CN105232004A - Opto-acoustic-ultrasonic united imaging device and imaging method for precisely measuring thickness of melanoma - Google Patents

Abstract

The invention relates to a combined photoacoustic and ultrasonic imaging device for accurately measuring the thickness of melanoma, including a computer control and imaging system, a laser emitting system, a delay module, an FPGA control and signal processing system, a digital-to-analog converter, an ultrasonic receiving/emitting unit, Handheld dual-mode integrated detector; the pulse trigger of the laser emission system is divided into two channels, one is directly in contact with the FPGA control and signal processing system for light-emitting and acoustic signal acquisition, and the other is in contact with the FPGA control and signal processing system through the delay module Ultrasound signal acquisition is used to accurately measure the thickness of melanoma through the generated photoacoustic image and ultrasound image. The invention also relates to a combined photoacoustic and ultrasonic imaging method for accurately measuring the thickness of melanoma. The invention can accurately measure the thickness of melanoma in different stages in a non-destructive manner, has a small size, provides possibility for rapid clinical detection, and belongs to the technical field of photoacoustic and ultrasonic imaging measurement.

Description

A photoacoustic ultrasound combined imaging device and imaging method for accurately measuring the thickness of melanoma

technical field

The invention relates to a technique for measuring the thickness of melanoma by means of photoacoustic and ultrasonic imaging, in particular to a combined photoacoustic and ultrasonic imaging device and imaging method for accurately measuring the thickness of melanoma.

Background technique

Melanoma thickness is an important criterion for judging the five-year survival rate after surgery. Increased thickness of melanoma invasion (Clark grade) was associated with poorer prognosis. Histological judgment Treatment and prognosis are mainly determined by microscopic observation of the depth of invasion in melanoma histology. Histological grading requires an adequate biopsy. However, biopsy can be painful and scarring for the patient, and damaging excision may lead to further malignancy. At this stage, the main method for non-destructive measurement of melanoma thickness is ultrasound imaging. Currently, high-frequency ultrasound is commonly used for melanoma measurement. The main frequency is generally 15-20Mhz. For melanoma less than 1.5mm, especially less than 0.75mm, the statistical error of thickness is relatively large.

Photoacoustic imaging is a non-destructive medical imaging technology. It is based on the photoacoustic effect and uses short-pulse laser light (light signal) on the order of nanoseconds to irradiate biological tissue. After the short-pulse laser is absorbed by the biological tissue, it causes rapid thermoelastic expansion. Mechanical waves are generated, whereby ultrasonic waves (photoacoustic signals) are generated. The ultrasonic probe receives the generated ultrasonic waves and back-projects them through a certain algorithm to obtain the light absorption distribution in the tissue. Photoacoustic imaging is imaging based on tissue absorption. Although the acoustic impedance of early melanoma is not much different from that of surrounding tissues, it contains a large amount of melanin, so high-contrast and high-resolution photoacoustic results can be obtained. However, the imaging depth of melanoma by photoacoustic imaging is limited. Therefore, by combining photoacoustic and ultrasonic imaging, the thickness of melanoma at different stages can be obtained. At the same time, the acoustic impedance of the epidermis and the coupling agent are quite different, which can be clearly presented by ultrasonic imaging. , thereby improving the accuracy of melanoma infiltration depth detection.

Contents of the invention

In view of the technical problems existing in the prior art, the object of the present invention is to provide a combined photoacoustic ultrasound imaging device and imaging method for accurately measuring the thickness of melanoma, which can rapidly and accurately measure the thickness of melanoma in different stages in real time.

In order to achieve the above object, the present invention adopts following technical scheme:

A combined photoacoustic and ultrasonic imaging device for accurately measuring the thickness of melanoma, including: computer control and imaging system, laser emission system, delay module, FPGA control and signal processing system, digital-to-analog converter, ultrasonic receiving/transmitting unit, handheld dual-mode integrated detector; the computer control and imaging system are connected with the laser emission system; the pulse trigger of the laser emission system is divided into two paths, one path is directly connected with the FPGA control and signal processing The timing module is connected with the FPGA control and signal processing system to trigger ultrasonic signal acquisition; along the signal flow direction, FPGA control and signal processing system, ultrasonic receiving/transmitting unit, handheld dual-mode integrated detector, ultrasonic receiving/transmitting unit, The digital-to-analog converter, FPGA control and signal processing system, computer control and imaging system are set up in sequence.

