We present and evaluate the application of the "Reconstructed Image from Simulations Ensemble" (RISE), a novel tomographic image reconstruction method, in infrared tomography. We demonstrate that established methods of photon emission tomography, widely used with penetrating ionizing radiation, are applicable to infrared radiation. RISE, the method of choice, employs statistical physics concepts and utilizes Monte Carlo techniques to construct the imaged object from its infrared planar projections. The validity of the InfraRed Emission Tomographic (IRET) method is demonstrated, and the efficacy of RISE is evaluated with A) simulated data and B) experimental sets of infrared projections obtained from a thermal phantom with an infrared camera. For the simulation studies presented, the reconstructed images obtained with RISE and the well -known Algebraic Reconstruction Technique (ART) and Maximum Likelihood Expectation Maximization (MLEM) method were evaluated using well-established metrics.

The combination of two imaging modalities in a single agent has received increasing attention during the last few years, since its synergistic action guarantees both accurate and timely diagnosis. For this reason, dual-modality contrast agents (DMCAs), such as radiolabeled iron oxide (namely Fe3O4) nanoparticles, constitute a powerful tool in diagnostic applications. In this respect, here we focus on the synthesis of a potential single photon emission computed tomography/magnetic resonance imaging (SPECT/MRI) DMCA, which consists of Fe3O4 nanoparticles, surface functionalized with 2,3-dicarboxypropane-1,1-diphosphonic acid (DPD) and radiolabeled with 99mTc, [99mTc]Tc-DPD-Fe3O4. The in vitro stability results showed that this DMCA is highly stable after 24 h of incubation in phosphate buffer saline (~92.3% intact), while it is adequately stable after 24 h of incubation with human serum (~67.3% intact). Subsequently, [99mTc]Tc-DPD-Fe3O4 DMCA was evaluated in vivo in mice models through standard biodistribution studies, MR imaging and gamma-camera imaging. All techniques provided consistent results, clearly evidencing noticeable liver uptake. Our work documents that [99mTc]Tc-DPD-Fe3O4 has all the necessary characteristics to be a potential DMCA.

The sensitivity and the spatial resolution of a small field y-Camera system based on a Position Sensitive PhotoMultiplier Tube (PSPMT) on a tomographic level are examined in this study. A cylindrical Gel-Phantom (d=40 mm, h=50mm) with cylindro-conoidal tubes and capillaries (from 64 to 640 mm3) containing water solution of 99mTc is used as a test phantom in the present work. A total of 24 projections covering the full angle region (0°_360°) are obtained with the y-Camera system under examination. The planar information is further analyzed to reconstruct the tomographic images taking into account all off-line corrections needed to remove barreloid deformations appearing at the edges of the field-of-view. The reconstruction procedure is performed with iterative algorithms and for comparison reasons two different techniques (MLEM and accelerated ART) are used. The variety of the 99mTc_volu mes in the phantom with the given specific radioactivity and the phantom axial asymmetry, due to the different radial distances of the tubes in the gel environment, allow a realistic characterization of the system's performance on a tomographic level. Obtained experimental results for the system sensitivity and spatial resolution are presented and discussed in this work;they are also directly compared with ideal tomographic results acquired from the fully simulated y-Camera system through GATE.

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