Publications by authors named "Nobuhiko Hata"

88 Publications

Rapid Quality Assessment of Nonrigid Image Registration Based on Supervised Learning.

J Digit Imaging 2021 Oct 13. Epub 2021 Oct 13.

Institute for Advanced Computer Studies, University of Maryland, College Park, MD, USA.

When preprocedural images are overlaid on intraprocedural images, interventional procedures benefit in that more structures are revealed in intraprocedural imaging. However, image artifacts, respiratory motion, and challenging scenarios could limit the accuracy of multimodality image registration necessary before image overlay. Ensuring the accuracy of registration during interventional procedures is therefore critically important. The goal of this study was to develop a novel framework that has the ability to assess the quality (i.e., accuracy) of nonrigid multimodality image registration accurately in near real time. We constructed a solution using registration quality metrics that can be computed rapidly and combined to form a single binary assessment of image registration quality as either successful or poor. Based on expert-generated quality metrics as ground truth, we used a supervised learning method to train and test this system on existing clinical data. Using the trained quality classifier, the proposed framework identified successful image registration cases with an accuracy of 81.5%. The current implementation produced the classification result in 5.5 s, fast enough for typical interventional radiology procedures. Using supervised learning, we have shown that the described framework could enable a clinician to obtain confirmation or caution of registration results during clinical procedures.
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http://dx.doi.org/10.1007/s10278-021-00523-5DOI Listing
October 2021

Visually Navigated Bronchoscopy using three cycle-Consistent generative adversarial network for depth estimation.

Med Image Anal 2021 10 18;73:102164. Epub 2021 Jul 18.

National Center for Image-guided Therapy, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, United States.

[Background] Electromagnetically Navigated Bronchoscopy (ENB) is currently the state-of-the art diagnostic and interventional bronchoscopy. CT-to-body divergence is a critical hurdle in ENB, causing navigation error and ultimately limiting the clinical efficacy of diagnosis and treatment. In this study, Visually Navigated Bronchoscopy (VNB) is proposed to address the aforementioned issue of CT-to-body divergence. [Materials and Methods] We extended and validated an unsupervised learning method to generate a depth map directly from bronchoscopic images using a Three Cycle-Consistent Generative Adversarial Network (3cGAN) and registering the depth map to preprocedural CTs. We tested the working hypothesis that the proposed VNB can be integrated to the navigated bronchoscopic system based on 3D Slicer, and accurately register bronchoscopic images to pre-procedural CTs to navigate transbronchial biopsies. The quantitative metrics to asses the hypothesis we set was Absolute Tracking Error (ATE) of the tracking and the Target Registration Error (TRE) of the total navigation system. We validated our method on phantoms produced from the pre-procedural CTs of five patients who underwent ENB and on two ex-vivo pig lung specimens. [Results] The ATE using 3cGAN was 6.2 +/- 2.9 [mm]. The ATE of 3cGAN was statistically significantly lower than that of cGAN, particularly in the trachea and lobar bronchus (p < 0.001). The TRE of the proposed method had a range of 11.7 to 40.5 [mm]. The TRE computed by 3cGAN was statistically significantly smaller than those computed by cGAN in two of the five cases enrolled (p < 0.05). [Conclusion] VNB, using 3cGAN to generate the depth maps was technically and clinically feasible. While the accuracy of tracking by cGAN was acceptable, the TRE warrants further investigation and improvement.
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http://dx.doi.org/10.1016/j.media.2021.102164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8453111PMC
October 2021

The translational and regulatory development of an implantable microdevice for multiple drug sensitivity measurements in cancer patients.

IEEE Trans Biomed Eng 2021 Jul 9;PP. Epub 2021 Jul 9.

Objective: The purpose of this article is to report the translational process of an implantable microdevice platform with an emphasis on the technical and engineering adaptations for patient use, regulatory advances, and successful integration into clinical workflow.

Methods: We developed design adaptations for implantation and retrieval, established ongoing monitoring and testing, and facilitated regulatory advances that enabled the administration and examination of a large set of cancer therapies simultaneously in individual patients.

Results: Six applications for oncology studies have successfully proceeded to patient trials, with future applications in progress.

Conclusion: First-in-human translation required engineering design changes to enable implantation and retrieval that fit with existing clinical workflows, a regulatory strategy that enabled both delivery and response measurement of up to 20 agents in a single patient, and establishment of novel testing and quality control processes for a drug/device combination product without clear precedents.

Significance: This manuscript provides a real-world account and roadmap on how to advance from animal proof-of-concept into the clinic, confronting the question of how to use research to benefit patients.
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http://dx.doi.org/10.1109/TBME.2021.3096126DOI Listing
July 2021

Technical validation of multi-section robotic bronchoscope with first person view control for transbronchial biopsies of peripheral lung.

IEEE Trans Biomed Eng 2021 May 4;PP. Epub 2021 May 4.

