AAPM and GEC-ESTRO guidelines for image-guided robotic brachytherapy: report of Task Group 192

Multimodal image-guided surgical robot versus 3D-printed template for brachytherapy of malignant tumours in the skull base and deep facial region: a clinical comparative study

This study compared a multimodal image-guided robot and three-dimensionally (3D) printed templates for implanting iodine-125 (I125) radioactive seeds in patients with malignant tumours in the skull base and deep facial region. Seventeen patients who underwent I125 radioactive seed implantation between December 2018 and December 2019 were included. The operation time, intraoperative blood loss, and accuracy of seed implantation were compared between the multimodal image-guided robot-assisted implantation (experimental) group (n = 7) and 3D-printed template-assisted implantation (control) group (n = 10). In total, 291 seeds were implanted in the experimental group and 436 in the control group; the mean error of seed implantation accuracy was 1.95 ± 0.13 mm and 1.90 ± 0.08 mm, respectively (P = 0.309). The preparation time was 26.13 ± 5.28 min in the experimental group and 0 min in the control group, while the average operation time was 34.44 ± 6.39 min versus 43.70 ± 6.06 min, respectively. The intraoperative blood loss was 4.96 ± 1.76 ml (experimental) versus 8.97 ± 2.99 ml (control) (P = 0.123). Multimodal image-guided robot-assisted I125 radioactive seed implantation met the clinical requirements for treating malignant tumours in the skull base and deep facial regions.

Is model-based dose calculation based on cone-beam computed tomography suitable for adaptive treatment planning in brachytherapy?

BACKGROUND AND PURPOSE

Model-based dose calculation considering tissue compositions is increasingly being investigated in brachytherapy. The aim of this study was to assess the suitability of modern cone-beam computed tomography (CBCT) imaging compared to conventional computed tomography (CT) scans for this purpose.

MATERIALS AND METHODS

By means of a phantom study, we evaluated the CT numbers and electron densities measured using a modern CBCT device as well as a conventional CT scanner for various materials. Based on this, we compared dose calculations (using the TG-43 formalism as well as model-based collapsed cone calculations assuming uniform materials [ACEuniform] and considering CT numbers [ACECT#]) on planning CTs and control CBCTs for patients with cervical and breast cancer as well as phantom-simulated skin cancer cases. Assessing dosimetric deviations between the planning CTs and control CBCTs acquired during the treatment course served to estimate interfractional implant variations.

RESULTS

The comparison of ACEuniform-ACECT# deviations between planning CTs and control CBCTs revealed no statistically significant difference for almost all examined dose parameters. Dosimetric deviations between model-based dose calculations and TG-43 were partly significant but of small magnitude (< 10 cGy per fraction). Interfractional dosimetric variations were substantially larger than the dosimetric differences found between the various dose calculation procedures.

CONCLUSION

Model-based dose calculation based on modern CBCT imaging was suitable. However, the found differences between these calculations and the TG-43 formalism should be investigated in dose-outcome analyses. The observed interfractional dosimetric variations revealed the importance of performing treatment quality assurance.

Phantom study of a fully automatic radioactive seed placement robot for the treatment of skull base tumours

BACKGROUND

Interstitial brachytherapy is a form of intensive local irradiation that facilitates the effective protection of surrounding structures and the preservation of organ functions, resulting in a favourable therapeutic response. As surgical robots can perform needle placement with a high level of accuracy, our team developed a fully automatic radioactive seed placement robot, and this study aimed to evaluate the accuracy and feasibility of fully automatic radioactive seed placement for the treatment of tumours in the skull base.

METHODS

A fully automatic radioactive seed placement robot was established, and 4 phantoms of skull base tumours were built for experimental validation. All the phantoms were subjected to computed tomography (CT) scans. Then, the CT data were imported into the Remebot software to design the preoperative seed placement plan. After the phantoms were fixed in place, navigation registration of the Remebot was carried out, and the automatic seed placement device was controlled to complete the needle insertion and particle placement operations. After all of the seeds were implanted in the 4 phantoms, postoperative image scanning was performed, and the results were verified via image fusion.

RESULTS

A total of 120 seeds were implanted in 4 phantoms. The average error of seed placement was (2.51 ± 1.44) mm.

CONCLUSION

This study presents an innovative, fully automated radioactive particle implantation system utilizing the Remebot device, which can successfully complete automated localization, needle insertion, and radioactive particle implantation procedures for skull base tumours. The phantom experiments showed the robotic system to be reliable, stable, efficient and safe. However, further research on the needle-soft tissue interaction and deformation mechanism of needle puncture is still needed.

Clinical Efficacy and Openness to New Challenges of Low Dose Rate Brachytherapy for Prostate Cancer

Over a century ago, low-dose-rate (LDR) brachytherapy was introduced to treat prostate cancer (PCa). Since then, it has been widely applied worldwide, including in East Asia. LDR brachytherapy has been performed in 88 institutes in Japan. Beneficial clinical outcomes of LDR brachytherapy for intermediate-to-high-risk PCa have been demonstrated in large clinical trials. These clinical outcomes were achieved through advances in methods, such as urological precise needle puncture and seed placement, and the quantitative decision making regarding radiological parameters by radiation oncologists. The combined use of LDR brachytherapy with other therapeutic modalities, such as external beam radiation and androgen deprivation therapy, for the clinical risk classification of PCa has led to better anticancer treatment efficacy. In this study, we summarized basic LDR brachytherapy findings that should remain unchanged and be passed down in urology departments. We also discussed the applications of LDR brachytherapy for PCa in various clinical settings, including focal and salvage therapies. In addition, we highlighted technologies associated with brachytherapy that are under development.

MR-guided HDR prostate brachytherapy with teleoperated steerable needles

Conformity of tumour volumes and dose plans in prostate brachytherapy (BT) can be constrained by unwanted needle deflections, needle access restrictions and visualisation limitations. This work validates the feasibility of teleoperated robotic control of an active steerable needle using magnetic resonance (MR) for guidance. With this system, perturbations can be counteracted and critical structures can be circumvented to access currently inaccessible areas. The system comprises of (1) a novel steerable needle, (2) the minimally invasive robotics in an MR environment (MIRIAM) system, and (3) the daVinci Research Kit (dVRK). MR scans provide visual feedback to the operator controlling the dVRK. Needle steering is performed along curved trajectories to avoid the urethra towards targets (representing tumour tissue) in a prostate phantom with a targeting error of 1.2 ± 1.0 mm. This work shows the potential clinical applicability of active needle steering for prostate BT with a teleoperated robotic system in an MR environment.

