Brain tumor protocol (MRI)

MRI protocol for brain tumour assessment is a group of MRI sequences put together to best approach CNS tumours in general.

Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutional protocols, patient factors (e.g. allergy) and time constraints. 

Sequences

A good protocol for this purpose involves at least:

• T1 weighted
  • plane: axial and sagittal (or volumetric 3D)
  • sequence: fast-spin echo (T1 FSE) or gradient (T1 MPRAGE)
  • purpose: anatomical overview, which includes the soft tissues below the base of skull
• T2 weighted
  • plane: axial
  • sequence: T2 FSE
  • purpose: evaluation of basal cisterns, ventricular system and subdural spaces, evaluation of vasogenic oedema, and good visualisation of flow-voids in vessels
• FLAIR
  • plane: axial
  • sequence: FLAIR
  • purpose: assessment of white-matter tumour involvement and related vasogenic oedema
• diffusion-weighted imaging (DWI)
  • plane: axial
  • sequence: DWI: B=0, B=1000 and ADC 
  • purpose: evaluation of the tumour cellularity 
• postcontrast sequences
  • plane: axial and coronal (at least two different planes or volumetric 3D)
  • sequence: post-contrastfast-spin echo (T1 FSE) or gradient (T1 MPRAGE) . A fat-saturated sequence is considered in at least one plane, especially when tumour involves the skull's base
    • Gadolinium-based contrast agents (GBCAs) for CNS ¹:
      • gadoterate meglumine (Dotarem®)
      • gadobutrol (Gadavist®)
      • gadopentetate dimeglumine (Magnevist®)
      • gadobenate dimeglumine (MultiHance®)
      • gadodiamide (Omniscan®)
      • gadoversetamide (OptiMARK®)
      • gadoteridol (ProHance®)
    • all these GBCAs are approved by FDA at identical administered total doses of 0.1mmol/kg body weight ¹
• susceptibility weighted imaging (SWI)
  • plane: axial
  • sequence: susceptibility weighted imaging (ideal) or T2*
  • purpose: identify blood products or calcification within the tumour

When assessing gliomas it is relevant to include advanced MRI sequences, such as:

• perfusion
  • sequence:MR perfusion
  • purpose: elevation in rCBV is generally related with a high-grade tumour. It also helps in the evaluation of pseudoprogression and pseudoresponse
• spectroscopy
  • sequence: single or multivoxel spectroscopy
  • purpose: metabolic peaks characterisation