Adaptation of image reconstruction algorithm for purposes of ultrasound transmission tomography (UTT)
Abstract
In this research, the convolution and backprojection method has been adapted for the purposes of image reconstruction in ultrasound transmission tomography (UTT). In particular, a complete computer algorithm enabling the use of different convolving and interpolation functions has been developed. A technique of reducing and scaling the tomographic measuring data to minimize the reconstruction errors is proposed. The convolution and backprojection method was optimized through a choice of a versatile convolving function and a simple interpolation function, and it was tested using simulated and actual tomographic measuring data. After reconstruction, good-quality images were obtained. It has been found that the number of measuring rays determines the resolution of an image, the accuracy with which the size of structures is imaged and the accuracy with which the image point values are reconstructed, whereas the number of measuring projections determines the dynamics and distortion of an image. Because of computation time and image blur, an optimum reconstruction grid size, according to the visualization quality criterion, should be chosen. The convolution and backprojection algorithm optimized in this research can be applied directly to the UTT visualization of the internal structure of objects as a distribution of local sound velocities in this structure, reconstructed on the basis of measurements of mean times of the passage of an ultrasonic wave through a cross-section of an object immersed in water, in a parallel ray projection geometry.References
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[3] T. Gudra, K. Opielinski and W. Selwesiuk, Experimental setup for ultrasound transmission tomography [in Polish], Proceedings of XLIII Open Seminar on Acoustics OSA’96, 1, 259–264 (1996).
[4] A.K. Jain, Fundamentals of digital image processing, Prentice-Hall, Englewood Cliffs, New Jersey 1989, p. 570.
[5] A.C. Kak and M. Slaney, Principles of computerized tomographic imaging, The IEEE Inc., IEEE Press, New York 1988, p. 329.
[6] R.M. Lewitt, Reconstruction algorithms: transform methods, Proceedings of the IEEE, 71, 3, 390–408 (1983).
[7] S.A. Nielsen, K.K. Borum and H.E. Gundtoft, Veryfying an ultrasonic reconstruction algorithm for non-destructive tomography, Proc. Of The 1995World Congress on Ultrasonics, 447–450 (1995).
[8] K. Opieliński, Computer model of ultrasound transmission tomography: reconstruction of images [in Polish], Proceedings of XLIII Open Seminar on Acoustics OSA’96, 2, 547–552 (1996).
[9] K. Opieliński, Imaging of object’s internal structure by ultrasound transmission tomography
(UTT) on the basis of computer simulation of acoustic parameters [in Polish], Acoustics in Technology,
Medicine and Culture — KBN Grant Projects carried out in the years 1993–1995, 215–220
(1996).
[10] K. Opieliński, Reconstruction of image of object’s internal structure by ultrasound transmission tomography (UTT) on the basis of computer simulation of ultrasound velocity measurements [in Polish], Molecular and Quantum Acoustics, 17, 219–226 (1996).
[11] G.N. Ramachandran and A.V. Lakshminarayanan, Three dimensional reconstructions from radiographs and electron micrographs: Application on convolution instead of Fourier transforms, Proc. Nat. Acad. Sci., 68 (1971).
[12] L.A. Shepp and B.F. Logan, The Fourier reconstruction of a head section, IEEE Trans. Nucl. Sci., NS-21 (1974).
[13] M. Stapper and G. Sollie, Ultrasound transmission tomography by means of a personal computer, Ultrasonics International’85, 935–940 (1985).
