Developing a system of holders for an ultrasound kinematic analysis system

Field: Engineering (Physical Sciences)

Background:
Because the current techniques for the analysis of knee kinematics are either invasive or radiative, the demand
for new, non-invasive and non-radiative techniques has originated. A system that relies on ultrasound
is one of the explored alternatives. The goal of this bachelor report is to develop a holder that is the interface
between the ultrasound system and the patient. The holders must enable the dynamic reconstruction of
the knee joint kinematics. Theretofore 30 ultrasound transducers must be divided in correct manner over the
upper and lower leg of the patient. This enables the localisation of the femur and tibia bone of this patient
and as a result the reconstruction of the knee kinematics.
Analysis Phase:
The first step was to map the current situation regarding the development of the ultrasound system. By
attending a cadaver testing, an attempt was made to provide insights in the operation and shortcomings of
the required materials. Furthermore the knowledge regarding ultrasound has been broadened by looking
into the theory behind it. Besides the Visualeyez motion capture system has been analysed and it is specified
that the prototypes will be fabricated using 3D-prinitng techniques. The use of A-mode ultrasound and
the Visualeyez motion capture system incorporates several requirements and limitations to the design of the
holders. These, together with the requirements and wishes of the client, are translated into a statement of
requirements.
Concept phase:
After the analysis phase the exploration of possible solutions for the design of the holders started, complexity
and versatile were varied here. The three most promising ideas are further elaborated into basic concepts,
where it is tried to establish a basic principle behind the ideas. Eventually the most promising concept
is chosen and a simplified prototype has been tested. The goal was to determine the feasibility of the
basic idea. By determining if it is even possible to keep seeing the bone during a dynamic measurements
using ultrasound, an estimation could be made whether the principle is viable. The results of this test were
positive, but it was decided that structured testing was necessary to reveal where on the leg the chosen
basic principle works. The reason was the uncertainty regarding the performance of the chosen principle
on the characteristic locations, who are required for the reconstruction of the kinematics. The locations that
would be tested were determined using a theoretical approach and then tested using an especially designed
testing holder. This resulted in the 30 most appropriate locations to reconstruct the kinematics using the
basic principle.
Final concept phase:
Using the observations done during the location testing, a morphological analysis could be prepared. It was
used to be able to make choices regarding a few key components. Based on the information obtained in the
location testing and the morphological analysis, concepts could be made of the six separate holder parts.
For each of them a parametrisation has been prepared to enable the fabrication of versions tailored specially
for a subject. The concepts are then translated to Solidworks models, using the parametrisation as base
for the models. Prototypes of the models were printed and analysed, leading to several improvements to the
design, these were implemented in the final design of the concepts. Furthermore a special documentation
has been written explaining how a subject must be measured and how these values can be translated into
subject specific Solidworks models.
Conclusion:
Eventually a concept is developed that enables the analysis of the knee kinematics in a dynamic fashion.
While no conclusions can be drawn regarding the working of the system of holders, they aren’t tested yet,
it can be said that it is proven that, while using the chosen basic principle, it is possible to keep seeing the
bone in the characteristic locations required to reconstruct the knee kinematics.