A model-based bone milling state identification method via force sensing for a robotic surgical system.

BACKGROUND: This paper presents a model-based bone milling state identification method that provides intraoperative bone quality information during robotic bone milling. The method helps surgeons identify bone layer transitions during bone milling. METHODS: On the basis of a series of bone milling experiments with commercial artificial bones, an artificial neural network force model is developed to estimate the milling force of different bone densities as a function of the milling feed rate and spindle speed. The model estimations are used to identify the bone density at the cutting zone by comparing the actual milling force with the estimated one. RESULTS: The verification experiments indicate the ability of the proposed method to distinguish between one cortical and two cancellous bone densities. CONCLUSIONS: The significance of the proposed method is that it can be used to discriminate a set of different bone density layers for a range of the milling feed rate and spindle speed.

Three-Dimensional Intravascular Reconstruction Techniques Based on Intravascular Ultrasound: A Technical Review.

Intravascular ultrasound (IVUS) imaging provides two-dimensional (2-D) real-time luminal and transmural cross-sectional images of intravascular vessels with detailed pathological information. It has offered significant advantages in terms of diagnosis and guidance and has been increasingly introduced from coronary interventions into more generalized endovascular surgery. However, IVUS itself does not provide spatial pose information for its generated images, making it difficult to construct a 3-D intravascular visualization. To address this limitation, IVUS imaging-driven 3-D intravascular reconstruction techniques have been developed. These techniques enable accurate diagnosis and quantitative measurements of intravascular diseases to facilitate optimal treatment determination. Such reconstruction extends the IVUS imaging modality from pure diagnostic assistance to intraoperative navigation and guidance and supports both therapeutic options and interventional operations. This paper presents a comprehensive survey of technological advances and recent progress on IVUS imaging-based 3-D intravascular reconstruction and its state-of-the-art applications. Limitations of existing technologies and prospects of new technologies are also discussed.

Shape Sensing Techniques for Continuum Robots in Minimally Invasive Surgery: A Survey.

Continuum robots provide inherent structural compliance with high dexterity to access the surgical target sites along tortuous anatomical paths under constrained environments and enable to perform complex and delicate operations through small incisions in minimally invasive surgery. These advantages enable their broad applications with minimal trauma and make challenging clinical procedures possible with miniaturized instrumentation and high curvilinear access capabilities. However, their inherent deformable designs make it difficult to realize 3-D intraoperative real-time shape sensing to accurately model their shape. Solutions to this limitation can lead themselves to further develop closely associated techniques of closed-loop control, path planning, human-robot interaction, and surgical manipulation safety concerns in minimally invasive surgery. Although extensive model-based research that relies on kinematics and mechanics has been performed, accurate shape sensing of continuum robots remains challenging, particularly in cases of unknown and dynamic payloads. This survey investigates the recent advances in alternative emerging techniques for 3-D shape sensing in this field and focuses on the following categories: fiber-optic-sensor-based, electromagnetic-tracking-based, and intraoperative imaging modality-based shape-reconstruction methods. The limitations of existing technologies and prospects of new technologies are also discussed.

Microfluidic Device to Measure the Speed of C. elegans Using the Resistance Change of the Flexible Electrode.

This work presents a novel method to assess the condition of Caenorhabditis elegans (C. elegans) through a resistance measurement of its undulatory locomotion speed inside a micro channel. As the worm moves over the electrode inside the micro channel, the length of the electrode changes, consequently behaving like a strain gauge. In this paper, the electrotaxis was applied for controlling the direction of motion of C. elegans as an external stimulus, resulting in the worm moving towards the cathode of the circuit. To confirm the proposed measurement method, a microfluidic device was developed that employs a sinusoidal channel and a thin polydimethylsiloxane (PDMS) layer with an electrode. The PDMS layer maintains a porous structure to enable the flexibility of the electrode. In this study, 6 measurements were performed to obtain the speed of an early adult stage C. elegans, where the measured average speed was 0.35 (±0.05) mm/s. The results of this work demonstrate the application of our method to measure the speed of C. elegans undulatory locomotion. This novel approach can be applied to make such measurements without an imaging system, and more importantly, allows directly to detect the locomotion of C. elegans using an electrical signal (i.e., the change in resistance).

In vitro simulator with numerical stress analysis for evaluation of stent-assisted coiling embolization in cerebral aneurysm treatments.

