• Journal of radiological science and technology
• /
• v.38 no.3
• /
• pp.205-211
• /
• 2015

We evaluated the effectiveness of TL (Time Limit) method by comparing with NTL (Non-time limit) method when it is used for examinations for abdomen Anterior Posterior (AP) in this paper. The evaluation was conducted based on the comparison of dose, and of signal to noise ratio (SNR) and contrast to ratio (CNR) on both methods. The experiments were conducted with XGEO GC 80 (Samsung, Korea), Unfors ThinX RAD (Unfors, Sweden) and Rando Phantom (Alderson research laboratories, USA) and shielding material with the size of $5.5{\times}9{\times}0.1cm^3$. It was set to activate only two upper ionization chambers in automatic exposure control(AEC) mode and the tube-voltage was set to 80kVp. When the exposure time was limited, it is limited to 51 msec. The images both by NTL AEC method and TL AEC method were acquired when with and without attachment of shielding material on the upper ionization chambers. The images were evaluated by SNR and CNR which are the image evaluation methods using 'Image J'. The NTL AEC method showed increases in dose as much as 130.7% at maximum and 80% at minimum than other methods. The TL AEC method showed decreases in mAs and exposure dose than the NTL AEC method as much as 43.8% and 44.4% respectively. There were no significant differences in SNR or CNR for the experiments (($p{\geq}0.05$). Therefore, it is suggested that the TLAEC mode is more effective when examining patients who have high BMI index or a patient with a metallic substance in the body after surgery.

• Korean Journal of Digital Imaging in Medicine
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2013

Purpose : The Carotid Angio inspection including Aortic arch applied to wide area is conducted as the Contrast Enhance MR Angiography(CEA) which is using a contrast medium. However it is a burden not only for someone such as infants, pregnant women and patients suffering from kidney failure but continuous use of contrast medium also can be a burden for patients who has been taken follow up inspection since diagnose lesion already. The purpose of this study is to estimate a usefulness of the Time of Flight (TOF) by comparing with CEA. Materials and methods : 10 patients with an average age of 58 (from 45 to 75) who had MRA inspection in our hospital were studied using 3.0 Tesla Aachieva (Philips, Netherland) MRI system and Sense Neuro-Vascular 16 Channels Coil. The same patient was inspected both TOF and CEA simultaneously. The TOF inspection included from Aortic arch to Willis Circle by connecting 3 TOF stacks and so did CEA inspection. The quantitative analysis was conducted through signal to noise ratio(SNR) and contrast to noise ratio(CNR) with soft tissue by setting up an area of interest on CCA bifurcatoin, ICA, ECA, MCA and VA concerning obtained image. In case of qualitative analysis, 3 radiological technologists and 1 radiologist evaluated 4 items (1: Visibility of the blood vessel, 2: Image distortion measure, 3: Overlapping measure with vein, 4: Peripheral blood vessel description measure) into five points scale (1: Very bad, 2: Bad, 3: Normal 4: Good, 5: Very good). Results : Results for the quantitative analysis was obtained by calculating the average of 5 ROIs in case of SNR and CNR separately. Results of SNR, TOF were generally measured higher than CEA (In case of TOF were 166.1, 205.2, 154.39, 172.23, 161.95, and CEA were 92.05, 95.43, 84.76, 73.69, 88.3). But according to the result of CNR, both TOF and CEA were measured similarly as 67.62, 106.71, 55.9, 73.74, 63.46 for TOF and 67.82, 71.19, 60.52, 49.45, 64.07 for CEA. Throughout every results of each ROI, SNR showed statistically meaningful consequence (0.050.05). In case of qualitative analysis the average of each evaluated item was 4.2points and 4.28points in the item1, 2.93points and 4.55points in the item2, 4.6points and 3.13points in the item3, 2.88points and 4.6points in the item4. According to the results TOF was measured higher in the item3 while in the item2 and item4 CEA was higher and in case of the item1, both CEA and TOF were similar. To sum up statistically meaningful results (p<0.05) were shown in the item2, item3 and item4 but not in the item1 (p>0.05). Conclusions : Both TOF and CEA are complementary because each inspection has pros and cons, but when inspect wide area including Aortic arch normally CEA is conducted. But TOF inspection also can be considered as alternative in terms of patients who has difficulty in the contrast medium such as infants, pregnant women and patients suffering from kidney failure and patients during follow up.

• Progress in Medical Physics
• /
• v.19 no.3
• /
• pp.150-156
• /
• 2008

An applied technique of contrast enhancement for X-ray image is proposed which is based on combined enhancement of scaling and wavelet coefficients in discrete wavelet transform space. Conventional contrast enhancement methods such as contrast limited adaptive histogram equalization (CLAHE), multi-scale image contrast amplification (MUSICA) and gamma correction were applied on scaling coefficients to enhance the contrast of an original. In order to enhance the detail as well as reduce the blurring caused by up scaling of contrast modified scale coefficients from lower resolution, the sigmoid manipulation function was used to manipulate wavelet coefficients. The contrast detail mammography (CDMAM) phantom was imaged and processed to measure the image line profile of results and contrast to noise ratio (CNR) comparatively. The proposed technique produced better results than direct application of various contrast enhancement methods on image itself. The proposed method can enhance contrast, and also suppress the amplification of noise components in a single process. It could be useful for various applications in medical, industrial and graphical images where contrast and detail are of importance.

