Medical Physics Seminar – Monday, November 8, 2010
Bringing new PET image derived parameters to clinical practice
Dimitri Visvikis, Ph.D. (guest of Dr. Robert Jeraj)
Universite de Bretagne Occidentale, Brest, France
Prediction and follow up of therapy is of increasing interest in the field of PET clinical imaging. The PET image index predominantly used in such studies for the assessment of metabolic response is the maximum standardized uptake value corresponding to the normalized highest activity pixel value and/or the normalized mean tumor activity concentration known as the mean Standardized Uptake Value, within a region of interest around the tumor. Within the same context, it has been recently proposed that tumor functional volumes should be part of the classification criteria for response to therapy studies incorporating PET imaging. These functional tumour volume measurements can be considered separately or in combination with the overall tracer accumulation (total glycolysis volume). However all of these measurements require an accurate tumor functional volume delineation, which is still the subject of intense debate and new developments. Finally, a more detailed FDG tumor uptake characterization may be useful in predicting therapy response since FDG has been shown to be associated not only with increased metabolism, but also with several other physiological parameters such as perfusion, cell proliferation, tumor viability, aggressiveness or hypoxia all of which may in turn be responsible for tumor uptake heterogeneity. Eventually within this same context the combined utilisation of more specific radiotracers can be equally considered. The development of tools allowing the measurement of such image derived indices in an accurate and reliable fashion and preliminary results of their use in clinical research will be discussed.