BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoacoustic image generation apparatus, a photoacoustic image generation method, and a recording media storing non-transitory computer readable photoacoustic image generation program that detect photoacoustic waves generated in a subject irradiated with light and generate a photoacoustic image.

2. Description of the Related Art

In recent years, photoacoustic imaging has been known which captures the image of the inside of a living body using a photoacoustic effect. In general, in the photoacoustic imaging, the inside of the living body is irradiated with pulsed laser light. In the inside of the living body, a living body tissue absorbs the energy of the pulsed laser light and ultrasonic waves (photoacoustic waves) are generated by adiabatic expansion caused by the energy. For example, an ultrasound probe detects the photoacoustic waves and a photoacoustic image is formed on the basis of a detection signal. In this way, it is possible to visualize the inside of the living body on the basis of the photoacoustic waves.

Here, in a case in which a photoacoustic image is generated in the photoacoustic imaging, a reconstruction process is performed for the detection signal detected by the ultrasound probe. A frequency domain reconstruction process, such as a reconstruction process using a Fourier transform algorithm (FTA) method, or a time domain reconstruction process, such as a reconstruction process using a delay-and-sum (DnS) method, has been proposed as the reconstruction process (for example, see JP2010-035806A). In a case in which the reconstruction process using the FTA method is compared to the reconstruction process using the DnS method, the amount of calculation in the reconstruction process using the FTA method is less than that in the reconstruction process using the DnS method and the quality of a photoacoustic image in the reconstruction process using the FTA method is higher than that in the reconstruction process using the DnS method. The reconstruction process using the FTA method uses the dispersion relation of photoacoustic waves in a frequency space to simply connect a time frequency space and a spatial frequency space. Therefore, the detected time-space information can be converted into real-space information by a simple arithmetic process.

SUMMARY OF THE INVENTION

However, an arithmetic process of the reconstruction process using the FTA method is performed for a detection signal of a probe in which detection elements are arranged by a rectangular coordinate system such as a linear probe. Therefore, it is difficult to use the arithmetic process of the reconstruction process using the FTA method for a detection signal of a probe in which detection elements are arranged by coordinate systems other than the rectangular coordinate system, such as a convex probe, without any change. Even in a case in which the arithmetic process is changed, the arithmetic process becomes very complicated and the amount of calculation increases, which makes it difficult to perform the reconstruction process at a high speed.

The invention has been made in view of the above-mentioned problems and an object of the invention is to provide a photoacoustic image generation apparatus, a photoacoustic image generation method, and a recording media storing non-transitory computer readable photoacoustic image generation program that can perform a more appropriate reconstruction process regardless of the type of probe, without causing a reduction in the speed of an arithmetic process.

According to an aspect of the invention, there is provided a photoacoustic image generation apparatus comprising: a probe that detects photoacoustic waves generated in a subject irradiated with light and outputs a photoacoustic wave detection signal; a probe identification unit that identifies whether the probe is a probe in which detection elements are arranged by a coordinate system using polar coordinates or a probe in which detection elements are arranged by a rectangular coordinate system; and a photoacoustic image generation unit that performs a time domain reconstruction process or a frequency domain reconstruction process, using the photoacoustic wave detection signal, to generate a photoacoustic image. In a case in which the probe is identified as the probe in which the detection elements are arranged by the coordinate system using the polar coordinates, the photoacoustic image generation unit selects the time domain reconstruction process and generates the photoacoustic image.

In the photoacoustic image generation apparatus according to the aspect of the invention, the probe identification unit may identify at least one of a convex probe, a micro-convex probe, or a radial scanning probe as the probe in which the detection elements are arranged by the coordinate system using the polar coordinates.

In the photoacoustic image generation apparatus according to the aspect of the invention, in a case in which the probe is identified as the probe in which the detection elements are arranged by the rectangular coordinate system, the photoacoustic image generation unit may select the frequency domain reconstruction process and generate the photoacoustic image.

