Effect of tissue preservation on imaging using ultrahigh resolution optical coherence tomography.

Ultrahigh resolution optical coherence tomography OCT is an emerging imaging modality that enables noninvasive imaging of tissue with 1- to 3-m resolutions. Initial OCT studies have typically been performed using harvested tissue specimens ex vivo .N o re- ports have investigated postexcision tissue degradation on OCT image quality. We investigate the effects of formalin fixation and commonly used cell culture media on tissue optical scattering characteristics in OCT images at different times postexcision compared to in vivo con- ditions. OCT imaging at 800-nm wavelength with 1.5-m axial reso- lution is used to image the hamster cheek pouch in vivo, followed by excision and imaging during preservation in phosphate-buffered sa- line PBS, Dulbecco's Modified Eagle's Media DMEM, and 10% neutral-buffered formalin. Imaging is performed in vivo and at se- quential time points postexcision from 15 min to 10 to 18 h. Formalin fixation results in increases in scattering intensity from the muscle layers, as well as shrinkage of the epithelium, muscle, and connective tissue of 50%. PBS preservation shows loss of optical contrast within two hours, occurring predominantly in deep muscle and con- nective tissue. DMEM maintains tissue structure and optical scattering characteristics close to in vivo conditions up to 4 to 6h after excision and best preserved tissue optical properties when compared to in vivo imaging. © 2005 Society of Photo-Optical Instrumentation Engineers.