Active and passive elasticity measurements of the tongue using in vivo measurement techniques

Among all treatments of cancer, surgery of locally advanced head and neck
cancer has one of the highest risks of loss of vital functions. Speech,
mastication and swallowing are complex functions that are easily affected. The
term *functional inoperability* is used when unacceptable function loss after
surgery is to be expected. It is hard to reach a consensus for the majority of
surgical interventions regarding functional inoperability. Making effective
patient counselling on the expected outcome impossible. To make a better
prediction of functional loss after treatment a project was launched called
Virtual Therapy. This project aims to develop a biomechanical model to simulate
different treatment options and predict functional outcome on founded
expectation. To make this model as accurate patient specific as possible, it is
important to have knowledge of elastic properties of tissues in the oral
region, e.g. the tongue. Elastic properties of the tongue are strongly
influenced by postoperative fibrotic changes. but before we can say anything
about the effects of fibrosis in patients we need to measure the passive and
active stiffness of healthy tongue tissue. Shear wave ultrasound elastography
and LASTIC are promising techniques to measure in vivo tissue elasticity.

The primary objectives of this study are:
* Analyse if shear wave ultrasound elastography with ElastQ and LASTIC are both
feasible techniques to identify differences in tongue tissue elasticity and
analyse if there is a correlation between both techniques.
* Investigate if shear wave ultrasound elastography and/or LASTIC can be used
to distinguish the *active* and * passive* component of the tongue muscle
elastic properties.

Prospective feasibility study

No risks are expected with any of the interventions performed in this research
protocol. The measurement for the active component of tongue stiffness takes up
to twenty minutes and will be scheduled on a moment that is most suitable for
the patient. The passive component measurement will be performed under general
anaesthesia.

The risk of possible tissue damage with LASTIC has been reduced to a very
minimum. Several articles describe that human cells and tissue will be damaged
after applying 50% or more strain to the tissue for 5-10 minutes.. To set the
strain limit on 50% and only applying it for a few seconds we assure no damage
to the tissue will be done. If the volunteer experiences pain and wants to
terminate to measurement all pressure can be released with the turn of one
valve to assure direct and safe removal of the suction cup.