• 비파괴검사학회지
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• 제9권1호
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• pp.83-89
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• 1989

Effects of the microstructure and the testing conditions for the detectability of the small flaw in ultrasonic testing have been studied. The detectability of the flaw was influenced not only by the grain size but also by the microstructure of the test piece. This is considered to be caused by randomization of the matrix which influences the elastic anisotropy of the grain. It was found that the detectability was improved as the frequence became higher and the beam size became smaller. The experimental results indicate that ultrasonic backscattering measurement is one of the promising methods to evaluate the detectability of the flaw indirectly.

• 치과방사선
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• 제24권2호
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• pp.305-316
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• 1994

The comparative detectability of the artificial defects among conventional radiographs, digital images and digital subtraction images was evaluated. The artificial defects were made within spogy bone of 24 unilateral mandibles of adult dogs. The results were as follows: 1. With normal exposure time, the detectability of digital subtraction radiographs was 90.3% which was statistically significant superior to those of conventional radiographs(78.0%) and digital images(75.9%) (p<0.05). 2. With half-exposure time, the detectability of conventional radiographs, digital images and digital subtraction radiographs was 68.4%, 67.3% and 69.9% respectively. There was no statistical significant difference among the detectability of these methods(p>0.05). 3. All radiographic images with normal exposure time showed statistically significant superior detectability to those with half-exposure time(p<0.05). 4. The detectability of digital subtraction radiographs was not linearly related to the standard deviation of the grey levels of reference line(p<0.05).

• Korean Journal of Radiology
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• 제20권1호
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• pp.58-68
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• 2019

Objective: To compare digital breast tomosynthesis (DBT) and conventional full-field digital mammography (FFDM) in the detectability of breast cancers in patients with dense breast tissue, and to determine the influencing factors in the detection of breast cancers using the two techniques. Materials and Methods: Three blinded radiologists independently graded cancer detectability of 300 breast cancers (288 women with dense breasts) on DBT and conventional FFDM images, retrospectively. Hormone status, histologic grade, T stage, and breast cancer subtype were recorded to identify factors affecting cancer detectability. The Wilcoxon signed-rank test was used to compare cancer detectability by DBT and conventional FFDM. Fisher's exact tests were used to determine differences in cancer characteristics between detectability groups. Kruskal-Wallis tests were used to determine whether the detectability score differed according to cancer characteristics. Results: Forty breast cancers (13.3%) were detectable only with DBT; 191 (63.7%) breast cancers were detected with both FFDM and DBT, and 69 (23%) were not detected with either. Cancer detectability scores were significantly higher for DBT than for conventional FFDM (median score, 6; range, 0-6; p < 0.001). The DBT-only cancer group had more invasive lobular-type breast cancers (22.5%) than the other two groups (i.e., cancer detected on both types of image [both-detected group], 5.2%; cancer not detected on either type of image [both-non-detected group], 7.3%), and less detectability of ductal carcinoma in situ (5% vs. 16.8% [both-detected group] vs. 27.5% [both-non-detected group]). Low-grade cancers were more often detected in the DBT-only group than in the both-detected group (22.5% vs. 10%, p = 0.026). Human epidermal growth factor receptor-2 (HER-2)-negative cancers were more often detected in the DBT-only group than in the both-detected group (92.3% vs. 70.5%, p = 0.004). Cancers surrounded by mostly glandular tissue were detected less often in the DBT only group than in the both-non-detected group (10% vs. 31.9%, p = 0.016). DBT cancer detectability scores were significantly associated with cancer type (p = 0.012), histologic grade (p = 0.013), T and N stage (p = 0.001, p = 0.024), proportion of glandular tissue surrounding lesions (p = 0.013), and lesion type (p < 0.001). Conclusion: Invasive lobular, low-grade, or HER-2-negative cancer is more detectable with DBT than with conventional FFDM in patients with dense breasts, but cancers surrounded by mostly glandular tissue might be missed with both techniques.

• 치과방사선
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• 제27권2호
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• pp.117-125
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• 1997

The purpose of this study was to evaluate the detectability of various radiographic techniques for mandibular condylar lesions. Erosive lesion, osteophyte and flattening were formed on the artificial mandibular condyle, and panoramic, transcranial, transorbital radiography, lateral and frontal tomography were taken. The results were as follows; 1. The detectability for erosive lesions was superior in the order of frontal tomography(96％), lateral tomography(78％), transorbital(59％), transcranial(16％) and panoramic(48％) radiography. 2. The location of erosive lesion that showed the highest detectability was the medial third in panoramic, the lateral third in transcranial, the central portion of anteroposterior direction in transorbital, the central portion of mediolateral direction and the posterior third in lateral tomography. Frontal tomography disclosed all erosive lesions except one anterolateral lesion. 3. The detectability of osteophyte was 100％ in lateral tomography, 78％ in transcranial and 56％ in panoramic radiography. 4. For flattening, lateral tomography showed the flattened condyle, but both panoramic and transcranial views showed only decreased bone density without the change of condylar shape.

