In order to reduce the unnecessary radiation exposure for the clinical personnel, the optimization of procedures in the quality control test of gamma camera was investigated. A significant component of the radiation dose in performing the quality control testing is handling phantoms of radioactivity, especially the mixing to get a uniform activity concentration. Improving the phantom mixing techniques appeared to be a means of reducing radiation dose to personnel. However, this is difficult to perform without a continuous dynamic tomographic acquisition system to study mixing the phantom. In the first part of this study a computational fluid dynamics model was investigated to simulate the mixing procedure. Mixing techniques of shaking and spinning were simulated using the computational fluid dynamics tool FLUENT. In the second part of this study a Siemens E.Cam gamma camera was simulated using the Monte Carlo software SIMIND. A series of validation experiments demonstrated the reliability of the Monte Carlo simulation. In the third part of this study the simulated the mixing data from FLUENT was used as the source distribution in SIMIND to simulate a tomographic acquisition of the phantom. The planar data from the simulation was reconstructed using filtered back projection to produce a tomographic data set for the activity distribution in the phantom. This completed the simulation routine for phantom mixing and verified the Proof-in-Concept that the phantom mixing problem can be studied using a combination of computational fluid dynamics and nuclear medicine radiation transport simulations.

The optimisation of image quality in medical imaging techniques is a significant factor in favourable patient prognoses. The number of counts in a nuclear medicine image is one factor in determining the diagnostic value of the image. The current study aims to determine the variation in counts in whole-body bone scan images with patient height and weight. Three separate studies were undertaken as part of the investigation. First, 65 whole-body bone scans were analysed together with patient height, weight, age and sex. Weight was found to the most important anatomy influence on image counts. However, significant influences from patient sex and age meant that a useful relationship between image counts and patient anatomy based solely on height and weight could not be determined. For the second study, a model of General Electric Millennium MG gamma camera was created and validated within the SIMIND Monte Carlo software. The results indicate that the model is an accurate representation of the gamma camera. Third, the 4D NCAT whole-body patient phantom was modified to represent the average male and female clinical study participants. The phantoms were used in conjunction with the gamma camera model to simulate the whole-body bone scan procedure. The counts in the simulated images were consistent with the average measured counts of the clinical study indicating that it is feasible to use the NCAT phantom for nuclear medicine bone imaging. However, the phantom’s method of activity distribution should be refined to allow a more realistic distribution of activity throughout the skeleton.

Tématem této diplomové práce je design kardiologické gama kamery. Hlavním cílem práce je navrhnout originální, vizuálně i ergonomicky vyvážený design pro sedícího či napůl ležícího pacienta s využitím nejnovějších technologií s důrazem na propojení dílčích segmentů v kompaktní celek.

Le présent travail a pour but le développement d’une caméra gamma à masque codé permettant d’estimer la position tridimensionnelle (3D) des sources radioactives. Cela est d’un intérêt considérable dans le cadre d’un grand nombre d'applications, de la reconstruction de la forme 3D des objets radioactifs aux systèmes de réalité augmentée appliqués à la radioprotection. Les caméras gamma portables actuelles ne fournissent que la position angulaire relative des sources gamma à localiser, c'est-à-dire qu'aucune information métrique concernant les sources n’est disponible, comme par exemple leur distance par rapport à la caméra. Dans cette thèse, nous proposons principalement deux approches permettant d’estimer la position 3D des sources. La première approche consiste à étalonner la caméra gamma avec un capteur de profondeur à lumière structurée. La seconde approche permet d'estimer la distance source-détecteur par une méthode d’imagerie gamma stéréoscopique. Pour aligner géométriquement les images obtenues par la caméra gamma, le capteur de profondeur, et la caméra optique, une procédure d'étalonnage n’utilisant qu’une seule source ponctuelle radioactive a été conçue et mise en œuvre. Les résultats expérimentaux démontrent que les approches proposées permettent d'obtenir une précision inférieure au pixel, tant pour l’erreur de reprojection que pour la superposition des images gamma et optiques. Ces travaux présentent également une analyse quantitative de la précision et de la résolution relatives à l’estimation de la distance source-détecteur. De plus, les résultats obtenus ont validé le choix de la géométrie du modèle sténopé pour les caméras gamma à masque codé. / A coded aperture gamma camera for retrieving the three-dimensional (3-D) position of radioactive sources is presented. This is of considerable interest for a wide number of applications, ranging from the reconstruction of the 3-D shape of radioactive objects to augmented reality systems. Current portable γ-cameras only provide the relative angular position of the hotspots within their field of view. That is, they do not provide any metric information concerning the located sources. In this study, we propose two approaches to estimate the distance of the surrounding hotspots, and to autonomously determine if they are occluded by an object. The first consists in combining and accurately calibrating the gamma camera with a structured-light depth sensor. The second approach allows the estimation of the source-detector distance by means of stereo gamma imaging. To geometrically align the images obtained by the gamma, depth, and optical cameras used, a versatile calibration procedure has been designed and carried out. Such procedure uses a calibration phantom intentionally easy to build and inexpensive, allowing the procedure to be performed with only one radioactive point source. Experimental results showed that our calibration procedure yields to sub-pixel accuracy both in the re-projection error and the overlay of radiation and optical images. A quantitative analysis concerning the accuracy and resolution of the retrieved source-detector distance is also provided, along with an insight into the respective most influential factors. Moreover, the results obtained validated the choice of the geometry of the pinhole model for a coded aperture gamma camera.

