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Accuracy of positron emission tomography/computed tomography and clinical assessment in the detection of complete rectal tumor regression after neoadjuvant chemoradiation Long-Term Results of a Prospective Trial (National Clinical Trial 00254683)

Perez, Rodrigo Oliva; Habr-Gama, Angelita; Gama-Rodrigues, Joaquim; Proscurshim, Igor; Sao Juliao, Guilherme Pagin; Lynn, Patricio; Ono, Carla Rachel; Campos, Fabio Guilherme; Silva e Sousa, Afonso Henrique, Jr.; Imperiale, Antonio Rocco; Nahas, Sergio Ca
Fonte: WILEY-BLACKWELL; HOBOKEN Publicador: WILEY-BLACKWELL; HOBOKEN
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
96.32%
BACKGROUND: Neoadjuvant chemoradiation (CRT) therapy may result in significant tumor regression in patients with rectal cancer. Patients who develop complete tumor regression have been managed by treatment strategies that are alternatives to standard total mesorectal excision. Therefore, assessment of tumor response with positron emission tomography/computed tomography (PET/CT) after neoadjuvant treatment may offer relevant information for the selection of patients to receive alternative treatment strategies. METHODS: Patients with clinical T2 (cT2) through cT4NxM0 rectal adenocarcinoma were included prospectively. Neoadjuvant therapy consisted of 54 grays of radiation and 5-fluorouracil-based chemotherapy. Baseline PET/CT studies were obtained before CRT followed by PET/CT studies at 6 weeks and 12 weeks after the completion of CRT. Clinical assessment was performed at 12 weeks after CRT completion. PET/CT results were compared with clinical and pathologic data. RESULTS: In total, 99 patients were included in the study. Twenty-three patients were complete responders (16 had a complete clinical response, and 7 had a complete pathologic response). The PET/CT response evaluation at 12 weeks indicated that 18 patients had a complete response...

Alterações metabólicas cerebrais associadas aos fatores de risco cardiovascular: um estudo de tomografia por emissão de pósitron (PET); Abnormalities on brain metabolism associated to cardiovascular risk factors: a positron emission tomography (PET) study

Tamashiro-Duran, Jaqueline Hatsuko
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/12/2011 PT
Relevância na Pesquisa
96.38%
INTRODUÇÃO: Os fatores de risco cardiovascular (FRCV) afetam o fluxo sanguíneo cerebral, contribuindo possivelmente para o declínio cognitivo e a emergência da Doença de Alzheimer (DA), a forma mais comum de demência. A tomografia por emissão de pósitrons (positron emission tomography, PET) com fluordesoxiglucose F18 (18F-FDG) é largamente usada para demonstrar o padrão específico de metabolismo cerebral de glicose reduzido em sujeitos com DA e em indivíduos não-demenciados portadores do alelo e4 da apolipoproteína E (APOE e4), o maior fator de risco genético para DA. Entretanto, estudos de PET investigando o impacto dos FRCV no metabolismo cerebral são escassos. OBJETIVO: Examinar se níveis diferentes de FRCV estariam associados com reduções na taxa de metabolismo cerebral de glicose (TMCG), envolvendo as regiões cerebrais afetadas nos estágios iniciais da DA (pré-cúneo e giro do cíngulo posterior, neocórtex parieto-temporal lateral e região hipocampal). MÉTODOS: Nós avaliamos 59 indivíduos cognitivamente preservados (66-75 anos) subdivididos em três grupos de acordo com seu escore para Framingham Coronary Heart Disease Risk (FCHDR) (alto-risco, médio-risco e baixo-risco) para os exames de ressonância magnética (RM) e de PET-FDG. Dados de PET foram corrigidos para os efeitos de volume parcial a fim de evitar efeitos confundidores devido à atrofia cerebral regional. Nós realizamos uma análise de covariância global (ANCOVA) para investigar as reduções de TMCG em associação com os três grupos...

