Imaging with X-radiation is one of the most important diagnostic methods in medicine. The present use of shadow projection results in the information on depth in three-dimensional objects being lost. Structures in different depth are superimposed generating a confusing image which is difficult to interpret. These problems are partly solved by the well-known method of tomography. It, however, generates only one layer, whose location in depth cannot exactly be settled beforehand, and is rather time and radiation dose-consuming. These problems are overcome by tomosynthesis which utilizes a conventional tomographic equipment to record a set of radiographs each taken from a different position of the X-ray source. Arbitrary layers of the X-ray object can then be synthesized under visual control by reconstructing the projection geometry with holographic or electronic methods. Since about 3 s are required to record the individual radiographs, this method is still restricted to slowly moving parts of the human body. The recording time can be reduced to a few milliseconds by coded aperture imaging. It employs a small number of simultaneously operated, point-like X-ray sources to record a correspondingly coded X-ray image of the patient. Images of layers in deliberately chosen depth can then be generated by post-processing. The paper will describe the theory and various optic and electronic systems for implementing the algorithms involved. Experimental results will be demonstrated.
[1]
G Groh.
Holographic tomography using a circular synthetic aperture.
,
1971,
Applied optics.
[2]
G. Groh.
Some Optical Information Processing Systems
,
1972
.
[3]
E E Hoefer,et al.
Computer-controlled synthesis of tomograms by means of a TV storage tube.
,
1974,
IEEE transactions on bio-medical engineering.
[4]
Erhard Klotz,et al.
Three-dimensional coded aperture imaging using nonredundant point distributions
,
1974
.
[5]
D. DeRosier,et al.
The reconstruction of a three-dimensional structure from projections and its application to electron microscopy
,
1970,
Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.
[6]
M. Kock,et al.
Tomosynthesis: A holographic method for variable depth display
,
1973
.
[7]
Gabor T. Herman,et al.
Algorithms for reproducing objects from their X-rays
,
1972,
Comput. Graph. Image Process..
[8]
G Groh,et al.
3-d display of x-ray images by means of holography.
,
1970,
Applied optics.
[9]
Erhard Klotz,et al.
A new method for deconvoluting coded aperture images of three dimensional X-ray objects
,
1974
.