Publications

2013
Junichi Tokuda, Sang-Eun Song, Kemal Tuncali, Clare Tempany, and Nobuhiko Hata. 2013. “Configurable automatic detection and registration of fiducial frames for device-to-image registration in MRI-guided prostate interventions.” Med Image Comput Comput Assist Interv, 16, Pt 3, Pp. 355-62.Abstract
We propose a novel automatic fiducial frame detection and registration method for device-to-image registration in MRI-guided prostate interventions. The proposed method does not require any manual selection of markers, and can be applied to a variety of fiducial frames, which consist of multiple cylindrical MR-visible markers placed in different orientations. The key idea is that automatic extraction of linear features using a line filter is more robust than that of bright spots by thresholding; by applying a line set registration algorithm to the detected markers, the frame can be registered to the MRI. The method was capable of registering the fiducial frame to the MRI with an accuracy of 1.00 +/- 0.73 mm and 1.41 +/- 1.06 degrees in a phantom study, and was sufficiently robust to detect the fiducial frame in 98% of images acquired in clinical cases despite the existence of anatomical structures in the field of view.
Sang-Eun Song, Junichi Tokuda, Kemal Tuncali, Clare M Tempany, Elizabeth Zhang, and Nobuhiko Hata. 2013. “Development and preliminary evaluation of a motorized needle guide template for MRI-guided targeted prostate biopsy.” IEEE Trans Biomed Eng, 60, 11, Pp. 3019-27.Abstract
To overcome the problems of limited needle insertion accuracy and human error in the use of a conventional needle guide template in magnetic resonance imaging (MRI)-guided prostate intervention, we developed a motorized MRI-compatible needle guide template that resembles a transrectal ultrasound-guided prostate template. The motorized template allows automated, gapless needle guidance in a 3T MRI scanner with minimal changes in the current clinical procedure. To evaluate the impact of the motorized template on MRI, signal-to-noise ratio and distortion were measured under various system configurations. A maximum of 44% signal-to-noise ratio decrease was found when the ultrasonic motors were running, and a maximum of 0.4% image distortion was observed due to the presence of the motorized template. To measure needle insertion accuracy, we performed four sets of five random target needle insertions mimicking four biopsy procedures, which resulted in an average in-plane targeting error of 0.94 mm with a standard deviation of 0.34 mm. The evaluation studies indicated that the presence and operation of the motorized template in the MRI bore create insignificant image degradation, and provide submillimeter targeting accuracy. The automated needle guide that is directly controlled by navigation software eliminates human error so that the safety of the procedure can be improved.
Gang Li, Hao Su, Weijian Shang, Junichi Tokuda, Nobuhiko Hata, Clare M Tempany, and Gregory S Fischer. 2013. “A Fully Actuated Robotic Assistant for MRI-Guided Prostate Biopsy and Brachytherapy.” Proc SPIE Int Soc Opt Eng, 8671, Pp. 867117.Abstract
Intra-operative medical imaging enables incorporation of human experience and intelligence in a controlled, closed-loop fashion. Magnetic resonance imaging (MRI) is an ideal modality for surgical guidance of diagnostic and therapeutic procedures, with its ability to perform high resolution, real-time, high soft tissue contrast imaging without ionizing radiation. However, for most current image-guided approaches only static pre-operative images are accessible for guidance, which are unable to provide updated information during a surgical procedure. The high magnetic field, electrical interference, and limited access of closed-bore MRI render great challenges to developing robotic systems that can perform inside a diagnostic high-field MRI while obtaining interactively updated MR images. To overcome these limitations, we are developing a piezoelectrically actuated robotic assistant for actuated percutaneous prostate interventions under real-time MRI guidance. Utilizing a modular design, the system enables coherent and straight forward workflow for various percutaneous interventions, including prostate biopsy sampling and brachytherapy seed placement, using various needle driver configurations. The unified workflow compromises: 1) system hardware and software initialization, 2) fiducial frame registration, 3) target selection and motion planning, 4) moving to the target and performing the intervention (e.g. taking a biopsy sample) under live imaging, and 5) visualization and verification. Phantom experiments of prostate biopsy and brachytherapy were executed under MRI-guidance to evaluate the feasibility of the workflow. The robot successfully performed fully actuated biopsy sampling and delivery of simulated brachytherapy seeds under live MR imaging, as well as precise delivery of a prostate brachytherapy seed distribution with an RMS accuracy of 0.98mm.
