Polymeric-matrix brachytherapy sources

Abstract

Therapeutic sources for use in the practice of brachytherapy comprise a radioactive composite that includes (a) a polymeric matrix and (b) a radioactive powder, e.g. Pd-103 or I-125, consisting essentially of very fine radioactive particles that are randomly and essentially uniformly dispersed within the polymeric matrix. The composite may be in the shape of one or more solid cylindrical rods surrounded by a non-radioactive sleeve. Alternatively it may be a hollow rod, suture, film, sheet, or microspheroidal particles.

1 . A therapeutic source comprising a radioactive composite consisting essentially of (a) polymeric matrix and (b) a radioactive powder consisting essentially of very fine radioactive particles that are randomly and essentially uniformly dispersed within said polymeric matrix; 
 wherein the radioactive composite is in the shape of one or more right circular cylindrical rods, solid in cross section, having a cylindrical wall and a pair of ends, wherein the therapeutic source further comprises a non-radioactive sleeve which surrounds the cylindrical wall of sufficient thickness to absorb a portion of the radiation emitted by the radioactive composite.    
   
   
       2 . The therapeutic source of  claim 1 , further comprising a pair of non-radioactive caps covering each of the pair of ends, the caps being of sufficient thickness to absorb a portion of the radiation emitted by the radioactive composite.  
   
   
       3 . A plurality of therapeutic sources of  claim 1 , wherein the radioactive composite of each of said sources has substantially the same radioactivity emission characteristics as each of the other of the plurality of sources, and wherein the thickness of the non-radioactive sleeve is different from that of the others in said plurality of sources such that a different amount of the emitted radiation is absorbed, whereby a medical practitioner has the option of selecting from among the plurality of sources a particular source emitting the radiation dosage most desirable for implantation in a patient in accordance with a treatment plan.  
   
   
       4 . A therapeutic source comprising a radioactive composite consisting essentially of (a) polymeric matrix and (b) a radioactive powder consisting essentially of very fine radioactive particles that are randomly and essentially uniformly dispersed within said polymeric matrix; 
 wherein the radioactive composite is in the shape of one or more right circular cylindrical rods, solid in cross section, having a cylindrical wall and a pair of ends, wherein the therapeutic source further comprises a non-radioactive sleeve which surrounds the cylindrical wall of a composition and sufficient thickness to modify the energy spectrum of the radiation emitted by the radioactive composite.    
   
   
       5 . The therapeutic source of  claim 4 , further comprising a pair of non-radioactive caps covering each of the pair of ends, the caps being of a composition and sufficient thickness to modify the energy spectrum of the radiation emitted by the radioactive composite.  
   
   
       6 . The therapeutic source of  claim 4 , wherein the radioactive composite emits beta particles and the sleeve modifies the energy spectrum of the emitted radiation by reducing the average energy of the beta particles and creating bremstrahlung.  
   
   
       7 . A plurality of therapeutic sources of  claim 4 , wherein the radioactive composite of each of said sources has substantially the same radioactivity emission characteristics as each of the others of the plurality of sources, and wherein the thickness of the non-radioactive sleeve is different from that of the others in said plurality of sources such that the energy spectrum of the emitted radiation is modified by a different amount, whereby a medical practitioner has the option of selecting from among the plurality of sources a particular source emitting the radiation dosage most desirable for implantation in a patient in accordance with a treatment plan.  
   
   
       8 . A method of providing brachytherapy treatment to a tissue comprising the steps of: 
 (a) generating a treatment plan for the tissue to be treated, which treatment plan specifies the dose rate of emitted radiation from a brachytherapy source,    (b) providing a plurality of therapeutic sources in the shape of one or more right circular cylindrical rods, solid in cross section, having a cylindrical wall, comprising a radioactive composite consisting essentially of (a) polymeric matrix and (b) a radioactive powder consisting essentially of very fine radioactive particles, wherein the radioactive composite is in the shape of one or more right circular cylindrical rods, solid in cross section, having a cylindrical wall and a pair of ends, each of the therapeutic sources further comprising a non-radioactive sleeve which surrounds the cylindrical wall, wherein the radioactive composite of each of said sources has substantially the same radioactivity emission characteristics as each of the other of the plurality of sources, and wherein the thickness of the non-radioactive sleeve is different from that of the other sources in said plurality such that a different amount of the emitted radiation is absorbed; and    (c) selecting from among the plurality of sources a particular source emitting the radiation dosage most desirable for implantation in a patient in accordance with a treatment plan.