Language：English   Publishing type：Research paper (other academic)  

The method of obtaining the primary x-ray spectrum by the Compton scattering correction has been practically established for relatively high x-ray tube voltages. However, for mammography, the tube voltages are less than 30 to 35 kV and there exists an intense characteristic x-ray peak at 17.5 keV from the molybdenum target. The influence of Rayleigh scattering can not be neglected in this mammography energy range. Accurate data of Rayleigh and Compton cross sections for the scatterer material are required for obtaining the primary x-ray spectrum by correcting the scattered x-ray spectrum of mammography. The purpose of this study is to investigate the Rayleigh and Compton scattering cross sections for PMMA scatterer material in the mammography energy range theoretically and experimentally. Fluorescent x-rays of 15 to 25 keV were generated by exciting four metal targets including molybdenum by synchrotron radiation. The produced fluorescent x-rays were incident on a sphere of PMMA (polymethyl methacrylate), and scattered x-rays at 90, 120, 150, and 165 degrees, respectively, were measured with a CdTe detector. The scattered fluorescent x-ray spectrum was separated into the Rayleigh and Compton scattering peaks by using a curve fitting technique with two Gaussian functions. We compared the measured cross section data to those obtained from theoretical values. In addition, we calculated the scattered fluorescent x-ray spectra using the Monte Carlo simulation and compared them to the measured spectra. As a result, the ratio of the Rayleigh to the total scattering ratio agreed to theoretical value within 10%. The shapes of the scattered spectra calculated by Monte Carlo simulation agreed fairly well with those of measured spectra.

DOI： 10.1007/978-3-642-03879-2-66

Language：English   Publishing type：Research paper (other academic)  

The analysis of the x-ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system such as mammography. In the case of mammography, the direct measurement of the primary x-ray spectra under clinical conditions is very difficult and time-consuming mainly because it is almost impossible to increase the longitudinal distance between the focal spot and x-ray detector in order to make the photon counting measurement possible. An alternative way of measuring the primary spectra is to correct the 90 degree scattered x-ray spectra which can be measured without photon pile-up since the intensity of the scattered x-rays is significantly lowered. The scattered x-ray spectrum is composed of two components, Compton scattered photons and Rayleigh scattered photons. We have developed a new method of reconstructing the primary x-ray spectrum from the scattered x-ray spectrum taking into account both Rayleigh and Compton scattered photons . The 90 degree scattered x-ray spectrum from a 28 kV mammography x-ray unit was measured at a tube voltage by using a CdTe semiconductor detector. The reconstructed spectrum agreed fairly well with a directly measured primary x-ray spectrum. The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x-ray spectra under clinical conditions and useful for QA and QC of the mammography x-ray units.

DOI： 10.1007/978-3-642-03879-2-65

Language：English  

DOI： 10.6009/jjrt.65.1109

Language：English  

Purpose: The method of obtaining the primary x‐ray spectrum by the Compton scattering correction has been established for relatively high x‐ray tube voltages. However, the influence of Rayleigh scattering can not be neglected in the mammography energy range. Besides, accurate data of Rayleigh and Compton cross sections for the scatterer material are required for obtaining the primary x‐ray spectrum by correcting the scattered x‐ray spectrum in mammography. The purpose of this study is to investigate theoretically and experimentally the relative contributions of Rayleigh scattering for PMMA (polymethyl methacrylate) in the mammography energy range. Method and Materials: Fluorescent x‐rays in the energy range of 10 to 25 keV were generated by exciting four metal targets including molybdenum by synchrotron radiation. The fluorescent x‐rays were incident on a sphere of PMMA, and the scattered x‐rays were measured with a CdTe detector at scattering angles of 90, 120, 150, 165 degrees. The scattered fluorescent x‐ray spectrum was separated into the Rayleigh and Compton scattering peaks by using a curve fitting technique with two Gaussian functions. We compared the measured cross section data to those obtained from theoretical values. We also calculated the scattered fluorescent x‐ray spectra using the Monte Carlo simulation and compared them to the measured spectra. Results: The measured ratio of Rayleigh to total scattering cross section was about 30% at 10 keV. The maximum discrepancy of the measured and theoretically calculated values of the ratio was about 30% for the scattering angles of 90 to 165 degrees. However, at the angle of 120 degrees where the overall error might be minimum, the theoretical and experimental values agreed within 2%. Conclusion: Rayleigh and Compton scattering cross sections should be measured more precisely in order to improve the calculation of the primary mammography x‐ray spectrum from the scattered x‐ray spectrum.

