Julianna Ianni
Meher Juttukonda
David Morris
Advisor: Dr. Jadrien Young, M.D.
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]
Anatomy of the Ear
Mastoidectomy Clip
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.
Why Ultrasound?
Category
CT - Method
Ultrasound
Safety
Ionizing Radiation
No Ionizing Radiation
Real-time Data
Time
Drilling Platform
Not necessary
Invasiveness
Invasive
Non-invasive
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.
Solidworks Prototype
Side View
Top View
Bottom View
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.
Model of Mastoid
 Bone -> Acrylic
 Speed of Sound = 2750 m/s [4]
 Soft Tissue -> Gel
 Speed of Sound ~ 1540 m/s
Analysis of Simulation
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
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
Multiple layers
Y gradient
20
y-gradient amplitude
15
10
5
0
-5
-10
-15
-20
1
2
3
Depth(cm)
4
•
•
•
•
Example with 2 layers of acrylic
(total thickness= 4.06mm)
w/tissue layer
8.89MHz
5
6
7
Statistics
No.
Layers
f (MHz)
Tissue
Thickness(cm)
Thickness(cm)
error(mm)
error(mm)
Layer 1
Layer 2
Layer 1
Layer 2
% Error
Layer 1
% Error
Layer 2
1
1
8.89
N
0.2275
0.243
11.96
2
1
8.89
Y
0.2398
0.366
18.01
3
1
4
N
0.2164
0.132
6.50
4
1
4
Y
0.2272
0.24
11.81
5
2
8.89
N
0.2023
0.4298
-0.009
0.234
-0.44
5.76
6
2
8.89
Y
0.2398
0.4543
0.366
0.479
18.01
11.79
7
2
4
N
0.2023
0.4298
-0.009
0.234
-0.44
5.76
8
2
4
Y
0.2394
0.4283
0.362
0.219
17.81
5.39
Actual
1st Layer
0.2032 cm
Thickness
2nd Layer
0.4064 cm
Tissue
0.2 cm
Future Work
• Getting transducers in & testing (high frequency and
low frequency)
• building prototype & attachment for drill
• calibrating/signal processing and analysis
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
 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.signalprocessing.com/tech/us_data_plastic.htm