Publications

2005
Nobuhiko Hata, Yoshihiro Muragaki, Takashi Inomata, Takashi Maruyama, Hiroshi Iseki, Tomokatsu Hori, and Takeyoshi Dohi. 2005. “Intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery for tumor resection rate control.” Acad Radiol, 12, 1, Pp. 116-22.Abstract
RATIONALE AND OBJECTIVES: Gross-total surgery under intraoperative magnetic resonance imaging (MRI) is a promising method of glioma removal. The purpose of this article is intraoperative measurement of resected tumor volume in MRI-guided glioma surgery using semiautomatic image segmentation to unbiased resection rate control. MATERIALS AND METHODS: A newly developed software program based on a fuzzy connectedness (FC) segmentation algorithm was used to achieve fast and semiautomatic tumor segmentation and tumor volume measurement. The program was validated by retrospective study of eight glioma cases and then applied to seven glioma cases. All clinical cases underwent actual MRI-guided surgery using 0.3-T open magnets. RESULTS: The volume of the tumor before resection ranged from 10.1 to 206.7 mL. A comparison of the results of manual segmentation with those of the semiautomatic FC-based segmentation gave an average dice similarity coefficient of 0.80 and an average match of 76%. Volume measurement combined with a developed software program enabled quantitative monitoring of tumor removal, which was critical in the near-total resection of glioma in MRI-guided surgery. CONCLUSION: The FC-based tumor segmentation method can be used for intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery using 0.3-T open magnets. This method is useful for objective resection rate monitoring, which may ultimately minimize the amount of residual tumor in glioma surgery.
Steven J Haker, Robert V Mulkern, Joseph R Roebuck, Agnieska Szot Barnes, Simon DiMaio, Nobuhiko Hata, and Clare MC Tempany. 2005. “Magnetic resonance-guided prostate interventions.” Top Magn Reson Imaging, 16, 5, Pp. 355-68.Abstract
We review our experience using an open 0.5-T magnetic resonance (MR) interventional unit to guide procedures in the prostate. This system allows access to the patient and real-time MR imaging simultaneously and has made it possible to perform prostate biopsy and brachytherapy under MR guidance. We review MR imaging of the prostate and its use in targeted therapy, and describe our use of image processing methods such as image registration to further facilitate precise targeting. We describe current developments with a robot assist system being developed to aid radioactive seed placement.
Nobuhiko Hata, Toru Wada, Kyoko Kashima, Yoshiyuki Okada, Nobuya Unno, Michihiro Kitagawa, and Toshio Chiba. 2005. “Non-gated fetal MRI of umbilical blood flow in an acardiac twin.” Pediatr Radiol, 35, 8, Pp. 826-9.Abstract
Currently, the standard method of diagnosis of twin reversed arterial perfusion (TRAP) sequence is ultrasound imaging. The use of MRI for flow visualization may be a useful adjunct to US imaging for assessing the presence of retrograde blood flow in the acardiac fetus and/or umbilical artery. The technical challenge in fetal MRI flow imaging, however, is that fetal electrocardiogram (ECG) monitoring required for flow imaging is currently unavailable in the MRI scanner. A non-gated MRI flow imaging technique that requires no ECG monitoring was developed using the t-test to detect blood flow in 20 slices of phase-contrast MRI images randomly scanned at the same location over multiple cardiac cycles. A feasibility study was performed in a 24-week acardiac twin that showed no umbilical flow sonographically. Non-gated MRI flow images clearly indicated the presence of blood flow in the umbilical artery to the acardiac twin; however, there was no blood flow beyond the abdomen. This study leads us to conjecture that non-gated MRI flow imaging is sensitive in detecting low-range blood flow velocity and can be an adjunct to Doppler US imaging.
Nobuhiko Hata. 2005. “[Present status and problems in the new system of postgraduate psychiatry training in the psychiatry department of Nagasaki University Hospital].” Seishin Shinkeigaku Zasshi, 107, 8, Pp. 852-7.
