Forward planning

Forward planning is a technique used in external-beam radiotherapy to produce a treatment plan. In forward planning, a treatment oncologist places beams into a radiotherapy treatment planning system which can deliver sufficient radiation to a tumour while both sparing critical organs and minimising the dose to healthy tissue. The required decisions include how many radiation beams to use, which angles each will be delivered from, whether attenuating wedges be used, and which multileaf collimator configuration will be used to shape the radiation from each beam.

Once the treatment planner has made an initial plan, the treatment planning system calculates a predicted dose to the patient. The information from a prior CT scan of the patient allows more accurate modeling of the behaviour of the radiation as it travels through the patient's tissues. Different dose prediction models are available, including pencil beam, cone beam and monte carlo simulation, with precision versus time being the relevant trade-off.

This type of planning is used for the majority of external-beam radiotherapy treatments, but is only sufficiently adept to handle relatively simple cases—cases in which the tumour has a simple shape and is not near any critical organs. For more sophisticated plans, inverse planning is used to create a intensity-modulated treatment plan.