The computer control and imaging system controls the operation of the laser emission system, controls the opening and closing of the delay module, receives photoacoustic/ultrasonic signals, and realizes real-time imaging; the laser emission system emits laser light; the delay module delays the laser for ultrasonic imaging mode; FPGA The control and signal processing system controls the ultrasonic receiving/transmitting unit to transmit and receive signals and returns the photoacoustic/ultrasonic signal to the computer control and imaging system after processing; the ultrasonic receiving/transmitting unit only receives signals in the photoacoustic imaging mode, Transmit and receive signals; the handheld dual-mode integrated detector is in contact with the skin, transmits signals to the skin and receives the signal reflected by the skin.

The handheld dual-mode integrated detector includes: a housing and an optical fiber bundle sequentially arranged in the housing, a line collimating lens, a line focusing lens, and an ultrasonic detector array; the ultrasonic receiving/transmitting unit is connected to the optical fiber bundle; the ultrasonic detector array Receive the signal reflected by the skin and transmit the signal to the ultrasonic receiving/transmitting unit.

The fiber bundle includes n optical fibers, the ultrasonic probe array includes n sets of array elements, the ultrasonic receiving/transmitting unit includes n sets of receiving/transmitting circuits, and one optical fiber and a group of array elements are connected to a set of receiving/transmitting circuits; n A group of receiving/transmitting circuits are connected in parallel to the FPGA control and signal processing system; where n is a positive integer.

The optical fiber bundle is a multimode optical fiber in which multiple optical fibers are arranged in a linear structure.

There are multiple groups of array elements; each group has two array elements, which are symmetrically arranged on both sides of the signal irradiating the skin; multiple array element elements on the same side are arranged in a row.

Each element sheet is at an angle of 5 degrees to 10 degrees with the skin surface; two array elements in the same group form a figure-eight shape, and the large opening of the figure-eight shape faces the skin.

The shape of the line focusing lens is a strip shape, the convex side is downward, and the focal length is 22-30 mm.

A photoacoustic ultrasound combined imaging method for accurately measuring the thickness of melanoma, using a photoacoustic ultrasound combined imaging device for accurately measuring the thickness of melanoma, comprising the following steps:

a. The computer control and imaging system controls the operation of the laser emission system. The laser emission system emits laser light and provides trigger signals for photoacoustic imaging and ultrasonic imaging. One trigger signal directly triggers photoacoustic signal acquisition, that is, step b, and the other trigger signal The ultrasonic signal acquisition is triggered by the delay module, that is, step c, to realize step-by-step triggering of photoacoustic imaging and ultrasonic imaging at the same acquisition site;

b. The laser passes through the FPGA control and signal processing system, the signal is amplified by the ultrasonic receiving/transmitting unit, and then irradiates the skin through the handheld dual-mode integrated detector, and the ultrasonic detector array of the handheld dual-mode integrated detector receives the skin reflection The photoacoustic signal returns the photoacoustic signal to the ultrasonic receiving/transmitting unit into an electrical signal, and the electrical signal reaches the computer control and imaging system after the digital-to-analog converter, FPGA control and signal processing system; the FPGA control and signal processing system is in the In the photoacoustic imaging mode, the photoacoustic signal is collected by the ultrasonic receiving/transmitting unit for photoacoustic imaging reconstruction, and the ultrasonic receiving/transmitting unit only works in the receiving mode;

c. The laser passes through the delay module and FPGA control and signal processing system to excite the ultrasonic receiving/transmitting unit to transmit signals, and the signal excites the handheld dual-mode integrated detector to generate ultrasonic signals to irradiate the skin, and the handheld dual-mode integrated detector performs ultrasonic detection The sensor array receives the ultrasonic signal reflected by the skin, returns the ultrasonic signal to the ultrasonic receiving/transmitting unit and turns it into an electrical signal, and the electrical signal reaches the computer control and imaging system after passing through the digital-to-analog converter, FPGA control and signal processing system; And when the control switch of the signal processing system selects the ultrasonic imaging mode, the FPGA control and signal processing system controls the ultrasonic receiving/transmitting unit to transmit ultrasonic signals and collect ultrasonic signals for ultrasonic imaging reconstruction, and the ultrasonic receiving/transmitting unit works in receiving/transmitting model;

d. The computer control and imaging system includes a dual-mode imaging mode including photoacoustic imaging and ultrasonic imaging, generates photoacoustic images and ultrasonic images, and provides melanoma thickness test results through two images.

