Microwave ablation standing wave real-time detection and carbonization early warning system and method

Abstract

The present application relates to the field of microwave ablation, in particular to a microwave ablation standing wave real-time detection and carbonization early warning system and method. The system comprises a microwave energy source, an ablation antenna, a signal sampling module, a signal conversion module, a phase detection module and a signal processing module. The microwave energy source outputs a microwave signal; the ablation antenna radiates the microwave signal; the signal sampling module synchronously samples the transmitted power signal and the reflected power signal; the signal conversion module converts the transmitted and reflected power signals into first and second voltage signals respectively; the phase detection module detects the original phase difference between the first and second voltage signals; and the signal processing module calculates the standing wave ratio, the standing wave ratio change rate and the equivalent phase difference, and performs corresponding carbonization early warning based on the calculation results. Through the cooperative analysis of the standing wave ratio, the standing wave ratio change rate and the equivalent phase difference, the present application can realize the hierarchical early warning of different states of the diseased tissue, and reserve sufficient intervention and adjustment time for the operator.

Description

Technical Field

[0001] This invention relates to the field of microwave ablation technology, and in particular to a microwave ablation standing wave real-time detection and carbonization early warning system and method. Background Technology

[0002] Microwave ablation is a minimally invasive treatment technique that uses the thermal effect of microwaves to inactivate diseased tissue. Compared to traditional surgery, microwave ablation has advantages such as less trauma and better efficacy. However, during the ablation process, if excessive energy deposition leads to excessively high local temperatures, the diseased tissue will carbonize. This not only restricts heat conduction and affects the ablation effect, but may also cause thermal damage to surrounding normal tissues. Therefore, effective carbonization warnings during microwave ablation, allowing operators to make adaptive adjustments, are of great significance for ensuring surgical safety and treatment effectiveness.

[0003] When diseased tissue undergoes dehydration, denaturation, or even carbonization under microwave irradiation, the load impedance of the ablation antenna shifts significantly, increasing the reflected power of the microwave transmission link and resulting in a marked increase in the voltage standing wave ratio (VSWR). Therefore, current technologies typically use VSWR detection for early carbonization warnings. However, this approach ignores the characteristic signals generated in the early stages of tissue carbonization, making it difficult to provide early warning before carbonization occurs and failing to allow sufficient time for operators to adjust and intervene. Summary of the Invention

[0004] The purpose of this invention is to provide a microwave ablation standing wave real-time detection and carbonization early warning system and method to solve the technical problems in the prior art that only use the standing wave ratio for carbonization early warning, which cannot predict carbonization risks in advance and operators lack sufficient time for intervention and adjustment.

[0005] The technical solution of this invention is: a microwave ablation standing wave real-time detection and carbonization early warning system, comprising: A microwave energy source used to output microwave signals; An ablation antenna is connected to the end of the microwave transmission path of the microwave energy source and is used to radiate microwave signals. A signal sampling module is located on the microwave transmission path from the microwave energy source to the ablation antenna, and is used to synchronously sample the transmitted power signal and the reflected power signal; A signal conversion module, connected to the signal sampling module, is used to convert the transmitted power signal into a first voltage signal and the reflected power signal into a second voltage signal; A phase detection module, connected to the signal conversion module, is used to detect the original phase difference between the first voltage signal and the second voltage signal; The signal processing module, connected to both the signal conversion module and the phase detection module, is used for: Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; Calculate the equivalent phase difference based on the original phase difference; Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, a corresponding carbonization warning is executed.

[0006] Preferably, the method for calculating the equivalent phase difference is as follows:

[0007] in, The equivalent phase difference, Let β be the original phase difference, β be the equivalent propagation constant of the microwave signal in the microwave transmission path, L be the equivalent electrical length from the signal sampling module to the ablation antenna, and 2βL represent the round-trip propagation phase delay of the microwave signal from the signal sampling module to the ablation antenna. The system has a fixed phase offset.

