Publications

2010
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.
Sota Oguro, Junichi Tokuda, Haytham Elhawary, Steven Haker, Ron Kikinis, Clare MC Tempany, and Nobuhiko Hata. 2009. “MRI signal intensity based B-spline nonrigid registration for pre- and intraoperative imaging during prostate brachytherapy.” J Magn Reson Imaging, 30, 5, Pp. 1052-8.Abstract
PURPOSE: To apply an intensity-based nonrigid registration algorithm to MRI-guided prostate brachytherapy clinical data and to assess its accuracy. MATERIALS AND METHODS: A nonrigid registration of preoperative MRI to intraoperative MRI images was carried out in 16 cases using a Basis-Spline algorithm in a retrospective manner. The registration was assessed qualitatively by experts' visual inspection and quantitatively by measuring the Dice similarity coefficient (DSC) for total gland (TG), central gland (CG), and peripheral zone (PZ), the mutual information (MI) metric, and the fiducial registration error (FRE) between corresponding anatomical landmarks for both the nonrigid and a rigid registration method. RESULTS: All 16 cases were successfully registered in less than 5 min. After the nonrigid registration, DSC values for TG, CG, PZ were 0.91, 0.89, 0.79, respectively, the MI metric was -0.19 +/- 0.07 and FRE presented a value of 2.3 +/- 1.8 mm. All the metrics were significantly better than in the case of rigid registration, as determined by one-sided t-tests. CONCLUSION: The intensity-based nonrigid registration method using clinical data was demonstrated to be feasible and showed statistically improved metrics when compare to only rigid registration. The method is a valuable tool to integrate pre- and intraoperative images for brachytherapy.
Junichi Tokuda, Gregory S Fischer, Xenophon Papademetris, Ziv Yaniv, Luis Ibanez, Patrick Cheng, Haiying Liu, Jack Blevins, Jumpei Arata, Alexandra J Golby, Tina Kapur, Steve Pieper, Everette C Burdette, Gabor Fichtinger, Clare M Tempany, and Nobuhiko Hata. 2009. “OpenIGTLink: an open network protocol for image-guided therapy environment.” Int J Med Robot, 5, 4, Pp. 423-34.Abstract
BACKGROUND: With increasing research on system integration for image-guided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status. METHOD: We propose a new, open, simple and extensible network communication protocol for IGT, named OpenIGTLink, to transfer transform, image and status messages. We conducted performance tests and use-case evaluations in five clinical and engineering scenarios. RESULTS: The protocol was able to transfer position data with submillisecond latency up to 1024 fps and images with latency of <10 ms at 32 fps. The use-case tests demonstrated that the protocol is feasible for integrating devices and software. CONCLUSION: The protocol proved capable of handling data required in the IGT setting with sufficient time resolution and latency. The protocol not only improves the interoperability of devices and software but also promotes transitions of research prototypes to clinical applications.
Shigehiro Morikawa, Shigeyuki Naka, Koichiro Murakami, Yoshimasa Kurumi, Hisanori Shiomi, Tohru Tani, Hasnine A Haque, Junichi Tokuda, Nobuhiko Hata, and Toshiro Inubushi. 2009. “Preliminary clinical experiences of a motorized manipulator for magnetic resonance image-guided microwave coagulation therapy of liver tumors.” Am J Surg, 198, 3, Pp. 340-7.Abstract
BACKGROUND: In magnetic resonance (MR) image-guided microwave thermocoagulation of liver tumors, the choice of the optimal puncture route is an important and time-consuming process. To assist this process, we have developed a motorized MR-compatible manipulator. METHODS: The manipulator consists of a passive end effecter with 2 degrees-of-freedom (DOF) rotation and active base stages with 3 ultrasonic motors. It automatically chases the preset target point with synergetic remote-center-of-motion (RCM) control. A mechanical torque limiter and an electrical shutdown switch were added for patient safety. RESULTS: The manipulator was used for this procedure in 15 cases and successfully utilized to treat liver tumors in various locations. Thoracoscopic assistance was combined with the manipulator in 6 cases. No complications were experienced. CONCLUSIONS: The manipulator was found to be very effective for assisting MR-guided microwave coagulation of liver tumors.
