Read by QxMD icon Read

Radiological Physics and Technology

Masaru Sekiya, Michio Yamasaki
No abstract text is available yet for this article.
October 6, 2016: Radiological Physics and Technology
Yuki Ichinoseki, Yoshio Machida
Our purpose in this study was to elucidate the relation between the one-dimensional (1D) and two-dimensional (2D) noise power spectra (NPSs) in magnetic resonance imaging (MRI). We measured the 1D NPSs using the slit method and the radial frequency method. In the slit method, numerical slits 1 pixel wide and L pixels long were placed on a noise image (128 × 128 pixels) and scanned in the MR image domain. We obtained the 1D NPS using the slit method (1D NPS_Slit) and the 2D NPS of the noise region scanned by the slit (2D NPS_Slit)...
October 3, 2016: Radiological Physics and Technology
Kevin J Chang, Scott Collins, Baojun Li, William W Mayo-Smith
For assessment of the effect of varying the peak kilovoltage (kVp), the adaptive statistical iterative reconstruction technique (ASiR), and automatic dose modulation on radiation dose and image noise in a human cadaver, a cadaver torso underwent CT scanning at 80, 100, 120 and 140 kVp, each at ASiR settings of 0, 30 and 50 %, and noise indices (NIs) of 5.5, 11 and 22. The volume CT dose index (CTDIvol), image noise, and attenuation values of liver and fat were analyzed for 20 data sets. Size-specific dose estimates (SSDEs) and liver-to-fat contrast-to-noise ratios (CNRs) were calculated...
October 3, 2016: Radiological Physics and Technology
Lutfi Ergun, Turan Olgar
The performance of digital radiography systems can be evaluated in terms of spatial resolution and noise. Noise plays an important role in the achievable image quality for detecting small and low-contrast structures in digital images created by these systems. Our aim in this study was to investigate the noise sources both in the spatial and frequency domain for three digital radiography systems, one digital fluoroscopy system, and one digital mammography system, and to obtain information about the effective operating dose range of these detectors...
October 1, 2016: Radiological Physics and Technology
Yuya Ishikawa, Atsushi Urikura, Tsukasa Yoshida, Keisuke Takiguchi, Yoshihiro Nakaya
The purpose of this study was to optimize the monitoring dose, obtained using the conventional filtered back projection (FBP) method and iterative reconstruction algorithms, for the bolus tracking technique. A phantom study was performed to assess the effect of the scan start time in patients grouped according to different body weights. An oval torso phantom was used for simulating the time enhancement curve of the bolus tracking technique. To reproduce image noise levels in the two body weight groups, the phantom diameter was adjusted with a water-equivalent material...
September 30, 2016: 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...
September 19, 2016: Radiological Physics and Technology
Yasuhiro Fujiwara, Yoshiyuki Muranaka
Three-dimensional time-of-flight magnetic resonance angiography (TOF MRA) has been widely used in clinics. TOF MRA can cause dephasing artifacts, which lead to an intraluminal signal decrease. Silent MRA is a novel imaging technique that uses arterial spin labeling to achieve an ultrashort echo time (uTE), which is expected to decrease these effects and allow for accurate assessment of the flow in blood vessels. This study quantified the accuracy of Silent MRA images for visualizing the turbulent flow in flow-phantom and in vivo studies...
September 8, 2016: Radiological Physics and Technology
Haruo Yamashita, Yuki Kase, Shigeyuki Murayama
In radiotherapy involving craniospinal irradiation (CSI), field junctions of therapeutic beams are necessary, because a CSI target is generally several times larger than the maximum field size of the beams. The purpose of this study was to develop a simplified method for estimating dose uniformity around the field junctions in proton CSI. We estimated the dose profiles around the field junctions of proton beams using a simplified field-junction model, in which partial lateral dose distributions around the field edge were assumed to be approximated using the error function...
September 1, 2016: Radiological Physics and Technology
Yoshinori Tanabe, Takayuki Ishida
A new method was developed for quantifying the accuracy limits of image registration devices and the distortion of anatomical structures in verification images without image registration. A correlation was found between peak signal-to-noise ratio (PSNR) and the amount of parallel movement (1-10 mm at 1-mm intervals) of a rectangular parallelepiped phantom [correlation coefficient (CC) -0.91, contribution ratio (CR) 0.83]. Rotating the phantom from 1° to 10° at 1° intervals produced a similar correlation with PSNR (CC -0...
August 18, 2016: Radiological Physics and Technology
Bimali Sanjeevani Weerakoon, Toshiaki Osuga
The observation of molecular diffusion by means of magnetic resonance imaging (MRI) is significant in the evaluation of the metabolic activity of living tissues. Series of MRI examinations were conducted on a diffusion model to study the behaviour of the diffusion process of different-molecular-weight (MW) paramagnetic MRI contrast agents in an isotropic agar hydrogel medium. The model consisted of a solidified 1 % agar gel with an initial concentration of 0.5 mmol/L contrast solution layered on top of the gel...
