ABSTRACT
Abstract Metal artifacts are common in clinical images. Many methods for artifact reduction have been published to overcome this problem. In this work, animage smoothing method for artifact reduction (ISMAR) is proposed for image quality improvement in patients with hip prosthesis and dental fillings, which caused metal artifacts. ISMAR was evaluated and compared with three well-known methods for metal artifact reduction (linear interpolation (LI), normalized metal artifact reduction (NMAR) and frequency split metal artifact reduction (FSMAR)). The new method is based on edge-preserving smoothing via L0 Gradient Minimization filter. Image quality was evaluated by two experienced radiologists completely blinded to the information about if the image was processed or not to suppress the artifacts. They graded image quality in a five points-scale, where zero is an index of clear artifact presence, and five, a whole artifact suppression. The new method had the best results and it was statistically significant respect to the other tested methods (p < 0.05). This new method has a better performance in artifact suppression and tissue feature preservation.
Resumen Los artefactos metálicos son comunes en las imágenes clínicas. Muchos métodos para la reducción de los artefactos han sido publicados para superar este problema. En el presente trabajo, un método de suavizado de imágenes para la reducción de artefactos (ISMAR) es propuesto para mejorar la calidad de la imagen en pacientes con prótesis de cadera y empastes dentales, los cuales causaron artefactos metálicos. ISMAR fue evaluado y comparado con otros tres métodos reconocidos por su desempeño en la reducción de los artefactos metálicos (Interpolación lineal (LI), reducción de artefactos de metal normalizados (NMAR) y reducción de artefactos de metal divididos en frecuencia (FSMAR)). El nuevo método se basa en el suavizado y conservación de bordes, utilizando para ello el filtro de minimización de gradiente L0. La calidad de la imagen fue evaluada por dos radiólogos experimentados completamente ciegos a la información sobre si la imagen fue procesada o no para suprimir los artefactos. Ellos calificaron la calidad de la imagen en una escala de cinco puntos, donde el cero indica la presencia de artefactos, y el cinco, una supresión total de los artefactos. El nuevo método tuvo los mejores resultados y fue estadísticamente significativo con respecto a los otros métodos probados (p < 0.05). Este nuevo método tiene un mejor rendimiento en la supresión de artefactos y en la conservación de las características de los tejidos.
ABSTRACT
AbstractObjective:The present study is aimed at contributing to identify the most appropriate OSEM parameters to generate myocardial perfusion imaging reconstructions with the best diagnostic quality, correlating them with patients' body mass index.Materials and Methods:The present study included 28 adult patients submitted to myocardial perfusion imaging in a public hospital. The OSEM method was utilized in the images reconstruction with six different combinations of iterations and subsets numbers. The images were analyzed by nuclear cardiology specialists taking their diagnostic value into consideration and indicating the most appropriate images in terms of diagnostic quality.Results:An overall scoring analysis demonstrated that the combination of four iterations and four subsets has generated the most appropriate images in terms of diagnostic quality for all the classes of body mass index; however, the role played by the combination of six iterations and four subsets is highlighted in relation to the higher body mass index classes.Conclusion:The use of optimized parameters seems to play a relevant role in the generation of images with better diagnostic quality, ensuring the diagnosis and consequential appropriate and effective treatment for the patient.
ResumoObjetivo:O presente trabalho visa contribuir para identificar quais os parâmetros OSEM que geram as reconstruções na cintilografia de perfusão do miocárdio com o maior valor clínico de diagnóstico, relacionando-os com as classificações de índice de massa corporal.Materiais e Métodos:Foram selecionados 28 pacientes adultos que realizaram cintilografia de perfusão do miocárdio em um hospital público. Cada paciente teve seu exame processado com o método OSEM em seis combinações diferentes de número de iterações e subsets. As imagens foram analisadas por especialistas em cardiologia nuclear, que consideraram o valor clínico de diagnóstico delas e indicaram quais as imagens que mais se adequavam à qualidade diagnóstica.Resultados:Em análise global da pontuação conforme as avaliações médicas, o arranjo de quatro iterações e quatro subsets gerou as imagens com melhor qualidade diagnóstica em todas as classes de índice de massa corporal, porém o arranjo com seis iterações e quatro subsets se destacou nas classes de maiores índices de massa corporal.Conclusão:A utilização de parâmetros otimizados parece ter papel importante em proporcionar reconstruções de melhor qualidade diagnóstica, garantindo-se assim que o paciente tenha o seu diagnóstico e consequente terapêutica encaminhados de forma mais adequada e eficaz.
ABSTRACT
As the great progress in computer technology, the image reconstruction of PET has been extensively studied, especially the fast methods being able to suppress the noise and meanwhile improve spatial resolution. This paper gives a brief description of the principle and research status of PET reconstructions, and that of 3D PET as well.