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Radiological Physics and Technology

Junji Shiraishi, Kunio Doi
No abstract text is available yet for this article.
October 11, 2018: Radiological Physics and Technology
Hidetaka Arimura, Mazen Soufi, Kenta Ninomiya, Hidemi Kamezawa, Masahiro Yamada
Computer-aided diagnosis (CAD) is a field that is essentially based on pattern recognition that improves the accuracy of a diagnosis made by a physician who takes into account the computer's "opinion" derived from the quantitative analysis of radiological images. Radiomics is a field based on data science that massively and comprehensively analyzes a large number of medical images to extract a large number of phenotypic features reflecting disease traits, and explores the associations between the features and patients' prognoses for precision medicine...
December 2018: Radiological Physics and Technology
Ying-Hwey Nai, Shoichi Watanuki, Manabu Tashiro, Nobuyuki Okamura, Hiroshi Watabe
With the increasing incidence of dementia worldwide, the frequent use of amyloid and tau positron emission tomography imaging requires low-dose protocols for the differential diagnoses of various neurodegenerative diseases and the monitoring of disease progression. In this study, we investigated the feasibility to reduce the PET dose without a significant loss of quantitative accuracy in 3D dynamic row action maximum likelihood algorithm-reconstructed PET images using [11 C]PIB and [18 F]THK5351. Eighteen cognitively normal young controls, cognitively normal elderly controls, and patients with probable Alzheimer's disease (n = 6 each), were included...
December 2018: Radiological Physics and Technology
Yohei Inaba, Masaaki Nakamura, Koichi Chida, Masayuki Zuguchi
Radiation dose management is important in interventional radiology (IR) procedures, such as percutaneous coronary intervention, to prevent radiation-induced injuries. Therefore, radiation dose should be monitored in real time during IR. This study evaluated the fundamental characteristics of a novel real-time skin dosimeter (RTSD) developed at our institution. In addition, we compared the performance of our new and old radiation sensors and that of a skin dose monitor (SDM), with ion chamber reference values...
December 2018: Radiological Physics and Technology
Chockkalingam Krishnappan, Chandrasekaran Anu Radha, Karunakaran Balaji, Prasanna Kumar Mani, Vendhan Subramani, Velmurugan Thanigaimalai, Madhan Kumar Gunasekaran, Velayudham Ramasubramanian
The purpose of this study was to evaluate the dosimetric variation among six non-beam-matched Varian linacs using different techniques for the same plans. Six non-beam-matched Varian machines, comprising two Clinac iX, two 600 C/D (Unique), and two True Beam Tx photon 6 MV X-ray devices were acquired. Sixty patients with of head and neck (H&N; 30) and pelvic (30) treatment sites were chosen. For all 60 patients, three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated radiotherapy (VMAT) plans were generated for the Clinac iX-1 device; all plans were migrated to the remaining machines, using the eclipse treatment planning system without any modification...
December 2018: Radiological Physics and Technology
Kenta Ninomiya, Hidetaka Arimura, Motoki Sasahara, Yudai Kai, Taka-Aki Hirose, Saiji Ohga
This study aimed to investigate the feasibility of anatomical feature points for the estimation of prostate locations in the Bayesian delineation frameworks for prostate cancer radiotherapy. The relationships between the reference centroids of prostate regions (CPRs) (prostate locations) and anatomical feature points were explored, and the most feasible anatomical feature points were selected based on the smallest location estimation errors of CPRs and the largest Dice's similarity coefficient (DSC) between the reference and extracted prostates...
December 2018: Radiological Physics and Technology
Takahiro Aoyama, Hidetoshi Shimizu, Ikuo Shimizu, Atsushi Teramoto, Naoki Kaneda, Kazuhiko Nakamura, Masaru Nakamura, Takeshi Kodaira
Tumor locations are commonly delineated by referring to magnetic resonance (MR) images. However, MR images have geometric distortions that cannot be completely corrected. This study aimed to investigate quantitatively uncorrectable error [residual error (RE)] with the use of an open-source plugin for scientific image analysis. The RE values were calculated by Fiji, which was enhanced by Image J image processing software. The results obtained with the open-source plugin for scientific image analysis agreed with the results obtained with the commercially available software...
