document: Direct aperture optimization : A turnkey solution for step-and-shoot IMRT IMRT treatment plans for step-and-shoot delivery have traditionally been produced through the optimization of intensity distributions -LRB- or maps -RRB- for each beam angle . The optimization step is followed by the application of a leaf-sequencing algorithm that translates each intensity map into a set of deliverable aperture shapes . In this article , we introduce an automated planning system in which we bypass the traditional intensity optimization , and instead directly optimize the shapes and the weights of the apertures . We call this approach `` direct aperture optimization . '' This technique allows the user to specify the maximum number of apertures per beam direction , and hence provides significant control over the complexity of the treatment delivery . This is possible because the machine dependent delivery constraints imposed by the MLC are enforced within the aperture optimization algorithm rather than in a separate leaf-sequencing step . The leaf settings and the aperture intensities are optimized simultaneously using a simulated annealing algorithm . We have tested direct aperture optimization on a variety of patient cases using the EGS4/BEAM Monte Carlo package for our dose calculation engine . The results demonstrate that direct aperture optimization can produce highly conformal step-and-shoot treatment plans using only three to five apertures per beam direction . As compared with traditional optimization strategies , our studies demonstrate that direct aperture optimization can result in a significant reduction in both the number of beam segments and the number of monitor units . Direct aperture optimization therefore produces highly efficient treatment deliveries that maintain the full dosimetric benefits of IMRT
doc_bio_tags: B I I O O B I O O O B I I O O O O O O O O O O O B I O O B O O O B I O O B I O O O O O O O O O O O O B I O O O O B I I O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I I O O O B O O O O B I I O O O O O O O O O B I O O B I O O O O O B I I O O O O B I I O O O O B I O O O O O O O O B I I O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O B I O O O O B I O B I I O O B I I I O O O B I I O O
extractive_keyphrases: direct aperture optimization turnkey solution imrt treatment plans intensity distributions maps beam angle optimization step intensity map deliverable aperture shapes automated planning system machine dependent delivery constraints mlc aperture optimization algorithm leaf settings aperture intensities simulated annealing algorithm patient cases dose calculation engine beam segments monitor units highly efficient treatment deliveries full dosimetric benefits
abstractive_keyphrases: step-and-shoot imrt leaf-sequencing algorithm aperture weights aperture shapes treatment delivery complexity egs4/beam monte carlo package highly conformal step-and-shoot treatment plans