DOI： 10.1118/1.3181185

Language：English  

Purpose: An analysis of the x‐ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system. In the case of mammography, the direct measurement of the primary x‐ray spectra under clinical conditions is very difficult and time‐consuming. The method of obtaining the primary x‐ray spectrum by the Compton scattering correction has been established for relatively high x‐ray tube voltages. However, the influence of Rayleigh scattering can not be neglected for mammography. We have developed a new method of reconstructing the primary x‐ray spectrum from the scattered x‐ray spectrum taking into account both Rayleigh and Compton scattering. Method and Materials: The primary x‐ray beam from a 28 kV mammography x‐ray unit was incident on a PMMA (polymethyl methacrylate) sphere scatterer with a diameter of 6 mm. The 90‐degree scattered x‐ray spectrum was measured by using a CdTe semiconductor detector. The measured x‐ray spectrum was separated into three energy regions, and the characteristic x‐ray peaks and bremsstrahlung x‐rays were fitted by Gaussian and quadratic functions. The energy shift corrections of the Compton and Rayleigh components were made at each photon energy channel by splitting the number of photons at each channel into the two scattering components according to the corresponding cross sections. The Monte Carlo simulation of the 90‐degree scattered x‐ray spectra were also performed using the EGS5 code. Results: The reconstructed spectrum agreed fairly well with a directly measured primary x‐ray spectrum. In the Monte Carlo simulation, the scattered x‐ray spectrum calculated for the incidence of the reconstructed x‐ray spectrum showed a very good agreement to the measured scattered x‐ray spectrum. Conclusions: The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x‐ray spectra under clinical conditions and useful for QA and QC of the mammography x‐ray units.

DOI： 10.1118/1.3181174

Language：English  

In the last several years most diagnostic imaging systems which were screen-film systems have been replaced with digital systems. However, mammography has not advanced as much toward digitization. The most important factor against digitization of mammography is detectability of micro-calcifications, which are essential in diagnosing breast cancer. Digital images have low special resolution relative to screen-film for the limited pixel sizes. Recently, with the aim of improving this situation, high resolution CR systems with a pixel size of 50μm (half the pixel size of conventional CR systems) and full field digital mammography systems with a flat-panel-detector (FPD) pixel size of 100μm have been developed and made commercially available. In this report, we describe the current state of digital imaging system development for mammography. The purpose of this report is to survey the future of digital mammography from comparisons of the results of the physical imaging properties and contrast-detail characteristics between digital mammography (FPD and high resolution CR) and screen-film (Min-R2000/Min-R2000) systems.

Language：English  

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.

DOI： 10.6009/jjrt.62.425

Language：English  

In mammography units, the X-ray tube focal spot is located directly above the chest wall edge of the detector. Therefore, the X-ray beam is incident at a different angle along the cathode-anode axis. When the X-ray beam is incident on the imaging plate (IP) at a relatively large angle, the resolution property of a new imaging plate with dual-sided reading system would be degraded compared with the conventional imaging plate because of the parallax effect, which produces a shift in the image on two sides of the imaging plate. To evaluate the oblique incidence effect of the X-ray beam on the degradation of resolution properties and detection of simulated microcalcifications of a new CR system with a pixel size of 50 microm, its basic imaging properties and observer performance tests were compared with those of a conventional CR system. The resolution properties were evaluated by measuring modulation transfer functions (MTFs). Observer performance tests were conducted to compare the detectability of simulated microcalcifications of CR systems. Degradation of presampling MTFs for the new system is greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate. We found that the degradation of the area under the ROC curve (Az) for the new CR system was greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate.

