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Radiological Physics and Technology

Kohei Kawasaki, Masanobu Matsumoto, Masayuki Kase, Osamu Nagano, Kyoko Aoyagi, Takahiro Kageyama
In stereotactic radiosurgery for intracranial lesions, optimization of the dose to the at-risk organs is important to avoid neurological complications. We aimed to quantify the dose to the pyramidal tract (PT) and improve treatment planning for gamma knife radiosurgery by combining tractography. Pyramidal tractography images were depicted in 23 patients with lesions adjacent to the PT and fused with stereotactic magnetic resonance images. We regarded the PT as an at-risk organ and performed dose planning. To assess the efficacy of this process, we compared clinical parameters between plans with and without tractography...
August 7, 2017: Radiological Physics and Technology
Kei Fukuzawa, Tatsuya Hayashi, Junji Takahashi, Chiharu Yoshihara, Masakatsu Tano, Jun'ichi Kotoku, Satoshi Saitoh
This study aimed to evaluate (1) the agreement between the true fat fraction (FF) and proton density FF (PDFF) measured using a six-echo modified Dixon (6mDixon) and magnetic resonance spectroscopy (MRS) and (2) the influence of fat on T2* values. The study was performed using phantoms of varying fat and iron content. Point-resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) with single-echo (S) and multiecho (M) (PRESS-S, PRESS-M, STEAM-S, and STEAM-M) were used for MRS. In phantoms without iron, the agreement between the true FF and measured PDFF was tested using Bland-Altman analysis...
August 2, 2017: Radiological Physics and Technology
Yasuhiro Fujiwara, Hitoshi Fujioka, Tomoko Watanabe, Maiko Sekiguchi, Ryuji Murakami
Confirmation of the magnetic resonance (MR) compatibility of implanted medical devices (IMDs) is mandatory before conducting magnetic resonance imaging (MRI) examinations. In Japan, few such confirmation methods are in use, and they are time-consuming. This study aimed to develop a Web-based searchable MR safety information system to confirm IMD compatibility and to evaluate the usefulness of the system. First, MR safety information for intravascular stents and stent grafts sold in Japan was gathered by interviewing 20 manufacturers...
July 31, 2017: Radiological Physics and Technology
Mohd Fahmi Mohd Yusof, Puteri Nor Khatijah Abd Hamid, Abd Aziz Tajuddin, Rokiah Hashim, Sabar Bauk, Norriza Mohd Isa, Muhammad Jamal Md Isa
The aim of this study was to determine the suitability of tannin-added Rhizophora spp. particleboards as phantom materials in the application of low- and high-energy photons. The tannin-added Rhizophora spp. particleboards and density plug phantoms were created with a target density of 1.0 g/cm(3). The elemental composition and effective atomic number of the particleboards were measured using energy dispersive X-ray analysis. The mass attenuation coefficient of the particleboards for low-energy photons were measured using the attenuation of X-ray fluorescence...
July 17, 2017: Radiological Physics and Technology
Kenji Suzuki
The use of machine learning (ML) has been increasing rapidly in the medical imaging field, including computer-aided diagnosis (CAD), radiomics, and medical image analysis. Recently, an ML area called deep learning emerged in the computer vision field and became very popular in many fields. It started from an event in late 2012, when a deep-learning approach based on a convolutional neural network (CNN) won an overwhelming victory in the best-known worldwide computer vision competition, ImageNet Classification...
July 8, 2017: Radiological Physics and Technology
Ying-Hwey Nai, Takayuki Ose, Miho Shidahara, Hiroshi Watabe
Attenuation correction (AC) is required for accurate quantitative evaluation of small animal PET data. Our objective was to compare three AC methods in the small animal Clairvivo-PET scanner. The three AC methods involve applying attenuation coefficient maps generated by simulating a cylindrical map (SAC), segmenting the emission data (ESAC), and segmenting the transmission data (TSAC), imaged using a (137)Cs single-photon source. Investigation was carried out using a 65 mm uniform cylinder and an NEMA NU4 2008 mouse phantom, filled with water or tungsten liquid, to mimic bone...
July 8, 2017: Radiological Physics and Technology
Kazuya Koyama, Takuya Mitsumoto, Takahiro Shiraishi, Keisuke Tsuda, Atsushi Nishiyama, Kazumasa Inoue, Kyosan Yoshikawa, Kazuo Hatano, Kazuo Kubota, Masahiro Fukushi
We aimed to determine the difference in tumor volume associated with the reconstruction model in positron-emission tomography (PET). To reduce the influence of the reconstruction model, we suggested a method to measure the tumor volume using the relative threshold method with a fixed threshold based on peak standardized uptake value (SUVpeak). The efficacy of our method was verified using (18)F-2-fluoro-2-deoxy-D-glucose PET/computed tomography images of 20 patients with lung cancer. The tumor volume was determined using the relative threshold method with a fixed threshold based on the SUVpeak...
