Purpose The AAPM & GEC-ESTRO Task Group No. 192 Report was published in 2014. Since then, improvements in robotic brachytherapy technology have been realized and a large number of new robotic systems were developed. In addition, progress has been made on translating some of these devices from laboratory to clinical practice. In response to these advances, the AAPM Brachytherapy subcommittee and GEC-ESTRO BRAPHYQS subcommittee convened a joint task group (TG-342) charged with updating the TG-192 report and providing comprehensive guidelines for implementation of these robotic devices in the clinic. Materials and Methods The current report (TG-342) mainly focuses on newer robotic systems available or reported since 2013. The TG-342 committee has gathered information from literature and drafted a report. There is minimal or no overlap with TG-192, so far the robotic systems are concerned. However, there are some overlaps in the methodology of clinical applications and recommendations. Results Several robotics systems described in the TG-192 Report have gone through major modifications, whereas some of them are now discontinued. Several new robotic systems (not reported in TG-192) have successfully been translated to clinical use and the reported clinical outcomes are encouraging. In TG-342, eighteen new robotic systems have been described and their specifications, status and applications have been illustrated. In TG-192 Report, 13 robotic systems were presented. Most of the new systems in TG-342 (18 in total) differ from each other with respect to available features, functionalities and levels of automation. The systems are either US guided or CT guided, only 3 systems are MRI guided. About half of the systems are needle guides with manual needle insertion, the other half accommodates autonomous needle insertion. Reported accuracy of needle tip placement in a phantom ranges from 0.9 to 2.9 mm. Few of them have been developed for other needle-based procedures such as biopsy, RFA, etc. However, these systems are also being considered for brachytherapy with minor modifications. The robotic assistance in clinical applications for LDR (permanent seed/source implantation) remains almost the same, while the applications for HDR procedures with robotic assistance have been elaborated. In addition, the recommendation section has been expanded. Conclusions International efforts in developing brachytherapy robots have been realized; the vast majority of the new systems are reported from Asia and Europe (17 out of 18). Some of those robotic systems have been used clinically. Due to the wide variability among the available robotic systems, various sections such as safety, commissioning, and recommendations have been written focusing on brachytherapy procedures rather than any specific robotic system. Current available brachytherapy robotic systems greatly vary in design, characteristics, features, and imaging modalities. Therefore, the TG-342 report provides general rather than very strict recommendations and encourages all researchers to develop and document their own calibration procedures specific for their robotic system. The final draft of TG-342 report is ready for review and approval by the parent committees. The AAPM & GEC-ESTRO Task Group No. 192 Report was published in 2014. Since then, improvements in robotic brachytherapy technology have been realized and a large number of new robotic systems were developed. In addition, progress has been made on translating some of these devices from laboratory to clinical practice. In response to these advances, the AAPM Brachytherapy subcommittee and GEC-ESTRO BRAPHYQS subcommittee convened a joint task group (TG-342) charged with updating the TG-192 report and providing comprehensive guidelines for implementation of these robotic devices in the clinic. The current report (TG-342) mainly focuses on newer robotic systems available or reported since 2013. The TG-342 committee has gathered information from literature and drafted a report. There is minimal or no overlap with TG-192, so far the robotic systems are concerned. However, there are some overlaps in the methodology of clinical applications and recommendations. Several robotics systems described in the TG-192 Report have gone through major modifications, whereas some of them are now discontinued. Several new robotic systems (not reported in TG-192) have successfully been translated to clinical use and the reported clinical outcomes are encouraging. In TG-342, eighteen new robotic systems have been described and their specifications, status and applications have been illustrated. In TG-192 Report, 13 robotic systems were presented. Most of the new systems in TG-342 (18 in total) differ from each other with respect to available features, functionalities and levels of automation. The systems are either US guided or CT guided, only 3 systems are MRI guided. About half of the systems are needle guides with manual needle insertion, the other half accommodates autonomous needle insertion. Reported accuracy of needle tip placement in a phantom ranges from 0.9 to 2.9 mm. Few of them have been developed for other needle-based procedures such as biopsy, RFA, etc. However, these systems are also being considered for brachytherapy with minor modifications. The robotic assistance in clinical applications for LDR (permanent seed/source implantation) remains almost the same, while the applications for HDR procedures with robotic assistance have been elaborated. In addition, the recommendation section has been expanded. International efforts in developing brachytherapy robots have been realized; the vast majority of the new systems are reported from Asia and Europe (17 out of 18). Some of those robotic systems have been used clinically. Due to the wide variability among the available robotic systems, various sections such as safety, commissioning, and recommendations have been written focusing on brachytherapy procedures rather than any specific robotic system. Current available brachytherapy robotic systems greatly vary in design, characteristics, features, and imaging modalities. Therefore, the TG-342 report provides general rather than very strict recommendations and encourages all researchers to develop and document their own calibration procedures specific for their robotic system. The final draft of TG-342 report is ready for review and approval by the parent committees.

