Multimodal feedback systems for smart laser osteotomy: Depth control and tissue differentiation.

OBJECTIVES: The study aimed to improve the safety and accuracy of laser osteotomy (bone surgery) by integrating optical feedback systems with an Er:YAG laser. Optical feedback consists of a real-time visual feedback system that monitors and controls the depth of laser-induced cuts and a tissue sensor differentiating tissue types based on their chemical composition. The developed multimodal feedback systems demonstrated the potential to enhance the safety and accuracy of laser surgery. MATERIALS AND METHODS: The proposed method utilizes a laser-induced breakdown spectroscopy (LIBS) system and long-range Bessel-like beam optical coherence tomography (OCT) for tissue-specific laser surgery. The LIBS system detects tissue types by analyzing the plasma generated on the tissue by a nanosecond Nd:YAG laser, while OCT provides real-time monitoring and control of the laser-induced cut depth. The OCT system operates at a wavelength of 1288 ± 30 nm and has an A-scan rate of 104.17 kHz, enabling accurate depth control. Optical shutters are used to facilitate the integration of these multimodal feedback systems. RESULTS: The proposed system was tested on five specimens of pig femur bone to evaluate its functionality. Tissue differentiation and visual depth feedback were used to achieve high precision both on the surface and in-depth. The results showed successful real-time tissue differentiation and visualization without any visible thermal damage or carbonization. The accuracy of the tissue differentiation was evaluated, with a mean absolute error of 330.4 µm and a standard deviation of ±248.9 µm, indicating that bone ablation was typically stopped before reaching the bone marrow. The depth control of the laser cut had a mean accuracy of 65.9 µm with a standard deviation of ±45 µm, demonstrating the system's ability to achieve the pre-planned cutting depth. CONCLUSION: The integrated approach of combining an ablative laser, visual feedback (OCT), and tissue sensor (LIBS) has significant potential for enhancing minimally invasive surgery and warrants further investigation and development.

Towards phase-sensitive optical coherence tomography in smart laser osteotomy: temperature feedback.

Thermal effects during bone surgery pose a common challenge, whether using mechanical tools or lasers. An irrigation system is a standard solution to cool the tissue and reduce collateral thermal damage. In bone surgery using Er:YAG laser, insufficient irrigation raises the risk of thermal damage, while excessive water lowers ablation efficiency. This study investigated the potential of optical coherence tomography to provide feedback by relating the temperature rise with the photo-thermal expansion of the tissue. A phase-sensitive optical coherence tomography system (central wavelength of λ=1.288 µm, a bandwidth of 60.9 nm and a sweep rate of 104.17 kHz) was integrated with an Er:YAG laser using a custom-made dichromatic mirror. Phase calibration was performed by monitoring the temperature changes (thermal camera) and corresponding cumulative phase changes using the phase-sensitive optical coherence tomography system during laser ablation. In this experiment, we used an Er:YAG laser with 230 mJ per pulse at 10 Hz for ablation. Calibration coefficients were determined by fitting the temperature values to phase later and used to predict the temperature rise for subsequent laser ablations. Following the phase calibration step, we used the acquired values to predict the temperature rise of three different laser-induced cuts with the same parameters of the ablative laser. The average root-mean-square error for the three experiments was measured to be around 4 °C. In addition to single-point prediction, we evaluated this method's performance to predict the tissue's two-dimensional temperature rise during laser osteotomy. The findings suggest that the proposed principle could be used in the future to provide temperature feedback for minimally invasive laser osteotomy.

Real-time closed-loop tissue-specific laser osteotomy using deep-learning-assisted optical coherence tomography.

This article presents a real-time noninvasive method for detecting bone and bone marrow in laser osteotomy. This is the first optical coherence tomography (OCT) implementation as an online feedback system for laser osteotomy. A deep-learning model has been trained to identify tissue types during laser ablation with a test accuracy of 96.28 %. For the hole ablation experiments, the average maximum depth of perforation and volume loss was 0.216 mm and 0.077 mm3, respectively. The contactless nature of OCT with the reported performance shows that it is becoming more feasible to utilize it as a real-time feedback system for laser osteotomy.

