X-ray backscatter (XBS) provides a novel approach to the field of non-destructive evaluation (NDE) in the aerospace industry. XBS is conducted by collecting the radiation which is scattered from a sample illuminated by a well-defined Xray beam, and the technique enables objects to be scanned at a sub-surface level using single-sided access, and without the requirement for coupling with the sample. Single-sided access is of particular importance when the objects of interest are very large, such as aircraft components. Carbon fibre composite materials are being increasingly used as a structural material in aircraft, and there is an increasing demand for techniques which are sensitive to the delaminations which occur in these composites as a result of both large impacts and barely visible impact damage (BVID). The XBS signal is greatly enhanced for plastics and lightweight materials, making it an ideal candidate for probing sub-surface damage and defects in carbon fibre composites. Here we present both computer modelling and experimental data which demonstrate the capability of the XBS technique for identifying hidden defects in carbon fibre.
A disposable device is described for use in High Content Screening within the drug research process; it interfaces with a standard 384 well microtiter plate providing simultaneous full kinetic reaction data for a complete row of 24 wells. The device can be used in secondary screening for lead optimisation, for ADME (Absorption Distribution Metabolism and Excretion) assessment and toxicological assessment of candidate compounds.
The device is a microfluidic unit and incorporates the necessary substrate and reaction chemicals. The microfluidic circuitry includes mixing paths, a reaction chamber, a single use valve and a waste reservoir as well as electrical measurement contacts. Movement of the fluids is provided by a single vacuum line which is distributed to all 24 separate cells.
The device described incorporates a self-validation technique which provides a built in test facility.
This paper describes the requirements and constraints involved in the design of a digital scanning mammography system. The SNR model of Muntz is used to assess the influence of detector size and detected scatter-to-primary ratio on the detectability of microcalcifications in a breast phantom, and hence to consider the design of an optimized system. The effects of patient dose, exposure time and various technological constraints, such as x-ray tube power limits, maximum scanning speed and system MTF, are also discussed. It is demonstrated that the combined use of an air gap between the patient and the detector and a wider scanning slot can give the same scatter-to-primary ratio as a significantly smaller slot, while reducing the x- ray tube load. It is also demonstrated that, to some extent, the tube power constraints can be overcome by using higher kVp, less added filtration and a smaller source to patient distance.
The development of CCDs for use in dental radiology is now well established and provides a base technology for the development of mammography screening detectors. Techniques for overcoming the critical issues of image quality and detection area are discussed and include a 20 line pair/mm resolution capability.