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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Institute of Electronics and Information Engineers
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The Institute of Electronics Engineers of Korea
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Volume & Issues
Volume 51, Issue 12 - Dec 2014
Volume 51, Issue 11 - Nov 2014
Volume 51, Issue 10 - Oct 2014
Volume 51, Issue 9 - Sep 2014
Volume 51, Issue 8 - Aug 2014
Volume 51, Issue 7 - Jul 2014
Volume 51, Issue 6 - Jun 2014
Volume 51, Issue 5 - May 2014
Volume 51, Issue 4 - Apr 2014
Volume 51, Issue 3 - Mar 2014
Volume 51, Issue 2 - Feb 2014
Volume 51, Issue 1 - Jan 2014
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Design of a simple closed-loop Transmit Diversity Scheme Using Sub-carrier Grouping for ECMA-392 Systems
Joo, Jung Suk ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 3~9
DOI : 10.5573/ieie.2014.51.4.003
ECMA-392 is the first cognitive radio (CR) specification for personal/portable devices in TV white space. It supports two transmit antennas, for which only open-loop transmit diversity schemes are included. In this paper, we design a simple closed-loop transmit diversity scheme using sub-carrier grouping for ECMA-392 systems. First, sub-carrier grouping types suitable for ECMA-392 systems are described, and then a transmit antenna selection scheme is proposed. In order to reduce feedback information, decision on the transmit antenna selection in the given channel environments is made at the receiver side and the only index of the decided transmit antenna is sent to the transmit side. Through performance comparison to open-loop transmit diversity schemes of ECMA-392, it will be shown that with only a slight feedback overhead, the proposed scheme can improve receiver performance of ECMA-392 systems.
Performance Evaluation of Routing Algorithms based on Optimum Transmission Range in Tactical MANETs
Choi, Hyungseok ; Lee, JaeYong ; Kim, ByungChul ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 10~17
DOI : 10.5573/ieie.2014.51.4.010
This paper presents an analytical method for finding the optimum transmission range in mobile ad hoc networks(MANETs). The results are particularly useful for the operation of military networks, as the transmission range affects the traffic throughput of user & routing traffic, delay, and frequency interference. When the conditions of tactical environment are applied in our simulations and the above-mentioned performances are analyzed, we find the OLSR protocol is more excellent. Plus, we compare the results of MANETs performance when applying optimum transmission range and the default transmission range(10km), and analyze the reasonability of the calculation of optimum transmission range proposed by this paper.
Placement Optimization of Airborne Line-Of-Sight Datalink Directional Antenna in UAV
Kim, Jihoon ; Choi, Jaewon ; Chung, Eulho ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 18~24
DOI : 10.5573/ieie.2014.51.4.018
In this paper, the optimum placement of airborne line-of-sight (LOS) datalink directional antenna to minimize the datalink loss within the operation range of unmanned aerial vehicle (UAV) is analyzed by using the electromagnetic (EM) simulation. In quick banking of UAV, the datalink loss is occurred due to the electromagnetic distortion and transmission loss by the fuselage blockage. In general, the banking angle of UAV is limited to prevent the datalink loss. However, in this case, there is the problem that the mission performance ability is largely limited by the banking radius increase. To solve this problem, the optimum placement to mount the airborne LOS datalink 1-axis directional antenna on both the top and bottom surfaces of fuselage is analyzed by using EM simulation. The 1-axis antenna with large vertical beamwidth is used because the banking angle of UAV is dependent on the vertical beamwidth of antenna. Also, there is the benefit to reduce largely the weight because the 1-axis antenna can be mounted instead of the 2-axis one.
Two-Dimensional Hybrid Codes using Identity Matrix and Symmetric Balance Incomplete Block Design Codes for Optical CDMA
Jhee, Yoon Kyoo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 27~32
DOI : 10.5573/ieie.2014.51.4.027
Two-dimensional hybrid codewords are generated by using each row of identity matrix for spatial encoding and nonideal symmetric balance incomplete block design(BIBD) code for spectral encoding. This spatial/spectral optical code-division multiple-access (OCDMA) network uses single-balanced detectors to abstract the desired information bits and to eliminate the multiple-access interference(MAI). Analytical results show that the number of simultaneous users increases significantly by using the proposed hybrid codes.
