Thesis--University of Oklahoma. / Bibliography: leaves 115-119.

Thesis--University of Oklahoma. / Bibliography: leaves 152-154.

Thesis--University of Oklahoma. / Bibliography: leaves 69-70.

Introdução: O uso da tomografia de múltiplos detectores para avaliar a doença arterial coronariana tem aumentado, fornecendo informações valiosas para rotina clínica. O risco potencial da exposição à radiação, por outro lado, exige manter a dose de radiação tão baixo quanto razoavelmente possível. Objetivo: testar e avaliar o ajuste de parâmetros de aquisição no bolus tracking (BT) para reduzir a dose de radiação nos exames de angiotomografias das artérias coronárias (ATCC), sem comprometer a qualidade da imagem. Métodos: Este é um estudo prospectivo de 289 pacientes que realizaram ATCC. Os pacientes foram distribuídos consecutivamente em 4 grupos: A (n = 70), B (n = 79), C (n = 68) e D (n = 72). O grupo A foi o protocolo de referência - recomendado pelo fabricante do tomógrafo. As imagens dos outros grupos foram adquiridas por parâmetros de configuração diferentes do BT, em tempo, para alcançar a redução da dose de radiação. As imagens da fase da angiografia, para todos os grupos, foram realizadas com configurações semelhantes. Foram avaliados parâmetros de qualidade de imagem qualitativa e quantitativamente e a exposição da radiação. Resultados: A dose de radiação do BT foi significativamente diferente entre os grupos, principalmente quando comparados os grupos D e A (p < 0,001), grupos C e A (p < 0,001) e grupos B e A (p < 0,001), com a maior redução no grupo D (redução de 50% em relação ao grupo A). Não houve nenhuma diferença significativa entre os grupos em relação à dose de radiação efetiva e à qualidade de imagem da fase angiográfica. No entanto, a dose de radiação efetiva total (BT + fase angiográfica) foi estatisticamente diferente entre os grupos A e D (p = 0,025). Conclusão: O ajuste do tempo para a aquisição do BT reduz significativamente a dose de radiação efetiva em até 50%, sem reduzir a qualidade da imagem, oferecendo uma nova perspectiva para a redução da radiação total durante a ATCC / Introduction: Modern multidetector computed tomography scanners for assessing coronary artery disease have been growing in use, providing valuable information in clinical routine. The potential risk of radiation exposure, on the other hand, requires keeping radiation dose as low as reasonably achievable. Objectives: Test and evaluate the bolus tracking (BT) acquisition parameters adjustment to reduce radiation dose in coronary computed tomography angiography (CCTA), without compromising image quality. Methods: This is a prospective study of 289 patients referred to CCTA. Patients were consecutively distributed into 4 groups: A (n=70), B (n=79), C (n=68) and D (n=72). Group A was the reference protocol - recommended by the scanner manufacturer. The images of other groups were acquired by setting different time BT parameters in order to achieve radiation dose reduction. The images of angiography phase for all groups were performed with similar settings. Qualitative and quantitative image quality parameters and radiation exposures were evaluated. BT radiation dose was significantly different among groups, mainly when comparing groups D and A (p < 0.001), groups C and A (p < 0.001) and groups B and A (p < 0.001), with the highest reduction in group D (50% reduction in relation to group A). There was no significant difference between groups regarding effective radiation dose for the angiographic phase or image quality. However, total effective radiation dose (BT + angiographic phase) was statistically different between groups A and D (p= 0.025). Conclusion: Time adjustment of BT acquisition significantly reduces effective radiation dose in up to 50%, without reducing image quality, offering a new perspective for total radiation reduction during CCTA

Le but de notre travail a été d’évaluer l’effet de la réduction de la dose d’irradiation en TDM multibarrette quant à la performance diagnostique, la confiance de l’observateur dans le diagnostic proposé, la capacité à suggérer un diagnostic alternatif dans quelques pathologies courantes et/ou caractérisées par des situations de faibles contrastes entre les structures anatomiques normales ou pathologiques. Nous avons donc comparé ces paramètres entre des TDM à doses réduites et à doses standard telles que couramment rapportées dans la littérature dans les circonstances suivantes :<p><p>•\ / Doctorat en sciences médicales / info:eu-repo/semantics/nonPublished

