Despite this change, the molecule bears sufficient similarity to glucose to be taken up by living cells in proportion to their metabolic demands. The radiation emitted by the tracer after it has been absorbed by the cells can therefore be used to construct

a map depicting the glucose demands of the different tissues. FDG-PET scans have a characteristic appearance that can facilitate the diagnosis of AD (Silverman et al. 2001; Drzezga et al. 2005). In addition, PET scans have clinical utility for discerning between AD and dementia caused by frontotemporal lobar degeneration (FTLD) (Foster et al. 2007). Several research this website studies Inhibitors,research,lifescience,medical have evaluated the utility of PET scans for diagnosing AD (Minoshima et al. 1995; Silverman et al. 2001) or for predicting the progression of MCI or AD (Chetelat et al. 2003; Drzezga et al. 2005; Landau et al. 2010, 2011; Walhovd et al., 2010). PET scans for studies such as these are often subjected to complex Inhibitors,research,lifescience,medical post-processing, such as segmentation into volumes of interest, or surface projection. The current work focuses on automatic Inhibitors,research,lifescience,medical detection of AD or elevated MCI conversion risk, making use of elementary information retrieval (IR) techniques. IR is a broad field that is concerned chiefly with the rapid selection of relevant documents from vast databases. The documents in question are traditionally text, and this has shaped many IR techniques. The simplest approach is to formulate a query as a list

of key Inhibitors,research,lifescience,medical words and to retrieve only documents that contain all of the key words. This approach does not perform well in practice, however. Another approach that is almost as simple is to arrange word

counts from numerous documents in a matrix and then to treat the rows and columns of the matrix as vectors. This permits comparison of documents and queries using simple mathematical measurements on vectors, such as Euclidean distance (a generalization of the Pythagorean theorem) and cosine similarity (a measure of the angle between two vectors that is maximal when the vectors are parallel). Inhibitors,research,lifescience,medical More typically, the term-document matrix is subjected to Rutecarpine further mathematical processing for extracting the most salient features of the data, such as singular value decomposition or latent semantic analysis (Widdows 2004). This vector-space model of information has proven to be very useful, and the possibility of extending it to retrieval of images and music is an area of active research (Casey et al. 2008; Datta et al. 2008). The diagnosis of AD (or identification of patients who meet other clinical criteria) may be approached from an IR perspective. In this case, we wish to search a database of brain images and retrieve those images that belong to patients with AD or elderly controls. Somewhat more compelling (and more difficult) is the retrieval of scans from patients with memory impairment who are destined to develop AD. The immediate problem that arises is the formulation of the query.