Tissue equivalence of 3D printing materials with respect to attenuation and absorption of X‐rays used for diagnostic and interventional imaging

Abstract

Introduction Three‐dimensional printing is a promising technology to produce phantoms for quality assurance and dosimetry in X‐ray imaging. Crucial to this, however, is the use of tissue equivalent printing materials. It was thus the aim of this study to evaluate the properties of a larger number of commercially available printing filaments with respect to their attenuation and absorption of X‐rays. Materials and methods Apparent kerma attenuation coefficients (AKACs) and absorbed doses for different X‐ray spectra (tube voltages, 70–140 kV) were measured and simulated by Monte‐Carlo computations for a larger number of fused‐deposition‐modeling (FDM) materials. The results were compared with the respective values simulated for reference body tissues. In addition, the properties of polylactide acid samples printed with reduced infill densities were investigated. Results Measured and simulated AKACs and absorbed doses agreed well with each other and in case of AKACs also with attenuation coefficients derived from the reference database of the National Institute of Standards and Technology (NIST). For lung, adipose, muscle, and bulk soft tissue as well as for spongiosa (cancellous bone), printed materials with equivalent attenuation as well as absorption properties could be identified. In contrast, none of the considered printed materials was equivalent to cortical bone. Conclusion Several FDM materials have been identified as well‐suited substitutes for body tissues in terms of the investigated material characteristics. They can therefore be used for in‐house production of individualized and task‐specific phantoms for image quality assessment and dose measurements in X‐ray imaging.

Validation and study of different parameters in the simulation of diagnostic X-ray spectra using the MCNPX code

“…After achieving good agreement in the comparison with the AAPM TG 195 report, several simulations were performed varying X-ray tube parameters and the obtained spectra were compared with validated generators that use semi-empirical models. In this work, the semi-empirical generators SpekCalc and xpecgen were used due to their availability and because they are commonly used (mostly, SpekCalc) in the literature [20][21][22][23]5,10,16]. These softwares allow variations on both the target angle and filtration thickness, as well as in the electron beam energy.…”

Methodology for computed tomography characterization of commercially available 3D printing materials for use in radiology/radiation oncology

“…Recent studies have achieved this by incorporating commercially available materials consisting of plastics (e.g., PLA, ABS) doped with higher Z materials. [11][12][13][14] Some studies have also investigated the use of dual-nozzle printers to simultaneously print multiple materials within a 3D component to control average density/radiologic properties within small subvolumes. 12,13,19 The growing literature on this subject will help to find more applications and wider utility for 3D printing in radiology and radiation oncology.…”

“…12,13,19 The growing literature on this subject will help to find more applications and wider utility for 3D printing in radiology and radiation oncology. However, there is wide variability in printing techniques, measurement approaches, filament compositions (by manufacturer and by specific filament batch), as well as how printed components will be used (radiography/mammography, 10,14,[16][17][18]20,21 kilovoltage CT of various energies, 8,9,11,12,15,19,21,22 megavoltage applications such as MVCT or radiotherapy dosimetry, 6,7,12,13 or for exogenous components (e.g., bolus, orthopedic implants, brachytherapy applicators, etc.). 2,3 This work seeks to comprehensively evaluate commercially available 3D printing filaments with nonstandard composition for use in reproducing Hounsfield units (HUs) at various peak kilovoltage (kVp) spanning the range of all expected human tissues (from lung to dense bone) as well as even higher-density/higher-Z metallic implants.…”

“…It has proven more challenging to print components adequately mimicking properties of human bone with higher Z composition as well as variable densities between cancellous and cortical bone. Recent studies have achieved this by incorporating commercially available materials consisting of plastics (e.g., PLA, ABS) doped with higher Z materials 11–14 . Some studies have also investigated the use of dual‐nozzle printers to simultaneously print multiple materials within a 3D component to control average density/radiologic properties within small subvolumes 12,13,19 …”

“…The growing literature on this subject will help to find more applications and wider utility for 3D printing in radiology and radiation oncology. However, there is wide variability in printing techniques, measurement approaches, filament compositions (by manufacturer and by specific filament batch), as well as how printed components will be used (radiography/mammography, 10,14,16–18,20,21 kilovoltage CT of various energies, 8,9,11,12,15,19,21,22 megavoltage applications such as MVCT or radiotherapy dosimetry, 6,7,12,13 or for exogenous components (e.g., bolus, orthopedic implants, brachytherapy applicators, etc.) 2,3 .…”