Takahisa Kato, Ichiro Okumura, Sang-Eun Song, and Nobuhiko Hata. 2013. “Multi-section continuum robot for endoscopic surgical clipping of intracranial aneurysms.” Med Image Comput Comput Assist Interv, 16, Pt 1, Pp. 364-71.Abstract
We propose the development and assessment of a multi-section continuum robot for endoscopic surgical clipping of intracranial aneurysms. The robot has two sections for bending actuated by tendon wires. By actuating the two sections independently, the robot can generate a variety of posture combinations by these sections while maintaining the tip angle. This feature offers more flexibility in positioning of the tip than a conventional endoscope for large viewing angles of up to 180 degrees. To estimate the flexible positioning of the tip, we developed kinematic mapping with friction in tendon wires. In a kinematic-mapping simulation, the two-section robot at the target scale (i.e., an outer diameter of 1.7 mm and a length of 60 mm) had a variety of tip positions within 50-mm ranges at the 180 degree-angled view. In the experimental validation, the 1:10 scale prototype performed the three salient postures with different tip positions at the 1800-angled view.
Sohrab Eslami, Gregory S Fischer, Sang-Eun Song, Junichi Tokuda, Nobuhiko Hata, Clare M Tempany, and Iulian Iordachita. 2013. “Towards Clinically Optimized MRI-guided Surgical Manipulator for Minimally Invasive Prostate Percutaneous Interventions: Constructive Design.” IEEE Int Conf Robot Autom, 20132, Pp. 1228-1233.Abstract
This paper undertakes the modular design and development of a minimally invasive surgical manipulator for MRI-guided transperineal prostate interventions. Severe constraints for the MRI-compatibility to hold the minimum artifact on the image quality and dimensions restraint of the bore scanner shadow the design procedure. Regarding the constructive design, the manipulator kinematics has been optimized and the effective analytical needle workspace is developed and followed by proposing the workflow for the manual needle insertion. A study of the finite element analysis is established and utilized to improve the mechanism weaknesses under some inevitable external forces to ensure the minimum structure deformation. The procedure for attaching a sterile plastic drape on the robot manipulator is discussed. The introduced robotic manipulator herein is aimed for the clinically prostate biopsy and brachytherapy applications.
Sang-Eun Song, Nobuhiko Hata, Iulian Iordachita, Gabor Fichtinger, Clare Tempany, and Junichi Tokuda. 2013. “A workspace-orientated needle-guiding robot for 3T MRI-guided transperineal prostate intervention: evaluation of in-bore workspace and MRI compatibility.” Int J Med Robot, 9, 1, Pp. 67-74.Abstract
BACKGROUND: Magnetic resonance imaging (MRI)-guided prostate interventions have been introduced to enhance the cancer detection. For accurate needle positioning, in-bore-operated robotic systems have been developed and optimal use of the confined in-bore space become a critical engineering challenge. METHODS: As preliminary evaluation of our prostate intervention robot, we conducted a workspace design analysis, using a new evaluation method that we developed for in-bore-operated robots for transperineal prostate interventions, and an MRI compatibility study. RESULTS: The workspace analysis resulted in the effective workspace (VW ) of 0.32, which is greater than that of our early prototype, despite the current robot being ca. 50% larger than the early prototype in sectional space. The MRI compatibility study resulted in < 15% signal:noise ratio (SNR) reduction. CONCLUSIONS: The new workspace evaluation method quantifies the workspace utilization of the in-bore-operated robots for MRI-guided transperineal prostate interventions, providing a useful tool for evaluation and new robot design. The robot creates insignificant electromagnetic noise during typical prostate imaging sequences.
