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Fast calculation of the exact radiological path for a three‐dimensional CT array
Author(s) -
Siddon Robert L.
Publication year - 1985
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.595715
Subject(s) - voxel , computer science , radiological weapon , path (computing) , radiation treatment planning , medical imaging , intersection (aeronautics) , radiography , dosimetry , algorithm , medical physics , artificial intelligence , radiation therapy , nuclear medicine , radiology , physics , medicine , engineering , programming language , aerospace engineering
Ready availability has prompted the use of computed tomography (CT) data in various applications in radiation therapy. For example, some radiation treatment planning systems now utilize CT data in heterogeneous dose calculation algorithms. In radiotherapy imaging applications, CT data are projected onto specified planes, thus producing “radiographs,” which are compared with simulator radiographs to assist in proper patient positioning and delineation of target volumes. All these applications share the common geometric problem of evaluating the radiological path through the CT array. Due to the complexity of the three‐dimensional geometry and the enormous amount of CT data, the exact evaluation of the radiological path has proven to be a time consuming and difficult problem. This paper identifies the inefficient aspect of the traditional exact evaluation of the radiological path as that of treating the CT data as individual voxels. Rather than individual voxels, a new exact algorithm is presented that considers the CT data as consisting of the intersection volumes of three orthogonal sets of equally spaced, parallel planes. For a three‐dimensional CT array of N 3 voxels, the new exact algorithm scales with 3 N , the number of planes, rather than N 3 , the number of voxels. Coded in fortran‐77 on a VAX 11/780 with a floating point option, the algorithm requires approximately 5 ms to calculate an average radiological path in a 100 3 voxel array.