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Radiological Physics and Technology

Tatsuya Hayashi, Kei Fukuzawa, Hiroshi Kondo, Hiroshi Onodera, Shuji Toyotaka, Rie Tojo, Shimpei Yano, Masakatsu Tano, Tosiaki Miyati, Jun'ichi Kotoku, Takahide Okamoto, Keiko Toyoda, Hiroshi Oba
A diameter of glass bottles in phantoms in the above article (2 cm) was incorrect. The correct diameter is 4.5 cm.
March 14, 2018: Radiological Physics and Technology
Keisuke Usui, Keisuke Sasai, Koichi Ogawa
This study aimed to verify the validity of generating treatment plans for volumetric arc therapy (VMAT) for prostate cancer using magnetic resonance (MR) imaging with a dose calculation algorithm in Acuros XB (Eclipse version 13.6; Varian Medical Systems, Palo Alto, CA, USA) based on deterministically solving the linear Boltzmann transport equations. Four different classes were applied to prostate MR images: MRW (all water equivalent); MRW+B (water and bone); MRS+B (soft tissue and bone); and MRS+B+G (soft tissue, bone, and rectal gas)...
March 14, 2018: Radiological Physics and Technology
Yuji Nakaguchi, Takeshi Oono, Masato Maruyama, Yoshinobu Shimohigashi, Yudai Kai, Yuya Nakamura
In this study, we evaluated the basic performance of the three-dimensional dose verification system COMPASS (IBA Dosimetry). This system is capable of reconstructing 3D dose distributions on the patient anatomy based on the fluence measured using a new transmission detector (Dolphin, IBA Dosimetry) during treatment. The stability of the absolute dose and geometric calibrations of the COMPASS system with the Dolphin detector were investigated for fundamental validation. Furthermore, multileaf collimator (MLC) test patterns and a complicated volumetric modulated arc therapy (VMAT) plan were used to evaluate the accuracy of the reconstructed dose distributions determined by the COMPASS...
March 12, 2018: Radiological Physics and Technology
Maria D Falco, Salvatore Masala, Matteo Stefanini, Paolo Bagalà, Daniele Morosetti, Eros Calabria, Alessia Tonnetti, Gianluca Verona-Rinati
Interventional radiology is based on minimally invasive procedures that allow diagnosis and percutaneous treatment of diseases in almost all organ systems. Such procedures have many benefits, but they also contribute significantly to collective radiation dose. In this regard, effective dose (E) is a convenient quantity to estimate patients' stochastic radiation risk. However, E cannot be accurately evaluated immediately. In the present study, we aimed to estimate the E value in 15 selected interventional procedures...
March 8, 2018: Radiological Physics and Technology
Yuuji Inoue, Masami Yoneyama, Masanobu Nakamura, Atsushi Takemura
The two-dimensional Cartesian turbo spin-echo (TSE) sequence is widely used in routine clinical studies, but it is sensitive to respiratory motion. We investigated the k-space orders in Cartesian TSE that can effectively reduce motion artifacts. The purpose of this study was to demonstrate the relationship between k-space order and degree of motion artifacts using a moving phantom. We compared the degree of motion artifacts between linear and asymmetric k-space orders. The actual spacing of ghost artifacts in the asymmetric order was doubled compared with that in the linear order in the free-breathing situation...
March 7, 2018: Radiological Physics and Technology
Shinichiro Mori, Masahiro Endo
No abstract text is available yet for this article.
March 6, 2018: Radiological Physics and Technology
Yasuhiro Fujiwara, Hirotoshi Maruyama, Kanako Toyomaru, Yuri Nishizaka, Masahiro Fukamatsu
Magnetic resonance imaging (MRI) is widely used to detect carotid atherosclerotic plaques. Although it is important to evaluate vulnerable carotid plaques containing lipids and intra-plaque hemorrhages (IPHs) using T1 -weighted images, the image contrast changes depending on the imaging settings. Moreover, to distinguish between a thrombus and a hemorrhage, it is useful to evaluate the iron content of the plaque using both T1 -weighted and T2 *-weighted images. Therefore, a quantitative evaluation of carotid atherosclerotic plaques using T1 and T2 * values may be necessary for the accurate evaluation of plaque components...