2012
Andriy Fedorov, Kemal Tuncali, Fiona M Fennessy, Junichi Tokuda, Nobuhiko Hata, William M Wells, Ron Kikinis, and Clare M Tempany. 2012. “Image registration for targeted MRI-guided transperineal prostate biopsy.” J Magn Reson Imaging, 36, 4, Pp. 987-92.Abstract
PURPOSE: To develop and evaluate image registration methodology for automated re-identification of tumor-suspicious foci from preprocedural MR exams during MR-guided transperineal prostate core biopsy. MATERIALS AND METHODS: A hierarchical approach for automated registration between planning and intra-procedural T2-weighted prostate MRI was developed and evaluated on the images acquired during 10 consecutive MR-guided biopsies. Registration accuracy was quantified at image-based landmarks and by evaluating spatial overlap for the manually segmented prostate and sub-structures. Registration reliability was evaluated by simulating initial mis-registration and analyzing the convergence behavior. Registration precision was characterized at the planned biopsy targets. RESULTS: The total computation time was compatible with a clinical setting, being at most 2 min. Deformable registration led to a significant improvement in spatial overlap of the prostate and peripheral zone contours compared with both rigid and affine registration. Average in-slice landmark registration error was 1.3 ± 0.5 mm. Experiments simulating initial mis-registration resulted in an estimated average capture range of 6 mm and an average in-slice registration precision of ±0.3 mm. CONCLUSION: Our registration approach requires minimum user interaction and is compatible with the time constraints of our interventional clinical workflow. The initial evaluation shows acceptable accuracy, reliability and consistency of the method.
Junichi Tokuda, Kemal Tuncali, Iulian Iordachita, Sang-Eun Song, Andriy Fedorov, Sota Oguro, Andras Lasso, Fiona M Fennessy, Clare M Tempany, and Nobuhiko Hata. 2012. “In-bore setup and software for 3T MRI-guided transperineal prostate biopsy.” Phys Med Biol, 57, 18, Pp. 5823-40.Abstract
MRI-guided prostate biopsy in conventional closed-bore scanners requires transferring the patient outside the bore during needle insertion due to the constrained in-bore space, causing a safety hazard and limiting image feedback. To address this issue, we present our custom-made in-bore setup and software to support MRI-guided transperineal prostate biopsy in a wide-bore 3 T MRI scanner. The setup consists of a specially designed tabletop and a needle-guiding template with a Z-frame that gives a physician access to the perineum of the patient at the imaging position and allows the physician to perform MRI-guided transperineal biopsy without moving the patient out of the scanner. The software and Z-frame allow registration of the template, target planning and biopsy guidance. Initially, we performed phantom experiments to assess the accuracy of template registration and needle placement in a controlled environment. Subsequently, we embarked on our clinical trial (N = 10). The phantom experiments showed that the translational errors of the template registration along the right-left (RP) and anterior-posterior (AP) axes were 1.1 ± 0.8 and 1.4 ± 1.1 mm, respectively, while the rotational errors around the RL, AP and superior-inferior axes were (0.8 ± 1.0)°, (1.7 ± 1.6)° and (0.0 ± 0.0)°, respectively. The 2D root-mean-square (RMS) needle-placement error was 3 mm. The clinical biopsy procedures were safely carried out in all ten clinical cases with a needle-placement error of 5.4 mm (2D RMS). In conclusion, transperineal prostate biopsy in a wide-bore 3T scanner is feasible using our custom-made tabletop setup and software, which supports manual needle placement without moving the patient out of the magnet.
Gábor Kósa, Péter Jakab, Gábor Székely, and Nobuhiko Hata. 2012. “MRI driven magnetic microswimmers.” Biomed Microdevices, 14, 1, Pp. 165-78.Abstract
Capsule endoscopy is a promising technique for diagnosing diseases in the digestive system. Here we design and characterize a miniature swimming mechanism that uses the magnetic fields of the MRI for both propulsion and wireless powering of the capsule. Our method uses both the static and the radio frequency (RF) magnetic fields inherently available in MRI to generate a propulsive force. Our study focuses on the evaluation of the propulsive force for different swimming tails and experimental estimation of the parameters that influence its magnitude. We have found that an approximately 20 mm long, 5 mm wide swimming tail is capable of producing 0.21 mN propulsive force in water when driven by a 20 Hz signal providing 0.85 mW power and the tail located within the homogeneous field of a 3 T MRI scanner. We also analyze the parallel operation of the swimming mechanism and the scanner imaging. We characterize the size of artifacts caused by the propulsion system. We show that while the magnetic micro swimmer is propelling the capsule endoscope, the operator can locate the capsule on the image of an interventional scene without being obscured by significant artifacts. Although this swimming method does not scale down favorably, the high magnetic field of the MRI allows self propulsion speed on the order of several millimeter per second and can propel an endoscopic capsule in the stomach.
