Phantom Simulation of Liver Motion During Normal Breathing

1
Phantom Simulation of Liver Motion During Normal
Breathing Ian Dallemeyer1, Tuta Guerra1, Ian
Henderlong1 Advisor Dr. Robert Galloway1 1
Department of Biomedical Engineering, Vanderbilt
University Nashville, TN
Results/Testing
Abstract Image-guided liver surgery is a
minimally invasive therapy to treat primary and
metastatic liver cancer with little damage to
healthy tissue. This design project focuses on
creating a phantom simulation of liver motion
during normal breathing in order to provide an
accurate, reusable device to practice and perfect
image guided-liver surgery techniques. This
model consists of two different components a
cart design with base and vehicle that support
the silicon phantom liver and a circuit design
which produces the cyclic power output. Muscle
Wire, which contracts and relaxes when heated,
connects the two components and creates the
simulated liver motion during normal breathing.
The model successfully generates comparable
displacement and frequency, with minimal
difference in regard to motion of an actual human
liver.
Design Specifications
-1-D Linear Motion (cranial caudal
direction) -10.8 2.5 mm (Average Total Liver
Motion) - Breath Frequency .11 Hz
(1 breath/9sec) - Measurements
made with Optotrak 3220
Introduction The American Cancer Society
estimates 15,420 people will die of liver cancer
in the U.S. during 2005. This cancer is about 10
times more common in developing counties in East
Asia, Africa, and Asia than in the U.S and in
many of these countries it is the most common
type of cancer.
With the length of wire used (30 cm), the average
displacement of the phantom was 10.43 0.535 mm.
Over an 8-9 second interval, our phantom moved
10 mm in about half the cycle time or 4-5
seconds, and returned to rest in about the same
amount of time. A plot of the cart motion vs.
displacement is shown above. A plot of the cart
motion vs. displacement is shown above and is
very comparable to the ATLM data recorded by
Optotrak 3220.
Current therapies for liver cancer are incredibly
invasive. Often cancer is large, is found in
many different parts of the liver, or has spread
beyond the liver so complete removal of most
liver cancers is not possible. Image-guided
liver surgery offers the possibility of a more
effective therapy with less side effects. Image
guided surgery uses tomographic imaging
techniques such as CT, MR, and PET to create a
registered image that define the spatial extent,
location and structure of the diseased area and
the
Methods and Materials Cart Design - Plywood for
base, cart, track - Oak for spring recoil
system - 22 3/8 zinc screws - 4 1 hooks
-2 extension springs k 9 x 106 N/m - 4 1
diameter plastic wheels Circuit Design
Conclusion/Future Work The ATLM and frequency is
accurately reproduced by the phantom model. The
waveform of the documented human liver motion is
slightly different than the results produced by
our phantom model. The most important function of
the phantom model is the movement of the liver
being accurate with the measured average total
liver motion. The measurements made in the body
show an enormous amount of error, nearly 20
variance of the average total liver motion. The
muscle wire used does not produce that type of
error and therefore cannot accurately simulate
the wide range of variance to the millimeter
necessary for the simulation. Therefore, a
different type of linear actuator may be more
sufficient to reproduce the variance needed in
simulating liver motion due to breathing. Material
s used would be the area that could most
drastically effect the accuracy and precision of
this model. This being the first prototype for a
phantom liver model, many of the materials are
crude and are designed for use on a much larger
scale, in particular the wheels used on the cart.
Also of note, the order in which parts are
assembled has an effect on the precision of
movement, particularly in the track system.
References - Herline AJ, Stefansic JD, Debelak
JP, Hartmann SL, Wright Pinson C, Galloway RL,
Chapman WC. Image Guided Surgery Preliminary
Feasibility Studies of Frameless Stereotactic
Liver Surgery. June 1999 Archives of Surgery
134644-650 - Korin HW, Ehman RL, Riedere SJ,
Felmlee JP, Grimm RC.Respiratory kinematics of
the upper abdominal organs A quantitative
study. Magnetic Resonance Medicine 199223172 -
Nawaratne, Sumith Fabiny, Robert Brien, Joanne
E. Zalcberg, John Cosolo, Walter Whan, Andrew
Morgan, Denis J. Accuracy of Volume Measurement
Using Helical CT. Journal of Computer Assisted
Tomography. 21(3)481-486, May/June 1997. -
Sarfaraz M, Wu X, Lodge MA, Yu CX. Automatic
CT-SPECT registration of livers treated with
radioactive microspeheres. Physics in Medicine
and Biology. Vol 49, May 4, 2004.
location, function and topology of the normal
anatomy about the disease areas. Using these
images as maps, surgeons can effectively guide
the delivery of therapy in space and time to
localized regions of the liver. These therapies
include radio-frequency ablation,
chemoembolization, and other localized minimally
invasive therapies. Currently, porcine livers,
whose structure most closely resembles that of
humans, are used to simulate liver surgery.
However, the cost and incompatibility to humans
in terms of structure and motion render this
model insufficient in providing an accurate and
affordable simulator. Therefore, it is necessary
to develop a phantom simulation of liver motion
during normal breathing using an anatomically
correct phantom.
Market Potential -ACS estimates 17,550 new cases
of primary liver cancer in U.S. 200,000 new
cases of metastatic liver -International Market
250,000 cases in China most frequent cancer in
developing countries of East Asia, Africa and
Asia -Estimated market for IGLS is 10x greater
than current IGNS market -IGLS Market
3.0-7.5 billion -Porcine Liver costs
1,000-2,000. Phantom model 150-200
Muscle Wire - Flexinol 150 LT -
Nitinol Shape Memory Alloy - Resistance 50O/m
- Diameter 150 µm - Activation Current 400mA