IOP PUBLISHING PHYSICS IN MEDICINE AND BIOLOGY Phys. Med. Biol. 56 (2011) N115–N122 doi:10.1088/0031-9155/56/8/N01 NOTE Effects of formalin fixation on tissue optical polarization properties M F G Wood 1 , N Vurgun 1 , M A Wallenburg 1 and I A Vitkin 1,2 1 Division of Biophysics and Bioimaging, Ontario Cancer Institute and Departments of Medical Biophysics 2 Radiation Oncology, University of Toronto, 610 University Avenue, Toronto, ON M5G 2M9, Canada E-mail: mwood@uhnres.utoronto.ca Received 13 December 2010, in final form 25 February 2011 Published 28 March 2011 Online at stacks.iop.org/PMB/56/N115 Abstract Formalin fixation is a preparation method widely used in handling tissue specimens, such as biopsies, specifically in optical studies such as microscopy. In this note, we examine how formalin fixation affects the polarization properties of porcine myocardium and liver as assessed by optical polarimetry. Spatial maps of linear retardance and depolarization were derived from four myocardial and four liver samples before and after formalin fixation. Overall, linear retardance and depolarization increased after fixation for both myocardium (15% and 23% increase, respectively) and liver (38% and 51%, respectively). The relative increase in retardance was greater in liver compared to myocardium, although the absolute increase in retardance was comparable for both. The effect of fixation on bulk optical properties was also investigated for myocardium where the scattering coefficient increased from 92 to 132 cm −1 and the absorption coefficient remained constant at 1.1 cm −1 . (Some figures in this article are in colour only in the electronic version) 1. Introduction Polarized light can be used as a diagnostic tool to characterize tissue structure (Wu and Walsh 2006, Ghosh et al 2008a, 2008b, Wood et al 2009), provided sufficient polarization is maintained in polarized light interacting with the biological sample, so that one can quantify the tissue polarization effects of the medium. Linear birefringence and optical rotation are two useful polarization properties that provide potentially useful biological metrics. As an example, we have demonstrated linear birefringence as a metric for measuring the structural organization of the myocardium in healthy, infarcted, and stem-cell-regenerated tissues (Wood et al 2009). In addition, we have investigated the use of glucose-induced optical rotation to quantify glucose concentrations in tissue-like media (Guo et al 2006). 0031-9155/11/080115+08$33.00 © 2011 Institute of Physics and Engineering in Medicine Printed in the UK N115