July 4, 2017: Radiological Physics and Technology
Aogu Yamaguchi, Tsukasa Sasaki
We aimed to obtain high-stable computed tomography (CT) values for CT angiography (CTA). We verified the optimal use of the new protocol for long-range scanning using a contrast material flow phantom (Ichikawa, CT imaging theory. Igaku syoin Publishing, Tokyo, 8; Awai et al., Am J Roentgenol 186(2):379-385, 1) to obtain high-stable CT values (Fig. 2). We have developed a novel contrast injection method called the stable line imaging protocol (SLIP). This method involved a gradual reduction in the rate of administration of the contrast medium, which was accompanied by simultaneous administration of saline to compensate for the resultant decrease in the rate of administration...
June 1, 2017: Radiological Physics and Technology
Anchali Krisanachinda, Suphot Srimahachota, Kosuke Matsubara
Workers involved in interventional cardiology procedures receive high eye lens doses if radiation protection tools are not properly utilized. Currently, there is no suitable method for routine measurement of eye dose. In Thailand, the eye lens equivalent doses in terms of Hp(3) of the interventional cardiologists, nurses, and radiographers participating in interventional cardiology procedures have been measured at 12 centers since 2015 in the pilot study. The optically stimulated luminescence (OSL) dosimeter was used for measurement of the occupational exposure and the eye lens dose of 42 interventional cardiology personnel at King Chulalongkorn Memorial Hospital as one of the pilot centers...
May 27, 2017: Radiological Physics and Technology
John M Boone, Andrew M Hernandez, J Anthony Seibert
Conventional mammographic dosimetry has been developed over the past 40 years. Prior to the availability of high-resolution three-dimensional breast images, certain assumptions about breast anatomy were required. These assumptions were based on the information evident on two-dimensional mammograms; they included assumptions of thick skin, a uniform mixture of glandular and adipose tissue, and a median breast density of 50%. Recently, the availability of high-resolution breast CT studies has provided more accurate data about breast anatomy, and this, in turn, has provided the opportunity to update mammographic dosimetry...
June 1, 2017: Radiological Physics and Technology
Hiroshi Watanabe, Kimiya Noto, Tomokazu Shohji, Yasuyoshi Ogawa, Toshioh Fujibuchi, Ichiro Yamaguchi, Hitoshi Hiraki, Tetsuo Kida, Kazutoshi Sasanuma, Yasushi Katsunuma, Takurou Nakano, Genki Horitsugi, Makoto Hosono
The goal of this study is to develop a more appropriate shielding calculation method for computed tomography (CT) in comparison with the Japanese conventional (JC) method and the National Council on Radiation Protection and Measurements (NCRP)-dose length product (DLP) method. Scattered dose distributions were measured in a CT room with 18 scanners (16 scanners in the case of the JC method) for one week during routine clinical use. The radiation doses were calculated for the same period using the JC and NCRP-DLP methods...
June 2017: Radiological Physics and Technology
Yuta Matsunaga, Ai Kawaguchi, Masanao Kobayashi, Shigetaka Suzuki, Shoichi Suzuki, Koichi Chida
The purposes of this study were (1) to compare the radiation doses for 320- and 80-row fetal-computed tomography (CT), estimated using thermoluminescent dosimeters (TLDs) and the ImPACT Calculator (hereinafter referred to as the "CT dosimetry software"), for a woman in her late pregnancy and her fetus and (2) to estimate the overlapped fetal radiation dose from a 320-row CT examination using two different estimation methods of the CT dosimetry software. The direct TLD data in the present study were obtained from a previous study...
June 2017: Radiological Physics and Technology
Keita Takahashi, Shinichi Awamoto, Shinya Takarabe, Kazuhisa Ogawa, Yasuhiko Nakamura
The objective of this work was to evaluate the maximum luminance (L max) level of medical liquid crystal displays (LCDs) as a function of backlight hours (BLH) annually. The L max values for 249 2-megapixel color LCDs (RadiForce RX210, EIZO Corporation) were measured in February 2014, 2015, and 2016. Four near-range luminance meters and the built-in type luminance meters, each with an LCD, were used for the measurements. The average and standard deviation (SD) of BLH measured in 2014 was 15,371 ± 8219 h...
