Enhancing Compressed Sensing 4D Photoacoustic Tomography by Simultaneous Motion Estimation

A crucial limitation of current high-resolution 3D photoacoustic tomography (PAT) devices that employ sequential scanning is their long acquisition time. In previous work, we demonstrated how to use compressed sensing techniques to improve upon this: images with good spatial resolution and contrast can be obtained from suitably sub-sampled PAT data acquired by novel acoustic scanning systems if sparsity-constrained image reconstruction techniques such as total variation regularization are used. Now, we show how a further increase of image quality can be achieved for imaging dynamic processes in living tissue (4D PAT). The key idea is to exploit the additional temporal redundancy of the data by coupling the previously used spatial image reconstruction models with sparsity-constrained motion estimation models. While simulated data from a two-dimensional numerical phantom will be used to illustrate the main properties of this recently developed joint-image-reconstruction-and-motion-estimation framework, measured data from a dynamic experimental phantom will also be used to demonstrate their potential for challenging, large-scale, real-world, three-dimensional scenarios. The latter only becomes feasible if a carefully designed combination of tailored optimization schemes is employed, which we describe and examine in more detail

Laser-induced breakdown spectroscopy as a diagnostic tool for coal fines

Laser Induced Breakdown Spectroscopy (LIBS) is a technique that uses a laser, to focus down and atomize a sample of desired material. Focusing of the laser onto the material causes a plasma formation, which the material is broken down into excited ionic and atomic states. The atoms then emit characteristic optical radiation. Collection of the emitted light can be used to provide information on the elemental composition of the material. This research investigates a fundamental study of laser-induced breakdown spectroscopy (LIBS) applied to coal samples, coal fines, and fly ash. During this research, apparatus and methodology were developed to quantify the content of carbon, sulfur, iron and mercury in coal. It was observed carbon and mercury could be quantified using LIBS. A polygonal scanning mirror was added to the LIBS apparatus to observe lifetimes of emission lines. The data showed that each emission line showed different time dependent characteristics within the laser spark

Development of scanning ion conductance microscopy for biomedical applications

Imperial Users onl