Modern Tools for Modern Brachytherapy

This review aims to showcase the brachytherapy tools and technologies that have emerged during the last 10 years. Soft-tissue contrast using magnetic resonance and ultrasound imaging has seen enormous growth in use to plan all forms of brachytherapy. The era of image-guided brachytherapy has encouraged the development of advanced applicators and given rise to the growth of individualised 3D printing to achieve reproducible and predictable implants. These advances increase the quality of implants to better direct radiation to target volumes while sparing normal tissue. Applicator reconstruction has moved beyond manual digitising, to drag and drop of three-dimensional applicator models with embedded pre-defined source pathways, ready for auto-recognition and automation. The simplified TG-43 dose calculation formalism directly linked to reference air kerma rate of high-energy sources in the medium water remains clinically robust. Model-based dose calculation algorithms accounting for tissue heterogeneity and applicator material will advance the field of brachytherapy dosimetry to become more clinically accurate. Improved dose-optimising toolkits contribute to the real-time and adaptive planning portfolio that harmonises and expedites the entire image-guided brachytherapy process. Traditional planning strategies remain relevant to validate emerging technologies and should continue to be incorporated in practice, particularly for cervical cancer. Overall, technological developments need commissioning and validation to make the best use of the advanced features by understanding their strengths and limitations. Brachytherapy has become high-tech and modern by respecting tradition and remaining accessible to all.

Investigation of Radiochromic Film Use for Source Position Verification through a LINAC On-Board Imager (OBI)

Background and Objectives: Quality assurance is an integral part of brachytherapy. Traditionally, radiographic films have been used for source position verification, however, in many clinics, computerized tomography simulators have replaced conventional simulators, and computerized radiography systems have replaced radiographic film processing units. With these advances, the problem of controlling source position verification without traditional radiographic films and conventional simulators has appeared. Materials and Methods: In this study, we investigated an alternative method for source position verification for brachytherapy applications. Source positions were evaluated using Gafchromic™ RTQA2 and EBT3 film and visually compared to exposed RTQA radiochromic film when using a Nucletron Oldelft Simulix HP conventional simulator and a Gammamed 12-i brachytherapy device for performance evaluation. Gafchromic film autoradiography was performed with a linear accelerator (LINAC) on-board imager (OBI). Radiochromic films are very suitable for evaluation by visual inspection with a LINAC OBI. Results: The results showed that this type of low-cost, easy-to-find material can be used for verification purposes under clinical conditions. Conclusions: It can be concluded that source-position quality assurance may be performed through a LINAC OBI device.

Optimisation and validation of a co-manipulated robot for brachytherapy procedure

BACKGROUND

Low-dose rate brachytherapy is the referent treatment for early-stage prostate cancer and consists in manually inserting radioactive seeds within the organ to destroy tumorous cells. This treatment is inaccurate leading to side effects. Researchers developed robots to improve this technique. Despite ameliorating accuracy, they cannot be clinically used because of size and acceptability. Therefore, a 6-DOF parallel and co-manipulated robot is proposed to meet these requirements.

METHODS

To fulfil the application requirements, a compact design was modelled. The robot's optimal dimensions were defined by establishing kinematics and implementing genetic algorithm. The robot's relevance was evaluated by measuring workspace and needle placement errors.

RESULTS

The robot fits into a cube of 300 × 300 × 300 mm³ and provides a free-singularity workspace of 55 × 55 × 150 mm³ with a possible end-effector rotation of 15° and a needle placement error <3 mm.

CONCLUSION

The results are promising and prove that our robot fulfils the application requirements and presents a beneficial alternative to the manual procedure.

AAPM Task Group Report 303 endorsed by the ABS: MRI Implementation in HDR Brachytherapy-Considerations from Simulation to Treatment

The Task Group (TG) on Magnetic Resonance Imaging (MRI) Implementation in High Dose Rate (HDR) Brachytherapy - Considerations from Simulation to Treatment, TG 303, was constituted by the American Association of Physicists in Medicine's (AAPM's) Science Council under the direction of the Therapy Physics Committee, the Brachytherapy Subcommittee, and the Working Group on Brachytherapy Clinical Applications. The TG was charged with developing recommendations for commissioning, clinical implementation, and on-going quality assurance (QA). Additionally, the TG was charged with describing HDR brachytherapy (BT) workflows and evaluating practical consideration that arise when implementing MR imaging. For brevity, the report is focused on the treatment of gynecologic and prostate cancer. The TG report provides an introduction and rationale for MRI implementation in BT, a review of previous publications on topics including available applicators, clinical trials, previously published BT related TG reports, and new image guided recommendations beyond CT based practices. The report describes MRI protocols and methodologies, including recommendations for the clinical implementation and logical considerations for MR imaging for HDR BT. Given the evolution from prescriptive to risk-based QA,¹ an example of a risk-based analysis using MRI-based, prostate HDR BT is presented. In summary, the TG report is intended to provide clear and comprehensive guidelines and recommendations for commissioning, clinical implementation, and QA for MRI-based HDR BT that may be utilized by the medical physics community to streamline this process. This report is endorsed by the American Brachytherapy Society (ABS). This article is protected by copyright. All rights reserved.

Preliminary Study of a Modular MR-Compatible Robot for Image-Guided Insertion of Multiple Needles

Percutaneous needle-based interventions such as transperineal prostate brachytherapy require the accurate placement of multiple needles to treat cancerous lesions within the target organ. To guide needle placement, magnetic resonance imaging (MRI) offers excellent visualization of the target lesion without the need for ionizing radiation. To date, multi-needle insertion relies on a grid template, which limits the ability to steer individual needles. This work describes an MR-compatible robot designed for the sequential insertion of multiple non-parallel needles under MR guidance. The 6-DOF system is designed with an articulated arm to extend the reach of the robot. This strategy presents a novel approach enabling the robot to maneuver around existing needles while minimizing the footprint of the robot. Forward kinematics as well as optimization-based inverse kinematics are presented. The impact of the robot on image quality was tested for four sequences (T1w-TSE, T2w-TSE, THRIVE and EPI) on a 3T Philips Achieva system. Quantification of the signal-to-noise ratio showed a 46% signal loss in a gelatin phantom when the system was powered on but no further adverse effects when the robot was moving. Joint level testing showed a maximum error of 2.10 ± 0.72°s for revolute joints and 0.31 ± 0.60 mm for prismatic joints. The theoretical workspace spans the proposed clinical target surface of 10 x 10 cm. Lastly, the feasibility of multi-needle insertion was demonstrated with four needles inserted under real-time MR-guidance with no visible loss in image quality.

