CT dose reduction factors in the thousands using X-ray phase contrast

Phase-contrast X-ray imaging can improve the visibility of weakly absorbing objects (e.g. soft tissues) by an order of magnitude or more compared to conventional radiographs. Previously, it has been shown that combining phase retrieval with computed tomography (CT) can increase the signal-to-noise ratio (SNR) by up to two orders of magnitude over conventional CT at the same radiation dose, without loss of image quality. Our experiments reveal that as radiation dose decreases, the relative improvement in SNR increases. We discovered this enhancement can be traded for a reduction in dose greater than the square of the gain in SNR. Upon reducing the dose 300 fold, the phase-retrieved SNR was still almost 10 times larger than the absorption contrast data. This reveals the potential for dose reduction factors in the tens of thousands without loss in image quality, which would have a profound impact on medical and industrial imaging applications

Applications of Rapid Cardiac Micro-CT

Mouse models are an important tool in cardiovascular disease research and a non-invasive imaging method is an advantageous way of monitoring disease progression. Cardiac micro-CT is rapid imaging technique capable of quantifying changes in cardiac structure and function in mice. The goal of this thesis was to demonstrate the utility of this technique in monitoring disease progression in a longitudinal study, as well as its capability for evaluating other methods of measuring cardiac function in mice. In a longitudinal study, a mouse model of myocardial infarction was scanned weekly for four weeks; left ventricular volume and ejection fraction were measured from the images. Cardiac micro-CT was capable of tracking small changes in cardiac structure and function, with the MI mice demonstrating a significant increase in volume and a significant decrease in ejection fraction. Both inter- and intra-variability was low, indicating the results were highly reproducible. Contrast agents are essential to evaluating the heart in micro-CT images. A new blood-pool agent was evaluated to determine its suitability for use in cardiac micro-CT studies. The agent produced excellent enhancement for the first 30 minutes post-injection, and had a unique characteristic of enhancing the myocardium, which may prove useful in studies evaluating wall motion. The effect of x-ray dose delivered during a longitudinal micro-CT study was also evaluated. C57BL/6 mice were scanned weekly for six weeks; the total entrance dose delivered over the study was 5.04 Gy. No significant changes to the heart or lungs were detectable on the micro-CT images at six weeks, and the histology performed on myocardial and pulmonary tissue showed no indication of early inflammation at a cellular level. Micro-CT can therefore be used in longitudinal studies without concern of adverse effects. Cardiac micro-CT was used to evaluate conductance catheters, and found that the catheter volumes were drastically underestimated compared to the micro-CT volumes. It was also determined that catheterization has the potential for causing cardiac enlargement; 40% of the mice demonstrated enlarged hearts following the catheterization procedure. Overall, cardiac-gated micro-CT is a rapid and reproducible imaging technique, and is proving to be valuable tool in cardiovascular disease research

A preliminary approach to intelligent x-ray imaging for baggage inspection at airports

Identifying explosives in baggage at airports relies on being able to characterize the materials that make up an X-ray image. If a suspicion is generated during the imaging process (step 1), the image data could be enhanced by adapting the scanning parameters (step 2). This paper addresses the first part of this problem and uses textural signatures to recognize and characterize materials and hence enabling system control. Directional Gabor-type filtering was applied to a series of different X-ray images. Images were processed in such a way as to simulate a line scanning geometry. Based on our experiments with images of industrial standards and our own samples it was found that different materials could be characterized in terms of the frequency range and orientation of the filters. It was also found that the signal strength generated by the filters could be used as an indicator of visibility and optimum imaging conditions predicted

Compressive Phase Contrast Tomography

When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. In- terference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher con- trast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).Comment: 5 pages, "Image Reconstruction from Incomplete Data VI" conference 7800, SPIE Optical Engineering + Applications 1-5 August 2010 San Diego, CA United State

Challenges in imaging and predictive modeling of rhizosphere processes

Background Plant-soil interaction is central to human food production and ecosystem function. Thus, it is essential to not only understand, but also to develop predictive mathematical models which can be used to assess how climate and soil management practices will affect these interactions. Scope In this paper we review the current developments in structural and chemical imaging of rhizosphere processes within the context of multiscale mathematical image based modeling. We outline areas that need more research and areas which would benefit from more detailed understanding. Conclusions We conclude that the combination of structural and chemical imaging with modeling is an incredibly powerful tool which is fundamental for understanding how plant roots interact with soil. We emphasize the need for more researchers to be attracted to this area that is so fertile for future discoveries. Finally, model building must go hand in hand with experiments. In particular, there is a real need to integrate rhizosphere structural and chemical imaging with modeling for better understanding of the rhizosphere processes leading to models which explicitly account for pore scale processes

Radiography in Palaeopathology: Where Next?

YesRadiography has frequently been used during palaeopathological research, and plays an important role in the differential diagnosis of many diseases, including Paget¿s disease and carcinomas. Traditionally, radiographs were taken in hospitals with clinical equipment. However industrial radiography techniques have gradually become more commonly used, as their superior image quality and improved potential for diagnoses become recognised. The introduction of radiographic scanners has facilitated the digitisation of these images for dissemination and publication. However this is not all that radiographic digitisation can offer the researcher. Digital image processing (DIP) allows the researcher to focus on an area of interest and to adjust the brightness and contrast of the captured image. This allows the investigation of areas of high radio-opacity and radio-lucency, providing detailed images of the internal structures of bone and pathological lesions undetectable by the naked eye. In addition 3D effects, edge enhancement and sharpening algorithms, available through commonly used image processing software, can be very effective in enhancing the visibility of specific features. This paper will reveal how radiographic digitisation and manipulation can enhance radiographic images of palaeopathological lesions and potentially further our understanding of the bony manifestations of disease

Breast Cancer: Modelling and Detection

This paper reviews a number of the mathematical models used in cancer modelling and then chooses a specific cancer, breast carcinoma, to illustrate how the modelling can be used in aiding detection. We then discuss mathematical models that underpin mammographic image analysis, which complements models of tumour growth and facilitates diagnosis and treatment of cancer. Mammographic images are notoriously difficult to interpret, and we give an overview of the primary image enhancement technologies that have been introduced, before focusing on a more detailed description of some of our own recent work on the use of physics-based modelling in mammography. This theoretical approach to image analysis yields a wealth of information that could be incorporated into the mathematical models, and we conclude by describing how current mathematical models might be enhanced by use of this information, and how these models in turn will help to meet some of the major challenges in cancer detection

Switchable resolution in soft x-ray tomography of single cells.

The diversity of living cells, in both size and internal complexity, calls for imaging methods with adaptable spatial resolution. Soft x-ray tomography (SXT) is a three-dimensional imaging technique ideally suited to visualizing and quantifying the internal organization of single cells of varying sizes in a near-native state. The achievable resolution of the soft x-ray microscope is largely determined by the objective lens, but switching between objectives is extremely time-consuming and typically undertaken only during microscope maintenance procedures. Since the resolution of the optic is inversely proportional to the depth of focus, an optic capable of imaging the thickest cells is routinely selected. This unnecessarily limits the achievable resolution in smaller cells and eliminates the ability to obtain high-resolution images of regions of interest in larger cells. Here, we describe developments to overcome this shortfall and allow selection of microscope optics best suited to the specimen characteristics and data requirements. We demonstrate that switchable objective capability advances the flexibility of SXT to enable imaging cells ranging in size from bacteria to yeast and mammalian cells without physically modifying the microscope, and we demonstrate the use of this technology to image the same specimen with both optics