Digital radiography for determination of primary tooth length: in vivo and ex vivo studies

Background. Methods for determining the root canal length of the primary tooth should yield accurate and reproducible results. In vitro studies show some limitations, which do not allow their findings to be directly transferred to a clinical situation. Aim. To compare the accuracy of radiographic tooth length obtained from in vivo digital radiograph with that obtained from ex vivo digital radiograph. Method. Direct digital radiographs of 20 upper primary incisors were performed in teeth (2/3 radicular resorption) that were radiographed by an intraoral sensor, according to the long-cone technique. Teeth were extracted, measured, and mounted in a resin block, and then radiographic template was used to standardise the sensor-target distance (30 cm). The apparent tooth length (APTL) was obtained from the computer screen by means of an electronic ruler accompanying the digital radiography software (CDR 2.0), whereas the actual tooth length (ACTL) was obtained by means of a digital calliper following extraction. Data were compared to the ACTL by variance analysis and Pearson’s correlation test. Results. The values for APTL obtained from in vivo radiography were slightly underestimated, whereas those values obtained from ex vivo were slightly overestimated. No significance was observed between APTL and ACTL. Conclusion. The length of primary teeth estimated by in vivo and ex vivo comparisons using digital radiography was found to be similar to the actual tooth length.

Scaling digital radiographs for templating in total hip arthroplasty using conventional acetate templates independent of calibration markers

We describe a scaling method for templating digital radiographs using conventional acetate templates independent of template magnification without the need for a calibration marker. The mean magnification factor for the radiology department was determined (119.8%, range117%-123.4%). This fixed magnification factor was used to scale the radiographs by the method described. 32 femoral heads on postoperative THR radiographs were then measured and compared to the actual size. The mean absolute accuracy was within 0.5% of actual head size (range 0 to 3%) with a mean absolute difference of 0.16mm (range 0-1mm, SD 0.26mm). Intraclass Correlation Coefficient (ICC) showed excellent reliability for both inter and intraobserver measurements with ICC scores of 0.993 (95% CI 0.988-0.996) for interobserver measurements and intraobserver measurements ranging between 0.990-0.993 (95% CI 0.980-0.997).

Patient exposure monitoring and radiation qualities in two-dimensional digital x-ray imaging

The methods for estimating patient exposure in x-ray imaging are based on the measurement of radiation incident on the patient. In digital imaging, the useful dose range of the detector is large and excessive doses may remain undetected. Therefore, real-time monitoring of radiation exposure is important. According to international recommendations, the measurement uncertainty should be lower than 7% (confidence level 95%). The kerma-area product (KAP) is a measurement quantity used for monitoring patient exposure to radiation. A field KAP meter is typically attached to an x-ray device, and it is important to recognize the effect of this measurement geometry on the response of the meter. In a tandem calibration method, introduced in this study, a field KAP meter is used in its clinical position and calibration is performed with a reference KAP meter. This method provides a practical way to calibrate field KAP meters. However, the reference KAP meters require comprehensive calibration. In the calibration laboratory it is recommended to use standard radiation qualities. These qualities do not entirely correspond to the large range of clinical radiation qualities. In this work, the energy dependence of the response of different KAP meter types was examined. According to our findings, the recommended accuracy in KAP measurements is difficult to achieve with conventional KAP meters because of their strong energy dependence. The energy dependence of the response of a novel large KAP meter was found out to be much lower than with a conventional KAP meter. The accuracy of the tandem method can be improved by using this meter type as a reference meter. A KAP meter cannot be used to determine the radiation exposure of patients in mammography, in which part of the radiation beam is always aimed directly at the detector without attenuation produced by the tissue. This work assessed whether pixel values from this detector area could be used to monitor the radiation beam incident on the patient. The results were congruent with the tube output calculation, which is the method generally used for this purpose. The recommended accuracy can be achieved with the studied method. New optimization of radiation qualities and dose level is needed when other detector types are introduced. In this work, the optimal selections were examined with one direct digital detector type. For this device, the use of radiation qualities with higher energies was recommended and appropriate image quality was achieved by increasing the low dose level of the system.

Radiopacity of restorative materials using digital images

The radiopacity of esthetic restorative materials has been established as an important requirement, improving the radiographic diagnosis. The aim of this study was to evaluate the radiopacity of six restorative materials using a direct digital image system, comparing them to the dental tissues (enamel-dentin), expressed as equivalent thickness of aluminum (millimeters of aluminum). Five specimens of each material were made. Three 2-mm thick longitudinal sections were cut from an intact extracted permanent molar tooth (including enamel and dentin). An aluminum step wedge with 9 steps was used. The samples of different materials were placed on a phosphor plate together with a tooth section, aluminum step wedge and metal code letter, and were exposed using a dental x-ray unit. Five measurements of radiographic density were obtained from each image of each item assessed (restorative material, enamel, dentin, each step of the aluminum step wedge) and the mean of these values was calculated. Radiopacity values were subsequently calculated as equivalents of aluminum thickness. Analysis of variance (ANOVA) indicated significant differences in radiopacity values among the materials (P<0.0001). The radiopacity values of the restorative materials evaluated were, in decreasing order: TPH, F2000, Synergy, Prisma Flow, Degufill, Luxat. Only Luxat had significantly lower radiopacity values than dentin. One material (Degufill) had similar radiopacity values to enamel and four (TPH, F2000, Synergy and Prisma Flow) had significantly higher radiopacity values than enamel. In conclusion, to assess the adequacy of posterior composite restorations it is important that the restorative material to be used has enough radiopacity, in order to be easily distinguished from the tooth structure in the radiographic image. Knowledge on the radiopacity of different materials helps professionals to select the most suitable material, along with other properties such as biocompatibility, adhesion and esthetic.

