Microscopes and Endoscopes in Neurosurgery.pptx

history, working, optics and salient features of operating microscopes in neurosurgery and endoscope. role of endoscopes in various surgeries and newer prospects of both microscopes and endoscopes

1. Microscopes and Endoscopes i n Neurosurgery Presented by:- Dr Rahul Jain SR-2 Neurosurgery Moderated By:- Dr V. C. Jha Dr Nitish Kumar Dr Gaurav Verma

2. THE OPERATING MICROSCOPE

3. History The first described use of a microscope within the operative theatre was in 1686 by Giuseppe Campani , who used a compound microscope to examine wounds and scar tissue. The use of magnification in surgery began in earnest in the second half of the 19th century with the development of loupe spectacles. Surgical binocular microscope first used by Carl Nylen in 1929 for middle ear surgery. In 1957, Theodore Kurze became the first neurosurgeon to use the microscope in removal of a neurilemmoma of the seventh nerve from a 5 year old boy.

4. In 1958, R.M.P. Donaghy established the first microneurosurgical training laboratory where several neurosurgeons like M Gazi Yasargil also trained. Yasargil made several revolutionary improvements in the design of the operating microscope and is regarded as the “Father Of Microneurosurgery ” for his contributions . Julius H. Jacobson wanted to allow a second surgeon to assist him while using magnification aids during the surgery .  Jacobson contacted Carl Zeiss, Inc., and in 1964, Dr. Littman designed a microscope for Jacobson by adapting beam-splitter technology. This microscope was named the “ Diploscope ”

5. Optical principles Magnification dependent on the magnification of the objective and eyepiece a zoom system of lenses is interposed between these two principal lenses allowing continuous change in magnification The field of view changes with the magnification according to the formula Diameter of field = 200/total magnification

6. 3. Depth of field is also an important parameter which is a measure of field of vision in a stereoscopic system . The depth of field increases with the square of the focal length of the objective lens decreases linearly with the magnification of the microscope . 4. Working distance of a surgical microscope gives a surgeon space to handle surgical instruments. The working distance of the first monocular microscope was 60 mm, and the first binocular microscope had a working distance of 75 mm. Zeiss OPMI 1 came out in 1953 and had a working distance of 100 to 405  mm. Since then, working distance has been improving to meet the need of different types of surgeries varying from 200 to 500  mm.

7. Components surgical microscope can be roughly divided into a microscope body, a light source, and a supporting structure. The microscope body has all the high-precision optics that provide a clear magnified image with the minimum distortion The binoculars mounted on the microscope head offer stereopsis. Multiple optical ports are open for adaptation of imaging devices such as video cameras or for assistants to share the identical FOV.

8. The light source is installed away from the microscope to avoid heating the microscope optics or the surgical site. Based on the configuration, there are four types of surgical microscopes: ( i ) on casters, (ii) wall mounted, (iii) table top, and (iv) ceiling mounted . The on-caster stand is the most popular supporting structure due to its better mobility, but a ceiling mount or wall mount can help with space management.

9. A. Optical System main determinant of the imaging quality that a system can achieve Basically a binocular (with eyepieces on top) with a close-up lens, namely the optical components including the objective lens and the magnification changer (or zoom changer ). T otal magnification ( M total ) of a surgical microscope is determined by all the four optical components in the microscope, namely the focal length of the objective lens (F OBJ ), zoom value (M ZOOM ), the focal length of binocular (F TUBE ), and the magnifying power of eyepieces (M EP )

10. Resolution measures the acuity improved by magnification. It is the ability of an optical system to distinguish two separate entities. Human eyes have an inherent resolution of 0.2  mm but with  20×  magnification, it can be increased to 0.01  mm. The design of optics is vital to the image quality of a surgical microscope. Aberration is an inherent property of optical systems, and it causes the blur or distortion of images, which is adverse to the desire for a clear view A pochromatic lens – developed by Ernst Abbe, a physicist hired by Carl Zeiss, not only corrects for two wavelengths (red and blue) to reduce spherical aberration but also utilizes the exceptional quality optical materials that have unusual and desirable characteristics to reduce chromatic aberration for three wavelengths (red, green, and blue ).