Junichi Tokuda, Sang-Eun Song, Gregory S Fischer, Iulian I Iordachita, Reza Seifabadi, Nathan B Cho, Kemal Tuncali, Gabor Fichtinger, Clare M Tempany, and Nobuhiko Hata. 2012. “Preclinical evaluation of an MRI-compatible pneumatic robot for angulated needle placement in transperineal prostate interventions.” Int J Comput Assist Radiol Surg, 7, 6, Pp. 949-57.Abstract
PURPOSE: To evaluate the targeting accuracy of a small profile MRI-compatible pneumatic robot for needle placement that can angulate a needle insertion path into a large accessible target volume. METHODS: We extended our MRI-compatible pneumatic robot for needle placement to utilize its four degrees-of-freedom (4-DOF) mechanism with two parallel triangular structures and support transperineal prostate biopsies in a closed-bore magnetic resonance imaging (MRI) scanner. The robot is designed to guide a needle toward a lesion so that a radiologist can manually insert it in the bore. The robot is integrated with navigation software that allows an operator to plan angulated needle insertion by selecting a target and an entry point. The targeting error was evaluated while the angle between the needle insertion path and the static magnetic field was between -5.7° and 5.7° horizontally and between -5.7° and 4.3° vertically in the MRI scanner after sterilizing and draping the device. RESULTS: The robot positioned the needle for angulated insertion as specified on the navigation software with overall targeting error of 0.8 ± 0.5mm along the horizontal axis and 0.8 ± 0.8mm along the vertical axis. The two-dimensional root-mean-square targeting error on the axial slices as containing the targets was 1.4mm. CONCLUSIONS: Our preclinical evaluation demonstrated that the MRI-compatible pneumatic robot for needle placement with the capability to angulate the needle insertion path provides targeting accuracy feasible for clinical MRI-guided prostate interventions. The clinical feasibility has to be established in a clinical study.
2011
Thomas Maier, Gero Strauss, Franz Bauer, Andreas Grasser, Nobuhiko Hata, and Tim C Lueth. 2011. “Distance measurement in middle ear surgery using a telemanipulator.” Med Image Comput Comput Assist Interv, 14, Pt 1, Pp. 41-8.Abstract
In this article, a new tool for the intraoperative measurement of distances within the middle ear by means of a micromanipulator is presented. The purpose of this work was to offer the surgeon a highly accurate tool for measuring the distances between two points in the 3D operational field. The tool can be useful in various operations; this article focuses, however, on measuring the distance between the stapes footplate and the long process of the incus of the middle ear. This distance is important for estimating the proper prosthesis length in stapedotomy for treating otosclerosis. We evaluated the system using a simplified mechanical model. Our results show that the system can measure distances with a maximum error of 0.04 mm.
Hao Su, Alex Camilo, Gregory A Cole, Nobuhiko Hata, Clare M Tempany, and Gregory S Fischer. 2011. “High-field MRI-compatible needle placement robot for prostate interventions.” Stud Health Technol Inform, 163, Pp. 623-9.Abstract
This paper presents the design of a magnetic resonance imaging (MRI) compatible needle placement system actuated by piezoelectric actuators for prostate brachytherapy and biopsy. An MRI-compatible modular 3 degree-of-freedom (DOF) needle driver module coupled with a 3-DOF x-y-z stage is proposed as a slave robot to precisely deliver radioactive brachytherapy seeds under interactive MRI guidance. The needle driver module provides for needle cannula rotation, needle insertion and cannula retraction to enable the brachytherapy procedure with the preloaded needles. The device mimics the manual physician gesture by two point grasping (hub and base) and provides direct force measurement of needle insertion force by fiber optic force sensors. The fabricated prototype is presented and an experiment with phantom trials in 3T MRI is analyzed to demonstrate the system compatibility.