Tomografia por emissão de pósitrons com sistemas PET/SPECT: Um estudo da viabilidade de quantificação; Positron Emission Tomography PET / SPECT Systems Study Viability Quantification

Pozzo, Lorena
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/03/2005 PT
Relevância na Pesquisa
96.42%
A Tomografia por Emissão de Pósitrons (PET - Positron Emission Tomography) é uma modalidade de imagens para o diagnóstico em Medicina Nuclear. São utilizados radiofármacos emissores de pósitrons que possibilitam obter imagens que representam o processo bioquímico dessas substâncias no órgão ou tecido de interesse in vivo. São detectados, em coincidência, os fótons provenientes da aniquilação pósitron/elétron, que ocorre dentro do corpo do paciente. Esta informação é posteriormente utilizada para a reconstrução do objeto em estudo. Atualmente, existem dois tipos de equipamentos capazes de realizar estudos tomográficos por emissão de pósitrons: o dedicado e a câmara PET/SPCET. Este trabalho abordou este último tipo, que permite também a realização de exames habituais de Medicina Nuclear, que usam emissores de fótons. Existem dificuldades inerentes ao método de aquisição destas imagens que afetam a quantificação de índices ou atividade. Elas estão relacionadas ao fato de a emissão de radiação obedecer a uma distribuição de Poisson, às interações físicas da radiação com o corpo do paciente e com o detector, ao ruído devido à natureza estatística destas interações e de todo o processo de detecção...

Avaliação do desempenho de um sistema de tomografia PET com geometria elipsoidal; Performance evaluation of a system for PET tomography ellipsoidal geometry.

Bertolo, Antonio Carlos Nunes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/05/2014 PT
Relevância na Pesquisa
76.27%
Dentre as técnicas diagnósticas por imagem, em Medicina Nuclear, têm-se destacado a Tomografia por Emissão de Pósitrons (PET). O PET fornece imagens funcionais da região ou órgão de interesse, possibilitanto o diagnóstico de várias doenças e, também, um mapeamento da evolução ou regressão das mesmas. Os atuais sistemas PET apresentam blocos de cristais arranjados em geometria circular, mas a busca por novos arranjos, em geometrias diferenciadas, é pertinente, pois pode possibilitar um melhor desempenho destes tomógrafos. O objetivo deste estudo é avaliar o desempenho de um sistema PET constituído por blocos de cristais em arranjo elipsoidal. Para tal estudo, fez-se uso do GATE, ambiente de simulação para tomografia por emissão que apresentou resultados satisfatórios comparados à aparelhos utilizados na rotina clínica. Desta forma, elaborou-se dois sistemas PET, o primeiro com 46 blocos de cristais arranjados em geometria circular, no qual, os detectores opostos foram separados a uma distância de 816,4 mm na direção transaxial. No segundo caso, utilizou-se 36 blocos de cristais, arranjados em geometria elíptica, onde os detectores foram separados a uma distância de 500 mm na direção vertical e 816...

Estudo das variáveis de prognóstico clínico, da PET e PET/CT com 18FDG tomografia por emissão de pósitron/tomografia computadorizada ínterim, e do conceito de célula de origem por imuno-histoquímica em pacientes com linfoma difuso de grandes células B tratados com quimioimunoterapia; Study of clinical prognostic factors, interim PET and PET/CT with 18-FDG positron emission tomography/computed tomography, and immunohistochemistry cell of origin in patients

Costa, Renata de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/04/2015 PT
Relevância na Pesquisa
96.32%
O linfoma difuso de grandes células B (LDGCB) é o linfoma não-Hodgkin mais comum em nossa instituição (49,5%) e a classificação da Organização Mundial da Saúde reconhece vários subtipos de LDGCB com base na morfologia, imuno-histoquímica (IHQ) e perfil molecular. Metade dos pacientes permanecem incuráveis com terapia padrão baseada no anticorpo monoclonal anti-CD20 (rituximabe) e quimioterapia baseada em antraciclina. Portanto, é necessário identificar pacientes de alto risco e melhorar o seu prognóstico. Na era pré-rituximabe, a melhor maneira de identificar esse grupo de alto risco baseava-se no Índice de Prognóstico Internacional (IPI). Mais recentemente, grande interesse em subtipos moleculares e a caracterização da assinatura gênica das células malignas têm sido publicados. Pacientes com perfil de expressão gênica do centro germinativo (CG) parecem ter melhor prognóstico do que aqueles com assinatura de células B ativadas. Algoritmos IHC correspondentes foram propostos e o de Hans é o mais usado. No entanto, estes indicadores prognósticos têm sido questionados na era rituximabe. Além da classificação molecular, imagem funcional das células tumorais com 18F-fluodesoxiglucose (18F-FDG), a tomografia por emissão de pósitrons (PET/CT) tem sido recomendada ao diagnóstico e final do tratamento para aumentar a acurácia do estadiamento e avaliação de resposta. Embora alguns estudos tenham demonstrado que PET ínterim pode prognosticar a eficácia do tratamento...

