Signal formation in a photon-counting x-ray/gamma-ray imaging detector is a complex process resulting in detector signals governed by multiple random effects. Recovering maximum possible information about event attributes of interest requires a systematic collection of calibration data and analysis provided by estimation theory. In this context, a likelihood model provides a description of the connection between the observed signals and the event attributes. A quantitative measure of how well the measured signals can be used to produce an estimate of the parameters is given by Fisher Information analysis. In this work, we demonstrate several applications of the Fisher Information Matrix (FIM) as a powerful and practical tool for investigating and optimizing potential next-generation x-ray/gamma-ray detector designs, with an emphasis on medical-imaging applications. Using FIM as a design tool means to explore the physical detector design choices that have a relationship with the FIM through the likelihood function, how are they interrelated, and determining whether it is possible to modify any of these choices to yield or retain higher values for Fisher Information. We begin by testing these ideas by investigating a new type of a semiconductor detector, a Cadmium Telluride (CdTe) detector with double-sided-strip geometry developed by our collaborators at the Japan Aerospace Exploration Agency (JAXA). The statistical properties of the detector signals as a function of interaction positions in 3D (x, y, z) are presented with mathematical expressions as well as experimental data from measurements using synchrotron radiation at the Advanced Photon Source at Argonne National Laboratory. We show the computation of FIM for evaluating positioning performance and discuss how various detector parameters, that are identified to affect FIM, can be used in detector optimization. Next, we show the application of FIM analysis in a detector system based on multi-anode photomultiplier tubes coupled to a monolithic scintillator in the design of smart electronic read-out strategies. We conclude by arguing that a detector system is expected to perform the best when the hardware is optimized jointly with the estimation algorithm (simply referred to as the "software" in this context) that will be used with it. The results of this work lead to the idea of a detector development approach where the detector hardware platform is developed concurrently with the software and firmware in order to achieve optimal performance.

A tomografia computadorizada por emissão de fóton único (SPECT) é uma das modalidades de diagnóstico na Medicina Nuclear em que se detecta a radiação emitida por um radiofármaco previamente administrado ao paciente. Visto que osfótons emitidos sofrem interações com o corpo do paciente, fazem-se necessárias as correções de atenuação e de espalhamento a fim de melhor representar a distribuição do radiofármaco, e assimresultar em imagens mais precisas. O objetivo deste trabalho é avaliar os parâmetros anotados como padrão para reconstruções de imagens tomográficas e as correções de atenuação e de espalhamento em imagens SPECT do Hospital de Clínicas da Faculdade de Medicina da Universidade de São Paulo, por meio de análises qualitativas e quantitativas das imagens reconstruída a partir das aquisições tomográficas. Sob um protocolo de SPECT-CT cerebral modificado para duas janelas de aquisição, foram adquiridas imagens SPECT e SPECT-CT (BrightView XCT, Philips) utilizando fantomaJaszczak e reconstruídas pelos métodos FBP, MLEM e OSEM. Os resultados mostram que o método FBP apresenta imagens de baixa precisão devido à baixa SNR. A avaliação sugere o uso dos métodos iterativos MLEM e OSEM com correção de atenuação como método padrão de reconstrução de imagens de perfusão cerebral. De acordo com a avaliação de imagens do fantomaJaszczak e análise do contraste entre esfera fria ebackground,propõe-se análise observacional e avaliação das imagens clínicas reconstruídas pelo método OSEM com os parâmetros 3 iterações, 16 subsets, filtro Butterworth com frequência de corte 0,34 e potencia 1, como novos parâmetros padrão de reconstrução de imagens. / Single Photon Emission Computed Tomography (SPECT) is one of the diagnostic modalities in nuclear medicine, it detects the radiation emitted by a radioisotope previously administered to the patient. Since the photons undergo interactions with the patient\'s body,attenuationand scatteringcorrections are necessary in order to best represent the distribution of the radiopharmaceutical, and thus result in more accurate images. The aim of this study is to evaluate the standard parameters for tomographic imagesreconstruction, and attenuation and scatter corrections ofSPECT images, from Hospital das Clínicas da Faculdade de Medicina de RibeirãoPreto, Universidade de São Paulo, through qualitativeand quantitative analysis of the reconstructed image obtained from SPECT aquisitions. Though a modified to two windows of acquisition protocol for cerebral SPECT-CT, we acquired SPECT and SPECT-CT images (BrightView XCT, Philips) using phantom Jaszczak and the ones were reconstructed by FBP, MLEM and OSEM methods. The results show that the FBP method has poor image precision due to low SNR. The review suggests the use of iterative methods MLEM and OSEM with attenuation correction as a standard method of image reconstruction of cerebral perfusion. According to the images the phantom Jaszczak and contrast analysis between cold sphere and background, we propose observational analysis and evaluations of clinical images reconstructed by OSEM method with parameters 3 iterations, 16 subsets, Butterworth filter with cutoff frequency 0.34 and order 1, as newstandard parameters for image reconstruction parameters.