This study aims to validate the advantage of the new engineering method to maneuver multi-section robotic bronchoscope with first person view control in transbronchial biopsy. Six physician operators were recruited and tasked to operate a manual and a robotic bronchoscope to the peripheral area placed in patient-derived lung phantoms. The metrics collected were the furthest generation count of the airway the bronchoscope reached, force incurred to the phantoms, and NASA-Task Load Index. The furthest generation count of the airway the physicians reached using the manual and the robotic bronchoscopes were 6.6 +/- 1.2th and 6.7 +/- 0.8th. Robotic bronchoscopes successfully reached the 5th generation count into the peripheral area of the airway, while the manual bronchoscope typically failed earlier in the 3rd generation. More force was incurred to the airway when the manual bronchoscope was used (0.24 +/- 0.20 [N]) than the robotic bronchoscope was applied (0.18 +/- 0.22 [N], p<0.05). The manual bronchoscope imposed more physical demand than the robotic bronchoscope by NASA-TLX score (55 +/- 24 vs 19 +/- 16, p<0.05). These results indicate that a robotic bronchoscope facilitates the advancement of the bronchoscope to the peripheral area with less physical demand to physician operators. The metrics collected in this study would expect to be used as a benchmark for the future development of robotic bronchoscopes.
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http://dx.doi.org/10.1109/TBME.2021.3077356DOI Listing
May 2021

Ring-arrayed Forward-viewing Ultrasound Imaging System: A Feasibility Study.

Proc SPIE Int Soc Opt Eng 2020 Feb 16;11319. Epub 2020 Mar 16.

Dept. of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA, USA.

Current standard workflows of ultrasound (US)-guided needle insertion require physicians to use their both hands: holding the US probe to locate interested areas with the non-dominant hand and the needle with the dominant hand. This is due to the separation of functionalities for localization and needle insertion. This requirement does not only make the procedure cumbersome, but also limits the reliability of guidance given that the positional relationship between the needle and US images is unknown and interpreted with their experience and assumption. Although the US-guided needle insertion may be assisted through navigation systems, recovery of the positional relationship between the needle and US images requires the usage of external tracking systems and image-based tracking algorisms that may involve the registration inaccuracy. Therefore, there is an unmet need for the solution that provides a simple and intuitive needle localization and insertion to improve the conventional US-guided procedure. In this work, we propose a new device concept solution based on the ring-arrayed forward-viewing (RAF) ultrasound imaging system. The proposed system is comprised with ring-arrayed transducers and an open whole inside the ring where the needle can be inserted. The ring array provides forward-viewing US images, where the needle path is always maintained at the center of the reconstructed image without requiring any registration. As the proof of concept, we designed single-circle ring-arrayed configurations with different radiuses and visualized point targets using the forward-viewing US imaging through simulations and phantom experiments. The results demonstrated the successful target visualization and indicates the ring-arrayed US imaging has a potential to improve the US-guided needle insertion procedure to be simpler and more intuitive.
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http://dx.doi.org/10.1117/12.2550042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7416557PMC
February 2020

Simulated accuracy assessment of small footprint body-mounted probe alignment device for MRI-guided cryotherapy of abdominal lesions.

Med Phys 2020 Jun 28;47(6):2337-2349. Epub 2020 Mar 28.

Radiology, Brigham and Women's Hospital, Boston, MA, 02115, USA.

Purpose: Magnetic resonance imaging (MRI)-guided percutaneous cryotherapy of abdominal lesions, an established procedure, uses MRI to guide and monitor the cryoablation of lesions. Methods to precisely guide cryotherapy probes with a minimum amount of trial-and-error are yet to be established. To aid physicians in attaining precise probe alignment without trial-and-error, a body-mounted motorized cryotherapy-probe alignment device (BMCPAD) with motion compensation was clinically tested in this study. The study also compared the contribution of body motion and organ motion compensation to the guidance accuracy of a body-mounted probe alignment device.

Methods: The accuracy of guidance using the BMCPAD was prospectively measured during MRI-guided percutaneous cryotherapies before insertion of the probes. Clinical parameters including patient age, types of anesthesia, depths of the target, and organ sites of target were collected. By using MR images of the target organs and fiducial markers embedded in the BMCPAD, we retrospectively simulated the guidance accuracy with body motion compensation, organ motion compensation, and no compensation. The collected data were analyzed to test the impact of motion compensation on the guidance accuracy.

Results: Thirty-seven physical guidance of probes were prospectively recorded for sixteen completed cases. The accuracy of physical guidance using the BMCPAD was 13.4 ± 11.1 mm. The simulated accuracy of guidance with body motion compensation, organ motion compensation, and no compensation was 2.4 ± 2.9 mm, 2.2 ± 1.6 mm, and 3.5 ± 2.9 mm, respectively. Data analysis revealed that the body motion compensation and organ motion compensation individually impacted the improvement in the accuracy of simulated guidance. Moreover, the difference in the accuracy of guidance either by body motion compensation or organ motion compensation was not statistically significant. The major clinical parameters impacting the accuracy of guidance were the body and organ motions. Patient age, types of anesthesia, depths of the target, and organ sites of target did not influence the accuracy of guidance using BMCPAD. The magnitude of body surface movement and organ movement exhibited mutual statistical correlation.

Conclusions: The BMCPAD demonstrated guidance accuracy comparable to that of previously reported devices for CT-guided procedures. The analysis using simulated motion compensation revealed that body motion compensation and organ motion compensation individually impact the improvement in the accuracy of device-guided cryotherapy probe alignment. Considering the correlation between body and organ movements, we also determined that body motion compensation using the ring fiducial markers in the BMCPAD can be solely used to address both body and organ motions in MRI-guided cryotherapy.
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http://dx.doi.org/10.1002/mp.14116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7889307PMC
June 2020

System Integration and Preliminary Clinical Evaluation of a Robotic System for MRI-Guided Transperineal Prostate Biopsy.

J Med Robot Res 2019 Jun 15;4(2). Epub 2018 May 15.

