Systems And Methods For Isotopic Source External Beam Radiotherapy

Abstract

The subject matter described herein provides methods for developing an IMRT treatment plan for a radiotherapy system. In one aspect, the method can include providing initial treatment parameters. These parameters can include a number of isotopic beams, a transmission angle for each beam, a prescribed dose for a target, and dose volume histogram constraints. The method can further include determining an initial fluence map including one or more beamlets. The initial fluence map can specify a fluence value for each beamlet. The method can further include determining a delivery sequence for the fluence values in the initial fluence map. The delivery sequence can include one or more apertures formed by the leaves of a collimator. These apertures can have a specified size constrained to substantially less than a maximum size associated with the collimator, when the isotopic beam is near a critical structure. Related apparatus and systems are also described.

1 - 20 . (canceled) 
     
     
         21 . A method comprising:
 determining an initial fluence map including one or more beamlets, the initial fluence map specifying a fluence value for each of the one or more beamlets; and   determining a first delivery sequence for the fluence values in the initial fluence map, the first delivery sequence including one or more apertures formed by a first set of one or more leaves and a second set of one or more leaves in a collimator, the one or more apertures having a specified size constrained to substantially less than a maximum size associated with the collimator when a penumbra of an isotopic beam overlaps with a critical structure.   
     
     
         22 . The method of  claim 21 , wherein the specified size is not constrained when there is no overlap between the penumbra of the isotopic beam and the critical structure. 
     
     
         23 . The method of  claim 21 , further comprising:
 providing one or more initial treatment parameters selected from a group consisting of a number of isotopic beams, isocenters for each isotopic beam, a prescribed dose for a target, a maximum dose for a critical structure, and one or more dose volume histogram constraints.   
     
     
         24 . The method of  claim 21 , wherein the specified size is substantially 2 centimeters by 2 centimeters or less. 
     
     
         25 . The method of  claim 21 , wherein the first delivery sequence further specifies a maximum number of apertures or prohibits interdigitation between the first set of one or more leaves and the second set of one or more leaves. 
     
     
         26 . The method of  claim 21  further comprising:
 beginning treatment based on the determined initial fluence map and the determined first delivery sequence. 
 
     
     
         27 . The method of  claim 21  further comprising:
 calculating one or more dose values based on the one or more apertures in the first delivery sequence using an a priori dose calculation method; 
 comparing the one or more calculated dose values with a prescribed dose for a target; and 
 determining a second delivery sequence if there is an error between the one or more calculated dose values and the prescribed dose. 
 
     
     
         28 . The method of  claim 27 , wherein the a priori dose calculation method is selected from a group consisting of a Monte Carlo simulation and a discrete ordinates method. 
     
     
         29 . The method of  claim 27 , further comprising:
 beginning treatment using a final set of apertures if there is no error between the one or more calculated dose values and the prescribed dose.   
     
     
         30 . A system comprising:
 a processor; and   a memory, wherein the processor and the memory are configured to perform operations comprising:   determining an initial fluence map including one or more beamlets, the initial fluence map specifying a fluence value for each of the one or more beamlets; and   determining a first delivery sequence for the fluence values in the initial fluence map, the first delivery sequence including one or more apertures formed by a first set of one or more leaves and a second set of one or more leaves in a collimator, the one or more apertures having a specified size constrained to substantially less than a maximum size associated with the collimator when a penumbra of an isotopic beam overlaps with a critical structure.   
     
     
         31 . The system of  claim 30 , wherein the specified size is not constrained when there is no overlap between the penumbra of the isotopic beam and the critical structure. 
     
     
         32 . The system of  claim 30 , wherein the first delivery sequence further specifies a maximum number of apertures or prohibits interdigitation between the first set of one or more leaves and the second set of one or more leaves. 
     
     
         33 . The system of  claim 30 , the operations further comprising:
 beginning treatment based on the determined initial fluence map and the determined first delivery sequence.   
     
     
         34 . The system of  claim 30 , the operations further comprising:
 calculating one or more dose values based on the one or more apertures in the first delivery sequence using an a priori dose calculation method;   comparing the one or more calculated dose values with a prescribed dose for a target; and   determining a second delivery sequence if there is an error between the one or more calculated dose values and the prescribed dose.   
     
     
         35 . The system of  claim 34 , the operations further comprising:
 beginning treatment using a final set of apertures if there is no error between the one or more calculated dose values and the prescribed dose.   
     
     
         36 . A non-transitory computer-readable medium containing instructions to configure a processor to perform operations comprising:
 determining an initial fluence map including one or more beamlets, the initial fluence map specifying a fluence value for each of the one or more beamlets; and   determining a first delivery sequence for the fluence values in the initial fluence map, the first delivery sequence including one or more apertures formed by a first set of one or more leaves and a second set of one or more leaves in a collimator, the one or more apertures having a specified size constrained to substantially less than a maximum size associated with the collimator when a penumbra of an isotopic beam overlaps with a critical structure.   
     
     
         37 . The non-transitory computer-readable medium of  claim 36 , wherein the specified size is not constrained when there is no overlap between the penumbra of the isotopic beam and the critical structure. 
     
     
         38 . The non-transitory computer-readable medium of  claim 36 , wherein the first delivery sequence further specifies a maximum number of apertures or prohibits interdigitation between the first set of one or more leaves and the second set of one or more leaves. 
     
     
         39 . The non-transitory computer-readable medium of  claim 36 , the operations further comprising:
 beginning treatment based on the determined initial fluence map and the determined first delivery sequence.   
     
     
         40 . The non-transitory computer-readable medium of  claim 36 , the operations further comprising:
 calculating one or more dose values based on the one or more apertures in the first delivery sequence using an a priori dose calculation method;   comparing the one or more calculated dose values with a prescribed dose for a target;   determining a second delivery sequence if there is an error between the one or more calculated dose values and the prescribed dose; and   beginning treatment using a final set of apertures if there is no error between the one or more calculated dose values and the prescribed dose.