Comparative Optics of the Surgical Microscope and Rigid Endoscopes in Neurosurgery.

This chapter is intended to provide a brief overview of the optics of surgical microscopes and rigid endoscopes, with the aim of providing the reader with the principles dictating the nature of surgical visualization when either of the visual control systems is used. It is not by any means geared toward elaborating on the detailed optical physics of these systems, which is beyond the scope and objective of this chapter.

The usefulness of intraoperative sodium fluorescein in the surgical treatment of relapsed high-grade brain tumors in pediatric patients.

PURPOSE: We report the usefulness of intraoperative sodium fluorescein (SF) in the surgical treatment of relapsed high-grade brain tumors in pediatric neurosurgery. METHODS: We describe our protocol for intraoperative SF and three cases of patients between 5 and 11 years diagnosed and surgically treated for relapsed high-grade brain tumors using SF. RESULTS: The 560-nm microscope filter enables the use of low doses of this fluorochrome. A dose of 3 mg/kg of patient weight of 10% SF, administered intravenously, is safe and effective in children. The effect of SF was immediate, providing a clear margin between the tumor and healthy tissue, which enabled good tumor resection. We observed no adverse effects in the postoperative period, and the patients evolved satisfactorily. CONCLUSIONS: To the best of our knowledge, we describe for the first time the use of fluorescein in reoperations of relapsed high-grade brain tumors in childhood with promising results. Using SF in children is a safe, affordable, and effective technique that offers an excellent intraoperative image, being a feasible option to improve oncological resection. This study is one of the few that uses SF in pediatric neurosurgery, where it could be very beneficial.

Root Canal Treatment of Oehlers Type III Dens Invaginatus in Maxillary Lateral Incisor and Remote Sinus Tract Using Dental Surgical Microscope and Cone-Beam Computed Tomography.

Dens invaginatus is a morphological abnormality of the tooth that results from a developmental anomaly during tooth formation, in which part of the enamel and dentin of the crown invaginates into the pulp cavity. This report describes a case of a maxillary lateral incisor with apical periodontitis apparently caused by Oehlers Type III dens invaginatus. The patient was a 69-year-old man who visited our clinic complaining of discomfort in the maxillary right lateral incisor. Cone-beam computed tomography (CBCT) revealed dens invaginatus of the maxillary lateral incisor and a sinus tract in the maxillary central incisor region, which was derived from apical periodontitis of the maxillary lateral incisor. The dens invaginatus was accompanied by a complex root canal morphology. Treatment, which was performed using a dental surgical microscope, had a favorable outcome. The patient remains in good condition at 1 year postoperatively.

Interdental Papillary Reconstruction by Microtunnelling Technique Using Autologous Biomatrices-A Randomised Controlled Clinical Trial.

Background and objectives: The study aimed to evaluate and compare the amount of papillary gain and black triangle height reduction after intervention with a microtunnelling technique with either Connective tissue graft (CTG) or Platelet-rich fibrin (PRF) as a biomatrix at 6 months using a microsurgical approach. Materials and Methods: Twenty-six patients with interdental papillary loss were included in the study. The patients were selected randomly for the study groups with thirteen patients in each group: a control group where CTG was utilised as a matrix, and a test group where PRF was utilised as a matrix, for interdental papillary reconstruction. A microtunnelling technique was performed for both the study groups under a surgical microscope. The primary parameters assessed were interdental Papillary height (PH) and Black triangle height (BTH) at baseline, with secondary parameters Visual analogue score by dentist (VAS-D) and patient (VAS-P) assessed at 6 months. Results: Both the control and test groups showed a significant reduction in BTH within their respective group at six months (p < 0.05). The gain in papillary height significantly improved only in the CTG group at 6 months. However, significant differences could not be demonstrated for any of the variables such as BTH (p value = 0.582) and PH (p-value = 0.892) between the study groups at 6 months. Conclusions: IDP reconstruction utilising a microtunnelling approach with CTG or PRF was successful without any significant differences between the groups for the parameters assessed at 6 months.