Automation and Interventional Medicine Laboratory, Worcester Polytechnic Institute, Worcester, MA 01609, USA [napatel,

This paper presents the development, preclinical evaluation, and preliminary clinical study of a robotic system for targeted transperineal prostate biopsy under direct interventional magnetic resonance imaging (MRI) guidance. The clinically integrated robotic system is developed based on a modular design approach, comprised of surgical navigation application, robot control software, MRI robot controller hardware, and robotic needle placement manipulator. The system provides enabling technologies for MRI-guided procedures. It can be easily transported and setup for supporting the clinical workflow of interventional procedures, and the system is readily extensible and reconfigurable to other clinical applications. Preclinical evaluation of the system is performed with phantom studies in a 3 Tesla MRI scanner, rehearsing the proposed clinical workflow, and demonstrating an in-plane targeting error of 1.5mm. The robotic system has been approved by the institutional review board (IRB) for clinical trials. A preliminary clinical study is conducted with the patient consent, demonstrating the targeting errors at two biopsy target sites to be 4.0 and 3.7, which is sufficient to target a clinically significant tumor foci. First-in-human trials to evaluate the system's effectiveness and accuracy for MR image-guide prostate biopsy are underway.
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http://dx.doi.org/10.1142/S2424905X19500016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6726403PMC
June 2019

Transbronchial biopsy catheter enhanced by a multisection continuum robot with follow-the-leader motion.

Int J Comput Assist Radiol Surg 2019 Nov 9;14(11):2021-2029. Epub 2019 Jul 9.

National Center for Image Guided Therapy, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA, 02115, USA.

Purpose: Current manual catheters for transbronchial biopsy in the lung lack a steering ability, which hampers a physician's ability to reach nodules in the peripheral lung. The objective of this paper is to design and build a multisection robot with a follow-the-leader motion and compare the performance of the conventional catheter and our robotic catheter in the right main and right segmental lobar bronchus.

Methods: A three-section continuum robot with an outer diameter of 3 mm was developed. Each section includes one anchored wire and two driving wires made of stainless steel. Follow-the-leader control is implemented using a joystick for a physician to control the distal section of the robot, while the subsequent two sections follow the controlled distal section.

Results: The robotic catheter deviated from the preplanned approach path by less than the manual catheter did (robotic: [Formula: see text] mm and manual: [Formula: see text] mm), with [Formula: see text]. The average force applied to the wall, producing potential trauma to the wall, was less for the robotic catheter ([Formula: see text] N) than for the manual catheter ([Formula: see text] N), [Formula: see text].

Conclusion: This study demonstrated an improvement in the maneuverability for the robotic catheter. In addition to a greater aptitude for reaching a peripheral area of the lung, these findings suggest that the designated target in a peripheral area can be reached with less trauma to the bronchi wall.
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http://dx.doi.org/10.1007/s11548-019-02017-wDOI Listing
November 2019

Continuum Robot With Follow-the-Leader Motion for Endoscopic Third Ventriculostomy and Tumor Biopsy.

IEEE Trans Biomed Eng 2020 02 29;67(2):379-390. Epub 2019 Apr 29.

Background: In a combined endoscopic third ventriculostomy (ETV) and endoscopic tumor biopsy (ETB) procedure, an optimal tool trajectory is mandatory to minimize trauma to surrounding cerebral tissue.

Objective: This paper presents wire-driven multi-section robot with push-pull wire. The robot is tested to attain follow-the-leader (FTL) motion to place surgical instruments through narrow passages while minimizing the trauma to tissues.

Methods: A wire-driven continuum robot with six sub-sections was developed and its kinematic model was proposed to achieve FTL motion. An accuracy test to assess the robot's ability to attain FTL motion along a set of elementary curved trajectory was performed. We also used hydrocephalus ventricular model created from human subject data to generate five ETV/ETB trajectories and conducted a study assessing the accuracy of the FTL motion along these clinically desirable trajectories.

Results: In the test with elementary curved paths, the maximal deviation of the robot was increased from 0.47 mm at 30 turn to 1.78 mm at 180 in a simple C-shaped curve. S-shaped FTL motion had lesser deviation ranging from 0.16 to 0.18 mm. In the phantom study, the greatest tip deviation was 1.45 mm, and the greatest path deviation was 1.23 mm.

Conclusion: We present the application of a continuum robot with FTL motion to perform a combined ETV/ETB procedure. The validation study using human subject data indicated that the accuracy of FTL motion is relatively high. The study indicated that FTL motion may be useful tool for combined ETV and ETB.
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http://dx.doi.org/10.1109/TBME.2019.2913752DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7098325PMC
February 2020

Evaluation of robot-assisted MRI-guided prostate biopsy: needle path analysis during clinical trials.

Phys Med Biol 2018 10 16;63(20):20NT02. Epub 2018 Oct 16.

Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States of America. Author to whom correspondence should be addressed.

