CN107669334B - Ultrasonic radio frequency ablation temperature imaging device based on ultrasonic backscattering energy - Google Patents

Abstract

The invention relates to an ultrasonic radio frequency ablation temperature imaging method based on ultrasonic back scattering energy, which comprises the following steps: obtaining a detection ultrasonic backscattering signal, namely initial data, by using an ultrasonic probe; performing band-pass filtering on the initial data to reduce noise; obtaining an envelope of the initial data; through sliding windows, when calculating in each window, obtaining the square of the envelope in the step 3) to obtain the energy at the moment, dividing the energy by the square of the envelope at the reference temperature, only keeping positive backscatter energy at the moment, and removing negative backscatter energy to obtain a matrix of the positive ultrasonic backscatter energy; interpolating to obtain the size of the original image; and combining the images at different moments to remove part of noise.

Description

Ultrasonic radiofrequency ablation temperature imaging device based on ultrasonic backscattered energy

technical field

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

Background technique

In today's society, tumor is one of the important reasons for taking human life. Because the cause of the disease cannot be identified and prevention can be performed, the treatment of tumors has become the focus of the medical community. The traditional treatment methods are mostly surgical excision, which is very traumatic to the patient's body. For smaller tumors, ablation can be used at present, including high-energy focused ultrasonic ablation and radiofrequency ablation. The biggest advantage is minimally invasive, so the audience can be very wide. The temperature during the burning process can be observed by nuclear magnetic resonance, ultrasound, thermocouple, etc., but ultrasound has the characteristics of harmless to human body, low cost, and easy operation, so it has great research value.

Existing methods for temperature monitoring using ultrasonic waves include echo time shift, backscattering energy (Ultrasonic backscattering energy, CBE for short), and the like. The echo time-shift method relies on the tissue expansion and sound velocity changes caused by the increase of tissue temperature in the burning area to estimate the temperature, but parameters such as tissue expansion coefficient need to be determined in advance, and the temperature rise is up to 40 °C. The backscattered energy relies on the change of the backscattered energy during the heating process to monitor the temperature. The algorithm is simple and suitable for real-time monitoring.

Straube and Arthur of the University of Washington found that scatterers have positive and negative points. The backscattering energy value of positive scatterers increases with the increase of temperature, and shows a positive value during the ablation process. The backscattering energy value of negative scatterers increases with the increase of temperature. It decreases with increasing temperature, showing a negative value during ablation. On the basis of Sigelment and Reid, the normalized model of the relationship between the backscattering energy change of a single scatterer and the temperature change is calculated [1-5], such as formula (1-1):

where 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 equation (1-2):

CBE=η(T)/η(37) (1-2)

Tsui P H et al. found that the relationship between backscattered energy and temperature can also be obtained by canceling the displacement compensation of the original data, with higher sensitivity and more time saving [6].

On the basis of the above theory, Xia Jingjing et al. proposed a method of integrating ultrasonic backscatter energy (ICBE) and sliding window to obtain the temperature distribution image of the heating area. Instead, the temperature distribution is displayed along with the positive backscattered energy. The integrated backscattered energy value in each window of the sliding window:

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

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 ImagingWithout Echo Shift Compensation for Temperature Estimation, Ultrasonics, 2012, 52:925–935.

SUMMARY OF THE INVENTION

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

1. an ultrasonic radio frequency ablation temperature imaging device based on ultrasonic backscattered energy, comprising an ultrasonic probe, a bandpass filter module, a temperature imaging module, and a display module, wherein,

Ultrasonic probe, used to detect the ultrasonic backscattered signal, that is, the initial data;

Band-pass filtering module for band-pass filtering the initial data to reduce noise;

The temperature imaging module is used to complete the following functions:

(1) Obtain the envelope of the initial data;

(2) Through the sliding window, when calculating in each window, use step (1) to obtain the square of the envelope to obtain the energy at this moment, divide by the square of the envelope at the reference temperature, and only keep the positive backscattered energy at this time , remove the negative backscattered energy, that is, get the matrix of positive ultrasonic backscattered energy;

(3) Interpolate to the original image size;

The display module is used for combining the original images after interpolation at different times by the temperature imaging module to remove part of the noise, and display the result.