[0008] Preferably, the signal processing module pre-stores a precursor threshold, a first threshold, a second threshold, and a high-risk threshold, wherein the high-risk threshold is greater than the precursor threshold, and the carbonization early warning determination logic of the signal processing module is as follows: If the standing wave ratio is less than the precursor threshold, the standing wave ratio change rate is less than the first threshold, and the equivalent phase difference is less than the second threshold, then no warning processing will be performed; If the standing wave ratio is less than the precursor threshold, but the rate of change of the standing wave ratio is greater than or equal to the first threshold or the equivalent phase difference is greater than or equal to the second threshold, then a first-level warning is issued. If the standing wave ratio is greater than or equal to the precursor threshold and less than the high-risk threshold, a level-two warning is issued; If the VSWR is greater than or equal to the high-risk threshold, a Level 3 warning will be issued.

[0009] Preferably, the first-level warning is to limit the power increase of the microwave energy source and output a visual or auditory signal; The secondary warning is to reduce the output power of the microwave energy source and output a visual or auditory signal; The three-level warning means stopping the microwave energy source from outputting microwave signals, outputting visual or auditory signals, and prohibiting the microwave energy source from outputting microwave signals within a preset protection time.

[0010] Preferably, the signal sampling module includes a dual directional coupler, which is connected in series in the microwave transmission path between the microwave energy source and the ablation antenna. Its forward coupling port is used to output the transmitted power signal, and its reverse coupling port is used to output the reflected power signal.

[0011] Preferably, the signal conversion module includes: The first conversion branch includes a first logarithmic detector and a first amplifier. The first logarithmic detector is used to convert the transmit power signal into a first detector voltage signal, and the first amplifier is used to amplify the first detector voltage signal to output the first voltage signal. The second conversion branch includes a second logarithmic detector and a second amplifier. The second logarithmic detector is used to convert the reflected power signal into a second detected voltage signal, and the second amplifier is used to amplify the second detected voltage signal to output the second voltage signal.

[0012] Preferably, the signal conversion module further includes: The first filter is connected in series with the first conversion branch and is located before the first logarithmic detector. The second filter is connected in series with the second conversion branch and is located before the second logarithmic detector.

[0013] On the other hand, this application also discloses a method for real-time detection and carbonization early warning of microwave ablation standing waves, applied to any of the microwave ablation standing wave real-time detection and carbonization early warning systems described in this application, comprising: Simultaneously acquire the transmit power signal and the reflected power signal; The transmitted power signal and the reflected power signal are respectively converted into a first voltage signal and a second voltage signal; Detect the original phase difference between the first voltage signal and the second voltage signal; Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; calculate the equivalent phase difference based on the original phase difference. Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, a corresponding carbonization warning is executed.

[0014] Compared with the prior art, the advantages of this invention are: the introduction of two types of precursor characteristic parameters, namely standing wave ratio change rate and equivalent phase difference, can achieve early identification and warning before irreversible carbonization of diseased tissue, providing operators with sufficient power adjustment and intervention window, improving the safety of microwave ablation surgery, and reducing the risk of thermal damage to normal tissue caused by carbonization. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the structure of a microwave ablation standing wave real-time detection and carbonization early warning system according to the present invention; Figure 2 This is a flowchart of a microwave ablation standing wave real-time detection and carbonization early warning method according to the present invention; Figure 3 This is a standing wave ratio time relationship curve in one embodiment of the present invention; Figure 4 This is a time-dependent curve showing the rate of change of the standing wave ratio in one embodiment of the present invention; Figure 5 This is an equivalent phase difference time relationship curve in one embodiment of the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments: In this application, terms such as "first" and "second" are used only to distinguish different objects and do not indicate any limitation on order, quantity, or importance. Expressions such as "comprising," "including," and "having" are open-ended expressions, indicating that they may include not only the explicitly listed technical features but also other technical features that are not explicitly listed but can achieve the corresponding functions. "Connection" includes direct connection and indirect connection.

