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1. Concomitant Use of Fine-Needle Biopsy and Large-Needle Biopsy in the Diagnosis of Thyroid Nodules
Mizukami, Yuji ; Michigishi, Takatoshi ; Hisatomi, Motoji ; Noguchi, Masakuni ; Takemura, Akihiro ; Ichikawa, Katsuhiro
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Ichikawa, Katsuhiro ; Nishi, Yoshikazu ; Hayashi, Shigeo ; Hasegawa, Mikio ; Kodera, Yoshie
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We have developed and reported a super-high resolution liquid crystal display (SHR-LCD) using a new resolution enhancement technology of the independent sub-pixel driving (ISD) that utilizes three sub-pixels in each pixel element.
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This technology realizes the three-times resolution enhancement of monochrome LCDs, and improves the depiction ability of detailed shape such as micro-calcifications of a mammography and bone structures. Furthermore, the ISD technology brings not only resolution enhancement but also noise reduction effect by the high-resolution data sampling in displaying the clinical images. In this study, we examined the efficacy of the newly developed LCDs from the noise power spectrum measurement (NPS), the perceptual comparison of the phantom images and the clinical images. A 15 mega-pixel (MP)SHR-LCD out of a 5MP LCD and a 6MP SHR-LCD out of a 2MP LCD were used for the measurement and the evaluation. In the NPS measurements, the noise of all the SHR-LCDs was improved obviously. The improvement degree of the NPS varied according to the sub-sampling ratio of the data sampling implemented during the image displaying, and the 6MP LCD showed higher improvement. In the perceptual evaluation of the quality-control phantom images and the low-contrast images of the micro-calcifications of the mammography, all the SHR-LCDs provided higher performance than the conventional LCDs. These results proved that the SHR-LCDs using the ISD technology had the excellent ability to display the high-resolution clinical images.
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Ichikawa, Katsuhiro ; Kawashima, Hiroko ; Kimura, Naohiro ; Hasegawa, Mikio
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金沢大学医薬保健研究域保健学系<br />We have developed and reported super-high resolution liquid crystal displays (SHR-LCDs) using a new
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resolution enhancement technology of the independent sub-pixel driving (ISD) that utilizes three sub-pixels contained in each pixel element. This technology realizes the three-times resolution enhancement of monochrome LCDs. A 15 mega-pixel (MP) SHR-LCD out of a 5MP LCD and a 9MP SHR-LCD out of a 3MP LCD, for example, are realized by this technology, which improves the depiction ability of detailed image shapes such as micro-calcifications of a mammography. Furthermore, the ISD technology brings not only resolution enhancement but also noise reduction effect by the high-frequency data sampling in displaying the clinical images. In this study, we have investigated the clinical efficacy of the SHR-LCDs by means of phantom observation studies and blind observer comparison studies using clinical mammography images performed by radiologists. We used a conventional 5MP LCD for a comparison of a 15MP SHR-LCD and a 9MP SHR-LCD to evaluate their efficacy. From the results of the studies, it was indicated that the SHR-LCDs using the ISD technology had the excellent ability to display the high-resolution digital mammography images. © 2008 Springer-Verlag Berlin Heidelberg.
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Ichikawa, Katsuhiro ; Kodera, Yoshie ; Nishi, Yoshikazu ; Hayashi, Sigeo ; Hasegawa, Mikio
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金沢大学大学院医学系研究科量子医療技術学<br />A new resolution enhancement technology that used independent sub-pixel driving method was dev
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eloped for medical monochrome liquid crystal displays (LCDs). Each pixel of monochrome LCDs, which employ color liquid crystal panels with color filters removed, consists of three sub-pixels. In the new LCD system implemented with this technology, sub-pixel intensities were modulated according to detailed image information, and consequently resolution was enhanced three times. In addition, combined with adequate resolution improvement by image data processing, horizontal and vertical resolution properties were balanced. Thus the new technology realized 9 mega-pixels (MP) ultra-high resolution out of 3MP LCD. Physical measurements and perceptual evaluations proved that the achieved 9MP (through our new technology) was appropriate and efficient to depict finer anatomical structures such as micro calcifications in mammography.
