Three-dimensional Printing Technology Of Individualized Auditory Ossicles Based On Image Data

Background:3D printing(three dimensional printing, TDP) is considered to be a revolution technology in the manufacturing industry, and an innovative technology which can change the future and promote industrial progress. With the development of computer technology, the progress of production process and the advent of new materials, TDP has made great progresses in life science and many fields. As in the field of otolaryngology-head and neck surgery, currently, it has made gratifying progress and got extensive application in many aspects, such as anatomy training in otologic surgery, medical education, preoperative virtual reality and 3D modeling, filling and repair of large maxillofacial bone defects and so on.In the field of hearing reconstruction, as for the treatment of conductive hearing loss mainly due to the lesions of sound transmission structure caused by various reasons, ossicular chain reconstruction(OCR) is one of the important research directions in otomicrosurgery at present. However, because of the fine structures of auditory ossicles, complex lesion types, individual differences in shape and so on, only the artificial prosthesis with the similar length, angle and shape, could be implanted after shaping and sculpturing during the operation. The above processes not only increase the time and difficulty of operation, but also affect the sound transmission efficiency of ossicular chain. Based on the high-resolution CT(HRCT) technology, and applying the two-dimensional multi-planer reformation(MPR) and three-dimensional volume rendered(3D VR) technology, the lesions’ state of the patient’s ossicular chain could be made clear before the surgery, and accordingly, the total ossicular replacement prosthesis(TORP) or the partial ossicular replacement prosthesis(PORP), or even the conformal prosthesis which is fully consistent with the natural form of ossicular chain, could be pertinently designed for the OCR. If the above idea could be combined with computer-aided design and rapid prototyping technology, the manufacture of prostheses of individualized auditory ossicles in the true sense will come true. This research is based on the HRCT scanning data of temporal bone, with the rapid prototyping technology in the reconstruction of individualized auditory ossicles, whose processes are data conversion, computer-aided modeling and 3D printing, to reduce the sound transmission loss after the traditional operation of OCR and realize the accurate OCR, thus to provide a new way for treating conductive loss of ossicular chain. ObjectiveOur purpose is to reconstruct individualized auditory ossicles by computer-aided modeling and 3D printing, after extracting the axial HRCT scanning data of healthy temporal bones and data conversion, and compare them with the structures of healthy auditory ossicles to evaluate the accuracy of the 3D-printed auditory ossicles. Meanwhile, the 3D printing technology of individualized auditory ossicles based on HRCT scanning data will be explored. Materials and MethodsResearch participants were 34 patients(60 ears) with sudden deafness who were admitted to the department of otolaryngology-head and neck surgery in our hospital from October 2013 to June 2014, and other disorders of all their ears were excluded. Before operation, axial HRCT scans of temporal bones were performed on all the cases with 256-slice spiral computed tomography, and digital imaging and communications in medicine(DICOM) files with high resolution and high contrast were acquired. With the DICOM files input into the interactive medical image processing software Mimcs 16.0 for data transformation, the 3D segmentation and visualization of the target object was realized, and the target data obtained through computer-aided design(CAD) were input into the rapid prototyping software Magics 15.01, and finally with the data exported to the 3D printers, a real 3D object was manufactured. Since the middle ear disorders of all the affected ears were excluded, the structures of ossicular chains were acquiescently normal. With the 3D-printed auditory ossicles compared to the images of the normal ossicles which were regard as the standard, the iconic structures, such as head of malleus, neck of malleus, short process of malleus,manubrium of malleus,,body of incus, long crus of incus, short crus of incus, lenticular process,head of stapes, stapes arch, Stapes footplate and so on, were observed and used for evaluating the accuracy of the 3D-printed ossicles through the consistency check of kappa statistic. When get the target date,we input it to Magics 15.01 rapid prototyping auxiliary software and output it to 3d printing equipment,then, CAD data can be converted to the actual object. ResultsDisplay results of the auditory ossicles’ shape based on Mimcs data transformation are given to show the difference. In the following seven mark points, i.e.head of malleus, neck of malleus, manubrium of malleus, ariticulus incudomallearis,body of incus, long crus of incus, and short crus of incus, the display rates are all above 90%. Compared to the auditory ossicles images reconstructed from MPR and 3D VR, they have beautiful consistency and through Kappa consistency check, both of K values are greater than 0.75. As for lenticular process, head of stapes, stapes front arch and stapes back arch, the display rates are around 60%, and they have better consistency, K values are both greater than 0.4. But for stapes footplate, the display rate is only 25.0%. Compared to 76.4% of MPR and 52. 8% of 3D VR, they have weak consistency and K values are below 0.4. In all of the Kappa checks, the parameter P is below 0.05, then the results have statistical significance. It shows that the Mimcs software transformational malleus and incudes based on the HRCT of temporal bone have a high accuracy and were well restored. However, the Mimcs software transformational stapes based on the HRCT of temporal bone have a low accuracy and were badly restored. ConclusionIn the research, the basic realization of the rapid prototyping of individualized ossicles based on the HRCT data of temporal bone, and the printed malleuses and incuses with high accuracy, have laid the preliminary foundation for the application of the TDP individualized ossicles restoration.