Technical Issues of Image Guided Surgery

Transcription

1 Technical Issues of Image Guided Surgery Digital Image Processing Laboratory, Center for Biomedical Engineering and Physics Medical University Vienna

2 Image Guided CMF Surgery An incomplete list of systems... ARTMA Virtual Patient RoboDent System DenX IGI System Drill Guides (Materialise, T. Fortin et al.) Modification of commercial systems like the BrainLAB suite or the Medtronic TREON... and VISIT

3 Reviving old VHS Tapes: VISIT in action et al., IEEE Trans Med Imaging. 19(6): , 2000 et al., Clin Oral Implants Res. 12(1):69 78, 2001 F. Watzinger et al., Plast Reconstr Surg. 107(3): , 2001 A. Wagner et al., Clin Oral Implants Res. 14(3): , 2003

4 Challenges from a technical point of view Imaging CT protocols & handling of artefacts Patient to image registration Image processing issues visualization & segmentation Hardware for image guided CMF surgery Workflow optimization What's about to come? Non technical challenges...

5 Imaging CT is the modality of choice for dental and CMF surgery Streak artefacts stem from the reconstruction process and are difficult to avoid or to be removed Pantomography is strongly dependent on patient positioning due to the strong perspective and the tomographic distortion of the image CBCT introduces other artefacts such as truncation and ring artefacts

6 Artefacts in CBCT Truncation and ring artefacts are common...

7 Quantitative CT Homolka P, Beer A, Birkfellner W et al. Radiology, 224(1): , (2002)

8 Planning in VISIT Planning of implant channels based on available bone volume and density is rather straightforward For extraoral implants, a more sophisticated interface is necessary

9 Tracking & Registration a Link to the Real World Registration: Finding a transformation between the coordinate system of a volume image and the real world Tracking: Maintaining that registration by measuring motion in 3D by optical tracking electromagnetic probe alternative techniques et al., Med Phys 25(11): ,1998 et al., IEEE Trans Med Imaging. 17(5): , 1998 J. Hummel et al., Med Phys 29(10): , 2002

10 Key issues in Tracking Accuracy and resolution: Optical trackers are rather accurate and still superior to EM probes Reliability: A free line of sight for an optical tracker always be maintained Handling: Trackers are cumbersome in general; passive systems have a higher acceptance rate than active (=wired) systems, but are less robust. Sterilizability: Autoclavation of electronics is difficult, ETO is expensive and time consuming

11 Patient to Image Registration Point to point registration (Horn) using at least three markers and a point probe error 0.7 +/ 0.15 mm Birkfellner W, Solar P, Gahleitner A et al, Clin Oral Implants Res 12(1):69 78, (2001)

12 Some experiences Minimally invasive insertion of titanium microscrews is feasible; the markers stay stable for several weeks Increasing the number of markers beyond 3 screws does not influence registration accuracy Exact localisation of screwhead centroids is necessary Mobility of mucosa in atrophic patients caused inaccuracies when using splint type solutions, even if residual dentition is available

13 Image Processing: Segmentation Segmentation is not exact Identification of surfaces depends on algorithms used

14 Alternative techniques Surface registration: Highly dependent on the quality of surface segmentation and the presence of outliers Surface scanning by laser ranging is hampered by the small visible area of the mucosa Stab incisions are by Tactile Technologies, IL cumbersome, but give good results Schicho K, Seemann R, Cohen V et al. J Clin Periodontol. 34(11):991 7, (2007)

15 Splint techniques by DMFR, from Eggers G, Kress B, Rohde S, Mühling J. Dentomaxillofac Radiol. 38(1):28 33, (2009) Problematic in completely edentulous patients Residual elasticity of 2 component molding materials is recognizable Segmentation of molding material and mucosa sometimes difficult

16 Surface Scanning Result from the Medtronic FAZER surface digitizer from Schicho K, Figl M, Seemann R et al. J Neurosurg, 106(4):704 9, (2007) Colchester AC, Zhao J, Holton Tainter KS et al. Med Image Anal, 1(1):73 90, (1996) Has a long history in frameless stereotaxy Complicated for fully intraoral interventions

17 Tracking technologies for CMF & oral surgery 32 implants, 5 patients after tumor resection and primary recon struction Accuracy: top 1.0 +/ 0.5 mm bottom 1.3 +/ 0.9 mm Wagner A, Wanschitz F, Birkfellner W et al. Clin Oral Implants Res. 14(3):340 8, (2003)

18 Challenges in tool design Sterilizable electronics are West JB, Maurer CR Jr. IEEE Trans Med Imaging. 23(5):533 45, (2004) cumbersome, autoclavation is difficult. Passive markers somewhat solve the problem and are handy, but provide less accurate results when being conatminated with blood Tool geometry (and size) is crucial

19 An early academic effort Hybrid Tracking Birkfellner W, Watzinger F, Wanschitz F et al. IEEE Trans Med Imaging. 17(5):737 42, (1998) Combination of electromagnetic and optical sensors to overcome the drawbacks of both technologies

20 Looking back Implant insertion 2000

21 Implant insertion after hemimaxillectomy Sealing of the naso pharynx with an obturator prosthesis after radical resection of squamous cell carcinoma

22 Restoration after ablative tumor resection Surgical removal of an osteo sarcoma in the mandible Implant insertion in a scapula flap after recon struction Wagner A, Wanschitz F, Birkfellner W et al. Clin Oral Implants Res. 14(3):340 8, (2003)

23 Minimally invasive implant insertion Comparison of VISIT and the Medtronic TREON system. Accuracy ranges from 0.6 +/ 0.5 to 1.0 +/ 0.5 mm for both Wittwer G, Adeyemo WL, Schicho systems K et al.int J Oral Maxillofac Implants. 22(5):785 90, (2007)

24 Medical Augmented Reality et al., IEEE Trans Med Imaging. 21(8): , 2002 F. Wanschitz et al., Clin Oral Implants Res. 13(6): , 2002 et al., Phys Med Biol. 48(3):N49 57, 2003 M. Figl et al., IEEE Trans Med Imaging. 24(11): , 2005

25 Technology of image injection Birkfellner W, Figl M, Huber K et al. IEEE Trans Med Imaging.21(8):991 7, (2002)

26 Linking navigation and augmented reality

27 Conclusions & Outlook Research directions for Computer Aided Surgery in the CMF area include Technical developments concerning TRE Developments for optimized workflow and cost including socioeconomic research Evaluation of suitable clinical applications

28 Acknowledgments Dept. of Cranio Maxillofacial Surgery Dental School Vienna Dept. of Diagnostic Radiology My Colleagues at the CBMTP and R. Schulze and the IADMFR for inviting me!