@CONFERENCE\{IMM2007-05222,
    author       = "B. B{\"{o}}dvarsson and L. K. Hansen and C. Svarer and G. M. Knudsen",
    title        = "{NMF} on positron emission tomography",
    year         = "2007",
    keywords     = "{NMF,} Positron emission tomography, Brain",
    booktitle    = "International conference on acoustics, speech and signal processing 2007, {ICASSP}.",
    volume       = "",
    series       = "",
    editor       = "",
    publisher    = "",
    organization = "",
    address      = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/5222-full.html",
    abstract     = "In positron emission tomography, kinetic modelling of brain
tracer uptake, metabolism or binding requires knowledge of
the cerebral input function. Traditionally, this is achieved
with arterial blood sampling in the arm or as shown in [1] by
non-invasive {K-}means clustering. We propose anothermethod
to estimate time-activity curves (TAC) extracted directly from
dynamic positron emission tomography (PET) scans by nonnegative
matrix factorization (NMF). Since the scaling of the
basis curves is lost in the {NMF} the estimated {TAC} is scaled
by a vector A which is calculated from the {NMF} solution.
The method is tested on a [18F]-Altanserin tracer ligand data
set consisting of 5 healthy subjects. The results from using {K-}means
clustering and {NMF} are compared to a sampled arterial
 {TAC}. The comparison is done by calculating the correlation
with the arterial sampled {TAC}."
}