Table 1.

Comparison of the strengths and weaknesses of different imaging modalities for stroke

Modality	Strengths	Weaknesses
PET	Standard for ischemic penumbra delineation	Expensive
	Quantitative measurements	Limited availability Time-consuming when using certain radiotracers (such as 18F-labeled compounds) Radiation exposure Poor spatial and temporal resolution
CT Perfusion	Widely accessible	Radiation exposure
	Cheap	Contrast agent required
	Fast	Semi-quantitative, quantitation issues
SPECT	Serial measurements possible	Relatively expensive Difficult to use in emergency settings
MRI	Good spatial resolution	Time-consuming
	High sensitivity (especially diffusion imaging) Non-invasive/no radiation Great versatility and image contrasts	Expensive