A novel integration of spectral-domain optical-coherence-tomography and laser-ablation system for precision treatment

Performance analysis of a liquid lens for laser ablation using OCT imaging

Laser ablation has been used in different surgical procedures to perform precise treatments. Compared with previous free-beam laser delivery systems, flexible-optical-fiber-based systems can deliver laser energy to a curved space, avoiding the requirement of a straight working path to the target. However, the fiber tip maintains direct contact with the tissue to prevent laser divergence, resulting in fiber damage, uneven ablation, and tissue carbonization. Here, a liquid lens is used to address the problem of laser defocusing when radiating targets at different depths for flexible-optical-fiber-based systems. The liquid lens focuses a laser with a maximum power of 3 W onto a medium-density fiberboard at a focal length of 40-180 mm. The relationships between the ablation crater diameter and depth with the radiation time and laser power have been quantitatively evaluated through OCT (optical coherence tomography) imaging. Experiments demonstrate that the liquid lens can continuously focus the high-power laser to different depths, with the advantages of compact size, fast response, light weight, and easy operation. This study explores liquid-lens-based focused laser ablation, which can potentially improve the performance of future medical image-guided laser ablation.

The State-of-the-Art and Perspectives of Laser Ablation for Tumor Treatment

Tumors significantly impact individuals' physical well-being and quality of life. With the ongoing advancements in optical technology, information technology, robotic technology, etc., laser technology is being increasingly utilized in the field of tumor treatment, and laser ablation (LA) of tumors remains a prominent area of research interest. This paper presents an overview of the recent progress in tumor LA therapy, with a focus on the mechanisms and biological effects of LA, commonly used ablation lasers, image-guided LA, and robotic-assisted LA. Further insights and future prospects are discussed in relation to these aspects, and the paper proposed potential future directions for the development of tumor LA techniques.

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.

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.

N-mirror Robot System for Laser Surgery: A Simulation Study

Automated laser surgery with sensor fusion is an important problem in medical robotics since it requires precise control of mirrors used to steer the laser systems. The propagation of the laser beam should satisfy the geometric constraints of the surgical site but the relation between the number of mirrors and the design of the optical path remains an unsolved problem. Furthermore, different types of surgery (e.g. endoscopic vs open surgery) can require different optical designs with varying number of mirrors to successfully steer the laser beam to the tissue. A generalized method for controlling the laser beam in such systems remains an open research question. This paper proposes an analytical model for a laser-based surgical system with an arbitrary number of mirrors, which is referred as an "N -mirror" robotic system. This system consists of three laser inputs to transmit the laser beam to the tissue surface through N number of mirrors, which can achieve surface scanning, tissue resection and tissue classification separately. For sensor information alignment, the forward and inverse kinematics of the N -mirror robot system are derived and used to calculate the mirror angles for laser steering at the target surface. We propose a system calibration method to determine the laser input configuration that is required in the kinematic modelling. We conduct simulation experiments for a simulated 3-mirror system of an actual robotic laser platform and a 6-mirror simulated robot, both with 3-laser inputs. The simulation experiments for system calibration show results of maximum position offset smaller than 0.127 mm and maximum angle offset smaller than 0.05° for the optimal laser input predictions.

Towards OCT-Guided Endoscopic Laser Surgery-A Review

Optical Coherence Tomography (OCT) is an optical imaging technology occupying a unique position in the resolution vs. imaging depth spectrum. It is already well established in the field of ophthalmology, and its application in other fields of medicine is growing. This is motivated by the fact that OCT is a real-time sensing technology with high sensitivity to precancerous lesions in epithelial tissues, which can be exploited to provide valuable information to clinicians. In the prospective case of OCT-guided endoscopic laser surgery, these real-time data will be used to assist surgeons in challenging endoscopic procedures in which high-power lasers are used to eradicate diseases. The combination of OCT and laser is expected to enhance the detection of tumors, the identification of tumor margins, and ensure total disease eradication while avoiding damage to healthy tissue and critical anatomical structures. Therefore, OCT-guided endoscopic laser surgery is an important nascent research area. This paper aims to contribute to this field with a comprehensive review of state-of-the-art technologies that may be exploited as the building blocks for achieving such a system. The paper begins with a review of the principles and technical details of endoscopic OCT, highlighting challenges and proposed solutions. Then, once the state of the art of the base imaging technology is outlined, the new OCT-guided endoscopic laser surgery frontier is reviewed. Finally, the paper concludes with a discussion on the constraints, benefits and open challenges associated with this new type of surgical technology.

