Improving the imaging ability of ultrasound-modulated optical tomography with spectral-hole burning

Abstract

Ultrasound-modulated optical tomography is a hybrid imaging technique based on detection of the diffused light modulated by a focused ultrasonic wave inside a scattering medium. With the combined advantages of ultrasonic resolution and optical contrast, UOT is ideal for deep tissue imaging. Its growth in popularity and application, however, is hindered by the low efficiency in detecting the modulated diffused photons. Research activities on UOT have therefore been centered on improving its signal detection efficiency by exploring various technical solutions. A prime example is the use of spectral-hole burning (SHB) in UOT. By applying SHB crystal as a spectral filter, one modulation sideband of the diffused light can be efficiently selected while all the other frequency components are strongly suppressed. Immune to both the spatial and temporal incoherence of the signal with a high enough on/off ratio, SHB can boost the UOT imaging ability dramatically and push it towards practical applications. We compare SHB with the other technologies that have been applied to UOT, and identify the unique features that make SHB a preferable tool for UOT. We also discuss the desired improvements from the SHB side, which will help UOT pave the way from research to everyday life.