In step d, the position of the epidermis is indicated by the ultrasound image, and the position of the upper surface of the melanoma is indicated by the photoacoustic image: when the distance between the signal on the lower surface of melanoma measured by the photoacoustic signal and the signal on the upper surface is greater than 1.5mm, or the signal signal on the lower surface of the photoacoustic signal When the noise ratio is less than 6db, the position of the lower surface of the melanoma is indicated by the ultrasound image, otherwise, the position of the lower surface of the melanoma is indicated by the photoacoustic image.

Generally speaking, the present invention has following advantages:

1. The thickness of melanoma in different stages can be accurately measured in a non-destructive way.

2. It adopts a handheld dual-mode integrated detector with a small size, which provides the possibility for rapid clinical detection.

3. Photoacoustic and ultrasonic dual-mode imaging mode, simultaneously obtain the optical properties and acoustic impedance information of the tissue.

4. Using a line focusing lens to linearly focus the light spot and an ultrasonic detector array, it is faster than a single focusing light spot and a single array element detector, and can perform real-time and fast dual-mode imaging.

5. The array elements are inclined to the skin, and the detection sensitivity is improved through physical focusing.

Description of drawings

Figure 1 is a schematic block diagram of a photoacoustic ultrasound combined imaging device for accurately measuring the thickness of melanoma.

Fig. 2 is a schematic structural diagram of a handheld dual-mode integrated detector.

Fig. 3 is a schematic diagram of light and sound transmission of the handheld dual-mode integrated detector.

Fig. 4a is an ultrasound imaging image of Embodiment 1.

Fig. 4b is a photoacoustic imaging image of Example 1.

1 is computer control and imaging system, 2 is laser emission system, 3 is delay module, 4 is FPGA control and signal processing system, 5 is ultrasonic receiving/transmitting unit, 6 is handheld dual-mode integrated detector, 7 is Digital-to-analog converter. 5-1, 5-2, ..., 5-64 are receiving/transmitting circuits. 6-1, 6-2, ..., 6-64 are array element slices of each group.

61 is an optical fiber bundle, 62 is a line collimating lens, 63 is a line focusing lens, 64 is a focused light beam, and 65 is an ultrasonic detector array.

11 indicates the simulated skin surface, 12 indicates the upper surface of simulated melanoma, 13 indicates the lower surface of simulated melanoma marker with thickness less than 1.5 mm, and 14 indicates the lower surface of simulated melanoma marker with thickness greater than 1.5 mm.

detailed description

The present invention will be described in further detail below.

A combined photoacoustic and ultrasonic imaging device for accurately measuring the thickness of melanoma, including: computer control and imaging system, laser emission system, delay module, FPGA control and signal processing system, digital-to-analog converter, ultrasonic receiving/transmitting unit, handheld Dual-mode integrated detector. A combined photoacoustic and ultrasonic imaging device for accurately measuring the thickness of melanoma is formed by rearranging and connecting existing systems or modules. The connection method is as follows: the computer control and imaging system are connected with the laser emitting system; , one way is directly in contact with the FPGA control and signal processing system for the acquisition of luminescent and acoustic signals, and the other way is connected with the FPGA control and signal processing system through the delay module to trigger ultrasonic signal acquisition; along the flow direction of the signal, the FPGA control and signal processing system, Ultrasonic receiving/transmitting unit, hand-held dual-mode integrated detector, ultrasonic receiving/transmitting unit, digital-to-analog converter, FPGA control and signal processing system, computer control and imaging system are arranged in sequence. The handheld dual-mode integrated detector is made by rearranging and connecting the existing parts.

