Basic imaging properties of a computed radiographic system with photostimulable phosphors

Fujita, Hiroshi; Ueda, Katsuhiko; Morishita, Junji; Fujikawa, Toru; Ohtsuka, Akiyoshi; Sai, Tokugi

doi:10.1118/1.596402

Cited by 84 publications

(31 citation statements)

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“…The imaging plate had a wide dynamic range, and there was a log-linear correlation between the exposure dose and gray value, which made it useful for measurements under these conditions. [11][12][13] The scatter fractions for SODs of 150, 200, and 300 cm with no air gap were from 0.7 to 0.8, and these results are comparable to published data. 6,13,14 The linear regression fitting of the ESPS model was good, and the coefficients of determination of the fitting curves were very high, suggesting that the ESPS model is suited to cephalometric radiography.…”

Section: Discussionsupporting

confidence: 92%

Scatter radiation and the effects of air gaps in cephalometric radiography

et al. 2006

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orthodontic patients are children and adolescents, who are more sensitive to ionizing radiation than adults. In many cases, several cephalometric radiographs are taken during treatment and follow-up. Therefore, it is important that these patients be exposed to as little radiation as possible. In many facilities, cephalometric radiography is still performed using a grid to prevent image degradation, such as the decreased contrast caused by scatter radiation. The use of a grid results in increased exposure to compensate for the reduction in the radiation that reaches the detector plane. Some authors have removed the grid, 1 and introduced the air-gap technique 2 in cephalometric radiography. However, the scatter fraction, the ratio of the scatter radiation reaching the film plane to the primary radiation, with and without a grid, have been studied in cephalometric radiography in only one case. 2 In 1976, Muntz et al. 3 suggested that scatter rejection resulting from air gaps could be described using an empirical model in which the scattered radiation behaved as if it originated from an effective scatter point source (ESPS) located between the focal spot of the X-ray tube and the exit surface of the phantom (Fig. 1). Their suggestion was based on chest phantom experiments. In a subsequent paper, 4 they showed a similar tendency on mammography. In 1985, Sorenson and Floch 5 reported the effectiveness of ESPS models for various field sizes, tube voltages, and phantom thicknesses. However, these experiments did not include the parameters used in cephalometric radiography. These parameters could be explored from their results, but it is better to experiment using cephalometric radiography conditions directly. If this model is applicable to cephalometric radiography, the effectiveness of the scatter reduction for any distance of air gap could be estimated.In this study, we evaluated the use of the ESPS model for the scatter property in cephalometric radiography and estimated the scatter rejection effect of the air gap to optimize the air-gap distance. AbstractObjectives. The scatter radiation and scatter rejection effect of air gaps in cephalometric radiography were evaluated using an effective scatter point source (ESPS) model. Methods.A 16-cm-thick water-equivalent phantom was used to measure the scatter fraction. The distance from the source to the center of the object (SOD) was 150, 200, or 300 cm. The air gap was varied from 0 to 96 cm for each SOD. A photostimulable phosphor plate was used as the X-ray sensor. The measured scatter fraction ESPS model was used to simulate the scatter rejection by the air gap, and the predictions were compared with the grid. Results. There was excellent agreement between the ESPS model and the scatter measurements. The air gap reduced the scatter radiation, especially for an SOD of 200 or 300 cm, while keeping an object magnification of 1.1 in view of the signal-to-noise ratio improvement factor. Conclusions. The results suggest that a grid should not be used in cephalometric radiogr...

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Section: Discussionsupporting

confidence: 92%

Scatter radiation and the effects of air gaps in cephalometric radiography

et al. 2006

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“…As a result, the dynamic range and optimal exposure range of film are limited by the maximum optical density allowed for the film. On the other hand, a digital image utilizes a discrete numerical matrix to express an image [2]. In a digital image, the contrast is expressed by the difference in numerical pixel value compared to that of other areas of the image.…”

Section: Introductionmentioning

confidence: 99%

A Study on Image Quality Management in PACS Used by Korean Hospitals

Cho¹,

Lee²,

Dong

et al. 2012

J Digit Imaging

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This study evaluated a method to maintain the optimal image quality in clinical practice for image quality management in a picture archiving and communication system (PACS) that uses typical technology for digital medical images. This study conducted a survey of 25 hospitals in Seoul and metropolitan areas that had installed PACS to examine the reality of image quality management. Sixteen diagnostic monitors were used as calibration tools to compare and analyze the external illuminance uniformity and grayscale standard display function (GSDF) values at each frequency. According to the survey results, most of the hospitals did not have any particular rules or standardized methods for image quality control. In a PACS, the calibration frequency was examined within the allowable limits of error for each week and month. The calibration was not affected by the difference in brightness of the environment for reading an image. The GSDF measurement values were quite different from the standard values. In conclusion, to improve the image quality of the digital system, it is important to make good use of the system and maintain the image quality. Therefore, it is critical to capitalize on the method suggested in this study and maintain the optimal image quality to guarantee a high level of observer satisfaction.

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“…The MTF was calculated from the image data of the single line inclined slightly using a previously published method. 13 …”

Section: Camera Evaluationmentioning

confidence: 99%

MTF measurement method for medical displays by using a bar-pattern image

Ichikawa¹,

Kodera²,

Fujita³

2006

J. Soc. Inf. Display

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-A modulation-transfer-function (MTF) measurement method that uses a bar-pattern image for medical displays such as liquid-crystal displays (LCDs) and cathode-ray tubes (CRTs) has been investigated. A specific bar-pattern image on the display was acquired with a high-resolution singlelens reflex-type digital camera equipped with a close-up lens. The MTF was calculated from the amplitudes of the fundamental-frequency components, which were extracted from the profile data across the bar patterns by using Fourier analysis. Actual comparisons with the conventional line technique were performed for a medical CRT. The adequate accuracy and excellent reproducibility of the method were confirmed. Furthermore, unlike the line method, an advantageous feature which can use an input signal with sufficient amplitude was theoretically proved. Horizontal and vertical MTFs at the central position of the display area were measured up to the Nyquist frequency for several medical displays. From these measurements, this method has the capability to detect slight differences between the displays measured. This proposed method is useful in understanding and quantifying the medical display's performance due to excellent reproducibility and accuracy.

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Basic imaging properties of a computed radiographic system with photostimulable phosphors

Cited by 84 publications

References 0 publications

Scatter radiation and the effects of air gaps in cephalometric radiography

Scatter radiation and the effects of air gaps in cephalometric radiography

A Study on Image Quality Management in PACS Used by Korean Hospitals

MTF measurement method for medical displays by using a bar-pattern image

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