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MR Perfusion - Brain Tumour

MR perfusion adds haemodynamic information to conventional brain MRI by quantifying tumour microvascularity. Dynamic susceptibility contrast produces relative cerebral blood volume maps that correlate with glioma grade and angiogenesis, and it is central to distinguishing recurrent tumour from treatment-related change where conventional enhancement is ambiguous.

Indications

  • Grading of gliomas and estimation of tumour angiogenesis
  • Differentiating recurrent/progressive tumour from treatment-related change (pseudoprogression, radiation necrosis)
  • Distinguishing neoplastic from non-neoplastic enhancing lesions (e.g. tumefactive demyelination, abscess)
  • Guiding stereotactic biopsy to the most malignant (highest rCBV) region
  • Assessing response to anti-angiogenic and chemoradiation therapy
  • Characterising suspected lymphoma versus high-grade glioma

Contraindications & Cautions

  • Non-conditional pacemakers, ICDs, neurostimulators and ferromagnetic aneurysm clips
  • Cochlear implants and unstable metallic intra-ocular foreign bodies
  • Gadolinium caution with eGFR <30 mL/min/1.73 m2 (NSF risk); ASL is a contrast-free alternative
  • Severe claustrophobia without sedation
  • Pregnancy: avoid gadolinium; consider arterial spin labelling if perfusion is essential

Patient Preparation

  • MRI safety screening and removal of ferromagnetic objects
  • Large-bore intravenous access and a power injector for a tight contrast bolus
  • For DSC, consider a gadolinium preload dose to reduce contrast-leakage (T1) error in enhancing tumours
  • Explain the need for stillness during the dynamic acquisition
  • Review prior imaging and treatment history to frame recurrence-versus-necrosis questions

Technique & Parameters

  • Dynamic susceptibility contrast (DSC): rapid T2*-weighted gradient-echo EPI acquired continuously through a power-injected gadolinium bolus
  • Preload/leakage correction to mitigate signal error from blood-brain barrier breakdown
  • Generation of relative cerebral blood volume (rCBV) and relative cerebral blood flow maps, normalised to contralateral normal white matter
  • Dynamic contrast-enhanced (DCE) T1 perfusion for permeability metrics (Ktrans) where available
  • Arterial spin labelling (ASL) for a contrast-free cerebral blood flow map
  • Co-registration with conventional pre- and post-contrast T1, T2/FLAIR and DWI for anatomical correlation

Systematic Review

  • Confirm technical adequacy: bolus timing, susceptibility artefact and adequate normalisation region
  • Place regions of interest in the solid enhancing tumour, avoiding vessels, haemorrhage and calcification
  • Measure maximum rCBV and normalise to contralateral normal white matter
  • Correlate high-rCBV foci with enhancing and non-enhancing (FLAIR) components
  • Assess the DSC signal-intensity-time curve for return to baseline (leakage) versus overshoot
  • Integrate with DWI, spectroscopy and conventional sequences before concluding

Key Findings & Significance

  • High-grade glioma: markedly elevated maximum rCBV in the enhancing tumour reflecting neovascularity
  • Low-grade glioma: relatively low rCBV (with caution for oligodendroglial tumours which can have elevated rCBV)
  • Tumour recurrence/progression: elevated rCBV in the enhancing region
  • Radiation necrosis/treatment change: low rCBV with a low signal-recovery (leakage) curve
  • Tumefactive demyelination: relatively low rCBV despite avid enhancement, aiding differentiation from tumour
  • Cerebral abscess: low rCBV rim with central restricted diffusion, unlike a necrotic high-rCBV tumour

Differential Considerations

  • Enhancing lesion with high rCBV: high-grade glioma, metastasis, recurrent tumour
  • Enhancing lesion with low rCBV: radiation necrosis, tumefactive demyelination, abscess, subacute infarct
  • Lymphoma: variable, often modest rCBV with a characteristic DSC leakage overshoot pattern
  • Peritumoural high FLAIR signal: infiltrative tumour (raised rCBV) versus vasogenic oedema (low rCBV) around a metastasis
  • Post-treatment enhancement: pseudoprogression versus true progression

Pearls & Pitfalls

  • rCBV must be normalised to contralateral normal-appearing white matter for meaningful comparison
  • Leakage correction or a preload dose is essential in enhancing tumours to avoid underestimating rCBV
  • Elevated peritumoural rCBV favours infiltrative glioma over a well-circumscribed metastasis
  • Perfusion is an adjunct: always integrate rCBV with conventional MRI, diffusion and spectroscopy
  • Sample the highest-rCBV region to guide biopsy and avoid undersampling the most aggressive tumour component

Structured Report

  • State field strength, perfusion technique (DSC/DCE/ASL) and whether preload/leakage correction was applied
  • Report normalised maximum rCBV and its relation to enhancing and non-enhancing tumour
  • Give an interpretation regarding grade or recurrence-versus-treatment change
  • Correlate with conventional sequences, diffusion and spectroscopy
  • Provide an impression with recommendation for biopsy target, follow-up or multidisciplinary discussion

References

  • Boxerman JL, et al. Consensus recommendations for a dynamic susceptibility contrast MRI protocol for use in high-grade gliomas. Neuro-Oncology 2020
  • Essig M, et al. Perfusion MRI: the five most frequently asked technical questions. AJR
  • Radiographics: MR perfusion imaging of brain tumours (DSC, DCE, ASL)
  • ASFNR recommendations for clinical performance of MR perfusion in neuro-oncology

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.