2008
Polina Golland, Nobuhiko Hata, Sebastien Ourselin, and Nicholas Ayache. 2008. “Advances in radiological image analysis from MICCAI 2007.” Acad Radiol, 15, 11, Pp. 1345-6.
Peter Kazanzides, Tian Xia, Clint Baird, George Jallo, Kathryn Hayes, Nobuyuki Nakajima, and Nobuhiko Hata. 2008. “A cooperatively-controlled image guided robot system for skull base surgery.” Stud Health Technol Inform, 132, Pp. 198-203.Abstract
We created an image-guided robot system to assist with skull base drilling by integrating a robot, a commercial navigation system, and an open source visualization platform. The objective of this procedure is to create a cavity in the skull base to allow access for neurosurgical interventions. The motivation for introducing an image-guided robot is to improve safety by preventing the surgeon from accidentally damaging critical structures during the drilling procedure. Our approach is to attach the cutting tool to the robot end-effector and operate the robot in a cooperative control mode, where robot motion is determined from the forces and torques applied by the surgeon. We employ "virtual fixtures" to constrain the motion of the cutting tool so that it remains in the safe zone that was defined on a preoperative CT scan. This paper presents the system design and the results of phantom and cadaveric experiments. Both experiments have demonstrated the feasibility of the system, with average overcut error at about 1 mm and maximum errors at 2.5 mm.
Tian Xia, Clint Baird, George Jallo, Kathryn Hayes, Nobuyuki Nakajima, Nobuhiko Hata, and Peter Kazanzides. 2008. “An integrated system for planning, navigation and robotic assistance for skull base surgery.” Int J Med Robot, 4, 4, Pp. 321-30.Abstract
BACKGROUND: We developed an image-guided robot system to provide mechanical assistance for skull base drilling, which is performed to gain access for some neurosurgical interventions, such as tumour resection. The motivation for introducing this robot was to improve safety by preventing the surgeon from accidentally damaging critical neurovascular structures during the drilling procedure. METHODS: We integrated a Stealthstation navigation system, a NeuroMate robotic arm with a six-degree-of-freedom force sensor, and the 3D Slicer visualization software to allow the robotic arm to be used in a navigated, cooperatively-controlled fashion by the surgeon. We employed virtual fixtures to constrain the motion of the robot-held cutting tool, so that it remained in the safe zone that was defined on a preoperative CT scan. RESULTS: We performed experiments on both foam skull and cadaver heads. The results for foam blocks cut using different registrations yielded an average placement error of 0.6 mm and an average dimensional error of 0.6 mm. We drilled the posterior porus acusticus in three cadaver heads and concluded that the robot-assisted procedure is clinically feasible and provides some ergonomic benefits, such as stabilizing the drill. We obtained postoperative CT scans of the cadaver heads to assess the accuracy and found that some bone outside the virtual fixture boundary was cut. The typical overcut was 1-2 mm, with a maximum overcut of about 3 mm. CONCLUSIONS: The image-guided cooperatively-controlled robot system can improve the safety and ergonomics of skull base drilling by stabilizing the drill and enforcing virtual fixtures to protect critical neurovascular structures. The next step is to improve the accuracy so that the overcut can be reduced to a more clinically acceptable value of about 1 mm.
Clare Tempany, Sarah Straus, Nobuhiko Hata, and Steven Haker. 2008. “MR-guided prostate interventions.” J Magn Reson Imaging, 27, 2, Pp. 356-67.Abstract
In this article the current issues of diagnosis and detection of prostate cancer are reviewed. The limitations for current techniques are highlighted and some possible solutions with MR imaging and MR-guided biopsy approaches are reviewed. There are several different biopsy approaches under investigation. These include transperineal open magnet approaches to closed-bore 1.5T transrectal biopsies. The imaging, image processing, and tracking methods are also discussed. In the arena of therapy, MR guidance has been used in conjunction with radiation methods, either brachytherapy or external delivery. The principles of the radiation treatment, the toxicities, and use of images are outlined. The future role of imaging and image-guided interventions lie with providing a noninvasive surrogate for cancer surveillance or monitoring treatment response. The shift to minimally invasive focal therapies has already begun and will be very exciting when MR-guided focused ultrasound surgery reaches its full potential.