• Korean Journal of Radiology
• /
• v.20 no.5
• /
• pp.729-738
• /
• 2019

Objective: To assess the effects of iterative model reconstruction (IMR) on image quality for demonstrating non-calcific high-risk plaque characteristics of coronary arteries. Materials and Methods: This study included 66 patients (53 men and 13 women; aged 39-76 years; mean age, 55 ± 13 years) having single-vessel disease with predominantly non-calcified plaques evaluated using prospective electrocardiogram-gated 256-slice CT angiography. Paired image sets were created using two types of reconstruction: hybrid iterative reconstruction (HIR) and IMR. Plaque characteristics were compared using the two algorithms. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the images and the CNR between the plaque and adjacent adipose tissue were also compared between the two reformatted methods. Results: Seventy-seven predominantly non-calcified plaques were detected. Forty plaques showed napkin-ring sign with the IMR reformatted method, while nineteen plaques demonstrated napkin-ring sign with HIR. There was no statistically significant difference in the presentation of positive remodeling, low attenuation plaque, and spotty calcification between the HIR and IMR reconstructed methods (all p > 0.5); however, there was a statistically significant difference in the ability to discern the napkin-ring sign between the two algorithms (χ² = 12.12, p < 0.001). The image noise of IMR was lower than that of HIR (10 ± 2 HU versus 12 ± 2 HU; p < 0.01), and the SNR and CNR of the images and the CNR between plaques and surrounding adipose tissues on IMR were better than those on HIR (p < 0.01). Conclusion: IMR can significantly improve image quality compared with HIR for the demonstration of coronary artery and atherosclerotic plaques using a 256-slice CT.

• The Journal of the Korea Contents Association
• /
• v.19 no.12
• /
• pp.517-526
• /
• 2019

The purpose of this study is to find the optimal method for clinical application by analyzing image quality and radiation output according to parameter combination when using the Automatic Exposure Control (AEC). The experimental method combines 70, 81 kVp with sensitivity S200, S400, S800 and S1000 of the Automatic Exposure Control for Entrance Surface Dose (ESD), current volume, Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), Time-to-Radiation Dose Curve in abdomen and pelvis. And then, image quality and radiation output stability were evaluated. As a results, Entrance Surface Dose, current volume, Signal to Noise Ratio, Contrast to Noise Ratio decreased as the tube voltage and sensitivity were set higher. In addition, the higher tube voltage and sensitivity, the Time-to-Radiation Dose Curve showed a poor output stability. In conclusion, the higher the combination of tube voltage and sensitivity in the use of Automatic Exposure Control, the more problems can be seen in image quality and stability of the radiation output. Therefore, a relatively low combination of tube voltage and sensitivity showed that the image quality and radiation output stability could be optimized by minimizing the error range that would occur when the detector recognized a combination of parameters.

• Journal of the Korean Society of Radiology
• /
• v.8 no.5
• /
• pp.271-278
• /
• 2014

The purpose of this study is to know optimized fat suppression techniques for brachial plexus compared with STIR and SPAIR T1, T2 techniques. A total of 30 normal volunteers without brachial plexus disease were studied on a 3.0 T MRI scanner. As an analytical method, SNR, CNR, 4-point grading scale were evaluated by using three pulse sequences. As a quantitative analysis, the SNR, CNR for SPAIR T1 technique provided high value in branchial plexus roots (03.07, -2.25), branchial plexus trunks(06.70, 36.31)(p<0.05). As a qualitative Analysis, The visibility for delineation of brachial plexus, fat suppression, artifact was significantly better on SPAIR T1(3.2, 3.6, 3.4) technique(p<0.05).

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.12
• /
• pp.247-253
• /
• 2013

The purpose is a comparative evaluation in the DR System according to the dosimetry and image quality of the quantitative and objective via Direct digital radiography, Indirect digital radiography, Image intensifier (Charge Coupled Device type) digital radiography. The experimental method used rando phantom and measured the entrance surface dose. And through using the measured entrance surface dose and then using the PCXMC program were evaluated risk due to irradiation and the effective dose. SNR and NPS and CNR were measured and analyzed by using 21cm acryl phantom. Significance of measured value was evaluated by statistics method. Entrance surface dose, major organ dose, effective dose all of them were measured the lowest rated in direct DR when it is on the basis of direct DR dose, high-dose ratio were measured in I.I DR approximately 1.3 times, indirect DR approximately 2.4 times. Risk in accordance with radiation also was measured same as dose ratio. On the conclusion that SNR measurement result based on direct DR SNR measurements, low-SNR ratio were measured in I.I DR approximately 7.25 times, indirect DR approximately 1.48 times. On the conclusion that CNR measurement result based on direct DR CNR measurements, high-dose ratio were measured in I.I type DR approximately 1.16 tims and low-dose ratio were measured in indirect DR approximately 0.87 times. Therefore Direct DR system using a-selenium sensing element to detect x-ray photon is thought effectively at the examination such as infant to sensitive irradiation and the genital gland. Because quality image is built by low dose. Also when it is necessary that image test requiring many diagnosis information, indirect DR system is thought effectively.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1527-1532
• /
• 2023

