A qualidade dos exames mamográficos é uma preocupação constante do sistema de saúde mundial que se vê diante do desafio da detecção precoce do câncer de mama. As organizações responsáveis implementaram protocolos internacionais que consistem em testes de aceitação dos equipamentos mamográficos e de tomossíntese da mama, os quais estabelecem um padrão de qualidade nos serviços radiográficos. Porém, essas diretrizes têm como base o uso de objetos simuladores de mamas com espessuras e composições padrões, que muitas vezes não condizem com os perfis populacionais dos centros de diagnóstico. Neste trabalho, foi desenvolvido um sistema automatizado de rastreamento e gerenciamento de dados, que extrai as informações referentes ao processo de aquisição da mamografia digital e armazena-as em um servidor DICOM SCP (Service Class Provider). Após armazenadas, o sistema correlaciona os fatores de exposição das imagens, de forma a avaliar os níveis de referência em dose de radiação fornecidos pelos equipamentos. Como resultados, foi verificado que o perfil mamário dos centros institucionais de diagnóstico estudados não segue os valores de referência apresentados na literatura em termos de espessura e densidade mamária. Enquanto a mama padrão dos testes de garantia de qualidade é composta por 50 mm de espessura e 50% de densidade (50-50), a população estudada apresentou mamas comprimidas com média de 60 mm de espessura, com baixo percentual de tecido fibroglandular (menor que 25%). Portanto, o uso o sistema desenvolvido pode direcionar os testes de conformidade dos equipamentos para perfis mamários específicos. Esse direcionamento pode auxiliar na determinação de doses ótimas de radiação para melhoria da qualidade da imagem, produzindo valores de referência de grande utilidade para a qualidade dos serviços radiográficos. / Image quality assessment in mammography represents one of the greatest challenges that health services face in order to detect breast cancer early. The world health organization recommends quality assurance guidelines, which consist of acceptance tests for digital mammography (DM) and digital breast tomosynthesis (DBT), to standardize the radiological services. However, these guidelines are based on test objects widely used to simulate standard breasts in terms of composition and thickness, which often do not match with the demographic profiles in the breast care centers. In this thesis work, an automated system for tracking and data management was developed to extract the metadata (DICOM header) from the image acquisition process and to store it into a custom DICOM Service Class Provider (SPC). The developed system correlates the exposure factors\' info in order to evaluate the references for patient radiation dose provided by the manufacturers. As result of the data correlations, the reference required by the international guidelines for standard breasts are not a feasible representation for the demographic profile in the breast care center evaluated in terms of breast density and thickness. While the standard for quality assurance testing consists of breasts with 50 mm of thickness and 50% of density, the demographic population presented compressed breast thickness of approximately 60 mm and low fibroglandular tissue (less than 25%). Therefore, using the developed system should guide the quality assurance in digital mammography to specific breast profiles. This guidance may assist in determining optimal radiation doses to improve the image quality, producing useful benchmarks for the quality of radiological services.

