Tomografía computarizada por rayos X: fundamentos y actualidad

Este artículo presenta una revisión de los fundamentos de la tomografía computarizada, empezando por un recuento de los inicios y progresos de esta técnica a través del tiempo, y continuando con una descripción de los principios físicos que rigen la producción de los rayos X. El artículo también discute las bases matemáticas para la reconstrucción de las imágenes a partir de proyecciones utilizando métodos analíticos o iterativos. En una sección independiente, se revisan los conceptos más importantes relacionados con los riesgos de la radiación ionizante y se discuten investigaciones recientes, algunas polémicas, acerca de los beneficios y riesgos asociados con la tomografía computarizada y cómo estos afectan los protocolos de adquisición de las imágenes. Finalmente, con base en los avances científicos y tendencias más recientes, el artículo propone las áreas que, presumiblemente, continuarán siendo el centro de atención de la tomografía computarizada de rayos X en los próximos años.This paper reviews the fundamentals of x-ray computed tomography. It starts by summarizing the early days of the technique and its evolution through time, as well as the physical principles of x-ray production. Subsequently, the mathematical principles of image reconstruction are discussed with emphasis in both analytical and iterative reconstruction methods. A complete section is dedicated to review the main concepts related with the risks of ionizing radiation, and discuss some of the most recent controversies about CT radiation and how those risks affect scanning protocols. Finally, based on the most recent advances and trends in CT, the paper discuss about those areas, which, presumably, will be the research focus of CT in the near future

Relative Merits of 3D Visualization for the Detection of Subtle Lung Nodules

A new imaging modality called bi-plane correlation imaging (BCI) was examined to determine the merits of using BCI with stereoscopic visualization to detect subtle lung nodules. In the first aim of this project, the optimal geometry for conventional projection imaging applications was assessed using a theoretical model to develop generic results for MTF, NNPS, eDQE. The theoretical model was tested with a clinical system using two magnifications and two anthropomorphic chest phantoms to assess the modalities of single view CXR and stereo/BCI. Results indicated that magnification can potentially improve the signal and noise performance of digital images. Results also demonstrated that a cross over point occurs in the spatial frequency above and below which the effects of magnification differ indicating that there are task dependent tradeoffs associated with magnification. Results indicated that magnification can potentially improve the detection performance primarily due to the air gap which reduced scatter by 30-40%. For both anthropomorphic phantoms, at iso-dose, eDQE(0) for stereo/BCI was ~100 times higher than that for CXR. Magnification at iso-dose improved eDQE(0) by ~10 times for BCI. Increasing the dose did not improve results. The findings indicated that stereo/BCI with magnification may improve detection of subtle lung nodules compared to single view CXR. With quantitative results in place, a pilot clinical trial was constructed. Human subject data was acquired with a BCI acquisition system. Subjects were imaged in the PA position as well as two oblique angles. Realistic simulated lesions were added to a subset of subjects determined to be nodule free. A BCI CAD algorithm was also applied. In randomized readings, radiologists read the cases according to viewing protocol. For the radiologist trainees, the AUC of lesion detection was seen to improve by 2.8% (p < 0.05) for stereoscopic viewing after monoscopic viewing compared to monoscopic viewing only. A 13% decrease in false positives was observed. Stereo/BCI as an adjunct modality was beneficial. However, the full potential of stereo/BCI as a replacement modality for single view chest x-ray may be realized with improved observer training, clinically relevant stereoscopic displays, and more challenging detection tasks.Doctor of Philosoph