The thesis looks at various aspects of the modulation transfer function (MTF) and Wiener spectrum (WS) measurements for screen-film systems aiming at robust and simple methods for their routine measurement in a hospital setting. To measure the MTF of the film-screen systems, the square wave response function method was used. To normalise the MTF at a lower spatial frequency, a lead step and an object were incorporated into the measurement. Work on fitting the MTF data was carried out by considering two MTF models. To check if the current MTF calculation makes a low estimate, calculation using more terms in the Coltmann equation was performed. The value of the edge spread function method to measure the MTF was examined. The MTF of the microdensitometer was measured, and the correction factor for the screen-film. MTF based on this was calculated. MTF measurements of several screen-film combinations in use at the Aberdeen Royal Infirmary were made. The method used for the measurement of the WS of the screen-film was the fast Fourier transform digital method. A proper normalisation was chosen and implemented in the calculation. Low pass filtering, low frequency filtering, and windowing of the density fluctuation data were examined using sinusoidal and real noise data. The square shape of the scanning aperture of the microdensitomer was taken into account in the determination of WS. Slit length was synthesised and incorporated into the WS calculation. WS measurements of several screen-film combinations were made. A short receiver operating characteristic (ROC) study of two screen-film systems, recently introduced into Aberdeen Royal Infirmary, was undertaken to study the relationship between the physical measures of image quality that had been developed and the subjective measure based on the area under the ROC curve.

No description available.

No description available.

This dissertation presents a contrast-enhancement algorithm called Artifact-Suppressed Adaptive Histogram Equalization (ASAHE). This algorithm was developed as part of a larger effort to replace the film radiographs currently used in radiology departments with digital images. Among the expected benefits of digital radiology are improved image management and greater diagnostic accuracy. Film radiographs record X-ray transmission data at high spatial resolution, and a wide dynamic range of signal. Current digital radiography systems record an image at reduced spatial resolution and with coarse sampling of the available dynamic range. These reductions have a negative impact on diagnostic accuracy. The contrast-enhancement algorithm presented in this dissertation is designed to boost diagnostic accuracy of radiologists using digital images. The ASAHE algorithm is an extension of an earlier technique called Adaptive Histogram Equalization (AHE). The AHE algorithm is unsuitable for chest radiographs because it over-enhances noise, and introduces boundary artifacts. The modifications incorporated in ASAHE suppress the artifacts and allow processing of chest radiographs. This dissertation describes the psychophysical methods used to evaluate the effects of processing algorithms on human observer performance. An experiment conducted with anthropomorphic phantoms and simulated nodules showed the ASAHE algorithm to be superior for human detection of nodules when compared to a computed radiography system's algorithm that is in current use. An experiment conducted using clinical images demonstrating pneumothoraces (partial lung collapse) indicated no difference in human observer accuracy when ASAHE images were compared to computed radiography images, but greater ease of diagnosis when ASAHE images were used. These results provide evidence to suggest that Artifact-Suppressed Adaptive Histogram Equalization can be effective in increasing diagnostic accuracy and efficiency.

No description available.

