http://hdl.handle.net/10016/9269 2013-06-20T07:53:53Z http://hdl.handle.net/10016/16787 Title: A recurrent nonsense mutation occurring as a de novo event in a patient with recessive dystrophic epidermolysis bullosa Author(s): Cuadrado-Corrales, N.; Sánchez Jimeno, Carolina; García Diez, Marta; Ayuso, C.; Lucas, R. de; Vicario, J.L.; Conti, C.J.; Zambruno, G.; Escámez Toledano, María José; Río Nechaevsky, Marcela del 2011-11-30T23:00:00Z http://hdl.handle.net/10016/16435 Title: MRI compatibility of position-sensitive photomultiplier depth-of-interaction PET detectors modules for in-line multimodality preclinical studies Author(s): Vaquero, Juan José; Sánchez, J. J.; Udías, José Manuel; Cal-González, Jacobo; Desco, Manuel Abstract: This work addresses the feasibility of a small-animal, in-line PET/MR system based on Position-Sensitive Photo Multiplier Tubes (PS-PMTs). To this end, we measured the effects of static magnetic fields on the PS-PMTs performance in order to explore the minimal tandem separation between the PET and MR subsystems to preserve their respective performances. We concluded that it is possible to achieve minimal degradation of the PET scanner performance (after a system recalibration) if the magnetic field strength influencing the PET detectors is less than 1 mT and if it is oriented perpendicularly to the longitudinal axis of the tube. Therefore, we predict that it will be possible to maintain the PET image quality if it is placed outside the 1 mT line. Description: [Poster] First Conference on PET-MR and SPECT-MR: New Paradigms for Combined Modalities in Molecular Imaging, May 26–30, 2012, The ELBA Island (Italy) 2013-02-20T23:00:00Z http://hdl.handle.net/10016/16433 Title: Improved dead-time correction for PET scanners: application to small-animal PET; Physics in Medicine and Biology Author(s): Vicente, Esther; Herraiz, J. L.; España, Samuel; Herranz, Elena; Desco, Manuel; Vaquero, Juan José; Udías, José Manuel Abstract: Pile-up and dead-time are two main causes of nonlinearity in the response of a PET scanner as a function of activity in the field of view (FOV). For a given scanner and acquisition system, pile-up effects depend on the material and size of the object being imaged and on the distribution of activity inside and outside the FOV, because these factors change the singles-to-coincidences ratio (SCR). Thus, it is difficult to devise an accurate correction that would be valid for any acquisition. In this work, we demonstrate a linear relationship between SCR and effective dead-time, which measures the effects of both dead-time (losses) and pile-up (gains and losses). This relationship allows us to propose a simple method to accurately estimate dead-time and pile-up corrections using only two calibration acquisitions with, respectively, a high and low SCR. The method has been tested with simulations and experimental data for two different scanner geometries: a scanner with large area detectors and no pile-up rejection, and a scanner composed of two full rings of smaller detectors. Our results show that the SCR correction method is accurate within 7%, even for high activities in the FOV, and avoids the bias of the standard single-parameter method. 2013-04-06T22:00:00Z http://hdl.handle.net/10016/15775 Title: Misalignments calibration in small-animal PET scanners based on rotating planar detectors and parallel-beam geometry Author(s): Abella, Mónica; Vicente, Esther; Rodríguez-Ruano, A.; España, Samuel; Lage, E.; Desco, Manuel; Udías, José Manuel; Vaquero, Juan José Abstract: Technological advances have improved the assembly process of PET detectors, resulting in quite small mechanical tolerances. However, in high-spatialresolution systems, even submillimetric misalignments of the detectors may lead to a notable degradation of image resolution and artifacts. Therefore, the exact characterization of misalignments is critical for optimum reconstruction quality in such systems. This subject has been widely studied for CT and SPECT scanners based on cone beam geometry, but this is not the case for PET tomographs based on rotating planar detectors. The purpose of this work is to analyze misalignment effects in these systems and to propose a robust and easy-to-implement protocol for geometric characterization. The result of the proposed calibration method, which requires no more than a simple calibration phantom, can then be used to generate a correct 3D-sinogram from the acquired list mode data. 2012-09-30T22:00:00Z