Dark-field confocal photoacoustic microscopy

Photoacoustic microscopy (PAM) [1-3] is a recently developed modality of photoacoustic (PA) imaging. Similar to other PA imaging technologies, PAM detects laser-induced ultrasonic waves (referred to as PA waves) to image the internal distribution of optical energy deposition (specific optical absorption) in biological tissue. Therefore, PAM reveals physiologically specific optical absorption contrast. However, it differs from reconstruction-based photoacoustic tomography (PAT) [4-7] in several aspects. First, PAM provides high spatial resolution by detecting the high-frequency components of the PA waves [8]. Second, PAM optimizes for the signal-to-noise ratio (SNR) by employing an optical-ultrasonic confocal geometry [2]. Third, PAM involves no inverse reconstruction algorithms [9,10]. Fourth, PAM minimizes unwanted interferences by employing novel optical illumination design.