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Radiological Physics and Technology

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https://www.readbyqxmd.com/read/28921448/assessment-of-dose-uniformity-around-high-dose-rate-192-ir-and-60-co-stepping-sources
#1
Bagher Farhood, Mahdi Ghorbani
This study aimed to evaluate dose uniformity for (192)Ir and (60)Co stepping sources. High dose rate (192)Ir and (60)Co stepping sources were simulated by the MCNPX Monte Carlo code. To investigate dose uniformity, treatment lengths of 30, 50, 100, and 150 mm with stepping distances of 3, 5, 7, and 10 mm were considered. Finally, dose uniformity for the (192)Ir and (60)Co stepping sources with increasing distances from the source were assessed at these treatment lengths and steps. The findings showed that the dose distribution was non-uniform for regions in close vicinity of the source, especially in the high source steps, but for most points at distances >10 mm from the center of the source, the dose distribution was uniform...
September 18, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28895045/influence-of-gd-eob-dtpa-on-proton-density-fat-fraction-using-the-six-echo-dixon-method-in-3-tesla-magnetic-resonance-imaging
#2
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
The purpose of this study was to evaluate whether disodium gadoxetate (Gd-EOB-DTPA) affects proton density fat fractions (PDFFs) during use of the multiecho Dixon (meDixon) method in phantom and simulation magnetic resonance imaging (MRI) studies at 3 T. Fat-water phantoms comprising vegetable fat-water emulsions with varying fat volume percentages (0, 5, 10, 15, 20, 30, 40, and 50) and Gd-EOB-DTPA concentrations (0 and 0.4 mM) were prepared. Phantoms without Gd-EOB-DTPA were defined as precontrast, and those with Gd-EOB-DTPA were defined as postcontrast...
September 11, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28895040/clinical-utility-of-ultra-low-dose-pre-test-exposure-to-avoid-unnecessary-patient-exposure-due-to-positioning-errors-a-simulation-study
#3
Hideo Nose, Junji Shiraishi
The use of digital radiographic systems has decreased the frequency of image retakes due to over/underexposure in general radiography. However, image retakes owing to patient positioning errors are likely to increase because of the convenience of a real-time image check on a console table. The purpose of the present study is to propose a novel radiographic examination procedure with an ultra-low-dose pre-test exposure that may be utilized to check patient positioning prior to taking an actual image, thereby reducing unnecessary patient exposure owing to image retakes...
September 11, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28895034/whole-body-biodistribution-and-the-influence-of-body-activity-on-brain-kinetic-analysis-of-the-11-c-pib-pet-scan
#4
Go Akamatsu, Tomoyuki Nishio, Kazuhiko Adachi, Yasuhiko Ikari, Michio Senda
Dynamic (11)C-PiB PET imaging with kinetic analysis has been performed for accurate quantification of amyloid binding in patients with Alzheimer's disease (AD). In this study, we measured the whole-body biodistribution of (11)C-PiB in nine subjects. We then evaluated the effect of body activity on quantitative accuracy of brain (11)C-PiB three-dimensional (3D) dynamic PET. Based on clinical biodistribution data, we conducted phantom experiments to estimate the effect of body activity on quantification of the brain 3D dynamic (11)C-PiB PET data and the error introduced by body activity using six different PET camera models...
September 11, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28887805/quantitative-analysis-of-effects-of-hemodynamic-stress-on-temporal-variations-of-cardiac-phases-in-models-of-human-carotid-bulbs
#5
Tatsunori Saho, Hideo Onishi
In this study, we evaluated the hemodynamics of carotid artery models with carotid bulbs of various sizes using computational fluid dynamics (CFD) and the Fluent CFD software. The oscillatory shear index (OSI) and flow velocity distribution were evaluated in carotid models without a carotid bulb and with carotid bulbs of known geometry (major axis of 10, 11, 12, 13, and 14 mm; carotid bifurcation angle of 50°). Furthermore, the diameters of the common carotid artery, the external carotid artery, and the internal carotid artery were defined as 7...
September 8, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28879578/improved-wedge-method-for-the-measurement-of-sub-millimeter-slice-thicknesses-in-magnetic-resonance-imaging
#6
Tsutomu Kanazawa, Masaki Ohkubo, Tatsuya Kondo, Takayuki Miyazawa, Shoichi Inagawa
The standard method for measuring the slice thickness of magnetic resonance images uses the inclined surface of a wedge (wedge method); it is sensitive to small increases in noise because of the differentiation of the edge response function (ERF) required. The purpose of this study was to improve the wedge method by fitting a curve to the ERF. The curve-fit function was obtained by convolving an ideal ERF (a ramp function) with a Gaussian function to represent ERF blurring. Measurements of 5- and 3-mm slice thicknesses were performed on a 3T scanner using the conventional wedge method, the improved wedge method, and another standard method using an inclined slab (slab method)...