The photoacoustic image generation apparatus according to the aspect of the invention may further comprise a reconstruction process selection receiving unit that receives a selection of one of the time domain reconstruction process and the frequency domain reconstruction process in a case in which the probe is identified as the probe in which the detection elements are arranged by the rectangular coordinate system. The photoacoustic image generation unit may generate the photoacoustic image using the reconstruction process received by the reconstruction process selection receiving unit.

In the photoacoustic image generation apparatus according to the aspect of the invention, the probe identification unit may identify at least one of a linear probe or a sector probe as the probe in which the detection elements are arranged by the rectangular coordinate system.

In the photoacoustic image generation apparatus according to the aspect of the invention, the time domain reconstruction process may be a reconstruction process using a delay-and-sum (DnS) method.

In the photoacoustic image generation apparatus according to the aspect of the invention, the time domain reconstruction process may be a reconstruction process using a convolution back projection (CBP) method.

In the photoacoustic image generation apparatus according to the aspect of the invention, the frequency domain reconstruction process may be a reconstruction process using a Fourier transform algorithm (FTA) method.

In the photoacoustic image generation apparatus according to the aspect of the invention, the probe may detect reflected waves of acoustic waves transmitted to the subject and output a reflected wave detection signal. The photoacoustic image generation apparatus may further comprise a reflected wave image generation unit that performs the reconstruction process using the delay-and-sum (DnS) method on the basis of the reflected wave detection signal to generate a reflected wave image.

In the photoacoustic image generation apparatus according to the aspect of the invention, the reflected wave image generation unit may implement a process of generating the reflected wave image using hardware and the photoacoustic image generation unit may implement a process of generating the photoacoustic image using software.

In the photoacoustic image generation apparatus according to the aspect of the invention, the photoacoustic image generation unit may implement the time domain reconstruction process using hardware and may implement the frequency domain reconstruction process using software.

According to another aspect of the invention, there is provided a photoacoustic image generation method that performs a time domain reconstruction process or a frequency domain reconstruction process, using a photoacoustic wave detection signal obtained by detecting photoacoustic waves generated in a subject irradiated with light, to generate a photoacoustic image. The photoacoustic image generation method comprises: identifying whether a probe that detects the photoacoustic waves and outputs the photoacoustic wave detection signal is a probe in which detection elements are arranged by a coordinate system using polar coordinates or a probe in which detection elements are arranged by a rectangular coordinate system; and selecting the time domain reconstruction process and generating the photoacoustic image in a case in which the probe is identified as the probe in which the detection elements are arranged by the coordinate system using the polar coordinates.

According to still another aspect of the invention, there is provided a recording media storing non-transitory computer readable photoacoustic image generation program that causes a computer to function as: a photoacoustic image generation unit that performs a time domain reconstruction process or a frequency domain reconstruction process, using a photoacoustic wave detection signal obtained by detecting photoacoustic waves generated in a subject irradiated with light, to generate a photoacoustic image; and a probe identification unit that identifies whether the probe is a probe in which detection elements are arranged by a coordinate system using polar coordinates or a probe in which detection elements are arranged by a rectangular coordinate system. The photoacoustic image generation unit selects the time domain reconstruction process and generates the photoacoustic image in a case in which the probe is identified as the probe in which the detection elements are arranged by the coordinate system using the polar coordinates.

According to the photoacoustic image generation apparatus, the photoacoustic image generation method, and the recording media storing non-transitory computer readable photoacoustic image generation program of the invention, it is identified whether the probe that detects the photoacoustic waves and outputs the photoacoustic wave detection signal is a probe in which detection elements are arranged by a coordinate system using polar coordinates or a probe in which detection elements are arranged by a rectangular coordinate system. In a case in which the probe is identified as the probe in which the detection elements are arranged by the coordinate system using the polar coordinates, the time domain reconstruction process is selected and the photoacoustic image is generated. Therefore, it is possible to perform a more appropriate reconstruction process regardless of the type of probe, without causing a reduction in the speed of an arithmetic process.

