• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.10
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• pp.1477-1482
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• 2022

Haze is a local weather phenomenon in which very small droplets float in the atmosphere, and the amount and characteristics of haze may vary depending on the region. In particular, these haze reduce visibility, which can cause air traffic interference and vehicle traffic accidents, and degrade the quality of security CCTVs and so on. Therefore, in the past 10 years, research on haze removal has been actively conducted to reduce damage caused by haze. In this study, local haze removal is performed by weight generation using a haziness degree evaluator to adaptively respond to haze-free, homogeneous haze, and non-homogeneous haze cases. And the proposed method improves the limitations of the existing static haze removal method, which assumes that there is haze in the input image and removes the haze. We also demonstrate the superiority of the proposed method through quantitative and qualitative performance evaluations with benchmark algorithms.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.911-917
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• 2023

The method of observing nodular changes on the liver surface using clinical ultrasonography is useful for diagnosing cirrhosis. However, the speckle noise that inevitably occurs in ultrasound images makes it difficult to identify changes in the liver surface and echo patterns, which has a negative impact on the diagnosis of cirrhosis. The purpose of this study is to model the median modified Wiener filter (MMWF), which can efficiently reduce noise in cirrhotic ultrasound images, and confirm its applicability. Ultrasound images were acquired using an ACR phantom and an actual cirrhotic patient, and the proposed MMWF algorithm and conventional noise reduction algorithm were applied to each image. Coefficient of variation (COV) and edge rise distance (ERD) were used as quantitative image quality evaluation factors for the acquired ultrasound images. We confirmed that the MMWF algorithm improved both COV and ERD values compared to the conventional noise reduction algorithm in both ACR phantom and real ultrasound images of cirrhotic patients. In conclusion, the proposed MMWF algorithm is expected to contribute to improving the diagnosis rate of cirrhosis patients by reducing the noise level and improving spatial resolution at the same time.

• Journal of the Korean Society of Radiology
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• v.10 no.6
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• pp.381-385
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• 2016

This study aims to propose a method for reducing radiation dose in high-voltage radiography using air gap technique while maintaining the same image quality as when using grids. For an experiment, air gaps were set at 10 cm, 15 cm, 20 cm, 25 cm, and 30 cm with a focus-receptor distance of 180 cm; with each air gap distance, tube current was set at 15 mAs, and tube voltage was set at 80 kVp, 85 kVp, 90 kVp, 95 kVp and 100 kVp. Then, radiographs were taken. In a situation of employing a conventional method of using grids, radiographs were taken at 15 mAs and 107 kVp with a focus-receptor distance of 180 cm. According to the results of the experiment, the surface radiation dose from radiography using grids was 0.130 R; the surface radiation dose at a 20cm air gap was 0.124 R; PSNR between these two images was 10.65 [dB]. In conclusion, the air gap distance, which could maintain the image quality similar to that of a case where scattered radiation was removed and grids were used with a small surface radiation dose, was 20 cm. The result of this study is thought to be used as an indicator to remove surface radiation dose in radiography using air gap.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.677-684
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• 2020

Miscentering in the left and right X axis direction during CT examination affects dose and quality. When the CT Gantry Isocenter and the center of the examination objective are matched using the Lateral Sliding Table, the image quality is improved and the exposure dose is reduced. CTDI Head Phantom (Kimda, Korea) and dosimeter (Ray Safe, Sweden) were used to measure dose comparison CTDI (mGy) due to center deviation, and Water Phantom (HITACHI, Japan) was used to measure noise to see the difference in uniformity due to center deviation. Measurements of doses for dose comparison CTDI (mGy) with a deviation showed that doses were consistently reduced and exact dose was not projected until they were moved to 80 mm by 20 mm from the Isocenter. SD values were measured to see the difference in uniformity due to center deviation and the noise continued to increase until it was moved by 20 mm to 80 mm. The range of collimation has increased by the extent of deviating from the center and the range of exposure has increased. Using the Lateral Sliding Table, you can easily adjust the Isocenter, increase the quality of the image by adjusting the Isocenter in areaa such as the cardiac examination of the location away from the Isocenter, Extreme bone and Shoulder, and greatly reduce the collimation to the Isocenter, so it can be used to reduce unnecessary exposure dose.

• Journal of IKEEE
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• v.21 no.4
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• pp.412-415
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• 2017

In this paper, we propose a multi license plate recognition system using high resolution $360^{\circ}$ omnidirectional IP camera. The proposed system consists of a planar division part of $360^{\circ}$ circular image and a multi license plate recognition part. The planar division part of the $360^{\circ}$ circular image are divided into a planar image with enhanced image quality through processes such as circular image acquisition, circular image segmentation, conversion to plane image, pixel correction using color interpolation, color correction and edge correction in a high resolution $360^{\circ}$ omnidirectional IP Camera. Multi license plate recognition part is through the multi-plate extraction candidate region, a multi-plate candidate area normalized and restore, multiple license plate number, character recognition using a neural network in the process of recognizing a multi-planar imaging plates. In order to evaluate the multi license plate recognition system using the proposed high resolution $360^{\circ}$ omnidirectional IP camera, we experimented with a specialist in the operation of intelligent parking control system, and 97.8% of high plate recognition rate was confirmed.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.129-138
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• 2007

