X-ray Backscatter Imaging Research Articles

A flying spot X-ray system for Compton backscatter imaging

A Compton X-ray backscatter imaging (CBI) system using a single detector and a mechanically rastered "flying spot" X-ray beam has been designed, built, and tested. While retaining the essential noninvasive imaging capability of previous multiple detector CBI devices, this single detector system incorporates several advances over earlier CBI devices: more efficient detection of scattered X-rays, reduced X-ray exposure, and a simplified scan protocol more suitable for use with humans. This new CBI system also has specific design features to permit automating data acquisition from multiple two-dimensional image planes for integration into a 3D dynamic surface image. A simulated multislice scan study of a human thorax phantom provided X-ray dosimetry data verifying a very low X-ray dose (~50 mrem) delivered by this imaging device. Validation experiments with mechanical models show that surface displacement at typical heart beat frequencies can be measured to the nearest 0.1 mm (SD).

Flux maximization techniques for compton backscatter depth profilometry

Resolution in x-ray backscatter imaging has often been hampered by low fluxes. But, for a given set of resolution requirements and geometric constraints, it is possible to define a maximization problem in the geometric parameters for which the solution is the maximum flux possible in those circumstances. In this way, resolution in noncritical directions can be traded for improved resolution in a desired direction. Making this the thickness, or surface normal direction, makes practicable the depth profiling of layered structures. Such techniques were applied to the problem of imaging the layered structure of corroding aircraft sheet metal joints using Compton backscatter.

Flux Maximization Techniques for Compton Backscatter Depth Profilometry

Resolution in x-ray backscatter imaging has often been hampered by low fluxes. But, for a given set of resolution requirements and geometric constraints, it is possible to define a maximization problem in the geometric parameters for which the solution is the maximum flux possible in those circumstances. In this way, resolution in noncritical directions can be traded for improved resolution in a desired direction. Making this the thickness, or surface normal direction, makes practicable the depth profiling of layered structures. Such techniques were applied to the problem of imaging the layered structure of corroding aircraft sheet metal joints using Compton backscatter.

ZT imaging system for layered thin wall structures

Abstract : Phase I demonstrated the feasibility of using a one-sided x-ray backscatter imaging technique called ZT to display very small delaminations, cracks, porosity, and chemical species differences in a variety of objects. Using both supplied carbon composites materials, some with known defects, and custom built phantoms, a series of experiments was performed to measure the sensitivity limits of the ZT technique to the various anomalies. The equipment consisted of ZT imaging system. During the execution of the program, we modified both the focussing collimator, the detectors and the X-ray beam scanning mechanism were modified to observe the differences in image quality caused by parametric changes in these items. Delaminations as small as 127 microns (0,005 in.) deep and 0.05 in. in diameter were imaged with the laboratory system. In the porosity phantom, holes as small as 787 microns in diameter were visualized. Our density investigations showed the ability to detect density differences as small as 2%. Also uncovered during the density experiments was the sensitivity of ZT to chemical species variations. A mathematical model is constructed which accurately predicts total system performance, including the backscatter process and the human detection probability.