Os requisitos técnicos da qualidade da imagem em mamografia estabelecidos por normas nacionais e internacionais incluem parâmetros de qualidade que podem ser avaliados através da realização de testes periódicos. Estes parâmetros podem ser medidos com a aquisição e leitura de imagens de objetos (phantoms) que simulam as estruturas presentes em uma mamografia. O phantom CDMAM foi confeccionado especificamente para a realização de testes que utilizam um procedimento padrão para se determinar um limiar de contraste para cada diâmetro de disco presentes em suas imagens. No entanto, esta tarefa é bastante trabalhosa e consome tempo, além de estar sujeita a uma significativa dependência do observador, diminuindo a precisão das aferições. Nesse sentido, o propósito deste trabalho é o desenvolvimento de um software que auxilie o profissional na realização dos testes, reduzindo a subjetividade devida aos observadores e correlacionando as leituras automatizadas com o sistema visual humano, sem a necessidade de se efetuar a correção dos resultados, como é realizado em diversos trabalhos encontrados na literatura. Para isso, foram utilizadas imagens obtidas por cinco sistemas CR e um método de detecção baseado na confecção de filtros circulares correlatores. A correlação com a visão humana fundamentou-se nos parâmetros de Weber, que descrevem o comportamento do sistema visual na discriminação do contraste em imagens digitais. A classificação dos discos contidos na imagem do phantom entre visível ou não visível foi efetuada a partir de uma ferramenta de mineração de dados conhecida como WEKA (Waikato Environment for Knowledge Analysis) associada ao algoritmo J48, que promove a construção de modelos de árvore de decisão. O resultado da implementação destas árvores de decisão foi a obtenção de um sistema de auxílio ao especialista que reforça a sua integridade na avaliação a partir de resultados estáveis e de fácil interpretação, atingindo acurácias de até 95%. / Technical requirements of image quality in mammography established by national and international norms include quality parameters which can be achieved by conducting periodic tests. It is recommended that some quality parameters are measured from images acquired by exposing specific phantoms, as CDMAM, in such systems. Nevertheless, this task is hard-working and time consuming, besides to be subject to a significant dependence of the observer, reducing the measurements accuracy. Accordingly, the purpose of this work is the development of a software to assist in the professional testing, reducing the subjectivity due to the observers and correlating the automated readings with the human visual system, without the need to make the correction of the results, as is done in many studies in the literature. For this, we used 57 images obtained for five CR systems and a method of detection based on circular correlators filters. The correlation with human vision was based on the Weber\'s parameters which describe the behavior of the visual system to discriminate the contrast in digital images. The classification of the image discs between visible or not visible was made from a data mining tool known as WEKA (Waikato Environment for Knowledge Analysis) associated with the J48 algorithm which promotes the construction of decision tree models. The result of the decision trees implementation was a system to aid the specialist, reinforcing the integrity of the assessment using stable results, easily interpreted, and reaching accuracies of up to 95%.

A qualidade dos exames mamográficos é uma preocupação constante do sistema de saúde mundial que se vê diante do desafio da detecção precoce do câncer de mama. As organizações responsáveis implementaram protocolos internacionais que consistem em testes de aceitação dos equipamentos mamográficos e de tomossíntese da mama, os quais estabelecem um padrão de qualidade nos serviços radiográficos. Porém, essas diretrizes têm como base o uso de objetos simuladores de mamas com espessuras e composições padrões, que muitas vezes não condizem com os perfis populacionais dos centros de diagnóstico. Neste trabalho, foi desenvolvido um sistema automatizado de rastreamento e gerenciamento de dados, que extrai as informações referentes ao processo de aquisição da mamografia digital e armazena-as em um servidor DICOM SCP (Service Class Provider). Após armazenadas, o sistema correlaciona os fatores de exposição das imagens, de forma a avaliar os níveis de referência em dose de radiação fornecidos pelos equipamentos. Como resultados, foi verificado que o perfil mamário dos centros institucionais de diagnóstico estudados não segue os valores de referência apresentados na literatura em termos de espessura e densidade mamária. Enquanto a mama padrão dos testes de garantia de qualidade é composta por 50 mm de espessura e 50% de densidade (50-50), a população estudada apresentou mamas comprimidas com média de 60 mm de espessura, com baixo percentual de tecido fibroglandular (menor que 25%). Portanto, o uso o sistema desenvolvido pode direcionar os testes de conformidade dos equipamentos para perfis mamários específicos. Esse direcionamento pode auxiliar na determinação de doses ótimas de radiação para melhoria da qualidade da imagem, produzindo valores de referência de grande utilidade para a qualidade dos serviços radiográficos. / Image quality assessment in mammography represents one of the greatest challenges that health services face in order to detect breast cancer early. The world health organization recommends quality assurance guidelines, which consist of acceptance tests for digital mammography (DM) and digital breast tomosynthesis (DBT), to standardize the radiological services. However, these guidelines are based on test objects widely used to simulate standard breasts in terms of composition and thickness, which often do not match with the demographic profiles in the breast care centers. In this thesis work, an automated system for tracking and data management was developed to extract the metadata (DICOM header) from the image acquisition process and to store it into a custom DICOM Service Class Provider (SPC). The developed system correlates the exposure factors\' info in order to evaluate the references for patient radiation dose provided by the manufacturers. As result of the data correlations, the reference required by the international guidelines for standard breasts are not a feasible representation for the demographic profile in the breast care center evaluated in terms of breast density and thickness. While the standard for quality assurance testing consists of breasts with 50 mm of thickness and 50% of density, the demographic population presented compressed breast thickness of approximately 60 mm and low fibroglandular tissue (less than 25%). Therefore, using the developed system should guide the quality assurance in digital mammography to specific breast profiles. This guidance may assist in determining optimal radiation doses to improve the image quality, producing useful benchmarks for the quality of radiological services.