Classification of gastric cancerous tissues by a residual network based on optical coherence tomography images

Optical coherence tomography (OCT) is a noninvasive, radiation-free, and high-resolution imaging technology. The intraoperative classification of normal and cancerous tissue is critical for surgeons to guide surgical operations. Accurate classification of gastric cancerous OCT images is beneficial to improve the effect of surgical treatment based on the deep learning method. The OCT system was used to collect images of cancerous tissues removed from patients. An intelligent classification method of gastric cancerous tissues based on the residual network is proposed in this study and optimized with the ResNet18 model. Four residual blocks are used to reset the model structure of ResNet18 and reduce the number of network layers to identify cancerous tissues. The model performance of different residual networks is evaluated by accuracy, precision, recall, specificity, F1 value, ROC curve, and model parameters. The classification accuracies of the proposed method and ResNet18 both reach 99.90%. Also, the model parameters of the proposed method are 44% of ResNet18, which occupies fewer system resources and is more efficient. In this study, the proposed deep learning method was used to automatically recognize OCT images of gastric cancerous tissue. This artificial intelligence method could help promote the clinical application of gastric cancerous tissue classification in the future.

Current research and future prospects of IVOCT imaging-based detection of the vascular lumen and vulnerable plaque

Intravascular optical coherence tomography (IVOCT) is an imaging method that has developed rapidly in recent years and is useful in coronary atherosclerosis diagnosis. It is widely used in the assessment of vulnerable plaque. This review summarizes the main research methods used in recent years for blood vessel lumen boundary detection and segmentation and vulnerable plaque segmentation and classification. This article aims to comprehensively and systematically introduce the research progress on internal tissues of blood vessels based on IVOCT images. The characteristics and advantages of various methods have been summarized to provide theoretical ideas and methods for the reference of relevant researchers and scholars.

Quantitative investigation of laser ablation based on real-time temperature variations and OCT images for laser treatment applications

BACKGROUND AND OBJECTIVE

Lasers are widely employed in clinical applications. In vivo monitoring of real-time information about different-wavelength laser surgeries would provide important surgical feedback for surgeons or clinical therapy instruments. However, the quantitative effect of laser ablation or vaporization still needs to be further explored and investigated. Here, we investigate and quantitatively evaluate the ablation variations and morphological changes of two laser ablation models: point- and sweeping-based models.

METHODS

An infrared thermal imager was used to monitor the temperature variations, and curve fitting was used to build the relationship between the laser radiation duration/sweeping speed and quantitative parameters of the ablated areas. Optical coherence tomography (OCT) images were used to visualize the inner structure and evaluate the depth of the ablated craters. Optical attenuation coefficients (OACs) were computed to characterize the normal and ablated tissues.

RESULTS

The results demonstrated that there was a good linear relationship between radiation duration and temperature variation. Similarly, a linear relationship was observed between the sweeping speed and quantitative parameters of craters or scratches (width and depth). The mean OAC of normal tissues was significantly distinguished from the mean OACs of the ablated craters or scratches.

CONCLUSION

Laser ablation was investigated based on a quantitative parameter analysis, thermal detection, and OCT imaging, and the results successfully demonstrated that there is a linear relationship between the laser parameters and quantitative parameters of the ablated tissues under the current settings. Such technology could be used to provide quantitative solutions for exploring the laser-tissue biological effect and improve the performance of medical image-guided laser ablation in the future.

Intelligent optical diagnosis and treatment system for automated image-guided laser ablation of tumors

PURPOSE

For tumor resections near critical structures, accurate identification of tumor boundaries and maximum removal are the keys to improve surgical outcome and patient survival rate, especially in neurosurgery. In this paper, we propose an intelligent optical diagnosis and treatment system for tumor removal, with automated lesion localization and laser ablation.

