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Description
Purpose: The purpose of this study is to make a heterogeneous phantom that reproduce the commercial Rando phantom by mixing the plaster powder and the poly lactic acid (PLA) powder.
Methods: In order to match the mean Hounsfield units (HU) values of Rando phantom, the bone tissue changes from plaster and PLA powder 0% to 35% to find an appropriate HU value, and soft tissue changes the infill value of the PLA to find an appropriate HU value. Bone tissue (200 HU or higher), soft issue (-500 to 200 HU), and air cavity (less than -500 HU) are modeled based on the HU value of the computed tomography (CT) image. The bone tissue is modeled as cavity, and after three dimension (3D) printing, a solution in which plaster and PLA powder were mixed is poured. To evaluate the bone implementation of the plaster mixed with PLA powder phantom, the HU profile of the CT image of the only PLA 3D printed phantom and Rando phantom printed using only PLA is evaluated.
Results: In Rando phantom, the mean HU value of soft issue is -22 HU, which is most similar to -20 HU with an infill value of 82%. The mean HU value of Bone tissue is 669 HU, which is 15% of the ratio of PLA powder to Plaster, most similar to the 680 HU value. In plaster mixed with PLA powder phantom, the soft tissue is manufactured with a 3D printer with an infill value of 82%, and the bone tissue is manufactured with percentage of PLA powder 15%. In HU value profile, the Plaster mixed with PLA powder phantom has mean difference of 61 HU between Rando phantom and soft tissue, and mean difference of 109 HU in bone tissue. Only PLA 3D printed phantom and Rando phantom have mean difference of 114 HU in soft issue and mean difference of 543 HU in bone tissue.
Conclusion: It is confirmed that the ratio of PLA powder and plaster can be adjusted to a HU value similar to bone issue. A simple combination of PLA powder and Plaster enable Rando phantom of soft tissue as well as bone tissue to create a more suitable custom phantom.
Keywords: Anthropomorphic head phantom, 3D printer, PLA powder, plaster
