Medical imaging 2003: image processing, pts 1-3 vol:5032 pages:986-994
PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)
Medical Imaging 2003 Conference SAN DIEGO, CA, FEB 17-20, 2003
The accurate quantification of brain perfusion for emission computed tomography data (PET-SPELT) is limited by partial volume effects (PVE). This study presents a new approach to estimate accurately the true tissue tracer activity within the grey matter tissue compartment. The methodology is. based on the availability of additional anatomical side information and on the assumption that activity concentration within the white matter tissue compartment is constant. Starting from an initial estimate for the white matter activity and for the grey matter activity, the true tracer activity within. the grey matter tissue compartment is estimated by a ML-EM-algorithm. During the updating step the constant activity concentration within the white matter compartment is modelled in the forward projection in order to reconstruct the true activity distribution within the grey tissue compartment, hence reducing partial volume averaging. On his turn, the estimate for the constant activity in the white matter tissue compartment is updated based on the new estimated activity distribution in the grey matter tissue compartment. We have tested this methodology by means of computer simulations. A T1-weighted MR brainscan of a patient was segmented into white matter, grey matter and cerebrospinal fluid, using the segmentation package of the SPM-software (Statistical Parametric Mapping). The segmented grey and white matter were used to simulate a SPELT acquisition; modelling the noise and the distance dependant detector response:: Scatter and attenuation were ignored. Following the above described strategy, simulations have shown it is possible to reconstruct the true activity distribution for the grey matter tissue compartment (activity/tissue volume), assuming constant activity in the white matter tissue compartment.