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Characterization of CT Hounsfield Units Uniformity of 3D-Printed Materials for Proton Therapy

E Orton1*, C Engelberts1, R Orbovic1, M Crocker1,2, B Basaric1, D Sobczak3, L Zhao3, (1) Adaptiiv Medical Technologies, Halifax, NS, CA, (2) Dalhousie University, Halifax, NS, CA, (3) St. Jude Children's Research Hospital, Memphis, TN

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Previous studies have evaluated Hounsfield units (HU) uniformity for a variety of 3D printing techniques but available technology and materials are rapidly evolving and differences in reporting of results prevented straightforward assessment of 3D printer-material combinations. The purpose of this work was to evaluate the HU uniformity of twelve 3D printer-material combinations (multiple materials with FDM, SLA, SLA-DLP, PolyJet, MJF, and SLS technologies) for use in proton therapy, using a criterion requiring the HU standard deviation to be = 10HU to minimize proton range uncertainty caused by material heterogeneity.


Methods: 5x5x2cm samples were produced with 12 3D printer-material combinations. For a subset of these combinations, multiple samples were produced to assess reproducibility and material batch, print orientation, print time, and print geometry dependence. CT scans were acquired using 120 kVp. HU uniformity was assessed for each sample as a whole and in nine spatially distinct sub-regions. A clinical HU to proton stopping power (SPR) calibration curve was used to project SPR values.


Results: All print techniques except the SLS-material and two MJF-material combinations met the uniformity criterion. Analysis of the nine sub-regions showed consistent print uniformity across sample volume for all prints that met the criterion for the whole volume. Mean HU of prints that met the uniformity criterion ranged from -65 to 237HU, with standard deviation ranging from 3 to 9HU. This translated into relative SPRs from 0.978 ± 0.004 to 1.144 ± 0.002. FDM-PLA and SLA-Clear Resin were the most thoroughly investigated and demonstrated good reproducibility with no significant dependence on material batch, print orientation, and print geometry.


Conclusion: The majority of 3D printer-material combinations investigated in this work met our CT-based radiological uniformity criterion and can therefore be considered for use in proton therapy applications. SPR measurements are the next step in this work.

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Funding Support, Disclosures, and Conflict of Interest: Conflict of Interest: All authors whose listed affiliation is Adaptiiv Medical Tehnologies are employees of this company.

Keywords

Protons, Image Analysis, CT

Taxonomy

IM/TH- Image Analysis (Single Modality or Multi-Modality): Quantitative imaging

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