The noise reduction algorithm using the non-local means (NLM) approach is very efficient in nuclear medicine imaging. In this study, the applicability of the NLM noise reduction algorithm in single-photon emission computed tomography (SPECT) images with a brain phantom and the optimization of the NLM algorithm by changing the smoothing factors according to various reconstruction methods are investigated. Brain phantom images were reconstructed using filtered back projection (FBP) and ordered subset expectation maximization (OSEM). The smoothing factor of the NLM noise reduction algorithm determined the optimal coefficient of variation (COV) and contrast-to-noise ratio (CNR) results at a value of 0.020 in the FBP and OSEM reconstruction methods. We confirmed that the FBP- and OSEM-based SPECT images using the algorithm applied with the optimal smoothing factor improved the COV and CNR by 66.94% and 8.00% on average, respectively, compared to those of the original image. In conclusion, an optimized smoothing factor was derived from the NLM approach-based algorithm in brain SPECT images and may be applicable to various nuclear medicine imaging techniques in the future.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.19 no.1
• /
• pp.30-36
• /
• 2015

Purpose Whole body bone scan, which makes up a largest percentage of nuclear medicine tests, has high sensitivity and resolution about bone lesion like osteomyelitis, fracture and the early detection of primary cancer. However, any standard for valuation has not yet been created except minimum factor. Therefore, in this study, we will analysis the method which show a quantitative evaluation index in whole body bone scan. Materials and Methods This study is conducted among 30 call patients, who visited the hospital from April to September 2014 with no special point of view about bone lesion, using GE INFINIA equipment. Enumerated data is measured mainly with patient's whole body count and lumbar vertabrae, and the things which include CNR (Contrast to Noise ratio), SNR (Signal to Noise ratio) are calculated according to the mean value signal and standard deviation of each lumbar vertabrae. In addition, the numerical value with the abdominal thickness is compared to each value by the change of scan speed and tissue equivalent material throughout the phantom examination, and compared with 1hours deleyed value. Completely, on the scale of ten, 2 reading doctors and 5 skilled radiologists with 5-years experience analysis the correlation between visual analysis with blind test and quantitative calculation. Results The whole body count and interest region count of patients have no significant correlation with visual analysis value throughout the blind test(P<0.05). There is definite correlation among CNR and SNR. In phantom examination, Value of the change was caused by the thickness of the abdomen and the scan speed. And The poor value of the image in the subject as a delay test patient could be confirmed that the increase tendency. Conclusion Now, a standard for valuation has not been created in whole body bone scan except minimum factor. In this study, we can verify the significant correlation with blind test using CNR and SNR and also assure that the scan speed is a important factor to influence the imagine quality from the value. It is possible to be some limit depending on the physiology function and fluid intake of patient even if we progress the evaluation in same condition include same injection amount, same scan speed and so on. However, that we prove the significant evaluation index by presenting quantitative calculation objectively could be considered academic value.

• Journal of the Korean Society of Radiology
• /
• v.13 no.5
• /
• pp.765-771
• /
• 2019

Noise in skull X-ray imaging is inevitable, which reduces imaging quality and diagnostic accuracy and increases errors due to the nature of digital imaging devices. Increasing the dose can attenuate noise, but that could lead to big problems with higher exposure dose received by patients. Thus, noise reduction algorithms are actively being studied at low doses to solve dose problems and reduce noise at the same time. Wiener filter and median filter have been widely used, with the disadvantages of poor noise reduction efficiency and loss of much information about imaging boundary. The purpose of this study is to apply total variation (TV) algorithm to skull X-ray imaging that can compensate for the problems of previous noise reduction efficiency to assess quantitatively and compare them. For this study, skull X-ray imaging is obtained using various kVp and mAs using the skull phantom using the X-ray device of Siemens. In addition, contrast to noise ratio (CNR) and coefficient of variation (COV) are compared and measured when noisy image, median filter, Wiener filter and TV algorithm were applied to each phantom imaging. Experiments showed that when TV algorithms were applied, CNR and COV characteristics were excellent under all conditions. In conclusion, we've been able to see if we can use TV algorithm to improve image quality and CNR could be seen to increase due to the decrease in noise as the amount of increased mAs. On the other hand, COV decreased as the amount of increased mAs, and when kVp increased, noise was reduced and the transmittance was increased, so COV was reduced.