1. PSU Hershey Medical Center Team 3: Final Report
2 May 2016
Vikram Eswar
Daniel Johnson
Christopher Pfeiffer­Kelly
Andrew Simonson
Michael Tramontozzi
Yes​­ Intellectual Property Rights Agreement
No​­ Non­Disclosure Agreement
Executive Summary
The ​purpose of this capstone project is to design an endoscopic ultrasound guided radiofrequency
ablation probe with a detachable fiducial for the treatment of pancreatic cancer. The device uses two
forms of treatment: radiofrequency ablation (RFA) and stereotactic body radiation therapy (SBRT). RFA
is a treatment that works by using a rapidly changing electric field to excite surrounding ions resulting in
the heating and destruction of the malignant tissue. The second treatment, SBRT, uses a targeting fiducial
to deliver high doses of radiation to a tumor. The device developed for this project combines both of these
techniques by using a detachable segment of the RFA probe to act as the fiducial to be targeted for the
SBRT treatment after it is left in the body. All designs were based on current ablation probes on the
market and use an expansion technique to lodge within the tumor. The best two prototype ideas, the coil
and reverse peacock, will be micromachined at 2x scale and are described in detail with design
descriptions and exact dimensions provided. Made of stainless steel and nitinol, these devices will first be
tested with egg whites and gel matrices to determine heating patterns and deployment behaviors,
respectively. Further ex­vivo testing will be conducted by the research team at Hershey Medical Center in
various biological samples following the completion of our capstone. Our group has estimated
expenditures of $800 for the project that will be used for materials, manufacturing, and transportation.
The final deliverables for this capstone will include two working prototypes that can perform successful
tissue penetration, tumor ablation, and fiducial deployment.

2.
Table of Contents
1.0 Introduction: 2
1.1 Initial Problem Statement 2
1.2 Objectives 3
2.0 Customer Needs Assessment 4
2.1 Gathering Customer Needs 4
2.2 Weighting of Customer Needs 4
3.0 External Search 6
3.1 Patents 6
3.2 Existing Products 11
4.0 Engineering Specifications 13
4.1 Establishing Target Specifications 13
4.2 Relating Specifications to Customer Needs 15
5.0 Concept Generation and Selection 16
5.1 Problem Clarification 16
5.2 Concept Generation 16
5.3 Concept Selection 19
6.0 System Level Design 21
7.0 Special Topics 23
7.1 Preliminary Economic Analysis 23
7.2 Project Management 23
7.3 Risk Plan and Safety 24
7.4 Ethics Statement 25
7.5 Environmental Statement 26
7.6 Regulatory Considerations 26
7.7 Communication and Coordination with Project Sponsor 26
8.0 Detailed Design 27
8.1 Manufacturing Process Plan 28
8.2 Analysis 32
8.3 Material and Material Selection Process 36
8.4 Component and Component Selection Process 37
8.5 CAD Drawings 39
8.6 Test Procedure 41
8.7 Economic Analysis: Budget and Vendor Purchase Information 42
9.0 Final Discussion 43
9.1 Construction Process 43
9.2 Test Results and Discussion 49
10.0 Conclusions and Recommendations 57
11.0 Self Assessment 58
11.1 Customer Needs Assessment 58
11.2 Global and Societal Needs Assessment 59
Works Cited 59
Appendix 62
1

3.
1.0 Introduction
Pancreatic cancer is the ninth most deadly type of cancer in women and fourth in men (Alteri,
2016). With roughly 53,000 diagnosed cases annually, the one year survival rate is a measly
29%, with only 7% of patients surviving five years or more (Alteri, 2016). This is due to the
difficulty in detecting the illness in its early stages, resulting in diagnoses when it is at Stage III
or worse. While chemotherapy is often used as a treatment option, it is often not aggressive
enough to completely remove the tumor, particularly when diagnosed at a late stage as pancreatic
cancer often is. Surgery is also often avoided, as patients cannot survive the procedure. Due to
the fact that the pancreas is located in close proximity to other important anatomical structures,
average age of patient, and average stage of diagnosis, surgery carries a 2% chance of death and
40% chance of serious complication. The procedure also delays chemotherapy treatments several
weeks before and after. For this reason, radiofrequency ablation (RFA) and stereotactic body
radiation therapy (SBRT) are strongly preferred and commonly performed. In the former
method, an electrode is connected to a radiofrequency generator which rapidly oscillates a
current causing rapid changes in the dipole of molecules in close proximity to the probe,
resulting in friction and heat production (Hong, 2012). Grounding pads on the thighs of the
patient collect the current over a large area, preventing high energy concentrations at the tip of
the electrode and subsequent charring (Hong, 2012). The current disperses in the body and the
large grounding pads prevent skin burns by preventing a single point for the energy to flow
through. The large pad, in essence, collects the current over a large enough area to prevent the
high energy concentration found at the tip of the electrode in the tumor. The latter treatment,
SBRT, uses radiopaque markers that can be visualized under a wide variety of modalities such as
CT or MRI (SBRT, 2015). Often, they are composed of biocompatible materials, primarily
metals, such as titanium, gold, or palladium. Physicians use these markers to direct bursts of
radiation, typically X­rays, to kill tumors (SBRT, 2015). Interestingly enough, markers are
permanently left inside the tumor body. This is due to the short life expectancy of patients and
the bioinert properties of the materials. Independently, these methods offer some therapeutic
benefit; however, little headway has been made in combining them. It is hoped that using
ablative techniques in conjunction with post­operative radiotherapy will result in permanent
destruction of the tumor and a means to eliminate any resurging malignancies.
1.1 Initial Problem Statement
Treating pancreatic cancer, especially in older patients who cannot undergo surgery, is a pressing
issue in the medical field that needs to be addressed. Because many of the patients are incapable
of surviving a surgery to remove the tumor, the pancreas has to be accessed by some other less
2

4.
invasive technique. Often, the best method for accessing the pancreas non­invasively is via an
endoscopic procedure where a needle pierces the stomach lining gaining access to the tumor.
There are several methods currently available for the treatment once it has been reached which
include RFA and SBRT. However, even though these techniques do work, treatment of any form
of cancer is most effective when multiple treatment methods are used. This strategy is
particularly appealing with regard to pancreatic cancer because of the aggressive nature and late
stage diagnosis. For this project, the initial problem is to improve the effectiveness of cancer
treatment by combining these two techniques into one novel device.
1.2 Objectives
The ultimate objective of this device is to develop an endoscopic procedure for delivering
ablation and radiation therapy treatment to patients with pancreatic tumors. The device must fit
inside of a generic endoscope and provide RFA treatment to the patient. After RFA is completed,
a fiducial marker should remain in the patient to be used as a marker for SBRT. The design will
focus on two aspects of the device: the geometry/material makeup and the detachable fiducial
component that remains in the body after RFA. Physicians suggest that a more spherical ablation
zone may provide more precise treatment to the patient. The material composition of the device
must also be biocompatible and constructed such that it is conductive. The fiducial, as it will be
referenced throughout the report, should remain in contact with the leads that provide the
radiofrequency and conduct current throughout the RFA process. Upon completion of the
ablation, the fiducial will separate from the rest of the probe and remain in the body providing
markers that can be visualized under ultrasound for SBRT.
This project is not intended to completely redesign current endoscopes that are available to and
commonly used by physicians. Rather, the goal is to design a product that will combine the
existing treatments and fit into current products on the market. This should allow physicians to
use familiar techniques, significantly increasing the product’s popularity and acceptance. The
device will be used explicitly for endoscopic procedures, specifically for treatment of cancers
and abnormal growths in close proximity to the stomach and upper gastrointestinal tract.
3

5.
2.0 Customer Needs Assessment
2.1 Gathering Customer Input
The customers for the two prototype designs being created are the project sponsor, Dr. Moyer, as
well as PhD candidate student, Brad Hanks. Customer needs for this project were gathered by
examining past literature of the topics regarding endoscopic surgery, RFA probes, and SBRT
techniques. The majority of our customer needs specifications, however, came from
question­answer sessions and an extensive literature review. Together with or sponsor and
Brad’s input, criteria were generated and their appropriate rankings discussed in terms of the
necessity of the various objectives of the project.
2.2 Weighting of Customer Needs
Our project team, in collaboration with our sponsor, came up with nine customer needs that the
prototype probes need to address. The needs are as follows:
1. Detaches every time
2. Forms a spherical ablation zone
3. Low­cost
4. Is easily manufactured
5. Is flexible enough to be used with a 19 gauge needle
6. Is compatible with current endoscopes
7. Has an immobile fiducial after deployment
8. Is built to a testable scale
9. Has both ends of the device visible under ultrasound
The weighting of each of these customer needs is very important on the design side as it allows
the team to prioritize what is absolutely necessary for the prototypes to function as needed while
devoting less time to less important metrics. The values were calculated by comparing across the
rows where if the number is larger than 1 the row’s metric is more important to the customer
than what it is being compared to. If it is less than 1, then it is not as important of a need as what
it is being compared with in the particular column. The rows are added up and then divided by
the total number of points from all the rows in order to normalize the data. All of the weights add
up to 1, with needs that have a larger value being more important to the customer. This
methodology is depicted in Table 1. The values for each of the metrics were determined after
consulting with literature and taking insight from Dr. Moyer and Brad Hanks. Detaching every
time was pushed by Dr. Moyer as the most important aspect of the device as it is what makes this
combined RFA and SBRT technique novel. The cost of the device is the least important need to
be met because this concept would still be many times cheaper than recurring chemotherapy or
4