Breast cancer is a major health concern in the United States. Mammography is the gold standard for screening breast cancer and screen-film technology is still widely used in the screening for breast cancer. However, screen-film systems have limited dynamic range and contrasts compared to digital systems, and do not offer integrated image processing capabilities. Recently, digital mammography has seen an upsurge in clinical adoption but current digital mammography systems are limited in terms of their spatial resolution. Therefore, high-resolution digital mammography systems with superior signal-to-noise ratio and contrast characteristics need to be explored. A monolithic, single module high-resolution (39 um) digital x-ray platform (Fairchild Imaging Inc., Milpitas, CA) was developed and characterized for digital mammography. The architecture was extended to a large area (16 x 24-cm) multi-module solid-state imager with variable resolution (39 and 78-um). In addition, a four module (16 x 16-cm) imaging architecture with 78-um pixel was explored for high-resolution contrast enhanced digital mammography for the detection of malignancy-associated angiogenesis. Simulations based on the cascaded linear systems framework were performed in order to characterize the physical properties of the imaging platforms such as the modulation transfer function (MTF), noise power spectra (NPS), and detective quantum efficiency (DQE). Experimental measurements of imager performance was also conducted and compared to model predicted results. Further, perceptual analysis of the prototype imaging platform for digital mammography was performed. Various imaging platforms were successfully developed and investigated to identify essential parameters for high-resolution digital x-ray breast imaging. The single module prototype exhibited physical characteristics that are favorable for digital mammography. Good agreement between model and experimental results were observed demonstrating the utility of such models for further system improvement. The large area 16 x 24-cm prototype demonstrated superior contrast-detail characteristics compared to a clinical FFDM system (100 um pixel) at both 39 and 78-um pixel sizes. Both experimental and theoretical results pointed towards the feasibility of contrast enhanced mammography at mean x-ray glandular dose levels substantially lower than mammography under the conditions investigated. Qualitative analysis of contrast enhanced digital mammography indicated favorable image quality.

The aim of the study is to assess the connection between women’s participation in breast cancer screening and beliefs towards breast cancer, breast self-examination and mammography. The objectives of the study: 1. To assess validity and reliability of Champion Health Belief Model Scale for beliefs towards breast cancer, breast self-examination and mammography screening for Lithuanian women. 2. To estimate perceived susceptibility, perceived severity, perceived benefits, perceived barriers, confidence and health motivation. 3. To compare beliefs towards breast cancer, breast self-examination and mammography screening of participant and non-participant women in the screening program. 4. To assess perceived barriers towards mammography screening. 5. To investigate the role of information about breast cancer and mammography screening for women‘s beliefs towards breast cancer, breast self-examination and mammography screening. CONCLUSIONS 1. Champion Health Belief Model Scale is a valid and reliable to assess beliefs towards breast cancer, breast self- examination and mammography. The barriers- mammography item “Regular mammography screening would make me worry about breast cancer” was inappropriate to the scale and expunged from the questionnaire. 