title: Combining MRI with PET for partial volume correction improves image-derived input functions in mice.
abstract: Accurate kinetic modelling using dynamic PET requires knowledge of the tracer concentration in plasma, known as the arterial input function (AIF). AIFs are usually determined by invasive blood sampling, but this is prohibitive in murine studies due to low total blood volumes. As a result of the low spatial resolution of PET, image-derived input functions (IDIFs) must be extracted from left ventricular blood pool (LVBP) ROIs of the mouse heart. This is challenging because of partial volume and spillover effects between the LVBP and myocardium, contaminating IDIFs with tissue signal. We have applied the geometric transfer matrix (GTM) method of partial volume correction (PVC) to 12 mice injected with18F-FDG affected by a Myocardial Infarction (MI), of which 6 were treated with a drug which reduced infarction size [1]. We utilised high resolution MRI to assist in segmenting mouse hearts into 5 classes: LVBP, infarcted myocardium, healthy myocardium, lungs/body and background. The signal contribution from these 5 classes was convolved with the point spread function (PSF) of the Cambridge split magnet PET scanner and a non-linear fit was performed on the 5 measured signal components. The corrected IDIF was taken as the fitted LVBP component. It was found that the GTM PVC method could recover an IDIF with less contamination from spillover than an IDIF extracted from PET data alone. More realistic values of Kiwere achieved using GTM IDIFs, which were shown to be significantly different (p<0.05) between the treated and untreated groups.
authors.affiliation: Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK, CB2 0QQ ( ee244@cam.ac.uk ).
authors.forename: Eleanor
authors.initials: E
authors.lastname: Evans
authors.affiliation: Wolfson Brain Imaging Centre and the Department of Medicine, University of Cambridge, Cambridge, UK, CB2 0QQ ( gb396@cam.ac.uk ).
authors.forename: Guido
authors.initials: G
authors.lastname: Buonincontri
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Suite 2301, Charlestown, MA, 02129 ( davidizq@nmr.mgh.harvard.edu ).
authors.forename: David
authors.initials: D
authors.lastname: Izquierdo
authors.affiliation: Department of Medicine, University of Cambridge and is now at Oregon Health and Science University, Portland, OR, 97239 ( cm618@medschl.cam.ac.uk ).
authors.forename: Carmen
authors.initials: C
authors.lastname: Methner
authors.affiliation: Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK, CB2 0QQ ( rch20@cam.ac.uk ).
authors.forename: Rob C
authors.initials: RC
authors.lastname: Hawkes
authors.affiliation: Department of Physics, University of Cambridge, Cambridge, UK, CB3 0HE ( rea1@cam.ac.uk ).
authors.forename: Richard E
authors.initials: RE
authors.lastname: Ansorge
authors.affiliation: Member of the Department of Medicine, University of Cambridge, Cambridge, UK, CB2 0QQ ( tk382@medschl.cam.ac.uk ).
authors.forename: Thomas
authors.initials: T
authors.lastname: Krieg
authors.affiliation: Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK, CB2 0QQ ( tac12@cam.ac.uk ).
authors.forename: T Adrian
authors.initials: TA
authors.lastname: Carpenter
authors.affiliation: Member of both the Wolfson Brain Imaging Centre, and the Behavioural and Clinical Neurosciences Institute, University of Cambridge, Cambridge, UK, CB2 3EB ( sjs80@cam.ac.uk ).
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Sawiak
keywords: Arterial input function; Geometric transfer matrix; MRI; partial volume correction; small animal PET