Not all that shines is cancer: pulmonary cryptococcosis mimicking lymphoma in [(18)] F fluoro-2-deoxy-D-glucose positron emission tomography

Hamerschlak,Nelson; Pasternak,Jacyr; Wagner,Jairo; Perini,Guilherme Fleury
Fonte: Instituto Israelita de Ensino e Pesquisa Albert Einstein Publicador: Instituto Israelita de Ensino e Pesquisa Albert Einstein
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
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We report of a case of pulmonary cryptococcosis mimicking lymphoma in a positron emission tomography (FDG-PET) scan. A 62-year old man with diffuse large B-cell lymphoma had complete resolution of abdominal and pulmonary lesions after three cycles of rituximab-based chemotherapy (R-CHOP). However, FDG-PET showed new pulmonary nodules, suggesting active lymphoma. Chronic inflammatory granuloma was seen in the histopathological exam, with round-shaped structures compatible with fungus, later identified as Cryptococcus neoformans on culture. The lesions disappeared after 6 weeks of fluconazole therapy, and the patient could continue chemotherapy without further infectious complications.

Hibernoma - Intense uptake seen on Tc-99m tetrofosmin and FDG positron emission tomographic scanning

Chatterton, B.; Mensforth, D.; Coventry, B.; Cohen, P.
Fonte: Lippincott Williams & Wilkins Publicador: Lippincott Williams & Wilkins
Tipo: Artigo de Revista Científica
Publicado em //2002 EN
Relevância na Pesquisa
86.25%
A 65-year-old man with several subcutaneous masses (clinically diagnosed as lipomata), underwent Tc-99m tetrofosmin scanning for chest pain. One of these masses (in the right thigh) was incidentally noted to take up tetrofosmin. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a fat-containing lesion, and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET or C-PET) showed active uptake. Biopsy showed the lesion to be a hibemoma. Hibemoma is a benign but metabolically active tumor of brown fat origin. Brown fat is a major heat producer in the newborn and contains high levels of mitochondria. This high metabolic rate probably explains the uptake of Tc-99m tetrofosmin and F-18 FDG. Nevertheless, without a biopsy, the imaging studies could not exclude liposarcoma.; http://cat.inist.fr/?aModele=afficheN&cpsidt=13638310; http://journals.lww.com/nuclearmed/Citation/2002/05000/Hibernoma__Intense_Uptake_Seen_on_Tc_99m.16.aspx; Barry E. Chatterton, Dominic Mensforth, Brendon J. Coventry and Penelope Cohen

Der Beitrag der Positronen-Emissions-Tomographie mit F-18-Fluorodeoxyglucose zur Diagnostik bei Patienten mit CUP-Syndrom; The contribution of Positron Emission Tomography with F-18 fluorodeoxyglucose in the diagnostic work-up of patients with CUP syndrome

Aschoff, Philip
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
96.31%
Hintergrund und Fragestellung: Das CUP-Syndrom bezeichnet das Auftreten von Metastasen eines unbekannten Primärtumors (Cancer of Unknown Primary). In dieser Situation sind die Lokalisation des Primärtumors, die Ausdehnung der Metastasierung und potentielle tumorbedingte Komplikationen prognosebestimmende Faktoren. Ihre Kenntnis ist entscheidend für die Auswahl einer adäquaten kurativen oder palliativen Therapie. Die Positronen-Emissions-Tomographie mit F-18-Fluorodeoxyglucose (FDG-PET) wird mit diesen Fragestellungen in zunehmendem Maße als diagnostische Methode beim CUP-Syndrom eingesetzt. Ziel dieser Arbeit war es, den Beitrag zu evaluieren, den die FDG-PET im klinischen Alltag an einem nicht-universitären Krankenhaus der Maximalversorgung zur Detektion von Primärtumoren, zur Detektion bzw. zum Ausschluss weiterer, bislang nicht bekannter Metastasen und zur Detektion von potentiellen, therapierelevanten, komplikationsträchtigen Befunden beim CUP-Syndrom liefert. Weiterhin wurde der zusätzliche Nutzen der Computertomographie (CT) in der kombinierten FDG-PET/CT untersucht. Patienten und Methoden: Es erfolgte eine retrospektive Analyse der Untersuchungsergebnisse von 244 Patienten mit CUP-Syndrom, die mittels FDG-PET (Serie A...

