Clinical Applications of Physical 3D Models Derived From MDCT Data and Created by Rapid Prototyping

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1 Special rticle Pictorial Essay Esses et al. pplications of 3 Models erived From MT ata Special rticle Pictorial Essay ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved Steven J. Esses 1,2 Phillip erman 1 llan I. loom 1 Jacob Sosna 1,3 Esses SJ, erman P, loom I, Sosna J Keywords: 3 model, prosthesis design, rapid prototyping, surgical planning OI: /JR Received ugust 29, 2010; accepted after revision September 30, epartment of Radiology, Hadassah Hebrew University Medical enter, PO ox 12000, Jerusalem 91120, Israel. ddress correspondence to J. Sosna (jacobs@hadassah.org.il). 2 Mount Sinai School of Medicine, New York, NY. 3 epartment of Radiology, eth Israel eaconess Medical enter, Harvard School of Medicine, oston, M. WE This is a Web exclusive article. JR 2011; 196:W683 W X/11/1966 W683 merican Roentgen Ray Society linical pplications of Physical 3 Models erived From MT ata and reated by Rapid Prototyping OJETIVE. In this article, we describe the production of physical models from T data using rapid prototyping and present their clinical application. MT data acquisition of isotropic voxels and modern postprocessing techniques provide exquisite detail for clinicians and radiologists. ONLUSION. In recent years, rapid prototyping technologies have provided new possibilities to visualize complex anatomic structures through the generation of physical models that can be used to assist with diagnosis, surgical planning, prosthesis design, and patient communication. ackground Rapid prototyping involves creating a physical 3 model from a computer model. The technology has been used by industry to create forerunners of intended final products, including automobiles, toys, and computers. Models can be analyzed and modified before production is planned [1]. In medicine, rapid prototyping has been used by physicians to improve diagnostic accuracy, plan complex interventions, and aid in medical student and resident understanding of disease. It has been particularly helpful with regard to complex anatomic structures and disorders that are not easily captured or understood in two dimensions. Some T workstations can now quickly export IOM-based T data into the standard triangular language (STL) format used in rapid prototyping. This has greatly facilitated the printing of 3 models derived from radiologic images (Fig. 1). In the printing process, T slices are created as 2 layers, and a method of assembling these layers into a solid mass is applied. s T slice thickness is reduced, 3 model resolution will continue to improve [1]. Methods of Rapid Prototyping There are five major types of rapid prototyping: STL, selective laser sintering, fused deposition modeling, multijet modeling, and 3 printing. In STL, a laser emitting ultraviolet light causes local polymerization of a pool of photosensitive resin in shapes corresponding to each T slice. In selective laser sintering, a laser is used to fuse small plastic, metal, or ce- ramic particles into a 3 object. In fused deposition modeling, a plastic is melted and extruded through a nozzle that can move horizontally and vertically to lay down plastic according to T slice information. In the multijet model process, layers of powder are selectively bonded by a water-based ink that is released in the shape corresponding to the T slice information. In 3 printing, a photopolymer-based resin is jetted via high-resolution inkjet and cured using ultraviolet light [2]. linical pplications Maxillofacial Surgery and Otolaryngology Three-dimensional models are particularly useful for planning maxillofacial surgeries, because the anatomy and procedures in this region are especially complex (Figs. 2 and 3). n early prospective trial assessed the efficacy of 3 biomodels in craniofacial and maxillofacial surgeries. Three-dimensional models contributed positively to diagnosis, operative planning, and informed consent. In addition, surgeons estimated that the use of models reduced operating time by a mean of 17.63% [3]. Rapid prototyping plays an important role in prosthesis engineering for craniofacial and maxillofacial surgery and otolaryn gologic reconstructive surgery (Fig. 4). In one study, rapid prototyping technology was used to create auricular prostheses according to T scans of patients contralateral ears. The most common indications for reconstructive surgery were ear loss due to tumor, congenital malformation, and traumatic ear injury. 3 image of the pa- JR:196, June 2011 W683

