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The Timepix3 ASIC can be used very effectively for time resolved experiments at synchrotron facilities. We have carried out characterizations with the synchrotron beam in order to determine the time resolution and other characteristics such as the energy resolution, charge sharing and signals overlapping. The best time resolution achieved is 19 ns FWHM for 12 keV photons and 350 V bias voltage. The time resolution shows dependency on the photon energy as well as on the chip and acquisition parameters.

A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e − collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system.

This study focuses on Monte Carlo (MC) based techniques to calculate the system matrix (SM) for iterative image reconstruction of small animal PET data. For most PET scanners, the calculation of the SM requires extremely long simulation times due to the large number of image voxels, even when considering symmetries. Our goal is to determine in advance which simplifications can be done to accelerate the MC simulation without jeopardizing the accuracy of the SM. Our small animal scanner prototype was simulated using GATE. It consists of a continuous LSO crystal (42×42×10 mm 3 ) attached to Flat Panel position sensitive photomultipliers. We investigated three different radioactivity distribution models to compute the SM elements for five representative voxel positions. The results show that the simulation time required to compute the whole SM and the accuracy of the SM depend on the model and on the voxel position. In the inner region of the field of view (FOV), the model with eight point sources distributed within each voxel yields the best trade-off between simulation time and SM accuracy. Whereas, for the peripheral region of the FOV, the model with one emission point at the center of the voxel yields the best compromise. The analysis was carried out with and without having depth-of-interaction (DOI) into account. The effect of the distribution model is more significant when DOI is considered.

We have developed a mini gamma camera based on the new “flat-panel”-type multianode PSPMT (H8500) from Hamamatsu Photonics. The gamma camera is intended for intra-surgical use. The dimensions of the camera are 14 cm×7 cm×7 cm, with a useful field of view of 44 mm, and a weight of 1.2 kg. Its intrinsic resolution is better than 1.5 mm and its energy resolution is about 13%, when using a CsI(Na) scintillating crystal. We present here the most important performance features of the camera and the image reconstruction process followed. Several clinical tests, on breast cancer and melanoma patients, were performed and compared with conventional cameras, to check the quality of the camera. For an administered dose of 3 mCi of 99mTc around the tumour, 1 h before the lymphscintigraphy, we take high-quality images of the nodes in about 30 s using a pinhole collimator.

A portable gamma camera based on the multianode technology has been built and tested. The camera consists in optically coupling four “Flat Panel” H8500 PSPMTs to a 100×100×4 mm 3 CsI(Na) continuous scintillation crystal. The dimensions of the camera are 17×12×12 cm 3 including the pinhole collimator and it weighs a total of 2 kg. Its average spatial resolution is 2 mm, its energy resolution is about 15%, and it shows a field of view of 95 mm. Because of its portability, its FOV and its cost, it is a convenient choice for osteological, renal, mammary, and endocrine (thyroid, parathyroid and suprarenal) scintigraphies, as well as other important applications such as intraoperatory detection of lymph nodes and surgical oncology. We describe the simulations performed which explain the crystal choice, the mechanical design of the camera and the method of calibration and algorithms used for position, energy and uniformity correction. We present images taken from phantoms. We plan to increase the camera sensitivity by using a four-holes collimator in combination with the MLEM algorithm, in order to decrease the exploration time and to reduce the dose given to the patient.