Validierung der potentialorientierten Substratablation ventrikulärer Tachykardien bei Postinfarktpatienten mittels Positronenemissionstomographie; Validation of the potential orientated substrat ablation technique with positron emission tomography

Schwegler, Alexandra
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
96.25%
Viele Patienten mit Zustand nach Myokardinfarkt entwickeln ventrikuläre Tachykardien (VT). Bei Patienten, welche trotz Antiarrhythmikagabe an rezidivierenden Schocks durch den Defibrillator leiden, kann im Rahmen einer elektrophysiologischen Untersuchung (EPU) das arrythmogene Gewebe durch Radiofrequenzenergie zerstört werden (Ablation). Bei der so genannten substratorientierten Ablation werden Ablationslinien im Sinusrhythmus anhand von Elektrogrammkriterien für Narben und Narbenrandgebiete gezogen. Ein wichtiges Kriterium ist hierbei die Höhe der bipolaren Elektrogrammamplitude. Ablationspunkte werde meist nur in Elektrogrammamplitudenbereichen unter 1,5mV gesetzt. Dieser Grenzwert wurde anhand geringer Fallzahlen definiert. Es wurde auch nicht geprüft, bis zu welchem Elektrogrammamplitudenbereich Myokardgewebe Vitalität aufweist. Die Etablierung eines verbindlichen Grenzwertes ist wichtig um bei der Ablation kein vitales Myokard zu zerstören, denn dies könnte die ventrikuläre Funktion zusätzlich schwächen. Methoden: Wir führten eine EPU bei 7 VT-Patienten mit Zustand nach Myokardinfarkt durch und erstellten elektroanatomische Landkarten der linken Ventrikel mit Darstellung der bipolaren Elektrogrammamplituden auf der Ventrikeloberfläche. Als Referenzmethode zur Definition myokardialer Vitalität wählten wir eine Stoffwechseluntersuchung mittels Positronenemissionstomographie (PET) mit radioaktiv markierter Fluordesoxyglukose (18F-FDG). Es wurde ein Bild der linksventrikulären 18F-FDG-Aufnahme rekonstruiert. Beide Ventikelbilder wurde in gleicher Weise segmental aufgeteilt und korrespondierende Segmente beider Untersuchungen miteinander verglichen. So konnten die bipolare Elektrogrammamplituden mit der 18F-FDG Aufnahme in 424 Segmenten (42–84 Segmente pro Patient) korreliert werden. Ergebnisse: Die Korrelation zwischen bipolarer Elektrogrammamplitude und 18F-FDG-Aufnahme ist signifikant (p<0...

Monte Carlo Simulations in Positron Emission Tomography Reconstruction - Full matrix, dual matrix, and system matrix compression; Monte Carlo Simulationen in der PET-Bildrekonstruktion - Full Matrix, Dual Matrix und Matrixkompression

Rehfeld, Niklas Sebastian
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
96.3%
In positron emission tomography (PET) emission density images are formed by photon coincidence measurements. This process is complicated, particularly with regard to the photons that can be scattered in the inhomogeneous patient. A method to incorporate Monte Carlo simulations into the image formation process to model the scattering is presented. This is achieved by simulating the system matrix that describes the map from emission density to detected coincidences. The problem of the very large size of the matrix is met by fitting and B-spline compression of Monte Carlo results. A dedicated Monte Carlo code for system matrix calculation using variance reduction techniques is presented to reduce simulation time. Other desirable properties like reduced sensitivity to Monte Carlo noise and the possibility for sequential compression are met by the presented compression method. In proof-of-principle simulations of single ring scanners it is shown that the matrices compressed by this scheme are good approximations to the uncompressed matrices and that scatter artifacts in the images are strongly suppressed. In the last part, noise in the images introduced by the noise of the Monte Carlo simulated system matrices is investigated and quantified.; In der Photonenemissionstomographie (PET) werden Bilder der Aktivitätsverteilung aus Photonen-Koinzidenzmessungen errechnet. Das ist insbesondere wegen der Streuung der Photonen im inhomogenen Patienten kompliziert. In der vorgestellten Methode werden Monte Carlo Simulationen in der Bildberechnung benutzt...