Ziel der Studie war ein Zusammenhang zwischen cholinerger Innervation in den Basalganglien mit Levodopa-induzierter Dyskinesie darzustellen. 26 Patienten mit idiopatischem Parkinson-Syndrom ohne Demenz und Depression wurden in zwei Gruppen mit und ohne Dyskinesie eingeteilt. Es wurde nach klinischer Untersuchung eine SPECT-Bildgebung mit 5-[123I]iodo-3-[2(S)-2-azetidinylmethoxy]pyridine (5IA) durchgeführt und anschließend die Ergebnisse in Zusammenschau mit den klinischen Daten und mit den Ergebnissen der SPECT mit [123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (FP-CIT) bewertet. Dyskinetische Patienten hatten eine höhere Dichte an nikotinergen Acetylcholinrezeptoren im Nucleus caudatus, hauptsächlich der Halbseite mit stärkerer dopaminerger Degeneration. Dies stützt die Hypothese, dass sich die Dyskinesie nach Levodopa-Therapie aufgrund einer verstärkten cholinergen Modulation im stärker degenerierten Striatum entwickelt. / Objective: To explore cholinergic innervation in the basal ganglia in relation to levodopa-induced dyskinesia in patients with Parkinson’s disease. Methods: A total of 26 patients with PD without dementia and depression were divided into two matched groups (dyskinetic and nondyskinetic). We acquired SPECT scan with 5-[123I]iodo-3-[2(S)-2-azetidinylmethoxy]pyridine. We then analyzed binding potentials at basal ganglia structures and correlations with clinical variables and [123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane SPECT. Results: Dyskinetic subjects showed higher density of nicotinic acetylcholine receptors in the caudate nucleus, predominant in the hemisphere with lower dopamine transporter density. Conclusion: Our findings support the hypothesis that the expression of dyskinesia following repeated levodopa exposure may result from enhanced cholinergic neuronal excitability in a dopaminergic-depleted striatum.

<p>This work investigates phantom and subject positioning as well as collecting data with a variety of angular sampling and acquisition trajectories. The overall goal of this work has been to utilize the dedicated, breast SPECT-CT system to acquire the best possible images. A large portion of this work has been to apply corrections to the system for quantitative imaging. The system has been shown to provide high quality images with minimal out-of-field signal contribution. Additionally, the quantification procedure has been shown to be within 10% of the known activity concentration present at the time of imaging for both VAOR and PROJSINE trajectories.</p> / Dissertation

