The University of Kentucky Cancer Research Center requested that engineering students design a more comfortable headrest for patients undergoing breast biopsies via MRI. The existing headrest was uncomfortable, immobilizing, and caused neck/back pain. The engineering team designed a new headrest with 4 adjustable springs allowing horizontal and vertical movement. It also includes a mirror for a better view to reduce claustrophobia. Analysis showed the springs and connections could withstand stresses from patient movement safely. The prototype will be 3D printed and tested to ensure comfort and safety in the MRI environment.

1. University of Kentucky Cancer Research Center: Breast Biopsy
Headrest
Presenter(s): Ayoub Al-Wadhahi, David Stapleton, Elona Ryspayeva, Garrett
Cowen, Wesley Day, Scott Balch
Department of Mechanical Engineering
University of Kentucky, Lexington, KY
Introduction and Project Description
Project Requirements
Analysis
Team 2 of the senior design class has agreed to work
with doctors at the University of Kentucky Hospital to
design a headrest for their MRI (magnetic resonance
imaging) machine. The machine they have uses a 3
Tesla magnet- that’s 1000 times more powerful than a
refrigerator magnet. When undergoing a breast MRI
procedure and biopsy (an examination of tissue
removed from the body), the patient is put into a prone
(lying face downward) position for about an hour.
Having an uncomfortable support system can lead to
neck and back pain, especially for older patients
undergoing the process. Another result of lying face
down is claustrophobia. For these reasons, the hospital
sponsors have requested that team 2 create a more
comfortable headrest that also reduces the feeling of
being trapped in a small space.
The existing headrest in use at the hospital is a
Siemens Medical Solutions Opticomfort Headrest SEN.
The MRI technician adjusts this headrest, not the
patient. Additionally, this headrest has a small mirror
that allows for a narrow field of view. To improve upon
this design, the team has set out to create a headrest
that adjusts based on patient input and provides a
better field of view.
For the headrest, we had a few different concepts,
which we could choose for our design. Some concepts
that we came up with include a 2 spring supported
headrest, ball bearing track headrest, and 4 spring
supported headrest. After receiving sponsor input, and
careful analysis of all concepts, we have finalized our
design idea to the 4 spring supported headrest. We
have chosen this design because of its stability when a
load is placed onto the headrest, and its range of
motion. Adding to the range of motion was a must due
to sponsor requirements. The design we have chosen
would be able to handle the loading of a head, and
allow the patient to have some motion in the horizontal
and vertical axis. This creates a more comfortable
experience for the patient, as they are placed into an
MRI machine for an extended period of time. For
comfort, our final design will also include a mirror with
a poster outside of the MRI to give the patient
something to look at while in the MRI. Also, the final
design has an antibacterial memory foam cushion,
which will also help the patient be more comfortable.
Once our final concept was selected, we needed to
make sure that it was feasible. To do this we needed to
analyze the connections and most importantly, the
springs. For the springs, the two materials that were
considered were phosphor bronze and copper
beryllium. The analysis can be seen here.
Concept Selection
Prototype
The University of Kentucky Medical Center provided the
team with the following design requirements:
• The prototype must function in an MRI environment
(Non-ferromagnetic).
• Allow for the patient to move their head when
desired.
• Follow all FDA and CDRH regulations.
• Support a weight of 25 pounds (Average human
head weight, plus weight of the frame).
• Fit within the dimensions of the MRI opening (9.45” x
9.45” x 6”).
• Have and overall weight of less than 10 pounds.
• Be able to perform for 10 years or 3500 cycles.
• Reduce the claustrophobia felt by the patient during
the biopsy procedure.
• Not to exceed a budget of $1,000.
The team was able to solve the specifications provided
by the doctors in the following ways. To ensure that the
headrest prototype will be more comfortable, and less
claustrophobic for the patient, the frame will incorporate
a mirror and four compression springs. Most of the
prototype will be 3-D printed using PLA filament, which
will ensure the device is non-ferromagnetic. The PLA
filament is lightweight and durable so the weight and
strength requirements can be met. The compression
springs will be custom made with phosphor-bronze
wire, which is a non-ferromagnetic metal. By using the
3-D printer location on campus, the team will be able to
get all pieces of the device made for free. The only
significant costs of the prototype will be the springs and
the cushion for the headrest, so the prototype will meet
the budget constraints and leave extra money for
testing purposes.
The prototype, which the team will assemble, will consist
of mainly 3-D printed material. The 3-D printing will be
completed with the help if the University of Kentucky
Mechanical Engineering department. The main
components constructed using the 3-D printer will be the
base, headrest, spring housing, and the base for the
mirror. The remaining components, which include the
springs, bolts, cushion, and reflective mirror material, will
be ordered through outside vendors. Once assembled, the
prototype will undergo numerous testing, including
recruitment of volunteers to test the device and provide
feedback regarding its comfort level, as well as aid in
measuring the true deflection of the device from the force
exerted by a human head. Additional stress testing on the
springs and spring housing will be preformed with various
weights being applied to the entire device to observe the
outcome and any potential areas of failure. A Safescan
Ferromagnetic Detector will be unitized to ensure that the
device is non-ferromagnetic before finally being ran
through the MRI to ensure its safety and performance.
The bolted and screwed connections were much more
straightforward. For this analysis, the distortion energy
method was used. The showed us that with aluminum
screws and bolts that we had a safety factor of over 18
and the stress in the threads would be under 700 psi.
So this showed us that there will be no problems with
any connections that we have.
AutoCAD illustration of the final concept design
University of Kentucky department of Mechanical Engineering
3-D printer.
Patient undergoing a breast biopsy procedure