Estudo em suínos sobre osteotomia com brocas de alta e baixa rotação e refrigeração líquida: análise radiográfica digital densitométrica em tecido ósseo alveolar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Subtração digital radiográfica: identificação precoce de perdas minerais em esmalte

Pós-graduação em Biopatologia Bucal - ICT

Análise de um regulador de velocidade digital para a Usina Hidroelétrica de Curuá-Una

Analisa uma proposta de um controlador digital para o regulador de velocidade da Usina Hidroelétrica de Curuá-Una, utilizando duas estratégias de projeto, a estratégia indireta com o projeto do controlador sendo feito no plano contínuo e depois discretizado e a estratégia direta, em que o controlador é projetado inteiramente no plano discreto. O conhecimento gerado no simulador é de grande importância, pois é uma das grandes ferramentas para avaliar o comportamento dos controladores digitais propostos, em ambiente seguro. O estudo dos controladores também permite uma substituição de equipamentos antigos, com produção descontinuada, por equipamentos novos que permitem a confecção de controladores modernos, digitais e inteligentes, que proporcionam uma substituição de técnicas antigas de controle por estratégias avançadas de controle, maximizando o rendimento do sistema em condições adversas de operação. O trabalho levanta as diferenças, vantagens e desvantagens de cada controlador, com o objetivo de auxiliar na escolha do controlador mais adequado para projetos de controladores avançados: tipo um controle adaptativo, controle fuzzy ou controle neural. As dificuldades de projeto e os resultados das simulações foram os principais indicadores na avaliações dos dois RV digitais projetados. De uma forma geral o RV digital direto apresentou melhor desempenho, estabilidade e menor esforço computacional, entretanto, o RV digital indireto mostrou desempenho similar, menor degradação devido às não linearidades e ao menor esforço de projeto.

Análise histológica, histométrica e fractal de enxerto ósseo autógeno, em elevação de seio maxilar: estudo clínico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparação entre metodologias de controle de qualidade em mamografia digital

The best way to detect breast cancer is by screening mammography. The mammography equipments are dedicated and require a rigorous quality control in order to have a good quality image and to early detect this disease. The digital equipment is relatively new in the market and there isn’t a national rule for quality control for several types of digital detectors. This study has proposed to compare two different tests manuals for quality control provided by the manufacturers of digital mammography equipments, and also compare them to the “European guidelines for quality assurance in breast cancer screening and diagnosis “(2006). The studied equipments were: Senographe 2000D from General Electric (GE) and the Hologic Selenia Lorad. Both were digital mammography equipments, the GE unit presents an indirect digital system and the other presents a direct digital system. Physical parameters of the image have been studied, such as spatial resolution, contrast resolution, noise, signal-tonoise ratio, contrast-to-noise ratio and modulation transfer function. After that, a study of the importance of quality control and the requirement to implement a Quality Assurance Program has been done. One data collection was done to compare those manual, it was done by checking which tests are indicated and the minimum frequency which they should be conducted in accordance with each manufacturer. The tests were performed by different methodologies and the results were compared. The examined tests were: the breast entrance skin dose, mean glandular dose, contrast-to-noise ratio, signal-to-noise ratio, automatic exposure control and automatic control of density, modulation transfer function, equipment resolution, homogeneity and ghost

Correlation of Fractal Dimension with Histomorphometry in Maxillary SinuLifting Using Autogenous Bone Graft

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Discrete control algorithms for a tubular ammonia reactor

The specific objective of this paper is to develop direct digital control strategies for an ammonia reactor using quadratic regulator theory and compare the performance of the resultant control system with that under conventional PID regulators. The controller design studies are based on a ninth order state-space model obtained from the exact nonlinear distributed model using linearization and lumping approximations. The evaluation of these controllers with reference to their disturbance rejection capabilities and transient response characteristics, is carried out using hybrid computer simulation.

