1. Julianna Ianni Meher Juttukonda David Morris Advisor: Dr. Jadrien Young, M.D.

2. What is Otologic Surgery? Surgery of the ear Mastoidectomy Mastoid air-filled spaces behind the ear Uses to remove cells from the mastoid to treat anti-biotic resistant infections in the region to insert a cochlear implant 30,000 to 60,000 performed annually in the U.S. [1]

3. Anatomy of the Ear

4. Mastoidectomy Clip

5. Objectives To find and attach an ultrasound transducer to an otologic surgical drill. To calculate the thickness of the mastoid bone using US To shut off the drill when the mastoid bone has been drilled or provide the surgeon with enough information to stop at the correct distance.

6. Why Ultrasound? CategoryCT - MethodUltrasound SafetyIonizing RadiationNo Ionizing Radiation Real-time Data TimeDrilling PlatformNot necessary InvasivenessInvasiveNon-invasive

7. Past Work Studied ultrasound equipment in order to determine the most effective way to produce accurate images Researched the best transducer frequency for imaging that region of the skull Developed the website Observed use of otologic drills & identify design constraints Identified potential design obstacles Generated design ideas concerning mechanism of attachment Restructured design goals focusing more on finding an ultrasound transducer compatible with an otologic drill. Performed some proof of concept tests for ultrasound depth measurements through bone.

8. Solidworks Prototype Side View Top View Bottom View

9. The Prototype The ultrasound transducer is placed so that it allows for the surgeon to quickly move the transducer into place to perform quick ultrasound scans. When not in use the transducer can be moved back out of the way and will allow the surgeon to quickly return to work. This set up allows for the surgeon to work quickly and prevents them from wasting a lot of time during surgery while also adding a safer means of cutting through the bones.

10. Model of Mastoid Bone -> Acrylic Speed of Sound = 2750 m/s [4] Soft Tissue -> Gel Speed of Sound ~ 1540 m/s

11. Analysis of Simulation

12. Results of simulation (gradient plots matched well w/ built-in edge detection) Worked really well with 1 layer of acrylic: Actual thickness= 2.03mm Measured thickness= 2.23mm w/o tissue & 2.35mm w/tissue For 4MHz: 2.13mm & 2.23mm respectively Want accuracy w/in 1mm

13. Multiple layers of acrylic? Harder to read Multiple peaks (including ones at the correct thickness) Not as distinct from noise Able to discern correct peaks knowing thickness, but can’t back them out just from data Most likely due to small air-pockets between layers of acrylic caused more echoes & attenuation @ ea. intersection

14. Multiple layers Depth(cm) y-gradient amplitude Example with 2 layers of acrylic (total thickness= 4.06mm) w/tissue layer 8.89MHz

15. Statistics No.Layersf (MHz)TissueThickness(cm) error(mm) % Error Layer 1Layer 2Layer 1Layer 2Layer 1Layer 2 118.89N0.22750.24311.96 218.89Y0.23980.36618.01 314N0.21640.1326.50 414Y0.22720.2411.81 528.89N0.20230.4298-0.0090.234-0.445.76 628.89Y0.23980.45430.3660.47918.0111.79 724N0.20230.4298-0.0090.234-0.445.76 824Y0.23940.42830.3620.21917.815.39 Actual1st Layer0.2032cm Thickness2nd Layer0.4064cm Tissue0.2cm

16. Future Work Getting transducers in & testing (high frequency and low frequency) building prototype & attachment for drill calibrating/signal processing and analysis

17. References 1. French, LC et al. “An estimate of the number of mastoidectomy procedures performed annually in the United States”. Ear Nose Throat J. 2008 May; 87(5): 267-70. 2. Ear Anatomy: http://www.umm.edu/imagepages/1092.htm http://www.umm.edu/imagepages/1092.htm 3. Clement, GT et. Al. “Correlation of Ultrasound Phase with Physical Skull Properties”. Ultrasound in Medicine & Biology. 2002 May; 28(5): 617-624. 4. http://www.signal- processing.com/tech/us_data_plastic.htmhttp://www.signal- processing.com/tech/us_data_plastic.htm