Nobuhiko Hata, Junichi Tokuda, Shelley Hurwitz, and Shigehiro Morikawa. 2008. “MRI-compatible manipulator with remote-center-of-motion control.” J Magn Reson Imaging, 27, 5, Pp. 1130-8.Abstract
PURPOSE: To develop and assess a needle-guiding manipulator for MRI-guided therapy that allows a physician to freely select the needle insertion path while maintaining remote center of motion (RCM) at the tumor site. MATERIALS AND METHODS: The manipulator consists of a three-degrees-of-freedom (DOF) base stage and passive needle holder with unconstrained two-DOF rotation. The synergistic control keeps the Virtual RCM at the preplanned target using encoder outputs from the needle holder as input to motorize the base stage. RESULTS: The manipulator assists in searching for an optimal needle insertion path which is a complex and time-consuming task in MRI-guided ablation therapy for liver tumors. The assessment study showed that accuracy of keeping the virtual RCM to predefined position is 3.0 mm. In a phantom test, the physicians found the needle insertion path faster with than without the manipulator (number of physicians = 3, P = 0.001). However, the alignment time with the virtual RCM was not shorter when imaging time for planning were considered. CONCLUSION: The study indicated that the robot holds promise as a tool for accurately and interactively selecting the optimal needle insertion path in liver ablation therapy guided by open-configuration MRI.
Gregory S Fischer, Iulian Iordachita, Csaba Csoma, Junichi Tokuda, Simon P Dimaio, Clare M Tempany, Nobuhiko Hata, and Gabor Fichtinger. 2008. “MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement.” IEEE ASME Trans Mechatron, 13, 3, Pp. 295-305.Abstract
Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system.
Gregory S Fischer, Iulian Iordachita, Csaba Csoma, Junichi Tokuda, Philip W Mewes, Clare M Tempany, Nobuhiko Hata, and Gabor Fichtinger. 2008. “Pneumatically Operated MRI-Compatible Needle Placement Robot for Prostate Interventions.” IEEE Int Conf Robot Autom, 2008, Pp. 2489-2495.Abstract
Magnetic Resonance Imaging (MRI) has potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. The strong magnetic field prevents the use of conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intra-prostatic needle placement inside closed high-field MRI scanners. The robot performs needle insertion under real-time 3T MR image guidance; workspace requirements, MR compatibility, and workflow have been evaluated on phantoms. The paper explains the robot mechanism and controller design and presents results of preliminary evaluation of the system.
Jens A Richolt, Nobuhiko Hata, Ron Kikinis, Detlef Scale, and Michael B Millis. 2008. “Quantitative evaluation of angular measurements on plain radiographs in patients with slipped capital femoral epiphysis: a 3-dimensional analysis of computed tomography-based computer models of 46 femora.” J Pediatr Orthop, 28, 3, Pp. 291-6.Abstract
BACKGROUND: In cases of slipped capital femoral epiphyses (SCFE) findings on plain radiographs help to determine the further necessary course of action. In severe cases possible surgical procedures are commonly indicated and planned using angular measurements on plain radiographs to describe the extent and direction of the slip. The aim of this study was to quantify the amount of angular errors deriving from this method. METHODS: Data and imaging of 23 consecutive patients with SCFE (31 affected and 15 unaffected femora) were included in this study. We determined shaft-neck/shaft-physis angles on antero-posterior and torsional angles on lateral radiographs in a clinical setting. As a reference we enabled similar angular measurements on CT-based three-dimensional computer models of the same femora bearing no projectional errors and malpositioning problems. RESULTS: In average, shaft-neck- and shaft-physis-angles were overestimated (6.5 degrees and 10.1 degrees ) on plain radiographs and neck torsion underestimated (-15.7 degrees ). In general the variability was high, especially for neck and physeal torsional measurements with standard deviations of +/-11.8 degrees and +/-16.7 degrees . Three out of four torsional measurements on affected femora were outside a +/-10 degrees window of error, about every third outside a +/-20 degrees window. CONCLUSION: Our results suggest to be careful when using plain radiographs as a source to determine the slippage extent in SCFE. Before using a plain radiograph to reject or indicate and plan a correction osteotomy in an individual case of SCFE the surgeon should reassure that radiographic method and patient positioning provide a reproducible and accurate depiction of the femoral geometry. LEVEL OF EVIDENCE: Level II; 23 consecutive patients with SCFE in the senior authors practice; evaluation of the reliability of angular measurements on plain radiographs; CT based 3D computer models of the same femora as a reference.