March 6, 2018: Radiological Physics and Technology
Hiroaki Hasegawa, Jiro Sato, Ikuo Kobayashi
The authors aimed to evaluate the effects of the half-scan mode on image quality and physician exposure to radiation in computed tomography (CT)-guided interventional radiology (IVR) to the right lung using an intermittent CT fluoroscopy technique for measuring phantom surface dose distribution and image noise. For the half-scan mode, settings at 0°, 90°, 180°, and 270° were used as the central axis of the X-ray exposure range on the chest phantom. With the center of the ventral side in the chest phantom defined as 0°, optically stimulated luminescent dosimeters were attached at five positions at 30° intervals on the right side of the phantom surface...
February 27, 2018: Radiological Physics and Technology
Chiaki Tominaga, Hiroki Azumi, Mitsunori Goto, Masaaki Taura, Noriyasu Homma, Issei Mori
Edge methods are predominantly used for modulation transfer function (MTF) measurements in computed tomography (CT) images reconstructed using iterative methods. However, edge methods employ a relatively large and distinct test object, which is intended to simulate relatively large and distinct clinical organs. If one wants to assess the image quality of a small low-contrast object that is visually indistinct against a noisy background, a small and indistinct test object is desired. Another concern is that information related to the signal amount is discarded during MTF measurements...
February 23, 2018: Radiological Physics and Technology
Nobuyuki Kanematsu, Naruhiro Matsufuji, Taku Inaniwa
A treatment of carbon-ion radiotherapy (CIRT) is generally evaluated using the dose weighted by relative biological effectiveness (RBE) while ignoring the radiation quality varying in the patient. In this study, we have developed a method of estimating linear energy transfer (LET) from the RBE in an archived treatment plan to represent the radiation quality of the treatment. The LET in a beam database was associated with the RBE by two fitting functions per energy, one for the spread-out Bragg peak (SOBP) and the other for shallower depths, to be differentiated by RBE per energy per modulation...
February 22, 2018: Radiological Physics and Technology
Shuki Maruyama, Yasuhiro Fukushima, Yuta Miyamae, Koji Koizumi
This study aimed to investigate the effects of parameter presets of the forward projected model-based iterative reconstruction solution (FIRST) on the accuracy of pulmonary nodule volume measurement. A torso phantom with simulated nodules [diameter: 5, 8, 10, and 12 mm; computed tomography (CT) density: - 630 HU] was scanned with a multi-detector CT at tube currents of 10 mA (ultra-low-dose: UL-dose) and 270 mA (standard-dose: Std-dose). Images were reconstructed with filtered back projection [FBP; standard (Std-FBP), ultra-low-dose (UL-FBP)], FIRST Lung (UL-Lung), and FIRST Body (UL-Body), and analyzed with a semi-automatic software...
February 10, 2018: Radiological Physics and Technology
Ayako Yagahara, Yuki Yokooka, Guoqian Jiang, Shintarou Tsuji, Akihisa Fukuda, Naoki Nishimoto, Kunio Kurowarabi, Katsuhiko Ogasawara
Describing complex mammography examination processes is important for improving the quality of mammograms. It is often difficult for experienced radiologic technologists to explain the process because their techniques depend on their experience and intuition. In our previous study, we analyzed the process using a new bottom-up hierarchical task analysis and identified key components of the process. Leveraging the results of the previous study, the purpose of this study was to construct a mammographic examination process ontology to formally describe the relationships between the process and image evaluation criteria to improve the quality of mammograms...
January 10, 2018: Radiological Physics and Technology
Mohammad Mehdi Firoozabadi, Elaheh Jimabadi, Mahdi Ghorbani, Marziyeh Behmadi
The CSM40 137Cs source model is currently being used in clinical brachytherapy. According to the recommendations of task group No. 43 (TG-43) of the American Association of Physicists in Medicine, dosimetry parameters of brachytherapy sources should be determined by two independent investigators before their clinical use. The aim of this study was to determine the TG-43 dosimetry parameters for a medium-dose-rate CSM40 137Cs source. The determined dosimetric parameters included the air kerma strength, dose rate constant, radial dose function, and anisotropy function...