6.
radiation treatments, as patients would have to go through several procedures and there is an
added cost to surgery.
Table 1. ​AHP Pairwise Comparison Chart to Determine Weighting for Prototype Customer
Needs
5

7.
3.0 External Search
To determine prior art, a patent search and market assessment were conducted. The goal of the
search was not only to garner a better understanding of how the components in an RFA probe
and fiducial markers interacted, but to find products outside of the medical industry that use
similar designs. There are currently no patents in the United States for an endoscopic ablation
probe with a fiducial component; however, the art vs. function matrix, Table 2, shows patented
designs that possess some of these characteristics. The market analysis yielded similar results,
with no commercial probes that match the design criteria; however, it was helpful in tailoring the
design of the fiducial component and possible probe geometries.
Table 2. ​Art vs. function matrix of RF probe and fiducial markers
3.1 Patents
Radiofrequency Ablation
RFA builds on pre­existing technologies implemented in a wide range of devices. While the
original use of electromagnetic waves was limited to the transmittance of information, further
research, spearheaded by the Raytheon Manufacturing Company, demonstrated a wide range of
applications previously unknown. The earliest precursor can be observed with the original patent
for the microwave oven, succinctly titled “Method of treating foodstuffs”, which relied on the
use of electromagnetic energy to dielectrically heat food (Spencer, 1950). The design harnessed
microwaves within a specific range of frequencies to induce thermal heating by rapidly shifting
the dipoles of molecules (Spencer, 1950). While there are obvious differences between
microwaves and RFA probes, specifically the nature of the wave used and the delivery
6

8.
mechanism, the essential design principle of heating through induced vibrations is the same. A
further elaboration on this concept was recently observed with an apparatus that used RF energy
to pasteurize the yolk of an egg through heating while preventing the denaturation of the outer
albumin (Geveke et al., 2015). The strategic placement of the electrode and grounding leads
along with the intermittent rotation of the egg allowed the targeted delivery of energy to heat the
inner yolk rather than its entirety, as observed in a microwave. The patented design achieves a
temperature of 67 °C within, a similar target in ablation therapies. These innovations highlight
the use of radio waves beyond the medical industry.
The ability to heat certain, specific areas within a target has numerous applications within the
healthcare field, specifically, the removal of malignancies or growths. One of the earliest
advances was the creation of an electrosurgical knife that, when coupled with a radiofrequency
generator, caused tissue destruction within the immediate vicinity of the blade (Doss et al.,
1979). By placing the two RF electrodes on either side of a tungsten­coated scalpel, less power
was required for heating, reducing harmful side effects of the ablation procedure such as burns
(Doss et al., 1979). While the device was useful in cutting and cauterizing vasculature, the
ablation of tumors needed probes capable of producing a larger heating zone. One of the most
common ablation probes designed is a simple, conductive electrode that can be moved axially
along a catheter to deliver electromagnetic energy at the tip, as seen by 6 in Figure 1. An
insulated sleeve (3) around the probe not only protects the rest of the apparatus during heating,
but allows for its facile removal at the end of the procedure (Morgan and Cunningham, 2003).
Figure 1.​ Simple ablation probe with singular tip
Recent developments have elaborated on this treatment method with multi­pronged probes that
are not only able to destroy larger tumors, but maintain a spherical heated region with minimal
destruction of healthy tissues. This can be seen with a design that has three; straight, isolated
probes with a controller that switches electrical power between them, allowing greater control of
the ablation region (Lee et al., 2009). The device has the benefit of being able to be used in a
wide range of anatomical settings without a need for a change in probe geometry (Lee et al.,
2009). Nevertheless, many patents have improved on the probe design in an effort to better
7

9.
control the ablation zone. A recent innovation uses the pressure generated from inserting an RFA
probe to eject electrode tines at an angle through the slits of a cannula, as seen by number 104 in
Figure 2 (Young et al., 2015). This allows the formation of spherical heated areas around each
electrode tip (Young et al., 2015).
Figure 2.​ Multi­pronged ablation probe with angled tines
Upon completion of the procedure, the array can be retracted, returning the probes to the needle
and sealing the exit points, number 112. Another design developed by Boston Scientific
employed a series of stainless­steel electrode tines that projected radially outward from a cannula
(Pearson et al., 2014). Additionally, the presence of a conical, distal tip not only allowed for the
facile penetration of tissues, but served as a marker under ultrasound (Pearson et al., 2014). The
everting, jellyfish­like shape of the tines, number 30 in Figure 3, are a source of inspiration for
many of the designs shown here as they not only cover an area consistent with larger pancreatic
tumors but diverge enough to easily get entangled within tissues.
Figure 3​. Multi­pronged ablation probe with everting shape
8

10.
While there are no pre­existing patents in the United States for ablation techniques done
endoscopically, they do exist in China. In this method, the RF electrode is inserted through the
mouth and guided to the target tumor through ultrasound imaging (Guoxin et al., 2010). Upon
reaching the destination, a needle can be extended axially to penetrate through the stomach or
digestive lining and ablate the necessary tissues. Overall, the use of RFA in American clinical
settings is very common; however, its restriction to laparoscopic procedures leaves applications
in endoscopy open for study.
Fiducials
The use of fiducial markers as signposts in the body has been instrumental in making
chemotherapy and radiation therapy more effective. A patent recently obtained by Boston
Scientific combines an RFA probe, which acts as a fiducial datum during ablation, with radiation
such as X­ray (Rioux, 2010). The electrode tines shown are the same as the Pearson et al. design,
but the exact number can be modified based on the physician’s preference. Another example,
with particularly relevant applications in neurosurgery and tumor removal, is a design involving
small divots attached to fiducial spheres that can be registered easily by CT or MRI scans, Figure
4 (Lee et al., 2006). While these can be imaged at any time, by unscrewing the spheres, a
calibration wand can be used in their stead to construct a 3D rendering of the patient’s internal
topography, assisting the physician with entry routes (Lee et al., 2006).
Figure 4​. Fiducial spheres
The use of radiopaque markers can also be seen with vascular surgery, specifically the
implantation of stents. A recent patent designed a longitudinal mesh plated with gold, platinum,
or silver that, when inserted into a patient’s artery, would be visible under X­ray or fluorescent
imaging (Lam et al., 1998). As with most markers, the coating was usually 0.0003 to 0.003
inches and encapsulated the entire outer surface (Lam et al., 1998). Another European
technology recently developed was a triangular marker, Figure 5, with lengths made of a
memory shaped nickel­titanium or iron­platinum alloy that could be deformed at room
9

11.
temperature but return to its natural shape within the body (Escarguel, 2015). X­ray visible
sections at the corners including gold, silver, platinum, tungsten, or palladium would then allow
stereotactic visualization of the patient (Escarguel, 2015).
Figure 5​. Triangular fiducial marker
Often, a simpler design is favored for imaging as can be seen with a barbell­shaped marker
which has readily visible bulbous ends under CT or MRI scans but an essentially transparent
center section (Whitmore and Jones, 2008). As the Escarguel and Whitmore and Jones designs
are so simplistic, they can be easily inserted via the cannula of a needle.
To date, fiducials are typically primarily delivered percutaneously. This can be observed with a
pending patent by Westerfield that ejects a number of markers a certain distance away from each
other (Westerfield and Rezac, 2015). The fiducials are loaded proximally in a cannula, and upon
being inserted, will fan out and lodge in the tissue (Westerfield and Rezac, 2015). A recent
endoscopically compatible product by Cook Medical, called the EchoTip Ultra HD
Endobronchial Ultrasound Needle comes preloaded with up to four golden fiducial cylinders
within the needle and can be easily pushed out by using a stylet (EchoTip, 2016). Additionally,
dimples around the outside of the needle allow easy visualization under ultrasound (EchoTip,
2016). As can be seen with all of the radiopaque markers mentioned here, few have been
designed to be inserted endoscopically, or used in the long term after ablation has taken place.
10

