title: Technical Note: Characterization of custom 3D printed multimodality imaging phantoms.
abstract: OBJECTIVE
  Imaging phantoms are important tools for researchers and technicians, but they can be costly and difficult to customize. Three dimensional (3D) printing is a widely available rapid prototyping technique that enables the fabrication of objects with 3D computer generated geometries. It is ideal for quickly producing customized, low cost, multimodal, reusable imaging phantoms. This work validates the use of 3D printed phantoms by comparing CT and PET scans of a 3D printed phantom and a commercial "Micro Deluxe" phantom. This report also presents results from a customized 3D printed PET/MRI phantom, and a customized high resolution imaging phantom with sub-mm features.
  
  
  METHODS
  CT and PET scans of a 3D printed phantom and a commercial Micro Deluxe (Data Spectrum Corporation, USA) phantom with 1.2, 1.6, 2.4, 3.2, 4.0, and 4.8 mm diameter hot rods were acquired. The measured PET and CT rod sizes, activities, and attenuation coefficients were compared. A PET/MRI scan of a custom 3D printed phantom with hot and cold rods was performed, with photon attenuation and normalization measurements performed with a separate 3D printed normalization phantom. X-ray transmission scans of a customized two level high resolution 3D printed phantom with sub-mm features were also performed.
  
  
  RESULTS
  Results show very good agreement between commercial and 3D printed micro deluxe phantoms with less than 3% difference in CT measured rod diameter, less than 5% difference in PET measured rod diameter, and a maximum of 6.2% difference in average rod activity from a 10 min, 333 kBq/ml (9 μCi/ml) Siemens Inveon (Siemens Healthcare, Germany) PET scan. In all cases, these differences were within the measurement uncertainties of our setups. PET/MRI scans successfully identified 3D printed hot and cold rods on PET and MRI modalities. X-ray projection images of a 3D printed high resolution phantom identified features as small as 350 μm wide.
  
  
  CONCLUSIONS
  This work shows that 3D printed phantoms can be functionally equivalent to commercially available phantoms. They are a viable option for quickly distributing and fabricating low cost, customized phantoms.
authors.affiliation: Department of Electrical Engineering, Stanford University, 350 Serra Mall, Stanford, California 94305.
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Bieniosek
authors.affiliation: Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, California 94305.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Lee
authors.affiliation: Departments of Radiology, Physics, Bioengineering and Electrical Engineering, Stanford University, 300 Pasteur Dr., Stanford, California 94305-5128.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Levin
mesh_terms: D008279:Magnetic Resonance Imaging; D064847:Multimodal Imaging / Q000295:instrumentation*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D066330:Printing, Three-Dimensional; D014057:Tomography, X-Ray Computed