Sota Oguro, Kemal Tuncali, Haytham Elhawary, Paul R Morrison, Nobuhiko Hata, and Stuart G Silverman. 2011. “Image registration of pre-procedural MRI and intra-procedural CT images to aid CT-guided percutaneous cryoablation of renal tumors.” Int J Comput Assist Radiol Surg, 6, 1, Pp. 111-7.Abstract
PURPOSE: To determine whether a non-rigid registration (NRR) technique was more accurate than a rigid registration (RR) technique when fusing pre-procedural contrast-enhanced MR images to unenhanced CT images during CT-guided percutaneous cryoablation of renal tumors. METHODS: Both RR and NRR were applied retrospectively to 11 CT-guided percutaneous cryoablation procedures performed to treat renal tumors (mean diameter; 23 mm). Pre-procedural contrast-enhanced MR images of the upper abdomen were registered to unenhanced intra-procedural CT images obtained just prior to the ablation. RRs were performed manually, and NRRs were performed using an intensity-based approach with affine and Basis-Spline techniques used for modeling displacement. Registration accuracy for each technique was assessed using the 95% Hausdorff distance (HD), Fiducial Registration Error (FRE) and the Dice Similarity Coefficient (DSC). Statistical differences were analyzed using a two-sided Student's t-test. Time for each registration technique was recorded. RESULTS: Mean 95% HD (1.7 mm), FRE (1.7 mm) and DSC (0.96) using the NRR technique were significantly better than mean 95% HD (6.4 mm), FRE (5.0 mm) and DSC (0.88) using the RR technique (P < 0.05 for each analysis). Mean registration times of NRR and RR techniques were 15.2 and 5.7 min, respectively. CONCLUSIONS: The non-rigid registration technique was more accurate than the rigid registration technique when fusing pre-procedural MR images to intra-procedural unenhanced CT images. The non-rigid registration technique can be used to improve visualization of renal tumors during CT-guided cryoablation procedures.
Junichi Tokuda, Hatsuho Mamata, Ritu R Gill, Nobuhiko Hata, Ron Kikinis, Robert F Padera, Robert E Lenkinski, David J Sugarbaker, and Hiroto Hatabu. 2011. “Impact of nonrigid motion correction technique on pixel-wise pharmacokinetic analysis of free-breathing pulmonary dynamic contrast-enhanced MR imaging.” J Magn Reson Imaging, 33, 4, Pp. 968-73.Abstract
PURPOSE: To investigates the impact of nonrigid motion correction on pixel-wise pharmacokinetic analysis of free-breathing DCE-MRI in patients with solitary pulmonary nodules (SPNs). Misalignment of focal lesions due to respiratory motion in free-breathing dynamic contrast-enhanced MRI (DCE-MRI) precludes obtaining reliable time-intensity curves, which are crucial for pharmacokinetic analysis for tissue characterization. MATERIALS AND METHODS: Single-slice 2D DCE-MRI was obtained in 15 patients. Misalignments of SPNs were corrected using nonrigid B-spline image registration. Pixel-wise pharmacokinetic parameters K(trans) , v(e) , and k(ep) were estimated from both original and motion-corrected DCE-MRI by fitting the two-compartment pharmacokinetic model to the time-intensity curve obtained in each pixel. The "goodness-of-fit" was tested with χ(2) -test in pixel-by-pixel basis to evaluate the reliability of the parameters. The percentages of reliable pixels within the SPNs were compared between the original and motion-corrected DCE-MRI. In addition, the parameters obtained from benign and malignant SPNs were compared. RESULTS: The percentage of reliable pixels in the motion-corrected DCE-MRI was significantly larger than the original DCE-MRI (P = 4 × 10(-7) ). Both K(trans) and k(ep) derived from the motion-corrected DCE-MRI showed significant differences between benign and malignant SPNs (P = 0.024, 0.015). CONCLUSION: The study demonstrated the impact of nonrigid motion correction technique on pixel-wise pharmacokinetic analysis of free-breathing DCE-MRI in SPNs.
