System and method for removing background noise from photoacoustic image

Patent metadata

Field	Value
Publication number	US-2018125373-A1
Application number	US-201715802735-A
Country	US
Kind code	A1
Filing date	Nov 3, 2017
Priority date	Nov 4, 2016
Publication date	May 10, 2018
Grant date	—

Abstract

Disclosed is a method of removing a background noise from a photoacoustic image, the method including applying an ultrasonic signal to a target absorbing body having a multi-modal microbubble contrast agent injected thereinto and receiving the ultrasonic signal reflected by the target absorbing body in order to acquire an ultrasonic image, when a photoacoustic signal is generated from the target absorbing body having the multi-modal microbubble contrast agent injected thereinto as the result of absorbing a laser pulse applied to the target absorbing body, receiving the photoacoustic signal in order to acquire a photoacoustic image, applying a critical value to pixels corresponding to microbubbles in the ultrasonic image in order to generate a mask image, and removing a background noise generated from a non-target absorbing body, while maintaining the target absorbing body, from the photoacoustic image using the mask image.

First claim

1 . A method of removing a background noise from a photoacoustic image, the method comprising:
applying an ultrasonic signal to a target absorbing body having a multi-modal microbubble contrast agent injected thereinto and receiving the ultrasonic signal reflected by the target absorbing body in order to acquire an ultrasonic image; when a photoacoustic signal is generated from the target absorbing body having the multi-modal microbubble contrast agent injected thereinto as a result of absorbing a laser pulse applied to the target absorbing body, receiving the photoacoustic signal in order to acquire a photoacoustic image; applying a critical value to pixels corresponding to microbubbles in the ultrasonic image in order to generate a mask image; and removing a background noise generated from a non-target absorbing body, while maintaining the target absorbing body, from the photoacoustic image using the mask image.

2 . The method according to claim 1 , further comprising, before the step of generating the mask image, improving a signal-to-noise ratio (SNR) and a contrast-to-noise ratio (CNR) through signal processing performed to increase an intensity of the ultrasonic signal generated by the multi-modal microbubble contrast agent such that the intensity of the ultrasonic signal is higher than an intensity of a photoacoustic signal generated from the non-target absorbing body and from a background of the target absorbing body.

3 . The method according to claim 2 , wherein the step of increasing the intensity of the ultrasonic signal comprises tracking the ultrasonic signal applied to the target absorbing body using at least one selected from among a pulse inversion image, an image using a coded excitation technique using at least one selected from among chirp, Golay code, and Barker code, and a harmonic image.

4 . The method according to claim 1 , wherein the step of generating the mask image comprises masking a region that is larger than a position of the microbubbles generated from the multi-modal microbubble contrast agent injected into the target absorbing body in order to prevent a loss of the photoacoustic signal.

5 . The method according to claim 1 , wherein the step of applying the critical value to the ultrasonic image in order to generate the mask image comprises binarizing the ultrasonic image into 1 or 0 based on a predetermined threshold in order to generate the mask image and masking the photoacoustic image using the generated mask image.

6 . The method according to claim 5 , wherein the step of removing the background noise from the photoacoustic image comprises multiplying the photoacoustic image by the mask image in order to acquire a photoacoustic image from which the background noise has been removed.

7 . The method according to claim 1 , wherein the step of generating the mask image comprises repeating the receiving the ultrasonic image, acquiring a plurality of frame images of the target absorbing body from ultrasonic images received over time, and accumulating phase-shifted signals of the microbubbles generated in N frame images beginning with a first frame image, among the acquired frame images, in order to acquire an ultrasonic image.

8 . A computer-readable recording medium having a program for allowing a computer to execute the method according to claim 1 recorded therein.

9 . A system for removing a background noise from a photoacoustic image, the system comprising:
a probe for sequentially emitting an ultrasonic signal and a laser pulse to a target absorbing body having a multi-modal microbubble contrast agent injected thereinto and receiving an ultrasonic signal and a photoacoustic signal generated by the target absorbing body; an original image acquisition unit for acquiring an ultrasonic image and a photoacoustic image from the ultrasonic signal and the photoacoustic signal received by the probe; a mask image generation unit for applying a critical value to pixels of microbubbles in the ultrasonic image in order to generate a mask image; a noise removal unit for removing a background noise from the photoacoustic image using the mask image; and a display unit for displaying the photoacoustic image from which the background noise has been removed.

10 . The system according to claim 9 , wherein the mask image generation unit improves a signal-to-noise ratio (SNR) and a contrast-to-noise ratio (CNR) through signal processing performed to increase an intensity of the ultrasonic signal generated by the multi-modal microbubble contrast agent such that the intensity of the ultrasonic signal is higher than an intensity of a photoacoustic signal generated from a non-target absorbing body and from a background of the target absorbing body, before generating the mask image.

11 . The system according to claim 9 , wherein the mask image generation unit tracks the ultrasonic signal applied to the target absorbing body using at least one selected from among a pulse inversion image, an image using a coded excitation technique using at least one selected from among chirp, Golay code, and Barker code, and a harmonic image in order to increase the intensity of the ultrasonic signal.

12 . The system according to claim 9 , wherein the mask image generation unit masks a region that is larger than a position of microbubbles generated from the multi-modal microbubble contrast agent injected into the target absorbing body in order to prevent a loss of the photoacoustic signal.

13 . The system according to claim 9 , wherein the mask image generation unit binarizes the ultrasonic image into 1 or 0 based on a predetermined threshold in order to generate the mask image and masks the photoacoustic image using the generated mask image.

14 . The system according to claim 13 , wherein the noise removal unit multiplies the photoacoustic image by the mask image in order to acquire a photoacoustic image from which the background noise has been removed.

15 . The system according to claim 9 , wherein the mask image generation unit repeats a process of receiving the ultrasonic image, acquires a plurality of frame images of the target absorbing body from ultrasonic images received over time, and accumulates phase-shifted signals of the microbubbles generated in N frame images beginning with a first frame image, among the acquired frame images, in order to acquire a pixel-wise displacement ultrasonic image.

Assignees

• Univ Sogang Res Foundation

Inventors

• Chang Jin Ho
• Kim Heamin

Classifications

• A61B5/0095 Primary

  by applying light and detecting acoustic waves, i.e. photoacoustic measurements · CPC title

• G06T2207/10132

  Ultrasound image · CPC title

• A61B8/481

  involving the use of contrast agents, e.g. microbubbles introduced into the bloodstream · CPC title

• G06T5/002

  Physics · mapped topic

• A61B5/7203

  for noise prevention, reduction or removal · CPC title