[Imaging quality of the robotic visualization 4K3D system and its application in microscopic vasectomy reversal in rats].

OBJECTIVE: To quantitatively assess the performance of the new robotic visualization system (Zeiss, KINEVO 900) in terms of visual imaging effect and evaluate its potential application in microscopic vasectomy reversal. METHODS: We made a parallel comparison between the effects of the plane and stereo visual images of KINEVO 900 and optical surgical microscopy (Zeiss, S7), and performed microscopic vasectomy reversal on the rat model using KINEVO 900. RESULTS: Compared with S7, KINEVO 900 provided an even longer working distance (200－625 mm), a 3－4 times larger effective field area and a 1.5－2 times deeper front depth of field with the same working distance of 200 mm. No statistically significant difference was observed in the average anastomosis time and immediate patency rate between the two platforms (P > 0.05). CONCLUSION: The 4K3D video image stream outputted by KINEVO 900 is not inferior to that of the optical surgical microscope represented by S7 and is sufficient for microsurgeries in urology and andrology. More prospective randomized clinical animal experiments are needed to further evaluate its application value in andrology.

Development and initial evaluation of a novel simulation model for comprehensive brain tumor surgery training.

BACKGROUND: Increasing technico-manual complexity of procedures and time constraints necessitates effective neurosurgical training. For this purpose, both screen- and model-based simulations are under investigation. Approaches including 3D printed brains, gelatin composite models, and virtual environments have already been published. However, quality of brain surgery simulation is limited due to discrepancies in visual and haptic experience. Similarly, virtual training scenarios are still lacking sufficient real-world resemblance. In this study, we introduce a novel simulator for realistic neurosurgical training that combines real brain tissue with 3D printing and augmented reality. METHODS: Based on a human CT scan, a skull base and skullcap were 3D printed and equipped with an artificial dura mater. The cerebral hemispheres of a calf's brain were placed in the convexity of the skullcap and tumor masses composed of aspic, water, and fluorescein were injected in the brain. The skullcap and skull base were placed on each other, glued together, and filled up with an aspic water solution for brain fixation. Then, four surgical scenarios were performed in the operating room as follows: (1) simple tumor resection, (2) complex tumor resection, (3) navigated biopsy via burr hole trepanation, and (4) retrosigmoidal craniotomy. Neuronavigation, augmented reality, fluorescence, and ocular-as well as screen-based (exoscopic)-surgery were available for the simulator training. A total of 29 participants performed at least one training scenario of the simulator and completed a 5-item Likert-like questionnaire as well as qualitative interviews. The questionnaire assessed the realism of the tumor model, skull, and brain tissue as well as the capability for training purposes. RESULTS: Visual and sensory realism of the skull and brain tissue were rated,"very good," while the sensory and visual realism of the tumor model were rated "good." Both overall satisfaction with the model and eligibility of the microscope and neurosurgical instruments for training purposes were rated with "very good." However, small size of the calf's brain, its limited shelf life, and the inability to simulate bleedings due to the lack of perfusion were significant drawbacks. CONCLUSION: The combination of 3D printing and real brain tissue provided surgical scenarios with very good real-life resemblance. This novel neurosurgical model features a versatile setup for surgical skill training and allows for efficient training of technological support like image and fluorescence guidance, exoscopic surgery, and robotic technology.

Sodium fluorescein-guided brain tumor surgery under the YELLOW-560-nm surgical microscope filter in pediatric age group: feasibility and preliminary results.

