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 ˜ 20 x 20cm² is investigated based on Gaussian beam (GB) predicted SAR distributions. The comparison is made in muscle equivalent tissue at 1cm depth (maximum SAR normalized to 100%) and over a volume of 3cm depth under the aperture of the antennae. The planar SAR distribution is tested on field sizes (FS_x: 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 67mm², FS₅₀ = 21cm²) is technically modified to assure clinical safety and load independence. The modified CSA, the D-CSA, has an aperture of 66 x 75mm² with an FS₅₀ = 28cm² and a PD of 10mm, the LCA (aperture 105 x 105 mm²) has an FS₅₀ = 76cm² and PD = 12mm. 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.

• Superficial Hyperthermia Microwave Antenna Gaussian Beam Modelling Sar Distribution Quality Assurance