<p>Cilj: Proveriti da li je moguće promeniti način CT verifikacije Hallerovog indeksa u okviru preoperativne pripreme pacijenata sa deformitetom grudnog ko&scaron;a po tipu pectus excavatum-a, uz utvrđivanje fiziolo&scaron;kog opsega vrednosti indeksa, njegove zavisnosti od uzrasta i pola, kao i respiratorne faze u kojoj se CT pregled izvodi. Utvrditi značaj vrednosti indeksa korekcije, indeksa asimetrije i indeksa torzije sternuma. Proveriti i mogućnost smanjivanja efektivne doze jonizujućeg zračenja kod primene CT tehnike jednog skena (single slice). Materijal i metod rada: Ispitivanje se sastojalo iz prospektivne studije koja je obuhvatila 30 pacijenata sa pektus ekskavatumom uz CT snimanje (single slice) u respiratornim fazama: ekspirijum i inspirijum. Na dobijenim snimcima su izračunati pored Halerovog indeksa i indeksi asimetrije, korekcije i sternalne torzije. Prema dobijenim rezultatima merenja i izračunavanja, dono&scaron;ena je odluka o načinu terapijskog tretmana. U retrospektivnoj studiji, urađena je analiza 100 CT pregleda grudnog ko&scaron;a kod dece gde nije verifikovan pectus excavatum, uz kalibriranje vrednosti indeksa u odnosu na uzrast i pol pacijenata. Retrospektivno istraživanje je obuhvatilo i analizu dodatnih 30 CT pregleda grudnog ko&scaron;a pacijenata sa deformitetom grudnog ko&scaron;a po tipu pectus excavatum-a, koji su dijagnostikovani i/ili operisani. Kod svih operisanih pacijenata je primenjenja Nusova operativna tehnika. U ovoj grupi pacijenata je izračunata srednja vrednost efektivne doze jonizujućeg zračenja, a dobijene vrednosti su potom komparirane sa efektivnim dozama koje su dobijene niskodoznim CT pregledima grudnog ko&scaron;a uz primenu novog protokola (&quot;single-slice&quot; tehnika u respiratornim fazama inspirijuma i ekspirijuma). Rezultati: Fiziolo&scaron;ki opseg vrednosti Haller-ovog indeksa u populaciji zdravih pacijenata se kretao od 1,47 do 3,17 i u proseku je iznosio 2,23&plusmn;0,32 (znatna pozitivna korelacija uzrasta i vrednosti HI). Na osnovu rezultata Man-Vitnijevog testa nije postojala polna razlika u posmatranoj grupi. Haller-ov indeks u grupi dijagnostikovane/operisane dece je u proseku iznosio 3,39 i kretao se u intervalu od 2,23 do 5,72 (korelacija između uzrasta ovih pacijenata i Haller-ovog indeksa je bila neznatna i negativna). Utvrđena je zavisnost veličine Haller-ovog indeksa od respiratorne faze u kojoj se CT pregled izvodi. Tako su prosečne vrednosti Haller-ovog indeksa u inspirijumu dece sa dijagnostikovanim deformitetom iznosile 2,69&plusmn;0,76. Kod dece ove grupe u ekspirijumu vrednosti Haller-ovog indeksa su iznosile 3,49&plusmn;1,19. U inspirijumu su samo 3/32 (9%) ispitanika imali vrednost HI preko 3,25 (granična vrednost za operativni tretman), dok ih je u ekspirijumu bilo znatno vi&scaron;e 13/32 (41%), &scaron;to je statistički značajna razlika (&chi;2=6,250; df =1; p=0,012). &quot;Single-slice&quot; tehnika CT pregleda u inspirijumu i ekspirijumu 20-25 puta smanjuje efektivnu dozu jonizujućeg zračenja. Zaključak: Vrednost Haller-ovog indeksa raste sa uzrastom deteta, dok nije utvrđena zavisnost Haller-ovog indeksa od pola. Moguće je promeniti načini CT verifikacije Haller-ovog indeksa u preoperativnoj pripremi za Nuss-ovu operaciju primenom &quot;single-slice&quot; tehnike u ekspiratornoj fazi. Osim Hallerovog indeksa, korisno je određivati i indeks korekcije, indeks asimetrije i indeks sternalne rotacije. Predlaže se protokol standardne preoperativne pripreme i lečenja pacijenata dečjeg uzrasta sa deformitetom grudnog ko&scaron;a po tipu pektus ekskavatuma, sa ciljem njegove primene u svakodnevnom radu u institucijama koje se bave ovim problemom, a u cilju pobolj&scaron;anja kvaliteta dijagnostikovanja i krajnjeg ishoda lečenja.