Application of the CLEAN algorithm to three dimensional coded aperture imaging

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.

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Three-Dimensional Terahertz Coded-Aperture Imaging Based on Back Projection

Sensors ◽

10.3390/s18082510 ◽

2018 ◽

Vol 18 (8) ◽

pp. 2510 ◽

Cited By ~ 1

Author(s):

Shuo Chen ◽

Chenggao Luo ◽

Hongqiang Wang ◽

Wenpeng Wang ◽

Long Peng ◽

...

Keyword(s):

Computational Complexity ◽

Pulse Compression ◽

Signal To Noise Ratio ◽

Reference Signal ◽

Three Dimensional ◽

Coded Aperture ◽

Imaging Method ◽

Back Projection ◽

Coded Aperture Imaging ◽

Resolution Imaging

Terahertz coded-aperture imaging (TCAI) can overcome the difficulties of traditional radar in forward-looking and high-resolution imaging. Three-dimensional (3D) TCAI relies mainly on the reference-signal matrix (RSM), the large size and poor accuracy of which reduce the computational efficiency and imaging ability, respectively. According to the previous research on TCAI, traditional TCAI cannot reduce the heavy computational burden while the improved TCAI achieve reconstructing the target parts of different ranges in parallel. However, large-sized RSM still accounts for the computational complexity of traditional TCAI and the improved TCAI. Therefore, this paper proposes a more efficient imaging method named back projection (BP)-TCAI (BP-TCAI). Referring to the basic principle of BP, BP-TCAI can not only divide the scattering information in different ranges but also project the range profiles into different imaging subareas. In this way, the target parts in different subareas can be reconstructed simultaneously to synthesize the whole 3D target and thus decomposes the computational complexity thoroughly. During the pulse compression and projection processes, the signal-to-noise ratio (SNR) of BP-TCAI is also improved. This present the imaging method, model and procedures of traditional TCAI, the improved TCAI and the proposed BP-TCAI. Numerical experimental results prove BP-TCAI to be more effective and efficient than previous imaging methods of TCAI. Besides, BP-TCAI can also be seen as synthetic aperture radar (SAR) imaging with coding technology. Therefore, BP-TCAI opens a future gate combining traditional SAR and coded-aperture imaging.

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