Haytham Elhawary, Haiying Liu, Pratik Patel, Isaiah Norton, Laura Rigolo, Xenophon Papademetris, Nobuhiko Hata, and Alexandra J Golby. 2011. “Intraoperative real-time querying of white matter tracts during frameless stereotactic neuronavigation.” Neurosurgery, 68, 2, Pp. 506-16; discussion 516.Abstract
BACKGROUND: Brain surgery faces important challenges when trying to achieve maximum tumor resection while avoiding postoperative neurological deficits. OBJECTIVE: For surgeons to have optimal intraoperative information concerning white matter (WM) anatomy, we developed a platform that allows the intraoperative real-time querying of tractography data sets during frameless stereotactic neuronavigation. METHODS: Structural magnetic resonance imaging, functional magnetic resonance imaging, and diffusion tensor imaging were performed on 5 patients before they underwent lesion resection using neuronavigation. During the procedure, the tracked surgical tool tip position was transferred from the navigation system to the 3-dimensional Slicer software package, which used this position to seed the WM tracts around the tool tip location, rendering a geometric visualization of these tracts on the preoperative images previously loaded onto the navigation system. The clinical feasibility of this approach was evaluated in 5 cases of lesion resection. In addition, system performance was evaluated by measuring the latency between surgical tool tracking and visualization of the seeded WM tracts. RESULTS: Lesion resection was performed successfully in all 5 patients. The seeded WM tracts close to the lesion and other critical structures, as defined by the functional and structural images, were interactively visualized during the intervention to determine their spatial relationships relative to the lesion and critical cortical areas. Latency between tracking and visualization of tracts was less than a second for a fiducial radius size of 4 to 5 mm. CONCLUSION: Interactive tractography can provide an intuitive way to inspect critical WM tracts in the vicinity of the surgical region, allowing the surgeon to have increased intraoperative WM information to execute the planned surgical resection.
2010
Junichi Tokuda, Gregory S Fischer, Simon P Dimaio, David G Gobbi, Csaba Csoma, Philip W Mewes, Gabor Fichtinger, Clare M Tempany, and Nobuhiko Hata. 2010. “Integrated navigation and control software system for MRI-guided robotic prostate interventions.” Comput Med Imaging Graph, 34, 1, Pp. 3-8.Abstract
A software system to provide intuitive navigation for MRI-guided robotic transperineal prostate therapy is presented. In the system, the robot control unit, the MRI scanner, and the open-source navigation software are connected together via Ethernet to exchange commands, coordinates, and images using an open network communication protocol, OpenIGTLink. The system has six states called "workphases" that provide the necessary synchronization of all components during each stage of the clinical workflow, and the user interface guides the operator linearly through these workphases. On top of this framework, the software provides the following features for needle guidance: interactive target planning; 3D image visualization with current needle position; treatment monitoring through real-time MR images of needle trajectories in the prostate. These features are supported by calibration of robot and image coordinates by fiducial-based registration. Performance tests show that the registration error of the system was 2.6mm within the prostate volume. Registered real-time 2D images were displayed 1.97 s after the image location is specified.
