• Journal of Magnetics
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• v.19 no.2
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• pp.185-191
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• 2014

In this study we evaluated that flow rate changes affect the (time of flight) TOF image and contrast-enhanced (CE) in a three-dimensional TOF angiography. We used a 3.0T MR System, a nonpulsatile flow rate model. Saline was used as a fluid injected at a flow rate of 11.4 cm/sec by auto injector. The fluid signal strength, phantom body signal strength and background signal strength were measured at 1, 5, 10, 15, 20 and 25-th cross-section in the experienced images and then they were used to determine signal-to-noise ratio and contrast-to-noise ratio. The inlet, middle and outlet length were measured using coronal images obtained through the maximum intensity projection method. As a result, the length of inner cavity was 2.66 mm with no difference among the inlet, middle and outlet length. We also could know that the magnification rate is 49-55.6% in inlet part, 49-59% in middle part and 49-59% in outlet part, and so the image is generally larger than in the actual measurement. Signal-to-noise ratio and contrast-to-noise ratio were negatively correlated with the fluid velocity and so we could see that signal-to-noise ratio and contrast-to-noise ratio are reduced by faster fluid velocity. Signal-to-noise ratio was 42.2-52.5 in 5-25th section and contrast-to-noise ratio was from 34.0-46.1 also not different, but there was a difference in the 1st section. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s. Consequently, 3D TOF MRA tests show that the faster fluid velocity decreases the signal-to-noise ratio and contrast-to-noise ratio, and basically it can be determined that 3D TOF MRA and 3D CE MRA are displayed larger than in the actual measurement.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.79-85
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• 2017

The purpose of this study was to measure contrast to noise ratio (CNR) and signal to noise ratio (SNR) according to change of reconstruction from region of interest (ROI) in breast positron emission tomography-computed tomography (PET-CT), and to analyze the CNR and SNR statically. We examined images of breast PET-CT of 100 patients in a University-affiliated hospital, Seoul, Korea. Each patient's image of breast PET-CT were calculated by using ImageJ. Differences of CNR and SNR among four reconstruction algorithms were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p<0.05). We have analysis socio-demographical variables, CNR and SNR according to reconstruction images, 95% confidence according to CNR and SNR of reconstruction and difference in a mean of CNR and SNR. SNR results, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR and SNR of PET-CT reconstruction methods of the breast would be useful to evaluate breast diseases.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.9-14
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• 2021

Recently, magnetic resonance imaging (MRI), which can acquire images with good contrast without exposure to radiation, has been widely used for diagnosis. However, noise that reduces the accuracy of diagnosis is essentially generated when acquiring the MR images, and by adjusting the parameters, the noise problem can be solved to obtain an image with excellent characteristics. Among the parameters, the number of excitation (NEX) can acquire images with excellent characteristics without additional degradation of image characteristics. In contrast, appropriate NEX setting is required since the scan time increases and motion artifacts may occur. Therefore, in this study, after fixing all MRI parameters through the MRiLab simulation program, we tried to evaluate the tendency of image characteristics according to changing NEX through quantitative evaluation of brain T2 weighted images acquired by adjusting only NEX. To evaluate the noise level and similarity of the acquired image, signal to noise ratio (SNR), contrast to noise ratio (CNR), root mean square error (RMSE) and peak signal to noise ratio (PSNR) were calculated. As a result, both noise level and similarity evaluation factors showed improved values as NEX increased, while the increasing width gradually decreased. In conclusion, we demonstrated that an appropriate NEX setting is important because an excessively large NEX does not affect image characteristics improvement and cause motion artifacts due to a long scan.