In modern clinical practice, gamma camera is one of the most important imaging modalities for tumour diagnosis. The standard technique uses scintillator-based gamma cameras equipped with parallel-hole collimator to detect the planar position of γ photon interaction (scintillation). However, the positioning is of insufficient resolution and linearity for breast imaging. With the aim to improve spatial resolution and positioning linearity, a new gamma camera configuration was described specifically for breast-imaging. This breast-specific gamma camera was supposed to have the following technical features: variable angle slant-hole collimator; double SiPM arrays readout at the front and back sides of the scintillator; diffusive reflectors at the edges around the scintillator. Because slant-hole collimator was used, a new 3D scintillation positioning method was introduced and tested. The setup of the gamma detector was created in a Monte Carlo simulation toolkit, and a library of a number of light distributions from known positions was acquired through optical simulation. Two library-based positioning algorithms, similarity comparison and maximum likelihood, were developed to estimate the 3D scintillation position by comparing the responses from simulated gamma interactions and the responses from library. Results indicated that the planar spatial resolution and positioning linearity estimated with this gamma detector setup and positioning algorithm was higher than the conventional gamma detectors. The depth-of-interaction estimation was also of high linearity and resolution. With the results presented, the gamma detector setup and positioning method is promising in future breast cancer diagnosis.

Large-scale radiological accidents have resulted in intakes of radioactive materials by members of the public and occupational radiation workers. However, current methods to evaluate intakes are designed for small numbers of individuals and cannot be easily scaled for large populations as has occurred. A proposed method for high throughput volumes of people to identify and quantify intakes of radioactive material through urine radiobioassay is described. MATERIALS AND METHODS: The MCNP V6.0 software code was used to model the General Electric Hawkeye V3 Gamma Camera for gamma ray efficiency. Technitium-99m was used to validate the model. The model was used to calculate detection efficiencies and minimum detectable doses for Cobalt-60, Iodine-131, Cesium-137/Barium-137m and Iridium-192. RESULTS: Differences of 8% were observed between measurements of the detection efficiency for Technitium-99m and the MCNP modeled detection efficiency (11.1% vs. 12.0%, respectively). Calculations showed that a dose of 20 mSv could be detected using urine radiobioassay in 6, 3, 2, and 20 days post incident for Type F intakes of Cobalt-60, Iodine-131, Cesium-137/Barium-137m and Iridium-192 respectively. Approximately 1,152 urine samples could be analyzed in an eight-hour shift using a single gamma camera. CONCLUSIONS: The use of the gamma camera for urine radiobioassay allows for high throughput volumes of samples and has sufficient detection sensitivity to meet dose-based decision guidelines.

