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Although still experimental and expensive, 3D printed models have potential for use in preoperative planning in some settings.
Dr. AjaoThe first Nobel Prize was awarded for discovery of technology that would go on to revolutionize medical imaging. Since Wilhelm Roentgen’s discovery of the x-ray in 1895, innovation has continued to refine our glimpse into the human body.1 The next century saw the addition of computed tomography (CT), nuclear medicine, ultrasound and magnetic resonance imaging (MRI) to the physician’s tool box.2 These technologies have had an immeasurable impact on screening, diagnosis, image-guided procedures, obstetric care, and preoperative planning. Further advances have made it possible to generate 3-dimensional (3D) constructs from 2-dimensional images. That technology has been applied to other surgical disciplines and gynecologic surgeons have begun investigating the utility of 3D printing in perioperative planning.
How and why of 3D printing
Three-dimensional printing was first introduced in the 1980s, in engineering and manufacturing.3 Prototype generation quickly followed and commercial printers became available by the 1990s. The earliest methods of 3D printing involved subtractive techniques (i.e., chipping away at a solid material to leave the desired product) whereas newer technology allows for additive printing (i.e., sequential deposition of layers of material.) The process of converting a radiographic image to a tangible model is complicated and involves several steps. For 3D printing, CT or MRI scan slices often need to be thinner than usual to optimize the model. Slices too thick will lead to loss of fine details while very thin slices require significant modification. These details necessitate a constant discussion between the clinician, radiologist and engineers. Three-dimensional printers do not recognize the standard mode of medical imaging storage, DICOM (Digital Imaging and Communications in Medicine), and require conversion to a recognizable format, a process known as segmentation. The new format, STL (Standard Tessellation Language), can then be recognized by the printers. Some post-processing can still be performed, such as artifact removal, hollowing lumen, smoothing, etc. with communication between the engineers and medical team. After details, such as material and color are selected, an STL file is then printed, generating the model (Figure 1).
Commercially, with decreasing cost and improving technology, 3D printing continues to gain momentum and a wide array of products have been printed (clothing, weapons, car parts, toys, jewelry). Medical applications include printing of surgical instruments, organ scaffolds, prostheses, and complex organ reconstruction for perioperative purposes. Three-dimensional printing is in use for patient care in all surgical fields as well as dentistry.4-13
3D printing in gynecology
In terms of technology adoption life cycle, gynecologic surgery appears to fall into the late majority or laggards category as opposed to early adopters like the field of dentistry. In 2015, Yoong et al14 reported their application of 3D printing in ob/gyn with a report of a 10-cm broad ligament hematoma following cesarean section with known extension of the hysterotomy. The model was generated from pelvic MRI and demonstrated the spatial relationship of the hematoma to the surrounding pelvic structures. The authors suggested that 3D printing has the potential to augment team-based surgical planning and patient education.
In 2017, Bartellas et al15 reported creation of a 3D printed realistic hemorrhagic cervical cancer model. Historical cervical cancer models were used rather than actual patient images. Computer-aided design models were generated, which were in turn converted to STL files and subsequently sent to 3D printers. Simulation make-up was then applied to the 3D printed models and ob/gyn residents underwent simulation training with the cervices. Participants completed a post-simulation survey assessing accuracy, realism and value in education. The models were judged to be realistic and rated highly in simulation value.
Modeling in gynecologic surgery
Two studies describe use of a 3D printed model specifically for gynecologic surgery. The first study, by Aluwee,16 reported on preoperative 3D printing of five uteri with endometrial cancer. STLs were generated from MRI images with 3D models subsequently printed. CT images of the generated models were compared to the patient MRIs and compared quantitatively. Surgeons found the slight measurable errors to be acceptable and the models to be useful for preoperative planning. Both surgeons and patients found the 3D models to be an effective tool for patient education.
In 2017, Ajao et al17 described reconstruction of a deep infiltrating endometriosis nodule involving the posterior uterine wall and rectum in a 49-year-old patient. A 3-Tesla magnet was used to acquire an MRI image of the pelvis, including 3D images capturing 1-mm image slices. The stored DICOM files were then converted to STL files. A representative 3D model was then generated. The patient underwent a total laparoscopic hysterectomy, left salpingo-oophorectomy, right salpingectomy, and resection of endometriosis. Intraoperatively, the patient’s uterus was normal size, but her left ovary was adherent to the pelvic sidewall. Intraoperatively, a 2- to 3-cm rectovaginal nodule was encountered, corresponding to the lesion noted on the 3D printed model. Because of logistics associated with timing of MRI to model availability, the model was not available prior to surgery and was retrospectively compared to the intraoperative findings. The model was concordant with the intraoperative finding in regard to nodule location and topographical relation to surrounding structures (See figure 3A-C). The authors theorize that 3D printing for deep infiltrating endometriosis could prove to be a beneficial adjunct to established preoperative imaging modalities.
As in other surgical fields, 3D printing in gynecologic surgery has the potential to impact preoperative planning and surgical decision-making, patient education and counseling, and resident/fellow education. There are several limitations that will likely impede the widespread adoption of this technology into gynecologic surgery in its current iterations. The current cost per model averages $1500.17 Further studies are needed to establish the clinical benefits of use of 3D printing in gynecologic surgery. Given the lack of evidence to justify its use and until the price per model is significantly reduced, established imaging modalities such as pelvic ultrasound and MRI will continue to be the standard of care. In addition, because use of 3D printing in gynecologic surgery remains investigational and subject to approval by institutional review boards, insurance coverage for the technology can be expected to be several years away.
What the future holds
For select cases of deep infiltrating endometriosis affecting multiple organ systems (gynecologic, urinary, alimentary tracts), a multidisciplinary surgical team might find 3D modeling useful for patient-specific preoperative planning and for counseling a patient regarding the extent of surgical resection and need for stents or stoma, etc. Other potential applications for 3D printing in gynecologic surgery include myomectomies and surgery for certain Müllerian abnormalities. With tactile feedback a limitation of laparoscopic or robotic myomectomy, smaller fibroids might be inadvertently retained during these procedures. Three-dimensional models of the uterus with varying color and consistency might aid in a more thorough procedure. In addition, a tangible model in complex multiple myomectomy cases might inform the optimal location of hysterotomies, thereby limiting unnecessary and inefficient incisions. Women with Müllerian anomalies in whom a hysterectomy is indicated often undergo preoperative MRI as part of gynecologic and urologic system evaluation. Three-dimensional rendering of anomalies involving the lower uterine segment or cervix (didelphys, bicollis, complete septate uterus, cervical agenesis, etc.) might more precisely delineate the relationship of the uterine vasculature and ureters to the uterus.
As enticing as it may be to use 3D printing for patient education, the current price of a model does not support that as the only indication for the technology. With continued innovation and evolution in the field of 3D printing, the cost of printers, and the process of image to model is expected to continue to decline to a more affordable level. As the paths of affordability and further research studies cross, clinical benefits of 3D printing in the field of gynecologic surgery may one day be clarified, making this exciting technology a new and permanent addition to the surgeon’s armamentarium.
Disclosures: The author reports no potential conflicts of interest with regard to this article.
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