OBJECTIVE: To evaluate the feasibility and safety of sodium fluorescein (Na-Fl)-guided surgery with the use of the PENTERO 900 surgical microscope (Carl Zeiss, Meditec, Oberkochen, Germany) equipped with the YELLOW-560-nm filter and low-dose Na-Fl (2 mg/kg) in pediatric brain tumor surgery. METHODS: The study included 23 pediatric patients with various intracranial pathologies, who underwent Na-Fl-guided surgery between April 2015 and February 2018. Clinical features, surgical observations, extent of resection, and tumor histopathology were retrospectively analyzed. The use of YELLOW-560-nm filter was found "helpful" if the discrimination of the pinkish brain tissue and bright yellow stained tumor tissue was clear. Otherwise, it was described as "not helpful." RESULTS: There were 11 female and 12 male patients with a mean age of 9.4 years. There were 7 brain stem/tectal plate gliomas, 6 supratentorial tumors, 4 intraventricular tumors, 2 pineal tumors, 2 infratentorial tumors, 1 clivus tumor, and 1 tumor with supra- and infratentorial extensions in the current series. Na-Fl was found helpful by means of the tumor demarcation in 20 instances (87%). In 11 of these 20 operations (55%), a total resection was achieved regardless of the tumor pathology. A subtotal resection was achieved in the remaining 9 patients (45%). No adverse events or side effects were encountered with regard to Na-Fl use. CONCLUSION: Na-Fl guidance with the use of the YELLOW-560 filter is safe and effective during brain tumor surgery in pediatric age group.

Effectiveness of Scleral Buckling with a Wide-Field Surgical Microscope and Chandelier Illumination in Retinal Detachment Repair.

PURPOSE: To assess treatment efficacy of scleral buckling surgery with wide-field surgical microscope and 27-gauge (G) chandelier illumination for rhegmatogenous retinal detachment (RRD). METHODS: This study is a retrospective chart review of 29 eyes in 29 patients with RRD who underwent scleral buckling surgery with a wide-field surgical microscope and 27-G chandelier illumination fiber inserted into the sclera at the pars plana. Results are expressed as mean ± standard deviation. Data were analyzed using the paired sample t test. Statistical significance was considered if p value was less than 0.05. RESULTS: The mean age of patients was 43.5 ± 3.5 years, and the mean follow-up time was 10.4 ± 2.5 months. Retinal reattachment was achieved in 27 of 29 eyes at initial surgery. The mean best corrected visual acuity improved from 0.38 ± 0.29 (logMAR) preoperatively to 0.19 ± 0.21 at 6 months after surgery. Two eyes underwent vitrectomy with silicone oil tamponade because of development of proliferative vitreoretinopathy. There was no complication such as choroidal hemorrhage, hypotony, or vitreous herniation at the end of surgery. CONCLUSION: Scleral buckling with a wide-field surgical microscope and 27-G chandelier illumination has the advantage of offering exact identification of retinal tears and determination of the adequacy of buckle height and position in retinal detachment surgery compared to conventional scleral buckling surgery.

[The results of coronary artery bypass grafting by using of surgical microscope]. / Gospital'nye rezul'taty koronarnogo shuntirovaniia s ispol'zovaniem operatsionnogo mikroskopa.

AIM: To analyze own experience of coronary artery bypass grafting (CABG) using microsurgical technique and operating microscope. MATERIAL AND METHODS: There were 100 patients with coronary artery disease who underwent CABG in the Petrovsky Russian Research Center for Surgery for the period from April 2017 to December 2018. Mean age of patients was 59.7 ± 8.9 years. Triple-vessel disease was noted in 83 (83%) patients, two-vessel - in 17 (17%) patients. Stenosis of left main coronary artery was observed in 34 (34%) patients. On-pump myocardial revascularization using microsurgical technique was performed in all patients. RESULTS: A total of 360 distal anastomoses with coronary arteries were formed in 100 patients using surgical microscope. Revascularization index was 3.6 ± 0.8, mean CPB time - 104 ± 24 min, aoric cross-clamping time - 72 ± 16 min. In-hospital mortality was absent. There were no cases of resternotomy for bleeding, infectious complications of postoperative wounds. One (1%) patient had intraoperative myocardial infarction. CONCLUSION: CABG using microsurgical technique and operating microscope may be appropriate in patients with multiple-vessel coronary lesion and small diameter of coronary arteries.

