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Proceedings Paper

Accuracy of distance measurements in biplane angiography
Author(s): Klaus D. Toennies; Satoru Oishi; David Koster; Gerhard Schroth
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Paper Abstract

Distance measurements of the vascular system of the brain can be derived from biplanar digital subtraction angiography (2p-DSA). The measurements are used for planning of minimal invasive surgical procedures. Our 90 degree-fixed-angle G- ring angiography system has the potential of acquiring pairs of such images with high geometric accuracy. The sizes of vessels and aneurysms are estimated applying a fast and accurate extraction method in order to select an appropriate surgical strategy. Distance computation from 2p-DSA is carried out in three steps. First, the boundary of the structure to be measured is detected based on zero-crossings and closeness to user-specified end points. Subsequently, the 3D location of the center of the structure is computed from the centers of gravity of its two projections. This location is used to reverse the magnification factor caused by the cone-shaped projection of the x-rays. Since exact measurements of possibly very small structures are crucial to the usefulness in surgical planning, we identified mechanical and computational influences on the geometry which may have an impact on the measurement accuracy. A study with phantoms is presented distinguishing between the different effects and enabling the computation of an optimal overall exactness. Comparing this optimum with results of distance measurements on phantoms whose exact size and shape is known, we found, that the measurement error for structures of size of 20 mm was less than 0.05 mm on average and 0.50 mm at maximum. The maximum achievable accuracy of 0.15 mm was in most cases exceeded by less than 0.15 mm. This accuracy surpasses by far the requirements for the above mentioned surgery application. The mechanic accuracy of the fixed-angle biplanar system meets the requirements for computing a 3D reconstruction of the small vessels of the brain. It also indicates, that simple measurements will be possible on systems being less accurate.

Paper Details

Date Published: 7 May 1997
PDF: 12 pages
Proc. SPIE 3031, Medical Imaging 1997: Image Display, (7 May 1997); doi: 10.1117/12.273907
Show Author Affiliations
Klaus D. Toennies, Inselspital Bern (Switzerland)
Satoru Oishi, Toshiba Nasu Works (Japan)
David Koster, Toshiba Medical Systems (Switzerland)
Gerhard Schroth, Inselspital Bern (Switzerland)

Published in SPIE Proceedings Vol. 3031:
Medical Imaging 1997: Image Display
Yongmin Kim, Editor(s)

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