Perfusion-weighted imaging

Wu O, 0stergaard L, Sorensen AG. Technical aspects of perfusion-weighted imaging. 

Yamada K, Wu O, Gonzalez RG et al (2002) Magnetic resonance perfusion-weighted imaging of acute cerebral infarction effect of the calculation methods and underlying vascu-lopathy. Stroke 33 87-94... 

Fig. 11.6. A patient with acute ischemic stroke where MRI shows a perfusion-diffusion mismatch with a relatively small area of high signal on diffusion-weighted imaging (a) but a large area of reduced perfusion on perfusion weighted imaging (b).

Two patterns of DWI and perfusion-weighted imaging abnormalities have been observed in acute ischemic stroke ... 

Despite the limitations described above, there is evidence that perfusion CT values correlate with angiographic findings and DWI/perfusion-weighted imaging changes, can predict infarction and clinical outcome (Nabavi et al. 2002 Meuli 2004 Parsons et al. 2005 Wintermark et al. 2007) and may be able to identify patients likely to benefit from thrombolysis. 

The use of brain imaging to select patients for thrombolysis is discussed in detail in Ch. 11. Assuming equal access to diffusion-weighted/perfusion-weighted imaging and CT perfusion, decisions regarding optimum imaging use can be dictated by time elapsed since stroke onset and symptom severity. 

Perfusion MRI In contrast to diffusion MRI that examines the movement of fluid through tissues, perfusion MRI determines blood flow on the basis of measures of blood volume. Perfusion-weighted imaging (PWI) can determine cerebral tissue... 

Table 5.5 Advantages and disadvantages of CTP relative to MR perfusion weighted imaging (PWI)...

Fig. 5.9 Prediction of infarct growth. A 65-year-old man, improving clinically at 5 h postictus, was monitored in the Neurology ICU based on his labile blood pressure, a fixed left M2 occlusion on CTA, and a significant core/penumbra mismatch on CTP/MRP. His 24-h follow-up DWI showed a small infarction. However, 24 h after cessation of hypertensive therapy there was infarct growth into the region of penumbra. Admission CTA (top) CTP (CBV/CBF/ MTT) at 4.5 h second row) MR-perfusion weighted imaging (MR-PWI) (CBV/CBF/MTT) at 5.25 h (third row) DWI at 24 h (fourth row) and follow-up DWI at 48 h (bottom). The CTP and MR-PWI demonstrate a mismatch between the CBV (no abnormality) and the CBF/MTT penumbra (arrows). After cessation of hypertensive therapy, the DWI abnormahty grows into the region predicted by the CBF/MTT maps...

Arenillas, J.F., et al.. Prediction of early neurological deterioration using diffusion- and perfusion-weighted imaging in hyperacute middle cerebral artery ischemic stroke. Stroke, 2002. 33(9) p. 2197-203. 

Table 8.1 Gradient echo-planar perfusion-weighted imaging parameters...

Restrepo L, Jacobs MA, Barker PB, Wityk RJ. Assessment of transient ischemic attack with diffusion- and perfusion-weighted imaging. AJNR Am J Neuroradiol. 2004 25 1645-1652... 

Wu O, 0stergaard L, Koroshetz WJ, Schwamm LH, O Donnell J, Schaefer PW, Rosen BR, Weisskoff RM, Sorensen AG. Effects of tracer arrival time on flow estimates in mr perfusion-weighted imaging. Magn Reson Med. 2003 50 856-864... 

Thijs VN, Somford DM, Bammer R, Robberecht W, Moseley ME, Albers GW. Influence of arterial input function on hypoperfusion volumes measured with perfusion-weighted imaging. Stroke. 2004 35 94-98... 

Kucinski T, Naumann D, Knab R et al (2005) Tissue at risk is overestimated in perfusion-weighted imaging MR imaging in acute stroke patients without vessel recanalization. AJNR Am J Neuroradiol 26 815-819... 

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