Discovering mammography-based machine learning classifiers for breast cancer diagnosis.

This work explores the design of mammography-based machine learning classifiers (MLC) and proposes a new method to build MLC for breast cancer diagnosis. We massively evaluated MLC configurations to classify features vectors extracted from segmented regions (pathological lesion or normal tissue) on craniocaudal (CC) and/or mediolateral oblique (MLO) mammography image views, providing BI-RADS diagnosis. Previously, appropriate combinations of image processing and normalization techniques were applied to reduce image artifacts and increase mammograms details. The method can be used under different data acquisition circumstances and exploits computer clusters to select well performing MLC configurations. We evaluated 286 cases extracted from the repository owned by HSJ-FMUP, where specialized radiologists segmented regions on CC and/or MLO images (biopsies provided the golden standard). Around 20,000 MLC configurations were evaluated, obtaining classifiers achieving an area under the ROC curve of 0.996 when combining features vectors extracted from CC and MLO views of the same case.

Stress analysis of cantilever-fixed partial denture connector design using the finite element method / Análise de tensões de desenhos de conectores de pontes cantilever pelo método dos elementos finitos

Purpose: To analyze the stress distribution on a cantilever-fixed partial denture after simulation of maximum mastication loads in order to optimize its design. Methods: A cantilever-fixed partial denture framework was designed in the CAD-CAM system Everest®Kavo v2.0 using two materials, titanium and zirconium, with connectors of 5.28 mm² and 9.05 mm², respectively. A finite element model was built for stress analysis using simulations of mastication load. Results: For zirconia, only the molar cantilever with the smaller connector area and a 0.5-mm fillet exceeded the considered threshold resistance value of 575 MPa. All the other designs yielded resistances below this value. For titanium, only cantilevers with 9.05 mm² connector area and fillets of 1 or 1.4 mm presented stress values inferior to titanium yield strengh. Conclusion: Within the limitations of this study, it can be concluded that titanium cantilever-fixed partial denture frameworks with a 5.28 mm² connector area cannot support maximum mastication loads; frameworks of this material require larger connectors with fillets introduced in the gingival embrasure. Zirconia, however, supports maximum bite forces in most situations with both molar and premolar design cantilevers. Precaution should be taken when dealing with smaller connectors of 5.28 mm².

Objetivo: Analisar a distribuição de tensões em próteses parciais fixas em cantilever após aplicação de cargas simuladoras da mastigação, de forma a otimizar o seu desenho. Metodologia: Obteve-se a infra-estrutura de uma prótese parcial fixa em cantilever no sistema CAD-CAM Everest®Kavo v2.0, considerando dois materiais: titânio e zircônia, com conectores de 5,28 mm² e 9,05 mm², respectivamente. Gerou-se um modelo de elementos finitos, onde foram efetuadas análises de tensões com cargas simuladoras da mastigação. Resultados: Para zircônia, apenas o cantilever molar com área de conector mais reduzida, e concordância de 0,5 mm, excedeu o valor de resistência 575 MPa. Para o titânio, apenas o cantilever de 9,05 mm², com concordâncias de 1 e 1,4 mm, apresentou valores inferiores à tensão do titânio. Conclusão: Dentro das limitações deste estudo pode-se concluir que as infra-estruturas de titânio em cantilever não suportam cargas mastigatórias máximas com uma área de conector de 5,28 mm² e requerem conectores de áreas superiores, com concordâncias introduzidas na embrasura gengival. A zircônia geralmente suporta forças mastigatórias máximas com cantilever molar ou pré-molar. Deve-se ter precaução quando a área dos conectores é reduzida para 5,28 mm².

Holographic stress analysis in a distal extension removable partial denture.

This study examines stress analysis of the mandible when submitted to mastication simulated forces over a distal extension removable partial denture. Two situations were analyzed upon loading: small pins had been placed over the bone crest and under the denture; low amplitude loads were applied over tooth 34-37. Holographic interferometry techniques were used to assess mandible's deformation. Results indicate that a correct adaptation of the denture base is critical to reduce stresses in the mandible. High stress levels in the second molar region suggest its non-inclusion in these prosthetic rehabilitations.