Miniature radiation source with flexible probe and laser driven thermionic emitter

A therapeutic radiation source, comprising:

• A. a flexible catheter extending along a probe axis between a proximal end and a distal end of the catheter, the flexible catheter comprising optical delivery means extending along said probe axis and having an originating end and a terminating end, and adapted for transmitting optical radiation incident on said originating end to said terminating end;
• B. an optical source, including means for generating a beam of optical radiation directed to said originating end of said optical delivery means;
• C. a radiation source coupled to said terminating end of said optical delivery means, comprising a substantially rigid housing enclosing an electron source and a target, said housing defining a substantially evacuated interior region extending along a beam axis between said electron source at an input end of the housing and a radiation transmissive window at an output end of the housing,
• a. wherein said electron source and said target are disposed along said beam axis and spaced apart from and opposite each other;
• b. wherein said electron source is adapted to emit electrons in response to optical radiation transmitted to said terminating end, and comprises a thermionic emitter having an electron emissive surface;
• and
• c. wherein said target is responsive to incident electrons to emit therapeutic radiation whereby therapeutic radiation emitted therefrom is directed through the radiation transmissive window;
• and
• D. means for establishing an accelerating electric field extending between said electron source toward said target, the electric field acting to accelerate electrons emitted from said electron source toward said target;
• wherein said optical delivery means are adapted for directing a beam of optical radiation transmitted therethrough to impinge upon said surface of said thermionic emitter, and wherein said beam of transmitted optical radiation has a power level sufficient to heat at least a portion of said surface to an electron emitting temperature so as to cause thermionic emission of electrons from said surface.