Depuis son émergence, la médecine nucléaire ne cesse d’évoluer. A la fois diagnostique et thérapeutique, elle occupe une place importante dans la stratégie médicale moderne. L’imagerie nucléaire consiste après injection au patient d’un radiotraceur, à détecter le rayonnement émis. Elle donne accès quantitativement à la fonctionnalité des organes ou à la localisation de structures cibles telles que des lésions tumorales. Cette imagerie a naturellement intégré les procédures chirurgicales en particulier en cancérologie (en pré et per opératoire). On parle de chirurgie radioguidée. Cette dernière permet de localiser lors du geste chirurgical les structures radiomarquées devant être retirées.Les avancées technologiques au niveau des radiopharmaceutiques et en instrumentation sont à l’origine de nouvelles stratégies de radioguidages pouvant cibler de petites structures. L’imagerie par rayonnement gamma reste la plus répandue et la mieux adaptée. On assiste au développement de dispositifs d’imagerie gamma portables miniaturisés permettant un contrôle visuel en per opératoire. Ces dispositifs sont prometteurs mais doivent être évalués.Un état des lieux des différentes procédures en chirurgie radioguidée et des imageurs utilisés en clinique est réalisé dans cette thèse.Le laboratoire Imagerie et Modélisation en Neurobiologie et Cancérologie (UMR 8165) développe de longue date de nouvelles approches de détection miniaturisée pour les différents types de rayonnement. Parmi celles-ci le prototype de deuxième génération appelé TReCam.Cette mini gamma caméra présente un champ de vue de 4,9 x 4,9 cm2 et intègre des technologies d’imagerie directement issues de la physique des particules. Elle est formée d’un collimateur à trous parallèles, d’un scintillateur continu LaBr3 (Ce) lu par un photomultiplicateur multi-anode et son électronique. Le système d’acquisition donne au chirurgien un affichage en temps réel de l’image radioactive.Ce travail de thèse a consisté également à évaluer la place des imageurs portables en chirurgie radioguidée, en particulier mammaire, à travers l’évaluation de la procédure SNOLL (repérage par marquage ɣ de la tumeur (T) et des ganglions sentinelles (GS)) avec TreCam. Il a reposé sur trois parties.Un premier volet a visé l’optimisation des performances de TReCam pour favoriser la localisation de structures peu radioactives dans des temps d’exposition de l’ordre de la dizaine de secondes. Pour ce faire, différentes stratégies d’optimisation des performances ont été mises en place au niveau du collimateur, de l’électronique et des algorithmes de traitement (dont réseaux de neurones) pour améliorer l’homogénéité de la détection.Le deuxième volet visait à objectiver les performances cliniques de TReCam pour la procédure SNOLL et situer les limites de son exploitation. A l’aide de simulations menées sur la plateforme GATE et modélisant la scène opératoire au plus près de la réalité clinique, nous avons montré que TreCam peut détecter des GS jusqu’à 4,5 cm de profondeur et situé à 4 cm de la T. L’impact du temps de pose n’est pas important. Par contre, le choix de la bonne fenêtre en énergie est primordial.Enfin, le troisième volet concrétise l’ambition interdisciplinaire de cette thèse. Il est consacré à l’évaluation clinique de TReCam à travers l’étude de son apport à la procédure SNOLL mammaire. Cette étude prospective interventionnelle incluant de 47 patientes (22 procédures SNOLL utilisant TReCam aux différents temps de la procédure et 25 procédures SNOLL standard). Les résultats ont montré un intérêt qualitatif à l’utilisation de TReCam en apportant un confort visuel lors de la procédure en complément de la sonde monopixel.Ce travail a montré l’intérêt de tels imageurs en chirurgie radioguidée mais aussi situé leurs limites actuelles. Des efforts de développement doivent être poursuivis tant au niveau des détecteurs qu’au niveau des radiopharmaceutiques utilisés pour le repérage. / Since its emergence in the middle of the twentieth century, nuclear medicine continues to evolve. At the same time diagnostic and therapeutic, it occupies an increasingly important place in the modern medical strategy. Nuclear imaging consists of injecting the patient with a radio-tracer to detect the radiation emitted. It provides quantitative access to the functionality of organs or the location of target structures such as tumor lesions. This imaging has been naturally integrated into surgical procedures, particularly in oncology (preoperatively and then intraoperatively). It is called radio-guided surgery. It makes possible to locate the radioactive target which will be removed during surgery.Technological advances in radiopharmaceutical instrumentation are driving new strategies that can target small structures. Gamma-ray imaging remains the most widespread and the most suitable. We are witnessing the development of miniaturized portable gamma imaging devices that allow visual control during surgery. These devices are promising but need to be evaluated.A short state-of-the-art of the various procedures in radioguided surgery and imagers used clinically is carried out in this thesis.For many years, the Imaging and Modeling in Neurobiology and Oncology Laboratory (UMR 8165) has been developing new miniaturized detection approaches for different types of radiation. Among them is the second-generation prototype called TReCam.This mini gamma camera has a field of view of 4.9 x 4.9 cm2 and integrates imaging technologies directly from particle physics. It consists of a collimator with parallel holes, a continuous scintillator LaBr3 (Ce) read by a multi-anode photomultiplier (PSPMT) and its electronics. The acquisition system gives the surgeon a real-time display of the radioactive image.This thesis work also consisted in evaluating the place of portable imagers in radioguided surgery, in particular mammary surgery, through the evaluation of the SNOLL procedure (identification of the tumor (T) and the sentinel lymph nodes (GS) by γ-labeling) with TreCam. It is based on three parts.The first part aimed at optimizing the performance of TReCam to improve the localization of lowradioactive structures with exposure times of around 10 seconds. To do this, different performance optimization strategies have been implemented in the collimator, electronics and processing algorithms (including neural networks) to improve the homogeneity of the detection. These performances were compared to those of a prototype developed at IMNC and integrating a new generation of photodetectors: the SiPM.The second part aimed to objectify the clinical performance of TReCam in the SNOLL procedure and to situate the limits of its exploitation. Using simulations conducted on the GATE platform and modeling the operating scene closer to clinical reality, we have shown that TreCam can detect GS up to 4.5 cm deep and located 4 cm from the T. Impact of the exposure time is not important. On the other hand, choosing the right energy window is essential.Finally, the third part concretizes the interdisciplinary ambition of this thesis. It is devoted to clinical evaluation of TReCam through the study of its contribution to the SNOLL breast procedure. This prospective interventional study included 47 patients (22 SNOLL procedures using TReCam at different times of the procedure and 25 standard SNOLL procedures). The results showed a qualitative interest in the use of TReCam by bringing a visual comfort during the procedure and must be used in addition to the monopixel probes.This work has shown the interest of such imagers in radioguided surgery but also set their current limits. Development efforts must be pursued at the level of both detectors and radiopharmaceuticals used for tracking.

