RESUMO
UNLABELLED: We recently completed construction of a small-animal PET system-the MiniPET-3-that uses state-of-the-art silicon photomultiplier (SiPM) photosensors, making possible dual-modality imaging with MRI. In this article, we compare the MiniPET-3 with the MiniPET-2, a system with the same crystal geometry but conventional photomultiplier tubes (PMTs). METHODS: The standard measurements proposed by the National Electrical Manufacturers Association NU 4 protocols were performed on both systems. These measurements included spatial resolution, system sensitivity, energy resolution, counting rate performance, scatter fraction, spillover ratio for air and water, recovery coefficient, and image uniformity. The energy windows were set to 350-650 keV on the MiniPET-2 and 360-662 keV on the MiniPET-3. RESULTS: Spatial resolution was approximately 17% better on average for the MiniPET-3 than the MiniPET-2. The systems performed similarly in terms of peak absolute sensitivity (â¼1.37%), spillover ratio for air (â¼0.15), spillover ratio for water (â¼0.25), and recovery coefficient (â¼0.33, 0.59, 0.81, 0.89, and 0.94). Uniformity was 5.59% for the MiniPET-2 and 6.49% for the MiniPET-3. Minor differences were found in scatter fraction. With the ratlike phantom, the peak noise-equivalent counting rate was 14 kcps on the MiniPET-2 but 24 kcps on the MiniPET-3. However, with the mouselike phantom, these values were 55 and 91 kcps, respectively. The optimal coincidence time window was 6 ns for the MiniPET-2 and 8 ns for the MiniPET-3. CONCLUSION: Images obtained with the SiPM-based MiniPET-3 small-animal PET system are similar in quality to those obtained with the conventional PMT-based MiniPET-2.
Assuntos
Imageamento por Ressonância Magnética/métodos , Imageamento por Ressonância Magnética/tendências , Imagem Multimodal/métodos , Imagem Multimodal/tendências , Tomografia por Emissão de Pósitrons/instrumentação , Tomografia por Emissão de Pósitrons/tendências , Algoritmos , Animais , Radioisótopos de Flúor , Camundongos , Imagens de Fantasmas , Ratos , Reprodutibilidade dos Testes , Células Fotorreceptoras Retinianas Bastonetes/diagnóstico por imagem , Radioisótopos de SódioRESUMO
The positron emission tomography (PET) technique is a well-known method in nuclear medicine for molecular imaging of biochemical functions in the human body, but it can also be applied to molecular imaging of the chemical processes on the surfaces of heterogeneous catalysts. Dynamic studies of adsorption, desorption, and realignment of 11 Câ positron-emitter-labeled compounds can be performed. In the work reported herein, a small PET scanner with approximately 1.3â mm spatial resolution, originally dedicated for small-animal studies, is applied to image the location and quantitative distribution of [11 C]methanol in a catalyst bed of approximately 8â cm3 volume in three dimensions. The PET imaging technique in combination with radio-gas chromatographic analysis was also used to study different strengths of chemical bonds during catalytic processes on fresh and used Lindeâ A-type zeolites as catalysts. The PET technique has been highly developed in the last few years with higher resolution and sensitivity and improved image reconstruction algorithms. The commercial human and small-animal PET scanners have great potential for imaging of well-functioning, poorly functioning, or partially covered catalyst surfaces in academic and industrial research for the development of catalysts. High-resolution PET scanning is a great catalysis imaging technique because of both axial and radial imaging of the catalyst bed; therefore, the distribution of radioactive compounds is analyzable in the total catalyst volume.