[Truncated abstract] In this thesis, we introduce a mammogram analysis system developed for the automatic segmentation and analysis of mammograms. This original system has been designed to aid radiologists to detect breast cancer on mammograms. The system embodies attribute-driven segmentation in which the attributes of an image are extracted progressively in a step-by-step, hierarchical fashion. Global, low-level attributes obtained in the early stages are used to derive local, high-level attributes in later stages, leading to increasing refinement and accuracy in image segmentation and analysis. The proposed system can be characterized as: • a bootstrap engine driven by the attributes of the images; • a solid framework supporting the process of hierarchical segmentation; • a universal platform for the development and integration of segmentation and analysis techniques; and • an extensible database in which knowledge about the image is accumulated. Central to this system are three major components: 1. a series of applications for attribute acquisition; 2. a standard format for attribute normalization; and 3. a database for attribute storage and data exchange between applications. The first step of the automatic process is to segment the mammogram hierarchically into several distinctive regions that represent the anatomy of the breast. The adequacy and quality of the mammogram are then assessed using the anatomical features obtained from segmentation. Further image analysis, such as breast density classification and lesion detection, may then be carried out inside the breast region. Several domain-specific algorithms have therefore been developed for the attribute acquisition component in the system. These include: 1. automatic pectoral muscle segmentation; 2. adequacy assessment of positioning and exposure; and 3. contrast enhancement of mass lesions. An adaptive algorithm is described for automatic segmentation of the pectoral muscle on mammograms of mediolateral oblique (MLO) views

Das Ziel dieser Untersuchung ist es, Aspekte der Strukturqualität (technische Untersuchungs- und Bildqualität), Prozessqualität (Angemessenheit der Indikation) und der Ergebnisqualität (Richtigkeit der Befunderhebungen) von Röntgenaufnahmen aus der tierärztlichen Praxis zu erörtern und häufige Fehlerquellen festzustellen. Dazu werden alle Röntgenaufnahmen von Kleintieren, die im Zeitraum von Anfang Dezember 2003 bis Ende Dezember 2004 als Original in die Klinik für Kleintiere der Universität Leipzig gelangen auf praxisrelevante Merkmale der Struktur-, Prozess- und Ergebnisqualität hin untersucht. Die Ermittlung der Daten erfolgt auf subjektiver Grundlage anhand eines Befundbogens durch Konsensbeurteilung von zwei Unter-suchern. Zur Auswertung gelangen 1259 Röntgenaufnahmen aus 600 verschiedenen Untersuchungen. Diese Aufnahmen stammen zu 86,9 % aus den Bundesländern Sachsen, Sachsen-Anhalt und Thüringen von 216 verschiedenen Tierarztpraxen. 80,3 % der untersuchten Tiere sind Hunde, 18,9 % Katzen. In der Gesamtbeurteilung der Bildqualität erweisen sich 48,7 % der Aufnahmen ohne Bean-standung. 29,2 % zeigen geringfügige Mängel, 16,0 % sind bedingt diagnostisch geeignet und 6,1 % sind unzureichend. 22,1 % der ausgewerteten Aufnahmen sind somit mangelhaft. Sie weisen Defizite in der diagnostischen Eignung auf oder sind hierfür ungeeignet. Die wichtigsten Fehlerquellen der Strukturqualität sind Mängel der Lagerung und Projektion, des Bildkontrastes und der Bildschärfe. Abweichungen der Lagerung und Projektion, meist durch nicht winkelgerechte Lagerung des Patienten im Direktstrahl verursacht, sind mit 11,4 % aller Aufnahmen im Vergleich zu anderen Fehlerquellen relativ selten. Die Auswirkungen auf die diagnostische Eignung sind jedoch oft schwerwiegend: 69,9 % der von Mängeln in der Lagerung betroffenen Aufnahmen zeigen Einschränkungen hinsichtlich der diagnostischen Eignung. 33,3 % aller Aufnahmen weisen Abweichungen des Bildkontrastes auf. Die häufigste Ursache dafür ist der Umgang mit verbrauchter Entwicklerlösung, gefolgt von Unter- und Überbelichtung. Betrachtet man die Gesamtheit der Kontrastabweichungen kann festgestellt werden, dass 47,7 % auf Fehler in der Filmentwicklung zurückzuführen sind. Auswirkungen auf die Eignung zur Diagnosestellung sind weniger gravierend als bei Mängeln der Lagerung und Projektion: 35,1 % der von Kontrastabweichungen betroffenen Aufnahmen zeigen Einschränkungen des diagnosti-schen Nutzens. 