Abstract
Purpose Respiratory motion during positron emission tomography
(PET) scans can be a major detriment to image quality in oncological
imaging, leading to loss of quantification accuracy and false negative
findings. The impact of motion on lesion quantification and
detectability can be assessed using anthropomorphic phantoms with
realistic anatomy representation and motion modelling. In this work we
design and build such a phantom, with careful consideration of system
requirements and detailed force analysis.
Methods: We start from a previously-developed
anatomically-accurate shell of a human torso and add elastic lungs with
a highly controllable actuation mechanism which replicates the physics
of breathing. The space outside the lungs is filled with a radioactive
water solution. To maintain anatomical accuracy in the torso and
realistic gamma ray attenuation, all motion mechanisms and actuators are
positioned outside of the phantom compartment. The actuation mechanism
can produce a plethora of custom respiratory waveforms with breathing
rates up to 25 breaths per minute and tidal volumes up to 1200mL.
Results: Several tests were performed to validate the
performance of the phantom assembly, in which the phantom was filled
with water and given respiratory waveforms to execute. All parts
demonstrated nominal performance. Force requirements were not exceeded
and no leaks were detected, although continued use of the phantom is
required to evaluate wear. The respiratory motion was determined to be
within a reasonable realistic range.
Conclusions: The full mechanical design is described in this
paper, as well as a software application with graphical user interface
which was developed to plan and visualize respiratory patterns. Both are
available open source and linked in this paper. The developed phantom
will facilitate future work in evaluating the impact of respiratory
motion on lesion quantification and detectability.