A short reader's guide to 3D tomographic reconstruction

3D electron microscopy of biological nanomachines: principles and applications

Transmission electron microscopy is a powerful technique for studying the three-dimensional (3D) structure of a wide range of biological specimens. Knowledge of this structure is crucial for fully understanding complex relationships among macromolecular complexes and organelles in living cells. In this paper, we present the principles and main application domains of 3D transmission electron microscopy in structural biology. Moreover, we survey current developments needed in this field, and discuss the close relationship of 3D transmission electron microscopy with other experimental techniques aimed at obtaining structural and dynamical information from the scale of whole living cells to atomic structure of macromolecular complexes.

An online interactive simulation system for medical imaging education

This report presents a recently developed web-based medical imaging simulation system for teaching students or other trainees who plan to work in the medical imaging field. The increased importance of computer and information technology widely applied to different imaging techniques in clinics and medical research necessitates a comprehensive medical imaging education program. A complete tutorial of simulations introducing popular imaging modalities, such as X-ray, MRI, CT, ultrasound and PET, forms an essential component of such an education. Internet technologies provide a vehicle to carry medical imaging education online. There exist a number of internet-based medical imaging hyper-books or online documentations. However, there are few providing interactive computational simulations. We focus on delivering knowledge of the physical principles and engineering implementation of medical imaging techniques through an interactive website environment. The online medical imaging simulation system presented in this report outlines basic principles underlying different imaging techniques and image processing algorithms and offers trainees an interactive virtual laboratory. For education purposes, this system aims to provide general understanding of each imaging modality with comprehensive explanations, ample illustrations and copious references as its thrust, rather than complex physics or detailed math. This report specifically describes the development of the tutorial for commonly used medical imaging modalities. An internet-accessible interface is used to simulate various imaging algorithms with user-adjustable parameters. The tutorial is under the MATLAB Web Server environment. Macromedia Director MX is used to develop interactive animations integrating theory with graphic-oriented simulations. HTML and JavaScript are used to enable a user to explore these modules online in a web browser. Numerous multiple choice questions, links and references for advanced study are provided in the tutorial for trainees to verify their understanding of each unit. It is expected that this tutorial will enhance medical imaging education, help trainees in subsequent analysis of image data, and form the basis for the development of more advanced technologies in the future.

Three-gamma annihilation imaging in positron emission tomography

It is argued that positron annihilation into three photons, although quite rare, could still be used as a new imaging modality of positron emission tomography. The information gained when the three decay photons are detected is significantly higher than in the case of 511 keV two-gamma annihilation. The performance of three-gamma imaging in terms of the required detector properties, spatial resolution and counting rates is discussed. A simple proof-of-principle experiment confirms the feasibility of the new imaging method.

PET kinetic modeling of 11C-acetate from projections

Positron emission tomography (PET) image reconstruction techniques inevitably introduce inaccuracies in images. To avoid these inaccuracies in PET kinetic modeling, kinetic parameters can directly be obtained from the projections. The present work describes modeling 11C-acetate in the sinograms measured in normal and ischemic rats with the Sherbrooke small animal PET scanner. Each bin of the dynamic sinograms was decomposed in its basis functions using spectral analysis technique in conjunction with the 11C-acetate kinetic model. Homogeneous structures were clearly separated and reconstructed as well as the kinetic model parameters. Rate constants were well correlated to those obtained by means of curve fitting from images.