[0017] When using microwave ablation to inactivate lesions, carbonization is not an instantaneous event, but a gradual process: as the lesion is exposed to the thermal effect of microwaves, its internal moisture gradually evaporates. After dehydration, the lesion does not immediately carbonize, but irreversible carbonization occurs as temperature continues to accumulate. Current technologies rely solely on standing wave ratio (SWR) detection, often triggering protection only after substantial carbonization has occurred in the lesion, thus missing the optimal intervention window.

[0018] Therefore, this application provides a method such as Figure 1 The microwave ablation standing wave real-time detection and carbonization early warning system shown includes: A microwave energy source used to generate microwave signals.

[0019] Specifically, microwaves refer to electromagnetic waves with frequencies between 300MHz and 300GHz. In medical applications, 915MHz and 2450MHz microwaves are commonly used. The higher the microwave frequency, the shallower the penetration depth and the more significant the signal attenuation; at the same output power, 2450MHz microwaves have a wider ablation range. Microwave energy sources generate continuous wave or pulse-modulated microwave signals of 915MHz or 2450MHz, with an output power range of 5W to 150W.

[0020] An ablation antenna is connected to the end of the microwave transmission path of a microwave energy source to radiate microwave signals.

[0021] Specifically, during microwave ablation surgery, the ablation antenna is directly inserted into the diseased tissue. The thermal effect generated by microwave radiation causes irreversible protein denaturation and coagulative necrosis. The typical impedance of the ablation antenna is 50Ω, and its length is 150~200mm.

[0022] The signal sampling module is used to simultaneously sample the transmitted power signal and the reflected power signal along the microwave transmission path from the microwave energy source to the ablation antenna.

[0023] In one embodiment, the signal sampling module includes a dual directional coupler connected in series in the microwave transmission path between the microwave energy source and the ablation antenna. The forward coupling port is used to output the transmitted power signal, and the reverse coupling port is used to output the reflected power signal. For example, the coupling degree of the dual directional coupler is 30 dB (±1 dB), and the directivity of the forward and reverse couplings is greater than or equal to 20 dB.

[0024] The signal conversion module, connected to the signal sampling module, is used to convert the transmitted power signal into a first voltage signal and the reflected power signal into a second voltage signal.

[0025] In one embodiment, the signal conversion module includes: The first conversion branch includes a first logarithmic detector and a first amplifier. The first logarithmic detector is used to convert the transmit power signal into a first detected voltage signal, and the first amplifier is used to amplify the first detected voltage signal to output a first voltage signal. The second conversion branch includes a second logarithmic detector and a second amplifier. The second logarithmic detector is used to convert the reflected power signal into a second detected voltage signal, and the second amplifier is used to amplify the second detected voltage signal to output a second voltage signal.

[0026] Specifically, the first and second logarithmic detectors can be equipped with AD8307 logarithmic detector chips, which have a dynamic range of 70dB and an output slope of 25mV / dB. Using the same detector chip in both the first and second conversion branches ensures that the voltage conversion characteristics of the transmitted and reflected power signals are completely consistent, eliminating measurement errors introduced by device differences. The first and second amplifiers respectively amplify the first and second detected voltage signals with fixed gain, adjusting the signal amplitude to match the input range of the sampling unit in the signal processing module to ensure sampling accuracy.

[0027] In another embodiment, the signal conversion module further includes: The first filter is connected in series in the first conversion branch and is located before the first logarithmic detector; The second filter is connected in series in the second conversion branch and is located before the second logarithmic detector.

[0028] Specifically, when using 2450MHz microwave, the first and second filters can be low-pass filters with a cutoff frequency of 3GHz to filter out high-order harmonics and radio frequency spurious interference generated during the transmission of transmitted and reflected power signals.

[0029] The phase detection module, connected to the signal conversion module, is used to detect the original phase difference between the first voltage signal and the second voltage signal.