BACKGROUND: There are several complications associated with Stent-assisted Coil Embolization (SACE) in cerebral aneurysm treatments, due to damaging operations by surgeons and undesirable mechanical properties of stents. Therefore, it is necessary to develop an in vitro simulator that provides both training and research for evaluating the mechanical properties of stents. METHODS: A new in vitro simulator for three-dimensional digital subtraction angiography was constructed, followed by aneurysm models fabricated with new materials. Next, this platform was used to provide training and to conduct photoelastic stress analysis to evaluate the SACE technique. RESULTS: The average interaction stress increasingly varied for the two different stents. Improvements for the Maximum-Likelihood Expectation-Maximization method were developed to reconstruct cross-sections with both thickness and stress information. CONCLUSIONS: The technique presented can improve a surgeon's skills and quantify the performance of stents to improve mechanical design and classification. This method can contribute to three-dimensional stress and volume variation evaluation and assess a surgeon's skills.

Single cell stiffness measurement at various humidity conditions by nanomanipulation of a nano-needle.

This paper presents a method for single cell stiffness measurement based on a nano-needle and nanomanipulation. The nano-needle with a buffering beam was fabricated from an atomic force microscope cantilever by the focused ion beam etching technique. Wild type yeast cells (W303) were prepared and placed on the sample stage inside an environmental scanning electron microscope (ESEM) chamber. The nanomanipulator actuated the nano-needle to press against a single yeast cell. As a result, the deformation of the cell and nano-needle was observed by the ESEM system in real-time. Finally, the stiffness of the single cell was determined based on this deformation information. To reveal the relationship between the cell stiffness and the environmental humidity conditions, the cell stiffness was measured at three different humidity conditions, i.e. 40, 70 and 100%, respectively. The results show that the stiffness of a single cell is reduced with increasing humidity.

In vitro strain measurements in cerebral aneurysm models for cyber-physical diagnosis.

BACKGROUND: The development of new diagnostic technologies for cerebrovascular diseases requires an understanding of the mechanism behind the growth and rupture of cerebral aneurysms. To provide a comprehensive diagnosis and prognosis of this disease, it is desirable to evaluate wall shear stress, pressure, deformation and strain in the aneurysm region, based on information provided by medical imaging technologies. METHODS: In this research, we propose a new cyber-physical system composed of in vitro dynamic strain experimental measurements and computational fluid dynamics (CFD) simulation for the diagnosis of cerebral aneurysms. A CFD simulation and a scaled-up membranous silicone model of a cerebral aneurysm were completed, based on patient-specific data recorded in August 2008. In vitro blood flow simulation was realized with the use of a specialized pump. A vision system was also developed to measure the strain at different regions on the model by way of pulsating blood flow circulating inside the model. RESULTS: Experimental results show that distance and area strain maxima were larger near the aneurysm neck (0.042 and 0.052), followed by the aneurysm dome (0.023 and 0.04) and finally the main blood vessel section (0.01 and 0.014). These results were complemented by a CFD simulation for the addition of wall shear stress, oscillatory shear index and aneurysm formation index. Diagnosis results using imaging obtained in August 2008 are consistent with the monitored aneurysm growth in 2011. CONCLUSION: The presented study demonstrates a new experimental platform for measuring dynamic strain within cerebral aneurysms. This platform is also complemented by a CFD simulation for advanced diagnosis and prediction of the growth tendency of an aneurysm in endovascular surgery.

Technical skills measurement based on a cyber-physical system for endovascular surgery simulation.

BACKGROUND: Quantification of medical skills is a challenge, particularly simulator-based training. In the case of endovascular intervention, it is desirable that a simulator accurately recreates the morphology and mechanical characteristics of the vasculature while enabling scoring. METHODS: For this purpose, we propose a cyber-physical system composed of optical sensors for a catheter's body motion encoding, a magnetic tracker for motion capture of an operator's hands, and opto-mechatronic sensors for measuring the interaction of the catheter tip with the vasculature model wall. Two pilot studies were conducted for measuring technical skills, one for distinguishing novices from experts and the other for measuring unnecessary motion. RESULTS: The proficiency levels were measurable between expert and novice and also between individual novice users. The results enabled scoring of the user's proficiency level, using sensitivity, reaction time, time to complete a task and respect for tissue integrity as evaluation criteria. Additionally, unnecessary motion was also measurable. CONCLUSION: The development of cyber-physical simulators for other domains of medicine depend on the study of photoelastic materials for human tissue modelling, and enables quantitative evaluation of skills using surgical instruments and a realistic representation of human tissue.