2. Surveyed women did not feel much threat to get breast cancer. They overvalued benefits of breast self-examination and positively rated mammography screening. However, confidence to perform breast self-examination was properly low... [to full text] / Šio darbo tikslas buvo įvertinti atvykusių ir neatvykusių tikrintis mamografiškai moterų nuostatų į krūties vėžį, krūtų savityrą ir atrankinę mamografinę patikrą skirtumus. Tikslui pasiekti iškelti tokie uždaviniai: 1. Įvertinti Champion VL sveikatos įsitikinimų modelio klausimyno tinkamumą tirti Lietuvos moterų nuostatoms į krūties vėžį, krūtų savityrą ir atrankinę mamografinę patikrą. 2. Nustatyti moterų suvoktą krūties vėžio grėsmę, apsaugančios nuo krūties vėžio pasekmių elgsenos naudą ir kliūtis šiai veiklai, sveikos gyvensenos motyvaciją. 3. Palyginti atvykusių ir neatvykusių tirtis mamografiškai dėl krūties vėžio moterų nuostatas į krūties vėžį, krūtų savityrą ir atrankinę mamografinę patikrą. 4. Įvertinti dalyvavusių atrankinėje mamografinėje patikroje dėl krūties vėžio moterų kliūtis tirtis mamografiškai. 5. Ištirti papildomos informacijos apie krūties vėžį, mamografinę patikrą įtaką moterų nuostatoms į krūties vėžį, savityrą bei atrankinę mamografinę patikrą ir moterų dalyvavimui atrankinės patikros programoje. Išvados: 1. Patikrintas ir įteisintas VL Champion sveikatos įsitikinimų modelio skalės klausimynas yra tinkamas Lietuvos moterų nuostatoms į krūties vėžį, krūtų savityrą ir atrankinę mamografinę patikrą tirti. Sveikos gyvensenos motyvacijos skalė turi būti padalinta į požiūrio į sveiką gyvenseną ir veiklos sveikatos labui subskales. Kliūčių tirtis mamografiškai teiginys “reguliarus mamografinis ištyrimas verstų mane nerimauti dėl krūties vėžio” išbrauktas... [toliau žr. visą tekstą]

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The dominant powder scintillator in most medical imaging modalities for decades is Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Except for Gd2O2S:Tb there are alternative powder phosphor scintillators like Lu2SiO5:Ce and Gd2O2S:Eu that has been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital imaging devices like CCDs and CMOS based detectors. The purposes of the present thesis, is to investigate the fundamental imaging performance of a high resolution CMOS based imaging sensor combined with custom made Europium (Eu3+) activated Gd2O2S screens in terms of Modulation Transfer Function (MTF), Normalized Noise Power Spectrum (NNPS), Detective Quantum Efficiency (DQE), Noise Equivalent Quanta (NEQ) and Information Capacity (IC) covering the mammography and general radiography energy ranges. The CMOS sensor was coupled to two Gd2O2S:Eu scintillator screens with coating thicknesses of 33.3 and 65.1 mg/cm2, respectively, which were placed in direct contact with the photodiode array. The CMOS photodiode array, featuring 1200x1600 pixels with a pixel pitch of 22.5 m , was used as an optical photon detector. In addition to frequency dependent parameters (MTF, NPS, DQE) characterizing image quality, image information content was assessed through the application of information capacity (IC). The MTF was measured using the slanted-edge method to avoid aliasing while the Normalized NPS (NNPS) was determined by two-dimensional (2D) Fourier transforming of uniformly exposed images. Both parameters were assessed by irradiation under the RQA-5 protocol (70kVp digital-radiography) recommended by the International Electrotechnical Commission Reports 62220-1 and the W/Rh, W/Ag beam qualities (28kVp digital-mammography). The DQE was assessed from the measured MTF, NNPS and the direct entrance surface air-Kerma (ESAK) obtained from X-ray spectra measurement with a portable cadmium telluride (CdTe) detector. The spectral matching factor between the optical spectra emitted by the Gd2O2S:Eu and the Gd2O2S:Tb screens and the CMOS optical sensor, evaluated in the present study, was 1 and 0.95 respectively. The ESAK values ranged between 11.2-87.5 Gy , for RQA-5, and between 65.8-334 Gy , for W/Rh, W/Ag beam qualities. It was found that the detector response function