DOI： 10.6009/jjrt.KJ00003326844

Language：English  

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.

DOI： 10.6009/jjrt.KJ00004017357

Language：English  

Purpose: To demonstrate the clinical usefulness of a temporal subtraction technique for the detection of interval changes in various interstitial lung diseases on digital chest radiographs. Materials and Methods: One hundred pairs of chest radiographs in 34 patients (63 with and 37 without interval changes) with various interstitial lung diseases were selected. All cases were confirmed by serial chest computed tomography (CT) and ascertained by radiologists. All chest radiographs were obtained with a computed radiography (CR) system, and temporal subtraction images were produced with an iterative image-warping technique. Four radiologists and two thoracic physicians provided confidence levels for interval changes in interstitial lung diseases with and without temporal subtraction. Their performances with and without temporal subtraction were evaluated by means of receiver operating characteristic (ROC) analysis using a sequential test. Results: The area under the ROC curve (Az) values of six observers obtained with and without temporal subtraction were 0.90 and 0.78, respectively. Results showed that the detection of interval changes in interstitial lung diseases was significantly improved by the use of temporal subtraction images compared with CR images alone (P=0.002), Furthermore, the high detection rate was achieved with temporal subtraction images regardless of the subtlety and location of interval changes. Conclusion: Temporal subtraction improved the diagnostic accuracy of radiologists in detecting interval changes in interstitial lung diseases on chest radiographs. It was also useful for cases of multiple interval changes.

Language：English  

The physical characteristics of a clinical amorphous silicon-based flat-panel imager for full-field digital mammography were investigated. Pre-sampled modulation transfer functions (MTF) were measured by using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform. The MTFs of full-field digital mammography systems showed significantly higher values than those of the computed radiography (CR) system. The full-field digital mammography system showed a lower noise level than that of the CR system under the same exposure conditions. Contrast detail analysis has been performed to compare the detectability of the full-field digital mammography system with that of the screen-film (Min-R 2000/Min-R 2000) system. 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 the digital contrast-detail curves and IQF, on average, are superior to those of the screen-film system.

DOI： 10.6009/jjrt.KJ00000922344

Language：English  

Purpose: To investigate the physical imaging properties and detection of simulated microcalcifications of a new computed radiography (CR) system with a pixel size of 50μm for digital mammography. Materials and Methods: New and conventional CR were employed in this study. The new CR system included a high-resolution imaging plate coupled with the FCR5000MA (50μm pixel pitch) including transparent support and a dual-sided reader. The conventional CR system was coupled with the FCR9000 (100μm pixel pitch). Modulation transfer functions (MTFs) and Wiener spectra (WS) of the new and conventional CR systems were measured. Observer performance tests were conducted to compare the effects of pixel size (50μm vs. 100μm) on the diagnostic accuracy of CR systems in the detection of simulated microcalcifications. Results: The presampling MTF of the new CR system was higher at high frequencies than the conventional CR system. The WS of the new CR system was comparable to that of the conventional CR system at all frequencies. The area under the receiver operating characteristic (ROC) curve (Az) obtained with the new CR and the conventional CR systems were 0.84 and 0.79, respectively. Results showed that the detection of simulated clustered microcalcifications was significantly improved by use of the new CR system compared with the conventional CR system (p<0.05). Conclusion: The new CR mammography system improved physical imaging properties and detection of simulated microcalcifications over conventional CR mammography.

Language：English  

In otorthinolaryngology, Stenvers' method is employed in radiography of the pyramid (internal acoustic meatus and semicircular canals). However, in cases of dizziness, where the prone position is difficult to achieve, we occasionally use the opposite Stenvers' method instead of the conventional one. This makes it possible to perform radiography with the patient in the supine position. Compared with the conventional Stenvers' method, the problems of this method were increases not only in the rate of magnification but also in lens dose. In this study, we evaluated these problems by employing computed tomography (CT) and a glass dosimeter with phantom as well as by clinical evaluation. The results showed no statistically significant difference between Stenvers' method and the opposite Stenvers' method in both the rate of magnification and the clinical evaluation. The increase in lens dose with the opposite Stenvers' method was not significant. We concluded that the opposite Stenvers' method was useful.

