Automated Hybrid TACT^® Volume Reconstructions

Summary

Objectives: To design, implement in Java™, and evaluate a method and means for the automated localization of artificial landmarks in optical images for tuned-aperture computed tomography^® (TACT^®) that allows the replacement of radiographic with optical landmarks.

Methods: Circular, colored, optical landmarks were designed to provide flexibility with regard to landmark constellation, imaging equipment, and lighting conditions. The landmark detection was based on Hough transforms (HT) for ellipses and lines. The HT for ellipses was extended to enable selective detection of bright ellipses on a dark background and vice versa, and the number of irrelevant votes in the accumulator arrays was reduced. An experiment was performed in vitro to test the automated landmark localization scheme, verify registration accuracy, and measure the required computation time.

Results: A visual evaluation of the tomographic slices that were produced using the new method revealed good registration accuracy. A comparison to tomographic slices similarly produced by means of conventional TACT showed identical results. The algorithm ran sufficiently fast on standard hardware to allow landmark localization in “real time” during successive image acquisition in clinical applications.

Conclusions: The proposed method provides robust automated localization of landmarks in optical images. Using a hybrid imaging system, TACT can now be clinically applied without manual interaction of a human operator and without radiopaque landmarks, which might cover anatomic details of diagnostic interest.

Keywords

Computer-assisted image processing - X-ray computed tomography - three-dimensional imaging

• References

• 1 Grant DG. Tomosynthesis: A three-dimensional radiographic imaging technique. IEEE Trans Biomed Eng 1972; 19: 20-8.
• 2 Webber RL, Horton RA, Tyndall DA, Ludlow JB. Tuned-aperture computed tomography (TACTTM). Theory and application for threedimensional dento-alveolar imaging. Dentomaxillofac Radiol 1997; 26: 53-62.
• 3 Chai-U-Dom O, Ludlow JB, Tyndall DA, Webber RL. Comparison of conventional and TACT® (tuned aperture computed tomography) digital subtraction radiography in detection of pericrestal bone-gain. J Periodont Res 2002; 37: 147-53.
• 4 Nance R, Tyndall D, Levin LG, Trope M. Identification of root canals in molars by tuned-aperture computed tomography. Int Endontic J 2000; 33: 392-6.
• 5 Suryanarayanan S, Karellas A, Vedantham S, Baker SP, Glick SJ, D’Orsi CJ, Webber RL. Evaluation of linear and nonlinear tomosynthetic reconstruction methods in digital mammography. Acad Radiol 2001; 8: 219-24.
• 6 Fahey FH, Grow KL, Webber RL, Harkness BA, Bayram E, Hemler PF. Emission tuned-aperture computed tomography: A novel approach to scintimammography. J Nucl Med 2001; 42: 1121-7.
• 7 Webber RL, Robinson SB, Fahey FH. Threedimensional, tuned-aperture computed tomography reconstruction using hybrid imaging systems. In preparation. Correspondence to: Frederic H. Fahey, DSc, Division of Nuclear Medicine, Children’s Hospital Boston, Boston, MA 02115, USA. E-mail. [e-mail] 2002
• 8 Faugeras O. Three-Dimensional Computer Vision. Cambridge: MIT Press; 1993
• 9 Jang G, Kim S, Lee W, Kweon I. Color landmark based self-localization for indoor mobile robots. In: Proceedings of the 2002 IEEE International Conference on Robotics and Automation (ICRA 2002). Piscataway: IEEE; 2002: 1037-42.
• 10 Jiang B, You S, Neumann U. Camera tracking for augmented reality media. In: Proceedings of the 2000 IEEE International Conference on Multimedia and Expo (ICME 2000). Piscataway: IEEE; 2000: 1637-40.
• 11 State A, Hirota G, Chen DT, Garrett WF, Livingston MA. Superior augmented reality registration by integrating landmark tracking and magnetic tracking. In Rushmeier H. (ed) SIGGRAPH 1996 Conference Proceedings. Reading: Addison Wesley; 1996: 429-38.
• 12 Linnenbrügger NI. Automated Hybrid TACT volume reconstructions using digital image processing. Master’s Thesis, Department of Medical Informatics, Aachen University of Technology (RWTH), 52057 Aachen, Germany. E-mail. [e-mail] 2003
• 13 Canny JF. A computational approach to edge detection. IEEE T Pattern Anal 1986; 8: 679-98.
• 14 Hough PVC. A method and means for recognizing complex pattern. US Patent Application No. 3069654. 1962
• 15 Guil N, Zapata EL. Lower order circle and ellipse Hough transform. Pattern Recogn 1997; 30: 1729-44.