Portable Optical Resolution Photoacoustic Microscopy

With the improvement of current life quality,there is an urgent need for medical techniques.As an important way to diagnose and study diseases,the development of medical imaging techniques is fast.New imaging technologies with advantages of fast,non-destructive,high resolution and high specificity play an important role in clinical medicine and basic medical research.Among them,photoacoustic imaging is a representative biomedical imaging method,which is non-invasive and non-ionizing,and owns comparable contrast to optical imaging and penetration depth to ultrasound imaging.As an important submodality of photoacoustic imaging,optical resolution photoacoustic microscopy not only has a high resolution,but also owns a three-dimensional imaging capability.However,existing optical resolution photoacoustic microscopy mainly uses two-dimensional raster scanning,which makes the system bulky and inflexibility.This defect is severely limiting the applications of optical resolution photoacoustic microscopy.In order to break the limitations of existing optical resolution photoacoustic microscopy,this paper proposes a unique rotary scanning mechanism that not only avoids the relative movement between the imaging interface and the sample,but also simplifies the system design.Simple operations of the system greatly increases the flexibility and versatility of the microscope.Based on this mechanism,we designed and developed the first generation of inverted photoacoustic microscope.The microscope uses a fast scanning galvanometer and a line-focusing ultrasound detector for rapid scanning of the sample,and can be used with a scanning lens or microscope objective to achieve large field of view or high-resolution image acquisition.Subsequently,we applied the device for long-term monitoring of tumor blood vessel growth.Further,in order to realize the handheld photoacoustic microscope,we re-optimized the system design,using dual gear transmission to reduce the system volume.We integrated the imaging system into a 15 cm × 12 cm × 11 cm metal casing,and used universal machinery arms to enhance the flexibility of the system.In the experimental evaluation,we collected images of mouse ear,mouse brain,rabbit ear and rabbit eye to test the performance of the handheld photoacoustic microscope.Finally,we used this handheld photoacoustic microscope to capture high-resolution images of human oral mucosa,and monitored the healing process of oral ulcers.This is the first time that photoacoustic microscopy has been used for human oral examination,which proves the great potential and value of photoacoustic microscopy in clinical research.In addition,we have also proposed the application of photoacoustic microscopy to the field of microfluidics research for the first time.We used the photoacoustic microscope developed to study the kinetics of droplet formation in microchannels,the liquid mixing process,the relationship between molecular concentration and photoacoustic signal amplitude,and biological cell detection.