[The results of coronary artery bypass grafting by using of surgical microscope]. / Rezul'taty koronarnogo shuntirovaniia s primeneniem operatsionnogo mikroskopa.

AIM: To present an experience of coronary artery bypass grafting (CABG) by using of surgical microscope in patients with coronary artery disease at Cardiac Surgery Department #2 (surgical treatment of myocardial dysfunction and heart failure) of Petrovsky Russian Research Center for Surgery. MATERIAL AND METHODS: There were 41 CABG procedures with surgical microscope. Indications for myocardial revascularization, surgical technique, intraoperative and postoperative complications are comprehensively described. RESULTS: CABG by using of surgical microscope is a successfully reproducible technique followed by good immediate outcomes.

Fluorescein sodium-guided resection of cerebral metastases-an update.

BACKGROUND: Cerebral metastasis (CM) is the most common malignancy affecting the brain. In patients eligible for surgery, complete tumor removal is the most important predictor of overall survival and neurological outcome. The emergence of surgical microscopes fitted with a fluorescein-specific filter have facilitated fluorescein-guided microsurgery and identification of tumor tissue. In 2012, we started evaluating fluorescein (FL) with the dedicated microscope filter in cerebral metastases (CM). After describing the treatment results of our first 30 patients, we now retrospectively report on 95 patients. METHODS: Ninety-five patients with CM of different primary cancers were included (47 women, 48 men, mean age, 60 years, range, 25-85 years); 5 mg/kg bodyweight of FL was intravenously injected at induction of anesthesia. A YELLOW 560-nm filter (Pentero 900, ZEISS Meditec, Germany) was used for microsurgical tumor resection and resection control. The extent of resection (EOR) was assessed by means of early postoperative contrast-enhanced MRI and the grade of fluorescent staining as described in the surgical reports. Furthermore, we evaluated information on neurological outcome and surgical complications as well as any adverse events. RESULTS: Ninety patients (95%) showed bright fluorescent staining that markedly enhanced tumor visibility. Five patients (5%); three with adenocarcinoma of the lung, one with melanoma of the skin, and one with renal cell carcinoma) showed insufficient FL staining. Thirteen patients (14%) showed residual tumor tissue on the postoperative MRI. Additionally, the MRI of three patients did not confirm complete resection beyond doubt. Thus, gross-total resection had been achieved in 83% (n = 79) of patients. No adverse events were registered during the postoperative course. CONCLUSIONS: FL and the YELLOW 560-nm filter are safe and feasible tools for increasing the EOR in patients with CM. Further prospective evaluation of the FL-guided technique in CM-surgery is in planning.

Unique migration of a dental needle into the parapharyngeal space: successful removal by an intraoral approach and simulation for tracking visibility in X-ray fluoroscopy.

OBJECTIVES: The first objective was to describe a novel case of migration of a broken dental needle into the parapharyngeal space. The second was to address the importance of simulation elucidating visualization of such a thin needle under X-ray fluoroscopy. METHODS: Clinical case records (including computed tomography [CT] and surgical approaches) were reviewed, and a simulation experiment using a head phantom was conducted using the same settings applied intraoperatively. RESULTS: A 36-year-old man was referred after failure to locate a broken 31-G dental needle. Computed tomography revealed migration of the needle into the parapharyngeal space. Intraoperative X-ray fluoroscopy failed to identify the needle, so a steel wire was applied as a reference during X-ray to locate the foreign body. The needle was successfully removed using an intraoral approach with tonsillectomy under surgical microscopy. The simulation showed that the dental needle was able to be identified only after applying an appropriate compensating filter, contrasting with the steel wire. CONCLUSION: Meticulous preoperative simulation regarding visual identification of dental needle foreign bodies is mandatory. Intraoperative radiography and an intraoral approach with tonsillectomy under surgical microscopy offer benefits for accessing the parapharyngeal space, specifically for cases medial to the great vessels.