Deep-Learning-Based Fast Optical Coherence Tomography (OCT) Image Denoising for Smart Laser Osteotomy.

Laser osteotomy promises precise cutting and minor bone tissue damage. We proposed Optical Coherence Tomography (OCT) to monitor the ablation process toward our smart laser osteotomy approach. The OCT image is helpful to identify tissue type and provide feedback for the ablation laser to avoid critical tissues such as bone marrow and nerve. Furthermore, in the implementation, the tissue classifier's accuracy is dependent on the quality of the OCT image. Therefore, image denoising plays an important role in having an accurate feedback system. A common OCT image denoising technique is the frame-averaging method. Inherent to this method is the need for multiple images, i.e., the more images used, the better the resulting image quality. However, this approach comes at the price of increased acquisition time and sensitivity to motion artifacts. To overcome these limitations, we applied a deep-learning denoising method capable of imitating the frame-averaging method. The resulting image had a similar image quality to the frame-averaging and was better than the classical digital filtering methods. We also evaluated if this method affects the tissue classifier model's accuracy that will provide feedback to the ablation laser. We found that image denoising significantly increased the accuracy of the tissue classifier. Furthermore, we observed that the classifier trained using the deep learning denoised images achieved similar accuracy to the classifier trained using frame-averaged images. The results suggest the possibility of using the deep learning method as a pre-processing step for real-time tissue classification in smart laser osteotomy.

Syndrome of ventricular septal defect and aortic regurgitation - A 22-year review of its management

Abstract Introduction: The presence of aortic regurgitation (AR) in the setting of ventricular septal defect (VSD) has always been a management challenge. Methods: This is a retrospective study looking at patients who underwent VSD closure with or without aortic valve intervention between January 1st, 1992 and December 31st, 2014 at the Institute Jantung Negara. This study looked at all cases of VSD and AR, where AR was classified as mild, moderate, and severe, the intervention done in each of this grade, and the durability of that intervention. The interventions were classified as no intervention (NI), aortic valve repair (AVr), and aortic valve replacement (AVR). Results: A total of 261 patients were recruited into this study. Based on the various grades of AR, 105 patients had intervention to their aortic valve during VSD closure. The rest 156 had NI. All patients were followed up for a mean time of 13.9±3.5 years. Overall freedom from reoperation at 15 years was 82.6% for AVr. Various factors were investigated to decide on intervening on the aortic valve during VSD closure. Among those that were statistically significant were the grade of AR, size of VSD, age at intervention, and number of cusp prolapse. Conclusion: We can conclude from our study that all moderate and severe AR with small VSD in older patients with more than one cusp prolapse will need intervention to their aortic valve during the closure of VSD.

Long-range optical coherence tomography with extended depth-of-focus: a visual feedback system for smart laser osteotomy.

This work presents a long-range and extended depth-of-focus optical coherence tomography (OCT) system using a Bessel-like beam (BLB) as a visual feedback system during laser osteotomy. We used a swept-source OCT system (λ c = 1310 nm) with an imaging range of 26.2 mm in the air, integrated with a high energy microsecond Er:YAG laser operating at 2.94 µm. We demonstrated that the self-healing characteristics of the BLB could reduce the imaging artifacts that may arise during real-time monitoring of laser ablation. Furthermore, the feasibility of using long-range OCT to monitor a deep laser-induced incision is demonstrated.

Syndrome of Ventricular Septal Defect and Aortic Regurgitation - A 22-Year Review of its Management.

