Biomedical subjects

Masao Matsumoto

Publications and source records attributed to Masao Matsumoto.

14 recordsLinked to original sources

PubMed2006

[Image quality and detection performance of a direct digital radiography system].

The physical characteristics of a direct amorphous Selenium (a-Se) digital fluoroscopy and radiography system were investigated. Pre-sampled modulation transfer functions (MTF) were measured using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform of uniformly exposed samples. The MTFs of direct digital radiography systems showed significantly higher values than those of indirect digital radiography and screen-film systems. The direct digital radiography systems showed higher noise levels compared with those of indirect systems under roughly the same exposure conditions. Contrast-detail analysis was performed to compare detection by direct digital radiography systems with that of the screen-film (FUJI HG-M2/UR2) systems. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that digital contrast-detail curves and IQF are, on average, are equal those of the screen-film system.

Fourier Analysis↗

PubMed2005

Physical imaging properties and low-contrast performance of a newly developed flat-panel digital radiographic system.

We investigated the clinical usefulness of a newly developed flat-panel detector (FPD) system by comparing its physical imaging properties and low-contrast detectability with those of a current FPD system. The newly developed CsI-based indirect FPD (Canon, CXDI-40C) and current Gd(2)O(2)S-based FPD (Canon CXDI-11) systems were used. Characteristic curves, resolution properties, radiographic noise, detective quantum efficiencies (DQEs) and low-contrast detectability for both systems were measured. The new FPD system showed considerably lower noise levels than those of the current FPD system. DQE (0) s of the new and current FPD systems were 75% and 35%, respectively. Observer performance tests of the contrast-detail (C-D) phantom indicated that the new FPD system can significantly improve low-contrast performance over that obtainable with the current FPD system under the same conditions of exposure. The new FPD system provided approximately 50% reduction in exposure while providing comparable detectability. The newly developed FPD system provides radiographic images with excellent inherent physical image quality and low-contrast performance.

Cesium↗

PubMed2005

Compton-scattering measurement of diagnostic x-ray spectrum using high-resolution Schottky CdTe detector.

The analysis of x-ray spectra is important for quality assurance (QA) and quality control (QC) of radiographic systems. The aim of this study is to measure the diagnostic x-ray spectra under clinical conditions using a high-resolution Schottky CdTe detector. Under clinical conditions, the direct measurement of a diagnostic spectrum is difficult because of the high photon fluence rates that cause significant detector photon pile-up. An alternative way of measuring the output spectra from a tube is first to measure the 90 deg Compton scattered photons from a given sample. With this set-up detector, pile-up is not a problem. From the scattered spectrum one can then use an energy correction and the Klein-Nishina function to reconstruct the actual spectrum incident upon the scattering sample. The verification of whether our spectra measured by the Compton method are accurate was accomplished by comparing exposure rates calculated from the reconstructed spectra to those measured with an ionization chamber. We used aluminum (Al) filtration ranging in thickness from 0 to 6 mm. The half value layers (HVLs) obtained for a 70 kV beam were 2.78 mm via the ionization chamber measurements and 2.93 mm via the spectral measurements. For a 100 kV beam we obtained 3.98 and 4.32 mm. The small differences in HVLs obtained by both techniques suggest that Compton scatter spectroscopy with a Schottky CdTe detector is suitable for measuring the diagnostic x-ray spectra and useful for QA and QC of clinical x-ray equipment.

Aluminum↗

PubMed2004

Linear deposition of immunoglobulins and complement components on the dura in normal pressure hydrocephalus complicating systemic lupus erythematosus.

We present a case of normal pressure hydrocephalus in a 70-year-old man with previously diagnosed systemic lupus erythematosus. Histological examination demonstrated the linear deposition of IgG, IgA, IgM, C(3) and C(1q) on the dura in the absence of inflammation or thrombosis that has previously been implicated in the aetiology of elevated pressure hydrocephalus in systemic lupus erythematosus. Our results suggest that the deposition of immunoglobulins and complement may play a pivotal role in an insidious manner in the pathogenesis of normal pressure hydrocephalus in systemic lupus erythematosus.

Aged↗

PubMed2004

[Measurement and correction of diagnostic X-ray spectra using a high resolution Schottky CdTe detector].