September 6, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28823084/effects-of-a-novel-tungsten-impregnated-rubber-neck-shield-on-the-quality-of-cerebral-images-acquired-using-15-o-labeled-gas
#7
Kei Wagatsuma, Keiichi Oda, Kenta Miwa, Motoki Inaji, Muneyuki Sakata, Jun Toyohara, Kiichi Ishiwata, Masayuki Sasaki, Kenji Ishii
The present study aimed to validate the effects of a novel tungsten-impregnated rubber neck shield on the quality of phantom and clinical (15)O-labeled gas positron emission tomography (PET) images. Images were acquired in the presence or absence of a neck shield from a cylindrical phantom containing [(15)O]H2O (phantom study) and from three individuals using [(15)O]CO2, [(15)O]O2 and [(15)O]CO gas (clinical study). Data were acquired in three-dimensional (3D) mode using a Discovery PET/CT 710. Values for cerebral blood flow, cerebral blood volume, oxygen extraction fraction, and cerebral metabolic rate of oxygen with and without the neck shield were calculated from (15)O-labeled gas images...
August 19, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28822095/validation-of-a-calibration-method-using-the-cross-calibration-factor-and-system-planar-sensitivity-in-quantitative-single-photon-emission-computed-tomography-imaging
#8
Norikazu Matsutomo, Saki Matsumoto, Tomoaki Yamamoto, Eisuke Sato
The present study aimed to validate the absolute quantitative accuracy of a calibration method for single-photon emission computed tomography (SPECT) using cross-calibration factor (CCF)- and system sensitivity-based calibration methods. The CCF obtained with different reconstruction parameters was evaluated using a cylindrical phantom (diameter 20 cm, height 20 cm). SPECT images were acquired with a positron emission tomography/computed tomography (CT) phantom. Subsequently, they were reconstructed by using ordered subset expectation maximization with resolution recovery, scatter, and CT-based attenuation correction...
August 18, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28822094/quantitative-knee-cartilage-measurement-at-mr-imaging-of-patients-with-anterior-cruciate-ligament-tear
#9
Kazuki Kato, Tamotsu Kamishima, Eiji Kondo, Tomohiro Onodera, Shota Ichikawa
In previous studies, numerous approaches were proposed that assess knee cartilage volume quantitatively using 3D magnetic resonance (MR) imaging. However, the clinical use of these approaches is limited because 3D MR is prone to metal artifacts in postoperative cases. Our purpose in this study was to validate a method for knee cartilage volume quantification using conventional MR imaging in patients who underwent anterior cruciate ligament (ACL) reconstruction surgery. The study included 16 patients who underwent MR imaging before and 1 year after ACL reconstruction surgery...
August 18, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28822074/general-equations-for-optimal-selection-of-diagnostic-image-acquisition-parameters-in-clinical-x-ray-imaging
#10
Xiaoming Zheng
The purpose of this work was to examine the effects of relationship functions between diagnostic image quality and radiation dose on the governing equations for image acquisition parameter variations in X-ray imaging. Various equations were derived for the optimal selection of peak kilovoltage (kVp) and exposure parameter (milliAmpere second, mAs) in computed tomography (CT), computed radiography (CR), and direct digital radiography. Logistic, logarithmic, and linear functions were employed to establish the relationship between radiation dose and diagnostic image quality...
August 18, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28815467/a-method-for-evaluating-luminance-non-uniformity-of-displays-by-use-of-a-commercially-available-digital-camera
#11
Keishin Kawamoto, Shogo Tokurei, Junji Morishita
The luminance uniformity of liquid-crystal displays (LCDs) deteriorates with their prolonged use. In this paper, we present a method for evaluating the degree of luminance non-uniformity of LCDs with the use of a commercially available digital camera. In this study, seven monochrome LCDs, which were used during various operating times ranging from 5000 to 25,000 h, were evaluated with use of a camera. The maximum luminance deviation (MLD) was measured on the two-dimensional (2D) images obtained with the camera...
August 16, 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28785993/quantification-of-the-radiation-dose-to-the-pyramidal-tract-using-tractography-in-treatment-planning-for-stereotactic-radiosurgery
#12
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
https://www.readbyqxmd.com/read/28770394/evaluation-of-six-point-modified-dixon-and-magnetic-resonance-spectroscopy-for-fat-quantification-a-fat-water-iron-phantom-study
#13
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
https://www.readbyqxmd.com/read/28762005/a-web-based-searchable-system-to-confirm-magnetic-resonance-compatibility-of-implantable-medical-devices-in-japan-a-preliminary-study
#14
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
https://www.readbyqxmd.com/read/28718054/mass-attenuation-coefficient-of-tannin-added-rhizophora-spp-particleboards-at-16-59-25-56%C3%A2-kev-photons-and-137-cs-and-60-co-gamma-energies
#15
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
https://www.readbyqxmd.com/read/28689314/overview-of-deep-learning-in-medical-imaging
#16
REVIEW
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
https://www.readbyqxmd.com/read/28689313/-137-cs-transmission-imaging-and-segmented-attenuation-corrections-in-a-small-animal-pet-scanner
#17
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
https://www.readbyqxmd.com/read/28676945/verification-of-the-tumor-volume-delineation-method-using-a-fixed-threshold-of-peak-standardized-uptake-value
#18
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
https://www.readbyqxmd.com/read/28573551/two-dimensional-breast-dosimetry-improved-using-three-dimensional-breast-image-data
#19
REVIEW
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 2017: Radiological Physics and Technology
https://www.readbyqxmd.com/read/28573550/optimal-injection-method-for-long-range-computed-tomography-angiography
#20
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
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