A Directional Interstitial Antenna for Microwave Tissue Ablation: Theoretical and Experimental Investigation.

Microwave ablation (MWA) is a minimally invasive thermal therapy modality increasingly employed for the treatment of tumors and benign disease. For successful treatment, complete thermal coverage of the tumor and margin of surrounding healthy tissue must be achieved. Currently available interstitial antennas for MWA have cylindrically symmetric radiation patterns. Thus, when treating targets in proximity to critical structures, caution must be taken to prevent unintended thermal damage. A novel coaxial antenna design for MWA with an asymmetrical cylindrical heating pattern is presented in this paper. This radiation pattern is achieved by employing a hemicylindrical reflector positioned at a critical distance from a conventional coaxial monopole antenna. Finite-element method simulations were employed to optimize the geometric dimensions of the antenna with the objective of minimizing the antenna reflection coefficient at the 2.45-GHz operating frequency, and maximizing volume of the ablation zone. Prototype antennas were fabricated and experimentally evaluated. Simulations indicated an optimal S11 of -32 dB at 2.45 GHz in close agreement with experimental measurements of -29 dB. Ex vivo experiments were performed to validate simulations and observe effects to the antennas' heating pattern with the varying input power and geometry of the reflector. Ablation zones up to 20 mm radially were observed in the forward direction, with minimal heating (less than 4 mm) behind the reflector.

Sensors and instrumentation for unobtrusive sleep quality assessment in autistic children.

Little is understood about the sleep quality of children with autism and other developmental disabilities. Conventional sensors and instrumentation for objective sleep quality assessment, such as those used in polysomnography, are highly obtrusive and not well-suited to this patient population. This paper presents a set of sensors and instrumentation for unobtrusive measurement of physiological and behavioral parameters indicative of sleep quality. Specifically, load cells, an electromechanical film, and thermocouples are used to measure respiratory rate, pulse rate, and physical activity of a subject lying on a bed. The sensor suite is being developed to monitor sleep quality of children at Heartspring, a residential and educational facility in Wichita, KS that serves children with severe developmental disabilities. These technologies have the potential to provide objective sleep quality assessment for children in their home environment.