12.
3.2 Existing Products
Radiofrequency Ablation
While the market is flooded with RFA probes and fiducial markers, few combine the two
therapies. To date, there are few commercial products available in the United States that ablate
tissue and can be inserted endoscopically. In Europe, a recent product developed by EMcision
called the Habib™ acts as a monopolar catheter that is capable of cauterizing and coagulating
tissue (Habib, 2015). The device can be placed in the biopsy channel of an endoscope or
laparoscope and, with the guidance of ultrasound scanning, can access lesions in abdominal
organs (Habib, 2015). Additionally, its working length of 220 cm and compatibility with the
industry­standard 19 gauge needles have led to the probe’s widespread use in clinical settings
(Habib, 2015). However, sales have largely been limited to Europe as the product has not
received the necessary FDA approvals. While revolutionary, the Habib™ is largely removed
from the American market, leaving plenty of room for innovation. Within the US, Medtronic
recently developed the Barrx™ 360 Balloon Catheter for ablation of the Barrett’s epithelium in
the esophagus, as can be seen in Figure 6 (Covidien, 2013). In the design, the bipolar electrode
delivers RF energy circumferentially through a compliant balloon material, heating a 3 cm long
cylindrical region in the throat (Covidien, 2013). While it can be inserted endoscopically, the 85
cm length of the probe is too short for lesion removal deeper in the body or insertion through the
digestive lining.
Figure 6.​ Barrx​TM​
360 Balloon Catheter
11

13.
Many biotech companies have designed RF devices of their own due to the prevalence of
percutaneous ablation techniques in American health care. For instance, the 3.5 mm­diameter
SERFAS probes by Stryker are bipolar, eliminating the need for grounding pads (Stryker, 2015).
They are typically used in an arthroscopic setting, cauterizing tissues around the hip and knee
during orthopedic procedures. Similarly, Arthrex has designed a series of CoolCut™ ablators for
use in a wide array of clinical settings. Built straight or at a 45° angle, they have a short length of
around 10 cm, allowing greater physician control (CoolCut, 2013). Additionally, the probes are
able to be inserted through the cannula of standard 17 gauge needles and can function at lower
power settings, removing the need for grounding pads (CoolCut, 2013). Medtronic has also
developed an ablation system for spinal tumors, called OsteoCool™. This system relies on two
separate 20 mm probes inserted through the cannula of radiopaque needles. One is the typical RF
heating probe while the other circulates water to act as a cooling mechanism and expand the size
of the ablation zone (OsteoCool, 2016). The current design specifications for endoscopic
ablation probes can be seen in Table 3. While the current market contains many products for RF
ablation of soft tissues, they are typically not associated with the cauterization of inner organs
such as the pancreas.
Table 3.​ Benchmarking for two endoscopic ablation probes
Design Characteristic Habib EUS Barrx​TM
Length 220 cm 85 cm
Diameter 2.5 mm 18­31 mm
Ablation Geometry Spherical Cylindrical
Detachability None None
Fiducials
The development of fiducial markers is lucrative due to their ease of manufacture and role in
numerous surgical procedures. CIVCO offers dozens of devices that vary based on material,
modality, and location of implantation. The FusionCoil™ images equally well under CT and
MRI scans and is composed of an open spiral gold coil with a flexible metallic core (Fiducial,
2015). The delivery mechanism is simple with the coil pre­loaded in a cartridge and inserted in a
needle hub for injection. FlexiMarc G/T™ markers consist of a titanium rod with two;
biocompatible nodes at each end, visible under most modalities, as can be seen in Figure 7
(Fiducial, 2015). The fixed distance of 10 or 20 mm between radiopaque sections provides
spatial resolution for radiation therapies (Fiducial, 2015).
12

14.
Figure 7​. Barbel shaped fiducial markers
The most common design is golden cylinders roughly 3 mm long with a 1 mm diameter
(Fiducial, 2015). As with the previous markers, these can be pre­loaded in sterilized needles for
percutaneous delivery. For the CIVCO products, all of the golden sections have a knurled surface
which prevents migration whilst the marker is lodged in the patient. The advent of fiducials has
also lead to the growth of robotic surgeries, primarily CyberKnife®. First, golden seeds, such as
the previous CIVCO cylinders, are inserted around the entire tumor with about 2 cm spacing
between (CyberKnife, 2015). The patient is then subjected to highly precise bursts of radiation to
destroy only tumorigenic tissue. For this reason, it is important that the markers not only provide
an accurate map of the tumor geometry, but do not dislodge or move between sessions of
therapy. While the CyberKnife® is just one of many radiation therapies that rely on fiducial
markers, no current ablative procedures use this technology concurrently. The benchmarking for
commercial fiducial markers can be seen in Table 4.
Table 4.​ Benchmarking for CIVCO fiducial markers
Design Characteristic CIVCO Products
Length 3­20 mm
Diameter 0.8­1.6 mm
Material Gold
Modality CT, MRI, IGRT
Delivery Mechanism Percutaneous injection
4.0 Engineering Specifications
4.1 Establishing Target Specifications
The ablation probe is being designed to be used in a hospital setting for patients diagnosed with
pancreatic tumors. The customer for this device, therefore, is determined to be Dr. Moyer, who is
13

15.
the sponsor for the project and the physician who will be using the device, and graduate student
Brad Hanks. Both of these individuals​ ​were surveyed to determine target values and
specifications for the device to make it efficient and marketable.​ ​The relationship between these
specifications and the customer needs is outlined in Table 5.
Table 5. ​Ablation Probe Needs and Specifications for 3x Scale
Physician Needs Specifications
Fiducial detaches every time Detaches completely from device after 10­15
minutes of RFA
Visibility Markers qualitatively visible under
endoscopic ultrasound
Endoscopic Maximum device radius = 4.0 mm
Maximum device length = 4 feet
Spherical ablation zone Radius of 2­2.5 cm
Manufacturability Manufacturing time , 1 hour per device
Scale Maximum fiducial radius = 1.3 mm
Maximum fiducial length = 3 cm
Immobile after deployment Fiducial migrates < 5 mm
Cost Manufacturing cost < $1000
Flexibility Device does not kink when bent to radius = 2
inches
Safety No adverse bleeding, infection, or sepsis
Tumor is destroyed Probe heats to 50­60 degrees C
The device is in the concept feasibility phase of the design process. As a result of this, a number
of the specific specifications for the physician needs are preliminary. Once more product testing
has been performed, Table 5 will be updated with more accurate specifications.
14

16.
4.2 Relating Specifications to Customer Needs
A Needs­Metrics Matrix comparing the customer needs and specifications shown in Table 5 is
shown below in Table 6. Each customer need and expectation is given a quantitative value of a
1, 3, or 9. A ranking of a 9 means that the combination is the most critical to the overall design
goal, and a ranking of a 1 means that the combination is less critical to the overall design goal.
The totals from each column are calculated to determine which metrics are most critical. Table 6
shows that the most critical metric for the device is that the fiducial must separate 100% of the
time.
Table 6.​ A Needs­Metrics Matrix for the Ablation Probe
15

17.
5.0 Concept Generation and Selection
5.1 Problem Clarification
At a high­level, the device needs to be inserted into the patient endoscopically and use RFA to
ablate a pancreatic tumor. After the ablation process, a fiducial marker that is visible on
ultrasound must be left inside the patient once the endoscope is removed. A sub­function
diagram for the ablation probe is shown below in Figure 8.
Figure 8.​ Sub­function diagram of the ablation probe
5.2 Concept Generation
Concept generation was performed in a group setting with Brad and the rest of the core­team.
Brad informed the team that the majority of the project would focus on system level designs, and
that the general concepts that Dr. Moyer would use were already established.
There are a number of restraints for the device that limit the number of feasible concepts for the
project. As mentioned in the introduction, the device has two main design challenges. The first
challenge is designing the ablation probe itself. The probe must be comprised of certain
materials and have a specific geometry to meet the specifications. The second challenge is
16