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5. Bulk motion-independent analyses of water diffusion changes in the brain during the cardiac cycle
Nakamura, Tomoya ; Miyati, Tosiaki ; Kasai, Harumasa ; Ohno, Naoki ; Yamada, Masato ; Mase, Mitsuhito ; Hara, Masaki ; Shibamoto, Yuta ; Suzuki, Yuriko ; Ichikawa, Katsuhiro
Abstract:
金沢大学医薬保健研究域保健学系<br />We evaluated dynamic changes in water diffusion in the brain during the cardiac cycle by using cine
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diffusion MRI. On a 1.5-T MRI, ECG-triggered single-shot diffusion echo planar imaging was used with sensitivity encoding, halfscan, and rectangular field of view techniques for minimizing bulk motion effects such as brain pulsation, with a data-sampling window of 3 ms. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the white matter zone were determined in ten healthy volunteers and then compared with the intracranial volume change (ICVC) revealed by phase-contrast cine MRI during the cardiac cycle. In addition, a frequency analysis of these waveforms was performed. ADC and FA values changed significantly during the cardiac cycle, despite minimizing the effect of bulk motion, i.e., independent of bulk motion. The ADC was synchronized with the ICVC during the cardiac cycle. A significant positive correlation was noted among their amplitudes. Analysis of the dynamic change of water diffusion by use of cine diffusion MRI facilitates the assessment of intracranial conditions. © 2009 Japanese Society of Radiological Technology and Japan Society of Medical Physics.
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Tanaka, Rie ; Ichikawa, Katsuhiro ; Mori, Shinichiro ; Dobashi, Suguru ; Kumagai, Motoki ; Kawashima, Hiroki ; Minohara, Shinichi ; Sanada, Sigeru
Abstract:
金沢大学医薬保健研究域保健学系<br />Real-time tumor tracking in external radiotherapy can be achieved by diagnostic (kV) X-ray imaging
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with a dynamic flat-panel detector (FPD). The purpose of this study was to address image lag in target tracking and its influence on the accuracy of tumor tracking. Fluoroscopic images were obtained using a direct type of dynamic FPD. Image lag properties were measured without test devices according to IEC 62220-1. Modulation transfer function (MTF) and profile curves were measured on the edges of a moving tungsten plate at movement rate of 10 and 20 mm/s, covering lung tumor movement of normal breathing. A lung tumor and metal sphere with blurred edge due to image lag was simulated using the results and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the image lag for the first frame after X-ray cutoff was 2.0% and decreased to less than 0.1% in the fifth frame. In the measurement of profile curves on the edges of static and moving tungsten material plates, the effect of image lag was seen as blurred edges of the plate. The blurred edges of a moving target were indicated as reduction of MTF. However, the target could be traced within an error of ± 5 mm. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation.
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| 7.
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Tanaka, Rie ; Ichikawa, Katsuhiro ; Mori, Shinichiro ; Sanada, Sigeru
Abstract:
Real-time tumor tracking in external radiotherapy can be achieved by diagnostic (kV) X-ray imaging with a dynamic flat-p
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anel detector (FPD). It is important to keep the patient dose as low as possible while maintaining tracking accuracy. A simulation approach would be helpful to optimize the imaging conditions. This study was performed to develop a computer simulation platform based on a noise property of the imaging system for the evaluation of tracking accuracy at any noise level. Flat-field images were obtained using a direct-type dynamic FPD, and noise power spectrum (NPS) analysis was performed. The relationship between incident quantum number and pixel value was addressed, and a conversion function was created. The pixel values were converted into a map of quantum number using the conversion function, and the map was then input into the random number generator to simulate image noise. Simulation images were provided at different noise levels by changing the incident quantum numbers. Subsequently, an implanted marker was tracked automatically and the maximum tracking errors were calculated at different noise levels. The results indicated that the maximum tracking error increased with decreasing incident quantum number in flat-field images with an implanted marker. In addition, the range of errors increased with decreasing incident quantum number. The present method could be used to determine the relationship between image noise and tracking accuracy. The results indicated that the simulation approach would aid in determining exposure dose conditions according to the necessary tracking accuracy. © The Author 2012. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology.