23,0 % der Aufnahmen sind durch Abweichungen der Bildschärfe gekennzeichnet. Am häufigs-ten ist Bewegungsunschärfe (67,7 % der betroffenen Aufnahmen) zu ermitteln. Weiterhin wer-den oft Materialunschärfe und Unschärfe durch Streustrahlung beobachtet, die auf den falschen Umgang mit dem Streustrahlenraster und der Film-Folien-Kombination zurückzuführen sind. Die Auswirkungen auf die diagnostische Eignung zeigen, dass 29,6 % der Röntgenaufnahmen mit Abweichungen der Bildschärfe Einschränkungen des diagnostischen Nutzens nach sich ziehen. Artefakte, vor allem verursacht durch Kratzer, Risse oder Brüche in Film oder Folie sowie durch Verunreinigungen durch Entwickler-, Fixierlösung oder Wasser, sind bei 20,7 % aller Röntgen-aufnahmen zu finden. Einschränkungen der diagnostischen Eignung ergeben sich dadurch bei 1,2 % der analysierten Aufnahmen. Zur Untersuchung der Prozessqualität wird die Angemessenheit der Indikation ermittelt, die nach RöV § 2a für jede Röntgenaufnahme gegeben sein muss (ANON. 2003a). Eine absolute Indikation kann bei 94,7 % der ausgewerteten Aufnahmen festgestellt werden. Bei knapp der Hälfte aller Aufnahmen dieser Arbeit kann die Ergebnisqualität erörtert werden. Die gestellte radiologische Verdachtsdiagnose ist bei 85,5 % dieser Fälle medizinisch nachvoll-ziehbar. Aus den Ergebnissen dieser Arbeit lässt sich ableiten, dass ein wesentlicher Teil der vorkom-menden Mängel der Bildqualität auf ungenügende Sorgfalt bei der Anfertigung und Verarbeitung der Röntgenaufnahme zurückzuführen ist. Allerdings liegen auch Defizite bei der Interpretation der gewonnenen Information durch die Röntgenuntersuchung vor. Da jeder Anwender ionisierender Strahlen verpflichtet ist, jede unnötige Strahlenexposition von Mensch und Umwelt zu vermeiden, müssen bestehende Defizite in Bezug auf die Anwendung der Projektionsradio-grafie abgebaut werden und die Vermittlung von Wissen und praktischen Fertigkeiten auf diesem Gebiet während der tierärztlichen Ausbildung verbessert werden. Ebenso sollte eine Feh-lerbeseitigung durch Ausnutzung oder Verbesserung der technischen Möglichkeiten erfolgen. Eine erneute Untersuchung zur Qualität von Röntgenaufnahmen in der tierärztlichen Praxis auf der Grundlage dieser Studie erscheint zur Überprüfung der getroffenen Maßnahmen zur Ver-besserung der Bildqualität sinnvoll.:ABKÜRZUNGSVERZEICHNIS IV 1 EINLEITUNG 1 2 LITERATURÜBERSICHT 4 2.1 Strahlenschutz 4 2.1.1 Strahlenbiologische Grundlagen 4 2.1.2 Rechtliche Grundlagen 5 2.1.2.1 Anwendung von Röntgenstrahlen 5 2.1.2.2 Indikationsstellung 6 2.1.3 Technischer und praktischer Strahlenschutz 6 2.2 Bildqualität 8 2.2.1 Ermittlung der Kenngrößen eines Röntgenbildes 8 2.2.1.1 Optische Dichte 9 2.2.1.1.1 Definition der optischen Dichte 9 2.2.1.1.2 Ermittlung der optischen Dichte 10 2.2.1.2 Unschärfe 10 2.2.1.2.1 Definition der Unschärfe 10 2.2.1.2.2 Ermittlung der Unschärfe 12 2.2.1.3 Kontrast 12 2.2.1.3.1 Definition des Kontrastes 12 2.2.1.3.2 Ermittlung des Kontrastes 15 2.2.1.4 Bildrauschen 15 2.2.1.4.1 Definition des Bildrauschens 15 2.2.1.4.2 Ermittlung des Bildrauschens 16 2.2.2 Einflussfaktoren auf die Bildqualität 17 2.2.2.1 Allgemeine Fehlerquellen 17 2.2.2.2 Einfluss von Spannung und Stromstärke 17 2.2.2.3 Einfluss der Streustrahlung 18 2.2.2.4 Rastereinsatz 20 2.2.2.5 Einfluss des Objektes 21 2.2.2.6 Einfluss der Geometrie 22 2.2.2.7 Einfluss von Film und Folie 22 2.2.2.7.1 Röntgenfilm 23 2.2.2.7.2 Verstärkerfolie 24 2.2.2.8 Einfluss der Filmverarbeitung 25 2.2.2.9 Dunkelkammerarbeit 26 2.2.2.10 Artefakte 26 3 TIERE, MATERIAL UND METHODEN 28 3.1 Tiere und Material 28 3.2 Methoden 28 3.2.1 Datenerfassung und Archivierung 28 3.2.2 Befundbogen 28 3.2.2.1 Epidemiologische Daten 29 3.2.2.2 Strukturqualität 29 3.2.2.2.1 Technische Untersuchungsqualität 29 3.2.2.2.2 Technische Bildqualität 30 3.2.2.3 Prozessqualität 31 3.2.2.4 Ergebnisqualität 31 3.2.2.5 Zusammenfassende Beurteilung der Bildqualität 37 3.2.3 Datenauswertung 38 4 ERGEBNISSE 39 4.1 Epidemiologische Daten 39 4.2 Strukturqualität 42 4.2.1 Häufigkeitsanalyse 42 4.2.1.1 Zusammenfassende Beurteilung der Bildqualität 42 4.2.1.2 Technische Untersuchungsqualität 44 4.2.1.2.1 Vollständigkeit der Untersuchung 44 4.2.1.2.2 Art der Entwicklung 44 4.2.1.2.3 