DOI： 10.6009/jjrt.KJ00003174217

Language：English   Publishing type：Research paper (scientific journal)  

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.

Language：English  

In A department of radiology, we have three fields of radiodiagnosis, nuclear medicine and radiotherapy. We use various medical equipments for patient in clinical examination. It is the truth that every material in various forms breakes certainly. Though medical equipments usually seem to be safe, suddenly they may cause an accident during clinical examination and they may do patient an injury. As medical accidents, unexpected incidents, near miss of medical accidents and complaints from patient caused by inevitability and medical malpractice may happen in daily clinical examination, we must prevent and minimize medical accidents. We sent out questionaries to 13 hospitals to get accident cases caused during clinical examination. We study risk management for prevention of patient's injury. In this paper, we discuss risk cases due to mistake of receptionist, plain radiographic techniques, ward radiographic techniques, contrast radiographic techniques and angiography.

DOI： 10.11261/iryo1946.52.554

Language：English  

We use many modalities of medical equipment in the department of radiology, but medical accidents, unexpected incidents, and near miss of medical accidents may be caused by inevitability and medical malpractice. We must prevent medical accidents during clinical examination. So, we investigate and analyze various risk cases in the department of radiology, and we study risk management for prevention of patient's injury. In this paper, we discuss risk cases due to computed tomography, magnetic resonance imaging, nuclear medicine, radiotherapy and ultrasonograpy.

DOI： 10.11261/iryo1946.52.601

Language：English  

We must introduce risk management for prevention of medical accidents in clinical examination. It is a useful method for prevention of patient's harm or injury to investigate and analyze various risk cases in many facilities. Though the main cause of medical troubles depend on medical accidents, unexpected incidents, and others, it is also useful for prevention of medical trouble to respond to patient's questions and complaints. So, we investigate and analyze various risk cases in the department of radiology. In this paper, we discuss medical troubles due to patient's question and complaint.

DOI： 10.11261/iryo1946.52.664

Responsible for pages：P120-P124   Language：Japanese   Book type：Scholarly book

Responsible for pages：231-233   Language：English  

The analysis of the x-ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system such as mammography. In the case of mammography, the direct measurement of the primary x-ray spectra under clinical conditions is very difficult and time-consuming mainly because it is almost impossible to increase the longitudinal distance between the focal spot and x-ray detector in order to make the photon counting measurement possible. An alternative way of measuring the primary spectra is to correct the 90 degree scattered x-ray spectra which can be measured without photon pile-up since the intensity of the scattered x-rays is significantly lowered. The scattered x-ray spectrum is composed of two components, Compton scattered photons and Rayleigh scattered photons. We have developed a new method of reconstructing the primary x-ray spectrum from the scattered x-ray spectrum taking into account both Rayleigh and Compton scattered photons . The 90 degree scattered x-ray spectrum from a 28 kV mammography x-ray unit was measured at a tube voltage by using a CdTe semiconductor detector. The reconstructed spectrum agreed fairly well with a directly measured primary x-ray spectrum. The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x-ray spectra under clinical conditions and useful for QA and QC of the mammography x-ray units.