18.
ensuring that the probe is detachable and can be left inside of the body for SBRT. A constraint
to these design challenges is that the device must fit inside of the working channel of an
endoscope. A needle is preferred to be used in order to pierce through the stomach wall and the
pancreas, and a 19 gauge needle is the maximum sized needle that can fit inside of the
endoscope.
The detachment mechanism for the probe is one area, however, in which concept generation was
used. Sketches for these can be seen in Section 6.0. The core­team brainstormed ideas for 30
minutes, and each member took one of the concepts to expand upon for the next meeting to
present to Brad. The first concept, which was recommended by Brad and Dr. Moyer, includes
using a male­female connection for the device. This concept relies on the fact that once the
device pierces the tumor, the tumor will provide enough friction and resistance to separate the
male­female connection, leaving the fiducial inside of the tumor.
A second concept considered included using a threaded screw and torsional motion to detach the
fiducial. This concept provides a sturdy mechanism in which the device could be deployed.
Although this concept would be robust, it was mentioned by Dr. Moyer that this concept is not
feasible as a result of torsional motion being nearly impossible within the endoscope. A third
concept discussed was using some type of biodegradable glue. In this manner, the heat
generated from the RFA probe would simultaneously melt the glue holding the fiducial in place.
The fiducial would then be separated at the end of RFA and left inside of the patient. A review
of biodegradable polymers showed that this concept may also not be feasible as such an adhesive
does not exist.
Due to the number of constraints, two high­level and feasible concepts were chosen to be
pursued for the delivery of the ablation probe. These concepts include a “detachment point”,
where one of the detachment mechanisms previously mentioned will be used. Figure 9 shows a
schematic of the first concept. This concept relies on the fact that the entire ablation probe moves
independently of the needle. A 19 gauge needle loaded with the device is inserted into the
endoscope. The needle is used to pierce the wall of the stomach and the pancreas. Once this is
performed, the device is then inserted into the tumor and the RFA process is begun. After the
RFA process is complete, a fiducial component at the axial end of the ablation probe is detached
and left inside of the pancreas. This fiducial contains markers that can be seen under ultrasound.
Not pictured in Figure 9 is the sheath that would be placed around the needle to ensure that the
endoscope and device are not damaged.
17

19.
Figure 9​. Schematic of Concept #1
Figure 10 shows a schematic of the second concept. This concept is similar to the first concept
but is different in that it relies on the fact that ablation probe and needle move together through
the endoscope. As opposed to the first concept in which the device was loaded into the 19 gauge
needle, this concept attached the device to the needle. The needle and ablation probe move as
one through the stomach wall and pancreas. The RFA process is completed inside of the
pancreas, and the fiducial component of the ablation probe at the axial end, which consists of the
tip of the needle and the device itself, is left inside of the pancreas. This fiducial contains
markers that can be seen under ultrasound. Not pictured in Figure 10 is the sheath that would be
placed around the needle to ensure that the endoscope and device are not damaged. A specific
prototype of concepts 1 and 2 are shown below in the System Level Design section.
18

20.
Figure 10.​ Schematic of Concept #2
5.3 Concept Selection
The team has decided to move forward with both concepts. In talking with Dr. Moyer and Brad,
neither of them have a preference between the two concepts. Currently the team has narrowed
down the number of system level designs to two: one of these designs features the first concept
and one of the designs features the second concept. Once testing is performed on the two
prototypes that the team is currently moving forward with, the team will have more insight into
how the selection criteria relate to each concept. For example, it is difficult to determine whether
or not the concept will detach every time without having tested it in some representative
medium.
Table 7 shows the current status of the concepts previously mentioned. The physician needs from
Table 5 were used to perform concept scoring. Each design concept was scored according to
Table 7 below. The total score was then calculated to determine which design concept best fits
the selection criteria. Concept #1 is represented by 1P and Concept #2 is represented by 2P.
19

21.
Table 7. ​Pugh Concept Scores
Concepts
1P 2P
Selection Criteria Weight Ranking Wgtd.
Score
Ranking Wgtd.
Score
Fiducial detaches
every time
0.22 4 0.88 3 0.66
Visibility 0.12 3 0.36 3 0.36
Endoscopic 0.11 5 0.55 4 0.44
Spherical ablation
zone
0.1 4 0.40 4 0.40
Manufacturability 0.1 3 0.30 5 0.50
Scale 0.06 3 0.18 5 0.30
Immobile after
deployment
0.06 4 0.24 5 0.30
Cost 0.02 3 0.06 3 0.06
Flexibility 0.08 5 0.40 4 0.32
Safety 0.03 5 0.15 3 0.15
Tumor is destroyed 0.1 4 0.4 4 0.4
Total Score 3.92 3.89
Rank 1 2
Relative Performance Rating
Much worse than reference 1
Worse than reference 2
Same as reference 3
Better than reference 4
Much better than reference 5
20

22.
Table 7 shows that the first design concept best fits the selection criteria. Discussions with Dr.
Moyer and Brad aided in providing the specific weights for each selection criteria. The fiducial
detachment was unanimously agreed to be most critical to the design and to Dr. Moyer’s
preference. Cost and biocompatibility, which are important factors in medical devices, are not as
large of a concern for this group. The projected cost of making this device is significantly less
than the alternative treatment option of chemo and radiation therapy. Biocompatibility is not a
large concern since the device will be embedded in non­living cells. The first concept provides a
more reliable detachment mechanism and is better suited for endoscopy since the device is inside
of a 19 gauge needle; however, due to this size the device may be difficult or more expensive to
manufacture on such a small scale. The second concept may provide slightly better ablation and
fiducial immobility due to the needle staying in the patient; however, this also poses a safety
concern.
6.0 System Level Design
The first prototype for the ablation probe, seen in Figure 11, shows a reverse peacock
deployment system for locking into the tumor. This design is meant to be inserted via cannula of
a needle. The tip punctures the tumor and is pushed into the required ablation region as seen fit
by the overseeing clinician. When RFA is ready to be performed, the doctor pulls back on the
cable attached to the end, which results in the fins being pushed outward into the tissue. The
entire component is conductive, so RFA can then be performed by the doctor. After the therapy
is complete, the doctor can give a hard pull on the cable causing the device to detach from the
male female mechanism at the end of the device. The frictional forces of the male female part
can be overcome by the peacock blades locked into the tissue. The cable attached to the female
part is then drawn out leaving the tip in the body to act as the fiducial for SBRT to be conducted
at a later time. The final prototype will have a diameter less than 1mm in order to fit into the
working channel of most common endoscopic devices. Initial prototypes will be built at 3x scale
and reduced in size based on ablation performance. The fiducial component of the deployment
mechanism is approximately 6mm​3​
. This dimension will be further constrained following heat
transfer testing of the ablation zone using gel with similar conductive properties to carcinogenic
tissue.
21

23.
Figure 11. ​Reverse Peacock Prototype
The second prototype, seen in Figure 12, for the ablation probe is based off of the thesis work by
Benjamin Kusiak whose rendering is below (Kusiak, 2014). A major difference between this
design and the first design is that the ablation probe is the end of the needle as opposed to
something that would be inserted through it. The device operates piercing the tissue as a normal
needle would and then having a coil made of heat­memory nitinol expand slowly into the tissue.
The expanding coil helps to create the spherical ablation zone required by the customer needs for
RFA. After the procedure when the doctor retracts the device, it pulls out at the end leaving the
entire spherical coil behind to act as the SBRT fiducial. The probe will have a diameter of 1 mm
and act as the end of a 19 gauge needle. The exact length will be determined with a variety of
deployment tests to find the optimal length for endoscopic release.
​Figure 12. ​Coil Prototype
22

24.
7.0 Special Topics
7.1 Preliminary Economic Analyses ­ Budget and Vendor Purchase
Information
Early prototype designs will be created using miscellaneous crafting materials. These materials
will include pipe cleaners, glue, paper, etc. Advanced prototype design will be created using
additive manufacturing, which will require the purchase of a thermoplastic. Before the final
prototype design(s) will be selected, the group will make two separate trips to Hershey Medical
Center to meet with Dr. Moyer and watch him perform endoscopic procedures. Final prototypes
will be micromachined out of Nitinol, which will be tested in a tissue­like substrate and egg
whites. Once the final design is chosen and tested, we will give a poster presentation. A bill of
materials along with the project budget can be seen in Appendix A.
7.2 Project Management
Mike Tramontozzi is our team’s point of contact, being the primary means of communication
with our sponsors. Mr. Tramontozzi will work with Mr. Hanks to set up meetings and conference
calls with Dr. Moyer and any other contacts. He will discuss and decide, with the sponsors, what
will be covered in the next meeting or call. Additionally, Mr. Tramontozzi will work with Dr.
Ritter and our sponsors to best meet the needs for the class and the project.
A long­term schedule was created to keep our team focused on the end product we will deliver
(Appendix B). This schedule was created by Vikram Eswar and was decided upon by the team.
Once we had a schedule, we met with our sponsor and decided on the major deliverables date
(Appendix C). Mr. Eswar will update this schedule as needed. He also created an availability
sheet that allows us to easily decide on meeting times with each other and our sponsors.
During these meetings, Andrew Simonson takes thorough notes, which he posts in our e­journal.
Although everyone writes down the important aspects of each meeting, Mr. Simonson’s notes
include finer details and allow absent members to understand everything that was discussed. The
previous notes are read before the next meeting, so each member can make sure they did not
miss any key details.
The time spent during each meeting is written down by Chris Pfeiffer­Kelly. He is in charge of
recording the time spent on the project each week and maintaining the budget. Mr. Pfeiffer­Kelly
will update members when they begin to fall behind in project hours to allow them to know they
23

