CN107669334A - Ultrasound RF ablation temperature imaging method based on ultrasonic wave backscattered energy - Google Patents

Abstract

The present invention relates to a kind of ultrasound RF based on ultrasonic wave backscattered energy to melt temperature imaging method, including：Obtain detecting ultrasonic wave backscatter signals, i.e. primary data using ultrasonic probe；Bandpass filtering is carried out to primary data to reduce noise；Try to achieve the envelope of primary data；By sliding window, when being calculated in each window, try to achieve envelope square with step 3) and obtain the moment energy, divided by square of reference temperature lower envelope, now only retain positive backscattered energy, remove negative backscattered energy, that is, obtain the matrix of positive excess sound wave backscattered energy；It is interpolated to original image size；Image at different moments is combined and removes part noise.

Description

Ultrasonic radiofrequency ablation temperature imaging method based on ultrasonic backscattering energy

technical field

The invention belongs to the field of medical image research and relates to an ultrasonic radio frequency ablation temperature imaging method.

Background technique

In today's society, tumor is one of the important reasons that take away human life. Because it is still impossible to clarify the cause of the disease so as to prevent it, the treatment of tumors has become the focus of medical attention. Traditional treatment methods are mostly based on surgical resection, which causes great trauma to the patient's body. For small tumors, ablation can be used at present. There are methods such as high-energy focused ultrasonic ablation and radiofrequency ablation. The biggest advantage is that it is minimally invasive, so the audience can be very wide. The temperature during the burning process can be observed by nuclear magnetic resonance, ultrasonic waves, thermocouples, etc., but ultrasonic waves are harmless to the human body, low in cost, and easy to operate, so they have great research value.

Existing methods for temperature monitoring using ultrasound include echo time shift, backscattering energy (Ultrasonic backscattering energy, CBE for short), and the like. The echo time-shift method relies on tissue expansion and sound velocity changes caused by the increase in tissue temperature in the burning area to estimate the temperature. The backscattered energy relies on the change of the backscattered energy during the heating process to monitor the temperature, and the algorithm is simple and suitable for real-time monitoring.

Straube and Arthur of the University of Washington found that scatterers can be divided into positive and negative. The backscattering energy value of positive scatterers increases with the increase of temperature, and it shows a positive value during the ablation process. Decreases with increasing temperature and shows negative values during ablation. On the basis of Sigelment and Reid, it calculated the normalized model of the relationship between the backscattering energy change and temperature change of single scatterers [1-5], such as formula (1-1):

Among them, α(T) is the attenuation coefficient, and η(T) is the backscattering coefficient. If the size of the scatterer is smaller than the ultrasonic wavelength, the model can be simplified to formula (1-2):

CBE=η(T)/η(37) (1-2)

Tsui P H et al. found that canceling the displacement compensation of the original data can also obtain the relationship between the backscattered energy and temperature, and the sensitivity is higher and the time is saved [6].

Based on the above theory, Xia Jingjing and others proposed the method of integrating ultrasonic backscatter energy (ICBE) and sliding window to obtain the temperature distribution image of the heating area. Inverted, the temperature distribution is displayed with positive backscattered energy. The integrated backscatter energy value in each window of the sliding window:

When the integrated ultrasonic backscattered energy method is used in real tissue radiofrequency ablation, it is found that there will be artifacts under the burning needle, which affects the correlation between the integrated ultrasonic backscattered energy value and the temperature value, and also seriously affects the temperature distribution image of the tissue.

references:

[1] Straube W L and Arthur R M, Theoretical Estimation of the Temperature Dependence of Backscattered Ultrasonic Power for Noninvasive Thermometry, Ultrasound in Medicine & Biology, 1994, 20(9): 915-922.

[2] Arthur R M, Trobaugh J W, Straube W L, et al., Temperature Dependence of Ultrasonic Backscattered Energy in Images Compensated for Tissue Motion, 2003 IEEE Symposium on Ultrasonics, 2003, 1:990～993.

[3] Arthur R M, Trobaugh J W, Straube W L, et al., Temperature Dependence of Ultrasonic Backscattered Energy in Motion Compensated Images, Ultrasonics, Ferroelectrics, and Frequency Control, 2005, 52(10): 1644～1652.

[4] Arthur R M, Straube W L, Starman J D, et al., Noninvasive Temperature Estimation Based on the Energy of Backscattered Ultrasound, Medical physics, 2003, 30(6): 1021～1029.

[5] Arthur R M, Straube W L, Trobaugh J W, et al., Non-Invasive Estimation of Hyperthermia Temperatures with Ultrasound, International journal of hyperthermia, 2005, 21(6): 589～600.

[6] Po-Hsiang Tsui, Yu-Ting Chien, et al, Using Ultrasound CBE Imaging Without Echo Shift Compensation for Temperature Estimation, Ultrasonics, 2012, 52:925–935.