The purpose of this study is to measure diagnostic x-ray spectra using a high resolution Schottky CdTe detector (TOYO MEDIC RAMTEC 413A) and to determine the best response function of CdTe detector for correcting the measured spectra with using a rise time discrimination (RTD) circuit to primary x-ray spectra. Since the measured spectra were distorted by the response of CdTe detector and did not present the true photon spectra, the correction by the stripping procedure was applied. The response function of CdTe detector has been determined by using Monte Carlo simulation method for calculating the photon interaction (K-escape, coherent scattering and Compton scattering) and incomplete charge collection by trapping of hole and use of RTD circuit. This simulation performed with various important factors (mean path length lambda(h) of hole and weight factor W(q) of incomplete charge collection) for finding the best response function. The photon spectra corrected with those various response functions were compared with the corrected photon spectra measured using a high purity Ge (HP-Ge) detector (PRINCETON GAMMA-TECH NIGP1013345), and the Al-attenuation curves calculated from corrected spectra and measured using the HP-Ge detector were compared. The best-fitted response function was determined, and the attenuation curves calculated from the spectra corrected with this response function were agreed with that measured using the HP-Ge detector within maximum error 0.03 of the attenuation rate and 5.0 % of the half value layer.

Gamma Rays↗

PubMed2004

Mammographic x-ray spectra measured by Compton spectroscopy using a high resolution Schottky CdTe detector.

Analysis of x-ray spectra is important for quality assurance (QA) and quality control (QC) of radiographic systems. This is especially true for mammographic x-ray imaging systems which require low-contrast detectability. Under clinical conditions, the measurement of diagnostic x-ray spectra is difficult because of pulse pile-up due to the high fluence rate of incident x-ray photons. However, it is difficult to set a long source-to-detector distance to reduce the number of photons detected per unit time for mammographic x-ray units. Compton spectroscopy is a suitable tool to deal with this problem. Detection of 90-degrees scattered photons only, energy correction and reconstruction are easy using the Klein-Nishina formula. However, x-ray spectra measured by this method have lower energy resolution, because of the geometrical irradiation angle or electron movement in the scatterer. Moreover, spectra measured with a compound semiconductor detector, such as a high resolution Schottky CdTe detector like we used, are distorted by the detector response, which is based on detecting x-ray photon interactions and charge carrier trapping in the semiconductor crystal. While the distortion of spectra caused by the response can be easily corrected by applying a stripping procedure, it is very difficult to reconstruct the broad spectra measured by Compton spectroscopy as sharp spectra such as obtained when directly measured. Some complicated reconstruction algorithms have been reported to fit the shape of spectra obtained by the Compton spectroscopy to sharp standard spectra. However, for QA / QC of the radiographic system, it is not necessary to correct the spectra sharply if the spectral broadening is at a tolerable level and the properties of the broad spectra acquired by the Compton spectroscopy agree with those of the sharp spectra measured directly; i.e. evaluations are necessary only for estimation of spectral shape. In this paper, we compared attenuation curves calculated using Hubbell's attenuation coefficients to estimate the coincidence or difference of spectra measured by the Compton spectroscopy and directly measured in the primary beam. Our results showed that the attenuation curves acquired from the reconstructed spectra measured by the Compton spectroscopy agreed with that acquired from corrected spectra that were directly measured. Moreover, the attenuation curves acquired from the spectra actually measured by adding aluminum attenuators agreed with theoretically calculated curves.

Mammography↗

PubMed2003

Dopamine-induced protection against indomethacin-evoked intestinal lesions in rats--role of anti-intestinal motility mediated by D2 receptors.

BACKGROUND: Although it is known that dopamine prevents various gastrointestinal lesions, the underlying mechanism remains unclear. In the present study, we examined the protective effect of dopamine on indomethacin-induced small intestinal lesions, in relation to intestinal hypermotility. MATERIAL/METHODS: Male SD rats received indomethacin (10 mg/kg) subcutaneously (s.c.), and the small intestine was examined for lesions 24 hr later. Dopamine (1-10 mg/kg) or atropine (3 mg/kg) was administered s.c. twice, 30 min before and 8 hr after indomethacin, while sulpiride (3 mg/kg) and domperidone (3 mg/kg), the dopamine D2 receptor antagonists, or yohimbine (10 mg/kg), the alpha2-adrenoceptor antagonist, were administered s.c. twice, 30 min before each dosing of dopamine. Intestinal motility was measured using a balloon under urethane anesthesia. RESULTS: Indomethacin caused severe lesions in the small intestine, mainly both the jejunum and ileum. The intestinal ulcerogenic response to indomethacin was dose-dependently prevented by dopamine as well as atropine. The protective effect of dopamine was almost totally antagonized by domperidone and sulpiride but not by yohimbine. On the other hand, indomethacin markedly enhanced intestinal motility, and the hypermotility response was also prevented by dopamine as well as atropine. Both sulpiride and domperidone, but not yohimbine, also antagonized the inhibitory effect of dopamine on the indomethacin-induced intestinal hypermotility. CONCLUSIONS: These results suggest that dopamine protects the small intestine against indomethacin-induced damage, probably by inhibiting the intestinal hypermotility mediated by dopamine D2 receptors.

Adrenergic alpha-Antagonists↗

PubMed2002

Expression of cyclooxygenase-2 in primary and remnant gastric carcinoma: comparing it with p53 accumulation, Helicobacter pylori infection, and vascular endothelial growth factor expression.

BACKGROUND AND OBJECTIVES: Cyclooxygenase-2 (COX-2) expression may contribute to the synthesis of prostanoids, which have been related to carcinogenesis and tumor progression. It is well known that the gastric remnant is at greater risk of the development of gastric cancer than is the whole stomach; incidence rates for gastric cardia adenocarcinoma are rising in the United States and Europe. Our objective was to determine the involvement of COX-2 in primary and remnant gastric cancer tissues as well as in adjacent noncancerous mucosa. METHODS: We investigated the expression of COX-2 in 91 human gastric cancer tissue and adjacent noncancerous mucosa samples (40 remnant gastric cancer, 37 gastric cardia cancer, and 14 gastric corpus and antrum cancer), using immunohistochemistry. In addition, p53 expression, Helicobacter pylori infection, and vascular endothelial growth factor in the tissues were evaluated by immunohistochemical staining and compared with COX-2 expression. RESULTS: There were no significant differences in clinicopathological data in the gastric cancer tissues. There was a significant relation between the expression of COX-2 and p53 in gastric cancer tissues (P = 0.0048). However, vascular endothelial growth factor expression and Helicobacter pylori infection showed no correlation with the expression of COX-2. In the case of adjacent noncancerous mucosa, the positive rate of COX-2 expression was significantly higher in the remnant gastric cancers (75.0%) than in the primary gastric cancers (25.5%) (P < 0.0001). CONCLUSIONS: This information may help in the analysis of the carcinogenesis of gastric cancer; there is also a possibility that the COX-2 selective inhibitor to the remnant gastric cancer has a chemopreventive effect.

Adult↗

PubMed2002

CdZnTe detector in diagnostic x-ray spectroscopy.

A method to utilize CdZnTe (CZT) detectors in diagnostic x-ray spectroscopy is described in this article. Spectral distortion due to transmission of primary x rays, the escape of cadmium- and tellurium-K fluorescent x rays, and tailing was severe in measured x-ray spectra. Therefore, correction for the distortion was performed with the stripping method using response functions. The response functions were calculated with the Monte Carlo method. The Hecht equation was employed to approximate the effects of carrier trapping in the calculations. The parameters in the Hecht equation, the mean-free path (lambda) of electrons and holes, were determined such that the tailing in calculated response functions fit that in measured gamma-ray spectra. Corrected x-ray spectra agreed well with the reference spectra measured with an HPGe detector. The results indicate that CZT detectors are suitable for diagnostic x-ray spectroscopy with appropriate corrections.

Algorithms↗

PubMed2002

[Canon's flat-panel detector].

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, modulation transfer function (MTF), Wiener spectrum (WS), noise equivalent quanta (NEQ) ) for Cannon's flat-panel detector (FPD), Fuji computed radiography (FCR) and screen-film (S/F) systems, respectively. First, the digital and overall characteristic curves of FPD and FCR systems were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of FPD system were better than those of FCR system a little at lower spatial frequencies than 0.8 mm(-1), but the overall MTF of FPD and FCR systems were worse than that of S/F system a little at all spatial frequencies. Third, the digital and overall WS of FPD system were similar or better than those of FCR system, but the overall WS of FPD and FCR systems were worse than that of S/F system. Fourth, the pre-sampling and overall NEQ of FPD system were better than those of FCR system a little at lower spatial frequencies than 1.6 mm(-1), but the overall NEQ of FPD and FCR systems were worse than that of S/F system at all spatial frequencies. Comparison of chest phantom images showed that the FPD produced images with quality comparable to or higher than those of the FCR system. From these results, we can expect that the FPD is useful machine by using digital image processing and so on in the radiology department.

Image Processing, Computer-Assisted↗

PubMed2002

[Hologic's Flat-Panel Detector].

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curve, Modulation Transfer Function (MTF), Wiener spectrum (WS), Noise Equivalent Quanta (NEQ) and Detective Quantum Efficiency (DQE)) for Hologic's direct type and Cannon's indirect type of Flat-Panel Detector (FPD). First, the digital and overall characteristic curves of both types of FPD were more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of the direct-type FPD system were superior to those of the indirect-type FPD system. Third, for identical exposures, the digital and overall WS of the direct-type FPD system were similar or worse than those of the indirect-type FPD system, and for larger exposure, the digital WS of the both types of FPD system were smaller, but the overall WS of the both types of FPD systems were larger. Fourth, the digital and overall NEQ and DQE of the direct-type FPD system were worse than those of the indirect-type FPD system at lower spatial frequencies than 1.75 - 2.0 mm(-1), but were worse at higher spatial frequencies than 1.75 - 2.0 mm(-1). We show radiographs made with the direct type of FPD system. Radiographs of square wave chart show the difference in MTF and contrast of the both types of FPD systems. As the result of evaluation of radiographs of chest phantom in point of noise by radiologists and radiological technologists, the direct type of FPD system needed double or more exposure dose than own standard condition, this dose was same as the indirect-type FPD system. And radiologists evaluated radiographs of human body, spatial resolution was very good, but contrast was much more likely to high at standard parameter. Therefore we have to consider exposure condition and image processing for the direct type of FPD system.

Humans↗

PubMed2002

[CR (Computed Radiography)].

Several recent studies have a questionnaire survey of many hospitals regarding the radiation exposure conditions of X-ray examinations. From the survey result the entrance surface doses (first quartile, median, third quartile and mean values) have calculated by using the Numerical Dose Determination (NDD) method. The calculated result for all types of examinations showed that the median values were lower than the mean values, whereas the median values of the results were lower than those in the NRPB 21 in England. The mean values of the results were lower than those in the NRPB 21 in England. The mean values were lower than IAEA guidance levels. The results have indicated that the medical exposure dose (entrance surface dose) is lower with Computed Radiography (CR) than with the Screen/Film (S/F) system except the case of chest radiography. In the case of chest radiography (adult patients) by CR exposure set-up using a lower voltage and high mAs than the S?F method, the entrance surface doses were 150 % of the median value for the overall examination and 160 % of the median value for orthochromatic S/F systems. A difference in patient dose among hospitals using CR system was also found. Mean entrance surface dose in CR system was 0.12 mGy in a quartile, 0.19 mGy in the middle and 0.27 mGy in the third quartile. Among the hospitals that showed higher doses of third quartile than above mentioned, dose differences of a quartile were distributed 2 to 10 times higher than mean exposure doses. Mori et al. propose guidance levels are lower than IAEA guidance levels of entrance surface doses for examinations carried out in Japanese institutions as the 3rd quartile of the dose distributions. Therefore the quality control of tube voltage, tube current and mAs and a regular measurement of exposure for X-ray units are required.

Humans↗

PubMed1999

Photoinduced Electron-Transfer Cope Rearrangements of 3,6-Diaryl-2,6-octadienes and 2,5-Diaryl-3,4-dimethyl-1,5-hexadienes: Stereospecificity and an Unexpected Formation of the Bicyclo[2.2.0]hexane Derivatives.

Under the 9,10-dicyanoanthracene-sensitized photoinduced electron-transfer conditions, (Z,Z)-, (E,E)-, (E,Z)-3,6-diaryl-2,6-octadiene and (d,l),(meso)-2,5-diaryl-3,4-dimethyl-1,5-hexadiene stereospecifically undergo the Cope rearrangement to give a Cope photostationary mixture. Remarkably, the photoinduced electron-transfer Cope rearrangements of the 4-methylphenyl derivatives are concurrent with the formation of trans- or endo,cis-1,4-bis(4-methylphenyl)-2,3-dimethylbicyclo[2.2.0]hexane in a Cope photostationary mixture. Observed stereospecificity of the Cope rearrangement and the formation of the bicyclo[2.2.0]hexane derivatives demonstrate the intermediacies of both the chair and boat 1,4-diaryl-1,2-dimethylcyclohexane-1,4-diyl and cation radical intermediates in a Cope rearrangement cycle. Photoreactions of trans- and exo,cis-1,4-diaryl-5,6-dimethyl-2,3-diazabicyclo[2.2.2]oct-2-enes further support the interventions of the diyl intermediates in the Cope rearrangement cycle. By photoacoustic analysis, a cation radical cyclization-diradical cleavage mechanism is proposed for the photoinduced electron-transfer Cope rearrangement of the title dienes.

Journal Article↗

PubMedDate not supplied

Monte Carlo calculation of depth doses for small field of CyberKnife.

PURPOSE: A Monte Carlo (MC) model of CyberKnife was developed as a quality assurance tool. The percentage depth dose (%dd) was verified by using this model. MATERIALS AND METHODS: An MC model was developed with Electron Gamma Shower version 4 (EGS4) in two steps: (1) a model of the CyberKnife treatment head and (2) a model of the collimator and phantom. The bremsstrahlung spectrum was calculated using the first model, and this spectrum was then used to calculate %dds with the second model. The calculated %dds for a large field (60 mm diameter) and three small fields (30, 15, and 5 mm diameter) were compared with those measured with a diamond detector. RESULTS AND DISCUSSION: The MC-calculated and measured %dd-curves for the 60 mm diameter field were in excellent agreement (<1.85%), thus confirming the validity of the model. Discrepancies between the calculated and measured %dd-curves increased with decreasing field size, with considerable discrepancy (11.62%) for the 5 mm diameter field due to lateral electron disequilibrium. Accurate dose can be determined with MC even in small fields. CONCLUSION: The MC technique can provide reliable standard data for accurate dose delivery with high-technology radiotherapies using small beams.

Humans↗