11. Focusing i s essential for a clear view . Depends on many factors such as quality of optical design, the size of objective lens aperture, magnification of the object, and it is reciprocal of the resolution. Parfocal , which means an optical system can stay in focus even with magnification changes.

12. B. Illumination System The original illuminator in the earliest surgical microscopes was an independent bulb externally mounted on the side of the microscope . Modern microscopes have adopted high-power light sources with stable light intensity and close-to-sunlight color temperature. With the built-in coaxial illuminator, light is rerouted to the viewing axis and projected down through the objective lens.

13. LED can provide illumination in the visible wavelength range with good brightness, good stability, longer life, less power consumption, and extremely low heat ; disadvantages : the higher color temperature and narrower wavelength range make the light not as close to sunlight; its spectrum is insufficient for fluorescence-guided applications especially ICG imaging. Automatic adjustment of light collimation in modern microscopes allows appropriate illumination as the magnification is varied . Auxiliary illumination In some advanced models auxiliary illumination is being used to decrease shadowing when changing the viewing angle.

14. In some contemporary surgical microscopes, small angle illumination ( SAI ), provides a concentrated and evenly distributed light beam, a bright view, and an improved depth perception, the shadow that appears at the edge of the viewing field is significantly reduced . Light management -irradiance (irradiation of a surface, W/m2) of a microscope light source increases with decreasing spot size and decreasing working distance.

15. C. Mechanical System and Automation  Mechanical stability is the second most important criterion in selecting a surgical microscope . The drift or vibrating of a microscope after positioning distracts surgeons’ focus on the surgical site. Microscope draping is a necessary requirement for sterilization in the OR. Modern surgical microscopes have made it an easy and time-saving process to balance. All six axes can get fully balanced with two pushes of a button, and intraoperative rebalance can be quickly and accurately accomplished with a single push of button on handgrip.

16. Robotic visualization system, two robotic positioning features, namely “point lock” and “position memory” With “ point lock ,” the microscope head stays in focus when being manually or automatically moved during surgery , “ Position memory ” makes the system able to “bookmark” positions and transit quickly and smoothly back to these positions with no need to rediscover . Ergonomics guarantees a comfortable and flexible working position; maneuverability is valued for the simplification of microscope operations.

17. D. Visualization System Microscope head usually has one main observation port and one rear or lateral port for co-observers. Stereopsis is a key feature of binocular surgical microscopes. The depth information can aid the detection of diagnostically relevant shapes, orientations, and positions of anatomical features, especially when monocular cues are absent or unreliable. A screen can show not only the white-light image of the surgical site but also other images, such as intraoperative OCT images, for surgical guidance.

18. The images can be shown separately, overlaid on the white-light image, or even in picture-in-picture endoscopic assistance view for endoscopic microinspection tools.

19. Application of microscope in neurosurgery Role of microscope in improving surgical outcomes first demonstrated in Acoustic Neuromas. Now routinely used in almost all intradural operative procedures whether in the brain or spine. Its use has resulted in smaller wounds, less postoperative neural and vascular damage, better hemostasis , more accurate nerve and vessel repairs, and surgical treatment of some previously inoperable lesions

20. It has improved operative results by permitting neural and vascular structures to be delineated with greater visual accuracy deep areas to be reached with less brain retraction and smaller cortical incisions bleeding points to be coagulated with less damage to adjacent neural structures, nerves distorted by tumor to be preserved with greater frequency enabling anastomosis and suturing of small vessels and nerves not previously possible to be performed.

21. Endoscopes

22. Neuroendoscopy Introduction of endoscope was undoubtedly a great advancement in neurosurgery. It minimises trauma to the brain tissue and maximises the vision around the remote areas. The access to the ventricle and cisterns has become much easier. Development in optics, lenses, long and angled instruments made the endoscopy in neurosurgery very versatile.

23. History

24. early 1970s, both flexible fibreoptic and high-resolution rigid endoscopes. At the initial days of neuroendoscopy , as ventricles contain the ideal medium of crystal-clear CSF, the endoscopic procedures were confined to those . Currently, the field of neuroendoscopy has extended beyond ventricular procedures and is currently applied for all types of neurosurgically treatable diseases such as intracranial cysts, intraventricular tumors , hypothalamic hamartoma (HH), skull base tumors , craniosynostosis , degenerative spine disease, and rare subtypes of hydrocephalus.

