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Photoacoustic Tomography

PAT is imaging technology that can capture 3D images of blood vessels in real time.
We aim to contribute to healthcare with new diagnostic imaging equipment that combines cutting-edge optical technology, ultrasonic technology and image processing technology.

2018/12/27Featured Technology

Taking 3D Images of Blood Vessels

#Healthcare#Imaging technologies#Social contribution#Mechanical engineering#Electrical engineering#Computer science#Physics

As awareness of a healthy life expectancy increases, the early diagnosis of such lifestyle-related diseases as cancer and diabetes and treatment tailored to the individual are becoming increasingly important.

Canon is currently developing Photo-acoustic Tomography (PAT), a leading-edge technology to improve healthcare through the early diagnosis and appropriate treatment of diseases. This technology was selected as a research topic for ImPACT (the Impulsing PAradigm Change through disruptive Technologies program) being implemented by the Council of Science, Technology and Innovation of the Cabinet Office in Japan.

PAT is technology that uses both light and ultrasonic waves to noninvasively capture 3D images of human blood vessels in real time without using X-rays or a contrast agent. When the human body is exposed to near-infrared laser light, red corpuscles in blood vessels absorb laser light, heat up and undergo thermal expansion, increasing their volume. The laser light is transmitted in pulses, so the exposure is short-term, and the expanded red corpuscles in the blood vessels soon cool off and return to their normal state. The effects of the expansion and the contraction are transmitted to neighboring soft tissue and are emitted from the surface of the body in the form of ultrasonic signals that can be detected by an ultrasonic sensor. This is the mechanism of PAT.

The laser light has a wavelength of 750 nm to 850 nm (nm = nanometer, one billionth of a meter); a pulse width of laser light is several nano seconds and has a repetition frequency of about 10 Hz. The ultrasonic sensor has 1024 piezoelectric elements attached to its hemispherical inner surface.

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Recreating a 3D image in real time at Kyoto University

Making Blood Vessels Visible and Precisely Determining their Position

#Healthcare#Imaging technologies#Social contribution#Mechanical engineering#Electrical engineering#Computer science#Physics

The challenge is the high number of blood vessels in the human body that generate ultrasonic signals throughout the body. The ultrasonic signals are conveyed as they expand to surrounding areas, making it difficult to determine which ultrasonic signal originated from which blood vessel at what location. Canon uses the image processing technologies that we have cultivated through the development of various imaging devices to successfully recreate a 3D image in real time based on the received ultrasonic signals.

Among the features of PAT is the ability to capture images from a wide range of areas—such as the hands and feet—the ability to make blood vessels as small as 0.2 mm visible, and high resolution imaging that allows for the position of each blood vessel to be determined individually. In addition, blood vessels are made visible to a depth of several centimeters, something that is difficult to achieve using light alone.

Potential to Lead to Early Diagnosis and Appropriate Treatment

#Healthcare#Imaging technologies#Social contribution#Mechanical engineering#Electrical engineering#Computer science#Physics

The 3D images of blood vessels captured by PAT are giving rise to ideas for applications in the early diagnosis of diseases and assessment before and after treatment. For example, diseases of the blood vessels and skin and such diseases as cancer can lead to inadequate blood circulation in the periphery of the limbs, irregularities in the shape of blood vessels and abnormal blood vessel growth. If it is possible to detect these symptoms and recognize minute changes at an early stage, such applications as the early identification of disease status, selection of appropriate treatment and post-treatment evaluation may be made possible.

Joint Research with Kyoto University and Keio University

#Open innovation#Healthcare#Imaging technologies#Social contribution#Mechanical engineering#Electrical engineering#Computer science#Physics

PAT is also characterized by the ability to distinguish between arteries and veins using a number of wavelengths of laser light. When the laser light wavelength is shortened, the ultrasonic signals emitted from arteries, which contain more oxygen, decrease compared with veins. In addition, images that reflect the oxygen saturation of blood can be captured through the use of multiple laser lights of different wavelengths. Use of these features makes visible changes resulting from the progression of a disease or the effects of treatment, as well as the amount of oxygen consumption in tissue and the volume of blood circulating. This holds promise for such applications as the diagnosis of peripheral artery disease caused by lifestyle-related illnesses, as well as skin conditions and cancer.

Canon is conducting clinical research using PAT in collaboration with Kyoto University and Keio University. The research with Kyoto University has produced results in the capture of 3D images of blood vessels that concentrate in the vicinity of a cancer tumor. Further research is needed to determine the direct relationship between the 3D images and the disease, but the accumulation of this type of knowledge increases the likelihood of clinical applications of this technology.

PAT is noninvasive, nondestructive and does not require X-rays or a contrast agent; it causes absolutely no harm to the human body. Canon is conducting development with the hope that one day, PAT imaging devices will be installed in hospitals alongside X-ray, CT diagnostic systems and MRI scanners, and contribute to the early diagnosis of disease and the evaluation of treatment.

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The subject is exposed to laser light, which is absorbed by absorbers. These absorbers undergo thermal expansion and emit ultrasonic sound (known as the photoacoustic effect). This sound is detected by spherical ultrasonic sensors.

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