Fabrication of a pediatric torso phantom with multiple tissues represented using a dual nozzle thermoplastic 3D printer

Abstract

Purpose: To demonstrate an on-demand and nearly automatic method for fabricating tissue-equivalent physical anthropomorphic phantoms for imaging and dosimetry applications using a dual nozzle thermoplastic three-dimensional (3D) printer and two types of plastic. Methods: Two 3D printing plastics were investigated: (a) Normal polylactic acid (PLA) as a soft tissue simulant and (b) Iron PLA (PLA-Fe), a composite of PLA and iron powder, as a bone simulant. The plastics and geometry of a 1-yr-old computational phantom were combined with a dual extrusion 3D printer to fabricate an anthropomorphic imaging phantom. The volumetric fill density of the 3D-printed parts was varied to approximate tissues of different radiographic density using a calibration curve relating the printer infill density setting to measured CT number. As a demonstration of our method we printed a 10 cm axial cross-section of the computational phantom's torso at full scale. We imaged the phantom on a CT scanner and compared HU values to those of a 1-yr-old patient and a commercial 5-yr-old physical phantom. Results: The phantom was printed in six parts over the course of a week. The printed phantom included 30 separate anatomical regions including soft tissue remainder, lungs (left and right), heart, esophagus, rib cage (left and right ribs 1 to 10), clavicles (left and right), scapulae (left and right), thoracic vertebrae (one solid object defining thoracic vertebrae T1 to T9). CT scanning of the phantom showed five distinct radiographic regions (heart, lung, soft tissue remainder, bone, and air cavity) despite using only two types of plastic. The 3D-printed phantom demonstrated excellent similarity to commercially available phantoms, although key limitations in the printer and printing materials leave opportunity for improvement. Conclusion: Patient-specific anthropomorphic phantoms can be 3D printed and assembled in sections for imaging and dosimetry applications. Such phantoms will be useful for dose verification purposes when commercial phantoms are unavailable for purchase in the specific anatomies of interest.

Mechanical and medical imaging properties of 3D‐printed materials as tissue equivalent materials

“…The 3D printing material samples with 30 × 10 mm 2 and a length of 30 mm were made for X‐ray attenuation coefficient (μ ) testing. The method to measure μ of the sample was through digital radiography (CXDI‐55G, Canon, Japan) with dosimeter (Solid dose 400, German) 26 .…”

“…Tissue equivalent materials have been widely used in medical research and clinical simulator to mimic the properties of real tissues. For instance, medical imaging researchers utilize tissue equivalent materials to calibrate equipment and develop new imaging methods 1,2 . In clinical simulators, tissue equivalent materials play important roles as idealized tissue model to train clinical skills of medical worker 3,4 .…”

Reproduction of a conventional anthropomorphic female chest phantom by 3D‐printing: Comparison of image contrasts and absorbed doses in CT

“…The technology permits the use of comparatively low‐budget printers and allows the processing of a broad range of different materials. With professional equipment, the simultaneous processing of multiple materials to print different types of tissues is possible 1,2 . This printing method is common for the production of phantoms for x‐ray imaging and therapy 3–6 .…”

“…With professional equipment, the simultaneous processing of multiple materials to print different types of tissues is possible. 1,2 This printing method is common for the production of phantoms for x-ray imaging and therapy. [3][4][5][6] By reducing the density of the interior area (infill density), printed objects can be used to mimic the physical properties of different tissues.…”

“…Although various studies addressing patient‐specific printed phantoms have been published, 5,11–14 only few studies have performed detailed comparisons to conventionally produced anthropomorphic phantoms 1,2,15,16 . In the latter studies, computed tomography (CT) values (given in Hounsfield units [HU]) of reference phantoms could be reproduced with sufficient accuracy.…”