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Background: Needle insertion is commonly used in minimally invasive surgery. Cannula flexible needle, as one of the insertion needles is composed of a flexible cannula and a flexible stylet, both of which need to be driven independently. The coordination control of both motions can achieve a variety of 3D insertion paths according to recent patents. Objective: This paper is to innovatively design an insertion mechanism for the cannula flexible realizing the coordinated motions of both the cannula and the stylet. Methods: Based on the analysis of the required degrees of freedom and motion models of the cannula flexible needle, the general scenario of the insertion mechanism was designed by using TRIZ theory. The condition for achieving the linear insertion path was obtained based on the analysis and calculation of the screw motion by using the screw theory. Results: The general scenario of the insertion mechanism was innovatively obtained, the spiral slide and the cross linear slide were adopted, and furthermore, the parameters of the spiral slide were determined, along with the design of cross linear slide. At last, the virtual prototype was achieved. Conclusion: In this paper, the TRIZ theory was used to innovatively design an insertion mechanism for the cannula flexible needle, and both the general scenario and the concrete parts were achieved. The result showed rationality of the designed insertion mechanism fulfilling all the requirements for the cannula flexible needle. Keywords: Cannula flexible needle, insertion mechanism, motion analysis, mechanical design, TRIZ, minimally invasive surgery.

In robot-assisted needle-based medical procedures, insertion motion planning is a crucial aspect. 3D dynamic motion planning for a cannula flexible needle is challenging with regard to the nonholonomic motion of the needle tip, the presence of anatomic obstacles or sensitive organs in the needle path, as well as uncertainties due to the dynamic environment caused by the movements and deformations of the organs. The kinematics of the cannula flexible needle is calculated in this paper. Based on a rapid and robust static motion planning algorithm, referred to as greedy heuristic and reachability-guided rapidly-exploring random trees, a 3D dynamic motion planner is developed by using replanning. Aiming at the large detour problem, the convergence problem and the accuracy problem that replanning encounters, three novel strategies are proposed and integrated into the conventional replanning algorithm. Comparisons are made between algorithms with and without the strategies to verify their validity. Simulations showed that the proposed algorithm can overcome the above-noted problems to realize real-time replanning in a 3D dynamic environment, which is appropriate for intraoperative planning.

Steerable needles can potentially improve the effectiveness of diagnostic and therapeutic procedures, such as biopsy and cancer treatment, by increasing the targeting accuracy and reaching previously inaccessible targets. A discrete potential field algorithm based on three dimensional (3D) anatomical structures is proposed in this paper to plan the needle path in minimally invasive surgery. A 3D kinematic model of needle steering is formulated using Lie group theory. Model parameters are fitted using experimental data acquired via a 2-degree of freedom robotic device and an ultrasound imaging device. To execute the paths with variable curvatures, the model is incorporated with duty cycled spinning. Empirical formula between needle curvature and duty cycled factor is obtained through insertion experiments. To improve the targeting accuracy, a path tracking algorithm is developed by correcting for the heading error and cross-track error of the needle tip. The targeting error of the simulation is 0.29 mm. We experimentally evaluate the path tracking model and it achieves an average targeting error of 1.15 +/- 0.56 mm in 3D environments with anatomical obstacles. The results of simulation are in agreement with steering experiments, showing that the discrete potential field algorithm and path tracking model have the potential to improve targeting accuracy and advance the therapeutic and diagnostic procedures. 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Background: Needle insertion is one of the most popular procedures in minimally invasive surgery (intervention). In order to improve the precision and automatization of the intervention, robot assisted surgery system has been extensively studied. Needle insertion mechanisms are one of the essential parts in the robot assisted surgery system. Keywords: Rigid needle, flexible needle, needle insertion mechanism, structural design, minimally invasive surgery, interventional robot.

