Optical Monte Carlo simulations have been extensively used for the accurate modeling of light transport in scintillators for the improvement of detector designs. In the present work, a GATE Monte Carlo toolkit was used to study the effect of scintillator thicknesses and septa materials in the performance parameters evaluation of a commercially available small animal gamma-optical camera, named “γ-eye”. Firstly, the simulated γ-eye system was validated against experimental data. Then, part of the validated camera was modeled defining all of the optical properties by means of the UNIFIED model of GATE. Different CsI:Na scintillator crystals with varying thicknesses (from 4 mm up to 6 mm) and different reflector (septa) materials were simulated and compared in terms of sensitivity, light output and spatial resolution. Results have demonstrated the reliability of the model and indicate that the thicker crystal array presents higher sensitivity values, but degraded spatial resolution properties. Moreover, the use of black tape around crystals leads to an improvement in spatial resolution values compared to a standard white reflector material.

In the current work, a pix2pix conditional generative adversarial network has been evaluated as a potential solution for generating adequately accurate synthesized morphological X-ray images by translating standard photographic images of mice. Such an approach will benefit 2D functional molecular imaging techniques, such as planar radioisotope and/or fluorescence/bioluminescence imaging, by providing high-resolution information for anatomical mapping, but not for diagnosis, using conventional photographic sensors. Planar functional imaging offers an efficient alternative to biodistribution ex vivo studies and/or 3D high-end molecular imaging systems since it can be effectively used to track new tracers and study the accumulation from zero point in time post-injection. The superimposition of functional information with an artificially produced X-ray image may enhance overall image information in such systems without added complexity and cost. The network has been trained in 700 input (photography)/ground truth (X-ray) paired mouse images and evaluated using a test dataset composed of 80 photographic images and 80 ground truth X-ray images. Performance metrics such as peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM) and Fréchet inception distance (FID) were used to quantitatively evaluate the proposed approach in the acquired dataset.

Nuclear medicine (SPECT and PET) provides functional information, which is complementary to the structural. In cancer imaging radiopharmaceuticals allow visualization of cancer cells functionality, thus small cell population can be imaged. This allows early diagnosis, as well as fast assessment of response to therapy. Our system is a single head gamma camera based on an R3292 position sensitive photomultiplier tube (PSPMT), coupled to a 10cm in diameter CsI:Tl crystal. We have assessed two CsI:Tl crystals with pixel size of 2x2mm² and 3x3mm² respectively. Three collimators were tested: a) a hexagonal, 1.1mm in diameter, general purpose parallel hole collimator b) a 1mm pinhole and c) a 2mm pinhole. Systems were tested using capillary phantoms. All measurements were carried out in photon counting mode with gamma radiation produced by ^99mTc. Using the 2x2mm² crystal and the 1mm pinhole collimator - a resolution better than 1mm was achieved. This allows very detailed imaging of small animals. Using the 3x3mm² and the 2mm pinhole collimator a resolution of 1.3mm was possible with suitable sensitivity for breast imaging. Those results indicate that this system is suitable for animal and breast studies. The next step will be clinical evaluation of the camera.

The development and assessment of a readout system based on field programmable gate arrays (FPGA) for dedicated nuclear medicine cameras is presented. We have used Xilinx Spartan3E starter kit, which is one of the simplest FPGA evaluation boards. The aim of this work is to offer a simple, open source, data acquisition tool, which provides accurate results for nuclear imaging applications. The system has been evaluated using three different experimental setups: pulses from two position-sensitive photo-multipliers (PSPMTs) and a silicon photo-multiplier (SiPM) were recorded, using ^99mTc sources. Two dual channel, external, 12 bit analog to digital converters with a sampling rate of 1 Msps per channel were used. The tool was designed using Xilinx's embedded development kit and was based in Xilinx's Microblaze soft-core processor. A reference multiparameter-based data acquisition system using nuclear instrumentation modules was used for the evaluation of the proposed system. A number of tests were carried out to assess different algorithms for pulse maximum estimation and Gaussian fitting provided optimal results. The results have shown that the FPGA data acquisition system (i) provides accurate digitization of the PSPMT anode signals under various conditions and (ii) gives similar energy spectra when SiPMs are used.