DOI： 10.1007/978-3-642-03879-2-65

Responsible for pages：234-237   Language：English  

The method of obtaining the primary x-ray spectrum by the Compton scattering correction has been practically established for relatively high x-ray tube voltages. However, for mammography, the tube voltages are less than 30 to 35 kV and there exists an intense characteristic x-ray peak at 17.5 keV from the molybdenum target. The influence of Rayleigh scattering can not be neglected in this mammography energy range. Accurate data of Rayleigh and Compton cross sections for the scatterer material are required for obtaining the primary x-ray spectrum by correcting the scattered x-ray spectrum of mammography. The purpose of this study is to investigate the Rayleigh and Compton scattering cross sections for PMMA scatterer material in the mammography energy range theoretically and experimentally. Fluorescent x-rays of 15 to 25 keV were generated by exciting four metal targets including molybdenum by synchrotron radiation. The produced fluorescent x-rays were incident on a sphere of PMMA (polymethyl methacrylate), and scattered x-rays at 90, 120, 150, and 165 degrees, respectively, were measured with a CdTe detector. The scattered fluorescent x-ray spectrum was separated into the Rayleigh and Compton scattering peaks by using a curve fitting technique with two Gaussian functions. We compared the measured cross section data to those obtained from theoretical values. In addition, we calculated the scattered fluorescent x-ray spectra using the Monte Carlo simulation and compared them to the measured spectra. As a result, the ratio of the Rayleigh to the total scattering ratio agreed to theoretical value within 10%. The shapes of the scattered spectra calculated by Monte Carlo simulation agreed fairly well with those of measured spectra.

DOI： 10.1007/978-3-642-03879-2-66

Event date： 2023.4

Language：Japanese  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2023.4

Language：Japanese  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2023.4

Language：Japanese  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2023.4

Language：Japanese  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2023.4

Language：Japanese  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2023.2 - 2023.3

Language：English  

Venue：Vienna   Country：Austria  

Event date： 2022.12 - 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：佐賀市   Country：Japan  

Event date： 2022.11

Language：Japanese  

Venue：福岡市（アクロス福岡）   Country：Japan  

Event date： 2022.11

Language：Japanese  

Venue：福岡市（アクロス福岡）   Country：Japan  

Event date： 2022.11

Language：Japanese  

Venue：福岡市（アクロス福岡）   Country：Japan  

Event date： 2022.11

Language：Japanese  

Venue：福岡市（アクロス福岡）   Country：Japan  

Event date： 2022.11

Language：Japanese  

Venue：福岡市（アクロス福岡）   Country：Japan  

Event date： 2022.4

Language：English  

Venue：Yokohama Japan   Country：Japan  

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：佐賀市   Country：Japan  

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：佐賀市   Country：Japan  

Event date： 2021.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：熊本市   Country：Japan  

Event date： 2021.5

Language：English   Presentation type：Oral presentation (general)  

Venue：Seoul   Country：Korea, Republic of  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎市   Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎市   Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎市   Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：長崎市   Country：Japan  

Event date： 2009.9

Language：English  

Venue：Munich   Country：Germany  

The analysis of the x-ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system such as mammography. In the case of mammography, the direct measurement of the primary x-ray spectra under clinical conditions is very difficult and time-consuming mainly because it is almost impossible to increase the longitudinal distance between the focal spot and x-ray detector in order to make the photon counting measurement possible. An alternative way of measuring the primary spectra is to correct the 90 degree scattered x-ray spectra which can be measured without photon pile-up since the intensity of the scattered x-rays is significantly lowered. The scattered x-ray spectrum is composed of two components, Compton scattered photons and Rayleigh scattered photons. We have developed a new method of reconstructing the primary x-ray spectrum from the scattered x-ray spectrum taking into account both Rayleigh and Compton scattered photons . The 90 degree scattered x-ray spectrum from a 28 kV mammography x-ray unit was measured at a tube voltage by using a CdTe semiconductor detector. The reconstructed spectrum agreed fairly well with a directly measured primary x-ray spectrum. The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x-ray spectra under clinical conditions and useful for QA and QC of the mammography x-ray units.