Jaesung Hong, Nobuhiko Hata, Kozo Konishi, and Makoto Hashizume. 2008. “Real-time magnetic resonance imaging driven by electromagnetic locator for interventional procedure and endoscopic therapy.” Surg Endosc, 22, 2, Pp. 552-6.Abstract
BACKGROUND: Surgical navigation systems using an optical position sensor have the occlusion problem due to a person or instrument in the line of sight of the camera. In this study, occlusion-free real-time magnetic resonance (MR) scanning with a passive electromagnetic locator is proposed. METHODS: A newly developed converter transforms the data of an electromagnetic locator into that of an optical sensor. Registration between the two different coordinate systems is performed for the electromagnetic locator to substitute the optical sensor without modifying the MRI system. RESULTS: An oil marker attached to the electromagnetic locator was identified in real-time MR images. Preliminary results demonstrated the high usability of the electromagnetic locator as an alternative position tracking method in the MR gantry. CONCLUSIONS: The occlusion problem of optical sensors is resolved by the proposed method.
Junichi Tokuda, Gregory S Fischer, Csaba Csoma, Simon P Dimaio, David G Gobbi, Gabor Fichtinger, Clare M Tempany, and Nobuhiko Hata. 2008. “Software strategy for robotic transperineal prostate therapy in closed-bore MRI.” Med Image Comput Comput Assist Interv, 11, Pt 2, Pp. 701-9.Abstract
A software strategy to provide intuitive navigation for MRI-guided robotic transperineal prostate therapy is presented. In the system, the robot control unit, the MRI scanner, and open-source navigation software are connected to one another via Ethernet to exchange commands, coordinates, and images. Six states of the system called "workphases" are defined based on the clinical scenario to synchronize behaviors of all components. The wizard-style user interface allows easy following of the clinical workflow. On top of this framework, the software provides features for intuitive needle guidance: interactive target planning; 3D image visualization with current needle position; treatment monitoring through real-time MRI. These features are supported by calibration of robot and image coordinates by the fiducial-based registration. The performance test shows that the registration error of the system was 2.6 mm in the prostate area, and it displayed real-time 2D image 1.7 s after the completion of image acquisition.
2007
Nobuhiko Hata, Steve Piper, Ferenc A Jolesz, Clare MC Tempany, Peter McL Black, Shigehiro Morikawa, Horoshi Iseki, Makoto Hashizume, and Ron Kikinis. 2007. “Application of open source image guided therapy software in MR-guided therapies.” Med Image Comput Comput Assist Interv, 10, Pt 1, Pp. 491-8.Abstract
We present software engineering methods to provide free open-source software for MR-guided therapy. We report that graphical representation of the surgical tools, interconnectively with the tracking device, patient-to-image registration, and MRI-based thermal mapping are crucial components of MR-guided therapy in sharing such software. Software process includes a network-based distribution mechanism by multi-platform compiling tool CMake, CVS, quality assurance software DART. We developed six procedures in four separate clinical sites using proposed software engineering and process, and found the proposed method is feasible to facilitate multicenter clinical trial of MR-guided therapies. Our future studies include use of the software in non-MR-guided therapies.