Efeitos do tratamento periodontal não cirúrgico sobre a densidade e altura óssea alveolar

O objetivo deste trabalho foi avaliar o efeito do tratamento periodontal não cirúrgico (TPNC), na densidade e na altura óssea alveolar, em pacientes com periodontite, utilizando radiografias digitais diretas. Cento e um sítios, em dezenove pacientes (idade média 36 7.3 anos) foram acompanhados no dia 0, e 90 e 180 dias após TPNC. Os índices clínicos de profundidade de bolsa a sondagem (PBS), nível de inserção clínica, sangramento à sondagem e índice de placa foram registrados e radiografias digitais foram feitas. A densidade foi analisada através de regiões ósseas de interesse colocadas sobre a crista óssea alveolar (ROI I) e sobre o osso medular (ROI II). A altura óssea alveolar foi medida através da distância da crista óssea alveolar até a junção cemento esmalte. Os sítios profundos (PBS ≥ 5mm) apresentaram uma melhora clínica significante (p <0.01), acompanhada de um aumento na densidade da ROI I (p <0.01). A ROI II mostrou um aumento na densidade dos sítios com PBS ≤ 3mm em pacientes com periodontite agressiva (p <0.05). No entanto, houve diminuição nos sítios com PBS ≥ 5mm nesses mesmos pacientes (p <0.03). A altura óssea alveolar não sofreu alteração após TPNC. Após o tratamento periodontal não cirúrgico, observou-se que as radiografias obtidas através da técnica digital direta parecem mostrar um aumento na densidade da crista óssea, nos sítios profundos dos pacientes com periodontite. No entanto, a redução da profundidade de bolsa e do ganho no nível de inserção clínica não foi acompanhada por alterações significantes na altura óssea alveolar nestes sítios.

Sistemas digitais directos vs indirectos : níveis de referência de diagnóstico locais na radiografia de tórax em projeção postero-anterior em dois hospitais portugueses

Este estudo teve como objetivo avaliar e comparar as doses de radiação recolhidas numa amostra de 69 pacientes, em dois hospitais, com diferentes métodos de aquisição de imagem digital, direta e indireta, que realizaram radiografia de tórax, em projeção postero-anterior (PA). Para os dois hospitais, a dose à entrada da pele (DEP) e efectiva (E), foram medidas usando o software PCXMC para comparação entre si e com referências internacionais. No Hospital A, com aquisição digital direta, a média de DEP foi de 0,089 mGy e a média de E foi 0,013 mSv. No Hospital B, com aquisição digital de indireta, a média de DEP foi de 0.151 mGy e a média de E foi 0.030mSv. Em ambos os hospitais, as doses médias não ultrapassaram os limites recomendados por lei (0,3 mGy). Para a radiografia de tórax PA, o nível de referência diagnostico (NRD) local calculado foi 0.107 mGy, para o Hospital A e 0.164 mGy, para o Hospital B. Na radiografia de tórax PA, a utilização de um sistema de aquisição direta implicou uma redução de dose de 41 %, concordante com as referências disponíveis que apontam para a redução da dose de cerca de 50 % entre os dois sistemas.

Radiographic assessment of bone density around integrated titanium implants after ovariectomy in rats

Objectives:This study evaluated the influence of ovariectomy 8 weeks after implant placement on bone integrated to titanium implants.Materials and methods:Thirty-eight female rats were submitted to a titanium implant at the tibiae proximal methaphysis. After a healing period of 8 weeks the animals were randomly divided into three groups: control (CTL-10 animals), sham-operated (SHAM-14 animals) and ovariectomy (OVX-14 animals). The CTL group was then sacrificed in order to confirm integration of the implant. The SHAM group was submitted to fictitious surgery and the OVX group was submitted to bilateral ovariectomy. After 12 weeks post-implant placement, the SHAM and OVX groups were sacrificed. In order to confirm the systemic osteopenia in rats, a dual-energy X-ray absorptiometry (DXA) was performed. For the evaluation of bone density, digital radiographs were taken. The grey level of the bone adjacent to implant was measured using image software and the bone density was calculated at six points on both sides of the implant.Results:Densitometry measurements of the femur confirmed systemic bone mass loss in the OVX group. Individualized bone analyses of different regions surrounding the implant showed a significantly lower radiographic bone density (P < 0.05) in the cancellous region of the OVX group (77.48 +/- 23.39 grey levels) when compared with the CTL and SHAM groups (91.61 +/- 32.10 and 102.57 +/- 32.50 grey levels, respectively).Conclusions:The present study showed a decrease of the radiographic bone density in the cancellous region of bone around titanium implants placed 8 weeks before ovariectomy in rats.

A new microcontrolled structural health monitoring system based on the electromechanical impedance principle

This article presents a new method to detect damage in structures based on the electromechanical impedance principle. The system follows the variations in the output voltage of piezoelectric transducers and does not compute the impedance itself. The proposed system is portable, autonomous, versatile, and could efficiently replace commercial instruments in different structural health monitoring applications. The identification of damage is performed by simply comparing the variations of root mean square voltage from response signals of piezoelectric transducers, such as lead zirconate titanate patches bonded to the structure, obtained for different frequencies of the excitation signal. The proposed system is not limited by the sampling rate of analog-to-digital converters, dispenses Fourier transform algorithms, and does not require a computer for processing, operating autonomously. A low-cost prototype based on microcontroller and digital synthesizer was built, and experiments were carried out on an aluminum structure and excellent results have been obtained. © The Author(s) 2012.