25.
are putting in less effort than group members. This allows us to work efficiently and evenly
between members so there are no tensions between members.
All of this information is kept online in an e­journal by Daniel Johnson. He is responsible for
making sure all the notes, project details, schedules, assignments, files, and documents are
uploaded to the e­journal in a timely manner. Mr. Johnson organizes the e­journal to ensure that
project materials can be easily found.
7.3 Risk Plan and Safety
As with any medical procedure, the safety of the process is of the utmost importance. There are
a number of risk factors that are critical to the design and development of the device, as
highlighted in Table 8. From a technical and reliability standpoint, the device needs to stand
behind the claim that the fiducial piece detaches from the probe every time. This type of a
confidence claim is a bold statement, but one that is essential for the success of this device. In
order to mitigate any problems in making this claim, a detailed design of experiments will be
done to ensure the reliability of the device. If the device continues to fail and not meet the
standards, a different test method could be pursued. Another design could also be tested in
conjunction with the current design so that a backup plan exists.
Since the device is still in the concept feasibility phase of the design, many of the design
specifications are still undetermined or ambiguous. As a result of this, a change in design
specifications after a concept is selected and a prototype is developed could drastically impact
the success of the device. For this reason, the team has invested a significant amount of time in
brainstorming and prototyping. If a new specification came into place, there a number of other
designs and prototypes that could be pursued in time to complete testing on a device.
24

26.
Table 8. ​Risk plan with mitigating actions
Risk Level Actions to Minimize Fall Back Strategy
Change in
Dr. Moyer
specification
Moderate
­Speak with Dr. Moyer as
often as we can
­Try and address as many
issues as we can when
meeting with him
­Add time to schedule for refining
design
­Additional budget required
Schedule
delays
High ­Constantly track project
progress
­Look for ways to accelerate
activities
­Build in safety time
­Re­allocate resources
or staff
Delays in
order
placement or
delivery
Moderate ­Make sure parts are in stock
­Make sure purchasing
department has all needed
information
­3D print components
­Use Brad’s resources in Leonard
building
­Have multiple sources
Product does
not function
as predicted
Low ­Test early and often
­Alternative designs
­Have multiple prototypes on hand
Customer
not satisfied
High ­Prepare prototypes often
­Address concerns quickly
­Discuss ways to fix the problem
7.4 Ethics Statement
As a team dedicated to improving the quality of life of individuals suffering from pancreatic
cancer, we will act according to the moral principle of beneficence. It is our moral duty to only
present the facts about our device in an objective manner. We follow this value of trust, so the
consumers who use our device are not misled in any manner. Additionally, we will be held
accountable for any unethical actions or statements we make.
25

27.
7.5 Environmental Statement
Our team will only use the necessary amount of materials to create each prototype. Additionally,
we will try to reduce the waste we create by saving our prototype designs and reusing materials
when combining prototype ideas. Material waste disposal will follow strict guidelines, as
dictated by Penn State’s Environmental Health and Safety department. Our role in maintaining
the environment will follow the ethics described in Section 7.4.
7.6 Regulatory Considerations
The procedures for RFA and SBRT have been performed previously. There should be no
problem with FDA regulations in regards to these procedures. The golden fiducials that are being
considered for use are also a common technique used in marking the radiation site for SBRT.
The approval of that portion of the device should remain the same and under the responsibility of
the manufacturer. The material used for the radiofrequency ablation, nitinol, is already approved
for the ablation technique.
The use of the combination procedure may need to be looked at for further review by the FDA to
make sure that combining procedures is safe for the patient. The nitinol ablation probe may also
need reviewed if it is to be left in the body as part of the fiducial marker. These approvals will be
pursued during ​in vivo​ testing performed by researchers at Hershey.
7.7 Communication and Coordination with Sponsor
As stated in Section 7.2, Mike Tramontozzi will maintain constant contact with our sponsor
through e­mails. We meet with our sponsor every week on Tuesday at 1 pm. On February 22 and
29, members of our team will travel to the Hershey Medical Center to meet with Dr. Moyer and
watch him perform fine­needle aspiration surgery. After this meeting, conference calls will be
held roughly every three weeks to communicate with Dr. Moyer when needed.
26

28.
8.0 Detailed Design
Section 8.0.1 Modifications to Statement of Work Sections
Executive Summary
An updated financial breakdown was added to the executive summary. In addition, the number
of prototypes that the group is moving forward with was chosen to be two (coil and reverse
peacock). The executive summary was changed to reflect this.
8.0.1.1 Introduction
Current figures from American Cancer Society regarding pancreatic cancer incidence rates and
mortalities were found and added. Further information about how the grounding mechanisms
works was also added.
8.0.1.2 Customer Needs Assessment
Section was edited to highlight the fact that the project sponsor is Dr. Moyer and Brad Hanks is
providing assistance.
8.0.1.3. External Search
An additional product by Cook Medical was found that ran counter to the previous belief that no
endoscopic fiducial deployment methods exist. See Section 3.2 for details.
8.0.1.4 Engineering Specifications
Changes were made to reflect that the device being built is 3x scale of what will be used
clinically.
8.0.1.5 Concept Generation and Selection
Changes were made to specify which prototype was being evaluated in the metrics.
8.0.1.6 System Level Design
The two new prototypes that will be pursued are now highlighted. These are the reverse peacock
design and the coil design. The descriptions of each have been updated to highlight this change.
8.0.1.7. Special Topics
Special etchings will be added to the nitinol during the micromachining process so the device
can be seen under endoscopic ultrasound. This eliminates the need for golden fiducials. Needles
were added to properly test the deployment mechanism. Exact prices of travel expenses, nitinol
wire, regular liquid plastic, and needles have been determined and updated in the bill of materials
and budget found in appendices A.
27

29.
8.1 Manufacturing Process Plan
Table 9 illustrates the protocol for construction of scaled, 3D printed prototypes of both the coil
and reverse peacock. These non­conductive devices will primarily be used for deployment
testing and proof of concept. The procedure seen in Table 10 will create a model allowing
transmittance of RF energy from a function generator to the tissues. These scaled prototypes will
serve as an experimental comparison to thermal simulations. The final 3x scale deliverable
prototypes will be manufactured by Innovative Solutions, a micro­machining company based at
Penn State University. Usage of their picosecond laser will allow cutting and shaping of nitinol
at the millimeter scale without thermal deformation of the material itself. Further consultation
with the owner, Ben Hall, will lend further insight into the ease of manufacture and guide future
changes to the design. Mass production of the device can be outsourced to companies such as
Agilent Technologies which offer competitive rates of less than $50 per item; however, Hershey
Medical Center will likely handle pricing negotiations once further production is deemed
necessary and practical.
Table 9. ​Manufacturing Process Plan for 3D Printing Prototypes
Assembly
Name
Material Type Raw Stock Size Operations
3D Printed
Coil and
Reverse
Peacock
ABS Plastic
Filament
0.069” diameter Create model in SolidWorks
and save in .stl format on a
computer (See Appendix E)
Plug in the printer to an outlet
and connect the computer to the
printer via USB.
Coat the bed cover with
hairspray and attach it to the
heated bed using two paper
clamps in front and one on the
side
Open Repetier­Host program
and connect to the printer
28

30.
Load the .stl model to print
In the Object Placement
window select the rotate screen
and flip the object about the
appropriate plane until it
appears to lay flat on the visual
provided. Select the “Lay Flat”
option under rotate as well as
the “Center object” button
If required, scale the object
until a desired size using the
scale window
Click on the “Center object”
button
Go to “The slicr” window
Select the correct printer and
plastic from the drop down
menus, then change the infill
density and resolution of the
print. These values vary during
each print and were different
for each prototype modeled
Hit the “Slice Using Slicr”
button and allow the software to
generate G­code from the .stl
file
Once slicing has finished, go to
the G­Code window and
comment out all lines dealing
with setting the temperature
29

31.
Set the bed temperature to
105°F and turn on the heated
bed. Allow the bed to heat up
completely before continuing,
around five minutes
Set the extruder temperature to
200°F and turn on. Wait
approximately two minutes for
the extruder to heat up
completely before continuing.
Load the filament by sliding it
into the top of the printer and
clicking the lower filament
button by ‘1’ until a small
amount of filament comes out
of the extruder
Lower the feed rate setting to
50
Hit the “Print” button at the top
of the screen
Watch carefully for the first few
layers of the print and remove
obvious deformities with
tweezers
Once several layers are down
increase the feed rate to 100 for
the remainder of the print
After the print is complete,
remove the paper clamps
holding the glass to the heated
bed. Place the glass on a table
30

