P. M. Mendes Correia

Accurate range verification is a critical component of proton therapy, ensuring that the high dose gradients characteristic of Bragg peaks are delivered precisely to the target volume. This work presents the first experimental evaluation of the easyPET.3D, a compact and cost-effective preclinical positron emission tomography scanner, as a potential tool for quality control assessment. Homogeneous PMMA phantoms were irradiated at the Paul Scherrer Institute Gantry 1 facility using proton beam energies ranging from 138 MeV–195 MeV. The resulting 3D β + activity distributions were reconstructed and analyzed to assess the system’s spatial accuracy, stability, and sensitivity. For the intermediate energy of 160 MeV, the measured activity profile showed a high degree of agreement with Monte Carlo (GATE) simulations, with a difference of 0.24 mm in the R 50 % position. The system exhibited robust performance under varying irradiation conditions. Doubling the number of delivered protons relative to a clinically relevant value resulted in a deviation of only 0.4 mm in the calculated range, confirming the method’s reproducibility. Furthermore, the system successfully resolved distinct beam paths in a dual-energy irradiation mode, distinguishing tracks separated vertically by 10 mm and quantifying longitudinal range differences. Sensitivity tests indicated that the system is capable of detecting longitudinal phantom displacements as small as 1 mm. The relationship between expected and measured displacements followed a linear trend with a slope of 1.13, indicating a systematic overestimation of 13%, and an offset of 0.45 mm, reflecting a small baseline bias. While further optimization of detector sensitivity and reconstruction algorithms is required to reduce acquisition times for routine clinical workflows, these findings validate the potential of easyPET.3D as a promising, accessible solution for proton range verification.

Photon-counting computed tomography (PCCT) using scintillator-based detectors are emerging as a promising technique for high-resolution, energy-resolved imaging in preclinical and clinical settings. The presented work describes the development and integration of a new computed tomography (CT) approach in easyPET.3D system, a dual-axis rotational micro-positron emission tomography (PET) system. The proposed CT methodology uses the same radiation detectors used for PET to detect photon emission from radioactive sources. To investigate the performance of this CT imaging approach, simulated and experimental data were collected to assess the system’s spatial resolution and material discrimination capabilities, using an ²⁴¹Am. A PMMA and wire copper-based phantom was scanned using a fan-beam configuration. The obtained images were reconstructed using Filtered Back Projection (FBP). Reconstructed images from simulations and experimental prototype were visually and quantitatively similar. The system demonstrated the ability to detect submillimetre high-attenuation structures and differentiate materials with varying densities. Spatial resolution analysis, based on FWHM measurements of Gaussian fits, showed good agreement with physical dimensions. Improved tangential resolution was observed in experimental data when using finer angular steps enabled by the fan rotation step-motor. These results demonstrated the potential of reliable CT imaging using an ²⁴¹Am source, the easyPET’s detectors and its rotation methodology. (Patent pending: WO 2025/158418 A1).

The growing prevalence of chronic diseases, population aging, and the shift toward preventive and personalized care under Healthcare 5.0 have increased the need for continuous health monitoring beyond clinical settings. While wearable devices enable remote monitoring, their long-term use is often limited by user compliance, comfort issues, battery dependence, and disruption of daily routines. To address these limitations, unobtrusive home-based health monitoring systems have emerged, integrating sensing technologies into domestic environments and everyday objects. This review provides a system-level analysis of unobtrusive health monitoring technologies for smart homes. It examines seven major sensing approaches, including camera-, laser-, radar-, infrared-, mechanical-, bioelectrical-, and optical-based sensors, and their integration into four home environments: living areas, bathrooms, bedrooms, and home offices. For each sensing modality, the operating principles, monitored physiological parameters, representative applications, and key advantages and limitations are discussed. Overall, existing solutions reveal trade-offs among measurement accuracy, robustness in real home conditions, energy autonomy, privacy preservation, and user acceptance. Heart rate and respiratory rate are the most commonly monitored parameters, while multimodal and clinically validated systems remain limited. Although unobtrusive sensing technologies show strong potential for proactive and personalized healthcare, challenges related to accuracy, interoperability, privacy, and cost continue to hinder large-scale adoption.

Silicon Photomultipliers (SiPMs) have become an integral part of time-of-flight positron emission tomography (TOF-PET) scanners in recent years. Their excellent photodetection efficiency and fast decay time are essential in state-of-the-art timing resolutions, which have enabled improvements in image quality for TOF-PET. However, most SiPMs share a common architecture: an array of single avalanche photodiodes. This design has a limitation: each pixel requires its own quenching resistor and conductive connections, creating inactive regions that reduce the effective detection area. In this paper we explored a new type of SiPMs called the Micropixel Avalanche Photodiodes (MAPD) for the purposes of TOF-PET. These devices utilize buried pixel technology, which minimizes detector dead zones and achieves an almost 100 % fill factor. We evaluated their noise characteristics, energy resolution, and coincidence timing resolution (CTR). Our findings indicate that although the MAPD-3NM-II devices exhibit higher dark count rates, notable optical cross-talk, and a narrower overvoltage range compared to the reference Hamamatsu S14160-3015PS SiPMs, they offer superior energy resolution—improving up to 17 % at 511 keV—while maintaining competitive timing performance at the same overvoltage. In particular, with 3.8×3.8×4 mm³ LYSO crystals, the MAPD-3NM-II achieved a CTR of 336 ± 12 ps, a 5% improvement compared to Hamamatsu at the same overvoltage. Despite operating only up to 4.5 V, the MAPD-3NM-II demonstrates strong potential for TOF-PET applications, especially in scenarios prioritizing energy resolution. Further structural optimizations to reduce cross-talk and expand the operable voltage range could make this technology a competitive alternative to established SiPM architectures.

