Doctorate in Applied and Engineering Physics  

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Thesis Proposal for the

Doctorate Program in Applied and Engineering Physics (DAEPHYS)

Starting in the Academic Year 2016/2017


Proposal 035


Title:Development of a Compton Camera for Nuclear Medical Imaging
 
Objectives (recommended length: 2000-3000 char):
The Anger Camera is the most spread detector in Nuclear Medical Imaging, namely for scintigraphy and Single Photon Emission Computed Tomography (SPECT). Although its success in the field, it stills presenting some imaging limitations: low position resolution (>8 mm) and fair energy resolutions (9-11%) for 140 keV. A lead collimator must be used in order to reproduce the projected image from the isotope distribution in the patient body. The consequence is a huge reduction (10-4) of the number of photons that impinges the crystal relatively to the number of photons emitted by the patient.
The Compton camera (a different concept) presents a different solution as it provides information about the incoming photon direction, avoiding the use of a collimator: it means that it is possible to reduce the patient dose or obtain better image quality for the same dose and improve the position resolution.
In contrast with the Anger Camera, where the detection efficiency is limited by the increase of the photon energy (~250 keV), the Compton Camera takes benefits from it, since the Compton cross-section increases with the energy of the photons. This fact triggers the possibility to use other radioisotopes (with photon energy exceeding 250 keV) for diagnosis that are nowadays inefficient with a Anger Camera. The low position and energy resolutions of Anger Camera are related to the low crystal light output and to the need of a collimator for image projection.
The aim of this work is to develop, build and study a Compton Camera envisaging Nuclear Medical Imaging (NMI). The main goal is to develop and test a 10x10 cm2 field-of-view (FOV) prototype, suitable for scintimammography and for small animal imaging, studying the possibility to scale it to a 30x30cm2 FOV prototype for human imaging.
The detector will be composed by a high pressure Gas Scintillation Proportional Counter/Time Projection Chamber coupled to a low cost and large area position sensitive gaseous photomultiplier (GPM).
Traditionally, Si and Ge semiconductor detectors have been investigated as Compton scatter detectors because of their good energy and position resolution. With such detectors it is, however, difficult to achieve a clinically useful field of view; they present needs of a massive number of electronic channels and very high costs, even for small scale devices. Our proposal presents a very competitive solution, which is feasibly with the good conditions of the different labs and with the high experience of the Team in these fields. The project deals with different technologies and techniques, being an excellent environment for students training.
 
Framework (recommended length: 500-2000 char):
Our group has a huge experience on working and developing CsI photosensors coupled to electron multiplier devices. Also we are experts in GSPC (Gas Scintillation Proportional Counters), one of the essential components of the proposed detector. The know-how on detectors development is also very high, namely for high energy particle physics experiments or detectors envisaging medical imaging.
The proposed detector is a combination of the existing knowledge with the ambition to develop a new device capable to compete in medical environment with the existing technology.
The group have excellent conditions for the proposed work, namely know-how and a full equipped laboratory for these developments. Recently, new equipment has been bought regarding this application.
 
Tasks (recommended length: 1000-3000 char):
Task 1 – Simulation:
The detector performance, namely full event detection (Compton+photoelectric) should be carefully studied by using Monte-Carlo simulation techniques. The first point is to simulate the primary electron cloud: by using Degrad software the number of primary electrons and their spatial distribution should be calculated for Xenon and mixtures, as a function of the pressure (0-20 bar).
Although the high number of primary electrons produced, their spatial distribution will depends on the gas type and pressure. Also, the excitation process should be taken into account as it will give information about the number of primary scintillation photons. This is also a crucial point as we will get information about the efficiency for a self-triggered detector configuration (avoiding external
trigger) and in such conditions we can operate it, i.e., which gas and pressure will benefit the number of primary scintillation photons.

Task 2. - Detector assembly and characterization:
By using an already partially existing hardware, a prototype of the compton camera should finished, clean, assembled and tested in therms of gas tightness, gas purity and electrical fields optimization.
The detector should be fully characterized and compared to the results obtained from previous task. A detailed measurements set of the position resolution and energy resolutions according to electric fields, gas pressure, etc, should be performed envisaging not only the applications but also the academic interest in the detectors performance knowledge.
After using calibration isotopes (e.g. Co-57), a set of phantoms should be designed and built in order to evaluate the detectors capability, using isotopes with clinical interest (ex: 140mTc). If possible,biological samples will be also used.

Task 3 – Software development
The goal is to build a software frame that contains all the detectors control parameters, i.e., power supply controls, gas flux controls, environment data-logging (pressure and temperature) and data acquisition. This will allow to create a single data file where all the parameters of the acquisitions will be recorded. The software should include the data analysis chain. A complete image reconstruction method should be included envisaging real-time image reconstruction.
Correction methods for the detector gain variations according to pressure and temperature will be developed.
 
Research centre/lab or R&D unit hosting the thesis project:
Radiation Detection and Medical Imaging (DRIM) group I3N – Aveiro and Physics Department of University of Aveiro;
 
University to which the thesis project will be presented:
UA - Universidade de Aveiro
 
DAEPHYS Scientific Domain in which the project fits:
Radiation, nuclear and atomic techniques
 
Relation of the project to the Scientific Domains of DAEPHYS:
The project deals with radiation and its interaction with matter, namely the photoelectric absorption and compton scattering.
In this work the atomic phenomena will be used, discussed and explored, as for example the electroeluminescence or atom de-excitation processes like fluorescence, Auger or Coster-Kronig processes.

 
Candidate profile:
The candidate should be self motivated with ambition to work in the radiation detection field.
He/she should present intermediate knowledge on Matlab or C++ programming languages .
The candidate should present strong motivation and skills to work in a experimental/instrumentation
project.
 
Does this proposal involve more than one University?:
yes
 
Synergies between the two Universities participating in the proposal:
DAEPHYS strongly encourages the presentation of thesis projects in co-supervision by researchers from two of the universities participating in the Program. In this field, explain the benefits resulting from the proposed co-supervision and the involvement of elements from the two universities, e.g. building critical mass teams, profiting from existing infrastructures or advanced equipments, profiting from expert technical know-how, etc. If the proposal involves only one University, write n/a.
(recommended length: 500-1000 char)
: DRIM and GIAN have a long and close collaboration tradition. The student will benefit with the knowledge of both groups. Moreover it is also usual to use/borrow the equipment and technical support own by each institution that will fill the lack of specific instrumentation.
 
Does this proposal involve a company?:
no
 
Proposals involving a company:
DAEPHYS strongly encourages the presentation of thesis projects involving a company, preferably a high-tech company. These proposals have to: 1) be centered on a technological problem in which the partner company has been (or plan / would like to be) involved; 2) have a co-supervisor on the enterprise; 3) include part of the project to be carried out in the company.
(recommended length: 500-1000 char)
:

 

Supervisor

Name:Carlos Davide da Rocha Azevedo
Institution: I3N - University of Aveiro
email:cdazevedo@ua.pt
 
link to CV or indication of ORCID ID:
http://orcid.org/0000-0002-7107-7203

 

Co-Supervisor

Name:Fernando Domingues Amaro
Institution:GIAN - Physics Department of University of Coimbra
email:famaro@gian.fis.uc.pt
 
link to CV or indication of ORCID ID:
http://orcid.org/0000-0001-7315-0550

 

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