[0030] In one embodiment, the phase detection module includes a single-channel phase detector, the input terminals of which are respectively connected to a first voltage signal and a second voltage signal, and the output signal is the original phase difference.

[0031] In another embodiment, the phase detection module includes a first phase detector and a second phase detector. The input terminal of the first phase detector is connected to a reference frequency source and a first voltage signal, respectively, and the output signal is a first phase difference. The input terminal of the second phase detector is connected to a reference frequency source and a second voltage signal, respectively, and the output signal is a second phase difference. The signal processing module uses the difference between the first phase difference and the second phase difference as the original phase difference. The reference frequency source is the reference signal source of the microwave energy source, and the microwave signal output by the microwave energy source is generated by amplifying the reference signal output from the reference frequency source.

[0032] The signal processing module, connected to both the signal conversion module and the phase detection module, is used for: Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; Calculate the equivalent phase difference based on the original phase difference; Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, corresponding carbonization early warning is executed.

[0033] In one embodiment, the signal processing module includes a sampling unit, a calculation unit, a storage unit, a power control unit, and an alarm unit. The sampling unit synchronously samples the first voltage signal and the second voltage signal output by the signal conversion module, as well as the original phase difference analog signal output by the phase detection module, and converts these analog signals into digital signals that can be processed by digital circuits. For example, an ADS1115 ADC chip can be used. The calculation unit receives the digital signal output by the sampling unit, calculates the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference in real time, and executes corresponding carbonization warnings based on the calculation results. The calculation unit can be a central processing unit (CPU), a microcontroller (MCU), a digital signal processor (DSP), or a combination of these devices. The storage unit mainly includes a program storage area and a data storage area, used to store the program code, threshold parameters, and intermediate calculation results required for the operation of the signal processing module. The power control unit is connected to the electrical control terminal of the microwave energy source and is used to control the output power of the microwave energy source according to the warning level. The alarm unit may include a visual subunit or an auditory subunit. The visual subunit may be an LED indicator, and the auditory subunit may be a buzzer, used to issue different levels of warning signals to prompt the operator to make corresponding adjustments.

[0034] In another embodiment, the signal processing module further includes an input unit. The operator can input pre-calibrated first threshold, second threshold, precursor threshold, and high-risk threshold based on the calibration results of the ex vivo tissue ablation experiment. The signal processing module stores these values ​​in a storage unit for real-time retrieval. Exemplary values ​​are as follows: first threshold is 0.1 / min, second threshold is 30°, precursor threshold is 1.3, and high-risk threshold is 1.6.

[0035] The signal processing module pre-stores a precursor threshold, a first threshold, a second threshold, and a high-risk threshold, with the high-risk threshold being greater than the precursor threshold. Its carbonization early warning determination logic is as follows: If the VSWR is less than the precursor threshold, the VSWR rate of change is less than the first threshold, and the equivalent phase difference is less than the second threshold, no warning is issued. If the VSWR is less than the precursor threshold, but the VSWR rate of change is greater than or equal to the first threshold or the equivalent phase difference is greater than or equal to the second threshold, a Level 1 warning is issued. If the VSWR is greater than or equal to the precursor threshold and less than the high-risk threshold, a Level 2 warning is issued. If the VSWR is greater than or equal to the high-risk threshold, a Level 3 warning is issued. It should be noted that different visual or auditory signals are used for different warning levels to facilitate quick identification by operators.

[0036] When the signal processing module issues a Level 1 warning, it indicates that the thermal state of the lesion tissue has begun to change significantly. At this time, the signal processing module will limit the increase of microwave energy source power and control the alarm unit to output visual or auditory signals. The operator should observe the image of the ablation zone and appropriately reduce the microwave energy source power or fine-tune the position of the ablation antenna to avoid excessive heat deposition. When the signal processing module issues a Level 2 warning, it indicates that the lesion tissue is undergoing extensive dehydration and vaporization, and is close to carbonization. The signal processing module will automatically reduce the microwave energy source power and control the alarm unit to output visual or auditory signals. The operator should immediately assess the ablation situation and further reduce the microwave energy source power or suspend ablation. When the signal processing module issues a Level 3 warning, it indicates that the lesion tissue is severely dehydrated and vaporized, with an extremely high risk of carbonization. The signal processing module will immediately cut off the microwave energy source output, control the alarm unit to output visual or auditory signals, and lock and restart within the preset protection time (e.g., 90 seconds) to terminate energy deposition. The operator must stop the operation at this time and wait for the lesion tissue to cool down.

