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Radiological Physics and Technology

Yuji Nakaguchi, Yuya Nakamura, Yohei Yotsuji
The Mobius3D (M3D) system (Mobius Medical Systems) is a second-check dosimetry system. We investigated the dose calculation accuracy of this system using heterogeneous phantoms with reference beam data provided by the manufacturer using simple and patient plans. We compared the dose distributions between M3D and the treatment planning system, as well as the measurements in solid water phantoms, heterogeneous phantoms, and patient plans for Varian and Elekta accelerators. The M3D results agreed well with the measurements in the solid water phantoms for the simple plans...
January 25, 2019: Radiological Physics and Technology
Yasuhiro Fujiwara, Yumi Inoue, Masayuki Kanamoto, Shota Ishida, Toshiki Adachi, Hirohiko Kimura
Synthetic magnetic resonance imaging (MRI) allows the production of images with any contrast from a single scan after quantification. The combined T2 -weighted image (T2WI) and fluid-attenuated inversion recovery (FLAIR) image is expected to have an improved contrast between the normal-appearing white matter (WM) and WM lesion (WML). The purpose of this study was to determine whether optimal T2 contrast-weighted images (SyFLAIR3 ) comprising the combined T2WI and FLAIR image generated using synthetic MRI could improve contrast in the WM region...
January 21, 2019: Radiological Physics and Technology
Masatoshi Saito
For accurate tissue-inhomogeneity correction in radiotherapy treatment planning, the author previously proposed a conversion of the energy-subtracted computed tomography (CT) number to electron density (ΔHU-ρe conversion). The purpose of the present study was to provide a method for investigating the accuracy of a photon-counting detector (PCD) used in the ΔHU-ρe conversion by performing dual-energy CT image simulations of a PCD system with two energy bins. To optimize the tube voltage and threshold energy, the image noise and errors in ρe calibration were evaluated using three types of virtual phantoms: a 35-cm-diameter pure water phantom, 33-cm-diameter solid water surrogate phantom equipped with 16 inserts, and another solid water surrogate phantom with a 25-cm diameter...
January 9, 2019: Radiological Physics and Technology
Mostafa Y A Mostafa, Hesham M H Zakaly, Michael Zhukovsky
Human pharmacokinetics and internal radiation dosimetry of normal organs after injection with the 99m Tc-labeled monoclonal antibody (intact and fragments) are simulated by the WinAct program and IDAC (Internal Dose Assessment by Computer) software. The WinAct program is used to calculate the cumulative activity in organs and tissues. The calculated cumulative activity is inputted to the IDAC software, an internal dosimetry program for nuclear medicine based on the International Commission on Radiological Protection (ICRP) adult reference voxel phantom, and the absorbed doses by the organs and tissues are estimated...
January 2, 2019: Radiological Physics and Technology
Bin Yang, Tin Lok Chiu, Wai Kong Law, Hui Geng, Wai Wang Lam, Tat Ming Leung, Lok Hang Yiu, Kin Yin Cheung, Siu Ki Yu
The aim of the current study was to evaluate the tracking error of the Synchrony Respiratory Tracking system by conducting beam-by-beam analyses to determine the variation in the tracking beams measured during target motion. A moving phantom of in-house design coupled with a two-dimensional (2D) detector array was used to simulate respiratory motion in the superoinferior (SI) and anteroposterior (AP) direction. A styrofoam block with four implanted fiducial markers was placed on top of the detector to enable the fiducial-based respiratory tracking...
January 2, 2019: Radiological Physics and Technology
Hiroyuki Sato, Takushi Takata, Yoshinori Sakurai
Radiation treatment planning for boron neutron capture therapy (BNCT) often uses computed tomography (CT) images reconstructed utilizing various section thickness and field-of-view (FOV) settings. Based on these images, a geometrical model is created by setting material regions manually over the pixel space defined in the treatment planning system. Thus, a setting difference of several pixels inevitably occurs in creation of the model. The influence of different section thicknesses and FOVs on thermal neutron flux estimations using the BNCT planning system was studied here...
December 19, 2018: Radiological Physics and Technology
Satoshi Yamaguchi, Eiichi Sato
To measure integral doses in image-guided radiation therapy, we developed an integral condenser dosimeter comprising a disposable USB-A mini-substrate with a 0.1-µF condenser and a silicon X-ray diode (Si-XD), a microcomputer (mbed) dock, and a personal computer (PC). The Si-XD is a high-sensitivity photodiode selected for detecting X-rays. The USB-A substrate with dimensions of 24 × 14 mm2 is inserted into the microcomputer dock, and the condenser is charged to 3.23 V through a 10-kΩ resistor. The condenser charging voltage is subsequently measured directly using an analog-digital converter (ADC) in mbed...
December 13, 2018: Radiological Physics and Technology
Jun Nakane, Norinari Honda, Kazuhiro Tsuchiya
The authors developed a method to ensure sufficient opacification of pulmonary vasculature for separate depiction of arteries and veins in three-dimensional form with a small dose of contrast medium utilizing a test injection to determine optimal timing of computed tomography (CT) scanning. The dose was determined by a simulation based on a pharmacokinetic model. The contrast medium was administered at a rate of 5.0 mL/s for 3 s, followed by helical scanning at the timing determined by a dynamic CT scanning following the test injection...
December 10, 2018: Radiological Physics and Technology
Hiroshi Ashiba, Ryohei Nakayama
Sentinel lymph node (SLN) biopsy for evaluating lymph node metastasis during breast cancer surgery is associated with several problems, such as the consequent increase in operation time and the possibility of abrupt changes in the treatment plan during the operation. Although it is desirable to distinguish SLNs with and without cancer metastasis before surgery, there is no established examination for this purpose. This study aimed to develop a computerized scheme for evaluating metastasis in SLNs by analyzing computed tomography lymphography images and the three-dimensional versions of these images...
November 29, 2018: Radiological Physics and Technology
Luca Coppeta, Antonio Pietroiusti, Anna Neri, Agostino Spataro, Elisabetta De Angelis, Stefano Perrone, Andrea Magrini
The main effect of ionizing radiation on the eyes is the onset of posterior cortical and subcapsular cataracts. Recent studies have raised questions about the mechanism of ocular damage and the threshold dose for the onset of such effects. Currently, operators may be exposed to ionizing radiation during surgical procedures. It has been estimated that urologists can be exposed to an annual dose close to or above 20 mSv/year. The aim of our study was to evaluate the frequency of cataracts in a group of professional radiological operators to verify their possible association with the radiation dose to the crystalline lens and the tasks performed...
November 26, 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
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