Hongen Liao, Makoto Iwahara, Takefumi Koike, Nobuhiko Hata, Ichiro Sakuma, and Takeyoshi Dohi. 2005. “Scalable high-resolution integral videography autostereoscopic display with a seamless multiprojection system.” Appl Opt, 44, 3, Pp. 305-15.Abstract
We propose a scalable high-resolution autostereoscopic display that uses integral videography (IV) and a seamless multiprojection system. IV is an animated extension of integral photography (IP). Although IP and IV are ideal ways to display three-dimensional images, their spatial viewing resolution needs improvement; the pixel pitch of the display and the lens pitch are the main factors affecting IV image quality. We improved the quality by increasing the number and density of the pixels. Using multiple projectors, we create a scalable high-resolution image and project it onto a small screen using long-focal-length projection optics. To generate seamless IV images, we developed an image calibration method for geometric correction and color modulation. We also fabricated a lens array especially for the display device. Experiments were conducted with nine XGA projectors and nine PCs for parallel image rendering and displaying. A total of 2868 x 2150 pixels were displayed on a 241 mm x 181 mm (302.4 dots/in.) rear-projection screen. The lens pitch was 1.016 mm, corresponding to 12 pixels of the projected image. Measurement of the geometric accuracy of the reproduced IV images demonstrated that the spatial resolution of the display system matched that of the theoretical analysis.
Hongen Liao, Makoto Iwahara, Yoichi Katayama, Nobuhiko Hata, and Takeyoshi Dohi. 2005. “Three-dimensional display with a long viewing distance by use of integral photography.” Opt Lett, 30, 6, Pp. 613-5.Abstract
We developed a technique of three-dimensional (3-D) display for distant viewing of a 3-D image without the need for special glasses. The photobased integral photography (IP) method allows precise 3-D images to be displayed at long viewing distances without any influence from deviated or distorted lenses in a lens array. We calculate elemental images from a referential viewing area for each lens and project the corresponding result images to photographic film through each lens. We succeed in creating an image display that appears to have three dimensionality even when viewed from a distance, with an image depth of 5.7 m or more in front of the display and 3.5 m or more behind the display. To the best of our knowledge, the long-distance IP display presented here is technically unique because it is the first report of generation of an image with such a long viewing distance.
2004
Hongen Liao, Makoto Iwahara, Nobuhiko Hata, and Takeyoshi Dohi. 2004. “High-quality integral videography using a multiprojector.” Opt Express, 12, 6, Pp. 1067-76.Abstract
Integral videography (IV) is an animated extension of integral photography. Despite IV's many advantages, the quality of its spatial images has thus far been poor; the pixel pitch of the display and the lens pitch are considered to be the main factors affecting the IV image format. Our solution for increasing pixel density is to use multiple projectors to create a high-resolution image and project the resultant image onto a small screen by using long-zoom-lens projection optics. We manufactured a lens array for the display device, and here we present experimental results on using two SXGA projectors. The pixel pitch and lens pitch of the new display are 85 mum and 1.016 mm, respectively. The multiprojector IV display device has a spatial resolution of approximately 1, 2, and 3 mm for image depths of 10, 35, and 60 mm, respectively, in front of and behind the lens array.
Junichi Tokuda, Shigehiro Morikawa, Takeyoshi Dohi, and Nobuhiko Hata. 2004. “Motion tracking in MR-guided liver therapy by using navigator echoes and projection profile matching.” Acad Radiol, 11, 1, Pp. 111-20.Abstract
RATIONALE AND OBJECTIVES: Image registration in magnetic resonance (MR) image-guided liver therapy enhances surgical guidance by fusing preoperative multimodality images with intraoperative images, or by fusing intramodality images to correlate serial intraoperative images to monitor the effect of therapy. The objective of this paper is to describe the application of navigator echo and projection profile matching to fast two-dimensional image registration for MR-guided liver therapy. MATERIALS AND METHODS: We obtain navigator echoes along the read-out and phase-encoding directions by using modified gradient echo imaging. This registration is made possible by masking out the liver profile from the image and performing profile matching with cross-correlation or mutual information as similarity measures. The set of experiments include a phantom study with a 2.0-T experimental MR scanner, and a volunteer and a clinical study with a 0.5-T open-configuration MR scanner, and these evaluate the accuracy and effectiveness of this method for liver therapy. RESULTS: Both the phantom and volunteer study indicate that this method can perform registration in 34 ms with root-mean-square error of 1.6 mm when the given misalignment of a liver is 30 mm. The clinical studies demonstrate that the method can track liver motion of up to approximately 40 mm. Matching profiles with cross-correlation information perform better than with mutual information in terms of robustness and speed. CONCLUSION: The proposed image registration method has potential clinical impact on and advantages for MR-guided liver therapy.