In robot-assisted needle-based medical procedures, insertion motion planning is a crucial aspect. 3D dynamic motion planning for a cannula flexible needle is challenging with regard to the nonholonomic motion of the needle tip, the presence of anatomic obstacles or sensitive organs in the needle path, as well as uncertainties due to the dynamic environment caused by the movements and deformations of the organs. The kinematics of the cannula flexible needle is calculated in this paper. Based on a rapid and robust static motion planning algorithm, referred to as greedy heuristic and reachability-guided rapidly-exploring random trees, a 3D dynamic motion planner is developed by using replanning. Aiming at the large detour problem, the convergence problem and the accuracy problem that replanning encounters, three novel strategies are proposed and integrated into the conventional replanning algorithm. Comparisons are made between algorithms with and without the strategies to verify their validity. Simulations showed that the proposed algorithm can overcome the above-noted problems to realize real-time replanning in a 3D dynamic environment, which is appropriate for intraoperative planning.

According to the requirements of MRI (Magnetic Resonance Imaging) surgical navigation robot, a MRI-compatible breast intervention robot is designed. Due to the available space in MRI scanner is limited, a seven DOF (Degree of Freedom) robot is designed with rectangular coordinate system. The metallic materials in nuclear magnetic environment will influence the imaging and reduce the accuracy of surgery. Resolve the MR-compatible problem by using non-magnetic stainless steels and other non-magnetic materials. Put motors out of the nuclear magnetic environment, and use a long-distance transmission way to deliver the power. Utilize MATLAB/Simulink to do working space analysis. According to the analysis results, it is testified that the robot working space can cover the whole breasts of patient. Utilize ANSYS / Workbench to do statics analysis about crucial parts of the robot. By the force simulation, the deformed patterns and stress patterns are obtained to prove that the structure of robot is reasonableness. This design lies the foundation of further study.

It is definite that transparent material with similar structural characteristics and mechanical properties to human tissue is favorable for experimental study of prostate brachytherapy. In this paper, a kind of transparent polyvinyl alcohol (PVA) hydrogel and silicone rubber are developed as suitable substitutions for human soft tissue. Segmentation and 3D reconstruction of medical image are performed to manufacture the mould of organ groups through rapid prototyping technology. Micro-structure observation, force test and CCD deformation test have been conducted to investigate the structure and mechanical properties of PVA hydrogel used in organ group mockup. Scanning electron microscope (SEM) image comparison results show that PVA hydrogel consisting of 3 g PVA, 17 g de-ionized water, 80 g dimethyl-sulfoxide (DMSO), 4 g NaCl, 1.5 g NaOH, 3 g epichlorohydrin (ECH) and 7 freeze/thaw cycles reveals similar micro-structure to human prostate tissue. Through the insertion force comparison between organ group mockup and clinical prostate brachytherapy, PVA hydrogel and silicone rubber are found to have the same mechanical properties as prostate tissue and muscle. CCD deformation test results show that insertion force suffers a sharp decrease and a relaxation of tissue deformation appears when needle punctures the capsule of prostate model. The results exhibit that organ group mockup consisting of PVA hydrogel, silicone rubber, membrane and agarose satisfies the needs of prostate brachytherapy simulation in general and can be used to mimic the soft tissues in pelvic structure.

Kinematic calibration is an effective and economical way to improve the accuracy of surgical robot, and in most cases, it is a necessary procedure before the robot is put into operation. This study investigates a novel kinematic calibration method where the effect of controller error is taken into account when formulating the model based on screw theory, which is applied to the kinematic control of magnetic resonance compatible surgical robot. Based on screw theory, the kinematic error model is established for the relationship between error of controller and the deviation of the measured pose of the end-effector. Therefore, the error of controller can be figured out and parameters of controller can be adjusted accordingly. Control strategy based on the kinematic calibration framework is proposed. According to artificial neural network, the deviation of end-effector in arbitrary configuration can be effectively obtained. Comparative experiments are carried out to show the validity and effectiveness of the proposed framework with the help of commercial visual system and joint encoders.