32.
and allow to cool for several
minutes
Carefully remove the part using
hands or tweezers
Hit the disconnect button in
Repetier­Host and unplug the
USB and power cord from
printer. No further treatment is
necessary
Table 10. ​Manufacturing Process Plan for Prototype Coil Design
Assembly
Name
Material Type Raw Stock Size Operations
Needle 304 Stainless
Steel
10 gauge:
0.134” OD,
0.106” ID
Turn 0.5” of stainless steel
needle down by 1/16” using a
lathe
Coil Nitinol 0.039” diameter
x 5’ wire
Heat 6” of wire to dull red glow
(roughly 500 °C) with acetylene
torch
Clamp end of annealed wire to
a 1” diameter stainless steel
pipe and wrap for 1.5”. Leave
1/10” of space between coils
Heat wire along pipe to dull red
color (500 °C) with torch
Quench wire­pipe construct in
room temperature water and let
sit for 10 min
31

33.
Needle­Coil
Assembly
After cooling, wrap wire around
faced stainless­steel needle for
0.5” in
Apply HighHeat Epoxy Putty to
both ends of wire with small
wire brush and let cure for 10 hr
8.2 Analysis
A theoretical analysis was performed for both the coil design and reverse peacock designs for
proof of concept. One of the most critical features of the design for the ablation probe is the
geometry. The geometry of the device dictates several functions of the device: the size and
shape of the ablation zone, how the physician will track the device in the patient, how/if the
device can penetrate the tumor, and the mechanism in which the fiducial will be left in the
patient.
For the coil design, the coil will initially be tightly wrapped around the shaft in the final device.
The shape memory effect of nitinol will take place as the probe is heated, and the coil will
conform to the spherical shape. For initial prototyping, heat generation was not used. Therefore,
in order to obtain the coil shape, the nitinol was manually bent and adhered to the shaft. A
springback calculation using an online program (custompart.net) was performed to determine the
degree at which the nitinol needed to be bent in order to achieve a 5 mm spherical radius. Given
that the thickness of the wire used for the prototyping was 1 mm, the yield strength for the
martensitic phase of nitinol is 40 GPa, the modulus for the martensitic phase of nitinol is 140
MPa and the K­factor is assumed to be 0.33, the initial bending radius to achieve a final radius of
5 mm is 4.572 mm (Nitinol, 2013).
The coil and reverse peacock designs rely on a male­female connection. The device will enter the
tumor with the male and female connection intact, but will separate upon the physician pulling
out of the tumor due to the friction of the tissue in the tumor. This will leave the female part
(effectively the fiducial), inside of the patient. The coefficient of friction between the tumor and
the device, therefore, should ideally be greater than the coefficient of friction between the male
and female connection. The equation for calculating frictional force is:
32

34.
FFT = μ N
where F​T ​is the total force, F​N ​is the normal force, and μ is the friction coefficient. For the
purpose of this analysis, we are assuming that the physician will pull the device at a high enough
force to overcome the friction regardless of the material, and so the coefficient of static friction is
of concern. We will assume that F​T ​and F​N​ are the same in each procedure. Therefore, we are
concerned with the ratio between the friction coefficients of the male­female connection and the
surrounding tissue to ensure that the device will separate while remaining inside the tumor. If the
coefficient between the male­female connection is greater than that between the outside of the
device and the tumor, the fiducial will not detach.
The two materials being considered for the male­female connection are stainless steel and
nitinol, as these are the two most common materials for syringes. Literature suggests that the
average coefficient of friction for stainless steel on stainless steel is 0.74 (Coefficient, 2006) and
the average coefficient of friction for nitinol on nitinol is 0.060 (NASA, 2009), which is much
lower than that of stainless steel. The properties of human tissue are not well researched;
however, a study from Johnson & Johnson suggests that the coefficient of friction for human
corneal tissue is around 0.0153 (Vistakon, 2013). This coefficient may not represent the type of
tissue that the ablation probe will experience, as the study focuses on corneal tissue. The
properties of ablated tissue are also unknown, but assumed to be stiffer than that of regular
tissue. The actual coefficient could therefore be greater than 0.0153. Whether or not the devices
detach ​ex vivo​ cannot be determined until ​ex vivo​ testing, but the coefficient for steel and nitinol
suggest that nitinol will detach more easily in the tissue.
The reverse peacock design contains tines that will be in compression inside of the sheath. The
void spaces where these legs will expand outward into the tissue provides a stress concentration
for when the physician is inserting the device into the tumor. These stress concentrations could
dictate the number of tines present in the final device. A larger number of tines was desired in
the final device as it was believed more tines would provide a better fixation of the device inside
of the tumor, as well as a more spherical ablation zone. A finite­element analysis model was
created using COMSOL Multiphysics Software in order to characterize the stresses on the
supports of device, and hand calculations were performed to verify the results.
An axial 5 N force, the average force necessary to pierce tissue, was applied along the needle tip.
The other end of the device was given a stationary boundary condition, as it is in contact with the
guidewire that the physician would be using. Figure 13 shows the von mises stresses on the
device, including a zoomed image of where the maximum von mises stress was found. The
33

35.
maximal force at the base of each support was only 19.7 MPa, much less than the compressive
yield stress of nitinol: 2550 MPa (Robertson, 2012). A hand calculation to verify the results
were performed using the definition of stress:
/Aσ = F
Using a force of 5 N and an area 0.02793 mm​2​
, which was calculated from the length and width
of a support, the stress was found to be 22.38 MPa.
Figure 13. The von mises stresses in A) the entire device and B) a zoomed in section of the
stress concentration.
In addition to a mechanical analysis on the reverse peacock, a thermal analysis was also performed. The
deployed reverse peacock model was imported into COMSOL. The simulation was only run for 4
minutes, although the minimum time for ablation is 10 minutes. Figure 14 shows the temperature profile
around the device at different time points. Figure 15 shows a 60 degree Celsius isotherm at different time
points. This temperature is the ideal temperature for burning tissue.
34

36.
Figure 14.​ Time­lapse contour plot of temperatures (°C) from reverse peacock ablation at (A) 0
min, (B) 1 min, (C) 2 min, and (D) 4 min.
35

37.
Figure 15.​ 60°C temperature surface contour plot at A) 0.2 min, B) 0.4 min, C) 1 min, and D), 4
min
8.3 Material and Material Selection Process
For the two prototypes being manufactured, several materials were selected to make up the
components. Not many materials are used so as to maintain the manufacturability of such a small
medical device. The material selection phase for the project was heavily influenced by already
existing needles resulting in only a small range of materials to decide among. The two prototypes
being developed use the same materials, but differ in manufacturing and overall design use of the
components. The process of selecting the particular materials was accomplished by consulting
with Dr. Moyer and Brad on what the industry standards are for endoscopic needles and then
36

38.
slowly adapting from there. Initially, gold and titanium seemed like viable options as they are
both biocompatible, non­toxic, and resistant to corrosion. Additionally, they have common uses
in fiducials and permanent implants, respectively. However, upon further consultation with
endoscopic radiologists, it was determined that simple etchings into the surface of the metal
would be sufficient for viewing, making the use of gold unnecessary. Based on established
design parameters which necessitated a certain degree of flexibility, titanium was ruled out due
to its high rigidity and Young’s modulus. The materials chosen will be broken down for each of
the devices:
Reverse Peacock
This design will be micromachined out of a 3 mm​ ​tube of 304 stainless steel as well as a 3 mm
tube of nitinol. These materials were chosen as they are relatively easy to micromachine and
acquire. Both are conductive and visible under ultrasound guided endoscopic procedures. They
are also both biocompatible (Santonen et. al, 2010), which is a minor customer need, but still
preferred. Both are of suitable flexibility; however, the nitinol version also has shape memory
properties making this version even more suitable for endoscopic deployment. The peacock
design has no mechanical component other than the male female connection at the end of the
device, thus can rely on the frictional forces of the metal to hold it in place until deployment.
Coil Design
A 2 mm steel tube will be used as the core of this design. It will also utilize nitinol wire that will
be wrapped around the core. The nitinol wire was selected to help with the spherical ablation as
well as act as the fiducial component following RFA. No material other than nitinol is as cheap,
accessible, and clinically tested. The steel needle part of the design is very machinable since it
requires only a lathe process to reduce the middle diameter. The nitinol wire was selected due to
the heat memory properties that allow it to be heavily deformed and then still return to its
prescribed shape when heated. The conductivity and visibility criteria are the same as those
described for the reverse peacock​.
8.4 Component and Component Selection Process
Careful selection of prototype components was necessary in order to ensure reliable fiducial
deployment and uniform ablation areas both during testing and in vivo. Upon observation of fine
needle aspiration procedures at Hershey and discussions with Dr. Moyer, it was determined that
the governing mantra should be “Simple is better”. Due to the small size of the device and its
subjection to variable shear and torsional forces, complex constructs will likely break and
become lodged within the working channel. Additionally, the nature of an endoscopic procedure
37

