Regina Bitelli Medeiros

Exames radiológicos na gestação

Gestantes podem precisar ser submetidas a exames radiologicos para um diagnostico preciso e conduta correta. Nestes casos a exposicao a radiacao ionizante e seus efeitos sobre o feto sao motivo de preocupacao para a paciente e o seu medico. Na verdade, a maioria destes exames e segura e nao oferece risco significativo ao feto. No entanto, e importante que o radiologista conheca estes riscos potenciais para poder orientar adequadamente todos os envolvidos no atendimento.

Hardcopy quality parameters to ensure structures detection at digital mammography

Objective To develop procedures to ensure consistency of printing quality of digital images, by means of hardcopy quantitative analysis based on a standard image. Materials and Methods Characteristics of mammography DI-ML and general purpose DI-HL films were studied through the QC-Test utilizing different processing techniques in a FujiFilm®-DryPix4000 printer. A software was developed for sensitometric evaluation, generating a digital image including a gray scale and a bar pattern to evaluate contrast and spatial resolution. Results Mammography films showed maximum optical density of 4.11 and general purpose films, 3.22. The digital image was developed with a 33-step wedge scale and a high-contrast bar pattern (1 to 30 lp/cm) for spatial resolution evaluation. Conclusion Mammographic films presented higher values for maximum optical density and contrast resolution as compared with general purpose films. The utilized digital processing technique could only change the image pixels matrix values and did not affect the printing standard. The proposed digital image standard allows greater control of the relationship between pixels values and optical density obtained in the analysis of films quality and printing systems.

Comparing Mammographic Images

The main motivation in using intensity attributes to analyze and compare the technologies of mammography images acquisition is that such images are intrinsically of low contrast, which hinders the lesions detection and interpretation. Considering the viewing conditions, the study is under development to validate the influence of the contrast variation of many types of equipment on the radiologists diagnosis. However, for the image processing, the contrast variation can be considered a problem affecting the detection of important structures. A large-intensity variation in a digitized image can be manipulated by image-processing techniques and aid in lesion detection. However, low-intensity variation, as observed in the images of full-field digital mammography systems, can impede the detection of some lesions types, as masses are structures of low contrast. Therefore, the new technologies should be tested and validated for an adequate calibration according to the procedures adjacent to the image acquisition itself.

Readjustment of abdominal computed tomography protocols in a university hospital: impact on radiation dose.

Objective To assess the reduction of estimated radiation dose in abdominal computed tomography following the implementation of new scan protocols on the basis of clinical suspicion and of adjusted images acquisition parameters. Materials and Methods Retrospective and prospective review of reports on radiation dose from abdominal CT scans performed three months before (group A – 551 studies) and three months after (group B – 788 studies) implementation of new scan protocols proposed as a function of clinical indications. Also, the images acquisition parameters were adjusted to reduce the radiation dose at each scan phase. The groups were compared for mean number of acquisition phases, mean CTDIvol per phase, mean DLP per phase, and mean DLP per scan. Results A significant reduction was observed for group B as regards all the analyzed aspects, as follows: 33.9%, 25.0%, 27.0% and 52.5%, respectively for number of acquisition phases, CTDIvol per phase, DLP per phase and DLP per scan (p < 0.001). Conclusion The rational use of abdominal computed tomography scan phases based on the clinical suspicion in conjunction with the adjusted images acquisition parameters allows for a 50% reduction in the radiation dose from abdominal computed tomography scans.

QualIM®: software para treinamento na interpretação de imagens médicas digitais

OBJECTIVE: A software called QualIM® – Qualificacao de Imagens Medicas was developed for training of practitioners in the interpretation of digital mammograms classified according to BI-RADS® categories, utilizing images manipulation tools on state-of-the-art displays. MATERIALS AND METHODS: A Delphi 7-based system stores data resulting from mammographic findings interpretation during the training, comparing them with a golden-standard data set. The database includes computed radiography, direct radiography and digitized images. The software converts computed radiography and direct radiography images into TIFF format, preserving their original spatial and contrast resolution. During the training, the images are manipulated with the aid of the software tools (zoom, inversion, digital rulers and others). Depending on the image complexity, up to eight mammographic views, six ultrasonography images and two anatomopathological images can be displayed. RESULTS: The training was initiated in 2007 and is currently included in the radiology residency program. Based on data entered by the practitioner, the software automatically generates a BI-RADS compliant text that is compared with a database. CONCLUSION: The QualIM software is a digital educational tool aimed at assisting practitioners in the recognition of visual patterns on mammographic images as well as in the interpretation of mammograms based on the BI-RADS classification.