Event date： 2009.9

Language：English  

Venue：Munich   Country：Germany  

The method of obtaining the primary x-ray spectrum by the Compton scattering correction has been practically established for relatively high x-ray tube voltages. However, for mammography, the tube voltages are less than 30 to 35 kV and there exists an intense characteristic x-ray peak at 17.5 keV from the molybdenum target. The influence of Rayleigh scattering can not be neglected in this mammography energy range. Accurate data of Rayleigh and Compton cross sections for the scatterer material are required for obtaining the primary x-ray spectrum by correcting the scattered x-ray spectrum of mammography. The purpose of this study is to investigate the Rayleigh and Compton scattering cross sections for PMMA scatterer material in the mammography energy range theoretically and experimentally. Fluorescent x-rays of 15 to 25 keV were generated by exciting four metal targets including molybdenum by synchrotron radiation. The produced fluorescent x-rays were incident on a sphere of PMMA (polymethyl methacrylate), and scattered x-rays at 90, 120, 150, and 165 degrees, respectively, were measured with a CdTe detector. The scattered fluorescent x-ray spectrum was separated into the Rayleigh and Compton scattering peaks by using a curve fitting technique with two Gaussian functions. We compared the measured cross section data to those obtained from theoretical values. In addition, we calculated the scattered fluorescent x-ray spectra using the Monte Carlo simulation and compared them to the measured spectra. As a result, the ratio of the Rayleigh to the total scattering ratio agreed to theoretical value within 10%. The shapes of the scattered spectra calculated by Monte Carlo simulation agreed fairly well with those of measured spectra.

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：Japanese  

Language：English  

Language：English  

Purpose: An analysis of the x‐ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system. In the case of mammography, the direct measurement of the primary x‐ray spectra under clinical conditions is very difficult and time‐consuming. The method of obtaining the primary x‐ray spectrum by the Compton scattering correction has been established for relatively high x‐ray tube voltages. However, the influence of Rayleigh scattering can not be neglected for mammography. We have developed a new method of reconstructing the primary x‐ray spectrum from the scattered x‐ray spectrum taking into account both Rayleigh and Compton scattering. Method and Materials: The primary x‐ray beam from a 28 kV mammography x‐ray unit was incident on a PMMA (polymethyl methacrylate) sphere scatterer with a diameter of 6 mm. The 90‐degree scattered x‐ray spectrum was measured by using a CdTe semiconductor detector. The measured x‐ray spectrum was separated into three energy regions, and the characteristic x‐ray peaks and bremsstrahlung x‐rays were fitted by Gaussian and quadratic functions. The energy shift corrections of the Compton and Rayleigh components were made at each photon energy channel by splitting the number of photons at each channel into the two scattering components according to the corresponding cross sections. The Monte Carlo simulation of the 90‐degree scattered x‐ray spectra were also performed using the EGS5 code. Results: The reconstructed spectrum agreed fairly well with a directly measured primary x‐ray spectrum. In the Monte Carlo simulation, the scattered x‐ray spectrum calculated for the incidence of the reconstructed x‐ray spectrum showed a very good agreement to the measured scattered x‐ray spectrum. Conclusions: The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x‐ray spectra under clinical conditions and useful for QA and QC of the mammography x‐ray units.

DOI： 10.1118/1.3181174

Language：English  

In the last several years most diagnostic imaging systems which were screen-film systems have been replaced with digital systems. However, mammography has not advanced as much toward digitization. The most important factor against digitization of mammography is detectability of micro-calcifications, which are essential in diagnosing breast cancer. Digital images have low special resolution relative to screen-film for the limited pixel sizes. Recently, with the aim of improving this situation, high resolution CR systems with a pixel size of 50μm (half the pixel size of conventional CR systems) and full field digital mammography systems with a flat-panel-detector (FPD) pixel size of 100μm have been developed and made commercially available. In this report, we describe the current state of digital imaging system development for mammography. The purpose of this report is to survey the future of digital mammography from comparisons of the results of the physical imaging properties and contrast-detail characteristics between digital mammography (FPD and high resolution CR) and screen-film (Min-R2000/Min-R2000) systems.

Language：English  

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.

