title: Effect of saccharide additives on response of ferrous-agarose-xylenol orange radiotherapy gel dosimeters.
abstract: Glucose, sucrose, starch, and locust bean gum have been used as additives to the ferrous-agarose-xylenol orange (FAX) gel dosimeter. The saccharide enhanced dosimeters were found to have a higher dose sensitivity over a standard FAX gel as measured by both optical density change and magnetic resonance imaging (MRI). With optical density measurement, OD-dose sensitivity increases were up to 55% for glucose, 122% for sucrose and 43% for starch, while locust bean gum did not give a consistent response. With MRI, R1-dose sensitivity increases were up to 178% with sucrose addition. The FAX gel with sucrose was studied in greatest detail. The OD-dose sensitivity dependence on cooling rate was reduced for the sucrose FAX gel over the standard FAX gel, which has significant implications for uniform dose sensitivity in large gel phantoms. The thermal oxidation rate in the sucrose FAX gel was up to 2.3 times higher than in the standard gel. The OD-dose sensitivity of oxygenated sucrose FAX gels was 4.3 times greater than standard FAX gels, while continued enhancement in OD-dose sensitivity with increased sucrose concentrations beyond 2.0 g/l was found only for the oxygenated sucrose FAX gels. Both the molar absorption coefficient of the ferric ion-xylenol orange complex at 543 nm and gel pH were not affected by the presence of sucrose, with the implication that the higher OD-dose sensitivity of gels with saccharides is due to increased chain reaction production of ferric ions.
authors.affiliation: Centre for Medical, Health and Environmental Physics, Queensland University of Technology, Brisbane, Queensland 4101, Australia. brendan_j_healy@health.qld.gov.au
authors.forename: B J
authors.initials: BJ
authors.lastname: Healy
authors.forename: M H
authors.initials: MH
authors.lastname: Zahmatkesh
authors.forename: K N
authors.initials: KN
authors.lastname: Nitschke
authors.forename: C
authors.initials: C
authors.lastname: Baldock
mesh_terms: D002241:Carbohydrates / Q000737:chemistry / Q000528:radiation effects*; D003720:Densitometry; D019544:Equipment Failure Analysis; D005296:Ferrous Compounds / Q000737:chemistry / Q000528:radiation effects*; D005782:Gels / Q000737:chemistry / Q000528:radiation effects*; D008279:Magnetic Resonance Imaging; D010636:Phenols; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013454:Sulfoxides; D014992:Xylenes
chemical_list: D002241:Carbohydrates; D005296:Ferrous Compounds; D005782:Gels; D010636:Phenols; D013454:Sulfoxides; D014992:Xylenes; C016833:xylenol orange