Deep Learning-Assisted Segmentation and Classification of Brain Tumor Types on Magnetic Resonance and Surgical Microscope Images.

OBJECTIVE: The primary aim of this research was to harness the capabilities of deep learning to enhance neurosurgical procedures, focusing on accurate tumor boundary delineation and classification. Through advanced diagnostic tools, we aimed to offer surgeons a more insightful perspective during surgeries, improving surgical outcomes and patient care. METHODS: The study deployed the Mask R-convolutional neural network (CNN) architecture, leveraging its sophisticated features to process and analyze data from surgical microscope videos and preoperative magnetic resonance images. Resnet101 and Resnet50 backbone networks are used in the Mask R-CNN method, and experimental results are given. We subsequently tested its performance across various metrics, such as accuracy, precision, recall, dice coefficient (DICE), and Jaccard index. Deep learning models were trained from magnetic resonance imaging and surgical microscope images, and the classification result obtained for each patient was combined with the weighted average. RESULTS: The algorithm exhibited remarkable capabilities in distinguishing among meningiomas, metastases, and high-grade glial tumors. Specifically, for the Mask R-CNN Resnet 101 architecture, precision, recall, DICE, and Jaccard index values were recorded as 96%, 93%, 91%, and 84%, respectively. Conversely, for the Mask R-CNN Resnet 50 architecture, these values stood at 94%, 89%, 89%, and 82%. Additionally, the model achieved an impressive DICE score range of 94%-95% and an accuracy of 98% in pathology estimation. CONCLUSIONS: As illustrated in our study, the confluence of deep learning with neurosurgical procedures marks a transformative phase in medical science. The results are promising but underscore diverse data sets' significance for training and refining these deep learning models.

Medium-term Outcomes of Excision Using Surgical Microscope of Tenosynovial Giant Cell Tumors of the Hand.

BACKGROUND/AIM: The recurrence rate following the excision of tenosynovial giant cell tumors (TSGCT) of the hand is very high. Intraoperative application of a surgical microscope has been reported. However, to date, there are no reports of medium-term outcomes related to this technique. This study aimed to evaluate the medium-term outcomes of tumor excision using surgical microscope for TSGCT of the hand. PATIENTS AND METHODS: A total of 27 patients, who underwent an initial surgery for histologically-confirmed TSGCT of the hand, between 2008 and 2020, were included and evaluated. The mean follow-up time postoperatively was 6.8 years. Tumor recurrence and preoperative tumor characteristics were assessed. RESULTS: All tumors were adherent to tendons, tendon sheaths, neurovascular structures or periarticular ligaments and capsules. Bony lesions were observed in 11 tumors. The surgical microscope was used in 13 tumors. Recurrences were observed in three tumors (overall recurrence rate: 11%). Tumor characteristics were similar in both groups, but the recurrence rate in the group treated using the surgical microscope was 0%, whereas the recurrence rate in the group treated without the surgical microscope was 21%. Re-operations using the surgical microscope for recurrent tumors were performed, without recurrence postoperatively. CONCLUSION: Among patients with TSGCT of the hand treated with tumor excision using the surgical microscope, the postoperative recurrence rate was 0%. Based on the results of this study, the surgical microscope might be used for excision of TSGCTs of the hand.

A Tubular-Mounted Digital Camera Versus Optical Surgical Microscope for Minimally Invasive Lumbar Decompression Surgery: The Impact on Operative Times, Ergonomics, and Workflow.

