Laser Ultrasonic and Optoacoustic Tomography of Biological Objects

A multichannel combined laser ultrasound (LU) and optoacoustic (OA) tomograph working in real time mode was created in the laboratory. These techniques are based on the optoacoustic effect. Both methods are based on recording acoustic waves. However, the OA technique is based on the absorption, while the LU method is based on the scattering. In addition, LU method based on acoustic contrast of tissues (the difference of impedances of various types of tissues), but OA method is based on optical contrast of tissues (various optical properties, primarily absorption of light). In OA tomography, ultrasonic signals are generated directly in the investigated object, whereas in the LU technique ultrasonic signals are often obtained with the help of a special medium with known optical, thermal and acoustic parameters (OA generator).

The problem of inserting a needle into a blood vessel (for monitoring the position of insertion of the tip of the needle and preventing puncture of the vessel) using a combined 2D OA and LU tomography in real time (frame rate 10 Hz) was investigated.

OA tomography is well suited for imaging tasks of an object that has an increased coefficient of light absorption in relation to the environment. Such tasks include, for example, the visualization of blood vessels, since blood is the main chromophore in the near-IR range. The increased content of blood vessels is typical for malignant tumors.

Below the results of clinical trials are presented. The patient was examined using X-ray, ultrasonography and biopsy samples were taken. OA diagnostics was carried out after making a decision about mastectomy.

The X-ray image has two suspicious areas, only one of them corresponds to malignant tumor (revealed as a result of pathological examination after mastectomy). The position of the tumors that were detected with OA tomography corresponded to that of the X-ray and ultrasonic images, as well as the pathological examination after mastectomy. In addition to the position of the tumor OA tomography also distinguishes its heterogeneous internal structure.