39.
necessitates flexibility, and designs with many parts would be unable to successfully navigate the
esophagus and stomach. As the desired shape of ablated tissue around the probe is spherical,
construction of the conductive elements in each probe design needed to lead to that shape.
The delivery mechanism for the current prototypes relies on a simple male­female connection.
This design relies on a press­fit contact between the “male” pin and “female” receptacle. As the
device is pushed through the narrow working channel of the endoscope, the connection is held.
An RF current can still be transmitted across the junction as long as both pieces are flush
together. Pulling the male stylet back will allow easy separation, leaving the female, in this case
fiducial component, behind. It was initially thought that the pin could be threaded and screwed
into the female holder ensuring a tight, reliable connection throughout the ablation. However,
further discussion with Dr. Moyer indicated that rotational movements, especially along the 220
cm endoscope, would not be possible. While the possibility of an actuator, such as a wire
wrapped around the junction, was considered in order to transfer an axial, pulling force into
rotation, the size of the device and addition of multiple parts would lead to a decrease in
manufacturability. Another delivery mechanism considered was the use of an adhesive polymer:
polylactic acid (PLA). At body temperature, the compound is gel­like and can attach the stylet to
the fiducial component. Upon being heated to temperatures upward of 60°C, PLA will melt
allowing separation. While the polymer is generally biocompatible, it was found that some of the
degradation products are mildly acidic (Hollinger, 1983). This could lead to potential
inflammation, immunogenic responses, and future complications. Additionally, the polymer
might degrade during transport or manufacture, resulting in faulty connections. After considering
all proposed delivery mechanisms both in terms of feasibility and biocompatibility, the simple
male­female junction was found to achieve separation without complication.
The selection of nitinol, a shape­memory alloy, as a material allowed for great diversity in
product ideas. Typical multi­pronged RF probes rely on spines manufactured a set distance apart,
severely limiting the geometry. These designs are typically preferred because electrode
separation allows for a larger ablation area. By heat treating nitinol, a wide range of shapes could
be obtained. This lead to the conception of the expandable balloon and whisk designs. Through
the natural course of the ablation, the compressed tines would slowly expand allowing for larger,
spherical heating zones. However, it was later found that the tough, rock­like stiffness of
pancreatic tumors would make this impossible. There would be no way to generate enough of a
radial force outward, whether it is through thermal expansion or inflation, to make this feasible.
Additionally, it was predicted that initial penetration through the stomach wall would cause
premature deployment of the whisk device, resulting in its expansion before entering the
pancreas. These factors, combined with difficulty in manufacturing at such a small scale, resulted
38

40.
in early dismissal of these two ideas. The decision to pursue further testing with the reverse
peacock and coil was due to their ability to combat these issues while still maintaining flexibility.
The former design would be capable of bending within the confines of the working channel.
Additionally, as this device easily fits within a standard 19 gauge needle, penetration into the
core of the tumor would be a non­issue. Finally, usage of the memory­shape characteristics
would allow expansion of the tips and facile entanglement within tumorigenic tissues. One key
aspect with both prototype ideas is that even failure of the deployment, whether it is suppression
of the “peacock feathers” or lack of expansion in the coil, will only minimally impact the success
of the procedure. In both cases, the ablation can still be carried out while leaving behind a
marker visible under ultrasound.
Ease of manufacture was considered during every step of the design process. The winged arrow
prototype, while innovative, would be nearly impossible to construct on a sub­millimeter scale.
The use of screws and joints cannot even be made on micro­machines as the tolerances would be
far too low. Additionally, there were too many potential complications for deployment of the
wings that would result in failure, such as the inability to catch in the tissues. The coil design
only requires the turning, a cutting method, of the needle to wrap the nitinol around. The actual
wire can be attached at the ends with a simple epoxy or weld, ensuring integrity. Similarly, the
reverse peacock can be easily micro­machine by cutting slits into the initial nitinol cylinder. Both
these designs also have large surface areas, compared to the wire meshes in the balloon/whisk
prototypes, allowing knurling of their surfaces. The etching of notches or divots is essential for
proper viewing under ultrasound.
8.5 CAD Drawings
The CAD and engineering drawings for the reverse peacock and coil design are given in
Appendix E. The final dimensions of the prototypes to be machined are given in millimeters.
Below are artistic renderings of the devices. For more exact design details please refer to the
appendix. Figure 16 depicts an artistic SolidWorks rendering of the fiducial needle along with
the nitinol coil, shown in red. Figure 17 is a similar artistic rendering of the reverse peacock,
made entirely of a single piece of nitinol with no assembly required. Figure 18 is a portrayal of
the design in its deployed state within the tumor, with the tines taking on an umbrella shape.
39

41.
Figure 16. ​Coil Rendering (Total Length: 25 mm)
Figure 17. ​Reverse Peacock Rendering (Total Length: 42 mm)
40

42.
Figure 18.​ Deployed Reverse Peacock
8.6 Test Procedure
The following test procedures will be conducted on an as­needed basis. At the end of each test,
pictures will be taken of the gel/eggs. This will allow us to remove the probe from the testing
materials and reuse it for additional testing. We will aim to complete each test three times, but
fatigue may cause the probe to fail during gel testing. To pass the gel test, the probe must enter
the gel, deploy, and remain in the gel. The ablation zone test will be used to characterize the
ablation area the device will create. The target for the ablation zone test is a sphere of around 2
cm within a timeframe of around 5 min, but any shape is acceptable.
The most important customer need is the device must detach 100% of the time. To test our
device, we are creating a gel with properties similar to that of cancer tissue. The device will then
be inserted into the gel. The needle and wire will be pulled back and removed from the gel, while
the fiducial is left behind. Exact steps for the procedure are listed below:
Creating the Gel
1. Pour approximately 750 mL of Regular Liquid Plastic into a 1 L beaker.
2. While gently stirring, heat the liquid to 350​°​F​.
3. Once the liquid is clear, discontinue stirring. Over stirring may lead to air bubbles inside
the gel.
41

43.
4. Pour the gel into clear bowls with approximate radii of 3 cm. Be sure to almost
completely fill the bowls.
5. Allow the gel to cool for at least 12 hours to ensure it hardens completely.
Gel Testing
1. Remove the gel from each bowl and place the flat surface against a table.
2. Insert the probe into the top of the gel until it is in the center of the gel.
3. While holding the gel against the table, deploy the probe and pull wire out of the gel.
Another important customer need is that the RFA probe creates a spherical heating zone. Egg
whites will be used to perform ablation zone testing. This test aims to show the exact geometry
and characteristics of cancer tissue that will be destroyed during RFA. This experiment allows
the viewing of the spherical ablation zone as it forms in the clear egg whites. As the temperature
of 60​°​C​ is reached, the egg whites cook causing them to become opaque. This zone will be
examined for sphericality for experiments with both prototypes at a variety of exposure times.
Exact steps for the procedure are listed below:
Ablation Zone Testing
1. Completely fill a bowl with an approximate radius of 5 cm with egg whites.
2. Attach alligator clips into the output channel of an arbitrary waveform generator.
3. Clip the red alligator clip to the endoscopic wire and the black alligator clip to ground.
4. Insert the probe into the middle of the egg whites.
5. Turn on the waveform generator and set it to a sine wave with a power of 70 W and a
current density of 11.0 amps/in​2​
(Boston Scientific, 2004).
6. Using a ruler, try to measure the dimensions of the “cooked egg” zone and turn off the
waveform generator once the radius is 2 cm in any direction.
8.7 Economic Analysis ­ Budget and Vendor Purchase Information
The materials necessary to create our final prototypes and conduct testing have been purchased.
It appears that the cost of each item was slightly overestimated which means we have more
money in our budget than initially planned. We have excluded the use of golden fiducials in our
design, which saved us approximately $150. We also saved a little more than $100 on travel
costs as compared to expected. This extra money allows us to either order more supplies to
create additional prototypes for testing or save as a reserve in the case of problems with the
micromachining process. The bill of materials and budget can be found in Appendix A.
42

44.
9.0 Final Discussion
Section 9.0.1 Modifications to Statement of Work and DSR Sections
9.0.1.1. Introduction
No changes were made.
9.0.1.2. Customer Needs
No changes were made.
9.0.1.3. External Search
No changes were made.
9.0.1.4. Engineering Specifications
No changes were made.
9.0.1.5. Concept Generation and Selection
No changes were made.
9.0.1.6. System Level Design
No changes were made.
9.0.1.7. Special Topics
No changes were made.
9.0.1.8 Detailed Design
The manufacturing plan for the reverse peacock in Section 8.2 was modified to include
sharpened feather tips, each at a 60​° ​angle to facilitate deployment. Additionally, the tines were
bent out before insertion into the gel. The test procedure in Section 8.6 was refined to match the
specifications of the devices in Hallowell. For ablation testing, a 25V DC was applied to both the
needle and reverse peacock with widths measured using digital calipers every 1 min.
9.1 Construction Process
There were several different phases for the prototyping of both the reverse peacock and coil
design devices, ranging from 3D printing to final micromachining.
Reverse Peacock
Initial designs for the reverse peacock were 3D printed using a MakerBot 3D printer. The CAD
drawing for the reverse peacock, as discussed in Section 8.5, was imported into the 3D printer
software. Table 9 in Section 8.1 discusses the specific procedure and setting for performing this
43