Multiple direction needle-path planning and inverse dose optimization for robotic low-dose rate brachytherapy

PURPOSE

Robotic systems to assist needle placements for low-dose rate brachytherapy enable conformal dose planning only restricted to path planning around risk structures. We report a treatment planning system (TPS) combining multiple direction needle-path planning with inverse dose optimization algorithms.

METHODS

We investigated in a path planning algorithm to efficiently locate needle injection points reaching the target volume without puncturing risk structures. A candidate needle domain with all combinations of trajectories is used for the optimization process. We report a modular algorithm for inverse radiation plan optimization. The initial plan with V100>99% is generated by the "greedy optimizer". The "remove-seed algorithm" reduces the number of seeds in the high dose regions. The "depth-optimizer" varies the insertion depth of the needles. The "coverage-optimizer" locates under-dosed areas in the target volume and supports them with an additional amount of seeds. The dose calculation algorithm is benchmarked on an image set of a phantom with a liver metastasis (prescription dose Dpr=100Gy) and is re-planned in a commercial CE-marked TPS to compare the calculated dose grids using a global gamma analysis. The inverse optimizer is benchmarked by calculating 10 plans on the same phantom to investigate the stability and statistical variability of the dose parameters.

RESULTS

The path planning algorithm efficiently removes 72.5% of all considered injection points. The candidate needle domain consists of combinations of 1971 tip points and 827 injection points. The global gamma analysis with gamma 1%=2.9Gy, 1mm showed a pass rate of 98.5%. The dose parameters were V100=99.1±0.3%, V150=76.4±2.5%, V200=44.5±5.5% and D90=125.9±3.6Gy and 10.7±1.3 needles with 34.0±0.8 seeds were used. The median of the TPS total running time was 4.4minutes.

CONCLUSIONS

The TPS generates treatment plans with acceptable dose coverage in a reasonable amount of time. The gamma analysis shows good accordance to the commercial TPS. The TPS allows taking full advantage of robotic navigation tools to enable a new precise and safe method of minimally invasive low-dose-rate brachytherapy.

Coordinated control of a 3DOF cartesian robot and a shape memory alloy-actuated flexible needle for surgical interventions: a non-model-based control method

Success of any needle-based medical procedures depends on accurate placement of the needle at the target location. However, accurate targeting and control of flexible self-actuating (active) needle are challenging. We have developed a shape memory alloy-actuated flexible needle steered by a 3D Cartesian robot and performed a comparative study of four, non-model-based, coordinated control methodologies for the combined robot steering and flexible-needle insertion process for surgical interventions. Investigated four controllers are: proportional–integral–derivative (PID), PID with the cubic of positional error term (PID-P3), static PID sliding mode controller, and robust adaptive PID sliding mode controller (RAPID-SMC). Relative efficacies of these controllers are demonstrated by performing experiements using a tissue-mimicking soft material phantom. Results from experiments have reavealed that RAPID-SMC is superior to other three controllers.

Precision Interventional Brachytherapy: A Promising Strategy Toward Treatment of Malignant Tumors

Precision interventional brachytherapy is a radiotherapy technique that combines radiation therapy medicine with computer network technology, physics, etc. It can solve the limitations of conventional brachytherapy. Radioactive drugs and their carriers change with each passing day, and major research institutions and enterprises worldwide have conducted extensive research on them. In addition, the capabilities of interventional robotic systems are also rapidly developing to meet clinical needs for the precise delivery of radiopharmaceuticals in interventional radiotherapy. This study reviews the main radiopharmaceuticals, drug carriers, dispensing and fixation technologies, and interventional robotic precision delivery systems used in precision brachytherapy of malignant tumors. We then discuss the current needs in the field and future development prospects in high-precision interventional brachytherapy.

Design of a seed implantation robot with counterbalance and soft tissue stabilization mechanism for prostate cancer brachytherapy

This article focuses on the topic of the structural design of surgical radioactive surgery robot for prostate cancer. To improve the weight-to-payload ratio of surgery robot end-effector, the energy consumption and stability of robot joint drive and reducing the displacement and deformation of needle insertion in soft tissue. This article discusses the new static torque balancing method and multi-needle insertion soft tissue stabilization mechanisms that may be used in previously articulated seed implantation robots. Compared with the existing balancing system schemes, we adopt the idea of mutual conversion of gravitational potential energy and elastic potential energy and establish a static balancing model. With preloaded displacement parameter of the spring α, the variable gravity torque balance of robot arm can be achieved. Torque and equivalent gravity balancing distribution with the spring balance system and the quantitative evaluation experiment were performed, and experiment results provide evidence that these spring balance devices can basically compensate the gravity torque of the robot arm. In addition, we used nonlinear spring–damper model to establish multi-needles insertion soft tissue force model. Then, a variable multi-needle insertion soft tissue stabilization device is designed with six working modes. The innovative design of this device is the use of the first four needles that are introduced simultaneously on either side of the midline. Initially completed displacement simulation of different numbers of needle insertion prostate tissue, experiment results indicate that multi-needle puncture mechanism could reduce prostate displacement in the y- or z-direction. By this method, the prostate may be fixed, thus this mechanism maybe reduces rotation of the prostate and enabling subsequent needles to be inserted accurately.

Eligibility criteria according to EAU/ESTRO/SIOG guidelines for exclusive iodine-125 brachytherapy for intermediate-risk prostate adenocarcinoma patients: impact on relapse-free survival

Purpose

Iodine-125 (¹²⁵I) brachytherapy (BT) alone for intermediate-risk (IR) prostate adenocarcinoma (PCA) is controversial. The purpose of the study was to investigate potential predictive factors in selected IR-PCA patients treated with BT.