The Purpose of this study is to suggest the basic data for making good quality image and maintaining equipment homeostasis by accepting image quality evaluation and radiation dose evaluation in Multi-detector CT. In this study we surveyed 14 CT equipments in Seoul. The results obtained were as follows ; CT number was $0.56{\pm}0.70\;HU$. Noise was $0.39{\pm}0.09\;HU$. Uniformity was $1.08{\pm}0.52\;HU$. High contrast resolution was $0.48{\pm}0.05\;mm$ and low contrast resolution was $3.65{\pm}1.16\;mm$. For CTDI, the central part and the peripheral part of head phantom were $43.2{\pm}15.4\;mGy$ and $45.6{\pm}17.5\;mGy$, respectively. For body phantom, the central part and the peripheral part of head phantom were $13.5{\pm}4.5$ and $29.2{\pm}10.2\;mGy$, respectively. CTDIw was $44.8{\pm}16.8\;mGy$ and CTDIw/100 mAs was $18.8{\pm}5.3\;mGy$ using head phantom. CTDIW was $24.0{\pm}8.3\;mGy$ and CTDIw/100 mAs was $10.1{\pm}2.5\;mGy$ using body phantom. Therefore, CT number, noise, high contrast resolution, low contrast resolution, CTDI, CTDIw and CTDIw/100 mAs of MDCT were showed excellently in all equipments.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.95-102
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• 2005

There are many tube and pipeline in nuclear power plant under high temperature and high pressure. Erosion and corrosion defects were expected on these tube and pipe-line by environmental and mechanical factors. These erosion and corrosion defects ran be evaluated by ultrasonic technique. In these study, Scanning Laser Source(SLS) technique was applied to detect defect and construct image. This technique also makes detection possible on rough and curved surfaces such as tube and pipe-line by scanning. Conventional ultrasonic scanning technique requires immersion of specimen or water jet for transferring ultrasonic wave between transducer and specimen. However, this SLS technique does not need contacting and couplant to generate surface wave and to get flaw images. Therefore, this SLS technique has several advantages, for complicated production inspection, non-contact, remote from specimen, and high resolution. In this study, SLS images were obtained with various conditions of generation laser ultrasound and receiving in order to enhance detectability of flaws on the tube. Stress corrosion cracks were produced on tube and images of stress corrosion cracks were constructed by using SLS technique.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.533-542
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• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.305-314
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• 2023

With the development of medical technology and radiation treatment equipment, the frequency of high-precision radiation therapy such as intensity modulation radiation therapy has increased. Image-guided radiation therapy has become essential for radiation therapy in precise and complex treatment plans. In particular, with the introduction of imaging equipment for diagnosis in a linear accelerator, CBCT scanning became possible, which made it possible to calibrate and correct the patient's posture through 3D images. Although more precise reproduction of the patient's posture has become possible, the exposure dose delivered to the patient during the image acquisition process cannot be ignored. Radiation optimization is necessary in the field of radiation therapy, and efforts to reduce exposure are necessary. However, when acquiring 3D CBCT images by changing the imaging conditions to reduce exposure, there should be no image quality or artefacts that would make it impossible to align the patient's position. In this study, Rando phantom was used to scan and evaluate images for each shooting condition. The highest SNR was obtained at 100 kV 80 mA 25 ms F1 filter 180°. As the tube voltage and tube current increased, the noise decreased, and the bowtie filter showed the optimal effect at high tube current. Based on the actual scanned images, it was confirmed that patient alignment was possible under all imaging conditions, and that image-guided radiation therapy for patient alignment was possible under the condition of 70 kV 10 mA 20 ms F0 filter 180°, which showed the lowest SNR. In this study, image evaluation was conducted according to the imaging conditions, and low tube voltage, tube current, and small rotation angle scan are expected to be effective in reducing radiation exposure. Based on this, the patient's exposure dose should be kept as low as possible during CBCT imaging.

• Journal of Broadcast Engineering
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• v.22 no.1
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• pp.28-41
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• 2017

In this paper, the fast encoding algorithm in High Efficiency Video Coding (HEVC) encoder was studied. For the encoding efficiency, the current HEVC reference software is divided the input image into Coding Tree Unit (CTU). then, it should be re-divided into CU up to maximum depth in form of quad-tree for RDO (Rate-Distortion Optimization) in encoding precess. But, it is one of the reason why complexity is high in the encoding precess. In this paper, to reduce the high complexity in the encoding process, it proposed the method by determining the maximum depth of the CU using a hierarchical clustering at the pre-processing. The hierarchical clustering results represented an average combination of motion vectors (MV) on neighboring blocks. Experimental results showed that the proposed method could achieve an average of 16% time saving with minimal BD-rate loss at 1080p video resolution. When combined the previous fast algorithm, the proposed method could achieve an average 45.13% time saving with 1.84% BD-rate loss.