The computer control and imaging system controls the operation of the laser emission system, controls the opening and closing of the delay module, receives photoacoustic/ultrasonic signals, and realizes real-time imaging. The computer control and imaging system includes a dual-mode imaging mode including photoacoustic imaging and ultrasonic imaging, generates photoacoustic images and ultrasonic images, and provides melanoma thickness test results through two images.

The laser emitting system is used to generate laser light, including laser, laser shaping filter element and fiber coupling device. The pulsed laser output from the laser is coupled into the fiber array by the fiber coupling device through the laser shaping filter element. The optical fiber array includes optical fiber bundles arranged in a rectangular array.

The delay module is based on a delay circuit composed of a 555 chip, which is used to delay the external trigger generated by the laser, and the external trigger triggers the emission and collection of ultrasonic signals through the delay.

FPGA control and signal processing system includes signal conditioning and acquisition module, DRAM, Flash (flash memory), PXIe controller and FPGA controller. Among them, the FPGA controller controls the ultrasonic receiving/transmitting unit to transmit and receive ultrasonic signals, and the signal conditioning and acquisition module converts the input analog signal into a serial digital signal and then inputs it to the FIFO module through the bus, and the FIFO module transmits the signal to the main control unit , and store the result in internal RAM. FPGA control and signal processing system is existing equipment, and it is a kind of development board, can realize required function by writing program above, the function that FPGA control among the present invention and signal processing system reach is existing.

The digital-to-analog converter is used for signal conversion, which is convenient for computer control and imaging systems to receive signals.

The ultrasonic receiving/transmitting unit includes 64 channels of receiving/transmitting circuits connected in parallel to the FPGA control and signal processing system. In the photoacoustic imaging mode, the receiving/transmitting circuit only receives signals and is used as a circuit for amplifying circuit signals. In the ultrasonic imaging mode, the 64-channel receiving/transmitting circuit stimulates the handheld dual-mode integrated detector to generate and receive ultrasonic signals.

The handheld dual-mode integrated detector includes an optical fiber bundle, a line collimating lens, a line focusing lens, an ultrasonic detector array, and a housing. In the housing, fiber bundles, line collimating lenses, line focusing lenses, and ultrasonic detector arrays are arranged in sequence. Among them, the optical fiber bundle includes 64 optical fibers, and the ultrasonic detector array includes 64 sets of array elements, and one optical fiber and a set of array elements are correspondingly connected to a set of receiving/transmitting circuits. The optical fiber bundle is a multimode optical fiber with 64 optical fibers arranged in a rectangular array. The line collimating lens is used to collimate the laser light emitted from the fiber bundle. The line focus lens is used to focus the collimated laser beam into a linear light source. The shape of the line focus lens is a long strip, with the convex side facing down, and the focal length is 22-30mm. The number of array element slices is 64 groups; the number of array element slices in each group is two, which are symmetrically arranged on both sides of the signal irradiating the skin; multiple array element slices on the same side are arranged in a row. Each array element is at an angle of 5° to 10° to the skin surface; two array elements in the same group are symmetrically arranged in a figure-eight shape, and the large opening of the figure-eight shape faces the skin, so that the signals reflected by the skin can be gathered and collected. The working process is as follows: the laser is introduced through the optical fiber bundle, and the laser emitted from the optical fiber bundle is collimated by the line collimating lens. The signal received at this time is used for the reconstruction of the photoacoustic image; after a period of delay, the ultrasonic detector array emits and receives the ultrasound, and the signal received at this time is used for the reconstruction of the ultrasonic signal. As shown in Figure 3, the focused beam irradiates the tissue surface, where the optical focus and the acoustic focus of the detector are on the same plane to improve the sensitivity of photoacoustic signal detection. The ultrasonic detector array is two rows of element slices placed symmetrically, and every two array element slices at symmetrical positions form a group, and each group of array element slices transmits and receives signals at the same time.