Modelling and Simulation of Hypoxia Imaging with Positron Emission Tomography; Modellierung und Simulation der Hypoxie-Bildgebung mittels Positronen-Emissions-Tomographie

Mönnich, David
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
96.25%
The presence of oxygen deprived (hypoxic) tissue regions in human tumours is associated with a reduced effectiveness of different treatment modalities. This effect is especially important in radiotherapy (RT) using photons with energies in the MeV range. In order to achieve high control probabilities with RT also for hypoxic tumours, it has been proposed to increase the radiation dose in hypoxic regions. For this purpose a three-dimensional assessment of the distribution and degree of hypoxia is required. This is possible with positron emission tomography (PET) in combination with the tracer 18F-Fluoromisonidazole (FMISO), as its accumulation is increased at low oxygen partial pressures (PO2). FMISO PET has a number of fundamental limitations: Its low spatial resolution (millimetres) results in large averaging effects. Moreover, FMISO accumulates in vital cells only and its diffusive distribution in tissue is slow. In this thesis, the effects of these limitations on clinical FMISO PET imaging were investigated using computer simulations. The coupled diffusion-reaction processes of O2 and FMISO on the microscopic length scale were incorporated in a mathematical model. The resulting partial differential equations were treated numerically using the finite element method. The flux of molecules across vessel membranes into and out of tissue was modelled by biologically realistic boundary conditions. For this purpose vessel distributions were created based on tumour tissue microsections. Applying this method...

Optimization of novel developments in Positron Emission Tomography (PET) imaging

Chang, Tingting
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
96.25%
Positron Emission Tomography (PET) is a widely used imaging modality for diagnosing patients with cancer. Recently, there have been three novel developments in PET imaging aiming to increase PET image quality and quantification. This thesis focuses on the optimization of PET image quality on these three developments. The first development is the fully 3D PET data acquisition and reconstruction. 3D Acquisitions are not constrained in collecting events in single 2D planes and can span across different planes. 3D acquisition provides better detection since it can accept more events. Also it can result in lower radiation dose to the patient and shorter imaging times. With the application of 3D acquisition, a fully 3D iterative reconstruction algorithm was also developed. The aim of the first project in this thesis is to evaluate the PET image and raw data quality when this fully 3D iterative reconstruction algorithm is applied. The second development in PET imaging is the time-of-flight (TOF) PET data acquisition and reconstruction. TOF imaging has the ability to measure the difference between the detection times, thus localize the event location more accurately to increase the image quality. The second project in this thesis focuses on optimizing the TOF reconstruction parameters on a newly developed TOF PET scanner. Then the improvement of TOF information on image quality is assessed using the derived optimal parameters. Finally the effect of scan duration is evaluated to determine whether similar image quality could be obtained between TOF and non-TOF while using less scan time for TOF. The third development is the interest in building PET / magnetic resonance (MR) multi-modality scanner. MR imaging has the ability to show high soft tissue contrast and can assess physiological processes...

Real-Time Digital Timing in Positron Emission Tomography

Guerra, P.; Ortuño, Juan E.; Kontaxakis, G.; Ledesma-Carbayo, M. J.; Vaquero, Juan José; Desco, Manuel; Santos, Andrés
Fonte: IEEE Publicador: IEEE
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/article Formato: application/octet-stream; application/octet-stream; application/pdf
Publicado em 08/12/2008 ENG
Relevância na Pesquisa
96.25%
Positron emission tomography (PET) requires accurate timing of scintillation events to properly discriminate between coincident and noncoincident pairs. The traditional solution to timing is based on custom application specific integrated circuits (ASIC) designs, whose cost may not be justified in the design of experimental small animal PET scanners. The new generation of PET scanners introduces the idea of continuous sampling of the detected scintillation pulse, replacing event-triggered acquisition front-ends. This approach enables new options to the timing procedure based on digital processing of the sampled pulse signal. This work proposes a time stamping algorithm based on the optically matched filter and compares the potential performance benefits of this approach versus other FIR-based timing algorithms, some of which have been already implemented by different authors. Results show that the coincidence timing resolution may be as low as 1.5 ns without the need of expensive high-speed converters when the proper signal processing is applied; IEEE Nuclear and Plasma Sciences Society