was linear for the exposure ranges under investigation. Under radiographic conditions the MTF of the present system was found higher than previously published MTF data for a 48 m CMOS sensor, in the low up to medium frequency ranges. DQE was found comparable, while the NNPS appeared to be higher in the frequency range under investigation (0–10 cycles/mm). NEQ reached a maximum (73563 mm-2) in the low frequency range (1.8 cycles/mm), under the RQA 5 (ESAK: 11.2 Gy ) conditions. IC values were found to range between 1730-1851 bits/mm2. Under mammographic conditions MTF, NNPS and NEQ were found comparable to data previously published for the 48 m CMOS sensor while the DQE was found lower. The corresponding IC values were found ranging between 2475 and 2821 bits/mm2. The imaging performance of europium (Eu3+) activated Gd2O2S screens in combination to the CMOS sensor, investigated in the present study, was found comparable to those of Terbium (Tb) activated Gd2O2S screens (combined with the CMOS sensor). It can be thus claimed that red emitting phosphors could be suitably used in digital imaging systems, where the Silicon (Si) based photodetectors are more sensitive to longer wavelength ranges, and particularly in the red wavelength range. / -

Breast cancer screening and diagnosis in X-ray mammography rely on the detection and visualization of microcalcifications (μCs) and soft tissue masses. The early detection of breast cancer has been shown to decrease breast cancer mortality. The μCs are composed mainly of calcium with attenuation coefficients greater than that of soft tissue. The detection and visualization of μCs are relatively easy over a uniform tissue background, but limited by the ‘‘clutter’’ due to overlapping tissue background present on the mammogram. The clutter in tissue background arises from the structures of glandular tissue, vessels, and soft tissue masses in the breast. However, depending upon their size and location, the visualization of calcifications in mammograms may be limited by the superimposed anatomical structures even when the calcifications have adequate contrast-to-noise ratio (CNR). Dual-energy subtraction imaging techniques offer an alternative approach to the detection and visualization of μCs. With this technique, high- and low-energy images are separately acquired and ‘‘subtracted’’ from each other in a weighted fashion to cancel out the cluttered tissue structure so as to decrease the obscurity from overlapping tissue structures. In this study, computer simulations were developed in order to compute SNR as a function of various imaging parameters (X-ray spectra, μC size, breast thickness, and total exposure- 2 different cases) in Dual Energy Calcification images. Emphasis was placed on the monochromatization of the X-ray spectra with the use of K-edge filtering technique. Also, simulations provided values for various quality parameters of the spectra. Optimization was based on maximization of SNRtc while reducing total entrance exposure of the breast or Coefficient of Variation of the incident photons (CVIinc). / Ο καρκίνος του μαστού, ο οποίος είναι μια κοινή αιτία θανάτου μεταξύ των γυναικών του πληθυσμού, μπορεί να εκδηλωθεί μέσω μικροαποτιτανώσεων. Στη μαστογραφία, η ιατρική διάγνωση (συμπεριλαμβανομένων των τεχνικών ελέγχου) βασίζεται στην ανίχνευση και απεικόνιση αυτών των μικροαποτιτανώσεων (μCs) ή/ και της μάζας των μαλακών ιστών. Η έγκαιρη ανίχνευση του καρκίνου έχει αποδειχθεί ότι μειώνει τη θνησιμότητα λόγω καρκίνου του μαστού. Οι μCs αποτελούνται κυρίως από ασβέστιο (Ca), με αποτέλεσμα τη μεγαλύτερη εξασθένηση της ακτινοβολίας σε σχέση με τον μαλακό ιστό. Η ανίχνευση και η απεικόνιση των μικροαποτιτανώσεων είναι σχετικά εύκολη για έναν ομοιόμορφο μαστό. Ωστόσο, η απεικόνιση περιορίζεται από την ανομοιομορφία του υγιούς επικείμενου ιστού, που προκύπτει από τον αδενώδη ιστό, τις φλέβες και τους μαλακούς ιστούς στο μαστό. Ανάλογα με το βαθμό της