Design of an anthropomorphic PET phantom with elastic lungs and respiration modeling

Abstract

<p><b>Purpose</b> 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.</p><p><b>Methods:</b> 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.</p><p><b>Results:</b> 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. </p><p><b>Conclusions:</b> 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.</p>

Technical note: Low‐cost MR‐compatible pneumatic respiratory organ motion simulator for the development of MR‐guided thermal therapy

“…The respiratory motion simulator was designed based on the fabrication methods and components used in earlier approaches 9,13,17,18 . Our design improves on them by offering a low‐cost and simple fabrication process.…”

“…There is a need for dynamic motion phantoms in the early stages of the development of new, motion‐robust, and fast MRI techniques in abdominal organs. Several custom‐made respiratory phantoms have been developed to evaluate motion compensation in MRI techniques 9,13,17,18 . For instance, Maier‐Hein et al.…”