Image contrast improvement with local weighting corrections from organ bio-distribution information by external TLD measurement in PET studies

Image contrast is frequently affected by the high radioactivity uptakes of source organs such as bladder and GI track in [F-18]FDG PET studies. Certain important tumors neighboring to these organs are potentially mis-diagnosed. The study is to propose a new approach to improve the image contrast by applying the local weighting factors obtained from the biodistribution information of the source organs. The biodistribution information is accurately evaluated from external exposure measurements with thermoluminescence dosimeters (TLD). A number of TLDs are attached on the body surfaces, just above the source organs during the clinical PET study, and the body-surface doses of the organs are then accumulated. As the body-surface doses are associated with the cumulated activities from the source organs, the organ biodistribution may be further calculated with the aids of a mathematical phantom and an inverse unfolding transform technique. A local weighting correction algorithm is developed, based on the organ biodistribution information, and applied to the whole body PET images. The algorithm is a local suppression technique assigning suppression weightings to the regions according to the levels of radioactivity uptake. From the phantom study, the image contrast is improved, and the proposed algorithm could be potentially applicable to the prostate lesion detection from high bladder [F-18]FDG uptake environment.