Issues in optimization for planning of intensity-modulated radiation therapy

The clinical use of intensity-modulated radiation therapy (IMRT) is expanding rapidly in academic and, more recently, in community-based radiotherapy centers due to a high level of clinician interest, improving reimbursement patterns, and the availability of the tools required to plan and deliver IMRT plans. These tools include inverse planning optimization algorithms and linear accelerator control systems with automated, multifield delivery capabilities. The hazards of this new technology are due primarily to the nonintuitive nature of the inverse planning process and the highly complex methods of delivery required for IMRT dose delivery. Important efforts are being made to define the required quality assurance for these computer-optimized IMRT plans and to find ways to reduce their complexity without reducing the quality of the resulting plans. By minimizing the complexity of these dose plans, one also minimizes the treatment time and the probability of dose delivery errors. Methods of optimization and evaluation of dose plans and practical considerations in inverse planning are discussed. In addition, this article points out the potential hazards of inverse-planned IMRT and discusses methods by which the complexity of these plans might be reduced.