Development and evaluation of a new gray-scale test pattern to adjust gradients of thoracic CT imaging

Yamaguchi, Michihiro; Fujita, Hideki; Uemura, Masanobu; Asai, Yoshiyuki; Wakae, H.; Ishifuro, Minoru

doi:10.1007/s00330-004-2315-3

Cited by 8 publications

(6 citation statements)

References 13 publications

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“…A drawback of our study is the retrospective nature, which does not allow specific conclusions regarding the incidence of mediastinitis. Promising results regarding consistency and reproducibility of mediastinal density related pathology assisting in early recognition of subtle changes may be available in the near future by the recent development of a gray-scale test pattern (NGTP) [27].…”

Section: Discussionmentioning

confidence: 99%

Acute mediastinitis: spectrum of computed tomography findings

Exarhos

Malagari²,

Tsatalou

et al. 2004

Eur Radiol

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The objective of this study was to describe CT findings and to determine the diagnostic value of CT in diagnosis of acute mediastinitis. CT findings were retrospectively studied in 40 patients with suspected acute mediastinitis, including 28 postoperative patients, five with acute descending necrotizing mediastinitis (ADNM), and seven with suspected post-traumatic perforation of the esophagus. Findings included increased attenuation of mediastinal fat (100%), localized mediastinal fluid collections (55%), free gas bubbles in the mediastinum (57.5%), mediastinal lymph nodes (35%), pericardial effusions (27.5%), pleural effusions (85%), lung infiltrates (35%), sternal dehiscence (40%), and pleuromediastinal fistula (2.5%). The sensitivity and specificity of CT in postoperative patients in the first 17 days was 100% and 33% respectively, and after day 17, 100% and 90%. In patients with ADNM sensitivity was 100% while in patients with suspected esophageal perforation sensitivity and specificity were 100%. CT is a highly sensitive technique for the detection of mediastinitis of various causes. For the postoperative patients there is clear time dependence for CT interpretation and accuracy. In patients with suspected ADNM, and traumatic esophageal perforation CT is highly specific early after clinical presentation.

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Section: Discussionmentioning

confidence: 99%

Acute mediastinitis: spectrum of computed tomography findings

Exarhos

Malagari²,

Tsatalou

et al. 2004

Eur Radiol

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“…We divided the digital driving level (DDL) into 256 points for calibration. To compare the effectiveness of δ for a CT image, the DDL was converted into a CT value (HU) with an NGTP [14].…”

Section: Methodsmentioning

confidence: 99%

Psychophysical analysis of monitor display functions affecting observer diagnostic performance of CT image on liquid crystal display monitors

et al. 2005

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The aim of the present study was to propose suitable display functions for CT image representation on liquid crystal display (LCD) monitors by analyzing the characteristics of the monitor's typical display functions using psychophysical analysis. The luminance of the LCD monitor was adjusted to a maximum of 275 cd/m2 and 480 cd/m2. Three types of postcalibrated display functions (i.e., GSDF, CIELAB, and Exponential gamma 2.2) were evaluated. Luminance calculation of a new grayscale test pattern (NGTP) was done for the conversion of the digital driving level (DDL) into the CT value. The psychophysical gradient delta of display functions for the CT value was evaluated and compared via statistical analysis. The delta value of GSDF and CIE decreased exponentially; however, the delta value of Exponential gamma 2.2 showed a convex curve with a peak at a specific point. There was a statistically significant difference among the delta values of the three types of display functions on the 480 cd/m2 maximum via Kruskal Wallis test (P<0.001). The GSDF was suitable for observation of abdominal and lung CT images; however, the display function combined the Exponential gamma 2.2 and the GSDF functions and was ideal for observation of brain CT images by psychophysical analysis.

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“…To determine the AL,,in of the LCD monitor, the new greyscale test pattern (NGTP), which was developed for evaluation of the gradation characteristic of lung CT images (YAMAGUCHI et al, 2004), was used. The NGTP is made up of 256 (16 × 16) square segments without gaps, as shown in Fig.…”

Section: Comparison Of Threshold Contrastmentioning

confidence: 99%

Evaluation of grey-scale standard display function as a calibration tool for diagnostic liquid crystal display monitors using psychophysical analysis

Asai

Shintani

Yamaguchi³

et al. 2005

Med. Biol. Eng. Comput.

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The digital imaging and communications in medicine (DICOM) standard proposed the grey-scale standard display function (GSDF) as a calibration tool for making the gradation characteristic of a radiographic output image consistent. This is designed in such a manner that the contrast visually recognised by observers (called psychophysical contrast) becomes a constant for all digital driving levels. The DICOM standard calls such an ideal characteristic perceptual linearisation. The psychophysical gradient that can express the psychophysical contrast was introduced for the evaluation of the GSDF using a liquid crystal display monitor. Investigations regarding its ability to yield a constant psychophysical contrast, independent of the digital driving level change and under an actual observation environment, such as for clinical radiographic diagnosis in hospital, were carried out. The psychophysical gradients of the GSDF were obtained for two kinds of observation environment: one was a restricted environment such as in a dark room, under steady-state adaptation, using the sinusoidal grading pattern corresponding to the peak frequency of the human eye response. The other was an actual environment reflecting that encountered during clinical diagnosis in a hospital. As a result, the psychophysical gradient under the restricted environment became almost constant and independent of the change in digital driving level, i.e. perceptual linearisation could be satisfied. Furthermore, under the actual observation environment, the psychophysical gradient decreased gradually with the increase in digital driving level, i.e. the perceptual linearisation could not be satisfied. The percentage decrease in the value of the psychophysical gradient at the maximum luminance area was approximately 60% compared with that at the minimum luminance area. Accordingly, the GSDF is unsuitable as a calibration tool for the liquid crystal display monitor, which will be used in actual clinical diagnosis, as it cannot achieve 'perceptual linearisation' under the actual environment. For the purpose of clinical diagnosis, it is necessary to enlarge the physical gradient of GSDF further in the high digital driving level range (which relates to a high luminance area) to give an approximation that is as close to the idealised form as possible.

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Development and evaluation of a new gray-scale test pattern to adjust gradients of thoracic CT imaging

Cited by 8 publications

References 13 publications

Acute mediastinitis: spectrum of computed tomography findings

Acute mediastinitis: spectrum of computed tomography findings

Psychophysical analysis of monitor display functions affecting observer diagnostic performance of CT image on liquid crystal display monitors

Evaluation of grey-scale standard display function as a calibration tool for diagnostic liquid crystal display monitors using psychophysical analysis

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