1 Image Overlay Guidance for Needle Insertion in CT Scanner Gabor Fichtinger*, Member, IEEE, Anton Deguet, Ken Masamune, Emese Balogh, Gregory S. Fischer, Member, IEEE, Herve Mathieu, Russell H. Taylor, Fellow, IEEE, S. James Zinreich, and Laura M. Fayad : : Date:2010/05/04 2 Outline Introduction and Background System concept CT image overlay device System integration Workflow Calibration Experiments and Results Discussion 3 Introduction and Background Numerous studies have demonstrated the potential efficacy of computed tomography (CT)-guided This frequently results in faulty needle placement attempts, especially in the case of a deep lesion adjacent to vital structures 4 The recent appearance of real-time CT fluoroscopy has brought significant improvement to needle insertion procedures Presently no technological in a simple, accurate, and inexpensive manner, without imparting additional radiation 5 System concept 6 Acquire a CT slice, flip it horizontally, adjust its magnification, and then render it on the display 7 The system creates the impression as if the CT image was floating inside the body in the correct pose and magnification Needle placement procedures, after the entry point is selected, three degrees-of-freedom (dof) motion of the needle needs to be controlled 8 Physician uses the overlay image to control the in-plane insertion angle (first dof) In the axial plane marked by the gantrys inner laser light (second dof) The insertion depth (third dof) 9 2-D image overlay are numerous in comparison to other virtual reality or display augmentation methods reviewed earlier 2-D image overlay provides optically stable image it requires only a simple alignment that does not need to be repeated for each patient 10 The main added benefit of the image overlay is making preinsertion CT images available for intraprocedural guidance 11 CT image overlay device Built two basic prototypes of the CT image overlay device for preclinical evaluation on phantoms and human cadavers Verified that the overlay device did not interfere with the laser lights of the scanner 12 First prototype of the image overlay system, the reflection image is in the inner axial laser plane of the scanner. 13 System integration Workflow A single CT slice is acquired with the fiducials in place and transferred in DICOM format to the planning and control software implemented on a stand-alone computer The CT window/level parameters can be interactively adjusted 14 The computer marks the target and entry points Especially in applications when the target anatomy is prone to motion due to respiration or mechanical force 15 Calibration Fabricated a calibration phantom containing a base board and a perpendicular fiducial board 16 CT image and display image pixel size Then the scale factors in x and y directions are calculated 17 The in-plane scaling between the CT and display image vectors If the pixel size is identical in x and y directions in both the CT and display, then the scale factors are equal 18 Calculate the required translation p to align the selected point Translate all CT image points 19 The center of rotation is the point selected previously for translation Rotate all CT points by the calculated amount about the chosen center of rotation 20 21 Experiments and Results Head phantom Implanted a honeydew melon with multiple 1.5-mmdiameter metal pellets serving as targets Body phantoms The overlay device, mounted in the inner laser plane of the scanner 22 Cadaver experiments Spinal nerve blocks and facet joint injections 23 Shoulder and hip arthrographies 24 Pilot Needle Insertion for Musculoskeletal Biopsy 25 Discussion This does not cause time delay, because the physician needs time to enter the scanner room anyway Needle placement experiments with both phantoms and cadavers were clinically successful and confirmed in post-insertion CT imaging