Budget impact from the incorporation of positron emission tomography – computed tomography for staging lung cancers

Biz,Aline Navega; Caetano,Rosângela
Fonte: Faculdade de Saúde Pública da Universidade de São Paulo Publicador: Faculdade de Saúde Pública da Universidade de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
96.31%
OBJECTIVE To estimate the budget impact from the incorporation of positron emission tomography (PET) in mediastinal and distant staging of non-small cell lung cancer.METHODS The estimates were calculated by the epidemiological method for years 2014 to 2018. Nation-wide data were used about the incidence; data on distribution of the disease´s prevalence and on the technologies’ accuracy were from the literature; data regarding involved costs were taken from a micro-costing study and from Brazilian Unified Health System (SUS) database. Two strategies for using PET were analyzed: the offer to all newly-diagnosed patients, and the restricted offer to the ones who had negative results in previous computed tomography (CT) exams. Univariate and extreme scenarios sensitivity analyses were conducted to evaluate the influence from sources of uncertainties in the parameters used.RESULTS The incorporation of PET-CT in SUS would imply the need for additional resources of 158.1 BRL (98.2 USD) million for the restricted offer and 202.7 BRL (125.9 USD) million for the inclusive offer in five years, with a difference of 44.6 BRL (27.7 USD) million between the two offer strategies within that period. In absolute terms, the total budget impact from its incorporation in SUS...

Verkürzung der Transmissionszeit bei einem Positronen-Emissions-Tomographen (PET) durch die segmentierte Schwächungskorrektur; Reduction of transmission scan time on a Positron Emission Tomograph (PET) by segmented attenuation correction

Bilger, Kilian
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
DE_DE
Relevância na Pesquisa
86.25%
Die Positronen-Emissions-Tomographie (PET) ist ein bildgebendes nuklearmedizinisches Verfahren, mit dem Stoffwechselvorgänge quantitativ analysiert werden können. Die wichtigste Korrektur um quantitative Bilder zu erhalten, ist die Korrektur der im Patienten absorbierten Photonen. Die Standardmethode der Schwächungskorrektur (Messung der Patientenschwächung im Koinzidenzmodus) benötigt, um eine ausreichende Bildqualität zu gewährleisten, eine Meßzeit von 15-20min pro Bettposition (~15cm). Diese Meßzeit kann durch den Einsatz der 'segmentierten Schwächungskorrektur' (SAC) verkürzt werden. Das Ziel der Arbeit war die Reduktion der Transmissionsmeßzeit bei einem GE ADVANCE Scanner. Es wurden drei Verfahren entwickelt und getestet: 1. TSH = Transmissions-Segmentierung mit Histogramm-Fit 2. TSF = Transmissions-Segmentierung mit Fuzzy-Inferenz 3. ESF = Emissions-Segmentierung mit Fuzzy-Inferenz Mit TSH konnte eine klinische Transmissionszeit von 50s-90s pro Bettposition ohne Verlust an Genauigkeit erreicht werden. Das Verfahren ist damit im Vergleich zu dem seit diesem Jahr herstellerseitig angebotenen Segmentierungstools um den Faktor 2 schneller. Die Segmentierung mit TSH wurde 1997 zusammen mit der iterativen Rekonstruktion für Emissionsdaten als Programmpaket 'SAC/IR' in der klinischen Routine als Standardverfahren integriert und seither bei allen Ganzkörperuntersuchungen angewendet. Mit Fuzzy Logic (TSF) und den lokalen Korrekturen kann im Vergleich zur Standardsegmentierung noch ein Zugewinn von 10-15s in der Meßzeit erreicht werden. Mit dem dritten System - ESF - lassen sich Genauigkeiten von 10-15 ohne Transmissionsmessung erreichen...

