title: Poly(vinyl alcohol) gels as photoacoustic breast phantoms revisited.
abstract: A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F-T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where temperature distributions during F-T are relatively homogeneous. In this work, in breast-sized samples we observed substantial temperature differences between the shallow regions and the interior during the F-T procedure. We investigated whether spatial variations were also present in the acoustic and optical properties. The speed of sound, acoustic attenuation, and optical reduced scattering coefficients were measured on specimens sampled at various locations in a large phantom. In general, the properties matched values quoted for breast tissue. But while acoustic properties were relatively homogeneous, the reduced scattering was substantially different at the surface compared with the interior. We correlated these variations with gel microstructure inspected using scanning electron microscopy. Interestingly, the phantom's reduced scattering spatial distribution matches the optical properties of the standard two-layer breast model used in x ray dosimetry. We conclude that large PVA samples prepared using the standard recipe make excellent breast tissue phantoms.
authors.affiliation: University of Twente, Biomedical Photonic Imaging group, Mira Institute for Biomedical Technology and Technical Medicine, P.O. Box 217, 7500AE Enschede, The Netherlands.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Xia
authors.forename: Daniele
authors.initials: D
authors.lastname: Piras
authors.forename: Michelle
authors.initials: M
authors.lastname: Heijblom
authors.forename: Wiendelt
authors.initials: W
authors.lastname: Steenbergen
authors.forename: Ton G
authors.initials: TG
authors.lastname: van Leeuwen
authors.forename: Srirang
authors.initials: S
authors.lastname: Manohar
mesh_terms: D000162:Acoustics; D001940:Breast; D001943:Breast Neoplasms / Q000175:diagnosis; D003952:Diagnostic Imaging / Q000379:methods*; D005260:Female; D005782:Gels; D006801:Humans; D008855:Microscopy, Electron, Scanning; D055620:Optical Phenomena; D019047:Phantoms, Imaging; D061088:Photoacoustic Techniques / Q000379:methods*; D011142:Polyvinyl Alcohol; D012542:Scattering, Radiation; D013499:Surface Properties; D013696:Temperature
chemical_list: D005782:Gels; D011142:Polyvinyl Alcohol