Performance Improvement Method of Multi-Port Memory Controller Using An Effective Multi-Channel Direct memory Access Management
Chun, Ik-Jae ; Lyuh, Chun-Gi ; Roh, Tae Moon ; Lee, Moon-Sik ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 33~41
DOI : 10.5573/ieie.2014.51.4.033
This paper presents an effective memory access method for a high-speed data transfer on mobile systems using a direct memory access controller that considers the characteristics of a multi-port memory controller. The direct memory access controller has an integrated channel management function to control multiple direct memory access channels. The channels are physically separated and operate independently from each other. Experimental results show that the proposed direct memory access method improves the transfer performance by up to 72% and 69% on read and write transfer cycles, respectively. The total number of transfer cycles of the proposed method is 63% less than in a commercial method under 4-channel access.
A New Small-Swing Domino Logic based on Twisted Diode Connections
Ahn, Sang-Yun ; Kim, Seok-Man ; Jang, Young-Jo ; Cho, Kyoungrok ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 42~48
DOI : 10.5573/ieie.2014.51.4.042
In this paper, we propose a new small swing domino logic that reduces the swing amplitude by using twist-connected PMOS and NMOS transistors. The output swing range of the proposed circuit is adjusted by the size of the twist-connected transistors and the load capacitance. The designed RCA with the proposed circuit technique shows reduction of the power consumption by 37% and PDP performance by 43% compared with the domino CMOS logic.
A 13-Gbps Low-swing Low-power Near-ground Signaling Transceiver
Ku, Jahyun ; Bae, Bongho ; Kim, Jongsun ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 49~58
DOI : 10.5573/ieie.2014.51.4.049
A low-swing differential near-ground signaling (NGS) transceiver for low-power high-speed mobile I/O interface is presented. The proposed transmitter adopts an on-chip regulated programmable-swing voltage-mode driver and a pre-driver with asymmetric rising/falling time. The proposed receiver utilizes a new multiple gain-path differential amplifier with feed-forward capacitors that boost high-frequency gain. Also, the receiver incorporates a new adaptive bias generator to compensate the input common-mode variation due to the variable output swing of the transmitter and to minimize the current mismatch of the receiver`s input stage amplifier. The use of the new simple and effective impedance matching techniques applied in the transmitter and receiver results in good signal integrity and high power efficiency. The proposed transceiver designed in a 65-nm CMOS technology achieves a data rate of 13 Gbps/channel and 0.3 pJ/bit (
CMOS Power Amplifier Using Mode Changeable Autotransformer
Ryu, Hyunsik ; Nam, Ilku ; Lee, Dong-Ho ; Lee, Ockgoo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 59~65
DOI : 10.5573/ieie.2014.51.4.059
In this paper, in order to improve efficiency performance of power amplifiers, a mode changeable autotransformer is proposed. Efficiency performance at the low-power mode can be improved by adopting the mode changeable autotransformer. A dual-mode autotransfomrer CMOS power amplifier using a standard 0.18-
CMOS process is designed in this work. Number of turns in a primary winding is re-configurated according to mode change between the high-power mode and the low-power mode. Thus, the efficiency performance of the power amplifier at each mode is optimized. EM and total circuit simulation results verify that low-power mode power added efficiency(PAE) at 24dBm output power is improved from 10.4% to 26.1% using the proposed multi-mode operation.