August 17, 2016: Radiological Physics and Technology
Shuji Nagamine, Toshioh Fujibuchi, Yoshiyuki Umezu, Kazuhiko Himuro, Shinichi Awamoto, Yuji Tsutsui, Yasuhiko Nakamura
In this study, we estimated the ambient dose equivalent rate (hereafter "dose rate") in the fluoro-2-deoxy-D-glucose (FDG) administration room in our hospital using Monte Carlo simulations, and examined the appropriate medical-personnel locations and a shielding method to reduce the dose rate during FDG injection using a lead glass shield. The line source was assumed to be the FDG feed tube and the patient a cube source. The dose rate distribution was calculated with a composite source that combines the line and cube sources...
August 16, 2016: Radiological Physics and Technology
Francisco Albiol, Alberto Corbi, Alberto Albiol
We explore three different alternatives for obtaining intrinsic and extrinsic parameters in conventional diagnostic X-ray frameworks: the direct linear transform (DLT), the Zhang method, and the Tsai approach. We analyze and describe the computational, operational, and mathematical background differences for these algorithms when they are applied to ordinary radiograph acquisition. For our study, we developed an initial 3D calibration frame with tin cross-shaped fiducials at specific locations. The three studied methods enable the derivation of projection matrices from 3D to 2D point correlations...
July 18, 2016: Radiological Physics and Technology
Fumio Hashimoto, Atsushi Teramoto, Yasuki Asada, Shoichi Suzuki, Hiroshi Fujita
Recently, region-setting computed tomography (CT) has been studied as a region of interest imaging method. This technique can strongly reduce the radiation dose by limiting the irradiation field. Although mathematical studies have been performed for reduction of the truncation artifact, no experimental studies have been performed so far. In this study, we developed a three-dimensional region-setting CT system and evaluated its imaging properties. As an experimental system, we developed an X-ray CT system with multileaf collimators...
July 9, 2016: Radiological Physics and Technology
Nobuyuki Kudomi, Yukito Maeda, Tetsuhiro Hatakeyama, Yuka Yamamoto, Yoshihiro Nishiyama
PET enables quantitative imaging of the rate constants K 1, k 2, k 3, and k 4, with a reversible two tissue compartment model (2TCM). A new method is proposed for computing all of these rates within a reasonable time, less than 1 min. A set of differential equations for the reversible 2TCM was converted into a single formula consisting of differential and convolution terms. The validity was tested on clinical data with (18)F-FLT PET for patients with glioma (n = 39). Parametric images were generated with the formula that was developed...
July 5, 2016: Radiological Physics and Technology
Rie Tanaka
Dynamic chest radiography is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view (FOV) of FPDs permits real-time observation of the entire lungs and simultaneous right-and-left evaluation of diaphragm kinetics. Most importantly, dynamic chest radiography provides pulmonary ventilation and circulation findings as slight changes in pixel value even without the use of contrast media; the interpretation is challenging and crucial for a better understanding of pulmonary function...
July 2016: Radiological Physics and Technology
(no author information available yet)
No abstract text is available yet for this article.
July 2016: Radiological Physics and Technology
Sukhvir Singh, Ajay K Singh, Manoj K Semwal, Virender Suhag, Arti Sarin, Aruna Kaushik
It is known that the output factors (OPFs) for external-beam radiotherapy units increase with field size due to increased scattered radiation from the collimator system. Saturation in the OPF value is generally reported beyond approximately 30 × 30 cm(2). For the first time, to the best of our knowledge, we report on a drop in OPF values, although marginal, measured for a telecobalt machine beyond the 38 × 38 cm(2) field size. We believe that reporting and explaining the results will lead to a better understanding of the scatter composition of the radiation from telecobalt machines...
July 2016: Radiological Physics and Technology
Toru Takakura, Yoshiyuki Ito, Akinori Higashikawa, Tomohiro Nishiyama, Takashi Sakamoto
This study measured the dose attenuation of a newly developed vacuum cushion for intensity-modulated radiation therapy (IMRT) of prostate cancer, and verified the effect of dose-correction accuracy in a radiation treatment planning system (RTPS). The new cushion was filled with polystyrene foams inflated 15-fold (Sφ ≒ 1 mm) to reduce contraction caused by air suction and was compared to normal polystyrene foam inflated to 50-fold (Sφ ≒ 2 mm). The dose attenuation at several thicknesses of compression bag filled with normal and low-inflation materials was measured using an ionization chamber; and then the calculated RTPS dose was compared to ionization chamber measurements, while the new cushion was virtually included as region of interest in the calculation area...
July 2016: Radiological Physics and Technology
Kazuki Takegami, Hiroaki Hayashi, Hiroki Okino, Natsumi Kimoto, Itsumi Maehata, Yuki Kanazawa, Tohru Okazaki, Takuya Hashizume, Ikuo Kobayashi
Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector...
July 2016: Radiological Physics and Technology
Tatsunori Saho, Hideo Onishi
In this study, we evaluated the hemodynamics of carotid artery bifurcation with various geometries using simulated and volunteer models based on magnetic resonance imaging (MRI). Computational fluid dynamics (CFD) was analyzed by use of OpenFOAM. The velocity distribution, streamline, and wall shear stress (WSS) were evaluated in a simulated model with known bifurcation angles (30°, 40°, 50°, 60°, derived from patients' data) and in three-dimensional (3D) healthy volunteer models. Separated flow was observed at the outer side of the bifurcation, and large bifurcation models represented upstream transfer of the point...
July 2016: Radiological Physics and Technology
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"