Additively Manufactured Patient-Specific Anthropomorphic Thorax Phantom With Realistic Radiation Attenuation Properties.

Sepideh Hatamikia,Gernot Kronreif,Ewald Unger,Gunpreet Oberoi,Wolfgang Birkfellner,Martin Buschmann,Barbara Knäusl,Francesco Moscato,Michael Figl,Joachim Kettenbach

doi:10.3389/fbioe.2020.00385

Abstract

Conventional medical imaging phantoms are limited by simplified geometry and radiographic skeletal homogeneity, which confines their usability for image quality assessment and radiation dosimetry. These challenges can be addressed by additive manufacturing technology, colloquially called 3D printing, which provides accurate anatomical replication and flexibility in material manipulation. In this study, we used Computed Tomography (CT)-based modified PolyJetTM 3D printing technology to print a hollow thorax phantom simulating skeletal morphology of the patient. To achieve realistic heterogenous skeletal radiation attenuation, we developed a novel radiopaque amalgamate constituting of epoxy, polypropylene and bone meal powder in twelve different ratios. We performed CT analysis for quantification of material radiodensity (in Hounsfield Units, HU) and for identification of specific compositions corresponding to the various skeletal structures in the thorax. We filled the skeletal structures with their respective radiopaque amalgamates. The phantom and isolated 3D printed rib specimens were rescanned by CT for reproducibility tests regarding verification of radiodensity and geometry. Our results showed that structural densities in the range of 42–705HU could be achieved. The radiodensity of the reconstructed phantom was comparable to the three skeletal structures investigated in a real patient thorax CT: ribs, ventral vertebral body and dorsal vertebral body. Reproducibility tests based on physical dimensional comparison between the patient and phantom CT-based segmentation displayed 97% of overlap in the range of 0.00–4.57 mm embracing the anatomical accuracy. Thus, the additively manufactured anthropomorphic thorax phantom opens new vistas for imaging- and radiation-based patient care in precision medicine.

Highlights

Medical imaging phantoms are widely used in radiology and medical physics to evaluate and adjust the performance of imaging devices (Filippou and Tsoumpas, 2018)
Number and percentage of the overlapped particles related to the point-based part comparison analysis (PPCA) analysis between the STL files acquired from patient and phantom thorax computed tomography (CT) are given in Table 3.The results from PPCA show that an average of 78% and 19% of all entities belonging to the thresholds I and II, respectively, completely matched between the STL files acquired from patient and phantom thorax CT
The production workflow of our novel thorax imaging model was different from the standard workflow of other human CT/magnetic resonance imaging (MRI) based additively manufactured (AM) medical models (Morikawa et al, 2017)

Summary

Introduction

Medical imaging phantoms are widely used in radiology and medical physics to evaluate and adjust the performance of imaging devices (Filippou and Tsoumpas, 2018) Their purpose is to assess imaging quality and radiation dosimetry by facilitating unrestricted repeated scans with defined parameters (Pogue and Patterson, 2006). Traditional mold phantoms usually consist of materials with tissue-equivalent radiopacity but they often have simple, homogenous forms and dimensions and do not mimic anatomy accurately (Ionita et al, 2014; Homolka et al, 2017) This often renders conclusions from phantoms to humans implausible (Pogue and Patterson, 2006; Jahnke et al, 2017; Hazelaar et al, 2018). Despite the ubiquitous existence of various thoracic pathologies and their imaging-based surgical and diagnostic procedures, more realistic models are required (Nardi et al, 2017; Huang et al, 2019; Montigaud et al, 2019)

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Conclusion