Progress on ThermoBrachytherapy Surface Applicator for Superficial Tissue Diseases.

This work reports the ongoing development of a combination applicator for simultaneous heating of superficial tissue disease using a 915 MHz DCC (dual concentric conductor) array and High Dose Rate (HDR) brachytherapy delivered via an integrated conformal catheter array. The progress includes engineering design changes in the waterbolus, DCC configurations and fabrication techniques of the conformal multilayer applicator. The dosimetric impact of the thin copper DCC array is also assessed. Steady state fluid dynamics of the new waterbolus bag indicates nearly uniform flow with less than 1°C variation across a large (19×32cm) bolus. Thermometry data of the torso phantom acquired with computer controlled movement of fiberoptic temperature probes inside thermal mapping catheters indicate feasibility of real time feedback control for the DCC array. MR (magnetic resonance) scans of a torso phantom indicate that the waterbolus thickness across the treatment area is controlled by the pressure applied by the surrounding inflatable airbladder and applicator securing straps. The attenuation coefficient of the DCC array was measured as 3± 0.001% and 2.95±0.03 % using an ion chamber and OneDose dosimeters respectively. The performance of the combination applicator on patient phantoms provides valuable feedback to optimize the applicator prior use in the patient clinic.