</p> / <p>Aim: The aim of this study was to verify whether it is possible to change the way of CT verification of Haller index (HI), as part of preoperative preparation for patients with pectus excavatum, with the determination of the physiological range of the index value, its dependence on the age and sex, as well as the respiratory phase during which the scan is performed. Also, the aim was to determine the significance of correction, asymmetry and sternal torsion indices values. Evaluate the possibility of reduction the effective dose of ionizing radiation using a single slice CT scan technique. Materials and methods: The study consisted of prospective study that included evaluation of CT scans (single slice technique) of 30 patients with pectus excavatum in both respiratory phases: expirium and inspirium. Haller index and indices of asymmetry, correction and sternal torsion were measured. The decision for the treatment was made according to the results of measurements and calculations of these indices. In retrospective study, 100 CT scans of the chest in children without the deformity (pectus excavatum) were analyzed, and the index value was calibrated depending on the age and gender. The retrospective study also included the analysis of another 30 CT scans in patients who were operated or diagnosed with pectus excavatum. Nuss procedure was used in all operated patients. In this group of patients the median value of effective dose of ionizing radiation was calculated, and the values were compared with the effective dose obtained using low-dose CT examinations applied in the new protocol (single-slice technique in inspiratory and expiratory respiratory phases). Results: The physiological range of Haller index value in healthy patients was from 1.47 to 3.17 and average value was 2.23&plusmn;0.32 (significant positive correlation between age and the value of HI). Results of Mann- Whitney test did not demonstrate any difference between gender in the observed group. In the group of patients who were operated/diagnosed with pectus excavatum the average value of Haller index was 3.39 within the range of 2.23 to 5.72 (correlation between the age of these patients and Haller index was negative, but not significant). The dependence of the Haller index value and certain respiratory phase during which the CT scan was performed also was determined. Thus, the average value of Haller index in inspirium in children with diagnosed deformity was up to 2.69&plusmn;0.76. In the same group of patients the value of Haller index in expirium was up to 3.49&plusmn;1.19. Only 3/32 (9%) patients had HI value over 3.25 (a boundary value for surgical treatment) during inspirium, while 13/32 (41%) patients had it in expirium, this data showed statistically significant difference (&chi;2=6.250; df=1; p=0.012). Single-slice CT technique during the inspiratory and expiratory phase reduces 20-25 times the effective dose of ionizing radiation. Conclusion: The value of Haller index increases with the age, but its dependence on the gender was not determined. It is possible to change the way of CT verification of Haller index in preoperative preparation for the Nuss operation using the &quot;single-slice&quot; technique in exspiratory phase. In addition to Haller index it is useful to determine correction index, the index of asymmetry and the index of sternal rotation as well. This protocol is proposed for standard preoperative preparation and treatment of pediatric population with pectus excavatum with the aim of its application in daily work in institutions that deal with this problem, but also to improve the quality of diagnosis and treatment outcomes.</p>

INTRODUÇÃO: Na Radioterapia, a acurácia da distribuição de dose em cálculos com correção de heterogeneidade está diretamente relacionada à escolha do algoritmo de cálculo. Existe uma variedade de algoritmos de cálculo disponíveis no mercado, variando em tempo de processamento e acurácia. Este estudo teve como objetivos quantificar a acurácia de dez diferentes algoritmos de cálculo em objetos simuladores de pulmão e analisar o impacto da escolha do algoritmo na distribuição de dose em radioterapia aplicada a tumores de pulmão. METODOLOGIA: Foram utilizados placas simuladoras de água (água sólida RW3) e pulmão (cortiça) para determinar a Porcentagem de Dose em Profundidade (PDP) e perfil transversal dentro da heterogeneidade (cortiça). As medidas foram realizadas em um Clinac