• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.679-685
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• 2017

Computed tomography has widely been used to diagnose patient disease, and patient dose also increase rapidly. To reduce the patient dose by CT, various techniques have been applied. The iterative reconstruction is used in view of image reconstruction. Image quality of the reconstructed section image through algebraic reconstruction technique, one of iterative reconstruction methods, was examined by the normalized root mean square error. The computer program was written with the Visual C++ under the parallel beam geometry, Shepp-Logan head phantom of $512{\times}512$ size, projections of 360, and detector-pixels of 1,024. The forward and backward projection was realized by Joseph method. The minimum NRMS of 0.108 was obtained after 10 iterations in the regularization parameter of 0.09-0.12, and the optimum image was obtained after 8 and 6 iterations for 0.1% and 0.2% noise. Variation of optimum value of the regularization parameter was observed according to the phantom used. If the ART was used in the reconstruction, the optimal value of the regularization parameter should be found in the case-by-case. By finding the optimal regularization parameter in the algebraic reconstruction technique, the reconstruction time can be reduced.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.637-645
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• 2017

The objective of this study was to find the optimum test device for the cerebral blood vessels by comparing and analyzing the SNR and CNR methods for images of three devices (i.e., MRA, CTA, and DSA). The study targeted 90 patients who underwent cerebral angiography from November 2016 to May 2017. The measuring parts were measured by using Rt MCA, Lt MCA, and ACA Image J. The results of quantitative analysis showed that the mean SNR of MRA, the CNR of MRA, the signal strength of MRA, the mean SNR of CTA, the CNR of CTA, the signal strength of CTA, the SNR of DSA, the CNR of DSA, and the signal strength of DSA were evaluated as 254.87, 178.13, 326.81, 74.75, 62.2, 356.66, 26.85, 25.89, and 4400.69, respectively (p<0.05). As a result, both SNR and CNR methods measured it in the order of MRA>CTA>DSA. Statistical significance was determined by using ANOVA analysis at p<0.05 and Bonferroni method was used as a post-hoc analysis SPSS. In conclusion, the results of this study revealed that the optimum imaging devices were MRA, CTA, and DSA after evaluating randomly selected patients with cerebrovascular disease.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.715-723
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• 2020

Cross-talk artifacts occur in two adjacent groups of axial imaging of lesions lumbar 4-5 and sacrum 1 in lumbar spine MRI. This causes problems in reading lesions in areas corresponding to the posterior vertebra. In this study, we are going to completely remove the cross-talk artifacts through optimal concatenation TR. The region of interested were measured by averaging them into fat (ROI1), erector spinal muscle(lateral tract: iliocostalis lumborum muscle) (ROI2), erector spinal muscle(lateral tract: longissimus muscle) (ROI3), and spinous process (ROI4). The mean signal intensity (SI) was 163.43 ± 25.08 at C4 for ROI1, ROI 2 and ROI 3 at C6, 67.89 ± 11.75 and 69.99 ± 10.91 and ROI4 at C5, respectively (p<0.000). The mean signal to noise ratio (SNR) was 135.45 ± 35.90, 56.92 ± 15.90, 58.77 ± 15.59, and 54.91 ± 118.95 for SNR 1, 2, 3 and 4 (p<0.000). The contrast-to-noise ratio (CNR) was CNR1 78.52 ± 24.11, CNR2 was 76.67 ± 24.38 and CNR3 was 80.54 ± 26.33 in concatenation 6, respectively (p<0.000). The SNR, CNR, and the most efficient concatenation TR value over time are 6, and it is considered to help reduce cross-talk artifact if this is applied to T1 axial images.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.627-634
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• 2020

Instead of lead, we intend to develop shielding materials for morphological implementation by mixing barium sulfate, an eco-friendly substance, and PLA filament, a 3D printer material. The environmental substance, barium sulfate powder and PLA filament, a 3D printer material, were used, and the shielding was made with a 3D printer after being fused into an extruder to mix the powder powder of barium sulfate with PLA. To check the mixing ratio of barium sulfate powder and PLA filament, the mixing input was analyzed, and the absorption dose by thickness according to barium sulfate content was obtained to check the shielding function of the mixed shielding. In the evaluation of the mixture of sulfate barium powder particles and PLA filaments, it was mixed in the most appropriate proportion when the content was 30% in the apparent and electron microscopic observation photographs. In the absorption dose results by thickness according to barium sulfate content, the difference between the content of 0% and the content of each % was greatest at 0.5 cm in thickness and the lowest dose value at 3 cm in thickness when the barium content was 30%. In addition, as the barium content began to increase at 30%, the absorbed dose value increased again. Instead of conventional lead, barium sulfate, an eco-friendly substance, could be mixed with PLA, a filament material, to create morphological shielding. Based on this study, it is expected that the mixing ratio of barium to the mixture is the most appropriate 30%, and will be used as the basis for the implementation of morphological shielding using 3D printers in the diagnosis and treatment section.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.685-693
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• 2020