This paper presents the experimental evaluation of a coordinated control system for a robot and robot-driven shape memory alloy (SMA) actuated smart flexible needle capable of following a curved path for percutaneous intervention. The robot driving the needle is considered the outer loop and the non-linear SMA actuated flexible needle system comprises the inner loop. The two feedback control loops are coordinated in such a way that the robot drives the needle while monitoring the needle's actual deflection against a preplanned ideal trajectory, so that the needle tip reaches the target location within an acceptable accuracy. In air and in water experimental results are presented to validate the ability of the proposed coordinated controller to track the overall desired trajectory which includes the combined trajectory of the robot driver and the needle.

Outstanding properties of nitinol, known as shape memory and superelasticity, make them suitable alternatives in several biomedical, aerospace, and civil applications. For instance, nitinol wires have been used as the actuator components in many innovative medical devices aiming to make surgical tasks less invasive and more efficient. In most of these applications, it is desired to have a consistent strain response of nitinol wires; therefore, it is necessary to investigate the internal phase transformations from microstructural point of view. In this study, the effect of influencing factors such as biased stress during thermal cycle, the maximum temperature wires experienced during heating part of thermal cycle, and also wire diameters on the amount of unrecovered strain occurred between the first and the second thermal cycles has been investigated. The generation of different phase compositions in the same thermomechanical condition for different wire diameters has been discussed using x-ray diffraction (XRD) method. The location and intensity of characteristic peaks were studied prior and after the loading cycles. It was observed that nitinol wires of diameters less than 0.19 mm exhibit unrecovered strain while heated to the range of 70-80 °C in a thermal cycle, whereas no unrecovered strain was found in wires with larger diameter. The observation was supported by the XRD patterns where the formation of R-phase instead of martensite was shown in wire diameters of less than 0.19 mm after cooling back to room temperature.

In external beam radiotherapy (EBRT), one of the major challenges is to compensate for target motion induced by patient's respiration and organ motion. The accurate delivery of radiation to the moving targets (tumors) requires new innovative technologies and methods to avoid excessive irradiation of healthy tissue. Recently, we developed a tracking method for target motion compensations, which includes the real-time motion of the robotic treatment couch and a prediction algorithm to correct the motion trajectory for the latency of the mechanical components of the system. The purpose of this study was to evaluate the tracking system efficacy, using different tumor motion trajectories collected from real patients diagnosed with lung cancer.

Biopsy and brachytherapy for small core breast cancer are always difficult medical problems in the field of cancer treatment. This research mainly develops a magnetic resonance imaging–guided high-precision robotic system for breast puncture treatment. First, a 5-degree-of-freedom tendon-based surgical robotic system is introduced in detail. What follows are the kinematic analysis and dynamical modeling of the robotic system, where a mathematic dynamic model is established using the Lagrange method and a lumped parameter tendon model is used to identify the nonlinear gain of the tendon-sheath transmission system. Based on the dynamical models, an adaptive proportional–integral–derivative controller with friction compensation is proposed for accurate position control. Through simulations using different sinusoidal input signals, we observe that the sinusoidal tracking error at 1/2 π Hz is 0.41 mm. Finally, the experiments on tendon-sheath transmission and needle insertion performance are conducted, which show that the insertion precision is 0.68 mm in laboratory environment.

A thorough understanding of needle-tissue interaction mechanics is necessary to optimize needle design, achieve robotically needle steering, and establish surgical simulation system. It is obvious that the interaction is influenced by numerous variable parameters, which are divided into three categories: needle geometries, insertion methods, and tissue characteristics. A series of experiments are performed to explore the effect of influence factors (material samples n=5 for each factor) on the insertion force. Data were collected from different biological tissues and a special tissue-equivalent phantom with similar mechanical properties, using a 1-DOF mechanical testing system instrumented with a 6-DOF force/torque (F/T) sensor. The experimental results indicate that three basic phases (deformation, insertion, and extraction phase) are existent during needle penetration. Needle diameter (0.7-3.2mm), needle tip (blunt, diamond, conical, and beveled) and bevel angle (10-85°) are turned out to have a great influence on insertion force, so do the insertion velocity (0.5-10mm/s), drive mode (robot-assisted and hand-held), and the insertion process (interrupted and continuous). Different tissues such as skin, muscle, fat, liver capsule and vessel are proved to generate various force cures, which can contribute to the judgement of the needle position and provide efficient insertion strategy.

