MRgRT

What is the main benefit of an MRI as compared to a CT?

• It provides a better estimate of the Hounfield numbers.

• It provides better contrast between soft-tissue structures

• It is geometrically robust compared to CT

The electron return effect...

• ..cannot be compensated in treatment planning

• 
  ..only happens at 1.5T and higher field strengths

  
  

• .is most prominent at tissue-air and tissue-lung-tissue interfaces

cine-MRI based beam gating...

• ..can facilitate smaller margins

• ..requires implantation of fiducial markers in or near the tumor

• ..is poorly tolerated by the majority of patients

Which one is CORRECT about MR-Linac?

• SAD 143.5 cm

• The immobilized devices should made from carbon fiber.

• maximum field size 40x40cm2

• Only VMAT available

What are the sources of distortion in MRI?

• Main magnetic field

• patient

• gradient non-linearity

• All of above

Which of the following fields should be considered in MRI safety assessment?

• The main magnetic field and the gradient field

• The radio frequency field

• All of the above

Which one is CORRECT about Motion Monitoring (MM) in MR-Linac

• 3D Cine

• balanced steady-state free precession

• Real-time MRI guidance causes more harm to the surrounding tissues during treatment

• image contrast is T2w

Which one is not an advantage of MR-Linac?

• Possibility to adapt the treatment plan daily

• superior visualization of the target volume.

• superior visualization of OAR

• Shorter in-room time compared to CBCT based linacs