ανομοιομορφίας, την αντίθεση των μCs, και τον τρόπο της επικάλυψης του ιστού, μπορεί να είναι δύσκολο να εντοπιστεί μια μικροαποτιτάνωση, παρόλο που ενδέχεται να υπάρχει επαρκής λόγος αντίθεσης προς θόρυβο (CNR). Η απεικόνιση με αφαιρετική τεχνική διπλής ενέργειας προσφέρει μια εναλλακτική προσέγγιση για την ανίχνευση και απεικόνιση των μCs. Με την τεχνική αυτή, αποκτώνται ξεχωριστά εικόνες υψηλής και χαμηλής ενέργειας και στη συνέχεια αφαιρείται η μια από την άλλη, με σκοπό να μειωθεί η ασάφεια από τις επικαλυπτόμενες δομές του ιστού. Στη παρούσα μελέτη, αναπτύχθηκε αλγόριθμος προσομοίωσης για τον υπολογισμό του SNR για διάφορους παράγοντες απεικόνισης (φάσματα ακτίνων-Χ, μέγεθος αποτιτάνωσης, πάχος μαστού και συνθήκες έκθεσης). Έμφαση δόθηκε στη τροποποίηση των φασμάτων ακτίνων-Χ ώστε να αποκτηθούν όσο το δυνατόν πιο «μονοχρωματικά» φάσματα με τη χρήση της τεχνικής K-edge. Η επιλογή των βέλτιστων φασμάτων υψηλής και χαμηλής ενέργειας βασίστηκε στην αύξηση του SNRtc με ταυτόχρονη μείωση της έκθεσης εισόδου στην επιφάνεια του μαστού ή τη μείωση του συντελεστή διακύμανσης των προσπιπτόντων φωτονίων στην είσοδο του μαστού (CVIinc).

Mammography is used to aid early detection and diagnosis systems. It takes an x-ray image of the breast and can provide a second opinion for radiologists. The earlier detection is made, the better treatment works. Digital mammograms are dealt with by Computer Aided Diagnosis (CAD) systems that can detect and analyze abnormalities in a mammogram. The purpose of this study is to investigate how to categories cropped regions of interest (ROI) from digital mammogram images into two classes; normal and abnormal regions (which contain microcalcifications). The work proposed in this thesis is divided into three stages to provide a concept system for classification between normal and abnormal cases. The first stage is the Segmentation Process, which applies thresholding filters to separate the abnormal objects (foreground) from the breast tissue (background). Moreover, this study has been carried out on mammogram images and mainly on cropped ROI images from different sizes that represent individual microcalcification and ROI that represent a cluster of microcalcifications. The second stage in this thesis is feature extraction. This stage makes use of the segmented ROI images to extract characteristic features that would help in identifying regions of interest. The wavelet transform has been utilized for this process as it provides a variety of features that could be examined in future studies. The third and final stage is classification, where machine learning is applied to be able to distinguish between normal ROI images and ROI images that may contain microcalcifications. The result indicated was that by combining wavelet transform and SVM we can distinguish between regions with normal breast tissue and regions that include microcalcifications.

Segmentation of mammograms pertains to assigning a meaningful label to each pixel found in the image. The segmented mammogram facilitates both the function of Computer Aided Diagnosis Systems and the development of tools used by radiologists during examination. Over the years many approaches to this problem have been presented. A surge in the popularity of new methods to image processing involving deep neural networks present new possibilities in this domain, and this thesis evaluates mammogram segmentation as an application of a specialized neural network architecture, U-net. Results are produced on publicly available datasets mini-MIAS and CBIS-DDSM. Using these two datasets together with mammograms from Hologic and FUJI, instances of U-net are trained and evaluated within and across the different datasets. A total of 10 experiments are conducted using 4 different models. Averaged over classes Pectoral, Breast and Background the best Dice scores are: 0.987 for Hologic, 0.978 for FUJI, 0.967 for mini-MIAS and 0.971 for CBIS-DDSM.