DOI： 10.6009/jjrt.62.425

Language：English  

In mammography units, the X-ray tube focal spot is located directly above the chest wall edge of the detector. Therefore, the X-ray beam is incident at a different angle along the cathode-anode axis. When the X-ray beam is incident on the imaging plate (IP) at a relatively large angle, the resolution property of a new imaging plate with dual-sided reading system would be degraded compared with the conventional imaging plate because of the parallax effect, which produces a shift in the image on two sides of the imaging plate. To evaluate the oblique incidence effect of the X-ray beam on the degradation of resolution properties and detection of simulated microcalcifications of a new CR system with a pixel size of 50 microm, its basic imaging properties and observer performance tests were compared with those of a conventional CR system. The resolution properties were evaluated by measuring modulation transfer functions (MTFs). Observer performance tests were conducted to compare the detectability of simulated microcalcifications of CR systems. Degradation of presampling MTFs for the new system is greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate. We found that the degradation of the area under the ROC curve (Az) for the new CR system was greater than that of the conventional CR system when the X-ray beam was incident at the same angle on the imaging plate.

DOI： 10.6009/jjrt.KJ00003326844

Language：English  

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.

DOI： 10.6009/jjrt.KJ00004017357

Language：English  

Purpose: To demonstrate the clinical usefulness of a temporal subtraction technique for the detection of interval changes in various interstitial lung diseases on digital chest radiographs. Materials and Methods: One hundred pairs of chest radiographs in 34 patients (63 with and 37 without interval changes) with various interstitial lung diseases were selected. All cases were confirmed by serial chest computed tomography (CT) and ascertained by radiologists. All chest radiographs were obtained with a computed radiography (CR) system, and temporal subtraction images were produced with an iterative image-warping technique. Four radiologists and two thoracic physicians provided confidence levels for interval changes in interstitial lung diseases with and without temporal subtraction. Their performances with and without temporal subtraction were evaluated by means of receiver operating characteristic (ROC) analysis using a sequential test. Results: The area under the ROC curve (Az) values of six observers obtained with and without temporal subtraction were 0.90 and 0.78, respectively. Results showed that the detection of interval changes in interstitial lung diseases was significantly improved by the use of temporal subtraction images compared with CR images alone (P=0.002), Furthermore, the high detection rate was achieved with temporal subtraction images regardless of the subtlety and location of interval changes. Conclusion: Temporal subtraction improved the diagnostic accuracy of radiologists in detecting interval changes in interstitial lung diseases on chest radiographs. It was also useful for cases of multiple interval changes.

Language：English  

The physical characteristics of a clinical amorphous silicon-based flat-panel imager for full-field digital mammography were investigated. Pre-sampled modulation transfer functions (MTF) were measured by using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform. The MTFs of full-field digital mammography systems showed significantly higher values than those of the computed radiography (CR) system. The full-field digital mammography system showed a lower noise level than that of the CR system under the same exposure conditions. Contrast detail analysis has been performed to compare the detectability of the full-field digital mammography system with that of the screen-film (Min-R 2000/Min-R 2000) system. 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 the digital contrast-detail curves and IQF, on average, are superior to those of the screen-film system.

DOI： 10.6009/jjrt.KJ00000922344

Language：English  

Purpose: To investigate the physical imaging properties and detection of simulated microcalcifications of a new computed radiography (CR) system with a pixel size of 50μm for digital mammography. Materials and Methods: New and conventional CR were employed in this study. The new CR system included a high-resolution imaging plate coupled with the FCR5000MA (50μm pixel pitch) including transparent support and a dual-sided reader. The conventional CR system was coupled with the FCR9000 (100μm pixel pitch). Modulation transfer functions (MTFs) and Wiener spectra (WS) of the new and conventional CR systems were measured. Observer performance tests were conducted to compare the effects of pixel size (50μm vs. 100μm) on the diagnostic accuracy of CR systems in the detection of simulated microcalcifications. Results: The presampling MTF of the new CR system was higher at high frequencies than the conventional CR system. The WS of the new CR system was comparable to that of the conventional CR system at all frequencies. The area under the receiver operating characteristic (ROC) curve (Az) obtained with the new CR and the conventional CR systems were 0.84 and 0.79, respectively. Results showed that the detection of simulated clustered microcalcifications was significantly improved by use of the new CR system compared with the conventional CR system (p<0.05). Conclusion: The new CR mammography system improved physical imaging properties and detection of simulated microcalcifications over conventional CR mammography.

Language：English  

In otorthinolaryngology, Stenvers' method is employed in radiography of the pyramid (internal acoustic meatus and semicircular canals). However, in cases of dizziness, where the prone position is difficult to achieve, we occasionally use the opposite Stenvers' method instead of the conventional one. This makes it possible to perform radiography with the patient in the supine position. Compared with the conventional Stenvers' method, the problems of this method were increases not only in the rate of magnification but also in lens dose. In this study, we evaluated these problems by employing computed tomography (CT) and a glass dosimeter with phantom as well as by clinical evaluation. The results showed no statistically significant difference between Stenvers' method and the opposite Stenvers' method in both the rate of magnification and the clinical evaluation. The increase in lens dose with the opposite Stenvers' method was not significant. We concluded that the opposite Stenvers' method was useful.

DOI： 10.6009/jjrt.KJ00003174217

Language：English  

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.

Language：English  

In A department of radiology, we have three fields of radiodiagnosis, nuclear medicine and radiotherapy. We use various medical equipments for patient in clinical examination. It is the truth that every material in various forms breakes certainly. Though medical equipments usually seem to be safe, suddenly they may cause an accident during clinical examination and they may do patient an injury. As medical accidents, unexpected incidents, near miss of medical accidents and complaints from patient caused by inevitability and medical malpractice may happen in daily clinical examination, we must prevent and minimize medical accidents. We sent out questionaries to 13 hospitals to get accident cases caused during clinical examination. We study risk management for prevention of patient's injury. In this paper, we discuss risk cases due to mistake of receptionist, plain radiographic techniques, ward radiographic techniques, contrast radiographic techniques and angiography.

DOI： 10.11261/iryo1946.52.554

Language：English  

We use many modalities of medical equipment in the department of radiology, but medical accidents, unexpected incidents, and near miss of medical accidents may be caused by inevitability and medical malpractice. We must prevent medical accidents during clinical examination. So, we investigate and analyze various risk cases in the department of radiology, and we study risk management for prevention of patient's injury. In this paper, we discuss risk cases due to computed tomography, magnetic resonance imaging, nuclear medicine, radiotherapy and ultrasonograpy.

DOI： 10.11261/iryo1946.52.601

Language：English  

We must introduce risk management for prevention of medical accidents in clinical examination. It is a useful method for prevention of patient's harm or injury to investigate and analyze various risk cases in many facilities. Though the main cause of medical troubles depend on medical accidents, unexpected incidents, and others, it is also useful for prevention of medical trouble to respond to patient's questions and complaints. So, we investigate and analyze various risk cases in the department of radiology. In this paper, we discuss medical troubles due to patient's question and complaint.

DOI： 10.11261/iryo1946.52.664

Type：Competition, symposium, etc. 

researchmap

Type：Competition, symposium, etc. 

Number of participants：55

Type：Competition, symposium, etc. 

Number of participants：55

Type：Competition, symposium, etc. 

researchmap

Type：Competition, symposium, etc. 

Number of participants：80

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：2

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：2

Proceedings of domestic conference Number of peer-reviewed papers：10

Type：Peer review 

Proceedings of domestic conference Number of peer-reviewed papers：20

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Proceedings of domestic conference Number of peer-reviewed papers：20

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Type：Competition, symposium, etc. 

Number of participants：13,000

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Type：Academic society, research group, etc. 

Type：Competition, symposium, etc. 

Number of participants：13,000

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Type：Competition, symposium, etc. 

Number of participants：500

Type：Peer review 

Number of peer-reviewed articles in Japanese journals：1

Type：Competition, symposium, etc. 

Number of participants：150