2 Esses et al. ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved tient s unaffected ear was created on the basis of T data and was inverted, creating a mirror image. cast of the inverted image was created using rapid prototyping, and the final prosthesis was created from this cast [4, 5]. Neurosurgery Rapid prototyping has also been used for neurosurgical procedures, including repair of skull defects and intravascular interventions. Several groups have created 3 models of cranial defects from T scans to personalize the cranial implant used for repairs [6, 7] (Fig. 5). enefits derived from the plates included reduced hospital admissions, improved fit, and improved cosmetic outcomes. Other groups have used the models to plan constructive and reconstructive cranioplasty and to plan surgical approaches to uncommonly complex skullbased tumors. In most of these cases, operating time and errors were reduced [8]. Orthopedics Several groups have begun to use rapid prototyping technology for orthopedic diagnosis and surgical planning. The technology has been applied to treat disorders of the spine, hip, pelvis, and shoulder (Fig. 6). One group used 3 polystyrene models based on T scans in the treatment of complex and severe spinal deformity. The models allowed the surgeons to measure deformities directly, perform preoperative morphologic assessments, and communicate more effectively with families. The models also allowed the surgeons to preoperatively determine the proper location for placement of pedicle screws [9]. ardiovascular Three-dimensional models can play a major role in the diagnosis and treatment of cardiovascular disease. The technology can be particularly helpful with respect to surgical and catheter-based interventions. These procedures can be aided by a physician s ability to physically manipulate rapid prototyped models to determine the 3 spatial relationships of cardiac structures. Many reports in the literature describe the use of models in the treatment of valve disease. Schievano et al. [10] determined patients suitability for percutaneous pulmonary valve implantation by assessing 3 MRIbased models of the right ventricular outflow tract and pulmonary trunk. ardiologists correctly determined whether valve implantation would be successful in two of eight patients using MRI alone and in five of eight patients using the rapid prototyped models. Rapid prototyping has also been used for the surgical and catheter-based treatment of pathologic abnormalities involving the aorta, including cases of complex abdominal aortic aneurysms (Fig. 7). The models can help orient clinicians in catheter-based interventions, such as coronary artery stent procedures (Fig. 8). onclusion Rapid prototyping can assist with diagnosis, surgical and catheter-based intervention planning, patient communication, and prosthesis design in fields as diverse as maxillofacial surgery and cardiology. In the past 2 years, vendors have begun to equip workstations with the ability to convert IOM files from T scans to STL files, thereby drastically reducing the complexity and time to create physical models. Rapid prototyping technology may become another tool for radiologists to improve visualization of complex anatomy. Fig. 1 Photograph of rapid prototyping device. Patient undergoes T, and 3 rendering is derived from IOM-based T data on 3 workstation. Images are exported in standard triangular language format, which can be read by the rapid prototyping device, and a physical model is created. (Photograph of 3 printer courtesy of Objet Geometries, Ltd.) References 1. Webb P. review of rapid prototyping (RP) techniques in the medical and biomedical sector. J Med Eng Technol 2000; 24: Kim MS, Hansgen R, Wink O, Quaife R, arroll J. Rapid prototyping: a new tool in understanding and treating structural heart disease. irculation 2008; 117: Urso PS, arker TM, Earwaker WJ, et al. Stereolithographic biomodelling in craniomaxillofacial surgery: a prospective trial. J raniomaxillofac Surg 1999; 27: Karayazgan-Saracoglu, Gunay Y, tay. Fabrication of an auricular prosthesis using computed tomography and rapid prototyping technique. J raniofac Surg 2009; 20: Turgut G, Sacak, Kiran K, as L. Use of rapid prototyping in prosthetic auricular restoration. J raniofac Surg 2009; 20: Maravelakis E, avid K, ntoniadis, Manios, ilalis N, Papaharilaou Y. Reverse engineering techniques for cranioplasty: a case study. J Med Eng Technol : Winder J, ooke RS, Gray J, Fannin T, Fegan T. Medical rapid prototyping and 3 T in the manufacture of custom made cranial titanium plates. J Med Eng Technol 1999; 23: Müller, Krishnan KG, Uhl E, Mast G. The application of rapid prototyping techniques in cranial reconstruction and preoperative planning in neurosurgery. J raniofac Surg 2003; 14: Mao K, Wang Y, Xiao S, et al. linical application of computer-designed polystyrene models in complex severe spinal deformities: a pilot study. Eur Spine J 2010; 19: Schievano S, Migliavacca F, oats L, et al. Percutaneous pulmonary valve implantation based on rapid prototyping of right ventricular outflow tract and pulmonary trunk from MR data. Radiology 2007; 242: W684 JR:196, June 2011

3 pplications of 3 Models erived From MT ata ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with ameloblastoma of left mandible., Image shows 3 rendering of mandible. and, 3 rapid prototyped model allowed preoperative planning of bony incisions () and preoperative contouring of titanium bone plate used in mandible reconstruction (). Preoperative contouring allowed moreprecise plate to be constructed., Photo shows plate in use during surgery. Operating time was substantially reduced. E and F, efore subsequent operation, another 3 model (E) was constructed by rapid prototyping to aid in planning dimensions of bone graft that would be harvested from patient s hip during surgery. 3 model illustrating bone graft placement (F). one graft was implanted in operating room, thereby completing jaw reconstruction. G, Image shows graft after implantation. E F G JR:196, June 2011 W685

4 Esses et al. ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man whose right zygomatic bone was fractured in fight. and, xial T image () and 3 reconstruction () illustrate fracture; 3 image was exported in standard triangle language format., Physical model was created by rapid prototyping. Fig year-old girl who presented with limited ability to open her mouth because of overgrowth of coronoid process of mandible., T-derived 3 reconstruction illustrates extent to which patient was able to open her mouth., 3 reconstruction illustrates coronoid process overgrowth. and, 3 rapid prototype models were used to determine optimal point for resection. Surgery enabled patient to open her mouth more widely. (Fig. 4 continues on next page) W686 JR:196, June 2011

5 pplications of 3 Models erived From MT ata ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved Fig. 4 (continued) 18-year-old man whose right zygomatic bone was fractured in fight. and E, 3 model was used as template to create implant. F, Photograph shows patient before surgery. Note that area of fracture underneath right eye has sunken appearance. G, Photograph shows patient after surgery. Fig. 5 3 model of a skull after craniectomy., To personalize cranial implants in skull repairs, a 3 model of the negative defect is created., Model of implant is shown fitted to skull defect. Implant is then produced from biocompatible acrylic media. (Photographs courtesy of Objet Geometries, Ltd.) F E G JR:196, June 2011 W687

6 Esses et al. Fig year-old man who presented with fractured scapula secondary to trauma. and, Radiograph () and T scan () illustrate fracture (arrows, and )., 3 model was used to plan scapula reconstruction and to pinpoint optimal location for plate placement., Postoperative radiograph. ownloaded from by on 07/04/16 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with abdominal aortic aneurysm., Image shows 3 rendering of aneurysm derived from IOM-based T data., Photograph of rapid prototyped model., Model was brought into operating room to help orient surgeon performing stent procedure. Fig year-old man with coronary artery disease who was referred for coronary artery stent placement., Femoral approach was precluded by tortuous thoracic aorta, as seen in this 3 rendering., Photograph shows posterior view of T-derived rapid prototype model of left subclavian artery. Left-subclavian approach was also difficult because of artery s route. Model was brought into catheter laboratory to aid with orientation and facilitated catheterization. W688 JR:196, June 2011