title: Investigation of ultrasonic properties of PAG and MAGIC polymer gel dosimeters.
abstract: Ultrasonic speed of propagation and attenuation were investigated as a function of absorbed radiation dose in PAG and MAGIC polymer gel dosimeters. Both PAG and MAGIC gel dosimeters displayed a dependence of ultrasonic parameters on absorbed dose with attenuation displaying significant changes in the dose range investigated. The ultrasonic attenuation dose sensitivity at 4 MHz in MAGIC gels was determined to be 4.7 +/- 0.3 dB m(-1) Gy(-1) and for PAG 3.9 +/- 0.3 dB m(-1) Gy(-1). Ultrasonic speed dose sensitivities were 0.178 +/- 0.006 m s(-1) Gy(-1) for MAGIC gel and -0.44 +/- 0.02 m s(-1) Gy(-1) for PAG. Density and compressional elastic modulus were investigated to explain the different sensitivities of ultrasonic speed to radiation for PAG and MAGIC gels. The different sensitivities were found to be due to differences in the compressional elastic modulus as a function of dose for the two formulations. To understand the physical phenomena underlying the increase in ultrasonic attenuation with dose, the viscoelastic properties of the gels were studied. Results suggest that at ultrasonic frequencies, attenuation in polymer gel dosimeters is primarily due to volume viscosity. It is concluded that ultrasonic attenuation significantly increases with absorbed dose. Also, the ultrasonic speed in polymer gel dosimeters is affected by changes in dosimeter elastic modulus that are likely to be a result of polymerization. It is suggested that ultrasound is a sufficiently sensitive technique for polymer gel dosimetry.
authors.affiliation: Centre for Medical, Health and Environmental Physics, Queensland University of Technology, Brisbane, Australia.
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Mather
authors.forename: Yves
authors.initials: Y
authors.lastname: De Deene
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Whittaker
authors.forename: George P
authors.initials: GP
authors.lastname: Simon
authors.forename: Rulande
authors.initials: R
authors.lastname: Rutgers
authors.forename: Clive
authors.initials: C
authors.lastname: Baldock
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry / Q000528:radiation effects*; D001205:Ascorbic Acid / Q000737:chemistry* / Q000528:radiation effects; D019327:Copper Sulfate / Q000737:chemistry* / Q000528:radiation effects; D003720:Densitometry / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D004548:Elasticity; D005780:Gelatin / Q000737:chemistry* / Q000528:radiation effects; D005782:Gels / Q000737:chemistry / Q000528:radiation effects; D006873:Hydroquinones / Q000737:chemistry* / Q000528:radiation effects; D008422:Materials Testing / Q000379:methods; D008689:Methacrylates / Q000737:chemistry* / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D033081:Shear Strength; D014463:Ultrasonography / Q000379:methods*; D014783:Viscosity
chemical_list: D000180:Acrylic Resins; D005782:Gels; D006873:Hydroquinones; C476159:MAGIC polymer gel; D008689:Methacrylates; D011108:Polymers; C016680:polyacrylamide gels; D005780:Gelatin; D019327:Copper Sulfate; D001205:Ascorbic Acid