Abstract
Currently, the validation of multimodal quantitative imaging and absorbed dose measurement is impeded by the lack of suitable, commercially available anthropomorphic phantoms of variable sizes and shapes. To demonstrate the potential of 3D printing techniques for quantitative SPECT/CT imaging, a set of kidney dosimetry phantoms and their spherical counterparts was designed and manufactured with a fused deposition modeling 3D printer. Nuclide-dependent SPECT/CT calibration factors were determined to assess the accuracy of quantitative imaging for internal renal dosimetry. Methods A set of four one-compartment kidney phantoms with filling volumes between 8 mL and 123 mL was designed based on the outer kidney dimensions provided by MIRD Pamphlet 19. After printing the phantoms, SPECT/CT acquisitions of three radionuclides (Tc-99m, Lu-177, and I-131) were performed and calibration constants determined for each radionuclide-volume combination. A set of additionally manufactured spheres matching the kidney volumes was additionally examined to assess the influence of the phantom shape and size on the calibration constants. Results A set of refillable, waterproof and chemically stable kidneys and spheres was successfully manufactured. Average calibration factors for Tc-99m, Lu-177, and I-131 were obtained in a large source measured in air. For the largest phantom (122.9 mL), the VOIs had to be enlarged by 1.2 mm (Tc-99m), 2.5 mm (Lu-177), and 4.9 mm (I-131) in all directions to obtain calibration factors comparable to the reference. While partial- volume effects were observed for decreasing phantom volumes (percentage difference up to 9.8 % for the smallest volume of 8.6 mL), the difference between corresponding sphere/kidney pairs was small (< 1.1% for all volumes). Conclusion 3D printing is a promising prototyping technique for geometry-specific calibration of SPECT/CT systems. While the underlying radionuclide and the related collimator have a major influence on the calibration, no relevant differences between kidney-shaped and spherically-shaped uniform-activity phantoms were observed. With comparably low costs and sub-mm resolution, 3D printing techniques hold the potential for manufacturing individualized anthropomorphic phantoms in many clinical applications in Nuclear Medicine.
- Instrumentation
- Radiobiology/Dosimetry
- Renal
- SPECT/CT
- Other
- 3D Printing
- Anthropomorphic Phantom Design (Kidney)
- Gamma Camera Calibration
- Internal Radiation Dosimetry
- Quantitative SPECT Imaging
- Copyright © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.