Hongen Liao, Nobuhiko Hata, Susumu Nakajima, Makoto Iwahara, Ichiro Sakuma, and Takeyoshi Dohi. 2004. “Surgical navigation by autostereoscopic image overlay of integral videography.” IEEE Trans Inf Technol Biomed, 8, 2, Pp. 114-21.Abstract
This paper describes an autostereoscopic image overlay technique that is integrated into a surgical navigation system to superimpose a real three-dimensional (3-D) image onto the patient via a half-silvered mirror. The images are created by employing a modified version of integral videography (IV), which is an animated extension of integral photography. IV records and reproduces 3-D images using a microconvex lens array and flat display; it can display geometrically accurate 3-D autostereoscopic images and reproduce motion parallax without the need for special devices. The use of semitransparent display devices makes it appear that the 3-D image is inside the patient's body. This is the first report of applying an autostereoscopic display with an image overlay system in surgical navigation. Experiments demonstrated that the fast IV rendering technique and patient-image registration method produce an average registration accuracy of 1.13 mm. Experiments using a target in phantom agar showed that the system can guide a needle toward a target with an average error of 2.6 mm. Improvement in the quality of the IV display will make this system practical and its use will increase surgical accuracy and reduce invasiveness.
2003
Shigehiro Morikawa, Toshiro Inubushi, Yoshimasa Kurumi, Shigeyuki Naka, Koichiro Sato, Koichi Demura, Tohru Tani, Hasnine A Haque, Junichi Tokuda, and Nobuhiko Hata. 2003. “Advanced computer assistance for magnetic resonance-guided microwave thermocoagulation of liver tumors.” Acad Radiol, 10, 12, Pp. 1442-9.Abstract
RATIONALE AND OBJECTIVES: The purpose of this study was to utilize computer assistance effectively for both easy and accurate magnetic resonance (MR) image-guided microwave thermocoagulation therapy of liver tumors. MATERIALS AND METHODS: An open configuration MR scanner and a microwave coagulator at 2.45 GHz were used. Navigation software, a 3D Slicer, was customized to combine fluoroscopic MR images and preoperative MR images for the navigation. New functions to display MR temperature maps with simple parameter setting, and to record and display the coagulated areas by multiple microwave ablations in the 3-dimensional space (footprinting), were also introduced into the software. The VGA signal of the computer display was directly transferred to the surgeon's monitor. RESULTS: The customized software could be used for both accurate image navigation and convenient and easy temperature monitoring. Because repeated punctures and ablations are usually required in this procedure, the footprinting function made targeting of the tumors both easy and accurate and was quite effective in achieving the necessary and sufficient treatment. Furthermore, clear display on the surgeon's monitor, which was obtained by direct transfer of the VGA signal, enabled precise image navigation. CONCLUSION: The newly developed computer assistance was quite useful and helpful for this MR-guided procedure.