May 2, 2017: Radiological Physics and Technology
Norio Hayashi, Akio Ogura, Toshio Tsuchihashi, Daisuke Takahashi, Tsuyoshi Matsuda, Shinya Seino, Tsukasa Doi
The purpose of this study was to evaluate the magnetization and demagnetization of magnetic dental attachments in a 3.0-T magnetic resonance imaging (MRI) scanner. A high-field-strength (3.0 T) MRI scanner (Achieva 3.0 T, Philips, Amsterdam, Netherlands) was used. Magnetic flux leakage was measured using a gaussmeter. To evaluate the magnetization and demagnetization of the magnetic assemblies and keepers caused by the moving in and out of the MRI scanner, the magnetic force of the attachments was measured before and after the table was moved in and out...
April 27, 2017: Radiological Physics and Technology
Yoichiro Shimizu, Junji Morishita
This paper describes the development of an automated method of extraction of biological fingerprints (BFs), including detection of image orientation in chest radiographs. The image orientation of a target image was recognized and modified by examination of normalized cross-correlation values between a target image and averaged male and female images with correct image orientation. Templates of BFs were extracted from averaged images. Then, each BF in the target image was extracted from locations that showed the highest cross-correlation value between the template of BF in the averaged image and the corresponding BF in the target image...
April 27, 2017: Radiological Physics and Technology
Shiro Nishiyama, Satoru Ishibashi, Ryo Takahashi, Hidenobu Tachibana
An add-on micro multi-leaf collimator (mMLC) is used for stereotactic radiosurgery (SRS) and brain stereotactic radiotherapy (SRT), in which rotational radiotherapy may make more complex and time-consuming. We performed a retrospective study of an independent dose calculation verification for brain SRS and SRT in two institutions to show the accuracy of the verification system and propose a tolerance value for the verification. Several comparisons of static plans and patients' plans were conducted using a phantom measurement, and patients' plans using the patients' own computed tomography image...
April 19, 2017: Radiological Physics and Technology
Sayed Ahmad Zikri Bin Sayed Aluwee, Xiangrong Zhou, Hiroki Kato, Hiroshi Makino, Chisako Muramatsu, Takeshi Hara, Masayuki Matsuo, Hiroshi Fujita
We propose an approach to supporting pre-surgical planning for the uterus by integrating medical image analysis and physical model generation based on 3D printing. With our method, we first segment the patient-specific anatomy and lesions of the uterus on MR images; then, we create a 3D physical model, an exact replica of the patient's uterus in terms of size and softness, with transparency for easy observation of the internal structures of the uterus. In our experiments, we created pre-surgical models of hysterectomy for five patients who had been diagnosed to have uterine endometrial cancer...
April 12, 2017: Radiological Physics and Technology
Shunichi Motegi, Takehiro Shimada, Norio Hayashi, Hiroyuki Nagase, Ayako Taketomi-Takahashi, Yoshito Tsushima
We propose a practical method for setting the optimal inversion times (TI) for double inversion recovery (DIR) sequences. Our method used the measurement of signal intensity (SI) from real images to set the optimal TI for white-matter (WM) and gray-matter (GM)-attenuated inversion recovery (WAIR and GAIR, respectively) images. 3D-DIR images of healthy volunteers were obtained on 1.5- and 3.0-T magnetic resonance (MR) scanners and the SIs of GM, WM, and cerebrospinal fluid (CSF) were evaluated on real images...
April 9, 2017: Radiological Physics and Technology
Akio Ogura, Aoi Kamakura, Youhei Kaneko, Tomoya Kitaoka, Norio Hayashi, Anna Taniguchi
Medical images are increasingly being rendered as digital images that are displayed on a monitor to provide diagnoses. However, these images are often rendered in grayscale. In this context, we compare the detectability of low-contrast signals between digital grayscale images and color-scale images. Low-contrast phantom images were rendered with the use of five color tables (gray, blue, red, yellow, and green). The 32 acquired images sorted in random order were evaluated by nine observers, and their observations were subjected to receiver operating characteristic analysis...
March 27, 2017: Radiological Physics and Technology
Carina Marques Coelho, Raquel Calçada, Sofia Rodrigues, Juan Antonio Barragán, Ana Cravo Sá, Ana Paula Macedo, Maria de Fátima Monsanto
This study aimed to assess the administered dose based on portal imaging in craniospinal pediatric irradiation by evaluating cases in which portal images did or did not account for the total administered dose. We also intended to calculate the mean increase in total administered dose. Data were collected from General University Hospital Gregorio Marañón; we evaluated the total dose administered, total dose planned, number of portal images per treatment and corresponding monitor units of two different groups: one in which the dose from portal images is deducted from the total administered dose (D), and another in which it was not (N)...
March 21, 2017: Radiological Physics and Technology
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