Alon Goren

Coherent hollow-core waveguide bundles for infrared imaging

Coherent IR fiber optic bundles for use in IR imaging from 2 to 12 µm are fabricated from rigid hollow-glass waveguide arrays. The bore of each hollow glass tube in the bundle is coated with thin films of metallic Ag followed by AgI for enhanced reflectivity. The coating of the rigid bundle is done using liquid phase chemistry techniques applied to all tubes simultaneously. The hollow-glass arrays are composed of up to 900 individual tubes with bore sizes as small as 50 µm. Several rigid hollow-core arrays are used to transmit an IR image of a small loop of hot wire and a sample of tissue heated by a CO2 laser.

Ventilating Hornets Display Differential Body Temperature

Our investigation entailed a thermal analysis of hornets engaging in ventilation activity at the nest entrance. In the hot summer months, between July–October, ventilating worker hornets are seen just outside the nest entrance, where they assume a typical stance, namely, with their feet erect and fastened to the substrate, their abdomen bent downward at a 90◦ angle to the thorax, their antennae vibrating, and their wings beating rapidly for minutes at a time. Eventually these hornets leave their position, either to retreat into the nest or else to fly off to the field, and are replaced by new hornets that assume the ventilation task. Infra-red (IR) photography reveals that in the course of the ventilation activity, the warmest region in the ventilating hornet body is the anterior upper part of the thorax, and the coolest regions are the wings, limbs, antennae and abdomen. This study involved precise and repeated measurements via IR photography of the temperature in the various body parts of the ventilating hornets, and it also offers a preliminary, tentative explanation for the observed differential body temperature. The communication value of the color of the hornet body when ventilating is discussed.

Thermal imaging through infrared fiber/waveguides bundles

Trans-endoscopic Infrared Imaging (IRI) relates the possibility to conduct IRI diagnosis of internal body surfaces under minimal invasiveness. It may also be utilized to control and to optimize the thermal interactions and the potential side effects during Minimally Invasive Surgeries (MIS). However, transferring the thermal images transendoscopically requires the usage of IR imaging bundles, which are neither yet mature nor commercially available. In our setup we have used two basic types of recently-developed imaging bundles: Ag/AgI-coated Hollow Glass Waveguide (HGW) bundles and Silver Halide (AgClBr) core-clad fiber bundles. The optical setup system was consisted of IR optics (e.g. ZnSe lenses, reflective objectives) and a thermal IR camera. We have succeeded to image objects through the bundles, such as various shapes of electrically heated wires, ex-vivo biological phantoms (samples of porcine stomach) and in-vivo phantom models (mice) irradiated by CO2 laser. Measurements were conducted for both - static and dynamic object states.

Transendoscopic laser-based surgical procedure within body cavities

The recent development of flexible hollow waveguides for MID-IR lasers may be utilized transendoscopically to ablate selectively neoplastic, superficial tissues within body cavities. Study goals are to investigate theoretically and experimentally heat distribution and thermal response of cavity lining, during CO2 laser Minimally Invasive Surgery (MIS), and to thermally optimize the procedure under practical conditions. Mathematical model was developed to predict temperature distribution along cavity lining during and after the irradiation. Experimental setup was built, including all the necessary components for a fully feedback-controlled MIS (CO2 laser, hollow waveguide, suction, insufflation, electrical regulators, cavity-like phantoms, IR camera, Labview application). Thermal images of cavity lining were recorded and analyzed throughout varying conditions. Thermal gradients were obtained mathematically and experimentally. Diverse modes of heat dispersions were observed, as wel as the relative contributions of user-controlled parameters to the maximal heat of cavity lining. The software-controlled setup has demonstrated instant adaptivity to manage varying conditions, by which it automatically protects cavity lining from getting overheated. Analytical predictions and experimental measurements were highly correlated. The software-controlled systme may serve a powerful tool to control thermal side effects during MIS within body cavities.