INTRODUCTION: The presence of aortic regurgitation (AR) in the setting of ventricular septal defect (VSD) has always been a management challenge. METHODS: This is a retrospective study looking at patients who underwent VSD closure with or without aortic valve intervention between January 1st, 1992 and December 31st, 2014 at the Institute Jantung Negara. This study looked at all cases of VSD and AR, where AR was classified as mild, moderate, and severe, the intervention done in each of this grade, and the durability of that intervention. The interventions were classified as no intervention (NI), aortic valve repair (AVr), and aortic valve replacement (AVR). RESULTS: A total of 261 patients were recruited into this study. Based on the various grades of AR, 105 patients had intervention to their aortic valve during VSD closure. The rest 156 had NI. All patients were followed up for a mean time of 13.9±3.5 years. Overall freedom from reoperation at 15 years was 82.6% for AVr. Various factors were investigated to decide on intervening on the aortic valve during VSD closure. Among those that were statistically significant were the grade of AR, size of VSD, age at intervention, and number of cusp prolapse. CONCLUSION: We can conclude from our study that all moderate and severe AR with small VSD in older patients with more than one cusp prolapse will need intervention to their aortic valve during the closure of VSD.

Delayed Presentation of Posttraumatic Diaphragmatic Hernia Masquerading as Recurrent Acute Asthmatic Attack.

Diaphragmatic hernia following blunt abdominal injury is extremely rare and often diagnosed late. Missed diagnosis is also common with this condition. We herein present a delayed presentation of diaphragmatic hernia following blunt abdominal injury that was initially misdiagnosed as recurrent acute asthmatic attack due to repeated presentation with episodic difficulty in breathing.

Coarctation of aorta repair at the National Heart Institute (1983-1994).

This retrospective study illustrates our approach to this problem over the years, from performing subclavian flap aortoplasty initially to the more accepted procedure now, which is resection and end-to-end anastomosis. Coarctation of aorta in our population is seen in a varying age groups and are also associated with other cardiac anomalies including both acyanotic and cyanotic congenital cardiac defects. Therefore a wide variety of surgical procedures were performed including resection of the coarcted segment and end-to-end anastomosis, subclavian flap aortoplasty, patch aortoplasty and synthetic tube graft interposition. Subclavian flap aortoplasty is not widely practised anymore in favour of resection with end-to-end anastomosis. Fifty four point four percent of patients had isolated coarctation, 10.5% had associated valvular defects, 28.1% had other simple congenital defects and 7.0% had associated complex cyanotic congenital defects. Perioperative mortality was 5.26% and is correlated with the younger age of patients at time of surgery and severity of cardiac failure at time of presentation. We did not see any difference in mortality for patients with complex congenital disease or between the different surgical procedures. However, we did find that in the early period when resection with end-to-end anastomosis was performed, there was a significantly higher incidence of morbidities.

Obstruction of mechanical heart valve--diagnosis, surgical treatment and outcome.

From 1982 till 1999, our department performed a total of 2970 heart valve replacements--92% of which were with mechanical heart valves. During this period, there were 8 patients who came to our department with mechanical heart valve obstruction. All these patients presented with signs of heart failure or compromised haemodynamic. Confirmatory tests included transthoracic or transoesophageal echocardiography and cine fluoroscopy. Seven patients were operated upon urgently. Four of the patients had valve thrombosis. The time interval between the initial implantation and presentation varies from 4 months to 11.3 years. Six of the seven patients who were operated on recovered well from the surgery.

Mediastinal teratoma in a neonate.

A neonate with severe respiratory distress due to a benign mediastinal teratoma (MT) is reported. Despite early and easy surgical excision of the tumor, the child died due to poor cardiac function. Only ten cases of MT in neonates have been reported in the literature so far. While the tumor has been known to interfere with lung development in utero, postnatal myocardial dysfunction due to poor heart development has not been previously documented.

Survey of patients attending the eye clinic during the month of March; 1992

An audit survey was carried out during the month of March 1992 of patients attending the eye clinic. The number of patients; age and sex distribution; diagnosis; treatment modality and disposal were recorded. A total of 1166 patients were seen. The commonest diagnosis seen by the Ophthalmologist was non specific; and the commonest by the optometrist was presbyopia. Diseases required treatment included cataract; glaucoma and pterygium. Conditions that require screening included glaucoma and diabetic retinopathy. Prevention could be instituted in reducing other common conditions such trauma; pterygium and toxoplasma chorioretinitis