3D imaging
The word stereoscopy derives from Greek στερεός (stereos), meaning “firm, solid”, and σκοπέω (skopeō), meaning “to look, to see”.
Stereoscopy (also called stereoscopics or 3D imaging) is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision.
One of the primary restrictions of endoscopic or endoscope assisted surgery is the lack of binocular or stereoscopic vision. Monocular endoscopes and displays create a 2-dimensional (2-D) image that impairs depth perception, hand-eye coordination, and the ability to estimate size 1) 2).
Most stereoscopic methods present two offset images separately to the left and right eye of the viewer. These two-dimensional images are then combined in the brain to give the perception of 3D depth. This technique is distinguished from 3D displays that display an image in three full dimensions, allowing the observer to increase information about the 3-dimensional objects being displayed by head and eye movements.
Operating in a 2D environment requires surgeons to train their hand-eye coordination to respond to visual cues received by the interaction of the operative instruments with the environment to accurately understand the relative depth of structures in the 2-D projection. Surgeons will often move the endoscope in and out or side to side to gain a motion parallax depth cue. This lack of stereoscopic vision has contributed to the steep learning curve in the field of neuroendoscopy. The next obvious step in the evolution of minimal access endoscopic surgery is the development of high-definition stereoendoscopes that produce a 3-dimensional (3-D) image.
Although such stereoendoscopes exist their use in neurosurgery has been limited because of the larger diameter and poor resolution of earlier generations.
Neurosurgery and Stereoscopy
It is easy to make errors in estimating the exact size and positioning of neural structures, especially when only using tomographic methods, as a lot of imagination and little precision is required. Wu and Tang found that combining the use of sectional micro-anatomy and micro-stereoscopic anatomy is much more accurate. They believe that his study makes a significant contribution to the literature because they believe that using improved methods to examine the neural structure is vital in future research on the micro-stereoscopic brain anatomy 3)
In neurosurgery stereoscopy has been used very successfully to demonstrate microsurgical anatomy by Albert L. Rhoton and co-workers 4) and Shimizu et al in 2006 5) , explained the importance of 3D neuroanatomical imaging as a teaching tool in neurosurgical training and comprehensively described original techniques for their production.
The use of 3D imaging in neurosurgical training is not as widespread as it could be, partially due to the complexity of some techniques described in the past, the long preparation time in the pre- and post-operative phases and their interference with the operation, making it impractical in busy neurosurgical theatres.
Companies producing microscopes and endoscopes have developed integrated 3D technology making 3D recording and editing less complex, but these are still very expensive.
Abarca et al performed endoscopic dissection in cadaveric specimens fixed with formalin and with the Thiel technique, both prepared using the intravascular injection of colored material. Endonasal approaches were performed with conventional 2D endoscopes. Then they applied the 3D anaglyph technique to illustrate the pictures in 3D.
The most important anatomical structures and landmarks of the sellar region under endonasal endoscopic vision are illustrated in 3D images.
The skull base consists of complex bony and neurovascular structures. Experience with cadaver dissection is essential to understand complex anatomy and develop surgical skills. A 3D view constitutes a useful tool for understanding skull base anatomy 6).
Advantages
Used effectively, stereoscopic three-dimensional (3D) technologies can engage students with complex disciplinary content as they are presented with informative representations of abstract concepts. In addition, preliminary evidence suggests that stereoscopy may enhance learning and retention in some educational settings. Biological concepts particularly benefit from this type of presentation since complex spatially oriented structures frequently define function within these systems. Viewing biological phenomena in 3D as they are in real life allows the user to relate these spatial relationships and easily grasp concepts making the key connection between structure and function. In addition, viewing these concepts interactively in 3D and in a manner that leads to increased engagement for young prospective scientists can further increase the impact. We conducted two studies evaluating the use of this technology as an instructional tool to teach high school students complex biological concepts. The first study tested the use of stereoscopic materials for teaching brain function and human anatomy to four classes. The second study evaluated stereoscopic images to support the learning of cell structure and DNA in four different high school classes. Most important, students who used stereoscopic 3D had significantly higher test scores than those who did not. In addition, students reported enjoying 3D presentations, and it was among their top choices for learning about these complex concepts. In summary, our evidence adds further support for the benefits of 3D images to students’ learning of science concepts 7).
The teaching of neuroanatomy in medical education has historically been based on didactic instruction, cadaveric dissections, and intra-operative experience for students. Multiple novel 3-Dimensional (3D) modalities have recently emerged. Among these, stereoscopic anaglyphic video is easily accessible and affordable, however, its effects have not yet formally been investigated.
This study aimed to investigate if 3D stereoscopic anaglyphic video instruction in neuroanatomy could improve learning for content-naive students, as compared to 2D video instruction.
A single-site controlled prospective case control study was conducted at the School of Education. Content knowledge was assessed at baseline, followed by the presentation of an instructional neuroanatomy video. Participants viewed the video in either 2D or 3D format, then completed a written test of skull base neuroanatomy. Pre-test and post-test performances were analyzed with independent t-tests and ANCOVA.
249 subjects completed the study. At baseline, the 2D (n=124, F=97) and 3D groups (n=125, F=96) were similar, although the 3D group was older by 1.7 years (p=.0355) and the curricula of participating classes differed (p<.0001). Average scores for the 3D group were higher for both pretest (2D, M=19.9%, SD=12.5% vs. 3D, M=23.9%, SD=14.9%, p=.0234) and posttest (2D, M=68.5%, SD=18.6% vs. 3D, M=77.3%, SD=18.8%, p=.003), but the magnitude of improvement across groups did not reach statistical significance (2D, M=48.7%, SD=21.3%, vs. 3D, M=53.5%, SD=22.7%, p=.0855).
Incorporation of 3D video instruction into curricula without careful integration is insufficient to promote learning over 2D video 8).
Preoperative 3D imaging provides reliable and detailed information about the intraoperative anatomical relationship between the trigeminal nerve and the SPV. This evaluation is useful for preoperative planning 9).
O arm 3D imaging with stereotactic navigation may be used to localize lesions intraoperatively with real-time dynamic feedback of tumor resection.
Stereotactic guidance may augment resection or biopsy of primary and metastatic spinal tumors. It offers reduced radiation exposure to OR personnel as well as the ability to use minimally invasive approaches that limit tissue injury. Further work may be done to assess the utility of stereotactic image guidance in oncological tumor resection, particularly with respect to outcomes for patients 10).