Avaliando a difusão de tecnologias médicas no sistema de saúde privado no Brasil: o caso da tomografia por emissão de pósitrons (PET); Assessing the use of medical technology in the private health system in Brazil: the case of Positron Emission Tomography (PET)

VIANA, Ana Luiza d´Ávila; SILVA, Hudson Pacífico da
Fonte: Instituto de Medicina Integral Prof. Fernando Figueira Publicador: Instituto de Medicina Integral Prof. Fernando Figueira
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
96.25%
OBJETIVOS: analisar os determinantes da difusão da tomografia por emissão de pósitrons (PET) em um conjunto selecionado de prestadores de serviços e operadoras de planos de saúde no Brasil. MÉTODOS: estudo de caso qualitativo, com coleta de dados realizada por meio de entrevistas em profundidade (N=9) com representantes de quatro prestadores de serviços de saúde privados e três operadoras de planos de saúde. RESULTADOS: as decisões para aquisição da tecnologia estudada são tomadas por dirigentes de hospitais e clínicas que adotam uma estratégia de diferenciação baseada em liderança tecnológica. Os fatores que influenciam essa decisão são: histórico de pioneirismo da instituição na incorporação de tecnologias; pressão do corpo clínico vinculado à instituição; prestígio do médico ou da área demandante; disponibilidade de recursos financeiros; acesso facilitado à tecnologia; concorrência entre os prestadores de serviços de saúde; evidências científicas; e rentabilidade do investimento. CONCLUSÕES: os atuais instrumentos de política usados para gerenciar a difusão de tecnologias médicas no sistema de saúde brasileiro exercem pouca influência nas decisões de grandes prestadores privados, cujas atividades não estão necessariamente relacionadas com as necessidades de saúde da população ou com as prioridades da política de saúde.; OBJECTIVES: to analyze the determining factors underlying the extent to which positron emission tomography (PET) is used in a selected medical services provider covered by private health insurance plans in Brazil. METHODS: a qualitative case study was undertaken with data collected by means of in-depth interviews (N=9) with representatives of four private health service providers and three health insurance plan operators. RESULTS: the decisions to acquire the technology under study are taken by managers of hospitals and clinics that adopt a strategy based on excellence in technology. The factors that influence the decision are: a history of being pioneers in the introduction of new technology; pressure from the institution's clinical staff; the prestige of the physician or the area covered by the unit; the financial resources available; ease of access to technology; competition among health service providers; scientific evidence; and the expected return on the investment. CONCLUSIONS: the policy instruments currently used to manage the use of medical technology in the Brazilian health system has little influence on the decisions made by large-scale private service providers...

Changes in F18-flurodeoxyglucose uptake on serial cardiac positron emission tomography and left ventricular ejection fraction in patients with cardiac sarcoidosis

Osborne, Michael T.; Hulten, Edward A.; Singh, Avinainder; Waller, Alfonso H.; Bittencourt, Márcio Sommer; Stewart, Garrick C.; Skali, Hicham; Hainer, Jon; Dorbala, Sharmila; Di Carli, Marcelo F.; Blankstein, Ron
Fonte: American Heart Association; Dallas Publicador: American Heart Association; Dallas
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
96.25%
lntroduction: Cardiac positron emission tomography (PET) using F18-fluorodeoxyglucose (FDG) has been used to diagnose and monitor cardiac sarcoidosis (CS). It is not yet known whether a reduction in myocardial inflammation, as measured by FDG uptake, is associated with improvement in LV ejection fraction (EF). Methods: For 23 patients with CS (83% diagnosed by biopsy, 17% clinically) followed by a-total of 90 serial PET exams (median 4 per patient), two physicians blinded to EF quantified the maximum standardized uptake value (SUV) and volume of FDG to assess lhe intensity and extent of FDG uptake on each study. Using gated rubidium rest perfusion images, EF was measured by a physician blind to all clinical and FDG data. To account for clustering and differences in scan frequency, a mixed effects model was used to evaluate the relationship between FDG uptake and changes in EF on interval scans. Results : Among 23 patients with serial PETexams (mean age 49,74% male, mean baseline EF 43± 13%) the median time between the first and last scan was 2.0 years. Overall, 91% were treated with corticosteroids, 78% with ACE/ARB, 83% with beta-blockers and 83% had ICDs. Mixed modeling demonstrated a significant inverse linear relationship with an expected increase in EF'of 7.9% per SUV reduction of 10 g/mL (p≤ 0.008) and an increase of 3.8% per SUV volume reduction of 100 cm3 (p≤ 0.022). Conclusions: In a longitudinal cohort of CS patients...

