The aim of this study was to evaluate the operating characteristics of a microwave radiometry system in the noninvasive assessment of activated and nonactivated brown adipose tissue (BAT) and normal-tissue temperatures, reflecting metabolic activity in healthy human subjects. The radiometry data were compared with F-FDG PET/CT images in the same subjects. Microwave radiometry and F-FDG PET/CT were sequentially performed on 19 participants who underwent a cold intervention to maximize BAT activation. The cold intervention involved the participants' intermittently placing their feet on an ice block while sitting in a cool room. Participants exhibiting BAT activity qualitatively on PET/CT were scanned again with both modalities after undergoing a BAT minimization protocol (exposure to a warm room and a 20-mg dose of propranolol). Radiometry was performed every 5 min for 2 h before PET/CT imaging during both the warm and the cold interventions. A grid of 15-20 points was drawn on the participant's upper body (data were collected at each point), and a photograph was taken for comparison with PET/CT images. PET/CT identified increased signal consistent with BAT activity in 11 of 19 participants. In 10 of 11 participants with active BAT, radiometry measurements collected during the cold study were modestly, but significantly, higher on points located over areas of active BAT on PET/CT than on points not exhibiting BAT activity ( < 0.01). This difference lessened during the warm studies: 7 of 11 participants showed radiometry measurements that did not differ significantly between the same set of points. The mean radiometry result collected during BAT maximization was 33.2°C ± 1.5°C at points designated as active and 32.7°C ± 1.3°C at points designated as inactive ( < 0.01). Passive microwave radiometry was shown to be feasible and, with substantial improvements, has the potential to noninvasively detect active brown adipose tissue without a radiotracer injection.

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The paper describes a new approach to the treatment of solid malignant tumors. In this approach the tumors are thermally ablated with minimally invasive microwave balloon catheters, and the cavities created in the tumors by the balloon catheters are filled with anticancer agents that can be forced through the ablated malignant tissues to the margins of the tumors in order to destroy any remaining viable tumor cells. In vivo and in vitro experiments are described that illustrate the ability of microwave balloon ablation catheters to rapidly ablate of large volumes of tissues, to create reservoirs for anticancer agents in the ablated (necrosed) tissues, and to force substances with large molecular weights that are introduced into these reservoirs through the ablated tissues to the margins of the ablation.

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