brain tumours Flashcards
pie chart approach to CNS tumours
1/3rd glial tumours
1/3rd non-glial tumours
1/3rd metastases
noon glial tumours
meningioma schwanoma pituitary pineal lymphoma
glial tumours
astrocytoma
oligodendroglioma
routine MRI
signal intensity characteristics depend on the choice of pulse sequence
there is significant overlap in the imaging appearance of different lesions
not very specific
MR spectroscopy
provides information about cerebral biochemistry in vivo
the relative concentration of metabolites is indication by the peak height (y axis)
benefits proton MR spectroscopy
spectroscopy provides biochemical information about the tumour and surrounding brain tissue
spectroscopy can guide biopsy
can differentiate between recurrent tumour and radiation necrosis
lack specificity
diffusion weighted imaging
useful for showing metastatic invasion of lymph nodes
provides insight into the cellulcar microstructure of lesions
information yelided by diffusion weighted imaging
apparent diffusion coefficient (ADC) and mean diffusivity (MDD) yeildd information about cell density, nucleus-cytoplasm ratio, viscosity etc.
diffusion tensor imaging
takes into account magnitide and direction of difusion
can be expressed mathematically by a tenor (6-dim)
DWI takes into account
only direction of diffusion
can be expressed mathematically by a vactor (3-dim)
information yeilded by DTI in neoplasmss
can tell you whether fibre tracts are deviated, infiltrated, peritumoural edema, or destoyed
CBV and astrocytic tumour grade
high grade glial brain tumours tend to have a higher CBV than low-grade lesions
perfusion imaging can be used to monitor therapy
plot of mean rCBV values against tumours grade shows increase in rCBV with increasing tumour grade
