Comparison of a cylindrical and flat panel phantom to normalize a small animal Clearpet Neuro System

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] Normalizing a PET system consists of ensuring that all lines of response joining detectors in coincidence have the same effective sensitivity (Badawi & Marsden, 1999). To obtain the effective sensitivity inside the field of view of the scanner, the deviations of the system must be corrected. These deviations such as effective crystal length variation, it depends on the scanner and detector design. Therefore, the aim of this ground study is to compare two different source phantoms, a flat panel phantom and a cylindrical phantom, in order to normalize the Small Animal ClearPET™ Neuro System. The study is based on the simulation of the Small Animal ClearPET™ Neuro System with both phantoms using GATE and using ROOT for the analysis. Both phantoms were filled with the same activity using Ga-68. Some assumptions were taken into account such as the ideal efficiency of the detectors, the omission of the random coincidences or a perfect structural alignment, among others. Using C+ scripts and ROOT, both phantoms were analyzed correcting for attenuation and for the effective crystal length variation of the detectors. Two situations were compared, on the one hand, the analysis was carried out using the sum of all transversal information (2D); on the other hand, it was used the Single Slice Rebinning algorithm (SSRB) to transform a 3D system into 2D dataset using the influence of the oblique angle. The simulated data was compared with the mathematical case which represented the activity concentration of the phantom. The result shows that the flat panel phantom discerned a distribution similar to a step function instead of the parabolic distribution of the cylindrical phantom. The comparison profiles discerned a flat distribution for both phantoms. Moreover, the geometric phenomena have a huge influence for the cylindrical phantom in comparison with the flat panel phantom. Both phantoms could be suitable for the normalization procedure but if the geometric phenomena (scattering and attenuation phenomena) are taken into account, the flat panel phantom might be more suitable for the purpose under the study conditions.