A phantom for testing Cone Beam CTs.

Cone Beam Computed Tomography (CBCT) scanners are becoming more common for dental and maxillofacial/head scanning, but performing image quality tests on these systems is difficult. There are quality assurance (QA) phantoms commercially available but they can be expensive, bulky and not optimised for CBCT imaging limits. Smaller phantoms often lack features that are recommended for testing CBCT systems. A custom made phantom can provide more useful test objects in a more convenient size and at a lower cost. The proposed phantom is called the "Karu" Cone Beam CT Phantom and is constructed with a 3D printed poly lactic acid (PLA) shell, with 3D printed inserts for holding the test details in place. Tests included are geometric accuracy (in three dimensions), Hounsfield Unit (HU) accuracy, low contrast detectability, spatial resolution (using line pairs), and uniformity/artifacts/noise. The phantom was scanned on a number of scanners and was clearly able to differentiate scanners producing poorer quality images from better quality ones. The phantom could be produced for under NZ $2000.