AbstractID: 8063 Title: linear algebraic approach for IMRT inverse planning
The presenting IMRT optimization algorithm is based on the direct inverse operation of linear algebra. Rather than the quadratic
differences between the desired and the computed doses, the objective function is the quadratic summation of negative beam weights.
To minimize it is to search for the physically achievable beams. Instead of iterating the beam weights as the most of the optimization
algorithms do, this algorithm iterates the doses in the dose matrix within the given ranges. The dose matrix composed of the dose
voxels from arbitrary selection of dose points from target volumes and critical organs or surrounding tissue. The dose in each voxel is
already considered primary radiation as well as scatter radiation doses from all the pencil beams. The prescription for each category of
the dose point has the given dose range corresponding to the tolerances, biological indices and/or minimum and maximum dose
requirements. The process will simultaneously iterate doses in a batch of dose voxels within the given dose windows and search for
the physical achievability. From the inversely calculated beam weights, the optimization process would gradually minimize the
objective function and eventually converge to or close to the global minimum. It is a true inverse process. The algorithm described is
tested with computer simulations in a two-dimensional setup. The calculated doses are well conformed to the complex targets and
protecting the critical organs. The computer-simulated results are verified with film measurements and CORVUS verification plans
and have shown the excellent matches in the dose distributions.