Haytham Elhawary, Sota Oguro, Kemal Tuncali, Paul R Morrison, Servet Tatli, Paul B Shyn, Stuart G Silverman, and Nobuhiko Hata. 2010. “Multimodality non-rigid image registration for planning, targeting and monitoring during CT-guided percutaneous liver tumor cryoablation.” Acad Radiol, 17, 11, Pp. 1334-44.Abstract
RATIONALE AND OBJECTIVES: The aim of this study was to develop non-rigid image registration between preprocedure contrast-enhanced magnetic resonance (MR) images and intraprocedure unenhanced computed tomographic (CT) images, to enhance tumor visualization and localization during CT imaging-guided liver tumor cryoablation procedures. MATERIALS AND METHODS: A non-rigid registration technique was evaluated with different preprocessing steps and algorithm parameters and compared to a standard rigid registration approach. The Dice similarity coefficient, target registration error, 95th-percentile Hausdorff distance, and total registration time (minutes) were compared using a two-sided Student's t test. The entire registration method was then applied during five CT imaging-guided liver cryoablation cases with the intraprocedural CT data transmitted directly from the CT scanner, with both accuracy and registration time evaluated. RESULTS: Selected optimal parameters for registration were a section thickness of 5 mm, cropping the field of view to 66% of its original size, manual segmentation of the liver, B-spline control grid of 5 × 5 × 5, and spatial sampling of 50,000 pixels. A mean 95th-percentile Hausdorff distance of 3.3 mm (a 2.5 times improvement compared to rigid registration, P < .05), a mean Dice similarity coefficient of 0.97 (a 13% increase), and a mean target registration error of 4.1 mm (a 2.7 times reduction) were measured. During the cryoablation procedure, registration between the preprocedure MR and the planning intraprocedure CT imaging took a mean time of 10.6 minutes, MR to targeting CT image took 4 minutes, and MR to monitoring CT imaging took 4.3 minutes. Mean registration accuracy was <3.4 mm. CONCLUSIONS: Non-rigid registration allowed improved visualization of the tumor during interventional planning, targeting, and evaluation of tumor coverage by the ice ball. Future work is focused on reducing segmentation time to make the method more clinically acceptable.
Jumpei Arata, Hiroaki Kozuka, Hyung Wook Kim, Naoyuki Takesue, B Vladimirov, Masamichi Sakaguchi, Junichi Tokuda, Nobuhiko Hata, Kiyoyuki Chinzei, and Hideo Fujimoto. 2010. “Open core control software for surgical robots.” Int J Comput Assist Radiol Surg, 5, 3, Pp. 211-20.Abstract
OBJECT: In these days, patients and doctors in operation room are surrounded by many medical devices as resulting from recent advancement of medical technology. However, these cutting-edge medical devices are working independently and not collaborating with each other, even though the collaborations between these devices such as navigation systems and medical imaging devices are becoming very important for accomplishing complex surgical tasks (such as a tumor removal procedure while checking the tumor location in neurosurgery). On the other hand, several surgical robots have been commercialized, and are becoming common. However, these surgical robots are not open for collaborations with external medical devices in these days. A cutting-edge "intelligent surgical robot" will be possible in collaborating with surgical robots, various kinds of sensors, navigation system and so on. On the other hand, most of the academic software developments for surgical robots are "home-made" in their research institutions and not open to the public. Therefore, open source control software for surgical robots can be beneficial in this field. From these perspectives, we developed Open Core Control software for surgical robots to overcome these challenges. MATERIALS AND METHODS: In general, control softwares have hardware dependencies based on actuators, sensors and various kinds of internal devices. Therefore, these control softwares cannot be used on different types of robots without modifications. However, the structure of the Open Core Control software can be reused for various types of robots by abstracting hardware dependent parts. In addition, network connectivity is crucial for collaboration between advanced medical devices. The OpenIGTLink is adopted in Interface class which plays a role to communicate with external medical devices. At the same time, it is essential to maintain the stable operation within the asynchronous data transactions through network. In the Open Core Control software, several techniques for this purpose were introduced. Virtual fixture is well known technique as a "force guide" for supporting operators to perform precise manipulation by using a master-slave robot. The virtual fixture for precise and safety surgery was implemented on the system to demonstrate an idea of high-level collaboration between a surgical robot and a navigation system. The extension of virtual fixture is not a part of the Open Core Control system, however, the function such as virtual fixture cannot be realized without a tight collaboration between cutting-edge medical devices. By using the virtual fixture, operators can pre-define an accessible area on the navigation system, and the area information can be transferred to the robot. In this manner, the surgical console generates the reflection force when the operator tries to get out from the pre-defined accessible area during surgery. RESULTS: The Open Core Control software was implemented on a surgical master-slave robot and stable operation was observed in a motion test. The tip of the surgical robot was displayed on a navigation system by connecting the surgical robot with a 3D position sensor through the OpenIGTLink. The accessible area was pre-defined before the operation, and the virtual fixture was displayed as a "force guide" on the surgical console. In addition, the system showed stable performance in a duration test with network disturbance. CONCLUSION: In this paper, a design of the Open Core Control software for surgical robots and the implementation of virtual fixture were described. The Open Core Control software was implemented on a surgical robot system and showed stable performance in high-level collaboration works. The Open Core Control software is developed to be a widely used platform of surgical robots. Safety issues are essential for control software of these complex medical devices. It is important to follow the global specifications such as a FDA requirement "General Principles of Software Validation" or IEC62304. For following these regulations, it is important to develop a self-test environment. Therefore, a test environment is now under development to test various interference in operation room such as a noise of electric knife by considering safety and test environment regulations such as ISO13849 and IEC60508. The Open Core Control software is currently being developed software in open-source manner and available on the Internet. A communization of software interface is becoming a major trend in this field. Based on this perspective, the Open Core Control software can be expected to bring contributions in this field.