METHODS

The proposed system contains a laser ablation module, an optical coherence tomography (OCT) unit, and a robotic arm along with a stereo camera. The robotic arm can move the OCT sample arm and the laser ablation front-end to the suspected lesion area. The corresponding diagnosis and treatment procedures include computer-aided lesion segmentation using OCT, automated ablation planning, and laser control. The ablation process is controlled by a deflectable mirror, and a non-common-path ablation planning algorithm based on the transformation from lesion positions to mirror deflection angles is presented.

RESULTS

Phantom and animal experiments are carried out for system verification. The robot could reach the planned position with high precision, which is approximately 1.16 mm. Tissue classification with OCT images achieves 91.7% accuracy. The error of OCT-guided automated laser ablation is approximately 0.74 mm. Experiments on mouse brain tumors show that the proposed system is capable of clearing lesions efficiently and precisely. We also conducted an ex vivo porcine brain experiment to verify the whole process of the system.

CONCLUSION

An intelligent optical diagnosis and treatment system is proposed for tumor removal. Experimental results show that the proposed system and method are promising for precise and intelligent theranostics. Compared to conventional cancer diagnosis and treatment, the proposed system allows for automated operations monitored in real-time, with higher precision and efficiency.

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.

Antitumor effects of targeted killing of tumor-associated macrophages under photothermal conditions

Immunotherapy of tumors has become a research hotspot. Tumor-associated macrophages (TAMs) are the most abundant interstitial cells in a tumor's microenvironment. As the concentration of the prepared nanoparticles increased, so their cytotoxicity of intensified. Under photothermal conditions, mAb-CD163/Au inhibited tumor invasion by killing M2 macrophages in vitro. After exposure to near-infrared (NIR) laser, mAb-CD163/Au inhibited tumor growth in vivo. The gold nanoparticles were modified to target M2 macrophages. Under NIR laser irradiation, mAb-CD163/Au achieved antitumor effects by killing M2 macrophages in vitro and in vivo.

Laser brain cancer surgery in a xenograft model guided by optical coherence tomography

Higher precision surgical devices are needed for tumor resections near critical brain structures. The goal of this study is to demonstrate feasibility of a system capable of precise and bloodless tumor ablation. An image-guided laser surgical system is presented for excision of brain tumors in vivo in a murine xenograft model. The system combines optical coherence tomography (OCT) guidance with surgical lasers for high-precision tumor ablation (Er:YAG) and microcirculation coagulation (Thulium (Tm) fiber laser).

Methods: A fluorescent human glioblastoma cell line was injected into mice and allowed to grow four weeks. Craniotomies were performed and tumors were imaged with confocal fluorescence microscopy. The mice were subsequently OCT imaged prior, during and after laser coagulation and/or ablation. The prior OCT images were used to compute three-dimensional tumor margin and angiography images, which guided the coagulation and ablation steps. Histology of the treated regions was then compared to post-treatment OCT images.

Results: Tumor sizing based on OCT margin detection matched histology to within experimental error. Although fluorescence microscopy imaging showed the tumors were collocated with OCT imaging, margin assessment using confocal microscopy failed to see the extent of the tumor beyond ~ 250 µm in depth, as verified by OCT and histology. The two-laser approach to surgery utilizing Tm wavelength for coagulation and Er:YAG for ablation yielded bloodless resection of tumor regions with minimal residual damage as seen in histology.

Conclusion: Precise and bloodless tumor resection under OCT image guidance is demonstrated in the murine xenograft brain cancer model. Tumor margins and vasculature are accurately made visible without need for exogenous contrast agents.

Bioluminescence imaging and two-photon microscopy guided laser ablation of GBM decreases tumor burden

Brain tumor delineation and treatment are the main concerns of neurosurgeons in neurosurgical operations. Bridging the gap between imaging/diagnosis and treatment will provide great convenience for neurosurgeons. Here, we developed an optical theranostics platform that helps to delineate the boundary and quantitatively analyze glioblastoma multiforms (GBMs) with bioluminescence imaging (BLI) to guide laser ablation, and we imaged the GBM cells with two-photon microscopy (TPM) to visualize the laser ablation zone in vivo.