OBJECTIVE: Understanding ergonomic impact is foundational to critically evaluating value and safety of enabling technologies in minimally invasive spine surgeries. This study assessed the impact of a tubular-mounted digital camera (TMDC) versus an optical surgical microscope (OSM) in single-level minimally invasive spine surgeries on operative times, durotomy rate, surgeon ergonomics, safety, and operating room workflow. METHODS: This retrospective study compared consecutive single-level minimally invasive lumbar decompression surgeries in a TMDC cohort (September 2021-June 2022) with an historical OSM cohort (January 2020-July 2021). Data included patient demographics, operative times, durotomy incidence, surgeon ergonomics (Rapid Entire Body Assessment scores), and equipment impact via staff surveys. Operative times were assessed by t test, while Pearson χ2 test compared sex. Age, body mass index, and Charlson Comorbidity Index comparisons were made by Wilcoxon rank sum tests, and survey results were analyzed with Wilcoxon signed rank tests. RESULTS: TMDC and OSM groups included 74 and 82 patients, respectively. Age, sex, and Charlson Comorbidity Index did not significantly differ between groups. The TMDC group had a higher body mass index (29.6 ± 5.1) than the OSM group (29.0 ± 7.5) (P = 0.04). The TMDC group had significantly shorter operative times (57.3 ± 16.6 minutes) than the OSM group) (66.7 ± 22.5 minutes) (P = 0.004), with no difference in durotomy rates (P = 0.42). TMDC use yielded lower Rapid Entire Body Assessment scores compared with OSM (4.1 ± 0.77) (P < 0.001). Surveys indicated improved safety, setup time, and workflow with TMDC (P < 0.001). CONCLUSIONS: TMDC in single-level minimally invasive lumbar decompression surgery improved surgeon ergonomics, reduced operative times, and maintained durotomy rates, enhancing operating room efficiency. Evaluating ergonomic impact of technology is vital for safety and value assessment.

A hyperspectral surgical microscope with super-resolution reconstruction for intraoperative image guidance.

Hyperspectral imaging (HSI) is an emerging imaging modality in medical applications, especially for intraoperative image guidance. A surgical microscope improves surgeons' visualization with fine details during surgery. The combination of HSI and surgical microscope can provide a powerful tool for surgical guidance. However, to acquire high-resolution hyperspectral images, the long integration time and large image file size can be a burden for intraoperative applications. Super-resolution reconstruction allows acquisition of low-resolution hyperspectral images and generates high-resolution HSI. In this work, we developed a hyperspectral surgical microscope and employed our unsupervised super-resolution neural network, which generated high-resolution hyperspectral images with fine textures and spectral characteristics of tissues. The proposed method can reduce the acquisition time and save storage space taken up by hyperspectral images without compromising image quality, which will facilitate the adaptation of hyperspectral imaging technology in intraoperative image guidance.

Functionality and Usability of the Exoscope in Microvascular Decompression for Hemifacial Spasm and Trigeminal Neuralgia.

BACKGROUND: Studies on the functionality and usability of the exoscope in neurosurgical procedures against surgical microscopes (SMs) are limited. This study aimed to examine the functionality and usability of the exoscope during microvascular decompression (MVD) surgery. METHODS: Seven neurosurgeons evaluated the usefulness of a 4 K, 3-dimension digital exoscope in MVD by answering a questionnaire. The questionnaire inquired about the functionality and usability of the exoscope by utilizing a visual analog scale (VAS; 1-10). A score of 5 on VAS was equivalent to the corresponding quality of the SM. The learning effect of the exoscope was evaluated using mean VAS scores in the first and last 3 cases for each neurosurgeon. RESULTS: The functionality of the exoscope in MVD was superior to that in SM (P < 0.001). In the last 3 surgeries, the mean VAS scores of the exoscope were excellent in terms of ease of arm handling, exchange of surgical instruments, ease of surgical procedure, and intraoperative physical stress. The mean VAS scores of the exoscope in intraoperative asthenopia were significantly higher than those of the SM (P < 0.001). No statistical significance was found in operation time, discharge outcome, and 1-year post-surgery outcome between MVD performed using the exoscope and SM. CONCLUSIONS: Neurosurgeons may experience reduced stress levels during MVD when using the exoscope. As the outcome of MVD using the exoscope did not demonstrate a statistical difference compared with MVD using the SM, the exoscope may prove to be a useful tool for performing MVD.