Streustrahlenrastereinsatz 45 4.2.1.2.4 Praktischer Strahlenschutz 46 4.2.1.2.5 Vollständige Abbildung der Region 46 4.2.1.2.6 Identifikation der Aufnahme 46 4.2.1.2.7 Kontrastmitteleinsatz 47 4.2.1.3 Technische Bildqualität 48 4.2.1.3.1 Artefakte 48 4.2.1.3.2 Lagerung und Projektion 49 4.2.1.3.3 Bildkontrast 52 4.2.1.3.4 Bildschärfe 54 4.2.2 Fehleranalyse 57 4.2.2.1 Artefakte vs. Art der Entwicklung 57 4.2.2.2 Lagerung und Projektion vs. Projektionsebene 57 4.2.2.3 Lagerung und Projektion vs. Körperregion und Projektionsebene 58 4.2.2.4 Bildschärfe vs. Körperregion und Projektionsebene 59 4.2.2.5 Bildschärfe vs. Rastereinsatz 60 4.2.2.6 Bildkontrast vs. Projektionsebene 62 4.2.2.7 Bildkontrast vs. Rastereinsatz 62 4.2.2.8 Bildkontrast vs. Art der Entwicklung 63 4.3 Strukturqualität – Konstanzanalyse der Tierarztpraxen 63 4.4 Prozessqualität 67 4.5 Ergebnisqualität 67 5 DISKUSSION 69 5.1 Methode der Beurteilung der Bildqualität 69 5.2 Zusammenfassende Beurteilung der Bildqualität 69 5.3 Vollständigkeit der Untersuchung 70 5.4 Art der Entwicklung 71 5.5 Rastereinsatz 72 5.6 Praktischer Strahlenschutz 73 5.7 Artefakte 75 5.8 Lagerung und Projektion 77 5.9 Bildschärfe 78 5.10 Bildkontrast 80 5.11 Kontrastmitteleinsatz 83 5.12 Konstanz innerhalb der Tierarztpraxen 84 5.13 Prozessqualität 85 5.14 Ergebnisqualität 86 5.15 Zusammenfassung der Diskussion und Schlussfolgerung 87 6 ZUSAMMENFASSUNG 90 7 SUMMARY 92 8 LITERATURVERZEICHNIS 94 / The aim of this study is to evaluate aspects of structural quality (technical examination and im-age quality), quality of the process (adequacy of indication) and the outcome (correctness of findings) of radiographs from the veterinary practice and to indentify frequent radiographic er-rors. For this purpose all radiographs of small animals that are received at the Department of Small Animal Medicine of the University of Leipzig between December 1st 2003 and December 31th 2004 as an original are examined for relevant features of structural quality, process quality and outcome. The data collection is done subjectively based on the consensus examination of the radiographs by two independent examiners. The evaluation includes 1259 radiographs from 600 different examinations. 86.9 % of these images come from the federal states of Germany Saxony, Saxony-Anhalt and Thuringia from 216 different veterinary practices. 80.3 % of the examined animals are dogs, 18.9 % are cats. Concerning the over-all evaluation of the image quality, 48.7 % of the radiographs are without restrictions. Minor faults are detected in 29.2 % of the radiographs, 16.0 % are diagnostically compromised and 6.1 % are insufficient. Thus, 22.1 % of the examined radiographs are unsatis-factory. They show either deficits in their diagnostic suitability or are completely useless. The most important sources of errors are faults in positioning of the patient and the following projec-tion, of image contrast and sharpness. Deviations in positioning and projection, mostly caused by a suboptimal angle in the position of the patient in the x-ray, are with 11.4 % of all radiographs in comparison to other errors relatively rare. However the effect on the diagnostic use is severe: 69.9 % of the images with positioning faults show deficits with regard to the diagnostic suitability. Regarding the contrast of the image, 33.3 % of all radiographs display deficits. The most com-mon cause is the use of exhausted developer, followed by under- and overexposure. Consider-ing the overall deviations of image contrast, 47.7 % are attributed to errors during the x-ray film development. Consequences for the diagnostic use are less serious compared to errors in posi-tioning and projection: 35.1 % of the images with contrast deviations are of limited diagnostic use. 23.0 % of the radiographs are characterized by deviations in the sharpness: motion haziness occurs most frequently (in 67.7 %) of the images concerned. Receptor unsharpness and scat-tered radiation are often observed, caused by improper use of radiographic grids and film-screen combinations. The effects on the diagnostic suitability show that 29.6 % of the radiographs with deviations in the sharpness are of limited