title: Theoretical comparison of the SAR distributions from arrays of modified current sheet applicators with that of lucite cone applicators using Gaussian beam modelling.
abstract: The technical comparison of Current Sheet Applicator (CSA) and Lucite Cone Applicator (LCA) arrays covering an area of approximately 20 x 20 cm2 is investigated based on Gaussian beam (GB) predicted SAR distributions. The comparison is made in muscle equivalent tissue at 1 cm depth (maximum SAR normalized to 100%) and over a volume of 3 cm depth under the aperture of the antennae. The planar SAR distribution is tested on field sizes (FSx: area covering x% SAR), penetration depth (PD) and homogeneity coefficient (HC = FS75/FS25). From the SAR volume, a SAR-Volume histogram (volume enclosing y% SAR/total volume) is calculated as well as the volumetric HC. First, the prototype CSA (aperture 58 x 67 mm2, FS50 = 21 cm2) is technically modified to assure clinical safety and load independence. The modified CSA, the D-CSA, has an aperture of 66 x 75 mm2 with an FS50 = 28 cm2 and a PD of 10 mm, the LCA (aperture 105 x 105 mm2) has an FS50 = 76 cm2 and PD = 12 mm. The HC equals 0.21 (D-CSA), respectively 0.22 (LCA). Secondly, a 3 x 3 D-CSA array is compared with a 2 x 2 LCA array. The FS50s equals 72% (D-CSA), respectively 75% (LCA). The SAR-volume histograms, planar and volumetric HC show no significant difference; however, the planar HCs for D-CSA and LCA increase from 0.2-0.3, indicating that incoherently powered arrays from these antennae build SAR distributions constructively.
authors.affiliation: University Hospital Rotterdam-Daniel, Department of Radiation Oncology, The Netherlands. rietveld@hyph.azr.nl
authors.forename: P J
authors.initials: PJ
authors.lastname: Rietveld
authors.forename: J
authors.initials: J
authors.lastname: Stakenborg
authors.forename: T C
authors.initials: TC
authors.lastname: Cetas
authors.forename: M L
authors.initials: ML
authors.lastname: Lumori
authors.forename: G C
authors.initials: GC
authors.lastname: Van Rhoon
mesh_terms: D000465:Algorithms; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods*; D009369:Neoplasms / Q000628:therapy; D016011:Normal Distribution; D019047:Phantoms, Imaging; D019904:Polymethyl Methacrylate; D011786:Quality Control; D011827:Radiation
chemical_list: D019904:Polymethyl Methacrylate