Dose aspects of radiation therapy planning and treatment

A computer-implemented method of radiation treatment planning, the method comprising:

• determining a prescribed dose to be delivered into and across a target;
• accessing values of parameters comprising a number of beams in a plurality of beams to be directed into sub-volumes in the target, directions of the plurality of beams, and beam energies for the plurality of beams, wherein each of the beams comprises a plurality of beam segments;
• identifying any overlapping beams in the plurality of beams that have respective beam paths that overlap outside the target;
• for each beam in the plurality of beams, determining a maximum beam energy for the beam and determining beam energies for the beam segments of the beam as a percentage of the maximum beam energy for the beam;
• and
• for each overlapping beam of the overlapping beams that overlap outside the target, reducing the beam intensities for the beam segments of the overlapping beam by a factor, wherein the beam intensities for the beam segments for the plurality of beams are determined such that a cumulative dose delivered to the target satisfies the prescribed dose.

A computing system comprising:

• a central processing unit (CPU);
• and
• memory coupled to the CPU and having stored therein instructions that, when executed by the computing system, cause the computing system to execute operations to generate a radiation treatment plan, the operations comprising:
• accessing values of parameters comprising a number of beams to be directed into and across a target, directions of the beams, and beam energies for the beams;
• for each of the beams, generating a beam profile of calculated amount of dose versus depth in the target as a sequence of beam ranges;
• for each beam range, accessing a value that is assigned to the beam range according to a calculated amount of dose to be delivered by the beam range;
• determining total values for sub-volumes in the target, said determining comprising:
• for each sub-volume in the target, adding together the value for each beam region of each of the beams that are received by the sub-volume to determine a total value for the sub-volume;
• and
• adjusting the values of the parameters that affect the beam profile of each of the beams until the calculated dose inside the target is determined to be uniform across the target as measured by differences between the total values for the sub-volumes.