While the interaction between a needle and the surrounding tissue is known to cause a significant targeting error in prostate biopsy leading to false-negative results, few studies have demonstrated how it impacts in the actual procedure. We performed a pilot study on robot-assisted MRI-guided prostate biopsy with an emphasis on the in-depth analysis of the needle-tissue interaction in vivo. The data were acquired during in-bore transperineal prostate biopsies in patients using a 4 degrees-of-freedom (DoF) MRI-compatible robot. The anatomical structures in the pelvic area and the needle path were reconstructed from MR images, and quantitatively analyzed. We analyzed each structure individually and also proposed a mathematical model to investigate the influence of those structures in the targeting error using the mixed-model regression. The median targeting error in 188 insertions (27 patients) was 6.3 mm. Both the individual anatomical structure analysis and the mixed-model analysis showed that the deviation resulted from the contact between the needle and the skin as the main source of error. On contrary, needle bending inside the tissue (expressed as needle curvature) did not vary among insertions with targeting errors above and below the average. The analysis indicated that insertions crossing the bulbospongiosus presented a targeting error lower than the average. The mixed-model analysis demonstrated that the distance between the needle guide and the patient skin, the deviation at the entry point, and the path length inside the pelvic diaphragm had a statistically significant contribution to the targeting error (p  <  0.05). Our results indicate that the errors associated with the elastic contact between the needle and the skin were more prominent than the needle bending along the insertion. Our findings will help to improve the preoperative planning of transperineal prostate biopsies.
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http://dx.doi.org/10.1088/1361-6560/aae214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6198326PMC
October 2018

Closed-Loop Active Compensation for Needle Deflection and Target Shift During Cooperatively Controlled Robotic Needle Insertion.

Ann Biomed Eng 2018 Oct 20;46(10):1582-1594. Epub 2018 Jun 20.

Robotics Engineering, Worcester Polytechnic Institute, 85 Prescott St., Worcester, MA, 10605, USA.

Intra-operative imaging is sometimes available to assist needle biopsy, but typical open-loop insertion does not account for unmodeled needle deflection or target shift. Closed-loop image-guided compensation for deviation from an initial straight-line trajectory through rotational control of an asymmetric tip can reduce targeting error. Incorporating robotic closed-loop control often reduces physician interaction with the patient, but by pairing closed-loop trajectory compensation with hands-on cooperatively controlled insertion, a physician's control of the procedure can be maintained while incorporating benefits of robotic accuracy. A series of needle insertions were performed with a typical 18G needle using closed-loop active compensation under both fully autonomous and user-directed cooperative control. We demonstrated equivalent improvement in accuracy while maintaining physician-in-the-loop control with no statistically significant difference (p > 0.05) in the targeting accuracy between any pair of autonomous or individual cooperative sets, with average targeting accuracy of 3.56 mm. With cooperatively controlled insertions and target shift between 1 and 10 mm introduced upon needle contact, the system was able to effectively compensate up to the point where error approached a maximum curvature governed by bending mechanics. These results show closed-loop active compensation can enhance targeting accuracy, and that the improvement can be maintained under user directed cooperative insertion.
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http://dx.doi.org/10.1007/s10439-018-2070-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6319385PMC
October 2018

Motion compensation for MRI-compatible patient-mounted needle guide device: estimation of targeting accuracy in MRI-guided kidney cryoablations.

Phys Med Biol 2018 04 13;63(8):085010. Epub 2018 Apr 13.

Department of Radiology, Brigham and Womens Hospital and Harvard Medical School, Boston, MA 02115, United States of America.

Patient-mounted needle guide devices for percutaneous ablation are vulnerable to patient motion. The objective of this study is to develop and evaluate a software system for an MRI-compatible patient-mounted needle guide device that can adaptively compensate for displacement of the device due to patient motion using a novel image-based automatic device-to-image registration technique. We have developed a software system for an MRI-compatible patient-mounted needle guide device for percutaneous ablation. It features fully-automated image-based device-to-image registration to track the device position, and a device controller to adjust the needle trajectory to compensate for the displacement of the device. We performed: (a) a phantom study using a clinical MR scanner to evaluate registration performance; (b) simulations using intraoperative time-series MR data acquired in 20 clinical cases of MRI-guided renal cryoablations to assess its impact on motion compensation; and (c) a pilot clinical study in three patients to test its feasibility during the clinical procedure. FRE, TRE, and success rate of device-to-image registration were 2.71 ± 2.29 mm, 1.74 ± 1.13 mm, and 98.3% for the phantom images. The simulation study showed that the motion compensation reduced the targeting error for needle placement from 8.2 mm to 5.4 mm (p  <  0.0005) in patients under general anesthesia (GA), and from 14.4 mm to 10.0 mm (p < 1.0 × 10(−5)) in patients under monitored anesthesia care (MAC). The pilot study showed that the software registered the device successfully in a clinical setting. Our simulation study demonstrated that the software system could significantly improve targeting accuracy in patients treated under both MAC and GA. Intraprocedural image-based device-to-image registration was feasible.
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http://dx.doi.org/10.1088/1361-6560/aab736DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5899055PMC
April 2018

Robotics in MRI-Guided Interventions.

Top Magn Reson Imaging 2018 Feb;27(1):19-23

Department of Radiology, National Center for Image Guided Therapy, Brigham and Women's Hospital, Boston, MA.

Robots have been found to be a useful tool in magnetic resonance imaging (MRI)-guided intervention. The utility of robots in MRI-guided therapy ranges from aid for precision targeting to high-dexterity surgical tools to improve or even enable new MRI-guided therapy options. The objective of this article is to review the technical aspects of robotics in MRI-guided interventions, highlight the role of MRI robots in prostate interventions, and finally discuss the future contribution of emerging robotics technology useful in MRI-guided intervention.
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http://dx.doi.org/10.1097/RMR.0000000000000159DOI Listing
February 2018

Using needle orientation sensing as surrogate signal for respiratory motion estimation in percutaneous interventions.

Int J Comput Assist Radiol Surg 2018 Jan 1;13(1):125-133. Epub 2017 Aug 1.

Department of Radiology, Brigham and Womens Hospital and Harvard Medical School, Boston, MA, USA.

Purpose: To develop and evaluate an approach to estimate the respiratory-induced motion of lesions in the chest and abdomen.

Materials And Methods: The proposed approach uses the motion of an initial reference needle inserted into a moving organ to estimate the lesion (target) displacement that is caused by respiration. The needles position is measured using an inertial measurement unit (IMU) sensor externally attached to the hub of an initially placed reference needle. Data obtained from the IMU sensor and the target motion are used to train a learning-based approach to estimate the position of the moving target. An experimental platform was designed to mimic respiratory motion of the liver. Liver motion profiles of human subjects provided inputs to the experimental platform. Variables including the insertion angle, target depth, target motion velocity and target proximity to the reference needle were evaluated by measuring the error of the estimated target position and processing time.

Results: The mean error of estimation of the target position ranged between 0.86 and 1.29 mm. The processing maximum training and testing time was 5 ms which is suitable for real-time target motion estimation using the needle position sensor.

Conclusion: The external motion of an initially placed reference needle inserted into a moving organ can be used as a surrogate, measurable and accessible signal to estimate in real-time the position of a moving target caused by respiration; this technique could then be used to guide the placement of subsequently inserted needles directly into the target.
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http://dx.doi.org/10.1007/s11548-017-1644-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5754381PMC
January 2018

Fiber Optic Force Sensors for MRI-Guided Interventions and Rehabilitation: A Review.

IEEE Sens J 2017 Apr 17;17(7):1952-1963. Epub 2017 Jan 17.

Automation and Interventional Medicine (AIM) Robotics Laboratory, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA.

Magnetic Resonance Imaging (MRI) provides both anatomical imaging with excellent soft tissue contrast and functional MRI imaging (fMRI) of physiological parameters. The last two decades have witnessed the manifestation of increased interest in MRI-guided minimally invasive intervention procedures and fMRI for rehabilitation and neuroscience research. Accompanying the aspiration to utilize MRI to provide imaging feedback during interventions and brain activity for neuroscience study, there is an accumulated effort to utilize force sensors compatible with the MRI environment to meet the growing demand of these procedures, with the goal of enhanced interventional safety and accuracy, improved efficacy and rehabilitation outcome. This paper summarizes the fundamental principles, the state of the art development and challenges of fiber optic force sensors for MRI-guided interventions and rehabilitation. It provides an overview of MRI-compatible fiber optic force sensors based on different sensing principles, including light intensity modulation, wavelength modulation, and phase modulation. Extensive design prototypes are reviewed to illustrate the detailed implementation of these principles. Advantages and disadvantages of the sensor designs are compared and analyzed. A perspective on the future development of fiber optic sensors is also presented which may have additional broad clinical applications. Future surgical interventions or rehabilitation will rely on intelligent force sensors to provide situational awareness to augment or complement human perception in these procedures.
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http://dx.doi.org/10.1109/JSEN.2017.2654489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482288PMC
April 2017

Medical robotics-Regulatory, ethical, and legal considerations for increasing levels of autonomy.

Sci Robot 2017 Mar 15;2(4). Epub 2017 Mar 15.

Russell H. Taylor is Director of the the Laboratory for Computational Sensing and Robotics and of the Engineering Research Center for Computer-Integrated Surgical Systems and Technology, Department of Computer Science, Johns Hopkins University, Baltimore, MD 21218, USA.

The regulatory, ethical, and legal barriers imposed on medical robots necessitate careful consideration of different levels of autonomy, as well as the context for use.
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http://dx.doi.org/10.1126/scirobotics.aam8638DOI Listing
March 2017

Increasing the impact of medical image computing using community-based open-access hackathons: The NA-MIC and 3D Slicer experience.

Med Image Anal 2016 10 7;33:176-180. Epub 2016 Jul 7.

Brigham and Women's Hospital and Harvard Medical School.

The National Alliance for Medical Image Computing (NA-MIC) was launched in 2004 with the goal of investigating and developing an open source software infrastructure for the extraction of information and knowledge from medical images using computational methods. Several leading research and engineering groups participated in this effort that was funded by the US National Institutes of Health through a variety of infrastructure grants. This effort transformed 3D Slicer from an internal, Boston-based, academic research software application into a professionally maintained, robust, open source platform with an international leadership and developer and user communities. Critical improvements to the widely used underlying open source libraries and tools-VTK, ITK, CMake, CDash, DCMTK-were an additional consequence of this effort. This project has contributed to close to a thousand peer-reviewed publications and a growing portfolio of US and international funded efforts expanding the use of these tools in new medical computing applications every year. In this editorial, we discuss what we believe are gaps in the way medical image computing is pursued today; how a well-executed research platform can enable discovery, innovation and reproducible science ("Open Science"); and how our quest to build such a software platform has evolved into a productive and rewarding social engineering exercise in building an open-access community with a shared vision.
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http://dx.doi.org/10.1016/j.media.2016.06.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5003088PMC
October 2016

Three-dimensional quantitative assessment of ablation margins based on registration of pre- and post-procedural MRI and distance map.

Int J Comput Assist Radiol Surg 2016 Jun 2;11(6):1133-42. Epub 2016 Apr 2.

Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA, 02115, USA.

Purpose: Contrast-enhanced MR images are widely used to confirm the adequacy of ablation margin after liver ablation for early prediction of local recurrence. However, quantitative assessment of the ablation margin by comparing pre- and post-procedural images remains challenging. We developed and tested a novel method for three-dimensional quantitative assessment of ablation margin based on non-rigid image registration and 3D distance map.

Methods: Our method was tested with pre- and post-procedural MR images acquired in 21 patients who underwent image-guided percutaneous liver ablation. The two images were co-registered using non-rigid intensity-based registration. After the tumor and ablation volumes were segmented, target volume coverage, percent of tumor coverage, and Dice similarity coefficient were calculated as metrics representing overall adequacy of ablation. In addition, 3D distance map around the tumor was computed and superimposed on the ablation volume to identify the area with insufficient margins. For patients with local recurrences, the follow-up images were registered to the post-procedural image. Three-dimensional minimum distance between the recurrence and the areas with insufficient margins was quantified.

Results: The percent tumor coverage for all nonrecurrent cases was 100 %. Five cases had tumor recurrences, and the 3D distance map revealed insufficient tumor coverage or a 0-mm margin. It also showed that two recurrences were remote to the insufficient margin.

Conclusions: Non-rigid registration and 3D distance map allow us to quantitatively evaluate the adequacy of the ablation margin after percutaneous liver ablation. The method may be useful to predict local recurrences immediately following ablation procedure.
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http://dx.doi.org/10.1007/s11548-016-1398-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4893989PMC
June 2016

Body-mounted robotic instrument guide for image-guided cryotherapy of renal cancer.

Med Phys 2016 Feb;43(2):843-53

National Center for Image Guided Therapy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.

Purpose: Image-guided cryotherapy of renal cancer is an emerging alternative to surgical nephrectomy, particularly for those who cannot sustain the physical burden of surgery. It is well known that the outcome of this therapy depends on the accurate placement of the cryotherapy probe. Therefore, a robotic instrument guide may help physicians aim the cryotherapy probe precisely to maximize the efficacy of the treatment and avoid damage to critical surrounding structures. The objective of this paper was to propose a robotic instrument guide for orienting cryotherapy probes in image-guided cryotherapy of renal cancers. The authors propose a body-mounted robotic guide that is expected to be less susceptible to guidance errors caused by the patient's whole body motion.

Methods: Keeping the device's minimal footprint in mind, the authors developed and validated a body-mounted, robotic instrument guide that can maintain the geometrical relationship between the device and the patient's body, even in the presence of the patient's frequent body motions. The guide can orient the cryotherapy probe with the skin incision point as the remote-center-of-motion. The authors' validation studies included an evaluation of the mechanical accuracy and position repeatability of the robotic instrument guide. The authors also performed a mock MRI-guided cryotherapy procedure with a phantom to compare the advantage of robotically assisted probe replacements over a free-hand approach, by introducing organ motions to investigate their effects on the accurate placement of the cryotherapy probe. Measurements collected for performance analysis included accuracy and time taken for probe placements. Multivariate analysis was performed to assess if either or both organ motion and the robotic guide impacted these measurements.

Results: The mechanical accuracy and position repeatability of the probe placement using the robotic instrument guide were 0.3 and 0.1 mm, respectively, at a depth of 80 mm. The phantom test indicated that the accuracy of probe placement was significantly better with the robotic instrument guide (4.1 mm) than without the guide (6.3 mm, p<0.001), even in the presence of body motion. When independent organ motion was artificially added, in addition to body motion, the advantage of accurate probe placement using the robotic instrument guide disappeared statistically [i.e., 6.0 mm with the robotic guide and 5.9 mm without the robotic guide (p = 0.906)]. When the robotic instrument guide was used, the total time required to complete the procedure was reduced from 19.6 to 12.7 min (p<0.001). Multivariable analysis indicated that the robotic instrument guide, not the organ motion, was the cause of statistical significance. The statistical power the authors obtained was 88% in accuracy assessment and 99% higher in duration measurement.

Conclusions: The body-mounted robotic instrument guide allows positioning of the probe during image-guided cryotherapy of renal cancer and was done in fewer attempts and in less time than the free-hand approach. The accuracy of the placement of the cryotherapy probe was better using the robotic instrument guide than without the guide when no organ motion was present. The accuracy between the robotic and free-hand approach becomes comparable when organ motion was present.
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http://dx.doi.org/10.1118/1.4939875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4723400PMC
February 2016

Tendon-driven continuum robot for neuroendoscopy: validation of extended kinematic mapping for hysteresis operation.

Int J Comput Assist Radiol Surg 2016 Apr 17;11(4):589-602. Epub 2015 Oct 17.

National Center for Image Guided Therapy, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.

Purpose: The hysteresis operation is an outstanding issue in tendon-driven actuation--which is used in robot-assisted surgery--as it is incompatible with kinematic mapping for control and trajectory planning. Here, a new tendon-driven continuum robot, designed to fit existing neuroendoscopes, is presented with kinematic mapping for hysteresis operation.

Methods: With attention to tension in tendons as a salient factor of the hysteresis operation, extended forward kinematic mapping (FKM) has been developed. In the experiment, the significance of every component in the robot for the hysteresis operation has been investigated. Moreover, the prediction accuracy of postures by the extended FKM has been determined experimentally and compared with piecewise constant curvature assumption.

Results: The tendons were the most predominant factor affecting the hysteresis operation of the robot. The extended FKM including friction in tendons predicted the postures in the hysteresis operation with improved accuracy (2.89 and 3.87 mm for the single and the antagonistic-tendons layouts, respectively). The measured accuracy was within the target value of 5 mm for planning of neuroendoscopic resection of intraventricle tumors.