A combined photoacoustic and ultrasonic imaging method for accurately measuring the thickness of melanoma. The computer control and imaging system control the opening and closing of the laser emission system. The external trigger of the laser emission system (automatically selected by timing control) is divided into two channels, as shown in Figure 1. As shown in the dotted box on the right, the channel is selected by controlling the switch to trigger the acquisition of photoacoustic signals or ultrasonic signals. Among them, the external trigger directly triggers the FPGA control and signal processing system, that is, the switch shown in the figure selects the lower path, which triggers the photoacoustic signal acquisition; the external trigger passes through the delay module, that is, when the switch in the figure selects the upper path, the FPGA control is triggered. And the signal processing system is to trigger the ultrasonic signal acquisition. The FPGA control and signal processing system controls 64 receiving/transmitting circuits. In the photoacoustic mode, the receiving/transmitting circuit only receives photoacoustic signals and is used as a circuit for amplifying circuit signals; in the ultrasonic mode, the FPGA control and signal processing system controls 64 receiving/transmitting circuits stimulate the ultrasonic detector array to generate and receive ultrasonic signals. In both modes, the ultrasonic detector array receives the acoustic signal and converts the electrical signal through the digital-to-analog converter, receives it into the FPGA control and signal processing system for signal processing, and then transmits it to the computer control and imaging system. The computer control and imaging system receives the photoacoustic/ultrasonic signal and performs image reconstruction. The position of the epidermis is indicated by the ultrasonic image, and the position of the upper surface of the melanoma is indicated by the photoacoustic image; the indication of the position of the lower surface of the melanoma is divided into the following two situations : When the photoacoustic signal measured from the lower surface of the melanoma to the upper surface signal is greater than 1.5mm, or the signal-to-noise ratio of the lower surface signal of the photoacoustic signal is less than 6db, the position of the lower surface of the melanoma is indicated by the ultrasonic image; otherwise, the photoacoustic image Indicates the location of the subsurface of the melanoma.

The detection results are shown in Figure 4a and Figure 4b. The ultrasonic image indicates the position of the epidermis, the photoacoustic image indicates the position of the upper surface of the melanoma, and the indication of the position of the lower surface of the melanoma takes 1.5 mm as the index; when the system determines that the thickness of the melanoma is less than 1.5 mm (that is, the distance between the signal on the lower surface of the melanoma measured by the photoacoustic signal and the signal on the upper surface is less than 1.5 mm), the position of the lower surface of the melanoma is provided by photoacoustic imaging; When the signal-to-noise ratio is less than 6db, the position of the lower surface of the melanoma is indicated by ultrasound imaging.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. accurately measure a photoacoustic ultrasound joint imaging device for melanoma thickness, it is characterized in that: comprising: computer controls and imaging system, laser transmitting system, time delay module, FPGA control and signal processing system, digital to analog converter, ultrasonic reception/transmitter unit, the double-mode integrated detector of hand-held; Computer controls and imaging system connects with laser transmitting system; The pulse-triggered of laser transmitting system is divided into two-way, a road directly controls with FPGA and signal processing system contacts luminous acoustical signal collection, triggering ultrasonic signal acquisition that time delay module of separately leading up to controls with FPGA and signal processing system connects; Along the flow direction of signal, FPGA controls and signal processing system, ultrasonic reception/transmitter unit, the double-mode integrated detector of hand-held, ultrasonic reception/transmitter unit, digital to analog converter, FPGA control and signal processing system, computer control and imaging system set gradually.

2., according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 1, it is characterized in that: described in

Computer control and imaging system control the operation of laser transmitting system, control the keying of time delay module, receive optoacoustic/ultrasonic signal, realize realtime imaging;

Laser transmitting system Emission Lasers;

Laser postpones to be used for ultrasound imaging mode by time delay module;

FPGA controls and signal processing system controls ultrasonic reception/transmitter unit and launches and Received signal strength will return computer after optoacoustic/ultrasonic signal processing and control and imaging system;

Ultrasonic reception/transmitter unit only Received signal strength under photoacoustic imaging pattern, launches and Received signal strength under ultrasound imaging mode;

The double-mode integrated detector of hand-held and contact skin, transmit to skin and receive the signal of skin reflex.

3. according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 1, it is characterized in that: the double-mode integrated detector of described hand-held comprises: shell and the fibre bundle, line collimating lens, line focus lens, the ultrasonic detector array that are successively set in shell; Ultrasonic reception/transmitter unit connects with fibre bundle; The signal of ultrasonic detector array received skin reflex, transmits signals to ultrasonic reception/transmitter unit.