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Medical imaging based on radioactive tracers exposes the patient to radiation. For this reason, a phantom is preferably used for non-clinical studies such as routine quality assurance and research. The aim of this project was to design, build and test a multi-compartment phantom to be used in dynamic SPECT/CT, PET/CT and PET/MRI studies. By treating each compartment as a biological system and plotting activity distribution, desired characteristics of the phantom can be obtained. A software program was created to simulate compartment activity distribution for different input parameters. Such parameters include number of compartments, administered activity, flow rates between compartments and compartment volume. Based on the simulation, the phantom was designed to meet the desired characteristics. Due to the outbreak of the SARS-CoV-2 virus, no phantom could be built nor tested. Consequently, leading the project to create a foundation that facilitates future building of the phantom. / Medicinsk avbildning med radioaktiva spårämnen utsätter patienter för en stråldos. Av detta skäl används företrädesvis en fantom för icke-kliniska studier såsom rutinmässig kvalitetssäkring och forskning. Syftet med detta projekt var att designa, bygga och testa ett flerkammarfantom som ska användas i dynamiska SPECT/CT, PET/CT och PET/MRI studier. Genom att behandla varje kammare som ett biologiskt system och plotta aktivitetsfördelning kan önskade egenskaper hos fantomen erhållas. Ett program skapades för att simulera aktivitetsdistributionen i flerkammarfantomer för olika in parametrar så som antal kammare, administrerad aktivitet, flöden mellan kammare och kammarvolym. Baserat på simuleringen utformades fantomen för att uppfylla de önskade egenskaperna. På grund av utbrottet av SARS-CoV-2 viruset kunde ingen fantom byggas eller testas. Följaktligen leddes projektet till att skapa en grund som underlättar framtida byggande av fantomen.