Reversible Data Hiding Method Based on Min/Max in 2×2 Sub-blocks
Kim, Woo-Jin ; Kim, Pyung-Han ; Lee, Joon-Ho ; Jung, Ki-Hyun ; Yoo, Kee-Young ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 69~75
DOI : 10.5573/ieie.2014.51.4.069
A novel reversible data hiding method using pixel value ordering and prediction error expansion in the sub-block is resented in this paper. For each non-overlapping
sub-block, we divide into two groups. In the min group, the lowest value is changed to embed a secret bit and the highest value is changed in the max group. The experimental results show that the proposed method achieves a good visual quality and high capacity. The proposed method can embed 13,900 bits on average, it is higher 4,553 bits than the previous method and the visual quality is maintained 31.39dB on average.
Design and Implementation of MAC Protocol for Underwater Mobile Ad-hoc Networks
Lee, Jin-Young ; Yun, Nam-Yeol ; Park, Soo-Hyun ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 76~89
DOI : 10.5573/ieie.2014.51.4.076
In this paper, we propose a MAC(Media Access Control) protocol based on flexible RWT(RTS Waiting Time) for underwater mobile ad-hoc networks with a three-way handshaking mechanism. This protocol can solve a problem of collision between RTS(Request-To-Send) and CTS(Clear-To-Send) packets in existing MACA(Multiple Access with Collision Avoidance) protocol. This proposed MAC protocol is also an effective protocol which can apply to underwater mobile ad-hoc networks in a real field by using implementable technologies. We set flexible RTS Waiting Time called RWT, considering various characteristics of underwater environment. It is possible to support variable network size according to node mobility. Finally, we conduct a performance evaluation between proposed MAC protocol and existing MACA based MAC protocol through practical implementation and experiment. As a result, we verify the superiority of our proposed MAC protocol in terms of throughput, packet drop rate, average transmission time, energy consumption and channel utilization.
A Software Framework for Automatic Exception Handling of Context-aware Systems
Yoon, Tae-Seob ; Cho, Eun-Sun ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 90~97
DOI : 10.5573/ieie.2014.51.4.090
Context-aware systems provide proper services for the user according to current contexts. However, it is not actively deployed in our daily lives as expected, due to many concerns including occurrences of exceptions. C++/C#/JAVA provide exception handling facilities for desktop computing programs, but context-aware system developers might feel far more difficult to make use of such general facilities, because it is hard to decide the timing and position of exception handling with various devices engaged. In this paper, we propose an exception detection and handling mechanism using device semantics and AspectJ so that it can constantly detect a large number of devices to allow the programmers to detect and handle exceptions with less burden.
Contour Extraction Method using p-Snake with Prototype Energy
Oh, Seung-Taek ; Jun, Byung-Hwan ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 101~109
DOI : 10.5573/ieie.2014.51.4.101
It is an essential element for the establishment of image processing related systems to find the exact contour from the image of an arbitrary object. In particular, if a vision system is established to inspect the products in the automated production process, it is very important to detect the contours for standardized shapes such lines and curves. In this paper, we propose a prototype adaptive dynamic contour model, p-Snake with improved contour extraction algorithms by adding the prototype energy. The proposed method is to find the initial contour by applying the existing Snake algorithm after Sobel operation is performed for prototype analysis. Next, the final contour of the object is detected by analyzing prototypes such as lines and circles, defining prototype energy and using it as an additional energy item in the existing Snake function on the basis of information on initial contour. We performed experiments on 340 images obtained by using an environment that duplicated the background of an industrial site. It was found that even if objects are not clearly distinguished from the background due to noise and lighting or the edges being insufficiently visible in the images, the contour can be extracted. In addition, in the case of similarity which is the measure representing how much it matches the prototype, the prototype similarity of contour extracted from the proposed p-ACM is superior to that of ACM by 9.85%.
