Three-Dimensional Printing for Construction of Tissue-Equivalent Anthropomorphic Phantoms and Determination of...

The purpose of this study was to develop a road map for rapid construction of anthropomorphic phantoms from computational human phantoms for use in diagnostic imaging dosimetry studies. These phantoms are ideal for performing pregnant-patient dosimetry because the phantoms imitate the size and attenuation properties of an average-sized pregnant woman for multiple gestational periods.

The method was derived from methods and materials previously described but adapted for 3D printing technology. A 3D printer was used to transform computational models into a physical duplicate with small losses in spatial accuracy and to generate tissue-equivalent materials characterized for diagnostic energy x-rays. A series of pregnant abdomens were selected as prototypes because of their large size and complex modeling. The process involved the following steps: segmentation of anatomy used for modeling; transformation of the computational model into a printing file format; preparation, characterization, and introduction of phantom materials; and model removal and phantom assembly.

The density of the homogenized soft tissue-equivalent substitute was optimized by combining 9.0% by weight of urethane filler powder and 91.0% urethane polymer, which resulted in a mean density of 1.041 g/cm³ measured over 20 samples. Density varied among all of the samples by 0.0026 g/cm³. The total variation in density was 0.00261 g/cm³. The half-value layer of the bone material was measured to be 1.7 mm of bone material at 120 kVp and when simulated by use of the density of the bone tissue-equivalent substitute (1.60 g/cm³) was determined to be 1.61 mm of bone tissue. For dosimetry purposes the phantom provided excellent results for evaluating a site's protocol based on scan range.

The 3D printing technology is applicable to the fabrication of phantoms used for performing dosimetry. The tissue-equivalent materials used to substitute for the soft tissue were developed to be highly adaptable for optimization based on the dosimetry application. Use of this method resulted in more automated phantom construction with decreased construction time and increased out-of-slice spatial resolution of the phantoms.