Material and methods

Among 547 patients treated with ¹²⁵I BT between 2003 and 2013, 149 IR-PCA cases were selected according to NCCN classification after an additional exclusion of patients with prostate specific antigen (PSA) > 15 ng/ml and ISUP group 3. A relapse was defined as a biochemical failure, using ASTRO Phoenix definition, or a relapse identified on imaging. Survival curves were estimated with Kaplan-Meier method. Potential prognostic variables including EAU/ESTRO/SIOG guidelines eligibility criteria were analyzed using univariate and Cox’s proportional hazards regression analysis.

Results

Of the 149 IR patients, 112 were classified as favorable, with 69 cases eligible to BT according to EAU/ESTRO/SIOG guidelines, and 37 patients were identified as unfavorable as per NCCN. Androgen deprivation therapy (ADT) was applied in 6 patients only. Percentage of positive biopsy cores were ≤ 33% and ≥ 50% for 119 and 11 patients, respectively. With a median follow-up of 8.5 years, 30 patients experienced a relapse. 10-year overall survival, progression-free survival (PFS), and relapse-free survival (RFS) were 84% (95% CI: 75-90%), 66% (95% CI: 56-75%), and 77% (95% CI: 67-84%), respectively. Failure to meet EAU/ESTRO/SIOG criteria was significantly associated with a lower RFS (p = 0.0267, HR = 2.37 [95% CI: 1.10-5.08%]).

Conclusions

Brachytherapy is an effective treatment for selected IR-PCA cases. Patients who were not eligible according to EAU/ESTRO/SIOG guidelines demonstrated a lower RFS.

MR compatibility, safety and accuracy of the redesigned UMC Utrecht single needle implant device

Purpose. The Utrecht single needle implant device (SNID) was redesigned to increase needle insertion velocity. The purpose of this study is to evaluate the magnetic resonance compatibility, safety and accuracy of the implant device preparing its application in a patient study to investigate the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.Methods. Several experiments were performed to evaluate the mechanical and radiofrequency safety of the needle system, the magnetic field perturbation, the calibration of the implant device in the MR coordinate system, functioning of the implant device during imaging and accuracy of needle insertion.Results. Endurance experiments showed the mechanical safety of the needle system. Magnetic field perturbation was acceptable with induced image distortions smaller than 0.5 mm for clinical MR sequences. Calibration of the implant device in the MR coordinate system was reproducible with average error (mean±standard deviation) of 0.2 ± 0.4 mm, 0.1 ± 0.3 mm and 0.6 ± 0.6 mm in thex,y- andz- direction, respectively. The RF safety measurement showed for clinical MR imaging sequences maximum temperature rises of 0.2 °C at the entry and tip points of the needle. Simultaneous functioning of the implant device and imaging is possible albeit with some intensity band artifacts in the fast field echo images. Finally, phantom measurements showed deviations amounting 2.5-3.6 mm measured as target-to-needle distance at a depth of 12 cm.Conclusions. This preclinical evaluation showed that the MR compatibility, safety and accuracy of the redesigned UMC Utrecht SNID allow its application in a patient study on the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.

A novel multi-DoF surgical robotic system for brachytherapy on liver tumor: Design and control

Purpose

Radioactive seed implantation is an effective invasive treatment method for malignant liver tumors in hepatocellular carcinomas. However, challenges of the manual procedure may degrade the efficacy of the technique, such as the high accuracy requirement and radiation exposure to the surgeons. This paper aims to develop a robotic system and its control methods for assisting surgeons on the treatment.

Method

We present an interventional robotic system, which consists of a 5 Degree-of-Freedom (DoF) positioning robotic arm (a 3-DoF translational joint and a 2-DoF revolute joint) and a needle actuator used for needle insertion and radioactive seeds implantation. Control strategy is designed for the system to ensure the safety of the motion. In the designed framework, an artificial potential field (APF)-based motion planning and an ultrasound (US) image-based contacting methods are proposed for the control.

Result

Experiments were performed to evaluate position and orientation accuracy as well as validate the motion planning procedure of the system. The mean and standard deviation of targeting error is 0.69 mm and 0.33 mm, respectively. Needle placement accuracy is 1.10 mm by mean. The feasibility of the control strategy, including path planning and the contacting methods, is demonstrated by simulation and experiments based on an abdominal phantom.

Conclusion

This paper presents a robotic system with force and US image feedback in assisting surgeons performing brachytherapy on liver tumors. The proposed robotic system is capable of executing an accurate needle insertion task with by optical tracking. The proposed methods improve the safety of the robot’s motion and automate the process of US probe contacting under the feedback of US-image.

Image-guided robots for low dose rate prostate brachytherapy: Perspectives on safety in design and use

BACKGROUND

Image-guided brachytherapy (BT) robots can be used to assist urologists during seed implantation, thereby improving therapeutic effects. However, safety issues must be considered in the design of such robots, including their structure, mechanical movements, function, materials and actuators. Previous reviews focused on image-guided prostate BT robot technology (e.g., imaging and robot navigation technology and robot system introduction); however, this review is the first time that safety issues have been investigated as part of a study on low-dose-rate (LDR) prostate BT robots.

METHODS

Multiple electronic databases were searched for LDR prostate BT robot articles published during the last 24 years (1996-2020), with a particular focus on two aspects of robots: safety in design and use.

RESULTS

We retrieved a total of 26 LDR prostate BT robots. BT robots were divided into ultrasound, computed tomography, magnetic resonance imaging and fusion-guided systems. The conditions associated with each system were then analysed to develop a set of requirements for the safety of prostate BT robots. Recommendations are also provided for future BT robot development.

CONCLUSIONS

The transrectal approach for prostate seed implantation is safer than the traditional transperineal approach. Research into the control of a steerable needle by the urologists and robot, the needle deflection model, and robotic automated needle changing and seed injection equipment should be pursued in a future study.

Design and Kinematics of a Comanipulated Robot Dedicated to Prostate Brachytherapy

In brachytherapy, the manual implantation of seeds is not accurate leading to side effects and limiting the use of new procedures. Robotics solutions have to be fully suitable for medical applications especially considering the operating room. This paper investigates a delta robot solution for improving the accuracy of the prostate brachytherapy procedure by proposing a compact and lightweight robot. In addition, the design was thought as a comanipulated robot for a better acceptability and human–machine interaction. The robot kinematics and singularities were determined and the theoretical capability in term of resolution and force feedback was evaluated. A prototype was built in order to experimentally measure the capability of this first prototype.