Conclusion: The friction in tendons was the most predominant factor for the hysteresis operation in the robot. The extended FKM including this factor can improve prediction accuracy of the postures in the hysteresis operation. The trajectory of the new robot can be planned within target value for the neuroendoscopic procedure by using the extended FKM.
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http://dx.doi.org/10.1007/s11548-015-1310-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4993112PMC
April 2016

Piezoelectrically Actuated Robotic System for MRI-Guided Prostate Percutaneous Therapy.

IEEE ASME Trans Mechatron 2015 Aug;20(4):1920-1932

Automation and Interventional Medicine (AIM) Robotics Lab, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA ( ).

This paper presents a fully-actuated robotic system for percutaneous prostate therapy under continuously acquired live magnetic resonance imaging (MRI) guidance. The system is composed of modular hardware and software to support the surgical workflow of intra-operative MRI-guided surgical procedures. We present the development of a 6-degree-of-freedom (DOF) needle placement robot for transperineal prostate interventions. The robot consists of a 3-DOF needle driver module and a 3-DOF Cartesian motion module. The needle driver provides needle cannula translation and rotation (2-DOF) and stylet translation (1-DOF). A custom robot controller consisting of multiple piezoelectric motor drivers provides precision closed-loop control of piezoelectric motors and enables simultaneous robot motion and MR imaging. The developed modular robot control interface software performs image-based registration, kinematics calculation, and exchanges robot commands and coordinates between the navigation software and the robot controller with a new implementation of the open network communication protocol OpenIGTLink. Comprehensive compatibility of the robot is evaluated inside a 3-Tesla MRI scanner using standard imaging sequences and the signal-to-noise ratio (SNR) loss is limited to 15%. The image deterioration due to the present and motion of robot demonstrates unobservable image interference. Twenty-five targeted needle placements inside gelatin phantoms utilizing an 18-gauge ceramic needle demonstrated 0.87 mm root mean square (RMS) error in 3D Euclidean distance based on MRI volume segmentation of the image-guided robotic needle placement procedure.
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http://dx.doi.org/10.1109/TMECH.2014.2359413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4580290PMC
August 2015

Tendon-Driven Continuum Robot for Endoscopic Surgery: Preclinical Development and Validation of a Tension Propagation Model.

IEEE ASME Trans Mechatron 2015 Oct;20(5):2252-2263

National Center for Image Guided Therapy, Brigham and Women's Hospital and Harvard Medical School, MA, USA ( ).

In this paper, we present a tendon-driven continuum robot for endoscopic surgery. The robot has two sections for articulation actuated by tendon wires. By actuating the two sections independently, the robot can generate a variety of tip positions while maintaining the tip direction. This feature offers more flexibility in positioning the tip for large viewing angles of up to 180 degrees than does a conventional endoscope. To accurately estimate the tip position at large viewing angles, we employed kinematic mapping with a tension propagation model including friction between the tendon wires and the robot body. In a simulation study using this kinematic-mapping, the two-section robot at a target scale (outer diameter 1.7 mm and length 60 mm) produced a variety of tip positions within 50-mm ranges at the 180°-angle view. In the experimental validation, a 10:1 scale prototype performed three salient postures with different tip positions at the 180°-angle view. The proposed forward kinematic mapping (FKM) predicted the tip position within a tip-to-tip error of 6 mm over the 208-mm articulating length. The tip-to-tip error by FKM was significantly less than the one by conventional piecewise-constant-curvature approximation (PCCA) (FKM: 5.9 ± 2.9 mm vs. PCCA: 23.7 ± 3.6 mm, n=15, P < 0.01).
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http://dx.doi.org/10.1109/TMECH.2014.2372635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4569018PMC
October 2015

MICCAI 2014 special issue.

Int J Comput Assist Radiol Surg 2015 Aug;10(8):1179

Department of Radiology, Brigham and Women's Hospital, L1-050, 75 Francis St., Boston, MA, 02115, USA,

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http://dx.doi.org/10.1007/s11548-015-1270-6DOI Listing
August 2015

In-bore prostate transperineal interventions with an MRI-guided parallel manipulator: system development and preliminary evaluation.

Int J Med Robot 2016 Jun 26;12(2):199-213. Epub 2015 Jun 26.

Laboratory for Computational Sensing and Robotics (LCSR) at the Johns Hopkins University, Baltimore, MD, USA.

Background: Robot-assisted minimally-invasive surgery is well recognized as a feasible solution for diagnosis and treatment of prostate cancer in humans.

Methods: This paper discusses the kinematics of a parallel 4 Degrees-of-Freedom (DOF) surgical manipulator designed for minimally invasive in-bore prostate percutaneous interventions through the patient's perineum. The proposed manipulator takes advantage of four sliders actuated by MRI-compatible piezoelectric motors and incremental rotary encoders. Errors, mostly originating from the design and manufacturing process, need to be identified and reduced before the robot is deployed in clinical trials.

Results: The manipulator has undergone several experiments to evaluate the repeatability and accuracy (about 1 mm in air (in x or y direction) at the needle's reference point) of needle placement, which is an essential concern in percutaneous prostate interventions.

Conclusion: The acquired results endorse the sustainability, precision and reliability of the manipulator. Copyright © 2015 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/rcs.1671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4691445PMC
June 2016

Assessment of the OsteoMark-Navigation System for Oral and Maxillofacial Surgery.

J Oral Maxillofac Surg 2015 Oct 19;73(10):2005-16. Epub 2015 Mar 19.

Associate Professor, Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Boston, MA.