In proton therapy, a conformal and precise radiation dose is delivered to tumors, resulting in improved treatment outcomes and higher survival rates. However, the depth-dose profile (Bragg Peak) poses a significant concern for clinical applications, as even minor spatial uncertainties can lead to undesired doses in normal tissues. Imaging techniques like Positron Emission Tomography (PET) have been proposed to address this challenge. This study evaluates the suitability of the easyPET.3D system for assessing 3D proton beam profiles through Monte Carlo simulations. The primary focus is on accurately predicting the distribution of β ⁺ emitters produced in a phantom after proton beam irradiation. Simulations were performed to model the irradiation of homogeneous and heterogeneous phantoms with monoenergetic protons (energies ranging from 80 to 160 MeV) and obtain the corresponding PET images of the phantom’s irradiation. The β ⁺ production map (ground truth) generated in the phantoms showed reproducible agreement with the PET image obtained. For the energy beams simulated in this study, the relative deviation between the ground truth image and the PET 3D image was less than 14%, for every beam energy. The easyPET.3D system could also differentiate between the two materials in the heterogeneous phantom. Additionally, the distance between the Bragg peak and the maximum intensity of PET image profile obtained remained constant across all simulated proton energy beams, around 11.7 mm. This suggests that the easyPET.3D system can be used as an effective tool to assess beam quality in proton therapy by measuring the β ⁺ activation map generated in phantoms and correlate it with the beam’s profile.

The multiplicities of positive and negative pions, kaons, and unidentified hadrons produced in deep-inelastic scattering are measured in bins of the Bjorken scaling variable x , the relative virtual-photon energy y , and the fraction of the virtual-photon energy transferred to the final-state hadron z . Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam of both electric charges and a liquid hydrogen target. These measurements cover the kinematic domain with photon virtuality Q 2 > 1 ( GeV / c ) 2 , 0.004 < x < 0.4 , 0.1 < y < 0.7 , and 0.2 < z < 0.85 , in accordance with the kinematic domain used in earlier published COMPASS multiplicity measurements with an isoscalar target. The calculation of radiative corrections was improved by using the Monte Carlo generator , which results in up to 12% larger corrections in the low- x region.

Proton range verification (PRV) in proton therapy is an unmet clinical need. Prompt-gamma imaging (PGI) using thick collimators is a PRV modality that has obtained the most success to-date. The gamma detectors in such approach consist of scintillation crystals coupled to photodetectors. In this work, we report the development and use of detectors made of monolithic pure Cherenkov emitter crystals for the same purpose. We demonstrate for the first time the ability of such detector configuration to provide spatial resolution information in one direction using measurements from a collimated slit. The detector consisted of a PbF2 crystal with dimensions 25 ×25 × 10 mm coupled to a S13361-3050AE-08 array of 8x8 SiPMs from Hamamatsu. The SiPM array was connected to a row-column readout, with 8+8 channels, and triggered on the sum of the columns. Three different event reconstruction algorithms were tested: center of gravity (CoG), rise to the power (RTP), and neural-network (NN). The NN yielded the best spatial resolution, with 3.7±0.9 mm full width half maximum (FWHM) in average for all positions. CoG and RTP also showed a consistent shift with the change of position of the slit, although with more modest results, between 4 mm and 7 mm in average for all positions. This is the first characterization of monolithic pure Cherenkov emitters for Multi-MeV gamma imaging. Results are promising for this detector concept, showing that it can offer an alternative for collimated PGI in PRV with potential of sustaining high count rates, with effective background rejection, and low production costs based on the cost of primary components of the crystals.

EasyPET.3D is a preclinical positron emission tomography (PET) scanner with a unique scanning method based on two face-to-face detector modules with two axes of motion. Its performance evaluation is presented using the NEMA NU-4 standards and an animal model. Each detector module consists of a 32 × 2 pixelated cerium-doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator array with individual crystals of 2.0 × 2.0 × 30 mm3. The crystal arrays are coupled to 1.3 × 1.3 mm2 silicon photomultipliers (SiPMs). The transaxial field-of-view (FoV) is adjustable up to 48 mm in diameter, and the axial length is 73 mm. The performance characterization includes spatial resolution, sensitivity, count rate, scatter fraction (SF), and image quality (IQ) measurements. Furthermore, mice experiments were conducted to evaluate the in vivo imaging capability. Spatial resolution at the FoV centre (CFoV) in radial, tangential, and axial directions was 0.98±0.08, 0.97±0.06 and 0.94±0.08 mm, respectively. An absolute sensitivity of 0.23% was measured at CFoV. The mouse-like phantom SF was 16% (913 cps at 18 MBq). Recovery coefficients in the IQ phantom varied from 21±34% to 85±50% (1 to 5 mm diameter rods, accordingly). The uniformity was 17.6%, and spill-over ratios for water-filled and air-filled chambers were 0.49 and 0.40, respectively. EasyPET.3D geometry favours the reduction of parallax error, despite its low sensitivity. The system linearity is suitable for the low range of activities (7–8 MBq) used for mice imaging. The overall performance showed that easyPET.3D has potential for entry-level preclinical applications.