• Journal of the Korean Magnetics Society
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• v.26 no.3
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• pp.105-114
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• 2016

In this study, For assessment of triangular fibrocartilage complex (TFCC) injury, we acquired images by fat suppressed 3D fast spoiled gradient recalled T1 and fat suppressed Isotropic 3D fast spin echo T1 techniques. For quantitative evaluation, measured signal to noise ratio and contrast to noise ratio and verified statistical significance between two imaging techniques by Mann-Whitney U verification. And for qualitative evaluation, marked 4-grade scoring (0: non diagnostic, 1: poor, 2: adequate, 3: good) on shape of TFCC, artifacts by partial volumes, description of the lesions by two radiologist, verified coincidence between 2 observer using Kappa-value verification. We used 3.0 Tesla MR equipment and 8-channel RF coil for imaging acquisition. As quantitative evaluation results, signal to noise ratio and contrast to noise ratio value of Isotropic 3D fast spin echo T1 technique is higher in every image sections, also between two imaging techniques by Mann-Whitney U verification was statistically significant (p < 0.05). As qualitative results, observer 1, 2 marked a higher grade on Isotropic 3D FSE T1 technique, coincidence verification of evaluation results between two observers by Kappa-value verification was statistically significant (p < 0.05). As a result, during MRI examination on TFCC injury, fat suppressed Isotropic 3D fast spin echo T1 technique is considered offering more useful information about abnormal lesion of TFCC.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.2
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• pp.90-94
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• 2013

In this paper, we propose a new algorithm to improve the contrast ratio, to preserve information of bright regions and to maintain the color of backlight image that appears with a great relative contrast. Backlight images of the natural environment have characteristics for difference of local brightness; the overall image contrast improvement is not easy. To improve the contrast of the backlight images, MSR (Multi-Scale Retinex) algorithm using the existing multi-scale Gaussian filter is applied. However, existing multi-scale Gaussian filter involves color distortion and information loss of bright regions due to excessive contrast enhancement and noise because of the brightness improvement of dark regions. Moreover, it also increases computational complexity due to the use of multi-scale Gaussian filter. In order to solve these problems, a linear MSR is performed that reduces the amount of computation from the HSV color space preventing the color distortion and information loss due to excessive contrast enhancement. It can also remove the noise of the dark regions which is occurred due to the improved contrast through edge preserving filter. Through experimental evaluation of the average color difference comparison of CIELAB color space and the visual assessment, we have confirmed excellent performance of the proposed algorithm compared to conventional MSR algorithm.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.2
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• pp.39-47
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• 2014

Purpose As breast cancer patients continue to increase every year, cases of BSGI are on the rise with a heavier reliance on it. However, BSGI protocol in hospitals was not studied enough despite it was covered by hospital's condition and recommendation of manufacturers. The objective of the study was an examination of methods to be applicable to BSGI protocols, putting the self-development phantom to use in quality assessment of the images. Materials and Methods Dilon 6800 (Dilon Technologies Inc, Newport News, USA) was used in the study and five different sizes of sphere were distinctively produced in the phantom. The study used $^{99m}TcO_4$. The cases were classified in to three categories that background radioactivity to region of interest as ratio of 2: 4: 8, They were acquired images for 5, 7, 10mins. The acquired image was set region of interest according to the size of sphere, and We analyzed quantitative and qualitative analysis. The acquired data statistically analyzed with SPSS ver.18.0. Results As the result of quantitative and qualitative analysis, count rate of each sphere in accordance with difference of injection dose showed that higher count rate as injection dose and sphere size increased (P<0.005). Count rate of each sphere in accordance with difference of acquisition time showed that higher count rate as acquisition time and sphere size increased (P<0.005). Contrast noise ratio of each sphere in accordance with difference of injection dose showed that higher contrast noise ratio as injection dose increased. Particularly, Contrast noise ratio of eight times ratio images was the highest among. Contrast noise ratio of each sphere in accordance with difference of acquisition time showed that higher contrast noise ratio as acquisition time increased. And, Contrast noise ratio of seven minute image was the highest among (P<0.005). Conclusion There was significant change of Contrast noise ratio through quantitative and qualitative analysis. Moreover, We found usefulness of phantom. If Institutions identified image through the phantom study and they made BSGI protocol, We expected to help the improvement of diagnostic value of the images.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.656-659
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• 2006