Physician-Friendly Tool Center Point Calibration Method for Robot-Assisted Puncture Surgery

After each robot end tool replacement, tool center point (TCP) calibration must be performed to achieve precise control of the end tool. This process is also essential for robot-assisted puncture surgery. The purpose of this article is to solve the problems of poor accuracy stability and strong operational dependence in traditional TCP calibration methods and to propose a TCP calibration method that is more suitable for a physician. This paper designs a special binocular vision system and proposes a vision-based TCP calibration algorithm that simultaneously identifies tool center point position (TCPP) and tool center point frame (TCPF). An accuracy test experiment proves that the designed special binocular system has a positioning accuracy of ±0.05 mm. Experimental research shows that the magnitude of the robot configuration set is a key factor affecting the accuracy of TCPP. Accuracy of TCPF is not sensitive to the robot configuration set. Comparison experiments show that the proposed TCP calibration method reduces the time consumption by 82%, improves the accuracy of TCPP by 65% and improves the accuracy of TCPF by 52% compared to the traditional method. Therefore, the method proposed in this article has higher accuracy, better stability, less time consumption and less dependence on the operations than traditional methods, which has a positive effect on the clinical application of high-precision robot-assisted puncture surgery.

Needle placement accuracy in CT-guided robotic post mortem biopsy

Forensic autopsies include a thorough examination of the corpse to detect the source or alleged manner of death as well as to estimate the time since death. However, a full autopsy may be not feasible due to limited time, cost or ethical objections by relatives. Hence, we propose an automated minimal invasive needle biopsy system with a robotic arm, which does not require any online calibrations during a procedure. The proposed system can be easily integrated into the workflow of a forensic biopsy since the robot can be flexibly positioned relative to the corpse. With our proposed system, we performed needle insertions into wax phantoms and livers of two corpses and achieved an accuracy of 4.34 ± 1.27 mm and 10.81 ± 4.44 mm respectively.

Characterization and registration of 3D ultrasound for use in permanent breast seed implant brachytherapy treatment planning

PURPOSE

Permanent breast seed implant (PBSI) brachytherapy is a novel technique for early-stage breast cancer. Computed tomography (CT) images are used for treatment planning and freehand 2D ultrasound for implant guidance. The multimodality imaging approach leads to discrepancies in target identification. To address this, a prototype 3D ultrasound (3DUS) system was recently developed for PBSI. In this study, we characterize the 3DUS system performance, establish QA baselines, and develop and test a method to register 3DUS images to CT images for PBSI planning.

METHODS AND MATERIALS

3DUS system performance was characterized by testing distance and volume measurement accuracy, and needle template alignment accuracy. 3DUS-CT registration was achieved through point-based registration using a 3D-printed model designed and constructed to provide visible landmarks on both images and tested on an in-house made gel breast phantom.

RESULTS

The 3DUS system mean distance measurement accuracy was within 1% in axial, lateral, and elevational directions. A volumetric error of 3% was observed. The mean needle template alignment error was 1.0° ± 0.3 ° and 1.3 ± 0.5 mm. The mean 3DUS-CT registration error was within 3 mm when imaging at the breast centre or across all breast quadrants.

CONCLUSIONS

This study provided baseline data to characterize the performance of a prototype 3DUS system for PBSI planning and developed and tested a method to obtain accurate 3DUS-CT image registration for PBSI planning. Future work will focus on system validation and characterization in a clinical context as well as the assessment of impact on treatment plans.

Prospect of robotic assistance for fully automated brachytherapy seed placement into skull base: Experimental validation in phantom and cadaver

BACKGROUND AND PURPOSE

To investigate the feasibility and accuracy of robot-assisted brachytherapy for skull base tumours.

MATERIAL AND METHODS

A custom robot system was tested on both phantom and cadaveric specimen. Cone beam CT (CBCT) images were transferred to the graphical user interface (GUI) for planning trajectories and the data were sent to the robot control unit. Following registration, the puncture needle was inserted into the target by the robot under navigation guidance, and seeds were implanted. Placement error was instantly displayed on the GUI; the result was verified after postoperative image scanning.

RESULTS

A total of 150 seeds (100 for phantom experiments, 50 for cadaveric studies) were deposited by the robot system. In phantom experiments the mean placement error was 0.57 ± 0.21 mm (measured by the navigation system) vs. 1.41 ± 0.38 mm (measured by image fusion) (p < 0.001); in cadaveric studies the corresponding figures were 0.60 ± 0.30 mm vs. 2.48 ± 0.32 mm (p < 0.001). There was no significant difference for comparison of accuracy test in phantom experiments (p = 0.173) as well as in cadaveric studies (p = 0.354). Accuracy was better in the phantom experiment than in cadaveric studies (p < 0.001).

CONCLUSIONS

The performance of robot-assisted skull base brachytherapy is feasible and accurate. Dosimetric coverage will need to be demonstrated in further studies.

Risk Management for the Reliability of Robotic Assisted Treatment of Non-resectable Liver Tumors

Hepatic cancers represent an important worldwide health issue where surgery alone in most cases is not a feasible therapeutic solution since most tumors are non-resectable. Despite targeted therapies showing positive results in other areas of cancer treatment, in the case of liver tumors, no low-risk delivery methods have been identified. Based on a risk assessment approach, this paper proposes a technical solution in the form of a robotic system capable of achieving a reliable delivery method for targeted treatment, focusing on the patient safety and therapeutic efficiency. The design of the robotic system starts from the definition of the design constraints with respect to the medical protocol. An analytical hierarchy process is used to prioritize the data correlated with the technical characteristics of a new robotic system, aiming to minimize risks associated with the medical procedure. In a four-phase quality function deployment, the technical solution is evaluated with respect to the quality characteristics, functions, subsystems, and components aiming to achieve a safe and reliable system with high therapeutic efficiency. The results lead to the concept of HeRo, a parallel robotic system for the reliable targeted treatment of non-resectable liver tumors.

US/MRI Guided Robotic System for the Interventional Treatment of Prostate

Needle-based percutaneous prostate interventions include biopsy and brachytherapy and the former is the gold standard for the diagnosis of prostate cancer and the latter is often used in the treatment of prostate cancer. This paper introduces a novel robotic assistant system for prostate intervention and the system architecture and workflow are described, which is significant for the design of similar systems. In order to offer higher precision and better real-time performance, a Ultrasound (US)/Magnetic Resonance Imaging (MRI) fusion method is proposed to guide the procedures in this study. Moreover, image registration is a key step and a hot issue in image fusion, especially in multimodal image fusion. In this work, we adopt a novel registration method based on active demons and optic flow for prostate image fusion. To verify the availability of the system, we evaluate our approach of the US/MRI image fusion by using data acquired from six patients, and root mean square error (RMSE) for anatomical landmarks is 3.15[Formula: see text]mm. In order to verify the accuracy and validity of the system developed in this paper, a system experimental platform was built and used for bionic tissue puncture of prostate under the guidance of MR and Transrectal Ultrasound (TRUS) fusion images. The experimental results show that the deviations of the final actual needle points of the three target points on the bionic tissue model measured in the laboratory environment are less than 2.5[Formula: see text]mm.

A novel auto-positioning method in Iodine-125 seed brachytherapy driven by preoperative planning

Iodine-125 seed brachytherapy has great potential in the treatment of malignant tumors. However, the success of this treatment is highly dependent on the ability to accurately position the coplanar template. The aim of this study was to develop an auto-positioning system for the template with a design focus on efficiency and accuracy. In this study, an auto-positioning system was presented, which was composed of a treatment planning system (TPS) and a robot-assisted system. The TPS was developed as a control system for the robot-assisted system. Then, the robot-assisted system was driven by the output of the TPS to position the template. Contrast experiments for error validation were carried out in a computed tomography environment to compare with the traditional positioning method (TPM). Animal experiments on Sprague-Dawley rats were also carried out to evaluate the auto-positioning system. The error validation experiments and animal experiments with this auto-positioning system were successfully carried out with improved efficiency and accuracy. The error validation experiments achieved a positioning error of 1.04 ± 0.19 mm and a positioning time of 23.15 ± 2.52 min, demonstrating a great improvement compared with the TPM (2.55 ± 0.21 mm and 40.35 ± 2.99 min, respectively). The animal experiments demonstrated that the mean deviation of the seed position was 0.75 mm. The dose-volume histogram of the preoperative planning showed the same as the postoperative dosimetry validation. A novel auto-positioning system driven by preoperative planning was established, which exhibited higher efficiency and accuracy compared with the TPM.

3D Manipulation of an Active Steerable Needle via Actuation of Multiple SMA Wires

Many medical procedures such as brachytherapy, thermal ablations, and biopsies are performed using needle-based procedures. In this work, 3D manipulation of an active needle realized by multiple Shape Memory Alloy (SMA) actuators was first predicted by Finite Element Analyses (FEA), and then demonstrated by a fabricate prototype. The FEA results were validated by planar deflection of an active needle. A similar FEA was developed to predict 3D manipulation of the active needle. For 17-gage needle, a maximum of 26° reversible deflection was achieved in 3D space via actuation forces of a 0.127 mm SMA wire. A scaled prototype was also developed and tested to show the feasibility of developing a 3D steering active needle with multiple actuators.

Post-implant analysis in permanent breast seed implant: automated plan reconstruction using simulated annealing

Purpose

Post-implant analysis in permanent breast seed implant (PBSI) brachytherapy is an important component of the quality assurance process that indicates dosimetric quality relevant to patient outcome, indicating salvage therapy if inadequate, as well as providing feedback to the brachytherapy team to improve future treatments. To measure geometric indices on implant quality, plan reconstruction must be performed to correlate each planned and post-implant seed location. In this work, a simulated-annealing-based algorithm is developed to perform this plan reconstruction automatically.

Material and methods

The plan reconstruction algorithm was developed in MATLAB, taking the patient pre-treatment and post-implant (Day 0) plan and associated contours as inputs. For 19 treated patients, a reconstruction was obtained that defined the correspondence between each planned and post-implant seed. The simulated-annealing algorithm was used to reconstruct each patient 10 times to assess the variability in convergence. Manual reconstructions performed by at least two independent observers to obtain consensus were defined as the ground truth; these were compared to the automatic reconstructions obtained by the algorithm. Metrics on seed placement accuracy and needle strand angulation were calculated for the patients.

Results

The algorithm performed reconstructions on 19 patients (1235 seeds) with ground-truth reconstructions, obtaining 97 ± 8% correct matches. This strong performance indicates the ability to incorporate this algorithm into the clinical quality assurance workflow.

Conclusions

The plan reconstruction algorithm developed herein performed very well in a 19-patient cohort. This algorithm can be incorporated into the clinical process to assist in the assessment of center-specific seed placement accuracy and can be used to gather implant metrics in an automated, standardized fashion for future PBSI trials.

System and path planning algorithm for low-kV X-ray free-form surface irradiation

OBJECTIVE

Intraoperative radiotherapy (IORT) after surgical resection using a low-kV-X-ray source is a proven method used in cancer treatment. However, the shape and size of the targeted surface area are limited to the size of the available applicators. This can lead to nonconformal and therefore suboptimal treatment for many patients.

METHODS

A system is proposed comprising an X-ray source with an applicator for surface irradiation mounted on a robotic arm. This is controlled by an algorithm designed for planning the required continuous path, enabling irradiation of any desired shape with a controlled dose distribution.

RESULTS

The system is shown to be capable of irradiating areas composed of rectangles on a flat surface with a homogeneity index of less than 7% inside the targeted area.

CONCLUSION

The presented results demonstrate the potential of the proposed setup to eliminate the current limitations, leading to better treatment of patients.

EXPERIMENTAL STUDY OF NEEDLE INSERTION STRATEGIES OF SEED IMPLANTATION ARTICULATED ROBOT

This paper discusses several new mechanisms that may be used in prostate cancer seed implant robotics. Aiming at the limitation of human body structure space, and in order to improve robotic kinematic dexterity and execution efficiency. We have developed an articulated seed implantation robot with three-dimensional transrectal ultrasound navigation. It is noteworthy that the organization will produce displacement, deformation and needle tip deflection and other issues while needle inserting prostate. In order to improve positioning accuracy of robot to control the puncture needle, a piezoelectric vibration and rotation needle insertion device is designed and developed. Based on the evaluation experiment of vibration and rotation needle insertion, a high accuracy mixed needle insertion strategy is proposed and the corresponding control software is designed. Finally, the insertion force evaluation experiment is completed by mixed needle insertion strategy, and the experimental results validate the effectiveness of this method.