<p>Nukleärmedicinska bilder som exempelvis SPECT (Single Photon Emission Tomogra-phy) är en bildgenererande teknik som ofta används i många applikationer vid mätning av fysiologiska egenskaper i den mänskliga kroppen. En vanlig sorts undersökning som använder sig av SPECT är myokardiell perfusion (blodflöde i hjärtvävnaden), som ofta används för att undersöka t.ex. en möjlig hjärtinfarkt. För att göra det möjligt för läkare att ställa en kvalitativ diagnos baserad på dessa bilder, måste bilderna först segmenteras och roteras av en biomedicinsk analytiker. Detta utförs på grund av att hjärtat hos olika patienter, eller hos patienter vid olika examinationstillfällen, inte är lokaliserat och roterat på samma sätt, vilket är ett väsentligt antagande av läkaren vid granskning</p><p>av bilderna. Eftersom olika biomedicinska analytiker med olika mängd erfarenhet och expertis roterar bilderna olika uppkommer variation av de slutgiltiga bilder, vilket ofta kan vara ett problem vid diagnostisering.</p><p>En annan sorts nukleärmedicinsk undersökning är vid kvantifiering av dopaminreceptorer i de basala ganglierna i hjärnan. Detta utförs ofta på patienter som visar symptom av Parkinsons sjukdom, eller liknande sjukdomar. För att kunna bestämma graden av sjukdomen används ofta ett utförande för att räkna ut olika kvoter mellan områden runt dopaminreceptorerna. Detta är ett tröttsamt arbete för personen som utför kvantifieringen och trots att de insamlade bilderna är tredimensionella, utförs kvantifieringen allt för ofta endast på en eller flera skivor av bildvolymen. I likhet med myokardiell perfusionsundersökningar är variation mellan kvantifiering utförd av olika personer en möjlig felkälla.</p><p>I den här rapporten presenteras en ny metod för att automatiskt segmentera hjärtats vänstra kammare i SPECT-bilder. Segmenteringen är baserad på en intensitetsinvariant lokal-fasbaserad lösning, vilket eliminerar svårigheterna med den i myokardiella perfusionsbilder ofta varierande intensiteten. Dessutom används metoden för att uppskatta vinkeln hos hjärtats vänstra kammare. Efter att metoden sedan smått justerats används den som ett förslag på ett nytt sätt att automatiskt kvantifiera dopaminreceptorer i de basala ganglierna, vid användning av den radioaktiva lösningen DaTSCAN.</p> / <p>Nuclear medical imaging such as SPECT (Single Photon Emission Tomography) is an imaging modality which is readily used in many applications for measuring physiological properties of the human body. One very common type of examination using SPECT is when measuring myocardial perfusion (blood flow in the heart tissue), which is often used to examine e.g. a possible myocardial infarction (heart attack). In order for doctors to give a qualitative diagnose based on these images, the images must first be segmented and rotated by a medical technologist. This is performed due to the fact that the heart of different patients, or for patients at different times of examination, is not situated and rotated equally, which is an essential assumption for the doctor when examining the images. Consequently, as different technologists with different amount of experience and expertise will rotate images differently, variability between operators arises and can often become a problem in the process of diagnosing.</p><p>Another type of nuclear medical examination is when quantifying dopamine transporters in the basal ganglia in the brain. This is commonly done for patients showing symptoms of Parkinson’s disease or similar diseases. In order to specify the severity of the disease, a scheme for calculating different fractions between parts of the dopamine transporter area is often used. This is tedious work for the person performing the quantification, and despite the acquired three dimensional images, quantification is too often performed on one or more slices of the image volume. In resemblance with myocardial perfusion examinations, variability between different operators can also here present a possible source of errors.</p><p>In this thesis, a novel method for automatically segmenting the left ventricle of the heart in SPECT-images is presented. The segmentation is based on an intensity-invariant local-phase based approach, thus removing the difficulty of the commonly varying intensity in myocardial perfusion images. Additionally, the method is used to estimate the angle of the left ventricle of the heart. Furthermore, the method is slightly adjusted, and a new approach on automatically quantifying dopamine transporters in the basal ganglia using the DaTSCAN radiotracer is proposed.</p>