4. according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 3, it is characterized in that: described fibre bundle comprises n bar optical fiber, ultrasonic detector array comprises n group array element sheet, ultrasonic reception/transmitter unit comprises n group reception/radiating circuit, an optical fiber and one group of array element sheet correspondence access, one group of reception/radiating circuit; The access FPGA of n group reception/radiating circuit parallel connection controls and signal processing system; Wherein n gets positive integer.

5. according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 4, it is characterized in that: described fibre bundle is the multimode fibre of multifiber linearly arrangement architecture.

6., according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 4, it is characterized in that: the quantity of described array element sheet is many groups; The quantity often organizing array element sheet is two, the symmetrical both sides being arranged on the signal irradiating skin; Multiple array element sheets of the same side form a line.

7. according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 6, it is characterized in that: each array element sheet is all 5 degree to 10 degree angles with skin surface; Two array element sheets with group become splayed, and splay big uncork is towards skin.

8. according to a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to claim 3, it is characterized in that: the shape of described line focus lens is strip, convex surface is downward, and burnt length is 22-30 millimeter.

9. accurately measure a photoacoustic ultrasound joint imaging method for melanoma thickness, use a kind of photoacoustic ultrasound joint imaging device accurately measuring melanoma thickness according to any one of claim 1 to 8, it is characterized in that: comprise the steps:

A. computer control and imaging system control the operation of laser transmitting system, laser transmitting system Emission Lasers, simultaneously for photoacoustic imaging and ultra sonic imaging provide triggering signal, one tunnel triggering signal directly triggers photoacoustic signal collection, i.e. step b, another road triggering signal is through time delay module Triggered ultrasound signals collecting, i.e. step c, realizes photoacoustic imaging and the substep of ultra sonic imaging at same collection position triggers;

B. laser controls and signal processing system through FPGA, signal through ultrasonic reception/transmitter unit amplifies, skin is irradiated again by the double-mode integrated detector of hand-held, the photoacoustic signal of the ultrasonic detector array received skin reflex of the double-mode integrated detector of hand-held, photoacoustic signal is returned ultrasonic reception/transmitter unit and become the signal of telecommunication, the signal of telecommunication controls and arrives computer after signal processing system to control and imaging system through digital to analog converter, FPGA; Wherein FPGA control and signal processing system are under photoacoustic imaging pattern, and gather photoacoustic signal by ultrasonic reception/transmitter unit, be used for carrying out photoacoustic imaging restructuring, ultrasonic reception/transmitter unit only works in receiving mode;

C. laser to control and signal processing system excitation ultrasound reception/transmitter unit transmits through time delay module and FPGA, the double-mode integrated detector of signal excitation hand-held produces ultrasonic signal and irradiates skin, the ultrasonic signal of the ultrasonic detector array received skin reflex of the double-mode integrated detector of hand-held, ultrasonic signal is returned ultrasonic reception/transmitter unit and become the signal of telecommunication, the signal of telecommunication controls and arrives computer after signal processing system to control and imaging system through digital to analog converter, FPGA; Wherein, when FPGA control and signal processing system gauge tap select ultrasound imaging mode time, FPGA controls and signal processing system controls ultrasonic reception/transmitter unit transmitting ultrasonic signal and gathers ultrasonic signal, be used for carrying out ultra sonic imaging restructuring, ultrasonic reception/transmitter unit works in reception/emission mode;

D. computer control and imaging system comprise the double-mode imaging pattern containing photoacoustic imaging and ultra sonic imaging, generate photoacoustic image and ultrasonoscopy, are provided the test result of melanoma thickness by two width images.

10. according to a kind of photoacoustic ultrasound joint imaging method accurately measuring melanoma thickness according to claim 9, it is characterized in that: in steps d, epidermis position is indicated by ultrasonoscopy, melanoma upper surface position is indicated: measure melanoma lower surface signal distance upper surface signal when photoacoustic signal and be greater than 1.5mm by photoacoustic image, or photoacoustic signal lower surface Signal-to-Noise is when being less than 6db, melanoma lower surface position is indicated by ultrasonoscopy, otherwise, then melanoma lower surface position is indicated by photoacoustic image.