3D Visual Attention Model and its Application to No-reference Stereoscopic Video Quality Assessment
Kim, Donghyun ; Sohn, Kwanghoon ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 110~122
DOI : 10.5573/ieie.2014.51.4.110
As multimedia technologies develop, three-dimensional (3D) technologies are attracting increasing attention from researchers. In particular, video quality assessment (VQA) has become a critical issue in stereoscopic image/video processing applications. Furthermore, a human visual system (HVS) could play an important role in the measurement of stereoscopic video quality, yet existing VQA methods have done little to develop a HVS for stereoscopic video. We seek to amend this by proposing a 3D visual attention (3DVA) model which simulates the HVS for stereoscopic video by combining multiple perceptual stimuli such as depth, motion, color, intensity, and orientation contrast. We utilize this 3DVA model for pooling on significant regions of very poor video quality, and we propose no-reference (NR) stereoscopic VQA (SVQA) method. We validated the proposed SVQA method using subjective test scores from our results and those reported by others. Our approach yields high correlation with the measured mean opinion score (MOS) as well as consistent performance in asymmetric coding conditions. Additionally, the 3DVA model is used to extract information for the region-of-interest (ROI). Subjective evaluations of the extracted ROI indicate that the 3DVA-based ROI extraction outperforms the other compared extraction methods using spatial or/and temporal terms.
Sequential Defect Detection According to Defect Possibility in TFT-LCD Panel Image
Lee, SeungMin ; Kim, Tae-Hun ; Park, Kil-Houm ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 123~130
DOI : 10.5573/ieie.2014.51.4.123
In TFT-LCD panel images, defects are typically detected by using a large difference in the brightness compared to the background. In this paper, we propose a sequential defect detection algorithm according to defect possibility caused by difference of brightness. By using this method, pixels with high defect probabilities are preferentially detected and defects with a large brightness difference are accurately detected. Also, limited defects with a small brightness difference is detected more reliably, eventually minimizing the degree of over-detection. We have experimentally confirmed that our proposed method showed an excellent detection result for detecting limited defects as well as defects with a large brightness difference.
No-Reference Visibility Prediction Model of Foggy Images Using Perceptual Fog-Aware Statistical Features
Choi, Lark Kwon ; You, Jaehee ; Bovik, Alan C. ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 131~143
DOI : 10.5573/ieie.2014.51.4.131
We propose a no-reference perceptual fog density and visibility prediction model in a single foggy scene based on natural scene statistics (NSS) and perceptual "fog aware" statistical features. Unlike previous studies, the proposed model predicts fog density without multiple foggy images, without salient objects in a scene including lane markings or traffic signs, without supplementary geographical information using an onboard camera, and without training on human-rated judgments. The proposed fog density and visibility predictor makes use of only measurable deviations from statistical regularities observed in natural foggy and fog-free images. Perceptual "fog aware" statistical features are derived from a corpus of natural foggy and fog-free images by using a spatial NSS model and observed fog characteristics including low contrast, faint color, and shifted luminance. The proposed model not only predicts perceptual fog density for the entire image but also provides local fog density for each patch size. To evaluate the performance of the proposed model against human judgments regarding fog visibility, we executed a human subjective study using a variety of 100 foggy images. Results show that the predicted fog density of the model correlates well with human judgments. The proposed model is a new fog density assessment work based on human visual perceptions. We hope that the proposed model will provide fertile ground for future research not only to enhance the visibility of foggy scenes but also to accurately evaluate the performance of defog algorithms.
