Shape-from-focus for real-time terahertz 3D imaging.

Thanks to significant advances in real-time terahertz imaging in terms of resolution and image quality, adapting and extending optical methods for 3D imaging at the millimeter scale is now promising. The shape-from-focus algorithm is a post-processing tool used in optical microscopy to reconstruct the external shape surface of a convex surface object. Images acquired at different distances from the object-side focal plane are implemented in this algorithm. We localize the best focus position in the stack of images for each pixel and then reconstruct the object in 3D due to the short depth of field. In this Letter, we propose an application of this algorithm in active and real-time terahertz imaging. We achieve the experimental reconstruction in 3D with a terahertz waves imaging system composed of a powerful source and a real-time terahertz camera.

Liquid index matching for 2D and 3D terahertz imaging.

Two-dimensional (2D) terahertz imaging and 3D visualization suffer from severe artifacts since an important part of the terahertz beam is reflected, diffracted, and refracted at each interface. These phenomena are due to refractive index mismatch and reflection in the case of non-orthogonal incidence. This paper proposes an experimental procedure that reduces these deleterious optical refraction effects for a cylinder and a prism made with polyethylene material. We inserted these samples in a low absorption liquid medium to match the sample index. We then replaced the surrounding air with a liquid with an optimized refractive index, with respect to the samples being studied. Using this approach we could more accurately recover the original sample shape by time-of-flight tomography.

Epimerization study on [18f]FDG produced by an alkaline hydrolysis on solid support under stringent conditions.

Since 1998, routine [18F]FDG syntheses are being carried out by alkaline hydrolysis on a solid support, i.e. the labeled intermediate is trapped on a tC18 solid phase extraction cartridge, purified and finally hydrolyzed within the cartridge, at room temperature, using sodium hydroxide. The present study demonstrated that no epimerization of [18F]FDG to [18F]FDM occurs even when 12 N NaOH is used and when the hydrolysis time is extended up to 1 h. The alkaline hydrolysis on solid support appears to be a simple method leading to [18F]FDG with high purity.