[0037] The calculation methods for the parameters upon which the above early warning judgment relies are as follows: The method for calculating the standing wave ratio is as follows:

[0038]

[0039]

[0040] in, This is the second voltage signal. S is the first voltage signal, and S is the output slope of the logarithmic detector (unit: mV / dB). This represents the magnitude of the reflection coefficient.

[0041] The method for calculating the rate of change of standing wave ratio is as follows:

[0042] in, For the current standing bogey, For the standing poppy of the previous moment, The preset time window width (e.g., 50ms).

[0043] The method for calculating the equivalent phase difference is as follows:

[0044] in, For equivalent phase difference, Let β be the original phase difference, β be the equivalent propagation constant of the microwave signal, L be the equivalent electrical length from the signal sampling module to the ablation antenna, and 2βL represent the round-trip propagation phase delay of the microwave signal from the signal sampling module to the ablation antenna. A fixed phase offset is applied to the system. For example, β and L can be obtained by measuring the microwave transmission path using a network analyzer. The original phase difference can be measured by the phase detection module under the condition that the microwave energy source is outputting at low power (e.g., 1W) and the ablation antenna is inserted into the lesion tissue. The measurement at this time That is The above β, L, It is pre-stored in the signal processing module.

[0045] Figure 3 , Figure 4 , Figure 5 This is a specific embodiment of the present application, showing the changes in VSWR, VSWR rate of change, and equivalent phase difference over time. In this embodiment, the experimental subject is liver tumor tissue, the microwave energy source has an output power of 50W and an operating frequency of 2450MHz, and the initial temperature of the liver tumor tissue is 37℃. VSWR characterizes the impedance matching state between the ablation antenna and the liver tumor tissue; VSWR rate of change reflects the worsening trend of impedance mismatch; and equivalent phase difference reflects the change in the dielectric constant inside the liver tumor tissue due to water evaporation and thermal denaturation. This application combines the judgment of these three characteristics to achieve graded early warning of carbonization.

[0046] In summary, this application distinguishes the thermal evolution state of lesions during microwave ablation by jointly judging the standing wave ratio (SWR), the rate of change of SWR, and the equivalent phase difference, and performs early warning processing such as power adjustment and audible and visual alarms. It can identify precursor signals of carbonization before irreversible carbonization of the lesion tissue occurs, providing operators with sufficient intervention and adjustment windows, effectively avoiding carbonization of the lesion tissue and burns to surrounding normal tissue caused by excessive heat deposition, and improving the safety and therapeutic effect of microwave ablation surgery.

[0047] This application also provides a method such as Figure 2 The microwave ablation standing wave real-time detection and carbonization early warning method shown includes: Simultaneously acquire the transmit power signal and the reflected power signal; The transmitted power signal and the reflected power signal are respectively converted into a first voltage signal and a second voltage signal; Detect the original phase difference between the first voltage signal and the second voltage signal; Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; calculate the equivalent phase difference based on the original phase difference. Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, a corresponding carbonization warning is executed.