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| 8.
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西丸, 英治 ; 市川, 勝弘 ; 藤岡, 知加子 ; 木口, 雅夫 ; 石風呂, 実 ; 鈴木, 正行 ; Nishimaru, Eiji ; Ichikawa, Katsuhiro ; Fujioka, Chikako ; Kiguchi, Masao ; Ishifuro, Minoru ; Suzuki, Masayuki
Abstract:
Reference lines of brain computed tomography (CT) is orbitomeatal (OM) line that runs through the external canthus and the center of the external auditory meatus. However, because it is difficult to identify OM line on the scout image
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which is 2-dimensional X-ray image, OM line is usually set by radiological technologists subjectively. The purpose of our study is to propose a method which detects the scan angle and the scan range used on the scout images automatically. The algorithm in our proposed method is based on a two-dimensional post-processing that is the method of Hough transformation conversion for detecting the scan angle and the Cross-correlation technique for the scan range. Our proposed method was tested using the scout images of 30 clinical patients' data by visual evaluation of four radiological technologists. Four radiological technologists evaluated the results of the clinical cases and 28 cases (93%) of CT examinations with using our method were acceptable. We confirmed it has the potential to improve the consistency in scan planning of brain CT, because the proposed method detects almost accurately the scan angle and the scan range in clinical cases. In conclusion, it is possible to obtain reproducible slice level images.
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| 9.
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Tanaka, Rie ; Ichikawa, Katsuhiro ; Matsubara, Kosuke ; Kawashima, Hiroki
Abstract:
Reduction of exposure dose and improvement in image quality can be expected to result from advances in the performance o
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f imaging detectors. We propose a computerized method for determining optimized imaging conditions by use of simulated images. This study was performed to develop a prototype system for image noise and to ensure consistency between the resulting images and actual images. An RQA5 X-ray spectrum was used for determination of input-output characteristics of a flat-panel detector (FPD). The number of incident quantum to the detector per pixel (counts/pixel) was calculated according to the pixel size of the detector and the quantum number in RQA5 determined in IEC6220-1. The relationship among tube current-time product (mAs), exposure dose (C/kg) at the detector surface, the number of incident quanta (counts/pixel), and pixel values measured on the images was addressed, and a conversion function was then created. The images obtained by the FPD was converted into a map of incident quantum numbers and input into random-value generator to simulate image noise. In addition, graphic user interface was developed to observe images with changing image noise and exposure dose levels, which have trade-off relationship. Simulation images provided at different noise levels were compared with actual images obtained by the FPD system. The results indicated that image noise was simulated properly both in objective and subjective evaluation. The present system could allow us to determine necessary dose from image quality and also to estimate image quality from any exposure dose. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
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| 10.
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Tanaka, Rie ; Ichikawa, Katsuhiro ; Matsubara, Kosuke ; Kawashima, Hiroki
Abstract:
Reduction of exposure dose and improvement in image quality can be expected to result from advances in the performance o
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f imaging detectors. A number of researchers have reported on methods for simulating reduced dose images. The simplest method provides reduced dose images by adding white Gaussian noise with a certain standard deviation to the original image. Our aim in this study was to develop and validate a system with a graphic user interface for simulating reduced dose images by a simple method. Here, we describe a technical approach with the use of a flat-panel detector system, and we validated the simulation performance in reducing the dose objectively and subjectively. In addition, the technical limitations and possible solutions to the simple method are suggested based on the validation results presented in this paper. © 2012 Japanese Society of Radiological Technology and Japan Society of Medical Physics.<br />発行後1年より全文公開.
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