Methods: Laser ablation, using the method of coupled ablated path planning with the guidance of BLI, was implemented in vivo for mouse brain tumors. The mapping relationship between semi-quantitative BLI and the laser ablation path was built through the quantitative tumor burden. The mapping was reflected through coupled ablated path planning. The BLI quantitatively and qualitatively evaluated treatment using laser ablation with the appropriate laser parameters and laser-tissue parameters. These parameters were measured after treatment. Furthermore, histopathological analysis of the brain tissue was conducted to compare the TPM images before and after laser ablation and to evaluate the results of in vivo laser ablation. The local recurrences were measured with three separate cohorts. The weights of all of the mice were measured during the experiment.

Results: Our in vivo BLI data show that the tumor cell numbers were significantly attenuated after treatment with the optical theranostics platform, and the delineation of GBM margins had clear views to guide the laser resection; the fluorescence intensity in vivo of GBMs quantitatively analyzed the rapid progression of GBMs. The laser-tissue parameters under guidance of multimodality imaging ranged between 1.0 mm and 0.1 mm. The accuracy of the laser ablation reached a submillimeter level, and the resection ratio reached more than 99% under the guidance of BLI. The histopathological sections were compared to TPM images, and the results demonstrated that these images highly coincided. The weight index and local recurrence results demonstrated that the therapeutic effect of the optical theranostics platform was significant.

Conclusion: We propose an optical multimodality imaging-guided laser ablation theranostics platform for the treatment of GBMs in an intravital mouse model. The experimental results demonstrated that the integration of multimodality imaging can precisely guide laser ablation for the treatment of GBMs. This preclinical research provides a possibility for the precision treatment of GBMs. The study also provides some theoretical support for clinical research.

Optical coherence tomography for precision brain imaging, neurosurgical guidance and minimally invasive theranostics

This review focuses on optical coherence tomography (OCT)-based neurosurgical application for imaging and treatment of brain tumors. OCT has emerged as one of the most innovative and successful translational biomedical-diagnostic techniques. It is a useful imaging tool for noninvasive, in vivo, in situ and real-time imaging in soft biological tissues, such as brain tumor imaging. OCT can detect the structure of biological tissue in a micrometer scale, and functional OCT has some clinical researches and applications, such as nerve fiber tracts and neurovascular imaging. OCT is able to identify tumor margins, and it gives intraoperative precision identification and resection guidance. OCT-based theranostics is introduced into preclinical neurosurgical resection, such as the integration of OCT and laser ablation. We discuss the challenges and opportunities of OCT-based system in the field of combination of intraoperative structural and functional imaging, neurosurgical guidance and minimally invasive theranostics. We point out that OCT and laser ablation-based theranostics can give more precision and intelligence for intraoperative diagnosis and therapeutics in clinical applications. The theranostics can precisely locate, or specifically target cancerous tissues, and then as much as possiblly eliminate them.

Can "Indirect" Contact Laser Surgery be Used for Fluorescence-Image Guided Tumor Resections? Preliminary Results

Ensuring the complete removal of tumor tissue is the main challenge during resection operations. Recently, a technique of “indirect” contact laser surgery has been developed. In this study we assess the possibility of using such surgery for fluorescence image-guided tumor resection. Mouse colon adenocarcinoma CT-26 cells stably expressing the fluorescent protein mKate-2 was used as the tumor model. Resections of the tumor nodes were performed with either a scalpel blade, a laser scalpel with a bare tip, or a laser scalpel with a strongly absorbing coating on the fiber tip. Tumor-positive resection margins were detected using an IVIS Spectrum fluorescence imaging system. After tumor resection with the scalpel blade over half of the animals needed one additional resection to remove residual tumor cells. Animals in this group showed tumor recurrence within 7 days. Fluorescence imaging of the tumor bed, performed after resection to assess the presence of tumor cell clusters, was sufficiently effective only with a bloodless resection. The laser scalpels both with the bare tip and with the strongly absorbing coating on the tip provided such bloodless tumor resection in contact mode. Fewer animals required additional resections when the bare tipped scalpel was used and this also resulted in a reduction in tumor recurrence. After resections were carried out with the laser scalpel with the strongly absorbing coating on the tip, fluorescence was detected in the operative field and this led to undertaking additional resections, although subsequent investigation suggested that this was “false” fluorescence, resulting from the effects of the scalpel rather than the presence of residual tumor cells. The method of laser resection with a strongly absorbing coating on the tip therefore did not appear to demonstrate definite advantages over laser resection with a bare tip when removing tumors.