Absolute quantification of I-131 activity in tumors and normal tissue is essential for internal dose estimates and is one of the greatest challenges in contemporary Nuclear Medicine. Therefore, for obtaining more accurate results, the most suitable and clinical applicable method, for both patients and scientists, for the quantification of I-131 has to be found. In the theoretical part of this project, the two methods for the quantitation are explained and analyzed as well as the factors that affect the obtained clinical image followed by the corrections that must be applied for gaining a more discrete image. For the planar technique, two methods for scatter and septal penetration correction were used applying two different matrix sizes specifically, 256x256 and 512x512 matrix sizes. On the other hand, for the SPECT technique, a 64x64 matrix size was used and a comparison between an auto-ROI and a same pattern of ROI segmentation that was produced manually for the purpose of this project, was performed. Furthermore, for patient specific dosimetry the total absorbed dose for the thyroid gland was calculated. Figures and tables for planar and SPECT technique were produced for each matrix size along with the final curve of the absorbed dose of the patient. For the planar technique it was observed that the method proposed by Anne Larsson, according to statistical analysis, gives results with lower statistical errors than the method proposed by Macey. In addition, 512x512 matrix size for the planar technique leads to lower statistical errors when compared with the results from using the 256x256 matrix size. Moreover, for the SPECT technique, the auto-sum that the software of the camera provides gives exactly the same results compared with the manual-sum. Finally, the total thyroid absorbed dose was 45,0472 Gy a result very close to the ICRU proposed dose value. / Η απόλυτη ποσοτικοποίηση της ενεργότητας του I-131 σε καρκινικούς και σε φυσιολογικούς ιστούς είναι απαραίτητη για την εκτίμηση της εσωτερικής δόσης και αποτελεί μία από τις μεγαλύτερες προκλήσεις της σύγχρονης Πυρηνικής Ιατρικής. Για τον λόγο αυτό, για την απόκτηση ακριβέστερων αποτελεσμάτων, θα πρέπει να βρεθεί η καταλληλότερη μέθοδος ποσοτικοποίησης, που να είναι εύχρηστη τόσο για τον ασθενή όσο και για το επιστημονικό προσωπικό των νοσοκομείων. Στο θεωρητικό μέρος της παρούσας εργασίας, αναλύονται οι δύο μέθοδοι ποσοτικοποίησης καθώς και οι παράγοντες που επηρεάζουν την ποιότητα της εικόνας ακολουθούμενοι από τους διορθωτικούς παράγοντες για την απόκτηση μιας ευκρινέστερης κλινικής εικόνας. Όσον αφορά την Planar τεχνική, περιγράφονται δύο μέθοδοι για διόρθωση της σκεδαζόμενης ακτινοβολίας καθώς επίσης και του septal penetration στην τελική εικόνα, χρησιμοποιώντας δύο διαφορετικά μεγέθη μήτρας, συγκεκριμένα, 256x256 και 512x512. Για την τεχνική SPECT, το μέγεθος μήτρας που χρησιμοποιήθηκε ήταν 64x64 και στην συνέχεια έγινε σύγκριση της περιοχής ενδιαφέροντος (ROI) που έδωσε το λογισμικό της κάμερας με την περιοχή ενδιαφέροντος που σχεδιάστηκε χειροκίνητα για την συγκεκριμένη μελέτη. Επίσης, υπολογίστηκε η συνολική απορροφούμενη δόση στον θυρεοειδή αδένα ενός ασθενούς. Κατασκευάστηκαν διαγράμματα τόσο για την planar όσο και για την SPECT τεχνική και για τα δύο μεγέθη μήτρας καθώς και η καμπύλη απορροφούμενης δόσης του ασθενούς. Παρατηρήθηκε ότι στην planar τεχνική, η μέθοδος που προτείνεται από την Anne Larsson, δίνει καλύτερα αποτελέσματα και μικρότερα σφάλματα συγκρινόμενη με την μέθοδο που προτείνεται από τον Macey. Επιπλέον, παρατηρήθηκε ότι το 512x512 μέγεθος μήτρας δίνει πιο ευκρινή εικόνα απ’ ότι το 256x256 μέγεθος μήτρας. Επίσης, με την SPECT τεχνική, παρατηρείται ότι χρησιμοποιώντας το αυτόματο άθροισμα των κρούσεων που δίνεται από το λογισμικό της κάμερας προκύπτουν τα ίδια ακριβώς αποτελέσματα με την χρήση του αθροίσματος των κρούσεων όταν αυτό γίνεται χειροκίνητα. Τέλος, η τελική απορροφούμενη δόση του ασθενούς υπολογίστηκε 45,0472 Gy, ένα αποτέλεσμα που δεν αποκλείει από τις τιμές που προτείνονται από το ICRU.