Preliminary Clinical Experience with a High-Definition Three Dimensional Exoscope for Spinal Surgery.

We retrospectively evaluated spinal surgeries performed using the high-definition three-dimensional exoscopic system, which became available at our institution in August 2020. Eleven patients (4 with cervical disease and 7 with lumbar disease) underwent surgery with the system. There were no surgical complications related to the system, and the results were satisfactory. The small, flexible camera of the exoscope allows the surgeon to view the surgical field from various angles, facilitating both the approach and technique. In addition, it allows the surgeon to operate in an upright position without strain on the head and neck. Although further surgical experience is needed, this system has the potential to improve the visualization of the surgical field in spinal surgery.

Intraoperative zoom lens calibration for high magnification surgical microscope.

BACKGROUND AND OBJECTIVES: An augmented reality (AR)-based surgical guidance system is often used with high-magnification zoom lens systems such as a surgical microscope, particularly in neurology or otolaryngology. To superimpose the internal structures of relevant organs on the microscopy image, an accurate calibration process to obtain the camera intrinsic and hand-eye parameters of the microscope is essential. However, conventional calibration methods are unsuitable for surgical microscopes because of their narrow depth of focus at high magnifications. To realize AR-based surgical guidance with a high-magnification surgical microscope, we herein propose a new calibration method that is applicable to the highest magnification levels as well as low magnifications. METHODS: The key idea of the proposed method is to find the relationship between the focal length and the hand-eye parameters, which remains constant regardless of the magnification level. Based on this, even if the magnification changes arbitrarily during surgery, the intrinsic and hand-eye parameters are recalculated quickly and accurately with one or two pictures of the pattern. We also developed a dedicated calibration tool with a prism to take focused pattern images without interfering with the surgery. RESULTS: The proposed calibration method ensured an AR error of < 1 mm for all magnification levels. In addition, the variation of focal length was within 1% regardless of the magnification level, and the corresponding variation with the conventional calibration method exceeded 20% at high magnification levels. CONCLUSIONS: The comparative study showed that the proposed method has outstanding accuracy and reproducibility for a high-magnification surgical microscope. The proposed calibration method is applicable to various endoscope or microscope systems with zoom lens.

Multi-Asymmetric Irradiation Method Using a Ring Array to Obtain an Emission-Capable LED Beam Power Effect to Observe Cancer Removal Status in a Surgical Microscope.

The light emitting diodes (LEDs) used in surgical fluorescence microscopes have weak power, to induce fluorescence emission. The LED induces fluorescence emission throughout a lesion due to its large beam width; however, the beam irradiation intensity is not uniform within the beam width, resulting in a fluorescence emission induction difference. To overcome this problem, this study proposes an asymmetric irradiation array for supplying power uniformly throughout the beam width of the LED and increasing the intensity of the LED. To increase the irradiation power of the LEDs, a multi-asymmetric irradiation method with a ring-type array structure was used. The LED consisted of eight rings, and the space between the LEDs, the placement position, and the placement angle were analyzed to devise an experimental method using 3D printing technology. To test the irradiation power of the LED, the working distance (WD) between the LED and target was 30 cm. The bias voltage of the LED for irradiating the light source was 5.0 V and the measured power was 4.63 mW. The brightness (lux) was 1153 lx. Consequently, the LED satisfied the fluorescence emission induction conditions. The diameter of the LED-irradiated area was 9.5 cm. Therefore, this LED could be used to observe fluorescent emission-guided lesions. This study maximized the advantages of LEDs with optimal conditions for fluorescence emission by increasing the beam width, irradiation area, and energy efficiency, using a small number of LEDs at the maximum WD. The proposed method, optimized for fluorescence expression-induced surgery, can be made available at clinical sites by mass producing them through semiconductor processes.