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  4. 3D Printed Phantom for MicroCT Imaging QA

3D Printed Phantom for MicroCT Imaging QA

S Bialek1, B Vojanovic2, A Kavanagh2, C Johnstone1, T Kanesalingam3, M Bazalova-Carter1* (1) University of Victoria, Victoria, BC, Canada (2) Oxford University, Oxford, UK (3) Xstrahl Inc, Suwanee, GA

Presentations

(Monday, 7/30/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 9

Purpose: The goal of this work was to develop and test a cylindrical tissue equivalent microCT imaging phantom that overcomes deficiencies of existing phantoms thanks to its mouse-like dimensions and to determine imaging protocols to ensure accurate animal positioning and dose calculations for small animal radiotherapy.

Methods: The 7.5-cm long and 2.4-cm diameter phantom was 3D-printed out of Somos Next plastic on an SLA printer. The modular phantom consisted of four sections: 1) CT number evaluation, 2) spatial resolution with slanted edge section (for longitudinal direction), 3) spatial resolution with hole pattern (for transversal direction, and 4) a uniformity and geometry section. The phantom was scanned in the small animal radiation research platform (SARRP) in the pancake geometry (stationary x-ray tube and detector and rotating couch) with a variety of imaging protocols, including our standard protocol with 60kV tube voltage, 1.2mA tube current, 275µm voxel size, 6fps acquisition speed and 120s imaging time. MicroCT images were automatically analyzed with a Python-based graphical user interface (GUI).

Results: All imaging protocols passed the geometric accuracy criterion of <200 µm as well as the >1.5 lp/mm@0.2 MTF criterion for spatial resolution in the transversal direction. Only the imaging protocol with 200µm voxel size passed the >1.5 lp/mm@0.2MTF criterion for spatial resolution in the longitudinal direction. The 70kV tube voltage dataset failed the noise test of <55HU and the bone CT number accuracy test of <55HU difference from the standard dataset. Due to inverse cupping artifact, none of the imaging protocols passed the uniformity test of <55HU.

Conclusion: The new 3D-printed phantom presents a useful tool for microCT image analysis as it closely mimics a small animal. In order to image small animals with acceptable image quality, the standard protocol with 200 µm voxel size should be chosen and inverse cupping artifact resolved.

Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by Xstrahl. TK is an employee of Xstrahl.

Keywords

Not Applicable / None Entered.

Taxonomy

IM- CT: Phantoms - physical

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