Shigehiro Morikawa, Toshiro Inubushi, Yoshimasa Kurumi, Shigeyuki Naka, Koichiro Sato, Tohru Tani, Hasnine A Haque, Jun-ichi Tokuda, and Nobuhiko Hata. 2003. “New assistive devices for MR-guided microwave thermocoagulation of liver tumors.” Acad Radiol, 10, 2, Pp. 180-8.Abstract
RATIONALE AND OBJECTIVES: The purpose of this study was to develop and test new assistive devices to aid in the performance of safe, easy, and accurate microwave thermocoagulation therapy guided by magnetic resonance (MR) imaging. MATERIALS AND METHODS: An open-configuration MR imager with an optical tracking system for image plane control and a microwave coagulator operating at 2.45 GHz were used. Liver tumors were percutaneously punctured under the guidance of MR images and ablated. Handpiece adapters were then prepared for the optical tracking system. An MR-compatible endoscopic system also was used. Navigation software was installed and customized. These devices were combined to provide near-real-time MR image-guided navigation during thermocoagulation therapy for liver tumors. RESULTS: The handpiece adapters improved the flexibility of approaches for percutaneous puncture of tumors. The MR-compatible endoscope was used as a thoracoscope, and tumors just below the diaphragm were safely and easily punctured through the diaphragm. The customized navigation software displayed near-real-time MR images together with two reformatted images (on the same plane and on a perpendicular plane) from the registered high-resolution three-dimensional data, enabling accurate MR imaging navigation. CONCLUSION: These new assistive devices made it easier to perform safe, easy, and accurate MR-guided thermocoagulation therapy of liver tumors.
Nobuhiko Hata, Toru Wada, Toshio Chiba, Yoshiyuki Tsutsumi, Yoshiyuki Okada, and Takeyoshi Dohi. 2003. “Three-dimensional volume rendering of fetal MR images for the diagnosis of congenital cystic adenomatoid malformation.” Acad Radiol, 10, 3, Pp. 309-12.Abstract
RATIONALE AND OBJECTIVES: Great expertise is necessary to mentally compile a series of individual two-dimensional image sections into a three-dimensional (3D) composite view that can aid in differential diagnosis. The purpose of this study was to test 3D volume-rendering techniques for differentiating congenital cystic adenomatoid malformation from congenital diaphragmatic hernia. MATERIALS AND METHODS: The authors acquired T2-weighted magnetic resonance (MR) images of a 27-week fetus in the sagittal plane and then applied the 3D volume-rendering method to the MR image data sets to obtain a composite 3D image. RESULTS: It was unclear on the MR images whether the intestines were situated above or below the diaphragm. The composite image showed that the intestines were not herniated into the chest, and this facilitated a diagnosis of congenital cystic adenomatoid malformation rather than congenital diaphragmatic hernia. CONCLUSION: The 3D volume-rendering techniques aided in the assessment of fetal organ structure and could be applied also to preoperative simulation and planning of fetal surgery.
2002
Masanori Hirose, Aditya Bharatha, Nobuhiko Hata, Kelly H Zou, Simon K Warfield, Robert A Cormack, Anthony D'Amico, Ron Kikinis, Ferenc A Jolesz, and Clare MC Tempany. 2002. “Quantitative MR imaging assessment of prostate gland deformation before and during MR imaging-guided brachytherapy.” Acad Radiol, 9, 8, Pp. 906-12.Abstract
RATIONALE AND OBJECTIVES: The authors performed this study to document the deformations that occur between pretreatment magnetic resonance (MR) imaging and intraoperative MR imaging during brachytherapy. MATERIALS AND METHODS: MR images obtained at 1.5 and 0.5 T in 10 patients with prostate cancer were analyzed for changes in the shape and substructure of the prostate. Three-dimensional models of the prostate were obtained. The authors measured anteroposterior dimension; total gland, peripheral zone, and central gland volumes; transverse dimension; and superoinferior height. RESULTS: Gland deformations were seen at visual inspection of the three-dimensional models. The anteroposterior dimension of the total gland, central gland, and peripheral zone increased from 1.5- to 0.5-T imaging (median dimension, 4.9, 1.5, and 1.8 mm, respectively), and the increase was greatest in the peripheral zone (P < .05, all comparisons). There was a decrease in the transverse dimension from 1.5- to 0.5-T imaging (median, 4.5 mm; P < .005). The total gland volume and the superoinferior height did not show a statistically significant change. CONCLUSION: There were significant deformations in the shape of the prostate, especially in the peripheral zone, between the two imaging studies. The likely causes of the shape change are differences in rectal filling (endorectal coil used in 1.5-T studies vs obturator in 0.5-T studies) and/or changes in patient position (supine vs lithotomy). These findings suggest that pretreatment images alone may not be reliable for accurate therapy planning. It may be useful to integrate pre-and intraoperative data.

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