Survey of Image Quality and Radiographic Technique of Pediatric Chest Examinations Performed in Brazil

This work presents the results of a survey of Entrance Surface Air Kerma (Ke) values, image quality and radiographic exposure parameters used in pediatric chest examinations performed in Brazil. The study is part of the activities of the IAEA Regional Project RLA/9/057 whose objective is to optimize the radiological protection of patients in diagnostic and interventional radiology, nuclear medicine and radiotherapy. The survey was performed in four hospitals in Brazil. The study group consisted of 420 pediatric patients from two age groups (Group I- from two days to one year, Group II- from four to six years of age) undergoing chest PA/AP examinations. At the time of the examination the exposure parameters (kVp, mAs, focal-spot-to-film distance, etc.) and patient information (gender, height, weight and age) were recorded. The radiographic image quality was evaluated by the local radiologist based on the European Guidelines on Quality Criteria for Diagnostic Radiographic Images in Pediatrics. The results showed that the exposure parameters used on newborn patients were in the majority outside the 60-65kV range recommended by the European Guidelines for a good radiographic practice. In the case of examinations of patients with age between 4 and 6 years, 80% were performed with a peak tube voltage within the 60-80 kV range, as recommended by the European Guidelines. The Ke values, for both patient groups showed a wide dispersion, ranging from 30.7 μGy to 163.8 μGy for the newborn patients and from 34.5 μGy to 236.6 μGy for infant patients. It is possible to conclude that, in the Brazilian hospitals participating in this project, the radiographic techniques of pediatric chest images and the radiation protection need to be optimized.

Comparação Entre os Sistemas CR e DR Utilizados na Mamografia

Nosso objetivo foi comparar os parâmetros de desempenho dos sistemas mamograficos digitais e avaliar a qualidade das imagens associada as doses medias glandulares (DMG). Os parâmetros de qualidade e as DMG foram avaliados de acordo com protocolo europeu. A qualidade da imagem foi verificada utilizando o simulador CIRS11A. A DMG foi estimada para 1071 pacientes, sendo 799 exames realizados em sistema CR-Kodak utilizando os mamografos Performa-GE, MIV-LORAD e 12 placas fluorescentes (IP). Os demais exames foram realizados no sistema DR-Senographe DS-GE. Para a estimativa da DGM foram considerados os dados tecnicos e espessuras dos tecidos mamarios. Foram detectadas diferencas importantes na comparacao dos parâmetros de qualidade entre os sistemas, bem como nas DMG. Utilizando o sistema DR foi possivel detectar todos os tamanhos dos objetos existentes no simulador utilizando doses mais baixas. Ficou evidente as diferencas tecnologicas no que se refere aos parâmetros fisicos que influenciam na qualidade da imagem e nas doses de radiacao.

Influence of partial k-space filling on the quality of magnetic resonance images

Objective To study the influence that the scan percentage tool used in partial k-space acquisition has on the quality of images obtained with magnetic resonance imaging equipment. Materials and Methods A Philips 1.5 T magnetic resonance imaging scanner was used in order to obtain phantom images for quality control tests and images of the knee of an adult male. Results There were no significant variations in the uniformity and signal-to-noise ratios with the phantom images. However, analysis of the high-contrast spatial resolution revealed significant degradation when scan percentages of 70% and 85% were used in the acquisition of T1- and T2-weighted images, respectively. There was significant degradation when a scan percentage of 25% was used in T1- and T2-weighted in vivo images (p ≤ 0.01 for both). Conclusion The use of tools that limit the k-space is not recommended without knowledge of their effect on image quality.

Investigating the visual inspection subjectivity on the contrast-detail evaluation in digital mammography images

A major difficulty in the interpretation of mammographic images is the low contrast and, in the case of early detection of breast cancer, the reduced size of the features of malignancy on findings such as microcalcifications. Furthermore, image assessment is subject to significant reliance of the capacity of observation of the expert that will perform it, compromising the final diagnosis accuracy. Thinking about this aspect, this study evaluated the subjectivity of visual inspection to assess the contrast-detail in mammographic images. For this, we compared the human readings of images generated with the CDMAM phantom performed by four observers, enabling to determining a threshold of contrast visibility in each diameter disks present in the phantom. These thresholds were compared graphically and by statistical measures allowing us to build a strategy for use of contrast and detail (dimensions) as parameters of quality in mammography.

Development of computer techniques designed to aid tests of digital mammography systems quality evaluation with the phantom CDMAM 3.4

Image quality in digital mammography can be achieved by conducting periodic tests. It is recommended that some quality parameters be measured from images acquired by exposing specific phantoms, as CDMAM 3.4, in such systems. Whereas this task is hard-working and time consuming, this study has attempted to develop and compare two computational methods in order to assist the technical professional in performing the tests with such phantom images, reducing the subjectivity due to the observers. Tests used 27 phantom images obtained from six different digital mammography systems --- five CR-type and one DR-type. Both methods proved to be effective in detecting structures. However, the first one allowed the complete image processing and not just a region of interest, which makes it quite advantageous.