January 3, 2018: Radiological Physics and Technology
Yoshinori Tsuji, Satoshi Saitoh, Junji Takahashi, Chisato Abe, Tatsuya Hayashi, Masahiro Kobayashi
The controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique can decrease scan time. The purpose of this study was to determine whether an arterial phase scan can be performed in 5 s using the CAIPIRINHA short-scan and a reference scanning technique. The generalized autocalibrating partially parallel acquisition (GRAPPA), the CAIPIRINHA routine (CAIPI-routine), and the CAIPIRINHA short-scanning (CAIPI-short) methods were compared. The scan time for each method was preset to 20 s, 15 s, and 10 s, respectively...
January 3, 2018: Radiological Physics and Technology
Yohei Miura, Katsuhiro Ichikawa, Ichiro Fujimura, Takanori Hara, Takashi Hoshino, Shinji Niwa, Masao Funahashi
The 320-detector row computed tomography (CT) system, i.e., the area detector CT (ADCT), can perform helical scanning with detector configurations of 4-, 16-, 32-, 64-, 80-, 100-, and 160-detector rows for routine CT examinations. This phantom study aimed to compare the quality of images obtained using helical scan mode with different detector configurations. The image quality was measured using modulation transfer function (MTF) and noise power spectrum (NPS). The system performance function (SP), based on the pre-whitening theorem, was calculated as MTF2/NPS, and compared between configurations...
January 2, 2018: Radiological Physics and Technology
Abdel-Razzak M Al-Hinnawi, Bassam O Al-Naami, Haytham Al-Azzam
This paper explores the benefits of interactive three-dimensional (3D) visualization of stimuli using a computer aided detection (CAD) system of pulmonary embolisms (PEs), on computed tomography pulmonary angiography (CTPA) views. We designed a new CAD method that prompts the PE sites on CTPA views; we then utilized two interactive approaches of 3D visualization to assess CAD performance. This collaboration allows different methodologies to be used to assess PE-CAD performance, by comparison with the common method in which radiologists are prompted with CAD stimuli directly on the CTPA views...
December 28, 2017: Radiological Physics and Technology
Toshiyuki Terunuma, Aoi Tokui, Takeji Sakae
Robustness to obstacles is the most important factor necessary to achieve accurate tumor tracking without fiducial markers. Some high-density structures, such as bone, are enhanced on X-ray fluoroscopic images, which cause tumor mistracking. Tumor tracking should be performed by controlling "importance recognition": the understanding that soft-tissue is an important tracking feature and bone structure is unimportant. We propose a new real-time tumor-contouring method that uses deep learning with importance recognition control...
December 28, 2017: Radiological Physics and Technology
Hitoshi Saito, Teruhiro Ito, Takakiyo Tsujiguchi, Masaru Yamaguchi, Ikuo Kashiwakura
This study aimed to analyze the temporal sensitivity profile (TSP) shapes and temporal resolutions of computed tomography (CT) and investigate the effect of a combination of a given rotation time and helical pitch on the TSP and image quality. The study was performed on 16- and 64-row CT scanners, and the TSP and temporal resolution were measured using the impulse method. A shorter gantry rotation time and larger helical pitch improved the temporal resolution of both CT scanners. Although the measured TSP shapes were dependent on the helical pitch, the maximum helical pitch did not improve the temporal resolution of either CT scanner...
December 20, 2017: Radiological Physics and Technology
Akihiro Haga, Wataru Takahashi, Shuri Aoki, Kanabu Nawa, Hideomi Yamashita, Osamu Abe, Keiichi Nakagawa
Radiomics, which involves the extraction of large numbers of quantitative features from medical images, has attracted attention in cancer research. In radiomics analysis, tumor segmentation is a crucial step. In this study, we evaluated the potential application of radiomics for predicting the histology of early stage non-small cell lung cancer (NSCLC) by analyzing interobserver variability in tumor delineation. Forty patient datasets were included in this study, 21 involving adenocarcinomas and 19 involving squamous cell carcinomas...
March 2018: Radiological Physics and Technology
Kenichiro Yamamura, Yasuo Takatsu, Toshiaki Miyati
In acoustic-stimulated functional magnetic resonance imaging (fMRI), tasks are performed by subjects either during imaging in the presence of scanning noise or during non-imaging periods without scanning noise. Suitable syllables for voice tasks performed with MRI-compatible headphones are limited during the imaging period with scanning noise. However, suitable syllables for voice tasks during the non-imaging period, without scanning noise, are not yet known. This study aimed to identify suitable syllables for voice tasks during both imaging and non-imaging periods...
March 2018: Radiological Physics and Technology
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