R. Ribeiro

Bio: R. Ribeiro is an academic researcher from CERN. The author has contributed to research in topics: Detector & Cherenkov radiation. The author has an hindex of 10, co-authored 30 publications receiving 304 citations. Previous affiliations of R. Ribeiro include Faculdade de Engenharia da Universidade do Porto & University of Coimbra.

The application of genetic algorithms for shape control with piezoelectric patches—an experimental comparison

Abstract: The problem of shape control and correction of small displacements in composite structures using piezoelectric actuators glued or embedded was addressed. A finite element model based on Mindlin plate theory was used to characterize the behaviour of the structure and the one of the actuators. Emphasis was put on the development of an efficient and general methodology, based on genetic algorithms, for the determination of the optimal actuation voltages needed to apply to the piezoelectric actuators in such a way that a pre-defined shape of the structure is achieved. The model was investigated numerically and verified experimentally. Measurements were carried out using electronic speckle pattern interferometry. Good agreement was found between simulation results and the optically measured values.

Clear-PEM: A PET imaging system dedicated to breast cancer diagnostics

Abstract: The Clear-PEM scanner for positron emission mammography under development is described. The detector is based on pixelized LYSO crystals optically coupled to avalanche photodiodes and readout by a fast low-noise electronic system. A dedicated digital trigger (TGR) and data acquisition (DAQ) system is used for on-line selection of coincidence events with high efficiency, large bandwidth and small dead-time. A specialized gantry allows to perform exams of the breast and of the axilla. In this paper we present results of the measurement of detector modules that integrate the system under construction as well as the imaging performance estimated from Monte Carlo simulated data.

Clear-PEM: A dedicated pet camera for improved breast cancer detection

Abstract: Positron emission mammography (PEM) can offer a non-invasive method for the diagnosis of breast cancer. Metabolic images from PEM using 1 8 F-fluoro-deoxy-glucose, contain unique information not available from conventional morphologic imaging techniques like X-ray radiography. In this work, the concept of Clear-PEM, the system presently developed in the frame of the Crystal Clear Collaboration at CERN, is described. Clear-PEM will be a dedicated scanner, offering better perspectives in terms of position resolution and detection sensitivity.

Fast RICH detector with a cesium iodide photocathode at atmospheric pressure

Abstract: CsI photocathodes of 30 × 30 cm 2 size have been operated in a fast RICH detector composed of a NaF radiator and a multiwire proportional chamber with a cathode pad readout. Results are presented from tests with a 3 GeV c proton beam. A Cherenkov angular resolution of 8 mrad is obtained by detecting a mean of 8 photoelectrons per ring. Methods are described for counting the Cherenkov photons and evaluating the differential quantum efficiency of the CsI photocathode. The results obtained with photons impinging at a large angle on the CsI layer are presented and discussed in comparison with higher quantum efficiencies observed under different experimental conditions.

Design and evaluation of the clear-PEM detector for positron emission mammography

Abstract: The design and evaluation of the imaging system Clear-PEM for positron emission mammography, under development by the PEM Consortium within the framework of the Crystal Clear Collaboration at CERN, is presented. The proposed apparatus is based on fast, segmented, high atomic number radiation sensors with depth-of-interaction measurement capabilities and state-of-the-art data acquisition techniques. The camera consists of two compact and planar detector heads with adequate field-of-view dimensions for breast and axilla imaging. Low-noise integrated electronics provide signal amplification and analog multiplexing based on a new data-driven architecture. The coincidence trigger and data acquisition architecture makes extensive use of pipeline processing structures and multi-event memories for high efficiency up to a data acquisition rate of one million events/s. Experimental validation of the detection techniques, namely the basic properties of the radiation sensors and the ability to measure the depth-of-interaction of the incoming photons, are presented. System performance in terms of detection sensitivity, count-rates and reconstructed image spatial resolution were also evaluated by means of a detailed Monte Carlo simulation and an iterative image reconstruction algorithm.

Multimodality imaging of structure and function.