In the last decade, there have been significant developments into integration of robots and automation tools with brachytherapy delivery systems. These systems aim to improve the current paradigm by executing higher precision and accuracy in seed placement, improving calculation of optimal seed locations, minimizing surgical trauma, and reducing radiation exposure to medical staff. Most of the applications of this technology have been in the implantation of seeds in patients with early-stage prostate cancer. Nevertheless, the techniques apply to any clinical site where interstitial brachytherapy is appropriate. In consideration of the rapid developments in this area, the American Association of Physicists in Medicine (AAPM) commissioned Task Group 192 to review the state-of-the-art in the field of robotic interstitial brachytherapy. This is a joint Task Group with the Groupe Européen de Curiethérapie-European Society for Radiotherapy & Oncology (GEC-ESTRO). All developed and reported robotic brachytherapy systems were reviewed. Commissioning and quality assurance procedures for the safe and consistent use of these systems are also provided. Manual seed placement techniques with a rigid template have an estimated in vivo accuracy of 3-6 mm. In addition to the placement accuracy, factors such as tissue deformation, needle deviation, and edema may result in a delivered dose distribution that differs from the preimplant or intraoperative plan. However, real-time needle tracking and seed identification for dynamic updating of dosimetry may improve the quality of seed implantation. The AAPM and GEC-ESTRO recommend that robotic systems should demonstrate a spatial accuracy of seed placement ≤1.0 mm in a phantom. This recommendation is based on the current performance of existing robotic brachytherapy systems and propagation of uncertainties. During clinical commissioning, tests should be conducted to ensure that this level of accuracy is achieved. These tests should mimic the real operating procedure as closely as possible. Additional recommendations on robotic brachytherapy systems include display of the operational state; capability of manual override; documented policies for independent check and data verification; intuitive interface displaying the implantation plan and visualization of needle positions and seed locations relative to the target anatomy; needle insertion in a sequential order; robot-clinician and robot-patient interactions robustness, reliability, and safety while delivering the correct dose at the correct site for the correct patient; avoidance of excessive force on radioactive sources; delivery confirmation of the required number or position of seeds; incorporation of a collision avoidance system; system cleaning, decontamination, and sterilization procedures. These recommendations are applicable to end users and manufacturers of robotic brachytherapy systems.

In this paper, we focus on the design requirement of a high-precision magnetic resonance imaging-compatible robot for prostate needle-insertion surgery, which is actuated by five ultrasonic motors to achieve the goal of needle posture adjustment and prostate puncture. After a brief introduction to the robot, the direct and inverse kinematic equations are deduced. In order to show the relationship of the velocity between the actuators and the end effector, the Jacobian matrix is derived by formulating a velocity closed-loop equation for each limb. The kinematics is carried out by minimizing a global and comprehensive dimensional synthesis conditioning index subject to transmission angle and range of motion of the mechanism constraints. The dimensional parameters are obtained for achieving a good kinematic performance throughout the entire task workspace by an example, and finally the reachable workspace of the robot is calculated.

Unique thermomechanical properties of Nitinol known as shape memory and superelasticity make it applicable for different fields such as biomedical, structural, and aerospace engineering. These unique properties are due to the comparatively large recoverable strain, which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain. For cyclic applications, it is important to understand the strain behavior of Nitinol wires. In this study, the unrecovered strain of different Nitinol wire diameters was investigated using constant stress experiment. Uniaxial tensile test has been also performed to find the range of critical stresses. It was observed that the unrecovered strain produced in the first loading-unloading cycle affects the total strain in the subsequent cycles. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible while the wires heated up to the range of 70-80°C, depending on the wire diameters. The unrecovered strain of wire diameters of 0.19 mm and less was found to be sensitive to the critical stress. On the other hand, for wire diameters bigger than 0.19 mm this connection between the unrecovered strain and the critical stress was not observed for the same range of heating temperature.