse the CT, MRI and 3D digital subtraction angiography image data into a unified coordinate system through rigid registration and elastic registration; A pre-trained 3D U-Net deep learning model was used to automatically segment the fused images and reconstruct bone tissue, nerve bundles, vascular plexus, dura mater, brain tissue and tumor boundaries. Mark the hazardous areas and construct a three-dimensional structural model of the hazardous areas, then import the three-dimensional structural model into the positioning coordinate system; Real-time multi-source positioning data is collected by a miniature electromagnetic sensor installed on the tip of a scalpel. Extended Kalman filtering is used to fuse the multi-source positioning data and output the scalpel tip pose sequence. The blade tip pose sequence is imported into the positioning coordinate system and aligned with the patient's preoperative image space using a spatial registration algorithm. The blade tip pose sequence is stored in chronological order to form a trajectory point column. The blade tip orientation vector at each trajectory point in the trajectory point column is determined. The blade tip cutting direction is determined based on the blade tip orientation vector. The blade tip motion state trajectory parameters and blade tip cutting state trajectory parameters are determined according to the blade tip cutting direction. Determine the statistical trajectory points corresponding to the cutting state trajectory parameters of the blade tip, and calculate the shortest Euclidean distance between each statistical trajectory point and the surface of each danger zone. The current cutting safety status is determined based on the shortest Euclidean distance. The host control unit automatically reduces the ultrasonic drive signal power to the preset safety power based on the current cutting safety status and the comparison between the shortest Euclidean distance and the preset safety distance, and highlights the target danger area. The deviation between the actual cutting range and the pre-planned path during surgery is calculated based on the parameters of the blade tip's motion trajectory and cutting trajectory. When the target deviation exceeds the preset deviation value, a direction correction prompt will be issued; When the scalpel tip is determined to have entered a dangerous area and the tissue identification unit identifies it as soft tissue, the ultrasonic drive signal is automatically interrupted and the device is locked, forcing the surgeon to perform an emergency retraction operation.

10. The ultrasonic bone tissue surgical device for intelligent tissue judgment according to claim 1, characterized in that, The tissue identification unit can also distinguish between hard and soft tissue in the following ways: Obtain the maximum index value, mean index value, and standard deviation of the resistance and capacitance components respectively, and calculate the fusion score based on the index values ​​using a preset weighted fusion scoring function: in, This is represented as a fusion score. This is represented as a resistance adaptive calculation weight. This is represented as the maximum index value corresponding to the resistance component. Represented as the average value of the index corresponding to the resistance component. This is expressed as the standard deviation of the index corresponding to the resistance component. This is represented as a capacitor adaptive weight calculation. This is represented as the maximum index value corresponding to the capacitance component. This is represented by the average value of the index corresponding to the capacitance component. This is expressed as the standard deviation of the index corresponding to the capacitance component; The fusion score is mapped to an organization type probability using a preset logical function: in, This represents the probability of organization type, and e represents the natural constant with a value of 2.

72. This is expressed as the mapping sensitivity coefficient. This is expressed as a decision bias. When P is greater than the preset probability, it is determined to be soft tissue; when 1-P is greater than the preset probability, it is determined to be hard tissue.

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