Hole-type gaseous detectors for medical imaging and HEP experiments

This work presents the results on the development of a high pressure Xe gaseous detector envisaging medical imaging. The detector uses two VUV photosensors operating face-to-face, based on the CsI-MHSP with position discrimination capability. The known effect of the charge gain decrease with the gas pressure is compensated with a light gain using the electroluminescence process. Studies of signal amplitude, energy and position resolution are presented. On the second part, gaseous detectors based on THGEM where studied in order to fulfill the requirements of present and future high energy physics experiments. The work is focused on the application of THGEM in RICH detectors elements: a triple THGEM detector using CsI photocathodes in Ne mixtures was suggested. The ion backflow to the photocathode remains a concern and a limitation; to minimize it, the application of a new hole-structure, THCOBRA, was suggested. Preliminary results foresee good perspectives for the successful application of THCOBRA in ion back-flow suppression. This work contains several methods and measurements of the CsI photocathodes behaviour in radiation gaseous detectors. A long discussion on its issues and possible solutions are presented.

Federated architecture for biomedical data integration

The last decades have been characterized by a continuous adoption of IT solutions in the healthcare sector, which resulted in the proliferation of tremendous amounts of data over heterogeneous systems. Distinct data types are currently generated, manipulated, and stored, in the several institutions where patients are treated. The data sharing and an integrated access to this information will allow extracting relevant knowledge that can lead to better diagnostics and treatments. This thesis proposes new integration models for gathering information and extracting knowledge from multiple and heterogeneous biomedical sources. The scenario complexity led us to split the integration problem according to the data type and to the usage specificity. The first contribution is a cloud-based architecture for exchanging medical imaging services. It offers a simplified registration mechanism for providers and services, promotes remote data access, and facilitates the integration of distributed data sources. Moreover, it is compliant with international standards, ensuring the platform interoperability with current medical imaging devices. The second proposal is a sensor-based architecture for integration of electronic health records. It follows a federated integration model and aims to provide a scalable solution to search and retrieve data from multiple information systems. The last contribution is an open architecture for gathering patient-level data from disperse and heterogeneous databases. All the proposed solutions were deployed and validated in real world use cases.

Study and development of UV photodetectors envisaging COMPASS RICH-1 upgrade and applications

COMPASS is an experiment at CERN’s SPS whose goal is to study hadron structure and spectroscopy. The experiment includes a wide acceptance RICH detector, operating since 2001 and subject to a major upgrade of the central region of its photodetectors in 2006. The remaining 75% of the photodetection area are still using MWPCs from the original design, who suffer from limitations in gain due to aging of the photocathodes from ion bombardment and due to ion-induced instabilities. Besides the mentioned limitations, the increased luminosity conditions expected for the upcoming years of the experiment make an upgrade to the remaining detectors pertinent. This upgrade should be accomplished in 2016, using hybrid detectors composed of ThGEMs and MICROMEGAS. This work presents the study, development and characterization of gaseous photon detectors envisaging the foreseen upgrade, and the progress in production and evaluation techniques necessary to reach increasingly larger area detectors with the performances required. It includes reports on the studies performed under particle beam environment of such detectors. MPGD structures can also be used in a variety of other applications, of which nuclear medical imaging is a notorious example. This work includes, additionally, the initial steps in simulating, assembling and characterizing a prototype of a gaseous detector for application as a Compton Camera.