Matching Points Filtering Applied Panorama Image Processing Using SURF and RANSAC Algorithm
Kim, Jeongho ; Kim, Daewon ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 144~159
DOI : 10.5573/ieie.2014.51.4.144
Techniques for making a single panoramic image using multiple pictures are widely studied in many areas such as computer vision, computer graphics, etc. The panorama image can be applied to various fields like virtual reality, robot vision areas which require wide-angled shots as an useful way to overcome the limitations such as picture-angle, resolutions, and internal informations of an image taken from a single camera. It is so much meaningful in a point that a panoramic image usually provides better immersion feeling than a plain image. Although there are many ways to build a panoramic image, most of them are using the way of extracting feature points and matching points of each images for making a single panoramic image. In addition, those methods use the RANSAC(RANdom SAmple Consensus) algorithm with matching points and the Homography matrix to transform the image. The SURF(Speeded Up Robust Features) algorithm which is used in this paper to extract featuring points uses an image`s black and white informations and local spatial informations. The SURF is widely being used since it is very much robust at detecting image`s size, view-point changes, and additionally, faster than the SIFT(Scale Invariant Features Transform) algorithm. The SURF has a shortcoming of making an error which results in decreasing the RANSAC algorithm`s performance speed when extracting image`s feature points. As a result, this may increase the CPU usage occupation rate. The error of detecting matching points may role as a critical reason for disqualifying panoramic image`s accuracy and lucidity. In this paper, in order to minimize errors of extracting matching points, we used
region`s RGB pixel values around the matching points` coordinates to perform intermediate filtering process for removing wrong matching points. We have also presented analysis and evaluation results relating to enhanced working speed for producing a panorama image, CPU usage rate, extracted matching points` decreasing rate and accuracy.
Fast LDPC Decoding using Bit Plane Correlation in Wyner-Ziv Video Coding
Oh, Ryanggeun ; Shim, Hiuk Jae ; Jeon, Byeungwoo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 160~172
DOI : 10.5573/ieie.2014.51.4.160
Although Wyner-Ziv (WZ) video coding proves useful for applications employing encoders having restricted computing resources, the WZ decoder has a problem of excessive decoding complexity. It is mainly due to its iterative LDPC channel decoding process which repeatedly requests incremental parity data after iterative channel decoding of parity data received at each request. In order to solve the complexity problem, we divide bit planes into two groups and estimate the minimum required number of parity requests separately for the two groups of bit planes using bit plane correlation. The WZ decoder executes the iterative decoding process only after receiving parity data corresponding to the estimated minimum number of parity requests. The proposed method saves about 71% of the computing time in the LDPC decoding process.
Smoothed Group-Sparsity Iterative Hard Thresholding Recovery for Compressive Sensing of Color Image
Nguyen, Viet Anh ; Dinh, Khanh Quoc ; Van Trinh, Chien ; Park, Younghyeon ; Jeon, Byeungwoo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 173~180
DOI : 10.5573/ieie.2014.51.4.173
Compressive sensing is a new signal acquisition paradigm that enables sparse/compressible signal to be sampled under the Nyquist-rate. To fully benefit from its much simplified acquisition process, huge efforts have been made on improving the performance of compressive sensing recovery. However, concerning color images, compressive sensing recovery lacks in addressing image characteristics like energy distribution or human visual system. In order to overcome the problem, this paper proposes a new group-sparsity hard thresholding process by preserving some RGB-grouped coefficients important in both terms of energy and perceptual sensitivity. Moreover, a smoothed group-sparsity iterative hard thresholding algorithm for compressive sensing of color images is proposed by incorporating a frame-based filter with group-sparsity hard thresholding process. In this way, our proposed method not only pursues sparsity of image in transform domain but also pursues smoothness of image in spatial domain. Experimental results show average PSNR gains up to 2.7dB over the state-of-the-art group-sparsity smoothed recovery method.
SIR analysis for Enhancing Image Quality in Underwater Acoustic Lens System
Lee, Jieun ; Im, Sungbin ; Shim, Taebo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 181~190
DOI : 10.5573/ieie.2014.51.4.181
The underwater acoustic lens system is one of the systems getting high-resolution images on the seafloor by the beam forming method using acoustic lens. The beam forming using acoustic lenses reduces complexity and driving power. When receiving an incoming beam with the acoustic lens array, beam pattern analysis and arrangement problem of the array sensor must be addressed. Introducing SIR (Signal to Interference Ratio), the relationship among sensor interval, beam pattern and image quality would be analyzed. Generally if the sensor interval getting wider, the less effect of the side lobes makes SIR high. If the amplitude of a side lobe is high, SIR is generally getting low. The type of the apodization function changes the width, shape and amplitude of both main lobe and side lobes. Thus an appropriate apodization function can improve SIR. In this paper, SIR is stable at the sensor interval of 13mm with 0-10dB, which is not high relatively. By applying the Chebyshev function, the SIR becomes 80dB over the sensor interval of 37 mm or higher. The Hann and triangular functions demonstrate better SIR when the sensor interval becomes narrower.