MD (DLP, LCoS) Projection TV is appropriate for large screen display with high definition at a relatively low price and thus, has been popular in the digital TV market. In order to realize high resolutions in the DLP projection TV, we successfully developed the Pixel Enhancement Actuator. Furthermore, it is also required that the contrast ratio of projected video signals onto a large screen should be improved. Therefore, we propose a contrast enhancer which adjusts the amount of projected lights by a dynamic aperture and a attached position sensor.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.108-108
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• 2001

Purpose： To correlate the histological differentiation of hepatocellular carcinomas (HCCs) with finding on triple contrast-enhanced MR imaging using gadolinium-chelates, superparamganetic ire oxides (SPIO), and mangafodipir trisodium. Method： Ten patients with proven HCC underwent triple contrast-enhanced MRI befo surgical resection. Subjective ratings of the enhancement pattern and degree were compare with the histological grades determined on surgical specimen. Quantitative measurements signal-to-noise ratio (S/N) of the lesion and the lesion-to-liver contrast-to-noise ratio C/N on the enhanced MR images, and the degree of S/N and C/N changes between the unenhanced and enhanced images were also correlated with the histological grades.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.71-78
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• 2017

Scattered radiation is inherent phenomenon of x-ray, which occurs to the subject (or patient). Therefore it cannot be avoidable but also interacts as serious noise factor because the only meaningful information on x-ray radiography is primary x-ray photons. The purpose of this study was to quantify scattered radiation for various shooting parameters and to verify the effect of anti-scatter grid. We employed beam stopper method to characterize scatter to primary ratio. To evaluate effect on the projection images calculated contrast to noise ratio of given shooting parameters. From the experiments, we identified the scattered radiation increases in thicker patient and smaller air gap. Moreover, scattered radiation degraded contrast to noise ratio of the projection images. We find out that the anti-scatter grid rejected scattered radiation effectively, however there were not fewer than 100% of scatter to primary ratio in some shooting parameters. The results demonstrate that the scattered radiation was serious problem of medical x-ray system, we confirmed that the scattered radiation was not considerable factor of dig ital radiog raphy.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.295-300
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• 2021

This study aims to present new chest AP examination exposure conditions through a study on the effect on image quality and patient dose by applying high tube voltage and scatter ray post-processing software during chest AP examination in digital radiography equipment. This study was used a human body phantom and in the chest AP position, the dosimeter was placed horizontally at the thoracic spine 6. The experiment was conducted by dividing into a low tube voltage (70 kVp, 400 mA, 3.2 mAs) group and a high tube voltage (100 kVp, 400 mA, 1.2 mAs) group. The collimation size (14″× 17″) and the source to image receptor distance(110 cm) were same applied to both groups. Radiation dose was presented to dose area product and entrance surface dose. Image quality was compared and analyzed by comparing the difference between the signal-to-noise ratio and the contrast-to-noise ratio of the image according to the application of the scatter ray post-processing software under each condition. The average value of the entrance surface dose in the low and high tube voltage conditions was 93.04±0.45 µGy and 94.25±1.51 µGy, which was slightly higher in the high tube voltage condition, but the dose area product was 0.97±0.04 µGy and 0.93±0.01 µGy. There was a statistically significant difference in the group mean value(p<0.01). In terms of image quality, the values of the signal-to-noise ratio and the contrast noise ratio were higher in the high tube voltage than in the low tube voltage, and decreased when the scattering line post-processing function was used, but the contrast resolution was improved. If there is a scatter ray post-processing function during chest AP examination, it is helpful to actively utilize it to improve the image quality. However, when this function is not available, I thought that applying a higher tube voltage state than a low tube voltage state will help to realize images with a large amount of information without changing the dose.