Intensity modulated radiation therapy (IMRT) has revolutionized the treatment planning process. We can now produce treatment plans for complex target shapes and obtain remarkable dose conformity while respecting the tolerance doses to critical structures. While the emphasis has been given in the implementation of faster, more efficient, and more comprehensive optimization algorithms to solve the inverse problem, some progress has also been made in the implementation of accurate dose calculation algorithms. The convolution/superposition algorithm is the most popular photon dose engine used in treatment planning, while fast, pencil beam like implementations continue to be popular with IMRT. The Monte Carlo algorithm although available, is becoming an option as a secondary dose verification rather than as the principal optimization engine for IMRT planning, primarily due to calculation speed issues. In this presentation we will discuss the algorithms that have historically been used for photon beam treatment planning with emphasis on the convolution and Monte Carlo based methodologies and their application in IMRT planning. Clinical examples will also be presented to demonstrate the use and outcome of dose calculations in homogeneous and heterogeneous media. Educational Objectives: 1. Review of dose calculation algorithms for photon beams. 2. Demonstrate the effect of dose algorithm selection in IMRT planning.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging