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Volume 29 (2012)
- Issue 4 Pages 68-
- Issue 3 Pages 43-
- Issue 2 Pages 28-
- Issue 1 Pages 1-
Volume 29, Issue 1
Displaying 1-5 of 5 articles from this issue
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Original Article
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Hiroaki HAYASHI, Naotaka KAMIYA, Syou TANIUCHI, Sadamitsu NISHIHARA, S ...2012 Volume 29 Issue 1 Pages 1-6
Published: 2012
Released on J-STAGE: March 27, 2012
JOURNAL FREE ACCESSIt is necessary to make adjustments on fading effects when experiments are made for acquiring numerous data at different irradiation times on the photostimulable phosphor plate. However, since the adjusted coefficient for the fading effect that suits every researcher's experimental condition is rarely published, each researcher needs to acquire his own fading data. The purpose of our study is to develop an experimental procedure that enables us to acquire the data and, at the same time, to adjust the fading effect. Under the general method for obtaining the characteristic curve, a set of data having different mAs conditions was stored on the plate. On the other hand, our method is to irradiate the x-ray twice consecutively under the same mAs condition. We repeated this process under different mAs experimental conditions. After receiving a series of data set by this method, we were able to differentiate the adjusted fading coefficients from the two sets of the data under the same experimental conditions. As a result, we were able to correct any fading effect with a 10% accuracy level.View full abstractDownload PDF (1220K) -
~the effect of massive fission yielded nuclei diffused by the accidents of nuclear power plants~Hiroaki HAYASHI, Sadamitsu NISHIHARA, Syou TANIUCHI, Naotaka KAMIYA2012 Volume 29 Issue 1 Pages 7-11
Published: 2012
Released on J-STAGE: March 27, 2012
JOURNAL FREE ACCESSCaused by an accident of nuclear power plants at Fukushima in March 2011, many radioisotopes were spread to the environment. In medical front, the black spots were appeared on the radiographic image stored by the phosphor plate and they had a negative impact on the diagnostic imaging. The aim of this study is to simulate the effect of the emitted radiation(β-rays and/or γ-rays)on the luminescence of the photostimulable phosphor, and to evaluate the most effective RI to produce the black spots. We focused attention to the five nuclides(90Sr-90Y, 131I, 134Cs, 137Cs), and contributions for appearance of the black spots were calculated. In the simulation, the β-rays and γ-rays of each nuclide were individually estimated. As a result, we found that the contribution of β-rays was much larger than that of the γ-rays. Moreover, we considered about the main nuclei to produce the black spots based on the simulated results and the measured data by MEXT(Ministry of Education, Culture, Sports, Science and Technology). In the case in which RI was directly adhered on the phosphor plate, the β-ray emitted from 137Cs was main cause. In the other case in which RI was attached at the supporting equipments(cassette etc.), the γ-ray emitted from 134Cs was main cause.View full abstractDownload PDF (985K)
Note
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Satoru MATSUO, Tetsuro KATAFUCHI, Junji MORISHITA, Hiroshi FUJITA2012 Volume 29 Issue 1 Pages 12-19
Published: 2012
Released on J-STAGE: March 27, 2012
JOURNAL FREE ACCESSPhase contrast imaging is characterized by edge-enhancement of objective image boundaries. The conditions of geometric unsharpness, i.e. the focal spot size of an X-ray tube and the relation between the focus-object distance R1 and object-detector distance R2, are important factors in edge-enhancement. In this study, we investigated the following two issues: First, evaluation of the magnification factor that yields maximum edge-enhancement effect; second, an evaluation of the sampling pitch of digitization without loss of the edge-enhancement effect. For this purpose, we imaged a plastic-fiber of 3.0mm in diameter using various magnification factors and a screen-film system as the detector. We considered that the optimum magnification factor would be the one to yield the strongest edge-enhancement, and that the optimum sampling pitch size would be the one which retained the same degree of edge-enhancement as reflected by an “analog" profile curve of the plastic-fiber image. As a result, the optimum magnification ratio was found to be 1.75times, when R1 was 65cm using an X-ray tube of 0.1mm focus spot size. We also found that edge-enhancement in phase contrast imaging can be effectively achieved with digital imaging when acquired with a sampling pitch of 0.025mm or less.View full abstractDownload PDF (1491K)
Work in progress
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Risa YORIMITSU, Tosiaki MIYATI, Hirohito KAN, Naoki OHNO, Masaki HARA, ...2012 Volume 29 Issue 1 Pages 20-22
Published: 2012
Released on J-STAGE: March 27, 2012
JOURNAL FREE ACCESSWe evaluated water molecular displacement in vertebral bone marrow using q-space analysis to provide the detailed data on changing bone information. On a 1.5T MRI, single-shot diffusion echo planar imaging was used with multi b values. Displacement of the water molecules was obtained from the displacement probability profile calculated by Fourier transform of the signal decay as a function of the reciprocal spatial vector q. Mean water molecular displacement was determined in the lumbar vertebral body(L2–L4)of eleven normal subjects, and then compared with the bone mineral density(BMD)obtained with dual-energy X-ray absorptiometry(DXA). Moreover, fat fraction(FF)of the bone marrow was measured with spectral adiabatic inversion recovery(SPAIR)in the same subject. A strong positive correlation was found between mean water molecular displacement and BMD in the vertebral bone marrow(R2=0.92, P<0.001). Moreover, a negative correlation was noted between mean water displacement and FF(R2=0.69, P<0.01). In addition, there was a negative correlation between BMD and FF(R2=0.73, P<0.05). Water molecular displacement analysis with q-space makes it noninvasively possible to obtain more detailed information on changing bone marrow composition, and metabolism.View full abstractDownload PDF (1155K) -
Hirohito KAN, Tosiaki MIYATI, Mitsuhito MASE, Harumasa KASAI, Naoki OH ...2012 Volume 29 Issue 1 Pages 23-27
Published: 2012
Released on J-STAGE: March 27, 2012
JOURNAL FREE ACCESSTo evaluate the hemodynamic-independent biomechanical-information of the brain, we determined changes in the regional apparent diffusion coefficient(ADC)and total cerebral blood flow(tCBF)during the cardiac cycle using magnetic resonance imaging(MRI). The water fluctuation index(WFI), which was defined as a ratio of the regional ADC and the tCBF changes during the cardiac cycle(delta-ADC and delta-tCBF), was obtained from ECG-triggered single-shot diffusion echo planar imaging and phase-contrast cine MRI, respectively. The WFI was assessed in patients with idiopathic normal pressure hydrocephalus(I-NPH, n=2), brain atrophy or asymptomatic ventricular dilation(VD, n=2)and in healthy volunteers(control group, n=9). WFIs in I-NPH were clearly higher than those in VD and control because the water molecules in cerebral white matter in I-NPH easily fluctuate owing to the arterial blood volume loading of the cranium, due to the decreasing the lower compliance in I-NPH, compared with that in control. On the other hand, delta-ADC in I-NPH was higher than that in control while delta-tCBF in I-NPH was lower. However, the differences between them were lower than the WFI. WFI analysis makes it possible to obtain biomechanical information as the fluctuation of the water molecules hemodynamic-independently in the brain, and may assist in the diagnosis of I-NPH.View full abstractDownload PDF (1679K)
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