Stroke-imaging

CTP is a relatively recent development in acute stroke imaging that is already in routine clinical use in many centers. CTP and MRP are similar in that both techniques are based on rapid serial image acquisition during intravenous injection of a bolus of contrast material. In both techniques, measurements of density over time (for CTP) or signal intensity over time (for MRP) are converted to contrast agent-versus-time curves, and these are processed in similar ways to yield the same perfusion measurements (most often CBV, CBF, and MTT). Example CTP images are shown in Figure 2.12. 

Researchers are actively at work improving both the speed of ASL sequences and the quality of the resulting images, and ASL may prove an important acute stroke imaging technique in the future. 

Sodium imaging is relatively time consuming and cannot be performed on standard clinical scanners without specialized hardware and software upgrades. Nevertheless, the unique physiologic information provided by sodium imaging may make this technique an important tool in acute stroke imaging in years to come. 

If there is a systematic (i.e., highly ordered) tissue substructure such as in white matter, diffusion is usually more restricted in one than in another direction, i.e., the molecular mobility of water is not the same in all directions. In white matter, diffusion is less restricted parallel to than perpendicular to fiber tracts. If diffusion is different along various directions, then it is termed anisotropic diffusion. In stroke imaging the avoidance of the confounding effects of anisotropy is a common goal. However,... 

The idea of a book on stroke was conceived at Heidelberg many years back. Fortunately, this idea never led to anything had the book been written then, it would have been obsolete at the time of publication. The present book, which contains all the dramatic advances in MR stroke imaging that have occurred in recent years plus pertinent information on spinal stroke, is not likely to have this fate. Rather, it will soon be found on many desks and bookshelves, because clinicians and scientists interested in stroke will quickly recognize its eminent qualities well designed, well written, and highly instructive. 

Stroke magnetic resonance imaging is accurate in hyperacute intracerebral hemorrhage a multicenter study on the validity of stroke imaging. Stroke 35 502-506... 

Fiehler J, Albers GW, Boulanger JM for the MR Stroke Group (2007). Bleeding Risk Analysis in Stroke Imaging before thromboLysis (BRASIL) pooled analysis of Tjweighted magnetic resonance imaging data from 570 patients. Stroke 38 2738-2744... 

Contrast Administration. The cine acquisition of CTP forms the final step in the acute stroke imaging evaluation. With dynamic, quantitative CTP, an additional contrast bolus of 35 5 mL is administered via power injector (at a rate of 7 mL/s), with a saline chaser of 20 0 mL at the same injection rate. The contrast used should be of high concentration, typically 350-370 g/dL of iodine, for optimal signal-to-noise ratio for perfusion maps calculation. 

Commercial software suppliers use different mathematical methods. In the past some have incorporated the maximal slope method although new versions are frequently released and the reader is advised to check for the most up-to-date software from each vendor. Others have typically used deconvolution techniques, which, although theoretically superior to nondeconvolution methods - as has already been and will again be noted, the full clinical implication of using these different models has yet to be established and standardized by the stroke imaging community. 

An important goal of advanced stroke imaging is to provide an assessment of ischemic tissne viability that transcends an arbitrary clock-time [180-182], The... 

Fig. 12.1 Boston Acute Stroke Imaging Scale (BASIS). This dichotomous instrument classifies ischemic stroke patients as either major or minor strokes based on whether there is occlusion or evidence of recent occlusion of the cerebral arteries shown in the illustration. The arteries include the terminal ICA, proximal MCA and the basilar artery (BA). Adapted from Torres-Mozqueda et al. [4]...

OR 0.44, p=0.04). Another study of 480 patients demonstrated that patients with major strokes secondary to PAO classified according to the Boston Acute Stroke Imaging Scale or BASIS accounted for all the deaths, had longer ICU and hospital stays, and were more likely to be discharged to a rehabilitation facility (all outcomes, p< 0.0001) [29]. Although major strokes comprised less than one third of the cohort, they accounted for 60% of the total in-hospital costs. 

Torres-Mozqueda F, He J, Yeh IB et al (2008) An acute ischemic stroke classification instrument that includes CT or MR angiography the Boston Acute Stroke Imaging Scale. AJNR Am J Neuroradiol 29 1111-1117... 

SchelUnger PD, Fiebach JB, Mohr A et al (2001) Thrombolytic therapy for ischemic stroke-a review. Part Il-Intra-arterial thrombolysis, vertebrobasilar stroke, phase IV trials, and stroke imaging. Crit Care Med 29 1819-1825... 

Clinical Applications of Neurovascular MDCT 126 10.3.1 Comprehensive Stroke Imaging 126... 

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