3D Printing Materials Mimicking Human Tissues after Uptake of Iodinated Contrast Agents for Anthropomorphic Radiology Phantoms

Abstract

(1) Background: 3D printable materials with accurately defined iodine content enable the development and production of radiological phantoms that simulate human tissues, including lesions after contrast administration in medical imaging with X-rays. These phantoms provide accurate, stable and reproducible models with defined iodine concentrations, and 3D printing allows maximum flexibility and minimal development and production time, allowing the simulation of anatomically correct anthropomorphic replication of lesions and the production of calibration and QA standards in a typical medical research facility. (2) Methods: Standard printing resins were doped with an iodine contrast agent and printed using a consumer 3D printer, both (resins and printer) available from major online marketplaces, to produce printed specimens with iodine contents ranging from 0 to 3.0% by weight, equivalent to 0 to 3.85% elemental iodine per volume, covering the typical levels found in patients. The printed samples were scanned in a micro-CT scanner to measure the properties of the materials in the range of the iodine concentrations used. (3) Results: Both mass density and attenuation show a linear dependence on iodine concentration (R² = 1.00), allowing highly accurate, stable, and predictable results. (4) Conclusions: Standard 3D printing resins can be doped with liquids, avoiding the problem of sedimentation, resulting in perfectly homogeneous prints with accurate dopant content. Iodine contrast agents are perfectly suited to dope resins with appropriate iodine concentrations to radiologically mimic tissues after iodine uptake. In combination with computer-aided design, this can be used to produce printed objects with precisely defined iodine concentrations in the range of up to a few percent of elemental iodine, with high precision and anthropomorphic shapes. Applications include radiographic phantoms for detectability studies and calibration standards in projective X-ray imaging modalities, such as contrast-enhanced dual energy mammography (abbreviated CEDEM, CEDM, TICEM, or CESM depending on the equipment manufacturer), and 3-dimensional modalities like CT, including spectral and dual energy CT (DECT), and breast tomosynthesis.

Keywords: 3D printing; additive manufacturing; anthropomorphic phantoms; computed tomography; contrast-enhanced mammography; iodine contrast; medical imaging; quality control; radiology phantoms; tissue mimicking materials.

Figure 1

(a) PLA phantom of 6 cm diameter used for scanning of printed samples. View from above and below showing individual samples, and a 2 mL syringe in center filled with deionized water. (b) Single slice of the micro-CT image volume, indicating placement of ROIs used for determination of voxel values. (c–e): Transverse, coronal, and sagittal reformat of CT volume showing samples inside phantom. (c) Transversal reformat through section showing 6 cylinders with 8 mm diameter used for determining voxel values with iodine concentrations from 0 to 2.5% iodine, and water in the center. In (d,e) the water-filled syringe is shown centrally. Note: phantom sections containing thinner rods (5 and 3 mm in diameter) seen in coronal and sagittal reformats were not used in this work.

Figure 2

(a) Mass density measured in the test cylinders as a function of the iodine content. Points shown correspond to measurements from individual cylinders; (b) conversion of iodine content per weight (% w/w) to iodine content per volume (% w/v) as used in tomographic imaging. Points shown correspond to the calculated values using linear regression from (a).

Figure 3

Voxel values of the samples printed with iodine concentrations from zero (base polymer) to 3% elemental iodine (w/w) corresponding to 3.85% w/v. Blue data point at zero iodine content corresponds to the voxel value of deionized water. 1σ error bars are smaller than symbol size. (a) Voxel value vs. iodine content by weight, and (b) vs. iodine content per volume, converted according to Figure 2b.