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A lo largo de la historia de la Medicina Nuclear, se han desarrollado múltiples técnicas de diagnóstico y tratamiento de enfermedades como el cáncer. Una de ellas que sigue gozando de un gran éxito, es el diagnóstico mediante cámaras gamma pero, ¿se ha alcanzado ya su máximo potencial? [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Low field slice-selective ZTE imaging of ultra-short T2 tissues based on spin-locking" published in Scientific Reports. The correction addresses an incomplete funding section in the original article. The corrected version now includes additional support from the Generalitat Valenciana through grant CIPROM/2021/003. The authors of the article are Jose Borreguero, Fernando Galve, José M. Algarín, José M. Benlloch, and Joseba Alonso. [Extracted from the article]

Silicon photomultipliers (SiPMs) are arrays of single-photon avalanche diodes (SPADs) connected in parallel. Analog silicon photomultipliers are built in custom technologies optimized for detection efficiency. Digital silicon photomultipliers are built in CMOS technology. Although CMOS SPADs are less sensitive, they can incorporate additional functionality at the sensor plane, which is required in some applications for an accurate detection in terms of energy, timestamp, and spatial location. This additional circuitry comprises active quenching and recharge circuits, pulse combining and counting logic, and a time-to-digital converter. This, together with the disconnection of defective SPADs, results in a reduction of the light-sensitive area. In addition, the pile-up of pulses, in space and in time, translates into additional efficiency losses that are inherent to digital SiPMs. The design of digital SiPMs must include some sort of optimization of the pixel architecture in order to maximize sensitivity. In this paper, we identify the most relevant variables that determine the influence of SPAD yield, fill factor loss, and spatial and temporal pile-up in the photon detection efficiency. An optimum of 8% is found for different pixel sizes. The potential benefits of molecular imaging of these optimized and small-sized pixels with independent timestamping capabilities are also analyzed. [ABSTRACT FROM AUTHOR]

Options for optimizing the energy and spatial resolution of gamma-ray imaging detectors based on thick, monolithic crystals shaped like flat-topped pyramids were studied. Monte Carlo simulations were made of the scintillation light transport for evaluating the effect of four parameters on the energy resolution, the spatial resolutions, and the depth of interaction (DOI) resolution of the gamma-ray imaging detector. These four parameters are: the reflectivity of the surface coating; the scatter mean free path; the absorption mean free path of the scintillation light; and the angle that defines the inclination of the sides of the pyramidal frustum. In real detectors, the values for the mean free paths for optical photons are normally not known. We estimated these by comparing MC simulations of detector resolutions to measurements for three gamma-ray imaging detectors with LYSO and LSO from different suppliers and with different surface coatings and geometries. The gamma-ray imaging detector measures the energy, centroids, and depth of interaction of the gamma-ray. DOI enhanced charge dividing readouts were used to measure the depth of interaction. [ABSTRACT FROM AUTHOR]

We have developed a new device that allows precise guided surgery through gamma-camera images in real time. It consists of a portable mini gamma camera combined with an image guided surgery system. We call this new instrument the "Gamma Functional Navigator." The small gamma camera has been built by our group and has a spatial resolution of about 2 mm. The position and orientation of the gamma camera and the surgical instruments is determined by the navigator through infrared reflectors. A software program combines the images obtained by the gamma camera at two different positions to form a stereoscopic image of the object under study. We have focused our interest, as a starting point, to the simplest problem of quasi-punctual objects, such as lymph nodes or small tumors. We have tested the "Gamma Functional Navigator" with different phantoms finding the position of the node in 3-D space with a resolution better than 3 mm for node-camera head distances lower than 5 cm. This allows to locate and distinguish cancerous nodes from its neighbors during surgery. [ABSTRACT FROM AUTHOR]

This study aims to develop methods to design the complete magnetic system for a truly portable MRI scanner for neurological and musculoskeletal (MSK) applications, optimized for field homogeneity, field of view (FoV), and gradient performance compared to existing low-weight configurations. We explore optimal elliptic-bore Halbach configurations based on discrete arrays of permanent magnets. In this way, we seek to improve the field homogeneity and remove constraints to the extent of the gradient coils typical of Halbach magnets. Specifically, we have optimized a tightly packed distribution of magnetic Nd 2 Fe 14 B cubes with differential evolution algorithms and a second array of shimming magnets with interior point and differential evolution methods. We have also designed and constructed an elliptical set of gradient coils that extend over the whole magnet length, maximizing the distance between the lobe centers. These are optimized with a target field method minimizing a cost function that considers also heat dissipation. We have employed the new toolbox to build the main magnet and gradient modules for a portable MRI scanner designed for point-of-care and residential use. The elliptical Halbach bore has semi-axes of 10 and 14& cm, and the magnet generates a field of 87& mT homogeneous down to 5700& ppm (parts per million) in a 20-cm diameter FoV; it weighs 216& kg and has a width of 65& cm and a height of 72& cm. Gradient efficiencies go up to around 0.8& mT/m/A, for a maximum of 12& mT/m within 0.5& ms with 15& A and 15& V amplifier. The distance between lobes is 28& cm, significantly increased with respect to other Halbach-based scanners. Heat dissipation is around 25& W at maximum power, and gradient deviations from linearity are below 20% in a 20-cm sphere. Elliptic-bore Halbach magnets enhance the ergonomicity and field distribution of low-cost portable MRI scanners, while allowing for full-length gradient support to increase the FoV. This geometry can be potentially adapted for a prospective low-cost whole-body technology., (© 2024 The Author(s). NMR in Biomedicine published by John Wiley & Sons Ltd.)