December 2018: Radiological Physics and Technology
Hideo Arai, Masateru Kawakubo, Kenichi Sanui, Hiroshi Nishimura, Toshiaki Kadokami
T1 mapping data are generally acquired in patients' diastolic phase, wherein their myocardium is the thinnest in the cardiac cycle. However, the analysis of the thin myocardium may cause errors in image registrations and settings related to the region of interest. In this study, we validated systolic T1 mapping using the saturation recovery with individualized delay time (SR-IDT) method and compared it with conventional diastolic T1 mapping. Both diastolic and systolic T1 mappings were performed in the mid-ventricular plane in 10 healthy volunteers (35 ± 9 years, 9 males) and 29 consecutive patients with cardiac diseases (68 ± 14 years, 19 males)...
December 2018: Radiological Physics and Technology
Junji Shiraishi, Daisuke Fukuoka, Reimi Iha, Haruka Inada, Rie Tanaka, Takeshi Hara
ROCKIT, which is a receiver-operating characteristic (ROC) curve-fitting software package, was developed by Metz et al. In the early 1990s, it is a very frequently used ROC software throughout the world. In addition to ROCKIT, DBM-MRMC software was developed for multi-reader multi-case analysis of the difference in average area under ROC curves (AUCs). Because this old software cannot run on a PC with Windows 7 or a more recent operating system, we developed new software that employs the same basic algorithms with minor modifications...
December 2018: Radiological Physics and Technology
Takashi Hashido, Shinya Nakasone, Mari Fukao, Seiichi Ota, Shinichi Inoue
This study aimed to compare and assess the compatibility of the bone-structure-based manual and maximization of mutual information (MMI)-algorithm-based automatic image registration using megavoltage cone-beam computed tomography (MV-CBCT) images acquired with an imaging beam line. A total of 1163 MV-CBCT images from 30 prostate cancer patients were retrospectively analyzed. The differences between setup errors in three directions (left-right, LR; superior-inferior, SI; anterior-posterior, AP) of both registration methods were investigated...
December 2018: Radiological Physics and Technology
Farzaneh Allaveisi, Nasrin Amini, Sohrab Sakineh Pour
In the forward intensity-modulated radiotherapy (FIMRT) technique of treatment planning, the isocenter cannot fulfill the requirements of the International Commission on Radiation Units and Measurements (ICRU) reference point. This study aimed to propose dose prescription points to be used in breast and head/neck cancer patients treated using the FIMRT technique. Two-hundred patients with head/neck (n = 100) and breast (n = 100) cancers were selected. Treatment plans involved using the FIMRT technique...
December 2018: Radiological Physics and Technology
Hitomi Nakamura, Junji Morishita, Yoichiro Shimizu, Yongsu Yoon, Yusuke Matsunobu, Shigehiko Katsuragawa, Hidetake Yabuuchi
Similar subtraction imaging is useful for the detection of lung nodules; however, some artifacts on similar subtraction images reduce their utility. The authors attempted to improve the image quality of similar subtraction images by reducing artifacts caused by differences in image contrast and sharpness between two images used for similar subtraction imaging. Image contrast was adjusted using the histogram specification technique. The differences in image sharpness were compensated for using a pixel matching technique...
December 2018: Radiological Physics and Technology
Shin-Ichiro Hayashi, Hiraku Kawamura, Shuji Usui, Takahiro Tominaga
We investigated the effect of magnesium chloride (MgCl2 ) on the nuclear magnetic resonance dose-response of polyacrylamide-type (PAGAT, NIPAM, and VIPET) gel dosimeters containing acrylamide, N-isopropylacrylamide, and N-vinylpyrrolidone as a monomer, respectively. The dose-transverse relaxation rates (1/T2  = R2 ) obtained from magnetic resonance imaging data revealed that a substantial increase in the dose-R2 response occurred as the concentration of MgCl2 in the gel dosimeters increased. The sensitivity of the PAGAT gel with 1...
December 2018: Radiological Physics and Technology
Tomohiro Kajikawa, Noriyuki Kadoya, Kengo Ito, Yoshiki Takayama, Takahito Chiba, Seiji Tomori, Ken Takeda, Keiichi Jingu
The quality of radiotherapy has greatly improved due to the high precision achieved by intensity-modulated radiation therapy (IMRT). Studies have been conducted to increase the quality of planning and reduce the costs associated with planning through automated planning method; however, few studies have used the deep learning method for optimization of planning. The purpose of this study was to propose an automated method based on a convolutional neural network (CNN) for predicting the dosimetric eligibility of patients with prostate cancer undergoing IMRT...