Advances in Radiotherapy for Prostate Cancer Treatment

Major categories of radiotherapy (RT) for prostate cancer (CaP) treatment are: (1) external beam RT (EBRT), and (2) brachytherapy (BT). EBRT are performed using different techniques like three-dimensional conformal RT (3D-CRT), intensity modulated RT (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT), stereotactic radiosurgery (SRS) and intensity modulated proton therapy (IMPT), etc., using a variety of radiation delivery machines, such as a linear accelerator (Linac), Cyberknife robotic system, Gamma knife, Tomotherapy and proton beam machine. The primary advantage of proton beam therapy is sparing of normal tissues and organ at risks (OARs) with comparable coverage of the tumor volume. MR-Linac is the latest addition in the image-guided RT. Robot-assisted brachytherapy is one of the latest technological innovations in the field. With the advancement of technology, radiation therapy for prostate cancer can be improved using high quality multimodal imaging, robot-assistance for brachytherapy as well as EBRT. This chapter presents the advances in radiation therapy for the treatment of prostate cancer.

The Current State of MR Imaging-targeted Biopsy Techniques for Detection of Prostate Cancer

Systematic transrectal ultrasonography (US)-guided biopsy is the standard approach for histopathologic diagnosis of prostate cancer. However, this technique has multiple limitations because of its inability to accurately visualize and target prostate lesions. Multiparametric magnetic resonance (MR) imaging of the prostate is more reliably able to localize significant prostate cancer. Targeted prostate biopsy by using MR imaging may thus help to reduce false-negative results and improve risk assessment. Several commercial devices are now available for targeted prostate biopsy, including in-gantry MR imaging-targeted biopsy and real-time transrectal US-MR imaging fusion biopsy systems. This article reviews the current status of MR imaging-targeted biopsy platforms, including technical considerations, as well as advantages and challenges of each technique. ^© RSNA, 2017.

Design and validation of a CT-guided robotic system for lung cancer brachytherapy

PURPOSE

Currently, lung brachytherapy in clinical setting is a complex procedure. Operation accuracy depends on accurate positioning of the template; however, it is difficult to guarantee the positioning accuracy manually. Application of robotic-assisted systems can simplify the procedure and improve the manual positioning accuracy. Therefore, a novel CT-guided robotic system was developed to assist the lung cancer brachytherapy.

METHODS

A four degree-of-freedom (DOF) robot, controlled by a lung brachytherapy treatment planning system (TPS) software, was designed and manufactured to assist the template positioning. Target position of the template can be obtained from the treatment plan, thus the robot is driven to the target position automatically. The robotic system was validated in both the laboratory and the CT environment. In laboratory environment, a 3D laser tracker and an inertial measurement unit (IMU) were used to measure the mechanical accuracy in air, which includes positioning accuracy and position repeatability. Working reliability was also validated in this procedure by observing the response reliability and calculating the position repeatability. Imaging artifacts and accuracy of the robot registration were validated in the CT environment by using an artificial phantom with fiducial markers. CT images were obtained and used to test the image artifact and calculate the registration accuracy. Phantom experiments were conducted to test the accuracy of needle insertion by using a transparent hydrogel phantom with a high imitation artificial phantom. Also, the efficiency was validated in this procedure by comparing time costs in manual positioning with robotic positioning under the same experimental conditions.

RESULTS

The robotic system achieved the positioning accuracy of 0.28 ± 0.25 mm and the position repeatability of 0.09 ± 0.11 mm. Experimental results showed that the robot was CT-compatible and responded reliably to the control commands. The mean registration accuracy of the robotic system was 0.49 ± 0.29 mm. Phantom experiments indicated that the accuracy of needle insertion was 1.5 ± 1.7 mm at a depth ranging from 30 to 80 mm. The time used to adjust the template to the target position was 12 min on average by robotic system automatically. An average of 30 min was saved compared with the manual positioning procedure in phantom experiments.

CONCLUSIONS

This paper describes the design and experimental validation of a novel CT-guided robotic system for lung cancer brachytherapy. The robotic system was validated in a number of aspects which prove that it was capable of locating the template with clinically acceptable accuracy in the CT environment. All experimental results indicated that the system is reliable and ready to be applied to further studies on animals.

Brachytherapy patient safety events in an academic radiation medicine program

PURPOSE

To describe the incidence and type of brachytherapy patient safety events over 10 years in an academic brachytherapy program.

METHODS AND MATERIALS

Brachytherapy patient safety events reported between January 2007 and August 2016 were retrieved from the incident reporting system and reclassified using the recently developed National System for Incident Reporting in Radiation Treatment taxonomy. A multi-incident analysis was conducted to identify common themes and key learning points.

RESULTS

During the study period, 3095 patients received 4967 brachytherapy fractions. An additional 179 patients had MR-guided prostate biopsies without treatment as part of an interventional research program. A total of 94 brachytherapy- or biopsy-related safety events (incidents, near misses, or programmatic hazards) were identified, corresponding to a rate of 2.8% of brachytherapy patients, 1.7% of brachytherapy fractions, and 3.4% of patients undergoing MR-guided prostate biopsy. Fifty-one (54%) events were classified as actual incidents, 29 (31%) as near misses, and 14 (15%) as programmatic hazards. Two events were associated with moderate acute medical harm or dosimetric severity, and two were associated with high dosimetric severity. Multi-incident analysis identified five high-risk activities or clinical scenarios as follows: (1) uncommon, low-volume or newly implemented brachytherapy procedures, (2) real-time MR-guided brachytherapy or biopsy procedures, (3) use of in-house devices or software, (4) manual data entry, and (5) patient scheduling and handoffs.

CONCLUSIONS

Brachytherapy is a safe treatment and associated with a low rate of patient safety events. Effective incident management is a key element of continuous quality improvement and patient safety in brachytherapy.