• 대한기계학회논문집A
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• 제41권10호
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• pp.923-929
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• 2017

모터로 구동되는 전기자동차에서 발생하는 소리의 특징은 일반적으로 내연기관 자동차보다 음압이 낮아, 보행자에게 접근하는 차량을 인지 못하는 경우가 종종 발생한다. 따라서 전기자동차에 추가적인 경고음이 필요하다. 잘 들리는 경고음을 개발하기 위해, 이번 연구에서는 화성학 이론과 신호처리를 기초로 제작하였다. 도로에서 측정된 배경소음은 합성된 신호에 추가되었다. 주관적 평가로 이 경고음의 인지성을 측정하였다. 심리음향 이론과 주관적 평가를 통해 인지성과 관련된 요소를 조사하였다. 라우드니스, 샤프니스, 러프니스 등 알려져 있는 심리음향 지표는 인지성과 낮은 상관성을 가졌지만, 반대로 음의 지속구간에 높은 상관성이 있음을 발견하였다.

• Korean Journal of Radiology
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• 제23권4호
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• pp.402-412
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• 2022

Objective: To evaluate the image quality and lesion detectability of lower-dose CT (LDCT) of the abdomen and pelvis obtained using a deep learning image reconstruction (DLIR) algorithm compared with those of standard-dose CT (SDCT) images. Materials and Methods: This retrospective study included 123 patients (mean age ± standard deviation, 63 ± 11 years; male:female, 70:53) who underwent contrast-enhanced abdominopelvic LDCT between May and August 2020 and had prior SDCT obtained using the same CT scanner within a year. LDCT images were reconstructed with hybrid iterative reconstruction (h-IR) and DLIR at medium and high strengths (DLIR-M and DLIR-H), while SDCT images were reconstructed with h-IR. For quantitative image quality analysis, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured in the liver, muscle, and aorta. Among the three different LDCT reconstruction algorithms, the one showing the smallest difference in quantitative parameters from those of SDCT images was selected for qualitative image quality analysis and lesion detectability evaluation. For qualitative analysis, overall image quality, image noise, image sharpness, image texture, and lesion conspicuity were graded using a 5-point scale by two radiologists. Observer performance in focal liver lesion detection was evaluated by comparing the jackknife free-response receiver operating characteristic figures-of-merit (FOM). Results: LDCT (35.1% dose reduction compared with SDCT) images obtained using DLIR-M showed similar quantitative measures to those of SDCT with h-IR images. All qualitative parameters of LDCT with DLIR-M images but image texture were similar to or significantly better than those of SDCT with h-IR images. The lesion detectability on LDCT with DLIR-M images was not significantly different from that of SDCT with h-IR images (reader-averaged FOM, 0.887 vs. 0.874, respectively; p = 0.581). Conclusion: Overall image quality and detectability of focal liver lesions is preserved in contrast-enhanced abdominopelvic LDCT obtained with DLIR-M relative to those in SDCT with h-IR.

• International Journal of Control, Automation, and Systems
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• 제4권6호
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• pp.769-774
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• 2006

In this paper, we discuss the problem of non-mutual detectability using the invariant zero. We propose a representation method for excess spaces by linear equation based on the Rosenbrock system matrix. As an alternative to the system enlargement method proposed by White[1], we propose an appropriate form of an enlarged system to make a set of faults mutually detectable by assigning sufficient geometric multiplicity of invariant zeros. We show the equivalence between the two methods and a necessary condition for the system enlargement in terms of the geometric and algebraic multiplicities of invariant zeros.

• 한국통신학회논문지
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• 제6권1호
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• pp.27-31
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• 1981

본 논문에서는 방해잡음이 존재하는 상황하에서 수대신능신계통에 대한 실효탐지능력인자의 변화를 고찰하였다. 최대탐지거리와 방해거리를 변수로하여 계산한 대수수신계통과 선형수신계통의 결과를 비교하였다. 대수수신계통이 선형수신계통보다 광역의 동특성을 가지나 탐지거리 100km에서 대수수신계통의 실효탐지인자가 약 15%정도 감소함을 알 수 있었다.

• Nuclear Engineering and Technology
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• 제46권6호
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• pp.883-888
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• 2014

This work presents the influence of noise originating from the tube itself on the detectability and sizing accuracy for laboratory-induced outer diameter axial cracks in nuclear steam generator tubes. The variations of signal amplitude and phase angle of the same cracks were analyzed when increasing the signal-to-noise ratio of the tube itself from 9 to 18. It was experimentally verified that the detectability for small cracks was enhanced by increasing the signal-to-noise ratio. The phase angle also rotated to a value representing the actual position and depth of a crack when increasing the signal-to-noise ratio.

• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.113-120
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• 1997

This paper presents an optimal design for the SPECT reconstruction filter, based on a physical limit of SPECT lesion detection capability. To increase the performance of the filter on lesion detectability, the filter design was focused on increasing the local SyW ratio of a threshold lesion, that was determined by minimum detectable lesion size (MDU) from SPECT lesion detectabllity contrast-detail curve. The proposed filter showed flexible window characteristics of resolution recovery and noise smoothing for MDLSs in the resolution-limited and photon-limited regions, respectively, compennting for the relative impact of the main limitation factors on threshold detectability. The simulated results showed good adaptability of the proposed filter to the changes in physical parameters of photon counts, object contrast, and detector system resolution.