Abstract: Historically, medical devices to image either anatomical structure or functional processes have developed along somewhat independent paths. The recognition that combining images from different modalities can nevertheless offer significant diagnostic advantages gave rise to sophisticated software techniques to coregister structure and function. Recently, alternatives to retrospective software-based fusion have become available through instrumentation that combines two imaging modalities within a single device, an approach that has since been termed hardware fusion. As a result, following their recent introduction into the clinic, combined PET/CT and SPECT/CT devices are now playing an increasingly important role in the diagnosis and staging of human disease. Recently, although limited to the brain, the first clinical MR scanner with a PET insert, a technically-challenging design, has been undergoing evaluation. This review will follow the development of multimodality instrumentation for clinical use from conception to present-day technology and assess the status and future potential for such devices.

Letter of Intent

Abstract: Der Zugang zu und die Nutzung von vorhandenen Geoinformationen soll aufgrund des innerhalb und außerhalb Deutschlands stetig wachsenden Bedarfs zukunftsorientiert ausgerichtet werden. Insbesondere bei den Themen demographische Entwicklung, Klimawandel, Umweltschutz, Energiewende und übergreifende Fragestellungen soll durch den Ausbau und Betrieb einer Geodateninfrastruktur die Effizienz und Effektivität von Entscheidungsprozessen gesteigert werden. Geodateninfrastrukturen sollen neue Wertschöpfungspotentiale für die Wirtschaft erschließen und eine bessere Information der Gesellschaft ermöglichen. Die Entwicklungen von nationalen und europäischen Geodateninfrastrukturen sind zugleich wesentlicher Bestandteil der EGovernment-Initiativen von Bund, Ländern und Kommunen.

CsI UV photocathodes: history and mystery

Abstract: CsI films are known to be efficient photoconvertors, intensively investigated for UV-photon imaging devices. The article reviews the production and characterization techniques of CsI photocathodes and their photoemission properties in vacuum and gas media, in charge collection and multiplication modes. The important roles of surface phenomena, gas and electric fields are described. The stability of the films is discussed.

The positron emission mammography/tomography breast imaging and biopsy system (PEM/PET): design, construction and phantom-based measurements.

Abstract: Tomographic breast imaging techniques can potentially improve detection and diagnosis of cancer in women with radiodense and/or fibrocystic breasts. We have developed a high-resolution positron emission mammography/tomography imaging and biopsy device (called PEM/PET) to detect and guide the biopsy of suspicious breast lesions. PET images are acquired to detect suspicious focal uptake of the radiotracer and guide biopsy of the area. Limited-angle PEM images could then be used to verify the biopsy needle position prior to tissue sampling. The PEM/PET scanner consists of two sets of rotating planar detector heads. Each detector consists of a 4 x 3 array of Hamamatsu H8500 flat panel position sensitive photomultipliers (PSPMTs) coupled to a 96 x 72 array of 2 x 2 x 15 mm(3) LYSO detector elements (pitch = 2.1 mm). Image reconstruction is performed with a three-dimensional, ordered set expectation maximization (OSEM) algorithm parallelized to run on a multi-processor computer system. The reconstructed field of view (FOV) is 15 x 15 x 15 cm(3). Initial phantom-based testing of the device is focusing upon its PET imaging capabilities. Specifically, spatial resolution and detection sensitivity were assessed. The results from these measurements yielded a spatial resolution at the center of the FOV of 2.01 +/- 0.09 mm (radial), 2.04 +/- 0.08 mm (tangential) and 1.84 +/- 0.07 mm (axial). At a radius of 7 cm from the center of the scanner, the results were 2.11 +/- 0.08 mm (radial), 2.16 +/- 0.07 mm (tangential) and 1.87 +/- 0.08 mm (axial). Maximum system detection sensitivity of the scanner is 488.9 kcps microCi(-1) ml(-1) (6.88%). These promising findings indicate that PEM/PET may be an effective system for the detection and diagnosis of breast cancer.