Varian 6EX, com feixes de fótons de 6 MV e dois tamanhos de campo (5 x 5 cm2 e 10 x 10 cm2), irradiando-se filmes radiocrômicos Gafchromic EBT3 e câmara de ionização Scanditronix Wellhofer CC13. Planejamentos de 25 pacientes - 11 com técnica tridimendional (3D) e 14 com técnica de Radioterapia Estereotática Corpórea (SBRT) - foram realizados, inicialmente sem correção de heterogeneidade e, mantendo-se as UM, os cálculos com os diferentes algoritmos/métodos de correção foram comparados com o planejamento inicial. Foram avaliados as doses no volume alvo e nos órgãos em risco. RESULTADOS: As medidas realizadas em objetos simuladores revelaram que os algoritmos baseados no princípio da convolução (Eclipse® Pencil Beam Convolution com métodos de correção Batho, Batho Modificado e TAR equivalente; XiO® Clarkson e Convolution e iPlan® Pencil Beam) apresentaram diferenças de dose significativas na região da cortiça, sempre superestimando a medida, com uma sobredose superior a 8%. Algoritmos mais avançados, como o Eclipse® AAA e Acuros XB, XiO® Superposition e iPlan® XVMC, apresentaram desvios inferiores a 3% na região da heterogeneidade. A análise dos perfis mostra, igualmente, que a segunda classe de algoritmos apresenta melhor comportamento em meios de baixa densidade como a cortiça. A largura da penumbra apresentou desvios inferiores a 1 mm para os algoritmos mais avançados contra diferenças de até 4,5 mm entre os algoritmos baseados em convolução. A análise da distribuição de dose em planejamentos de tumores pulmonares mostrou que todos os cálculos com correção de heterogeneidade presentam doses superiores ao cálculo sem correção de heterogeneidade. O histograma dose-volume (DVH) do volume alvo sofreu um impacto maior do que dos órgãos em risco. Os cálculos realizados com algoritmos baseados em convolução apresentaram distribuições de dose semelhantes entre si, porém diferentes das do cálculo sem correção de heterogeneidade. Eclipse® AAA, Acuros XB, XiO® Superposition e iPlan® XVMC apresentaram distribuições de dose também semelhantes, porém Eclipse® Acuros XB e iPlan® XVMC são ainda mais similares. Os planejamentos de SBRT apresentaram resultados mais discrepantes do cálculo sem correção de heterogeneidade do que os planejamentos 3D. CONCLUSÕES: Os diferentes algoritmos de cálculo disponíveis possuem acurácias diferentes em meios de baixa densidade eletrônica. Essas diferenças possuem impacto nas distribuições de dose em planejamentos de tratamento de tumores pulmonares, sendo o impacto ainda maior para a técnica de SBRT. Entre os algoritmos avaliados, há pelo menos um de cada fabricante que apresentou bom desempenho em objetos simuladores de pulmão e que devem ser priorizados para o cálculo em planejamentos de tratamentos de câncer de pulmão / INTRODUCTION: In Radiotherapy, the dose distribution accuracy in heterogeneity correction calculations is directly related to the choice of calculation algorithm. There are many calculation algorithms commercially available. They vary in accuracy and processing time. This study aimed to quantify the accuracy of ten different calculation algorithms in lung equivalent material and to analyze the impact of the algorithm choice in the dose distribution in Radiotherapy applied to lung tumors. METHODS: It was used plates of water (solid water RW3) and lung (cork) equivalent materials to determine the Percentage of Depth Dose (PDD) and transversal profile inside the heterogeneity (cork). The measurements were performed in a Clinac Varian 6EX, with 6 MV photon beams and two field sizes (5 x 5 cm2 and 10 x 10 cm2), through irradiation of radiochromic films Gafchromic EBT3 and ionization chamber Scanditronix Wellhofer CC13. Treatment planning of 25 patients - 11 with tridimensional (3D) technique and 14 with Stereotactic Body Radiation Therapy (SBRT) technique - were performed, first without heterogeneity correction and, by keeping the Monitor Units (MU), the calculations were then performed with the different algorithms/methods of heterogeneity corrections and the results were compared with the initial planning. It was analyzed the target volume and organs at risk doses. RESULTS: The measurements performed in phantoms revealed that algorithms based on the convolution