Relationships between amyloid levels,glucose metabolism,morphologic changes in the brain and clinical status of patients with Alzheimer’s disease

Annals of Nuclear Medicine - The current study was conducted to improve the understanding of relationships between regional cortical amyloid load, glucose metabolism, cortical morphology (volume),...     

Effects of point spread function-based image reconstruction on neuroreceptor binding in positron emission tomography study with [<Superscript>11</Superscript>C]FLB 457

The ordered subset expectation maximization with a point spread function (OSEM-PSF) was developed to improve the spatial resolution of reconstructed positron emission tomography (PET) images and has been reported to improve the contrast of hot spots in PET studies for oncology. However, in neuroreceptor imaging, the regional radioactivity concentration changes dynamically during the scan, and the effects of the PSF may differ among various radioligands or quantification methods. In this study, we investigated the effects of the PSF on quantification in PET studies with [¹¹C]FLB 457 of dopamine D₂ receptors, using both phantom and human data acquired by the Siemens Biograph 16 imaging platform. In the phantom studies, we evaluated the hot contrast recovery coefficient (HCRC) for variously sized hot spheres and the linearity between the measured and true radioactivities in OSEM-PSF images. Next, in the human studies with [¹¹C]FLB 457, radioactivity concentrations and binding potentials for the cerebral cortex and thalamus were compared between images reconstructed with and without PSF. In the phantom studies, the OSEM-PSF images showed a better HCRC compared to images without PSF, and they showed a good linear correlation with true radioactivity. In the human studies, the radioactivity concentration increased especially in small regions with high accumulation of [¹¹C]FLB 457 when the PSF was included. However, little difference in the binding potentials was observed for the target regions between both types of reconstructed images. In conclusion, PSF-based reconstruction reduced the spill-over phenomena in small hot regions; however, it caused no increase in the binding potentials in the [¹¹C]FLB 457 studies.     

Lesson learned from Co-60 accident in Thailand

The causes and consequences of a Co-60 radiation accident in Samutprakarn Province, Thailand, were scrutinized to learn lessons aimed at preventing future radiation accidents. "Orphan sources" may end up in scrapyards. An out-of-use Co-60 medical teletherapy source, left unattended in a disused parking area belonging to a Medical Dealer, was stolen and sold to a scrap dealer in Samutprakarn Province at the end of January 2000. Because of its valuable appearance, a number of workers in the scrap trade who were not aware of radiation hazards managed to dismantle all parts. The Co-60 source was removed and left unshielded among pieces of scrap metal in the yard of the scrap shop. Some workers immediately became sick. Eighteen days later when they went to a local hospital their symptoms were recognized as radiation sickness and the incident was reported to the Office of Atomic Energy for Peace (OAEP) in Thailand. The unshielded source, with an estimated activity of 15.7 TBq (425 Ci), was retrieved soon after by an emergency team and placed in safe storage at the OAEP premises. Ten victims developed radiation sickness symptoms, of which three died soon after the accident. The accident alarmed the public, and has raised national concerns. The accident is similar in some ways to the 1987 radiation accident at Goiania, Brazil, involving a Cs-137 radiotherapy source. If not properly disposed of orphan radiation sources can lead to serious injury or even death. The accident highlights the need for security of spent high activity sources and the importance of regulatory controls.