The beneficial effects of the present invention are as follows:

1. When the integrated ultrasonic backscattered energy is used for radiofrequency ablation, serious artifacts will be produced under the cautery needle. Using the backscattered energy of normal ultrasound 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 value and temperature is also better than that of comprehensive ultrasonic backscattered energy. Therefore, the use of positive 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.

2 is a comparison diagram of the normal ultrasonic backscattering energy method and the comprehensive ultrasonic backscattering energy method and temperature curves respectively.

Detailed ways

The ultrasonic radiofrequency ablation temperature imaging method based on the ultrasonic backscattering energy of the present invention utilizes the positive ultrasonic backscattering energy (PCBE) method to solve the artifact problem of the temperature distribution image presented in real time during the radiofrequency ablation process improvement, and the value of the backscattered energy of the positive ultrasonic wave is more in line with the curve of the temperature value.

In the process of temperature monitoring, only the positive backscattered energy part is retained, 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, the artifact under the burning needle can be effectively improved, and the value of the backscattered energy value of the positive ultrasonic wave is more in line with the temperature curve than the value of the backscattered energy value of the comprehensive ultrasonic wave.

Specific steps are as follows:

1) Using the ultrasonic probe to obtain the detected ultrasonic backscattered signal, that is, the initial data;

2) Band-pass filtering the initial data to reduce noise

3) Find the envelope of the initial data

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

5) Interpolate to the original image size

6) Combine images at different times to remove some noise and display

7) Circle the region of interest, and average the part of the matrix obtained in step 4) in the region of interest to obtain the forward and backscattered energy value in the region of interest. The subsequent calculation of ablation area, etc. can also be performed

Examples are as follows:

A properly sized pork loin was placed in an acrylic box, and a radiofrequency cautery needle was inserted into the inside of the loin through a small hole in the box. The cautery needle was circulated with water, and the temperature was monitored with a thermocouple. Use the ultrasonic probe to find the cut surface of the needle tip, and cauterize in 50W mode. An initial data sheet was recorded every two seconds, and the heating was continued for 12 min.

Process the obtained data: filter each piece of data based on the center frequency of the ultrasonic probe used in the experiment to remove noise outside the bandwidth; perform Hilbert transform on the noise-removed data to obtain the signal envelope; Divide into many windows of the same size, and obtain the backscattered energy value of the positive ultrasonic wave in each window; interpolate the obtained matrix to become the original image size; combine the data at different times to eliminate part of the noise; correct the normal ultrasonic wave The backscattered energy temperature distribution image is displayed, and on this basis, the average value of the normal 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 temperature monitoring of radiofrequency ablation.

Claims (1)

1. An ultrasonic radio frequency ablation temperature imaging device based on ultrasonic back scattering energy comprises an ultrasonic probe, a band-pass filtering module, a temperature imaging module and a display module, wherein,

an ultrasonic probe for detecting an ultrasonic backscatter signal, i.e., initial data;

the band-pass filtering module is used for performing band-pass filtering on the initial data to reduce noise;

the temperature imaging module is used for completing the following functions:

(1) obtaining an envelope of the initial data;

(2) through sliding windows, when calculating in each window, obtaining the energy of the window at the moment by the square of the envelope obtained in the step (1), dividing the energy by the square of the envelope at the reference temperature, only keeping positive backscatter energy at the moment, and removing negative backscatter energy to obtain a matrix of the positive ultrasonic backscatter energy;

(3) interpolating to obtain the size of the original image;

and the display module is used for combining the original images subjected to interpolation at different moments by the temperature imaging module to remove part of noise and displaying the combined original images.

Images