diagnostic use. Artifacts, most frequently caused by scratches, tears and breaks of the film or the intensifying screen as well as by splashes of the developing resp. fixation reagent or water, are found on 20.7 % of all radiographs. As a result of artifacts 1.2 % of the radiographs examined show defi-cits in their diagnostic suitability. To evaluate the quality of the process the adequacy of indication is determined, which is required for every radiographic examination according to RöV § 2a (ANON. 2003a). An absolute indication can be found in 94.7 % of all images. The quality of the outcome can be discussed in almost halve of all radiographs. The referral diagnosis is medically plausible in 85.5 % of these cases. The results of this study reveal that a considerable portion of the occurring errors in the image quality are caused by a lack of care during taking and processing of the radiographic images. Deficits in the interpretation of the gained information from the radiographic examination occur as well. Since avoidance of unnecessary exposure of humans and the environment to radiation is a major obligation of every user of ionizing radiation, existing deficits regarding the use of projection radiography should be reduced and the transfer of knowledge and practical capabili-ties in this area during the veterinary training should be improved. Furthermore, the elimination of errors by use or improvement of the technical possibilities is important. A new evaluation of the quality of radiographic images from the veterinary practice on the basis of this study seems useful to examine the effects of the steps taken to improve the image quality.:ABKÜRZUNGSVERZEICHNIS IV 1 EINLEITUNG 1 2 LITERATURÜBERSICHT 4 2.1 Strahlenschutz 4 2.1.1 Strahlenbiologische Grundlagen 4 2.1.2 Rechtliche Grundlagen 5 2.1.2.1 Anwendung von Röntgenstrahlen 5 2.1.2.2 Indikationsstellung 6 2.1.3 Technischer und praktischer Strahlenschutz 6 2.2 Bildqualität 8 2.2.1 Ermittlung der Kenngrößen eines Röntgenbildes 8 2.2.1.1 Optische Dichte 9 2.2.1.1.1 Definition der optischen Dichte 9 2.2.1.1.2 Ermittlung der optischen Dichte 10 2.2.1.2 Unschärfe 10 2.2.1.2.1 Definition der Unschärfe 10 2.2.1.2.2 Ermittlung der Unschärfe 12 2.2.1.3 Kontrast 12 2.2.1.3.1 Definition des Kontrastes 12 2.2.1.3.2 Ermittlung des Kontrastes 15 2.2.1.4 Bildrauschen 15 2.2.1.4.1 Definition des Bildrauschens 15 2.2.1.4.2 Ermittlung des Bildrauschens 16 2.2.2 Einflussfaktoren auf die Bildqualität 17 2.2.2.1 Allgemeine Fehlerquellen 17 2.2.2.2 Einfluss von Spannung und Stromstärke 17 2.2.2.3 Einfluss der Streustrahlung 18 2.2.2.4 Rastereinsatz 20 2.2.2.5 Einfluss des Objektes 21 2.2.2.6 Einfluss der Geometrie 22 2.2.2.7 Einfluss von Film und Folie 22 2.2.2.7.1 Röntgenfilm 23 2.2.2.7.2 Verstärkerfolie 24 2.2.2.8 Einfluss der Filmverarbeitung 25 2.2.2.9 Dunkelkammerarbeit 26 2.2.2.10 Artefakte 26 3 TIERE, MATERIAL UND METHODEN 28 3.1 Tiere und Material 28 3.2 Methoden 28 3.2.1 Datenerfassung und Archivierung 28 3.2.2 Befundbogen 28 3.2.2.1 Epidemiologische Daten 29 3.2.2.2 Strukturqualität 29 3.2.2.2.1 Technische Untersuchungsqualität 29 3.2.2.2.2 Technische Bildqualität 30 3.2.2.3 Prozessqualität 31 3.2.2.4 Ergebnisqualität 31 3.2.2.5 Zusammenfassende Beurteilung der Bildqualität 37 3.2.3 Datenauswertung 38 4 ERGEBNISSE 39 4.1 Epidemiologische Daten 39 4.2 Strukturqualität 42 4.2.1 Häufigkeitsanalyse 42 4.2.1.1 Zusammenfassende Beurteilung der Bildqualität 42 4.2.1.2 Technische Untersuchungsqualität 44 4.2.1.2.1 Vollständigkeit der Untersuchung 44 4.2.1.2.2 Art der Entwicklung 44 4.2.1.2.3 Streustrahlenrastereinsatz 45 4.2.1.2.4 Praktischer Strahlenschutz 46 4.2.1.2.5 Vollständige Abbildung der Region 46 4.2.1.2.6 Identifikation der Aufnahme 46 4.2.1.2.7 Kontrastmitteleinsatz 47 4.2.1.3 Technische Bildqualität 48 4.2.1.3.1 Artefakte 48 4.2.1.3.2 Lagerung und Projektion 49 4.2.1.3.3 Bildkontrast 52 4.2.1.3.4 Bildschärfe 54 4.2.2 Fehleranalyse 57 4.2.2.1 Artefakte vs. Art der Entwicklung 57 4.2.2.2 Lagerung und Projektion vs. Projektionsebene 57 4.2.2.3 Lagerung und Projektion vs. Körperregion und Projektionsebene 58 4.2.2.4 Bildschärfe vs. Körperregion und Projektionsebene 59 4.2.2.5 Bildschärfe vs. Rastereinsatz 