Ultrasound based CT registration for Computer Assisted Orthopaedic Surgery (2003 - 2005)

Ultrasound sonography becomes more relevant in the context of future minimal invasive computer assisted orthopaedic surgery. For transcutaneous non invasive registration an A-Mode ultrasound features several advantages in comparison to the B-mode technology. Apart from low costs the A-Mode technique offers simple realization of real time processing. Further A-Mode ultrasound allows reliable detection of bone-tissue surfaces and eliminates the need for manual segmentation.

Fig 1. Ultrasound signal response (left)

and palpation with mechanicaly tracked ultrasound probe of epicondylus lateralis (right)


The first step is to perform a CT scan of the patients region of interest (ROI). After reconstructing a surface voxel model using the computer tomographic slices several matching techniques are applied to solve the registration problem. A paired point matching with at least three bone landmarks must be performed to calculate an initial transformation of the bone co-ordinate system relative to the co-ordinate system of the tracking instrument. To increase the accuracy of the registration a second matching technique must be applied. The ultrasound probe is used to transcutaneous palpate the surface of the bone. Based on the initially calculated spatial position of the bone an autopilot function is used to maintain a perpendicular alignment of the ultrasound beam relative to the palpated surface of the bone. These digitized bone points are used to undertake a surface based registration using the iterative closest point algorithm. To decrease the time of performance a KD-tree data structure with small bucket size is applied.

Fig 2. Surface matching of digitized bone points (yellow) to the surface computer voxel model (left before and right after the matching procedere)


To simulate the ultrasound parameters of soft tissue a gelatine model is used. After performing the final surface registration the averaged translation error was 0.55 mm. The averaged rotation error along the axial, sagittal and transversal axes was found to be lower then 0.6 °.


  • Heger, S., Portheine, F., Radermacher, K.: A-Mode Ultraschallreferenzierung in der Hüftendoprothetik. Zeitschrift f. Biomedizinische Technik, Band 46, Ergänzungsband 1, 2001, S. 58-59
  • Heger, St., Portheine, F., Ohnsorge, J., Radermacher, K.: Visuelle Benutzerführung zur Referenzierung auf Basis von A-Mode Ultraschall. Biomedizinische Technik, Band 47, Ergänzungsband 1,Teil1 2002, S. 61-64
  • Heger, S., de la Fuente, M, Ohnsorge, J.A.K., Radermacher, K. : Automatische Kalibrierung optisch geführter A-Mode Ultraschall basierter Referenzierung, Biomedizinische Technik, Band 48, Ergänzungsband 1, 2003, S. 114-115
  • S. Heger, F. Portheine, J.A. Ohnsorge, E. Schkommodau & K. Radermacher: User-Interactive Registration of Bone with A-Mode Ultrasound. IEEE Engineering in Medicine and Biology Magazine, 2005, 24(2), pp. 85-95
  • L. Fieten, S. Heger, L. Pasalic, M. Engelhardt, K. Schmieder & K. Radermacher: Registration of Cranial CT Images with A-Mode-Ultrasound Data Using the Random-ICP Algorithm - A Cadaver Study. Proceedings Biomedizinische Technik, 52 (Ergänzungsband, CD-ROM), 2007
  • L. Fieten, F. Portheine, R. Müller-Rath, K. Radermacher & S. Heger: Surface-Based Registration Using A-Mode Ultrasound for PAO. Proceedings Biomedizinische Technik, 52 (Ergänzungsband, CD-ROM), 2007
  • L. Fieten, S. Heger, L. Pasalic, M. Engelhardt, K. Schmieder & K. Radermacher: Fast and accurate registration of cranial CT images with A-mode ultrasound. Proceedings CARS (Suppl. 1), 3, 2008, pp. 275-276
  • S. Heger: Intraoperative Struktur- und Geometrieerfassung mittels A-Mode Ultraschall in der computerunterstützten Chirurgie. In: S. Leonhardt, K. Radermacher & T. Schmitz-Rode (ed.): 3, Aachener Beiträge zur Medizintechnik (ISBN 978-3-8322-7867-0), Shaker, 2009
  • L. Fieten, K. Radermacher, M. Kernenbach & S. Heger: Integration of Model-based Weighting into an ICP Variant to Account for Measurement Errors in Intra-operative A-Mode Ultrasound-based Registration. Proceedings of the 32nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2010, pp. 6264-6267
  • L. Fieten, I. Dupraz, K. Reising, P. Helwig, S. Heger, W. Blömer & K. Radermacher: Ultrasound-based registration of the pelvic coordinate system in the lateral position using symmetry for total hip replacement. Biomed Tech (Berl), 2012, 57(4), pp. 239-248
  • L. Fieten, K. Radermacher & S. Heger: An ICP variant with anisotropic weighting to accommodate measurement errors in A-Mode ultrasound-based registration. Biomed Tech (Berl), 2012, 57(4), pp. 249-260