3D Printing Of Multimodal,Heterogeneous Tissue-simulating Phantoms For Biomedical Optical Imaging

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases.However,the accuracy and the reproducibility of an optical imaging device are greatly affected by the performance characteristics of components,the test environment,and the operations.Therefore,it is necessary to calibrate these devices by traceable phantom standards.However,most of the currently available phantoms are homogeneous phantoms that cannot simulate multimodal and dynamic characteristics of biologic tissue.We propose to integrate different three-dimensional(3D)printing modalities in a 3D printing production line to produce tissue-simulating optical phantoms of multimodality and heterogenicity are given as follows:1.We proposed to integrate different additive manufacturing processes in a production line for fabrication of multimodal,heterogeneously optical tissue-simulating phantoms.The production line integrates a spin coating module,a PolyJet module,and a fused deposition modeling(FDM)module by an automatic control framework.A"digital optical phantom" was established by defining the prototype file that compiles the structural information and the optical parameters.Imported to the production line,the protype file controls the layer-by-layer phantom fabrication and sequential switch between different printing modalities.2.We demonstrated the integrated 3D printing of multi-layered,multi-scaled,and heterogeneous tissue-simulating phantoms.First,the epidermis layer phantom embedded with grooved skin-prints on the surface was spin coated using the positive textured silicon wafer as the substrate,the photocurable ink as the base material,the TiO2 as the scattering material,and the graphite powder as the absorbing material.Then,the dermis layer phantom was PolyJet printed on the epidermis phantom using the photocurable ink as the base material,TiO2 as the scattering material,and India ink as the absorbing material.Here,a skin reticular vessel in the dermis layer phantom can be printed if needed.The subcutaneous layer phantom was subsequently FDM printed using jelly wax as the base material,TiO2 as the scattering material,and graphite powder as the absorbing material.Combining with the casting technique,a multimodal,heterogeneous optical tissue phantom embedded with tumor and hollow vascular networks in the subcutaneous layer were fabricated.These phantoms mimicking structural and optical parameters tissue can be used not only for the calibration of optical imaging equipment,but also for the registration of multi-modal imaging technology.Both of them can promote the applications of optical imaging technology in clinical.3,We investigated the fabrication process and the polarization charactersitics of polylactic acid(PLA)phantoms.The phantoms were fabricated by sandwiching the electrospun PLA fibers in the middle of two pre-cast PDMS layers.An electrospinning system consisting of a microflow pump,a high-voltage power,a nozzle,and a rotating cylindrical collector was built to produce fibers with different orientations.Phantoms were finally fabricated by sandwiching the fibers between the plasma-processed grooved bottom PDMS layer and the top PDMS layer.The polarization test results indicated that phantoms fabricated with fibers collected in high/low rotational cylinder speeds can simulate polarization properties of normal/fibroma lesions tissue.The phantoms of long-term stability can be used not only to calibrate polarized optical imaging equipment,but also to help develop new optical treatments.4,Clinical utility of 3D printed phantoms in surgical planning was demonstrated through the case of conjoined twins surgery.Based on the CT data of the patients,the CAD models of the involved organs were reconstructed,and the casting mold and positioning system for assembling were designed.A tissue-simulating phantom of the conjoined twins was constructed by 3D printing of the skeleton and the molds of internal organs with ABS,casting internal organs using silica gel mixed with radiopacity materials of different colors,assembling the internal organ models,and casting them in a 3D printed shell structure.In addition,an algorithm for comparing the similarity of 3D models was proposed to verify the fidelity of the phantom.The results indicated that the proposed method was able to produce phantoms with optical and computered tomography(CT)contrasts,structural and functional characteristics,and simulated tissue heteregeneity.The 3D printed phantoms can be used for medical training and surgical planning in order to reduce the risk of surgery.