Purpose: To assess the accuracy of a novel navigation system for maxillofacial surgery using human cadavers and a live minipig model.

Materials And Methods: We tested an electromagnetic tracking system (OsteoMark-Navigation) that uses simple sensors to determine the position and orientation of a hand-held pencil-like marking device. The device can translate 3-dimensional computed tomographic data intraoperatively to allow the surgeon to localize and draw a proposed osteotomy or the resection margins of a tumor on bone. The accuracy of the OsteoMark-Navigation system in locating and marking osteotomies and screw positions in human cadaver heads was assessed. In group 1 (n = 3, 6 sides), OsteoMark-Navigation marked osteotomies and screw positions were compared to virtual treatment plans. In group 2 (n = 3, 6 sides), marked osteotomies and screw positions for distraction osteogenesis devices were compared with those performed using fabricated guide stents. Three metrics were used to document the precision and accuracy. In group 3 (n = 1), the system was tested in a standard operating room environment.

Results: For group 1, the mean error between the points was 0.7 mm (horizontal) and 1.7 mm (vertical). Compared with the posterior and inferior mandibular border, the mean error was 1.2 and 1.7 mm, respectively. For group 2, the mean discrepancy between the points marked using the OsteoMark-Navigation system and the surgical guides was 1.9 mm (range 0 to 4.1). The system maintained accuracy on a live minipig in a standard operating room environment.

Conclusion: Based on this research OsteoMark-Navigation is a potentially powerful tool for clinical use in maxillofacial surgery. It has accuracy and precision comparable to that of existing clinical applications.
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http://dx.doi.org/10.1016/j.joms.2015.03.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4575615PMC
October 2015

Graphics Processing Unit-Accelerated Nonrigid Registration of MR Images to CT Images During CT-Guided Percutaneous Liver Tumor Ablations.

Acad Radiol 2015 Jun 14;22(6):722-33. Epub 2015 Mar 14.

Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis St, ASB-I L1-050, Boston, MA 02115.

Rationale And Objectives: Accuracy and speed are essential for the intraprocedural nonrigid magnetic resonance (MR) to computed tomography (CT) image registration in the assessment of tumor margins during CT-guided liver tumor ablations. Although both accuracy and speed can be improved by limiting the registration to a region of interest (ROI), manual contouring of the ROI prolongs the registration process substantially. To achieve accurate and fast registration without the use of an ROI, we combined a nonrigid registration technique on the basis of volume subdivision with hardware acceleration using a graphics processing unit (GPU). We compared the registration accuracy and processing time of GPU-accelerated volume subdivision-based nonrigid registration technique to the conventional nonrigid B-spline registration technique.

Materials And Methods: Fourteen image data sets of preprocedural MR and intraprocedural CT images for percutaneous CT-guided liver tumor ablations were obtained. Each set of images was registered using the GPU-accelerated volume subdivision technique and the B-spline technique. Manual contouring of ROI was used only for the B-spline technique. Registration accuracies (Dice similarity coefficient [DSC] and 95% Hausdorff distance [HD]) and total processing time including contouring of ROIs and computation were compared using a paired Student t test.

Results: Accuracies of the GPU-accelerated registrations and B-spline registrations, respectively, were 88.3 ± 3.7% versus 89.3 ± 4.9% (P = .41) for DSC and 13.1 ± 5.2 versus 11.4 ± 6.3 mm (P = .15) for HD. Total processing time of the GPU-accelerated registration and B-spline registration techniques was 88 ± 14 versus 557 ± 116 seconds (P < .000000002), respectively; there was no significant difference in computation time despite the difference in the complexity of the algorithms (P = .71).

Conclusions: The GPU-accelerated volume subdivision technique was as accurate as the B-spline technique and required significantly less processing time. The GPU-accelerated volume subdivision technique may enable the implementation of nonrigid registration into routine clinical practice.
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http://dx.doi.org/10.1016/j.acra.2015.01.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4428967PMC
June 2015

3T MR-guided in-bore transperineal prostate biopsy: A comparison of robotic and manual needle-guidance templates.

J Magn Reson Imaging 2015 Jul 27;42(1):63-71. Epub 2014 Sep 27.

Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA.

Purpose: To demonstrate the utility of a robotic needle-guidance template device as compared to a manual template for in-bore 3T transperineal magnetic resonance imaging (MRI)-guided prostate biopsy.

Materials And Methods: This two-arm mixed retrospective-prospective study included 99 cases of targeted transperineal prostate biopsies. The biopsy needles were aimed at suspicious foci noted on multiparametric 3T MRI using manual template (historical control) as compared with a robotic template. The following data were obtained: the accuracy of average and closest needle placement to the focus, histologic yield, percentage of cancer volume in positive core samples, complication rate, and time to complete the procedure.

Results: In all, 56 cases were performed using the manual template and 43 cases were performed using the robotic template. The mean accuracy of the best needle placement attempt was higher in the robotic group (2.39 mm) than the manual group (3.71 mm, P < 0.027). The mean core procedure time was shorter in the robotic (90.82 min) than the manual group (100.63 min, P < 0.030). Percentage of cancer volume in positive core samples was higher in the robotic group (P < 0.001). Cancer yields and complication rates were not statistically different between the two subgroups (P = 0.557 and P = 0.172, respectively).

Conclusion: The robotic needle-guidance template helps accurate placement of biopsy needles in MRI-guided core biopsy of prostate cancer.
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http://dx.doi.org/10.1002/jmri.24770DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4376663PMC
July 2015
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