INSTITUTE OF PHYSICS PUBLISHING PHYSICS IN MEDICINE AND BIOLOGY Phys. Med. Biol. 48 (2003) 357–370 PII: S0031-9155(03)53741-1 Poly(vinyl alcohol) gels for use as tissue phantoms in photoacoustic mammography Alexei Kharine 1 , Srirang Manohar 1 , Rosalyn Seeton, Roy G M Kolkman, Ren´ e A Bolt, Wiendelt Steenbergen and Frits F M de Mul Biophysical Techniques Group, Faculty of Applied Physics, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands E-mail: W.Steenbergen@tn.utwente.nl Received 20 September 2002 Published 22 January 2003 Online at stacks.iop.org/PMB/48/357 Abstract Materials for solid photoacoustic breast phantoms, based on poly(vinyl alcohol) hydrogels, are presented. Phantoms intended for use in photoacoustics must possess both optical and acoustic properties of tissue. To realize the optical properties of tissue, one approach was to optimize the number of freezing and thawing cycles of aqueous poly(vinyl alcohol) solutions, a procedure which increases the turbidity of the gel while rigidifying it. The second approach concentrated on forming a clear matrix of the rigid poly(vinyl alcohol) gel without any scattering, so that appropriate amounts of optical scatterers could be added at the time of formation, to tune the optical properties as per requirement. The relevant optical and acoustic properties of such samples were measured to be close to the average properties of human breast tissue. Tumour simulating gel samples of suitable absorption coefficient were created by adding appropriate quantities of dye at the time of formation; the samples were then cut into spheres. A breast phantom embedded with such ‘tumours’ was developed for studying the applicability of photoacoustics in mammography. 1. Introduction Recent years have seen many research efforts in developing optical imaging of tissue into a diagnostic modality, with a thrust in mammography, as an alternative to conventional radiological techniques. Several embodiments of optical mammographs using near-infrared light (NIR) have been showcased in this regard, which can broadly be classified into time- domain (Grosenick et al 1999, Hebden et al 2001) and frequency-domain (Fantini et al 1997, 1 These authors contributed equally to the work. 0031-9155/03/030357+14$30.00 © 2003 IOP Publishing Ltd Printed in the UK 357