Simon DiMaio, Tina Kapur, Kevin Cleary, Stephen Aylward, Peter Kazanzides, Kirby Vosburgh, Randy Ellis, James Duncan, Keyvan Farahani, Heinz Lemke, Terry Peters, William Bill Lorensen, David Gobbi, John Haller, Laurence Larry Clarke, Stephen Pizer, Russell Taylor, Robert Galloway, Gabor Fichtinger, Nobuhiko Hata, Kimberly Lawson, Clare Tempany, Ron Kikinis, and Ferenc Jolesz. 2007. “Challenges in image-guided therapy system design.” Neuroimage, 37 Suppl 1, Pp. S144-51.Abstract
System development for image-guided therapy (IGT), or image-guided interventions (IGI), continues to be an area of active interest across academic and industry groups. This is an emerging field that is growing rapidly: major academic institutions and medical device manufacturers have produced IGT technologies that are in routine clinical use, dozens of high-impact publications are published in well regarded journals each year, and several small companies have successfully commercialized sophisticated IGT systems. In meetings between IGT investigators over the last two years, a consensus has emerged that several key areas must be addressed collaboratively by the community to reach the next level of impact and efficiency in IGT research and development to improve patient care. These meetings culminated in a two-day workshop that brought together several academic and industrial leaders in the field today. The goals of the workshop were to identify gaps in the engineering infrastructure available to IGT researchers, develop the role of research funding agencies and the recently established US-based National Center for Image Guided Therapy (NCIGT), and ultimately to facilitate the transfer of technology among research centers that are sponsored by the National Institutes of Health (NIH). Workshop discussions spanned many of the current challenges in the development and deployment of new IGT systems. Key challenges were identified in a number of areas, including: validation standards; workflows, use-cases, and application requirements; component reusability; and device interface standards. This report elaborates on these key points and proposes research challenges that are to be addressed by a joint effort between academic, industry, and NIH participants.
Jan Lesniak, Junichi Tokuda, Ron Kikinis, Catherina Burghart, and Nobuhiko Hata. 2007. “A device guidance method for organ motion compensation in MRI-guided therapy.” Phys Med Biol, 52, 21, Pp. 6427-38.Abstract
Organ motion compensation in image-guided therapy is an active area of research. However, there has been little research on motion tracking and compensation in magnetic resonance imaging (MRI)-guided therapy. In this paper, we present a method to track a moving organ in MRI and control an active mechanical device for motion compensation. The method proposed is based on MRI navigator echo tracking enhanced by Kalman filtering for noise robustness. We also developed an extrapolation scheme to resolve any discrepancies between tracking and device control sampling rates. The algorithm was tested in a simulation study using a phantom and an active mechanical tool holder. We found that the method is feasible to use in a clinical MRI scanner with sufficient accuracy (0.36 mm to 1.51 mm depending on the range of phantom motion) and is robust to noise. The method proposed may be useful in MRI-guided targeted therapy, such as focused ultrasound therapy for a moving organ.
Yasutoshi Honda and Nobuhiko Hata. 2007. “Dynamic imaging of swallowing in a seated position using open-configuration MRI.” J Magn Reson Imaging, 26, 1, Pp. 172-6.Abstract
PURPOSE: To assess the feasibility of dynamic MRI of swallowing in a seated position using an open-configuration MRI scanner, and to compare its capacity for motion analysis around the pharyngeal wall with that of videofluorography. MATERIALS AND METHODS: Six healthy individuals (four women and two men, mean age = 31.4 +/- 7.5 years) were examined with an open-configuration MRI system using a fast spoiled gradient-recalled echo (SPGR) sequence. Dynamic imaging was performed while the subjects were in a seated position after they swallowed oral contrast medium from a cup. An oral and maxillofacial radiologist measured the motion of six structures: the hyoid bone (HB), larynx (LX), upper oropharynx (UOP), lower oropharynx (LOP), pharyngoesophageal segment (PES) behind the vocal folds, and upper esophagus (ESO). The measured motions were compared with reported values from videofluorography-based observations. RESULTS: Open-configuration MRI depicted the anatomic structures related to swallowing (lip, tongue, soft palate, mandible, pharynx, HB, LX, and PES), and the course of the mylohyoid muscle (MM). The vertical and anteroposterior displacements of these structures did not differ significantly from those measured by videofluorography. CONCLUSION: Dynamic imaging of swallowing using open-configuration MRI provides image information comparable to that obtained from videofluorography.

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