UWE Bristol Engineering showcase 2015

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Karen Li
BEng (Hons) Mechanical Engineering
Project Supervisor
Tushar Dhavale
4D-CT Respiratory Motion Phantom Manufacture
Introduction
Phantoms are medical devices that mimic and simulate a part of a body. The use of phantoms in radiation oncology are used by medical
physicists as a substitute for human tissue. The various types of phantoms used have evolved with time in terms of shape, material ,
mechanism and composition. The purpose of the said phantom is to conduct a quality check and assurance for medical imaging
equipment, such as the 4D-CT.
The investigation being carried out attempts to re-design and develop a respiratory motion phantom; for the benefit and usage to the
NHS radiotherapy team. The final design should be able to meet the list of requirements shown under project objective.
Project summary
The NHS radiotherapy team requires a
respiratory motion phantom that would
enable a quality control check on their 4D-CT
scan, to ensure that the systems are running
as expected.
Lung and Breathing Phantom
The NHS radiotherapy team had design a lung phantom that represents the
outlines of the lung with tumors inside, shown at the right. The lung
phantom would require a drive unit that would enable it to move with
respects to the breathing waveform, shown below. The breathing phantom
also known as the infrared reflectors , are detected and recorded by the
infrared camera that is stationed at the end of the CT table.
Concept Design and Development
There are a variety of stationary
phantoms that could be adjusted and
created to fit the requirements. For
this reason, several concept design
sketches were sketched and have
been redesigned based on the
requirements. Research such as: the
material, manufacture, motor
selection and the cost analysis were
made and checked throughout this
project. Each phantom designed was
made into a CAD file using Solidworks.
Cam Design
A human breathing waveform is a
sinusoidal function. However an
irregular sinusoidal can occur when the
patient is having difficulties breathing,
or s/he were coughing during the
procedure. Two cams were designed to
produce both desired waveforms. These
cams are the drive of the phantom as
they not only move the lung phantom
but will be moving the infrared
reflectors to produce the outcomes
shown on the right.
Modeling Stage and Final Product
With a selected material (acrylic) and a manufacture technique (laser cutter) the first phantom
was created, shown right. In total, three models were produced. Each model was tested and
further developed, based on the end users feedback. Two models proved to be successful in
terms of fulfilling some of the requirements, but unreliable at times due to its assembly. But with
careful precision and recalculation to eliminate the error, the final phantom was made and given
to the NHS radiotherapy team.
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Project Objectives:
The main objective is to produce a respiratory motion
phantom and for it to be able to fulfill the list of
requirements conducted by the end users:
- To produce a frequency of a range of 10 – 20
Breathes per Minute (BPM) although 5- 20 BPM
would be desirable.
-Be able to produce a smooth irregular and sinusoidal
breathing waveform.
- Low maintenance and cost to produce.
-The drive unit should be able to move the ‘lung
phantom’
- The CT image should be able to produce clear
definition of the tumor and of its range.
- Produce a platform for the infrared reflectors that
can move in a linear vertical axis whilst having some
ties with the lung phantom.
-An amplitude of up to 2cm in both the breathing
waveform and lung phantom.
Project Conclusion
In conclusion, the calculations made to define
the outcome prove to be a success. The final
phantom was able to achieve the list of
requirements. Compared to some of the
commercialized phantoms, this was by extent
the cheapest to manufacture, and with low
maintenance needed.