60 4.2.2.6 Bildkontrast vs. Projektionsebene 62 4.2.2.7 Bildkontrast vs. Rastereinsatz 62 4.2.2.8 Bildkontrast vs. Art der Entwicklung 63 4.3 Strukturqualität – Konstanzanalyse der Tierarztpraxen 63 4.4 Prozessqualität 67 4.5 Ergebnisqualität 67 5 DISKUSSION 69 5.1 Methode der Beurteilung der Bildqualität 69 5.2 Zusammenfassende Beurteilung der Bildqualität 69 5.3 Vollständigkeit der Untersuchung 70 5.4 Art der Entwicklung 71 5.5 Rastereinsatz 72 5.6 Praktischer Strahlenschutz 73 5.7 Artefakte 75 5.8 Lagerung und Projektion 77 5.9 Bildschärfe 78 5.10 Bildkontrast 80 5.11 Kontrastmitteleinsatz 83 5.12 Konstanz innerhalb der Tierarztpraxen 84 5.13 Prozessqualität 85 5.14 Ergebnisqualität 86 5.15 Zusammenfassung der Diskussion und Schlussfolgerung 87 6 ZUSAMMENFASSUNG 90 7 SUMMARY 92 8 LITERATURVERZEICHNIS 94

Os exames radiológicos são importantes recursos no auxílio da elaboração um diagnóstico odontológico preciso. Contudo, só devem ser realizados quando houver uma real indicação clínica, visto que os efeitos das radiações ionizantes no organismo humano são cumulativos. Falhas na execução de procedimentos radiológicos resultam em imagens com qualidade diagnóstica duvidosa, sendo necessária, muitas vezes, a repetição de exames. Desta forma, métodos para minimizar a rejeição imagens radiológicas devem ser observados. A fim de colaborar para a diminuição dos erros de posicionamentos e consequente rejeição de exames de imagem na área da odontologia, este estudo teve por objetivo a criação de um guia de referência para aplicação em exames extraorais odontológicos. Para a elaboração e estruturação deste guia, foi realizado um estudo com o intuito de identificar os motivos de rejeição de radiografias panorâmicas em um serviço de radiologia odontológica digital. O estudo foi retrospectivo e por meio de uma busca no software de aquisição de imagens, foram selecionadas 2306 radiografias panorâmicas digitais, correspondentes a 10% do total de exames realizados entre os anos de 2013 a 2015. A partir da amostra, foram identificados os exames rejeitados e as causas da rejeição. Ainda para colaborar com o desenvolvimento do guia de referência, foi aplicado um questionário aos profissionais técnicos/tecnólogos atuantes no setor de radiologia onde a pesquisa foi realizada. O questionário contou com nove perguntas relacionadas à rotina de trabalho do setor. Com os resultados obtidos na pesquisa foi possível a elaboração do guia de referência com imagens radiográficas para aplicação em exames odontológicos. / The radiological exams are important resources in aid of drafting a dental diagnosis. However, should only be performed when there is a real clinical indication, since the effects of ionizing radiation on the human body are cumulative. Flaws in the implementation of radiological procedures result in doubtful quality diagnostic images, being necessary, many times, the repetition of exams. In this way, methods to minimize radiological images rejection must be observed. In order to contribute to the reduction of errors of positioning and consequent rejection of imaging examinations in the area of dentistry, this study had as its objective the creation of a reference guide for application in dental extraoral examinations. For the preparation and structuring of this guide, a study was conducted with the aim of identifying the reasons for the rejection of panoramic radiographs in a digital dental radiology service. The study was retrospective and by means of a search in the software of image acquisition, were selected 2306 digital panoramic radiographs, corresponding to 10% of the total number of examinations performed between the years of 2013 and 2015. From the sample, were identified the rejected exams and the causes of rejection. To collaborate with the development of the reference guide, a questionnaire was applied at technical professionals working in the radiology sector where the research was conducted. The questionnaire was attended by nine questions related to routine work in the sector. With the results obtained in the study it was possible to do the preparation of the guide of reference with radiographic images for application in dental examinations.