Consensus Segmentation for Positron Emission Tomography: Development and Applications in Radiation Therapy

McGurk, Ross
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2013
Relevância na Pesquisa
96.29%

The use of positron emission tomography (PET) in radiation therapy has continued to grow, especially since the development of combined computed tomography (CT) and PET imaging system in the early 1990s. Today, the biggest use of PET-CT is in oncology, where a glucose analog radiotracer is rapidly incorporated into the metabolic pathways of a variety of cancers. Images representing the in-vivo distribution of this radiotracer are used for the staging, delineation and assessment of treatment response of patients undergoing chemotherapy or radiation therapy. While PET offers the ability to provide functional information, the imaging quality of PET is adversely affected by its lower spatial resolution. It also has unfavorable image noise characteristics due to radiation dose concerns and patient compliance. These factors result in PET images having less detail and lower signal-to-noise (SNR) properties compared to images produced by CT. This complicates the use of PET within many areas of radiation oncology, but particularly the delineation of targets for radiation therapy and the assessment of patient response to therapy. The development of segmentation methods that can provide accurate object identification in PET images under a variety of imaging conditions has been a goal of the imaging community for years. The goal of this thesis are to: (1) investigate the effect of filtering on segmentation methods; (2) investigate whether combining individual segmentation methods can improve segmentation accuracy; (3) investigate whether the consensus volumes can be useful in aiding physicians of different experience in defining gross tumor volumes (GTV) for head-and-neck cancer patients; and (4) to investigate whether consensus volumes can be useful in assessing early treatment response in head-and-neck cancer patients.

For this dissertation work...

Emission Tomography: SPECT and PET

Chow Robilotta,Cecil
Fonte: Centro de Investigación en computación, IPN Publicador: Centro de Investigación en computación, IPN
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2004 EN
Relevância na Pesquisa
76.32%
Emission tomography is a medical image modality that utilizes molecules labelled with radionuclides, the radiopharmaceuticals, to obtain functional information about specific tissues or systems. In SPECT, Single Photon Emission Computerized Tomography, the radionuclide decays by emitting one or more photons, while in PET, Positron Emission Tomography, the radionuclide emits a positron, in order to reach a lower energy level. Although the forms of energy emitted are different, the images are reconstructed from the information acquired by external detection of the emitted photons (SPECT) and the pair of annihilation photons (PET) in coincidence. Due to the specificity and characteristics of these images, their information can be quantified, so that functional or metabolic parameters can be obtained for diagnostic or therapeutic purposes. However, in order to achieve reliable results, factors related to the instrumentation and patient conditions, as well as to the interactions between radiations and tissues and the reconstruction methods have to be considered carefully. In this lecture, after the introduction of the fundamentals of nuclear medicine imaging, the basis of emission tomography acquisition and reconstruction will be presented. Some correction methods will be introduced in order to exemplify the current quantifications adopted in the clinical routine of molecular imaging.

Budget impact from the incorporation of positron emission tomography – computed tomography for staging lung cancers

Biz,Aline Navega; Caetano,Rosângela
Fonte: Faculdade de Saúde Pública da Universidade de São Paulo Publicador: Faculdade de Saúde Pública da Universidade de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
96.31%
OBJECTIVE To estimate the budget impact from the incorporation of positron emission tomography (PET) in mediastinal and distant staging of non-small cell lung cancer.METHODS The estimates were calculated by the epidemiological method for years 2014 to 2018. Nation-wide data were used about the incidence; data on distribution of the disease´s prevalence and on the technologies’ accuracy were from the literature; data regarding involved costs were taken from a micro-costing study and from Brazilian Unified Health System (SUS) database. Two strategies for using PET were analyzed: the offer to all newly-diagnosed patients, and the restricted offer to the ones who had negative results in previous computed tomography (CT) exams. Univariate and extreme scenarios sensitivity analyses were conducted to evaluate the influence from sources of uncertainties in the parameters used.RESULTS The incorporation of PET-CT in SUS would imply the need for additional resources of 158.1 BRL (98.2 USD) million for the restricted offer and 202.7 BRL (125.9 USD) million for the inclusive offer in five years, with a difference of 44.6 BRL (27.7 USD) million between the two offer strategies within that period. In absolute terms, the total budget impact from its incorporation in SUS...