Xoft, Inc.

Superior Technical Ceramics Corporation

Xoft Microtube, Inc.

Peter Clark Smith

Paul A Lovoi

Alex L Lim

Robert G Neimeyer

Petre Vatahov

Thomas W Rusch

Earl E Dozier

Leonard Reed

Steve Axelrod

Michael Robert Forman

Heike Hausen

Michael Klein

Steven D Hansen

Donald G Pellinen

Robert W LeClair

John Rieke

The electron emission portion of a cathode for an electron gun has layers of substrate material formed from a ceramic powder such as Aluminum nitride. The substrate layers have conductive traces formed on them, the conductive traces made from sintered tungsten or alternatively a refractory foil. When current is passed through the conductive traces, heat is coupled to a cathode which is thermally coupled to the heater assembly. In another embodiment of the invention, one of the layers of the heater includes a thermionic emission material and optionally a work function lowering material such as BaO, which allows the outer layer of the multi-layer heater to directly emit electrons. In another embodiment of the invention, a control grid is formed on a layer above the thermionic cathode layer, which provides for a complete electron gun assembly having a heater, cathode with a reduced work function material, and control grid to be fabricated as a single unit at the same time.

Multi-layer heater for an electron gun

A flexible, lightweight radiation absorbing sheet or shield includes heavy metal particles in one layer and mid-atomic number particles in another layer, the layer that will be adjacent to the patient. The shield is particularly intended for protection of the wearer and others from radiation emanating from a therapeutic source positioned within the patient's body. With the disclosed multi-layer shield construction, backscattered radiation off the heavy metal particle layer, affecting the patient's adjacent tissue, is minimized.

Lightweight radiation absorbing shield

Brachytherapy applicators incorporate various forms of selective shielding devices for controlling the direction and intensity of radiation directed at a patient's tissue. In some forms the applicators include a retractable sheath, in some a series of retractable fingers. In other forms the applicator, having an inflatable balloon, has a shield which is retractable from a position adjacent to the balloon or retracted from the balloon, or a shield can itself be inflatable, separately or together with the balloon.

Radiation therapy apparatus with selective shielding capability

Age-related macular degeneration is treated by radiation delivered from a miniature x-ray tube inserted via a catheter around the globe of the eye, to a position behind the macula. The process can employ an applicator with several parallel guides, inserted around the eye to receive the catheter with x-ray tube (or an isotope) at a matrix of different positions. Methods are described for properly locating the catheter and x-ray tube, using illumination on the catheter and viewing through the front of the eye, or sensors on the catheter and a scanned beam shone from the front of the eye. Fluorescent material excited by x-rays can also be used. Also described are methods and devices for immobilizing the probe once properly located in the eye, for standoff of the x-ray tube from the target tissue, and for achieving prescription radiation dose in the choroid while eliminating dose to adjacent tissues. The x-ray treatment can be enhanced using a radiosensitizing drug, and can be combined with PDT.

Treatment of age-related macular degeneration

A miniature x-ray tube has an anode assembly capable of transmitting x-rays through the anode and over a wide angular range. The anode is in the shape of a cone or truncated cone with an axis on the x-ray tube frame axis, formed of low-Z material with high thermal conductivity for heat dissipation. A target material on the anode body is in a thin layer, which may be approximately 0.5 to 5 microns thick. In one embodiment a tube evacuation exhaust port at the tail end of the anode assembly forms a cavity for a getter, with a pinched-off tubulation at the end of the cavity.

Anode assembly for an x-ray tube

Methods for connecting electrical potential to an extractor cup at the cathode of a miniature x-ray tube are disclosed. The various connection schemes are designed to form a rugged and conveniently manufacturable connection between the metal extractor cup and one side of the cathode filament, so that the extractor cup shapes the path of electrons as desired en route to the anode of the tube. Some of the disclosed connections involve evaporation of conductive metal or other materials off the filament when the filament is first activated. Others involve applying a paste or paint conductive precursor directly to a base to connect a post and the extractor, the paste being heat-cured after the completion of assembly. Others involve a fine wire or spring strip from one filament post to the walls of the extractor cup. Other schemes include welded or brazed wires or foil, crimping, pinching, swaging and other connections, all made inside the tube enclosure.

Extractor cup on a miniature x-ray tube

A miniature x-ray tube is cooled using a catheter preferably having multiple small lumens for inflow and outflow of coolant. Inflow may be through an outer lumen(s) in a concentric-extrusion catheter, the liquid turning back at the distal end of the catheter to a proximal flow over the anode end of the x-ray tube and through an inner lumen within which the x-ray tube is positioned. A coolant distribution head may engage with the anode end of the x-ray tube, with small orifices so as to distribute coolant essentially evenly over the anode surface. Temperature and flow rate of the inflowing coolant liquid are balanced so as to optimize heat transfer while efficiently carrying coolant through small lumens without the need for high pressures. Some embodiments use the inflation liquid in an applicator balloon as the coolant, with the liquid actively flowing or, in a simplified system, with the liquid static.

Miniature x-ray tube cooling system

In a miniature x-ray tube, which may be on the order of approximately 1 mm in diameter or even less, a high voltage cable is provided in various embodiments for conducting current to the cathode of the x-ray tube and for conducting high voltage to the cathode and anode of the tube. In various embodiments of the cable, two conductors occupy a center region of the cable, packed as closely together as possible, in various shapes that are compact and present as smooth as possible an external shape for maximizing dielectric properties against the exterior high voltage ground, surrounding and generally concentric with the inner conductors. The inner conductors, which carry high voltage in opposition to the outer ground, can be in opposed D shapes, coaxial, two flattened conductors side by side, or simply a pair of cylindrical wires positioned as closely as possible. The space between the inner conductors and the outer ground can be occupied by a glass insulator, polymer, successive layers of polymers and adhesive, air, gas, vacuum or other dielectrics. A partially conductive region can surround the inner conductors.

Growing community of inventors

Half Moon Bay, CA, United States of America

Peter Clark Smith