September 2018: Radiological Physics and Technology
Toshiyuki Terunuma, Takeji Sakae
No abstract text is available yet for this article.
September 2018: Radiological Physics and Technology
Shinya Kojima, Hiroyuki Shinohara, Takeyuki Hashimoto, Shigeru Suzuki
In compressed sensing magnetic resonance imaging (CS-MRI), undersampling of k-space is performed to achieve faster imaging. For this process, it is important to acquire data randomly, and an optimal random undersampling pattern is required. However, random undersampling is difficult in two-dimensional (2D) Cartesian sampling. In this study, the effect of random undersampling patterns on image reconstruction was clarified using phantom and in vivo MRI, and a sampling pattern relevant for 2D Cartesian sampling in CS-MRI is suggested...
September 2018: Radiological Physics and Technology
Wataru Jomoto, Masao Tanooka, Tsukasa Wakayama, Takahiro Minamoto, Toru Suzuki, Reiichi Ishikura, Shingo Yamamoto, Noriko Kotoura
The purpose of this study was to compare diffusion tensor imaging using the local look technique and sensitivity encoding for tractography of the periprostatic neurovascular bundle. We compared the surrounding tissues of the prostate in eight healthy volunteers. The results of tractography in terms of the numbers of fibers and the fractional anisotropy map were evaluated. Distortion was evaluated using the dice similarity coefficient between isotropic diffusion images created from diffusion tensor images and T2-weighted images...
September 2018: Radiological Physics and Technology
Akihiro Furuta, Hideo Onishi, Noriyasu Yamaki, Nobuhiro Yada, Hizuru Amijima
We evaluated quantitation accuracy of the specific binding ratio (SBR) and specific uptake ratio (SUR) of dopamine transporter for various correction methods by using a novel three-dimensional striatum digital brain (3D-SDB) phantom comprised of segments containing the striatum, ventricle, brain parenchyma, and skull bone extracted from T2-weighted MR images. A process image was reconstructed by projection data sets with blurring, scatter, and attenuation from 3D-SDB phantom data. A 3D-iterative reconstruction algorithm was used without correction (OSEM), or with scatter (SC), attenuation (AC), AC + SC (ACSC), AC + resolution recovery (RR; ACRR), SC + RR (SCRR), AC + SC + RR (ACSCRR), AC + SC + RR + partial volume (PVC; ACSCRRP), and AC + SC + RR + PVC + ventricle (ACSCRRPV)...
September 2018: Radiological Physics and Technology
Tatsuya Hayashi, Kei Fukuzawa, Hiroshi Kondo, Hiroshi Onodera, Rie Tojo, Shimpei Yano, Tosiaki Miyati, Jun'ichi Kotoku, Takahide Okamoto, Keiko Toyoda, Hiroshi Oba
This phantom study assessed the effect of Gd-EOB-DTPA on T1 bias (difference in T1 between water and fat) of the proton density fat fraction when using magnetic resonance spectroscopy. Phantoms containing varying fat percentages, without and with Gd-EOB-DTPA (precontrast and postcontrast, respectively), were scanned with repetition times ranging from 1000 to 5000 ms. The relationship between the proton density fat fraction at a reference repetition time of 5000 ms and that using different repetition times, was evaluated in the precontrast and postcontrast phantoms using linear regression and Bland-Altman analyses...
September 2018: Radiological Physics and Technology
Chizuru Okamoto, Yoshie Kodera
We acquired a direct-type flat panel detector (FPD) developed for mammography systems and investigated its physical image properties, as its characteristics may affect future mammography in the clinic. The pixel size of the detector is 50 µm, the smallest size used in clinical mammography. Amorphous selenium (a-Se) film is used in direct-type FPDs. Due to its inferior temperature properties, the temperature of the imaging room should be set to approximately 25 °C. A novel a-Se film with superior heat resistance has been developed by the HAMAMATSU photonics KK Electron Tube Division that is suitable for high electric field driving...
September 2018: Radiological Physics and Technology
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