Imaging is used to form a virtual model of the patient, including the tumour
Native CT is almost always used, because the physical interactions between the radiation and the tissue is the same in native CT as in radiotherapy
This means that a native CT contains the dose-absorbing properties of the tissues of the patient
By using image registration and image fusion, multiple imaging modelities may be combined, if needed
Image registration refers to “matching” multiple imaging modalities by mapping the coordinates of anatomical structures on the different modalities, so that they “match” on top of each other
Image fusion refers to displaying multiple modalities on top of each other after image registration
MRI provides good differentiation between different soft tissues
PET provides good information of functionality and metastases
Ultrasound cannot be used for treatment planning
Computer systems allow for simulation and calculation of how different radiotherapy approaches would deliver radiation to the tumour and the surrounding tissues
Modern techniques allow for even more precise radiation planning
Intensity-modulated radiation therapy (IMRT)
3D conformal radiation therapy (3DCRT)
Intensity-modulated arc therapy (IMAT)
Image-guided radiation therapy (IGRT)
Volumes in radiotheapy planning
Gross tumour volume (GTV) = the volume of the macroscopic tumour
