Dosisplanning

Dosisplanning, often referred to as treatment planning in radiotherapy, is the process of determining the spatial distribution and timing of radiation dose to be delivered to a patient. The aim is to deliver an prescribed dose to the target volume while minimizing dose to surrounding healthy tissue and organs at risk.

The planning workflow typically starts with imaging, such as CT, sometimes supplemented by MRI or PET, to delineate the tumor and nearby critical structures. Clinicians define target volumes—often the gross tumor volume (GTV), clinical target volume (CTV), and planning target volume (PTV)—and identify organs at risk (OAR). A treatment planning system then computes dose distributions using algorithms such as pencil beam, collapsed cone, or Monte Carlo. Planners set objectives and constraints and use optimization to balance tumor coverage with sparing of normal tissue.

Plan evaluation uses metrics like dose‑volume histograms (DVH), and indices for conformity and homogeneity, to ensure the plan meets clinical requirements and institutional constraints. Common modalities include 3D conformal radiotherapy, intensity‑modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and, in some centers, proton therapy.

Delivery considerations include patient positioning, immobilization, and motion management, as well as uncertainties from setup and organ motion. Quality assurance processes verify plan accuracy and machine performance. Dosisplanning is a dynamic process, with adaptive planning possible when anatomy changes during the treatment course or dose constraints require modification.