The HURRA filter: an easy method to eliminate collimator artifacts in high-energy gamma camera images / Filtro HURRA: una manera sencilla de eliminar los artefactos del colimador en la imagen con gammacámara de alta energía

Purpose. The correct determination and delineation of tumor/organ size is crucial in 2-D imaging in 131I therapy. These images are usually obtained using a system composed of a Gamma camera and high-energy collimator, although the system can produce artifacts in the image. This article analyses these artifacts and describes a correction filter that can eliminate those collimator artifacts. Methods. Using free software, ImageJ, a central profile in the image is obtained and analyzed. Two components can be seen in the fluctuation of the profile: one associated with the stochastic nature of the radiation, plus electronic noise and the other periodically across the position in space due to the collimator. These frequencies are analytically obtained and compared with the frequencies in the Fourier transform of the profile. A specially developed filter removes the artifacts in the 2D Fourier transform of the DICOM image. This filter is tested using a 15-cm-diameter Petri dish with 131I radioactive water (big object size) image, a 131I clinical pill (small object size) image, and an image of the remainder of the lesion of two patients treated with 3.7GBq (100mCi), and 4.44GBq (120mCi) of 131I, respectively, after thyroidectomy. Results. The artifact is due to the hexagonal periodic structure of the collimator. The use of the filter on large-sized images reduces the fluctuation by 5.8-3.5%. In small-sized images, the FWHM can be determined in the filtered image, while this is impossible in the unfiltered image. The definition of tumor boundary and the visualization of the activity distribution inside patient lesions improve drastically when the filter is applied to the corresponding images obtained with HE gamma camera. Conclusion. The HURRA filter removes the artifact of high-energy collimator artifacts in planar images obtained with a Gamma camera without reducing the image resolution. It can be applied in any study of patient quantification because the number of counts remains invariant. The filter makes possible the definition and delimitation of small uptakes, such as those presented in treatments with 131I (AU)

Objetivo. En terapia con 131I es crucial la correcta delimitación y determinación del tamaño del tumor/órgano en la imagen obtenida con un equipo de gammacámara y colimador de alta energía. Sin embargo, en estas imágenes aparecen artefactos debidos al colimador que dificultan dicha tarea. En este trabajo se analizan dichos artefactos y se describe un filtro corrector que puede eliminar los artefactos producidos por el colimador. Métodos. Utilizando software de descarga gratuita, Image J, se obtiene un perfil central en la imagen que se analiza. Pueden distinguirse 2 componentes en la fluctuación del perfil: uno asociado a la naturaleza estocástica de la desintegración radiactiva más el ruido electrónico y otro con periodicidad espacial en la posición debida al colimador. Las frecuencias correspondientes a esta periodicidad se obtienen analíticamente y se comparan con las frecuencias conseguidas en la transformada de Fourier del perfil. Se desarrolla un filtro capaz de suprimir estos artefactos en la transformada de Fourier 2D de la imagen DICOM. Este filtro se verifica con la imagen de una placa Petri de 15cm de diámetro rellena de agua radiactiva con 131I (objeto de tamaño grande), con la imagen de una pastilla clínica de 131I (objeto de pequeño tamaño) y con la imagen obtenida con gammacámara y colimador de alta energía del resto tiroideo de 2 pacientes tratados con 3,7GBq y 4.44GBq de 131I tras sufrir tiroidectomía. Resultados. Los artefactos se deben a la estructura periódica hexagonal del colimador. La aplicación del filtro en imágenes de objetos de gran tamaño reduce la fluctuación del 5,8% al 3,5%. En imágenes de pequeño tamaño la aplicación del filtro permite obtener el FWHM (ancho a mitad de altura), lo que resulta imposible en la imagen sin filtrar. La definición del contorno y la distribución de actividad en el interior de lesiones tiroideas mejoran substancialmente cuando se aplica el filtro a las imágenes obtenidas con gammacámara y colimador de alta energía. Conclusión. El filtro denominado HURRA suprime los artefactos en la imagen planar obtenida con colimador de alta energía sin reducir la resolución de la imagen. Puede ser utilizado en cualquier estudio de cuantificación en imagen de pacientes ya que el número de cuentas permanece invariante. El filtro permite la definición y delimitación de pequeñas captaciones como las que se producen en tratamientos con 131I (AU)

[Nuclear medicine in Spain: high technology 2013]. / Medicina nuclear en España: alta tecnología 2013.

This article details the high technology equipment in Spain obtained through a survey sent to the three main provider companies of equipment installed in Spain. The geographical distribution of high technology by Autonomous Communities and its antiquity have been analyzed.

[Neurological explorations in Nuclear Medicine. A Spanish survey]. / Exploraciones neurológicas en Medicina Nuclear. Encuesta española.

A representative Nuclear Medicine Service in Spain has two or three gammacameras. It performs neurologic studies one or two days at week wich account 2,1% of total workload. Brain Perfusion SPECT, specially in cognitive disorders, is the most frequent application. Neurooncology has a lower but established relevance. Neuroreceptors imaging are increasing in the last months. Emission tomography is obtained using a double-headed camera fitted with high-resolution parallel hole collimators and a half an hour total acquisition time. Datasets are reconstructed by filtered backprojection with Butterworth or Metz filtres. Images are visually interpreted with comparison to MRI and/or CT findings.

[The need for nuclear medicine specialists and gamma cameras]. / Definiendo la necesidad de especialistas y gammacámaras en Medicina Nuclear.

BACKGROUND: The ideal number of nuclear medicine specialists in relation to the needs of a given population should be defined by the institutions training such specialists. AIM: To establish the relationship between the number of gammacameras, nuclear medicine specialists and the number of inhabitants in different countries, including Chile. MATERIAL AND METHODS: Information was obtained from the International Atomic Energy Agency, Britannic and Canadian Nuclear Medicine Societies, Pan-American Health Organization and American College of Nuclear Physicians. RESULTS: Industrialized countries have approximately 1 specialist and 0.5-3.3 gammacameras per 100,000 inhabitants. The respective figures in Chile are 0.25 and 0.25. Due to the unequal distribution of resources in Chile, the specialist and gammacameras rate in the Metropolitan area is 0.6, some regions or communities do not have these resources and in other communities the rate can raise up to nine. CONCLUSIONS: Compared to industrialized countries, Chile lacks nuclear medicine specialists and gammacameras, and these resources are unevenly distributed.

Definiendo la necesidad de especialistas y gammacámaras en medicina nuclear / Defining the need of specialists and gammacameras in nuclear medicine

The aim of this work was to establish the relationship between the number of gammacameras, nuclear medicine specialists and the number of inhabitants in different countries, including Chile. Information was obtained from the International Atomic Energy Agency, Britannic and Canadian Nuclear Medicine Societies, Pan-American Health Organization and American College of Nuclear Physicians. Industrialized countries have approximately 1 specialist and 0.5-3.3 gammacameras per 100,000 inhabitants. The respective figures in Chile are 0.25 and 0.25. Due to the unequal distribution of resources in Chile, the specialists and gammacameras rate in the Metropolitan area is 0.6, some regions or communities do not have these resources and in other communities the rate can raise up to nine. Compared to industrialized countries, Chile lacks nuclear medicine specialists and gammacameras and these resources are unevently distributed