CAPES / A dosimetria em tomografia computadorizada (TC) envolve desde a determinação de grandezas dosimétricas específicas de TC até a estimativa de dose absorvida e dose efetiva. Entretanto, deve-se considerar que por envolver radiação ionizante no seu processo, este procedimento apresenta riscos inerentes e sua utilização deve ponderar o custo e o benefício propiciado pelo procedimento. A proteção de pacientes submetidos a exames radiológicos, de uma maneira geral, é determinada pelos princípios da “justificação” e “otimização”. Desta forma, torna-se importante o conhecimento dos níveis de radiação nas exposições durante um procedimento tomográfico. Estes níveis foram observados através da estimativa das grandezas específicas para tomografia computadorizada, tais como o Índice de kerma no ar (C100,ar), o Índice de kerma ponderada (Cw) e o produto kerma comprimento (PKL,CT), e em estimados os níveis de dose efetiva e risco para o estudo tomográfico computadorizado de crânio, tórax e abdômen realizado com múltipla varredura. Os valores obtidos foram comparados com os obtidos por simulação computacional por Monte Carlo. Eles foram utilizados, neste estudo, no cálculo da Dose Efetiva e risco e para comparação com o nível de referência de dose estabelecido pela Comunidade Européia. Utilizando-se o programa de simulação computacional Dosecal X_CT e o protocolo ICRP 103, foram determinadas as grandezas de radioproteção relevantes para o estudo que são os valores de dose efetiva referente ao procedimento. O nível do Produto kerma comprimento (PKL,CT), utilizando-se o C100,ar previamente estabelecido, foi também obtido e comparado com o nível de referência de dose estabelecido pela comunidade europeia. Os valores encontrados até agora estão dentro dos limites dos Níveis de Referência. / The computed tomography (CT) dosimetry involves measurements of specific quantities of CT, which are part of CT quality control procedures, as well as calculation of absorbed and effective doses to a patient submitted to CT examinations. Since CT uses ionizing radiation, it should be considered that a precise balance between risks and benefits must be achieved in order to justify the adoption of such technique. Radiation protection of patients undergoing radiological exams is established based on the justification and optimization principles. Nowadays, it is important to know the dose radiation levels to which a patient is exposed during a tomographic procedure. Those are given by the estimation of specific dosimetric quantities called the computed tomography kerma index in air, C100,air, the weighted computed tomography kerma index Cw, kerma length product, PKL,CT and then the levels of effective dose and risk to the computerized CT scan study of skull, thorax and abdomen with a multiple scanning. The values obtained were compared with those obtained by computer simulation using Monte Carlo method. The protection quantities organ absorbed dose, effective dose and risk for comparison with the reference dose level established by the European Community. Using computational simulation program of the Dosecal X_CT and the ICRP 103 Protocol, were certain quantities of radiation protection relevant to study which are the values of effective dose for the procedure. The dose length product PKL,CT level was calculated from the C100,air and compared to the reference dose level established by the European Community. The values found so far are within the limits of the reference levels.