Magnetic resonance imaging basics for the prostate brachytherapist

Magnetic resonance imaging (MRI) is increasingly being used in radiation therapy, and integration of MRI into brachytherapy in particular is becoming more common. We present here a systematic review of the basic physics and technical aspects of incorporating MRI into prostate brachytherapy. Terminology and MRI system components are reviewed along with typical work flows in prostate high-dose-rate and low-dose-rate brachytherapy. In general, the brachytherapy workflow consists of five key components: diagnosis, implantation, treatment planning (scan + plan), implant verification, and delivery. MRI integration is discussed for diagnosis; treatment planning; and MRI-guided brachytherapy implants, in which MRI is used to guide the physical insertion of the brachytherapy applicator or needles. Considerations and challenges for establishing an MRI brachytherapy program are also discussed.

Guidelines by the AAPM and GEC-ESTRO on the use of innovative brachytherapy devices and applications: Report of Task Group 167

Although a multicenter, Phase III, prospective, randomized trial is the gold standard for evidence-based medicine, it is rarely used in the evaluation of innovative devices because of many practical and ethical reasons. It is usually sufficient to compare the dose distributions and dose rates for determining the equivalence of the innovative treatment modality to an existing one. Thus, quantitative evaluation of the dosimetric characteristics of innovative radiotherapy devices or applications is a critical part in which physicists should be actively involved. The physicist's role, along with physician colleagues, in this process is highlighted for innovative brachytherapy devices and applications and includes evaluation of (1) dosimetric considerations for clinical implementation (including calibrations, dose calculations, and radiobiological aspects) to comply with existing societal dosimetric prerequisites for sources in routine clinical use, (2) risks and benefits from a regulatory and safety perspective, and (3) resource assessment and preparedness. Further, it is suggested that any developed calibration methods be traceable to a primary standards dosimetry laboratory (PSDL) such as the National Institute of Standards and Technology in the U.S. or to other PSDLs located elsewhere such as in Europe. Clinical users should follow standards as approved by their country's regulatory agencies that approved such a brachytherapy device. Integration of this system into the medical source calibration infrastructure of secondary standard dosimetry laboratories such as the Accredited Dosimetry Calibration Laboratories in the U.S. is encouraged before a source is introduced into widespread routine clinical use. The American Association of Physicists in Medicine and the Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology (GEC-ESTRO) have developed guidelines for the safe and consistent application of brachytherapy using innovative devices and applications. The current report covers regulatory approvals, calibration, dose calculations, radiobiological issues, and overall safety concerns that should be addressed during the commissioning stage preceding clinical use. These guidelines are based on review of requirements of the U.S. Nuclear Regulatory Commission, U.S. Department of Transportation, International Electrotechnical Commission Medical Electrical Equipment Standard 60601, U.S. Food and Drug Administration, European Commission for CE Marking (Conformité Européenne), and institutional review boards and radiation safety committees.

Towards human-controlled, real-time shape sensing based flexible needle steering for MRI-guided percutaneous therapies

BACKGROUND

Accurate needle placement into soft tissue is essential to percutaneous prostate cancer diagnosis and treatment procedures.

METHODS

This paper discusses the steering of a 20 gauge (G) FBG-integrated needle with three sets of Fiber Bragg Grating (FBG) sensors. A fourth-order polynomial shape reconstruction method is introduced and compared with previous approaches. To control the needle, a bicycle model based navigation method is developed to provide visual guidance lines for clinicians. A real-time model updating method is proposed for needle steering inside inhomogeneous tissue. A series of experiments were performed to evaluate the proposed needle shape reconstruction, visual guidance and real-time model updating methods.

RESULTS

Targeting experiments were performed in soft plastic phantoms and in vitro tissues with insertion depths ranging between 90 and 120 mm. Average targeting errors calculated based upon the acquired camera images were 0.40 ± 0.35 mm in homogeneous plastic phantoms, 0.61 ± 0.45 mm in multilayer plastic phantoms and 0.69 ± 0.25 mm in ex vivo tissue.

CONCLUSIONS

Results endorse the feasibility and accuracy of the needle shape reconstruction and visual guidance methods developed in this work. The approach implemented for the multilayer phantom study could facilitate accurate needle placement efforts in real inhomogeneous tissues. Copyright © 2016 John Wiley & Sons, Ltd.

Adaptive planning strategy for high dose rate prostate brachytherapy—a simulation study on needle positioning errors

The development of magnetic resonance (MR) guided high dose rate (HDR) brachytherapy for prostate cancer has gained increasing interest for delivering a high tumor dose safely in a single fraction. To support needle placement in the limited workspace inside the closed-bore MRI, a single-needle MR-compatible robot is currently under development at the University Medical Center Utrecht (UMCU). This robotic device taps the needle in a divergent way from a single rotation point into the prostate. With this setup, it is warranted to deliver the irradiation dose by successive insertions of the needle. Although robot-assisted needle placement is expected to be more accurate than manual template-guided insertion, needle positioning errors may occur and are likely to modify the pre-planned dose distribution.In this paper, we propose a dose plan adaptation strategy for HDR prostate brachytherapy with feedback on the needle position: a dose plan is made at the beginning of the interventional procedure and updated after each needle insertion in order to compensate for possible needle positioning errors. The introduced procedure can be used with the single needle MR-compatible robot developed at the UMCU. The proposed feedback strategy was tested by simulating complete HDR procedures with and without feedback on eight patients with different numbers of needle insertions (varying from 4 to 12). In of the cases tested, the number of clinically acceptable plans obtained at the end of the procedure was larger with feedback compared to the situation without feedback. Furthermore, the computation time of the feedback between each insertion was below 100 s which makes it eligible for intra-operative use.

Brachytherapy next generation: robotic systems

In a field dominated by external beam radiation therapy (EBRT), both the therapeutic and technical possibilities of brachytherapy (BT) are underrated, shadowed by protons and intensity modulated radiotherapy. Decreasing expertise and indications, as well as increasing lack of specific BT training for radiation therapy (RT) residents led to the real need of shortening its learning curve and making it more popular. Developing robotic BT devices can be a way to mitigate the above issues. There are many teams working at custom-made robotic BT platforms to perfect and overcome the limitations of the existing systems. This paper provides a picture of the current state-of-the-art in robotic assisted BT, as it also conveys the author's solution to the problem, a parallel robot that uses CT-guidance.