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3D acoustic resolution-based photoacoustic endoscopy with dynamic focusing.

Background
Acoustic resolution-based photoacoustic endoscopy (ARPAE) is a non-invasive potential tool for imaging gastrointestinal and urogenital tracts. However, current ARPAE systems usually only provide 2D sectorial B-mode images, and have the limitation of the image quality significantly deteriorating out-of-focus regions due to transducers with fixed focus in these systems. To overcome these limitations, we put forward a modified back-projection method that can provide 3D images with dynamic focusing in ARPAE.


Methods
A graphics processing unit (GPU)-based parallel computation technique was adopted for efficient computation. Both simulated and phantom/ex-vivo experiments were conducted to validate our method.


Results
The findings indicated that our proposed method can effectively improve the lateral resolution and signal-to-noise ratio (SNR) in the out-of-focus regions. For a target 3 mm from the transducer focus, the new method can improve 11 times in the lateral resolution, along with an improvement of up to 37 dB in the SNR.


Conclusions
3D ARPAE provides high-quality imaging in both focus and out-of-focus regions.