45.
procedure. The final printed device was comprised of PLA. Figure 19 shows an image of the
final printed device at 3x scale. This plastic could not be used for testing because the device
would begin to melt at ablation temperatures. However, these initial devices provided a visual of
the design and aided in determining on final dimensions for future prototypes.
Figure 19. 3D printed prototypes of both designs. The device to the left is the coil design.
The device to the right is the reverse peacock.
The next round of prototyping involved using stainless steel tubing and a dremel to create a 5x
scale prototype. The stainless steel tubing had an inner diameter ~5mm and an outer diameter
~5.5 mm. A 6 inch segment of the tubing was cut with a dremel. The dremel was then used to
perform cuts on the outside of the tubing in order to create the tines on the device. The
SolidWorks drawing in Figure 20 was followed to create the cuts; however, because the cuts
were performed by hand with a dremel a number of inaccuracies exists. Figure 21 shows the
dremel that was used to create the device. Figure 22 shows an image of the final 5x scale
prototype. This prototype was used for experimental ablation testing.
44

46.
Figure 20. SolidWorks drawing of the 5x scale deployed reverse peacock design.
Figure 21. Dremel used to create the 5x scale reverse peacock prototype.
45

47.
Figure 22. The final 5x scale prototype of the reverse peacock comprised of stainless steel.
As mentioned above, the reverse peacock design will first ablate the tumor and then detach by a
male­female connection to be left in the tissue for SBRT. The device in Figure 22 serves as the
female component of that connection. A male connection was designed in SolidWorks to
press­fit into the proximal end of the device. The original SolidWorks drawing is shown in
Figure 23; however, this drawing was modified so that the male connection ran down the entire
length of the device as opposed to just the proximal tip. The reason for this is so that the
connection would provide more support to the device while the physician attempts to insert the
device into the tumor and protect against buckling of the reverse peacock.
.
Figure 23. Original SolidWorks model of the male connection. This drawing was modified
to include a longer working channel within the device.
46

48.
This male component was machined in the Penn State Learning Factory using a lathe. A stock of
6 mm OD stainless steel was loaded into the lathe, and the outside of the stock was machined
until the desired diameter was achieved.
The final reverse peacock was micromachined at a 3x scale in State College, PA by L4iS.
Several lengths of nitinol tubing (~3 mm ID) and the SolidWorks drawing for the reverse
peacock were sent to L4iS to be micromachined. The micromachining process involved using
lasers to make the necessary cuts specified by the SolidWorks drawing. Figure 24 shows the
final micromachined device provided to the team by L4iS.
Figure 24. Final micromachined device provided by L4iS at a 3x scale comprised of nitinol
tubing.
Coil Design
Initial designs for the coil design were also 3D printed using a MakerBot 3D printer. The CAD
drawing for the coil design, as discussed in Section 8.5, was imported into the 3D printer
software. Table 9 in Section 8.1 discusses the specific procedure and setting for performing this
47

49.
procedure. The final printed device was comprised of PLA. Figure 19 shows an image of the
final printed device at 3x scale. This plastic could not be used for testing because the device
would begin to melt at ablation temperatures. However, these initial devices provided a visual of
the design and aided in determining on final dimensions for future prototypes.
The shaft of the coil design was created using a lathe in the Penn State learning factory. A piece
of 5 mm OD stock was placed in the lathe and machined to the dimensions specified in Figure
25. The drawing in Figure X is of a 5x scale.
Figure 25. SolidWorks drawing of the coil design.
After the device was machined, a 4 inch in length nitinol wire of 1 mm in diameter was wrapped
around the shaft by hand in the orientation shown in Figure 25. Initial prototypes used an
industrial strength glue to adhere the wire to the shaft. These prototypes were used as a visual of
how the final device should appear, and could not be used for testing as the heat ablation would
melt the glue. A number of methods to permanently adhere the wire to the shaft were attempted.
The first attempt was to solder the nitinol to the stainless steel shaft. The nitinol did not appear
to bond well to the solder, and as a result the connection between the wire and the shaft was very
weak. A literature review showed that it is difficult to solder nitinol wire because of the TiO2
that is formed on the surface [Soldering]. Welding the nitinol to the stainless steel would also be
very difficult for two reasons: the welding would be very difficult on a small scale, and because
nitinol is a shape memory alloy and it has thermal properties, the extreme heat from the welding
48

50.
process may affect the properties of the nitinol wire. Currently, there has been no successful
method to permanently fix the nitinol to the steel.
9.2 Test Results and Discussion
As mentioned in Section 8.6, device testing was primarily conducted in two areas: ablation and
deployment. Through the use of a synthetic gel matrix and egg whites, our team hoped to
quantify the detachment patterns and heating geometries of the reverse peacock model compared
to a standard needle. This would, in turn, allow us to determine how successfully we were
meeting the appropriate customer needs and find areas for improvement.
Ablation Testing
The first set of experiments conducted was with a 12 gauge stainless­steel needle. While much
larger than the standard 19 gauge device used in endoscopic procedures, the size was overall
very similar to the 6x scale reverse peacock. The overall setup, as depicted in Figure 26, relied
on a 25 V direct current being applied through the egg white solution. As the albumin coagulates
at 60°C, the same temperature tissue is ablated at, this set up provides a good representative
model. While a standard RF generator would use an oscillating current at a given frequency, the
testing equipment used here did not have this capability. Nevertheless, the resultant data provide
a general, qualitative depiction.
Figure 26.​ Ablation test set­up with red lead hooked to base of needle and a grounding black
lead to a copper wire dipped in the solution
49

51.
Initial tests with the needle found that egg whites coagulated around its entirety. As this was not
representative of a clinical setting, Kapton insulating tape was wrapped around the needle base to
prevent dissipation of current from this area, as seen in Figure 27. Additionally, a thermocouple
was inserted in the cannula providing real­time temperature readings for the duration of the
study. With such a high voltage, cooking began almost instantly with a temperature of 40°C
reached within 20 sec at the needle tip.
Figure 27.​ Standard 12 gauge needle wrapped in Kapton insulating tape
As seen in Figure 28, despite heating only at the needle tip, the ablation zone was distinctly
cylindrical in shape with charring occurring at the 5 min mark. The cooked egg whites seen in
solution were largely due to the thin grounding wire which resulted in a concentrated electric
field and faster cooking compared to the needle itself. Future iterations primarily relied on a
metal coffee can with the grounding alligator clip connected to the rim. This assembly better
mimics a true RFA procedure as the current would dissipate faster due to the larger surface area,
similar to the function of large grounding pads on the thighs of a patient. Care had to be taken
during the experiment to keep the device from touching the edges or bottom of the can which
would lead to a short­circuit.
50

52.
Figure 28.​ Ablation zone from 12 gauge needle at (A) 1 min and (B) 5 min
The actual width of the coagulated egg whites was obtained with digital calipers and is depicted
in Figure 29. The actual length was trivial as this can be adjusted by the physician through
retraction or extension of the device from the surrounding sheath. While there was a significant
increase in width initially, it tapered out largely due to charring. As the protein burned, it became
less conductive, impeding heat transfer. Future experimentation should include an actual
alternating current at the appropriate frequency. The overall width was also much less than
expected, maxing out at around 10 mm, most likely due to the size of the needle and charring.
Figure 29.​ Width of ablation zone over time for 25 V DC applied through 12 gauge needle
The reverse peacock benchtop testing seen in Figure 30 largely served as a comparison to the
baseline shown in Figure 28. While the zone is generally more spherical, burning was observed
51

53.
on the supports. Interestingly, by 6 min, spherical regions were visible at the tips of each of the
feathers. This will likely contribute to a much more round shape in smaller scaled models.
Figure 30.​ Ablation zone from reverse peacock at (A) 2 min, (B) 4 min, and (C) 6 min
Figure 31 depicts the change in width of the ablation zone over time at the widest part, in this
case the feather tips. Compared to Figure 29, the growth rate is far more even and linear,
indicating less charring and a more symmetrical ablated region. As before, the exact widths are
not truly accurate representations of the desired values, around 2­3 cm; however, the direct
correlation is promising.
Figure 31.​ Width of ablation zone over time for 25 V DC applied through reverse peacock
Figure 32 provides a much better representation of the ablation zone as a function of time. Tissue
death begins within 1 min of applying the current, especially at the needle and feather tips. By 2
min, the tissue between the center shaft and feathers begins to burn with complete destruction
52