principle (Eclipse® Pencil Beam Convolution with correction methods Batho, Batho Modified and Equivalent TAR; XiO® Clarkson and Convolution e iPlan® Pencil Beam) presented significant dose differences in the cork region, overestimating the measurement, with a overdose higher than 8%. More advanced algorithms, as Eclipse® AAA and Acuros XB, XiO® Superposition and iPlan® XVMC, presented deviations below to 3% in the heterogeneity region. The profile analysis showed, similarly, that the second class of algorithms presents better performance in medium with low electronic density, like cork. The penumbra width presented deviations below to 1 mm for the more sophisticated algorithms against differences up to 4.5 mm between the convolution based algorithms. The dose distribution analysis in lung treatment planning showed that all the calculations performed with heterogeneity corrections presented doses higher than the calculation without heterogeneity corrections. The target volume dose-volume histogram (DVH) had a higher impact compared to the organs at risk. The calculation performed with convolution based algorithms presented dose distributions comparable, although different from the calculation performed without heterogeneity correction. Eclipse® AAA, Acuros XB, XiO® Superposition and iPlan® XVMC presented dose distribution similar, however Eclipse® Acuros XB and iPlan® XVMC are still more similar. The SBRT treatment planning presented higher deviations from the calculation with no heterogeneity correction, compared with the 3D treatment planning. CONCLUSIONS: The different calculation algorithms available have different accuracies in low density mediums. These differences have impact in the dose distributions in lung treatment planning, being the impact higher for the SBRT technique. Between the evaluated algorithms there is, at least one of each manufacturer, that presented acceptable performance in lung equivalent material and it should be the choice in lung treatment planning calculation

<p>Radioterapija (RT) je jedan od najvažnijih modaliteta lečenja solidnih malignih tumora i koristi je vi&scaron;e od 50% pacijenata (52,3%) sa malignim tumorima. Nauka koja proučava efekte elektromagnetnog zračenja na biolo&scaron;ke sisteme naziva se radiobiologija. Radiobiologija se fokusira na odgovor ćelija, tkiva i organizma kao celine na jonizujuće zračenje i proučava mehanizme radiobiolo&scaron;kog odgovora. Izlaganje ćelija niskim dozama JZ koje su nakon određenog vremenskog intervala praćene uobičajenim radioterapijskim dozama naziva se radioadaptivno zračenje. Adaptivni odgovor u sebi može da sadrži nekoliko fenomena: hiperradiosenzitaciju/radiorezistenciju, &ldquo;bystander&rdquo; efekat i radioadaptivni efekat u užem smislu. O molekularnim mehanizmima koji stoje iza navedenih efekata ne zna se dovoljno. U ovom radu ispitivan je odgovor malignih i zdravih ćelija na različite modalitete jonizujućeg zračenja u cilju boljeg poznavanja puteva ćelijske smrti i preživljavanja. Potpuno razumevanje molekularnih puteva koji vode u apoptozu ili u preživljavanje ćelija nakon izlaganja jonizujućem zračenju moglo bi koristiti u iznalaženju novih i efikasnijih strategija i modaliteta lečenja malignih tumora u cilju njihove potpune eredikacije. U istraživanju su kori&scaron;tene dve humane ćelijske linije ćelijska linija humanog kolorektalnog karcinoma HT-29 i ćelijska linija humanih fetalnih fibroblasta pluća MRC-5. Ćelije su zračene u dva režima različitim pre-iradijacionim dozama(0,03; 0,05 i 0,07Gy) i istom kurativnom dozom (2Gy) tokom 4 dana. Vi&scaron;ekratna primena niskih doza JZ nije značajno smanjila vijabilnost HT-29 ćelija, dok su dve radioadaptivne doze (0,05+2Gy i 0,07+2Gy), adekvatne doze JZ za radioterapijski postulat po&scaron;tede zdravih ćelija i bolji antitumorski efekat u odnosu na neradioadaptivno zračenje od 2Gy u toku 4 dana. Pokazana je mogućnost modulisanja ćelijskog odgovora na JZ uz pomoć niskih doza JZ koje su praćene dozom od 2Gy (radioadaptivni tip zračenja) u oba dizajnirana režima zračenja. Stepen o&scaron;tećenja hromozoma za većinu isporučenih doza pokazao dozno zavisni trend. Dozno-zavisno o&scaron;tećenje naslednog materijala izazvano radioadaptivnim zračenjem potvrđuje hipotezu