Improved in vivo photoacoustic microscopy based on a virtual-detector concept

• Published in: Optics letters Vol. 31; no. 4; p. 474
• Main Authors: Li, Meng-Lin, Zhang, Hao E, Maslov, Konstantin, Stoica, George, Wang, Lihong V
• Format: Journal Article
• Language: English
• Published: United States 15.02.2006
• Subjects: Algorithms; Animals; Image Enhancement - instrumentation; Image Enhancement - methods; Image Interpretation, Computer-Assisted - instrumentation; Image Interpretation, Computer-Assisted - methods; Microscopy, Confocal - instrumentation; Microscopy, Confocal - methods; Phantoms, Imaging; Rats; Reproducibility of Results; Scalp - anatomy & histology; Scalp - blood supply; Sensitivity and Specificity; Transducers; Ultrasonography - instrumentation; Ultrasonography - methods; User-Computer Interface
• ISSN: 0146-9592
• DOI: 10.1364/ol.31.000474

Recently an in vivo high-resolution backward-mode photoacoustic microscope was developed that shows potential for applications in dermatology and related cancer research. However, the limited depth of focus of the large-numerical-aperture (NA) ultrasonic lens employed in this system causes the image quality to deteriorate significantly in the out-of-focus region. To solve this problem, we devised and explored, for the first time to our knowledge, a virtual-detector-based synthetic-aperture focusing technique, combined with coherence weighting, for photoacoustic microscopy with such a large-NA transducer. Images of phantoms show that the proposed technique improves the -6 dB lateral resolution from 49-379 to 46-53 microm and increases the signal-to-noise ratio by up to 29 dB, depending on the distance from the ultrasonic focal point. In vivo experiments show that the technique also provides a clearer representation of the vascular distribution in the rat's scalp.