Development of One-channel Gamma ray spectroscope for Automatic Radiopharmaceutical Synthesis System
Song, Kwanhoon ; Kim, Kwangsoo ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 193~200
DOI : 10.5573/ieie.2014.51.4.193
In this paper, the prototype of one-channel gamma-ray spectroscope for automatic radiopharmaceutical systhesis system was designed and characterized. The prototype employed CZT (CdZnTe) spear detector for gamma-ray detection and employed analog-type signal processing method. A radioactive sample Co-60 was used for measuring performance of the gamma-ray spectroscope and energy spectrum is gained with bandwidth of 1173keV. The analog board is made up of SF (shaping filter) and PHA (peak and hold amplifier) for shaping CZT output signal appropriately and ADC (analog to digital converter) and FPGA (field programmable gate array) for drawing gamma-ray spectrum by counting the digitalized gamma-ray signal data.
A Study on the Optical flow Method for Analysis of Ipper Airway Deformation from Magnetic Resonance Images for Children with Obstructive Sleep Apnea Syndrome
Lee, Min Hee ; Kim, Dong Youn ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 201~209
DOI : 10.5573/ieie.2014.51.4.201
Obstructive sleep apnea syndrome(OSAS) is a respiratory disease caused by partial or complete obstruction of the upper airway during sleep. In this paper, we proposed the optical flow method to analyze the upper airway dynamic changes during respiration for children with OSAS and control subjects. We compared the absolute value of difference between inspiration and expiration for airway area analysis method and optical flow method for 5 children with OSAS and 6 control subjects. From the statistical analysis, airway area analysis method and optical flow method are statistically significant at the 0.1 (p value is 0.0977) and 0.01 (p value is 0.0011) significance level respectively. From this simulations, the optical flow method could provide more accurate information to diagnose the OSAS patients than the traditional airway area analysis method.
Experimental Studies of Control of a One-wheel Robot by Modifying Design and Control Method
Park, June Hyung ; Ha, Min Soo ; Jung, Seul ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 210~217
DOI : 10.5573/ieie.2014.51.4.210
This paper presents experimental studies on controlling one-wheel robot, GYROBO. The previous one has the problem of falling down because the inside gimbal leans against one direction to make it balancing. This structural problem has been solved by redesigning the system. Gains obtained through experimental tasks are used as a gain scheduling method so that GYROBO is more stabilized. A line trajectory following control task is performed to test the driving control as well.
The Study of Optimal Acquisition Condition and Image Processing
Lee, Yong-Gu ; Shin, Jong-Ho ; Seo, Kyoung-Eun ; Choi, Yoo-Lee ; Lee, Soo-Hyeon ; Lee, Young-Jin ; Kim, Hee-Joung ;
Journal of the Institute of Electronics and Information Engineers, volume 51, issue 4, 2014, Pages 221~226
DOI : 10.5573/ieie.2014.51.4.221
In this paper, we achieved the study which determined the excellent diagnostic condition and searched the exposure condition with the minimum radiation exposure level having the equal diagnostic ability. To accomplish these study, chest phantom images with lesions and without ones were evaluated at various exposure conditions. With respect to the phantom with lesions and without ones, we obtained the chest PA imaging applied by photographing parts of DR apparatus and the images processed as histogram equalization and edge enhancement method. The images were acquired at the exposure conditions of 2.0, 2.5, 3.2, 4.0 and 5.0mAs. The morphological analysis was performed by ROC curves using the images obtained at each exposure condition. The exposure conditions with the most excellent diagnostic ability and with the equal diagnostic capability having the minimum radiation exposure level were determined by means of sensitivity, specificity and accuracy.