A busca pela qualidade radiográfica com a menor dose de radiação absorvida é uma constante na comunidade radiológica. Juntamente com o princípio ALARA (As Low As Reasonably Achievable), os filtros de alumínio são peças fundamentais para barrar os fótons de baixa energia que não contribuem para a imagem e depositam dose de radiação para o paciente. De acordo com a Portaria n°453, a Agência Nacional de Vigilância Sanitária decretou que todos os equipamentos de raios X odontológicos intrabucais devem possuir a filtração adicional. Nesse sentido, os filtros são peças fundamentais para a proteção radiológica do paciente. Este estudo tem por objetivo caracterizar a composição elementar dos filtros de raios X de equipamentos de raios X odontológicos intrabucais. O estudo também relaciona a composição elementar com a qualidade das imagens radiográficas. A análise dos filtros foi realizada por meio do método de Espectroscopia de Fluorescência de raios X por Energia Dispersiva (EDXRF). Foram analisados, qualitativa e quantitativamente, dez filtros de alumínio. Para avaliar a qualidade das imagens, foram realizadas 30 radiografias periapicais dos dentes molares com 0,3 s de tempo de exposição (dez radiografias) e incisivos com 0,2 s e 0,3 s (vinte radiografias) com os diferentes filtros em um equipamento com os parâmetros de 66 kV e 6,5 mA. Os filtros e as radiografias foram identificadas, para que fosse possível distinguir a que filtro cada radiografia pertencia no momento das avaliações. Todas as radiografias foram feitas sob as mesmas condições. As radiografias foram submetidas à análise das densidades óticas por um densitômetro e posteriormente, enviadas a cirurgiões dentistas radiologistas que fizeram a análise subjetiva. Foram selecionadas três regiões para análise do densitômetro (diferenciadas entre dentes molares e incisivos) e uma região para análise subjetiva (diferentes regiões para dentes molares e incisivos). Os dados obtidos foram correlacionados com a avaliação dos efeitos da composição elementar dos filtros na qualidade das imagens radiográficas. Os elementos encontrados na análise dos filtros foram: Al, S, Cl, Ti, Mn, Fe, Cu, Zn e Zr. Os filtros apresentaram maiores concentrações de alumínio, com mais de 96% sendo os outros elementos contaminantes ou elementos que foram adicionados para melhorar a estabilidade mecânica do filtro. As densidades óticas das radiografias seguiram um padrão nas regiões analisadas, exceto as regiões enegrecidas do filme. A análise subjetiva revelou que muitas das radiografias realizadas poderiam ser aceitas para diagnóstico. Porém, imagens consideradas com baixo contraste obtiveram o mesmo valor de densidade ótica. Os resultados mostraram que a composição elementar dos filtros não modificou a qualidade da imagem. Por conseguinte, os filtros convencionais pesquisados oferecem uma opção aceitável para a produção de imagens de qualidade em radiologia odontológica, apesar das diferenças na composição das ligas. / The quest for radiographic quality with the lowest dose of radiation absorbed is a constant in the radiology community. Along with the ALARA principle (As Low As Reasonably Achievable), the aluminum filters are essential parts to bar the low energy photons do not contribute to the image and cause radiation dose to the patient. According to standard Portaria No. 453, the Agência Nacional de Vigilância Sanitária decreed that all equipment intraoral dental X-rays must have an additional filtration. Acording this, the filters are essential parts to radiological protection of patients. This study aims to characterize the elemental composition of filters used in intraoral X-ray equipment. We also intend to relate them to the quality of the radiographic images. The analysis of the filters was made using the method Energy Dispersive X-ray Fluorescence (EDXRF). Ten aluminum filters were analyzed (qualitatively and quantitatively). To evaluate the quality of images, 30 periapical radiographs of molars to 0.3 s (ten radiographs) and the incisor teeth 0.2 and 0.3 s (twenty radiographs) were performed with different filters. All filters and all radiographs were identified, it was possible to distinguish which folder each radiograph belonged at the time of the evaluations. All radiographs were performed under the same conditions. Radiographs were subjected to analysis of optical density by a densitometer and later, two dentists radiologists realized a subjective analysis. Three regions for analysis of the densitometer (differentiated between molars and incisors) and a region for subjective analysis (for different regions molars and incisors) were selected. The data were correlated with the assessment of the effects of the elemental composition of all filters in the quality of radiographic images. From the results, the elements of the filters in the analysis were: Al, S, Cl, Ti, Mn, Fe, Cu, Zn and Zr. The filters had higher aluminum concentrations (over 96%), other elements were contaminants or components that are added to improve the mechanical stability of the filter. The optical densities of radiographs followed a pattern for the regions analyzed except blackened regions of the film. Subjective analysis revealed that many of the radiographs were accepted for diagnosis. But considered low-contrast images obtained the same value of optical density. Therefore, it is concluded that the elemental composition of filters do not change the image quality. Consequently, conventional filters were evaluated option to produce an acceptable image quality in dental radiology, despite differences in the composition of the alloys.