Martin Annis

Quantitative Digital Radiography Using A Flying Spot Scanner

One of the potentials of Digital Radiography has been for quantitative measurement, both spatial or contrast. This potential has been realized for contrast in computerized tomography. All projection radiography is somewhat limited in quantitative density analysis by line of sight integration. However, by comparing two successive images of the same subject, differences between them may be assessed. If that difference is due to contrast material which fills an organ, then the image differences can be used to infer geometric organ information. To be successful the imaging system must be of sufficiently low noise, have low external and internal scatter, and have a well known X-ray energy to digital signal transfer function. If these conditions are met, the signal differences may be calibrated absolutely. AS&Es flying spot digital radiographic system has been used to implement two examples of this technique. They are the determination of lung line of sight depth using Xenon as a contrast material and determination of cardiac chamber dimensions by using the cyclic variations in line of sight blood depth.

Digital radiography: spatial and contrast resolution

The addition of digital image collection and storage to standard and newly developed x-ray imaging techniques has allowed spectacular improvements in some diagnostic procedures. There is no reason to expect that the developments in this area are yet complete. But no matter what further developments occur in this field, all the techniques will share a common element, digital image storage and processing. This common element alone determines some of the important imaging characteristics. These will be discussed using one system, the Medical MICRODOSE System as an example.

Flow device to measure γ radioactivity and size of microparticles

A description is given of the design and performance of an instrument which measures particle size and radioactivity of individual microparticles after uptake of a γ‐emitting radioactive tracer. A flow system allows the activated particles to be measured quickly and individually, giving statistically significant frequency distributions in a short time. The purpose of the flow device is to measure some property of particles of a given type, provided this property is correlated with the uptake of the tracer. The instrument sizes particles in the 5–150‐μm‐diam range, and detects γ rays of E≳30 keV.