Absolute quantification of the 3D distribution of a radionuclide within a patient has been one of the greatest challenges of nuclear medicine. This is due to the fact that nuclear medicine images are degraded by several factors, which limit the quantitative ability of this modality. Quantitative SPECT has wide applications in many areas in nuclear medicine from radiation dosimetry calculations to clinical applications. It has use in image analysis studies to extract information about areas, volumes, and/or amounts of radioactivity in specific regions of interest. The information that derived from these studies is then applied to estimate radiation dosimetry, volumes or to aid in clinical diagnoses. Absolute quantitation means precise and accurate measurements of volume and the amount of radioactivity in a specific region of interest. For absolute quantitation of volume the measurements can be expressed in cubic centimetres, for radioactivity in μCi or Bq. Quantitation of organ volumes using planar imaging technique is a procedure often performed in nuclear medicine but face difficulties due to structure containing radioactivity, which overlie or underlie the organ of interest. SPECT overcomes these difficulties since it is able to separate these structures in the reconstructed images, which have higher contrast than planar images. In the theoretical part of this work, there is a description of the operation and the characteristics of a gamma camera system. Following that, there is a mention to the quality control procedures of the system both for planar and SPECT techniques. Also, there is an extended discussion of the factors that affect to the image quantitation and the corrections that must be applied in order to achieve better volume and activity estimation. At the end of the theoretical part, there is a presentation of procedure for volume and activity quantitation on I-131 sources using threshold technique. In the practical part, there is a study on volume and activity quantitation for I-131 sources with volumes 0.5,1,5,8,10,20 and activities from 300 to 529 μCi using threshold technique. The practical part of this work was performed in the department of Nuclear Medicine of the “THEAGENION” Cancer Institute of Thessaloniki (Greece), with association with the department of Medical Physics. / Η απόλυτη ποσοτικοποίηση της κατανομής ενός ραδιοφαρμάκου στον ασθενή, είναι μια από τις μεγαλύτερες προκλήσεις στην πυρηνική ιατρική, καθώς οι εικόνες από τη γ-κάμερα υποβαθμίζονται από διάφορους παράγοντες, που περιορίζουν την ικανότητα ποσοτικοποίησης. Η ποσοτικοποίηση μέσω SPECT έχει πολλές εφαρμογές στην πυρηνική ιατρική, στο διαγνωστικό τομέα και στο θεραπευτικό στη δοσιμετρία. Χρησιμοποιείται κατά την ανάλυση των εικόνων με σκοπό τον προσδιορισμό όγκων και την μέτρηση ραδιενέργειας σε συγκεκριμένες περιοχές ενδιαφέροντος. Η απόλυτη ποσοτικοποίηση σημαίνει σαφή και όσο το δυνατόν, ακριβή μέτρηση όγκου και ραδιενέργειας σε κάποια περιοχή ενδιαφέροντος. Ο όγκος μπορεί να εκφραστεί σε κυβικά εκατοστά και η ραδιενέργεια σε μCi ή Bq. Η ποσοτικοποίηση του όγκου των οργάνων, χρησιμοποιώντας planar τεχνικη, είναι μια διαδικασία που χρησιμοποιείται συχνά στην πυρηνική ιατρική. Παρ’όλα αυτά αντιμετωπίζει δυσκολίες λόγω των δομών, που βρίσκονται πάνω και κάτω από την περιοχή ενδιαφέροντος, και περιέχουν ραδιενέργεια. Το SPECT αντιμετωπίζει αυτές τις δυσκολίες, αφού έχει τη δυνατότητα να ξεχωρίσει αυτές τις δομές, στις εικόνες που έχουν ανακατασκευαστεί, και να τις παρουσιάσει με μεγαλύτερη αντίθεση από την planar τεχνική. Στο θεωρητικό μέρος της εργασίας γίνεται περιγραφή των χαρακτηριστικών και της λειτουργίας του απεικονιστικού συστήματος της γ-camera. Ακολουθεί η περιγραφή των διαδικασιών ποιοτικού έλεγχου του συστήματος τόσο για την Planar όσο και για την SPECT τεχνική. Στη συνέχεια, γίνεται παρουσίαση της μεθόδου ποσοτικοποίησης όγκου και ραδιενέργειας, στην περίπτωση πηγών Ι-131, εφαρμόζοντας την τεχνική κατωφλίου, ανάλυση των παραγόντων που την επηρεάζουν, καθώς και των διορθώσεων, που πρέπει να γίνονται, ώστε να επιτυγχάνεται η όσο το δυνατόν μεγαλύτερη ακρίβεια. Στο πειραματικό μέρος της εργασίας γίνεται εφαρμογή της παραπάνω μεθόδου σε πηγές Ι-131, όγκου 0.5-20 ml ραδιενέργειας 300-529μCi και σύγκριση των αποτελεσμάτων. Η συγκεκριμένη εργασία εκπονήθηκε στο Τμήμα Πυρηνικής Ιατρικής του ΑΝΘ ‘’ΘΕΑΓΕΝΕΙΟ’’ σε συνεργασία με το Τμήμα Ιατρικής Φυσικής του Νοσοκομείου.

No description available.

No description available.

No description available.