Table 4.

Summary of key considerations for DIR between various image modalities used in radiotherapy.

Image modalities	Key Considerations	Ref
CT‐pCT registration	No specific considerations extending Table 2.
CBCT‐pCT registration	Limitations of CBCT (FOV, HU accuracy, length limits) should be evaluated when estimating dose calculated on CBCT. Consider using tissue, air and bone overrides.	8
MR‐pCT registration	MR‐pCT DIR should not be used routinely with the current tools available, unless multiple users have evaluated results on both technical and clinical grounds.	11
PET‐pCT registration	Validate the consistent frame of reference between the PET and its attenuation correction CT before coupling other registrations. PET‐pCT DIR should only be performed using the intermediate registration between the attenuation correction CT and pCT.	15