Sang-Eun Song, Nathan Cho, Junichi Tokuda, Nobuhiko Hata, Clare Tempany, Gabor Fichtinger, and Iulian Iordachita. 2010. “Preliminary Evaluation of a MRI-compatible Modular Robotic System for MRI-guided Prostate Interventions.” Proc IEEE RAS EMBS Int Conf Biomed Robot Biomechatron, 2010, Pp. 796-801.Abstract
Magnetic Resonance Imaging (MRI) guided robotic interventions have been introduced in order to advance prostate cancer detection and treatment. To overcome problems of such robotic interventions, we have been developing a pneumatically actuated MRI-compatible modular robotic system for MRI-guided transperineal prostate intervention and its interventional procedure. For system evaluation, a series of experiments have been conducted and this paper reports a needle insertion experiment using prostate phantom and patient mockup trials. The needle insertion experiment resulted in noticeable consistent error in one direction, which we will investigate further. Nonetheless, patient mockup experiences suggest that the modular robotic system and its interventional procedure are well integrated and implemented in clinical environment.
2009
Junichi Tokuda, Melanie Schmitt, Yanping Sun, Samuel Patz, Yi Tang, Carolyn E Mountford, Nobuhiko Hata, Lawrence L Wald, and Hiroto Hatabu. 2009. “Lung motion and volume measurement by dynamic 3D MRI using a 128-channel receiver coil.” Acad Radiol, 16, 1, Pp. 22-7.Abstract
RATIONALE AND OBJECTIVES: The authors present their initial experience using a 3-T whole-body scanner equipped with a 128-channel coil applied to lung motion assessment. Recent improvements in fast magnetic resonance imaging (MRI) technology have enabled several trials of free-breathing three-dimensional (3D) imaging of the lung. A large number of image frames necessarily increases the difficulty of image analysis and therefore warrants automatic image processing. However, the intensity homogeneities of images of prior dynamic 3D lung MRI studies have been insufficient to use such methods. In this study, initial data were obtained at 3 T with a 128-channel coil that demonstrate the feasibility of acquiring multiple sets of 3D pulmonary scans during free breathing and that have sufficient quality to be amenable to automatic segmentation. MATERIALS AND METHODS: Dynamic 3D images of the lungs of two volunteers were acquired with acquisition times of 0.62 to 0.76 frames/s and an image matrix of 128 x 128, with 24 to 30 slice encodings. The volunteers were instructed to take shallow and deep breaths during the scans. The variation of lung volume was measured from the segmented images. RESULTS: Dynamic 3D images were successfully acquired for both respiratory conditions for each subject. The images showed whole-lung motion, including lifting of the chest wall and the displacement of the diaphragm, with sufficient contrast to distinguish these structures from adjacent tissues. The average time to complete segmentation for one 3D image was 4.8 seconds. The tidal volume measured was consistent with known tidal volumes for healthy subjects performing deep-breathing maneuvers. The temporal resolution was insufficient to measure tidal volumes for shallow breathing. CONCLUSION: This initial experience with a 3-T whole-body scanner and a 128-channel coil showed that the scanner and imaging protocol provided dynamic 3D images with spatial and temporal resolution sufficient to delineate the diaphragmatic domes and chest wall during active breathing. In addition, the intensity homogeneities and signal-to-noise ratio were adequate to perform automatic segmentation.

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