[0048] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

Claims

1. A microwave ablation standing wave real-time detection and carbonization early warning system, characterized in that, include: A microwave energy source used to output microwave signals; An ablation antenna is connected to the end of the microwave transmission path of the microwave energy source and is used to radiate microwave signals. A signal sampling module is located on the microwave transmission path from the microwave energy source to the ablation antenna, and is used to synchronously sample the transmitted power signal and the reflected power signal; A signal conversion module, connected to the signal sampling module, is used to convert the transmitted power signal into a first voltage signal and the reflected power signal into a second voltage signal; A phase detection module, connected to the signal conversion module, is used to detect the original phase difference between the first voltage signal and the second voltage signal; The signal processing module, connected to both the signal conversion module and the phase detection module, is used for: Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; Calculate the equivalent phase difference based on the original phase difference; Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, a corresponding carbonization warning is executed.

2. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 1, characterized in that, The method for calculating the equivalent phase difference is as follows: ， in, The equivalent phase difference, Let β be the original phase difference, β be the equivalent propagation constant of the microwave signal in the microwave transmission path, L be the equivalent electrical length from the signal sampling module to the ablation antenna, and 2βL represent the round-trip propagation phase delay of the microwave signal from the signal sampling module to the ablation antenna. The system has a fixed phase offset.

3. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 1, characterized in that, The signal processing module pre-stores a precursor threshold, a first threshold, a second threshold, and a high-risk threshold. The high-risk threshold is greater than the precursor threshold. The carbonization early warning determination logic of the signal processing module is as follows: If the standing wave ratio is less than the precursor threshold, the standing wave ratio change rate is less than the first threshold, and the equivalent phase difference is less than the second threshold, then no warning processing will be performed; If the standing wave ratio is less than the precursor threshold, but the rate of change of the standing wave ratio is greater than or equal to the first threshold or the equivalent phase difference is greater than or equal to the second threshold, then a first-level warning is issued. If the standing wave ratio is greater than or equal to the precursor threshold and less than the high-risk threshold, a level-two warning is issued; If the VSWR is greater than or equal to the high-risk threshold, a Level 3 warning will be issued.

4. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 3, characterized in that: The first-level warning is to limit the power increase of the microwave energy source and output a visual or auditory signal; The secondary warning is to reduce the output power of the microwave energy source and output a visual or auditory signal; The three-level warning means stopping the microwave energy source from outputting microwave signals, outputting visual or auditory signals, and prohibiting the microwave energy source from outputting microwave signals within a preset protection time.

5. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 1, characterized in that: The signal sampling module includes a dual directional coupler, which is connected in series in the microwave transmission path between the microwave energy source and the ablation antenna. Its forward coupling port is used to output the transmitted power signal, and its reverse coupling port is used to output the reflected power signal.

6. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 1, characterized in that, The signal conversion module includes: The first conversion branch includes a first logarithmic detector and a first amplifier. The first logarithmic detector is used to convert the transmit power signal into a first detector voltage signal, and the first amplifier is used to amplify the first detector voltage signal to output the first voltage signal. The second conversion branch includes a second logarithmic detector and a second amplifier. The second logarithmic detector is used to convert the reflected power signal into a second detected voltage signal, and the second amplifier is used to amplify the second detected voltage signal to output the second voltage signal.

7. The microwave ablation standing wave real-time detection and carbonization early warning system according to claim 6, characterized in that, The signal conversion module also includes: The first filter is connected in series with the first conversion branch and is located before the first logarithmic detector. The second filter is connected in series with the second conversion branch and is located before the second logarithmic detector.

8. A method for real-time detection and carbonization early warning of microwave ablation standing waves, characterized in that, The system is applied to the microwave ablation standing wave real-time detection and carbonization early warning system as described in any one of claims 1-7, comprising: Simultaneously acquire the transmit power signal and the reflected power signal; The transmitted power signal and the reflected power signal are respectively converted into a first voltage signal and a second voltage signal; Detect the original phase difference between the first voltage signal and the second voltage signal; Calculate the standing wave ratio and the rate of change of standing wave ratio based on the first voltage signal and the second voltage signal; calculate the equivalent phase difference based on the original phase difference. Based on the standing wave ratio, the rate of change of the standing wave ratio, and the equivalent phase difference, a corresponding carbonization warning is executed.

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