25. Equipment include : video camera, camera control units, light source, video recorder, video monitor and a computerized system for storage of video segments or single-picture capture With the fixation arms, sudden movement of the hand or hand tremor can be minimized.

26. instruments include a pair of grabbing forceps and scissors, a monopolar or bipolar coagulation device, an irrigation system, and a straight and one or more scopes with various angles. Straight and angled scopes Light source Endoscopic microsurgery instruments Flexible endoscope

27. Frameless computerized neuronavigation has been used more in intracranial endoscopic neurosurgery to increase the accuracy and precision. Modern three-chip technology provides impressive color depth and brilliant red differentiation. The latest Full HD technology delivers lag-free images even with rapid camera movements . improved maneuverability of the scope by reduction of the bulk and integration of the camera and fiberoptic light components with an extensive viewing angle from 0 to 70 degrees, along with the provision of maintaining surgical orientation.

28. Endoscopic third ventriculostomy

29. Endoscope-assisted microsurgery most rapidly growing area in endoscopic neurosurgery . allows the neurosurgeon to view tumor remnants such as those hidden behind eloquent brain tissue, a cranial nerve, or the tentorial edge. Rigid endoscopes with various angles and flexible endoscopes help the surgeon to look around the remote corners which can be very useful in the removal of tumors and the clipping of cerebral aneurysms.

30. Endoscopes are increasingly used to inspect tumors , tumor beds following resection, aneurysms and other pathologies . Risks - the most problematic of which of using the scope is the risk of friction upon structures while introducing the scope . If the scope is not fixed, then small, barely noticeable movements at the tip can be the result of larger excursions at the back of the scope.

31. Endoscopy for skull base lesions P ioneering work of neuroendoscopy for skull base tumors was done by Carrau and colleagues in 1996, who reported their original experience of endonasal transsphenoidal hypophysectomy at the University of Pittsburgh. The endoscopic approach was expanded by de Divitiis and colleagues to include other lesions of the sellar and parasellar regions in their study in 2002.

32. The bilateral endonasal endoscopic approach now allows for visualization of tumors at the anterior skull base up to the crista galli and down to the level of C2 Application - pituitary adenoma and craniopharyngioma Supradiaphragmatic lesions can be removed via the endonasal route suprasellar prechiasmatic preinfundibular lesions can be removed with the transtuberculum-transplanum sphenoidale approach

33. Endoscopic application in aneurysm surgery Endoscope can be used in and around the operative field of aneurysms easier and safer. Furthermore , the endoscope facilitates confirmation of optimal clip positions. Chowdhury et al. in 2012, the variations were identified and the authors concluded endonasal extended transsphenoidal approach can fully expose CW with brain in situ to observe the circle for variations and asymmetry.

34. Taniguchi et al. in 1999, reported in their series of 54 cases, the endoscope was used for further clarification of the detailed additional anatomy in 9 cases (16.7%). The surgeons reapplied the clip on the basis of endoscopic information which was gained after the initial clipping in 5 cases (9.3 %). In general, very large and giant aneurysms gain fewer benefits from the endoscope than smaller ones in the same location, because the mass of the lesion compromises insertion and fixation of the endoscope in the operative field. The endoscope is especially useful in the treatment of deeply located cerebral aneurysm . The effectiveness of the endoscope is limited for superficially located aneurysms like middle cerebral artery aneurysms and distal aneurysms such as pericallosal aneurysms

35. Microvascular decompression Endoscopic techniques such as endoscopic or endoscope-assisted MVD (EMVD) have been used for MVD operations. Though many neurosurgeons do not find EMVD is superior to MMVD as the access for MMVD can be small and the offending vessels can be separated easily through that. several authors indicated the superior efficacy of endoscopic or endoscope assisted surgery in locating the offending site of neurovascular conflict when compared with the microscopic surgery 

