NEMA Performance Evaluation of CareMiBrain dedicated brain PET and Comparison with the whole-body and dedicated brain PET systems

[EN] This article presents system performance studies of the CareMiBrain dedicated brain PET according to NEMA NU 2-2012 (for whole-body PETS) and NU 4-2008 (for preclinical PETs). This scanner is based on monolithic LYSO crystals coupled to silicon photomultipliers. The results obtained for both protocols are compared with current commercial whole body PETs and dedicated brain PETs found in the literature. Spatial resolution, sensitivity, NECR and scatter-fraction are characterized with NEMA standards, as well as an image quality study. A customized image quality phantom is proposed as NEMA phantoms do not fulfil the necessities of dedicated brain PETs. The full-width half maximum of the radial/tangential/ axial spatial resolution of CareMiBrain reconstructed with FBP at 10 and 100 mm from the system center were, respectively, 1.87/1.68/1.39 mm and 1.86/1.91/1.40 mm (NU 2-2012) and 1.58/1.45/1.40 mm and 1.64/1.66/1.44 mm (NU 4-2008). Peak NECR was 49 kcps@287 MBq with a scatter fraction of 48% using NU 2-2012 phantom. The sensitivity was 13.82 cps/kBq at the center of the FOV (NU 2-2012) and 10% (NU 4-2008). Contrast recovery coefficients for customizing image quality phantom were 0.73/0.78/1.14/1.01 for the 4.5/6/9/12 mm diameter rods. The performance characteristics of CareMiBrain are at the top of the current technologies for PET systems. Dedicated brain PET systems significantly improve spatial resolution and sensitivity, but present worse results in count rate measurements and scatter-fraction tests. As for the comparison of preclinical and clinical standards, the results obtained for solid and liquid sources were similar.This study was funded by the Spanish Ministry of Science, Innovation and University under grant RTC-2016-5186-1, a project co-financed by the European Union through the European Regional Development Fund (ERDF). 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PSMA-Targeted Mesoporous Silica Nanoparticles for Selective Intracellular Delivery of Docetaxel in Prostate Cancer Cells

[EN] Although docetaxel is currently broadly used in prostate cancer treatment, poor water solubility and systemic toxicity limit the dose and duration of therapy. In this context, although different nanoplatforms have been proposed to overcome these issues, selective therapy needs developing methodologies to target malignant cells and minimizing the impact on healthy tissue. We here present a novel drug delivery system obtained by covalent conjugation of docetaxel and an anti-prostate specific membrane antigen (PSMA) molecule (anti-FOLH1 monoclonal antibody, clone C803N) over mesoporous silica nanoparticles. This conjugate remains stable in physiological medium and shows high selectivity for LNCaP, a specific cell line that overexpresses PSMA. As a consequence, cell internalization is increased by 25%. Furthermore, cytotoxic activity of the targeted system increases by 2-fold with regard to nontargeted nanoparticles and by 2 orders with regard to the naked drug. Conversely, no targeting effect is observed over PC3, a nonbearing PSMA cell line. We expect that this therapeutic system shows strong potential for treating nonmetastatic prostate cancer, mostly through intraprostatic administration.Financial support from the Spanish Ministry of Economy and Competitiveness (projects MAT2015-66666-C3-2-R, TEC2016-80976-R, and SEV-2016-0683) and the Generalitat Valenciana (project PROMETEO/2017/060) is gratefully acknowledged. We appreciate the assistance of the Electron Microscopy Service of the Universitat Politecnica de Valencia.Rivero-Buceta, EM.; Vidaurre Agut, CM.; Vera Donoso, CD.; Benlloch Baviera, JM.; Moreno Manzano, V.; Botella Asuncion, P. (2019). PSMA-Targeted Mesoporous Silica Nanoparticles for Selective Intracellular Delivery of Docetaxel in Prostate Cancer Cells. ACS Omega. 4(1):1281-1291. https://doi.org/10.1021/acsomega.8b02909S128112914

Image-guided Placement of Magnetic Neuroparticles as a Potential High-Resolution Brain-Machine Interface

We are developing methods of noninvasively delivering magnetic neuroparticles™ via intranasal administration followed by image-guided magnetic propulsion to selected locations in the brain. Once placed, the particles can activate neurons via vibrational motion or magnetoelectric stimulation. Similar particles might be used to read out neuronal electrical pulses via spintronic or liquid-crystal magnetic interactions, for fast bidirectional brain-machine interface. We have shown that particles containing liquid crystals can be read out with magnetic resonance imaging (MRI) using embedded magnetic nanoparticles and that the signal is visible even for voltages comparable to physiological characteristics. Such particles can be moved within the brain (e.g., across midline) without causing changes to neurological firing

2D study of a joint reconstruction algorithm for limited angle PET geometries

[EN] Recently, a wide interest on organ-dedicated PET systems has been shown. Some of those systems present geometries that produce an incomplete sampling of the tomographic data due to limited angular coverage and/or truncation, which lead to artifacts on the reconstructed image. Moreover, they are often designed as standalone systems, which implies the absence of anatomical information to estimate the attenuation factors. In this work, we propose a joint reconstruction algorithm for estimating the activity and the attenuation factors on a limited angle PET system with time-of-flight capabilities. This algorithm is based on MLACF and uses literature linear attenuation coefficients in a known tissue-class region to obtain an absolute quantification. We evaluate the algorithm through simple 2D simulations for different TOF resolutions and angular coverage. The results show that with good TOF resolution quantitative PET imaging can be achieved even with aggressive angular limitation.Vergara, M.; Rezaei, A.; Rodríguez-Álvarez, MJ.; Benlloch Baviera, JM.; Nuyts, J. (2021). 2D study of a joint reconstruction algorithm for limited angle PET geometries. KU Leuven. 103-106. http://hdl.handle.net/10251/180066S10310