Feature Of The Week 09/10/2017: Thermo-elastic Optical Coherence Tomography
The conventional OCT image contrast is derived from elastic scattering, and shows the internal structure of the sample. The determination of the tissue type in OCT images usually depends on the interpretation by the image reader. More accurate tissue type contrast may be achieved by new OCT-based imaging modalities, with sensitivity to other physical parameters than scattering alone.
Phase-sensitive OCT can detect tissue motion on nanometer-to-micrometer length scales using the phase of the OCT signal. Depending on the nature of the excitation, different functional images can be reconstructed: a mechanical stimulus yields images of tissue elasticity (optical coherence elastography), while continuous-wave laser illumination provides photo-thermal deformation images (photo-thermal OCT).
In this study, we will use nanosecond laser pulses to induce rapid thermo-elastic deformation in tissue, which happens within a few microseconds. We use phase-sensitive Megahertz OCT to investigate the associated displacement that is caused by the thermo-elastic deformation. Our phantom studies show that the associated displacement can be detected within a few microseconds. The deformation relies upon the absorption of the laser pulse. Based on the displacement detection, we further introduce a new modality of phase-sensitive OCT, called Thermo-elastic OCT (TE-OCT). TE-OCT can detect the optical absorbers that cannot be observed in the conventional OCT images. TE-OCT can also high light different tissue types by changing the wavelength of the excitation pulsed laser.
TE-OCT can potentially be used for diseased tissue identification requiring the integration of a short pulse laser to the current OCT platform. The short deformation accumulation time and the laser-based excitation make it possible to apply TE-OCT for endoscopic imaging at an A-line rate of 50-100 kHz, depending on the time required to capture the transient.
For more information see recent Article. Courtesy Tianshi Wang and Tom Pfeiffer from Erasmus University.