36. Regarding TN ,  SCA usually runs medial to the trigeminal nerve and the nerve can be compressed in a rostromedial direction. An approach with the thirty degree endoscope through the lateral tentorial surface of the cerebellum via a keyhole provides excellent exposure of the trigeminal nerve from the REZ to the Meckel’s cave . For HFS , the REZ of the facial nerve is located immediately medial to cranial nerve VIII in the supraolivary fossette , often compressed by the AICA from a caudal direction. 30  or 45  view of endoscopes through the petrosal surface of the cerebellum via a retrosigmoid keyhole clearly demonstrates the neurovascular structures, AICA can be transposed caudally and fixed at the petrosal dura mater.

37. In the meta-analysis by Li et al., it is shown that, EMVD was superior considering the perioperative safety as with less perioperative complications. Facial paralysis was significantly low in EMVD, and CSF leak and dysaudia (defective articulation stemming from auditory disability) also showed a similar trend with the previous discussions.

38. Evacuation of ICH: endoscopic and endoscope-assisted Endoscope-Assisted Evacuation describes the creation of a small craniotomy or craniectomy with stereotactic introduction of a port or sheath to the hematoma. It is followed by evacuation with the endoscope and a suction device or a combination device where the suction device is there side by side in the lumen of the sheath which is even less traumatic . Endoscopic evacuation is one of the earliest studies to investigate active MIS ICH evacuation using only endoscopes.

39. Newer prospects Intraoperative flourescence It is an upcoming technique available in several advanced micrscopes . applicable in aneurysm and tumour surgery where it allows the visualisation of sub millimeter vessels by the use of Indo- cyanin green dye used as fluorescing agent.

40. The detection module (blue) and the illumination model (yellow) are attached to the Zeiss Pentero OPMI head and can be used without affecting the standard operation of the microscope

41. 2. Augmented Reality AR is an immersive environment that contains real and computer-generated elements. AR can be very helpful with preoperative planning and intraoperative surgical navigation. It provides the visualization of anatomical structures beneath human skin intraoperatively by overlaying segmented preoperative images to the corresponding area on the human body . There are three core components of AR. First one is a virtual image or environment, which refers to the computer-generated 3D reconstruction. other two are the registration of the virtual environment with real space, and the display technology to combine the virtual and real environment, respectively.

42. 3. Laser Speckle Contrast Imaging for real-time assessment of perfusion . backscattered light from a scattering medium that is illuminated by coherent light forms a random interference pattern, namely the speckle pattern . When illuminating tissue with a coherent laser and acquiring images of the tissue with adequate exposure time, the movement of red blood cells can cause fluctuation in speckle patterns, thus the blurring of the images can be related to the blood flow. This blurring of the recorded pattern is used to calculate the speckle contrast, which is useful for the quantitative analysis of blood flow . fast and full-field, providing a 2D perfusion map without scanning.

43. SurgeON System has imaging specifications that are suitable for neurosurgery Comparing LSCI with ICG video angiography, this study demonstrated that the dye-free LSCI could not only provide more information such as the CBF variation but also guide the surgery in real-time.

44. C onclusion In conclusion, the surgical microscope and endoscope are powerful tools that can offer optional magnifications, bright illumination, and clear visualization. used in different types of surgeries and has improved surgical outcomes as well as surgeons’ ergonomics. It is anticipated that the integration of surgical microscopes and endoscopes with state-of-the-art optical imaging technologies will change the clinical practice in the operating room and benefit patients

45. References Youman and winns neurological surgery 8 th ed Ali Kawsar K. Endoscopy in Neurosurgery [Internet]. Frontiers in Clinical Neurosurgery. IntechOpen ; 2021 Uluç , K., Kujoth , G. C., & Başkaya , M. K. (2009). Operating microscopes: past, present, and future.  Neurosurgical Focus FOC ,  27 (3), E4 Ling Ma  and Baowei Fei . Comprehensive review of surgical microscopes: technology development and medical applications. J Biomed Opt. 2021 Jan; 26(1): 010901 Luigi   Rigante et al. Cleveland Clinic Journal of Medicine October 2019, 86 (10)  16ME-24ME Carl zeiss kinevo 900 brochure