da je stepen o&scaron;tećenja zdravih, MRC-5, ćelija manji nego u ćelijama kolorektalnog adenokarcinoma. Fragmentacija DNK je zabeležena za pojedine doze JZ u obe ćelijske linije, a uočena je i razlika u odgovoru zdrave i tumorske ćelijske linije. Detekcijom mutacija primarne sekvence fragmenta p53 gena pokazano je da se broj mutacija povećava sa povećanjem doze JZ. Oba režima radioadaptivnog zračenja, u obe ćelijske linije izazivaju vi&scaron;i nivo ekspresije p53. Ekspresija p38 MAPK proteina u HT-29 ćelijama bila je niža za sve isporučene doze JZ u odnosu na nezračene ćelije. U MRC-5 ćelijama, povi&scaron;ena ekspresija p38 MAPK utvrđena je samo u uzorcima koji su jednokratno primili samo niske doze JZ i dozu od 2Gy dnevno tokom 4 dana, u odnosu na nezračenu kontrolu. Razlike u ekspresiji ispitivanih proteina dobijene nakon primene dva režima radioadaptivnog zračenja posledica su delovanja niskih pre-iradijacionih doza JZ na modulisanje radiobiolo&scaron;kog odgovora obe ćelijske linije. Nivo ekspresije Bcl-2 i Bax proteina i njihov međusobni odnos, u obe ćelijske linije, su odraz različitog radiobiolo&scaron;kog odgovora ispitivanih ćelija koji zavisi od primenjenog režima zračenja.</p> / <p>Radiotherapy (RT) is one of the most important treatment modality for solid malignant tumors and it is applied in more than 50% of the patients (52.3%). Radiobiology id scientific discipline which studies the effects of electromagnetic irradiation on biological systems. Radiobiology focuses on the response of the cells, tissues and the organism as a whole to ionizing radiation and studying the mechanisms of radiobiological response. Exposure of cells to low-dose irradiation (priming dose) followed by challenging doses is called radioadaptive radiation. Adaptive response is described as several phenomena: hyperradiosensitivity / radiorezistence, &quot;bystander&quot; effect and radioadaptive effect in sensu strict. Molecular mechanisms underlying the above effects are not sufficiently known. In this study, the response of malignant and healthy cells on various modalities of ionizing radiation is explored in order to improve knowledge of pathways of cell death and survival. Fully understanding the molecular pathways leading to apoptosis or cell survival after exposure to ionizing radiation may be used in finding new and more effective strategies and modalities for the treatment of malignant tumors. The study used two human cell lines: human colorectal cancer HT-29 cell line and the human fetal lung fibroblast MRC-5. The cells were irradiated in two modalities using different pre-irradiation doses (0.03, 0.05 and 0,07Gy) and the same challenging dose (2Gy) for 4 days. Everyday use of low-dose did not significantly reduce the viability of HT-29 cells, while two radioadaptive doses (0.05 + 2Gy and 0.07+2Gy), are adequate doses for sparing healthy cells with better anti-tumor effects. The possibility of modulating the cellular response to the ionizing radiation was shown using low-doses followed by 2Gy (radioadaptive radiation) in both designed regimes of radiation. The level of chromosomal damage showed a dose-dependent trend. Dose-dependent damage to the genetic material caused by radiation confirms the hypothesis that the degree of damage to MRC-5 cells is smaller than the HT29 cells. DNA fragmentation differed between HT29 and MRC-5 cells. Detection of mutations in p53 gene fragment sequence increased with increasing doses. Both irradiation modalities, in both cell lines induce a higher level of p53 expression. Expression of p38 MAPK protein in the HT-29 cells was lower for all delivered doses compared to nonirradiated. In MRC-5 cells, increased expression of the p38 MAPK was found only in the samples that had only received on first day low-doses compared to the control nonirradiated cells. Differences in the expression of the tested proteins reflect different molecular mechanisms activated in normal and tumor cells. The level of Bcl.2 and Bax expression also reflected different radiobiological responses between normal and tumor cells, which depended on the applied irradiation regime.</p>

Graduation date: 1995

Thesis (M.S.)--Uniformed Services University of the Health Sciences, 2005. / Typescript (photocopy).