Contents of the invention

The purpose of the present invention is to provide an ultrasonic radiofrequency ablation temperature imaging method that can effectively remove artifacts, make the temperature distribution image more accurate, and better conform to the temperature value change curve. The technical scheme is as follows:

A temperature imaging method for ultrasonic radiofrequency ablation based on ultrasonic backscattering energy, comprising the following steps:

1) Use the ultrasonic probe to obtain the detected ultrasonic backscatter signal, that is, the initial data;

2) Perform band-pass filtering on the initial data to reduce noise;

3) Obtain the envelope of the initial data;

4) Through the sliding window, when calculating in each window, use step 3) to obtain the envelope square to obtain the energy at this moment, divide it by the envelope square at the reference temperature, and only keep the positive backscattering energy at this time, remove Negative backscattered energy, that is, the matrix of positive ultrasonic backscattered energy;

5) interpolation into the original image size;

6) Combining images at different times to remove part of the noise and displaying them;

7) Circle the region of interest, average the part of the matrix obtained in step 4) in the region of interest, obtain the forward and back scattering energy values in the region of interest, and perform subsequent calculation of the ablation area.

The beneficial effects of the present invention are as follows:

1. When the integrated ultrasonic backscatter energy is used for radiofrequency ablation, serious artifacts will be produced under the burning needle. The use of positive ultrasonic backscattering energy can effectively remove artifacts, make the temperature distribution image more accurate, and can be better used in clinical practice.

2. The fitting effect of positive ultrasonic backscattered energy and temperature is better than that of integrated ultrasonic backscattered energy. Therefore, using forward backscattered energy can better understand the change of temperature value during ablation.

Description of drawings

Accompanying drawing 1 is the flow chart of the method of the present invention.

Accompanying drawing 2 is the comparison chart of positive ultrasonic backscattering energy method, comprehensive ultrasonic backscattering energy method and temperature curve respectively.

detailed description

The ultrasonic radio frequency ablation temperature imaging method based on ultrasonic backscattering energy of the present invention utilizes the positive ultrasonic backscattering energy (Positive ultrasonic backscattering energy, referred to as PCBE) method to solve the artifact problem of the temperature distribution image presented in real time during the radio frequency ablation process Improvements are made, and the value of the positive ultrasonic backscattered energy is more in line with the curve of the temperature value.

In the process of temperature monitoring, only the positive backscattered energy part is kept, and the negative backscattered energy part is removed, that is, only the positive backscattered energy is used to display the temperature distribution image and calculate the backscattered energy value , in the real-time temperature monitoring of radiofrequency ablation, it can effectively improve the artifacts under the burning needle, and the positive ultrasonic backscatter energy value is more in line with the temperature curve than the integrated ultrasonic backscatter energy value.

Specific steps are as follows:

1) Use the ultrasonic probe to obtain the detected ultrasonic backscatter signal, that is, the initial data;

2) Perform bandpass filtering on the initial data to reduce noise

3) Obtain the envelope of the initial data

4) Through the sliding window, when calculating in each window, use step 3) to obtain the envelope square to obtain the energy at this moment, divide it by the envelope square at the reference temperature, and only keep the positive backscattering energy at this time, remove Negative backscattered energy, that is, the matrix to obtain positive ultrasonic backscattered energy

5) Interpolate to the original image size

6) Combine images at different times to remove part of the noise and display

7) Circle the region of interest, average the part of the matrix obtained in step 4) in the region of interest, and obtain the forward and back scattering energy values in the region of interest. It is also possible to calculate the subsequent ablation area, etc.

Examples are as follows:

Place the pork tenderloin of appropriate size in an acrylic box, insert the radio frequency burning needle into the inside of the pork tenderloin through the small hole on the box, the burning needle carries water circulation, and the temperature is monitored by a thermocouple. Use an ultrasonic probe to find the cutting surface of the needle tip, and burn in 50W mode. Record an initial data every two seconds, and continue heating for 12 minutes.

Process the obtained data: based on the center frequency of the experimental ultrasonic probe, filter each piece of data to remove noise outside the bandwidth; perform Hilbert transform on the data with noise removed to obtain the signal envelope; convert the image to Divide into many windows of the same size to obtain the positive ultrasonic backscatter energy value in each window; interpolate the obtained matrix to become the original image size; compound data at different times to eliminate part of the noise; The temperature distribution image of the backscattered energy is displayed, and on this basis, the average value of the forward ultrasonic backscattered energy in the region of interest is calculated and compared with the temperature value recorded by the thermocouple.

The obtained results can be compared with the integrated ultrasonic backscattered energy (ICBE) method to verify the advantages of positive ultrasonic backscattered energy (PCBE) in radiofrequency ablation temperature monitoring.

Claims (1)

1. a kind of ultrasound RF ablation temperature imaging method based on ultrasonic wave backscattered energy, comprises the following steps：

1) obtain detecting ultrasonic wave backscatter signals, i.e. primary data using ultrasonic probe；

2) bandpass filtering is carried out to primary data to reduce noise；

3) envelope of primary data is tried to achieve；

4) by sliding window, when being calculated in each window, try to achieve envelope square with step 3) and obtain the moment energy, divided by reference Square of temperature lower envelope, now only retain positive backscattered energy, remove negative backscattered energy, that is, obtain positive excess sound The matrix of ripple backscattered energy；

5) it is interpolated to original image size；

6) image at different moments is combined and removes part noise, and shown；

7) circle selects area-of-interest, and part of the matrix that step 4) is obtained in area-of-interest is averaged, and it is emerging to try to achieve sense Positive backscattered energy value in interesting region, it can also carry out the calculating of follow-up ablation area.