This study was performed to compare the differences between total fat area, subcutaneous fat area and visceral fat area according to L1-S1 inter vertebral disc level in asymptomatic Korean patients with non-contrast abdominal CT scan. The location of the maximum fat ratio of the total fat area is the total fat area measured in male L2-3, L3-4, L4-5, female L4-5, and L5-S1. The location showing the maximum fat ratio of the subcutaneous fat area is the subcutaneous fat area measured in male L4-5, and the woman is the subcutaneous fat area measured in L4-5 and L5-S1. The location of the maximum fat ratio of visceral fat area was the visceral fat area measured in L1-2 and L2-3 males, and there was no difference in visceral fat area according to the measured position in females. Although abdominal fat measurement is common at the L4-5 inter vertebral disc level, fat distribution varies widely depending on nationality, race, and gender. Therefore, it is necessary to analyze through the research data which location to choose according to the research purpose, and to mention why the location is appropriate.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.503-510
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• 2020

Concrete is one of the most widely used materials as the shielding structures of a nuclear facilities. It is also the most generated radioactive waste in quantity while dismantling facilities. Since the concrete captures neutrons and generates various radionuclides, radiation measurement and analysis of the sample was fulfilled prior to dismantle facilities. An HPGe detector is used in general for the radiation measurement, and effective correction factors such as geometrical correction factor, self-absorption correction, and absolute detector efficiency have to be applied to the measured data to decide exact radioactivity of the sample. Correction factors are obtained by measuring data using a standard source with the same geometry and chemical states as the sample under the same measurement conditions. However, it is very difficult to prepare standard concrete sources because concrete is limited in pretreatment due to various constituent materials and high density. In addition, the concrete sample obtained by core drill is a volumetric source, which requires geometric correction for sample diameter and self absorption correction for sample density. Therefore in recent years, many researchers are working on the calculation of effective correction factors using Monte carlo simulation instead of measuring them using a standard source. In this study we calculated, using Geant4, one of the Monte carlo codes, the correction factors for the various diameter and density of the concrete core sample at the gamma ray energy emitted from the nuclides ¹⁵²Eu and ⁶⁰Co, which are the most generated in radioactive concrete.

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.139-146
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• 2017

At the Brain MRI examination, RF Pulse are irradiated on the human head in order to acquire MR images. At this time, a considerable part of the irradiated RF Pulse energy is absorbed in our body and the temperature of the human head will rise depending on the degree of exposure, so it will affect the human head. Even if the same RF Pulse energy is given, if the metal is inserted in the human head, the conductivity of the human head is greatly increased by the metal, so the SAR value increases and the temperature also rises. Therefore, we started this research with the question as to whether there is difference between the change in SAR value and temperature displayed on the head of the human according to use or not of the dental implant. Experiments were using the XFDTD program on a 128 MHz RF Pulse frequency by a 3.0 tesla MRI. We can see that both are increasing that the average value of SAR and temperature that absorbed by the human head model used the dental implant. In addition, the average maximum SAR value and the maximum temperature rise in the brain part are shown below the international safety standard value but the influence can not be ignored because of the result may change according to the increase in the number of dental implant. And as future tasks. we need to the simulation of temperature rise and SAR due to an increase in the number of implants and volumes of teeth, dental implant material.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.287-291
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• 2005

To determine the appropriate session for changing treatment modality according to the size of proximal ureter stone with complete obstruction, We analyzed 201 patients with proximal ureter stone primarily treated by Dornier MPL 9000 lithotripter from January, 2002 to August, 2004. Of total 201 patients, the patients without complete obstruction were 142, and with complete obstruction were 59. In the patients without complete obstruction, the accumulative stone free rate of the first, second, and third session were 68.3%, 86.6%, and 94.4%, respectively. The accumulative stone free rate according to the stone size at third session were 100%, 90.5%, 00.0% in stones less than 10 mm, 10 to less than 20 mm, and larger than or 20 mm, respectively. In the patients with complete obstruction, the accumulative stone free rate of the first, second, and third session were 44.1%, 66.1%, and 76.3%, respectively. The accumulative stone free rate according to the stone size at third session were 100%, 65.5%, 33.3% in stones less than 10 mm, 10 to less than 20 mm, and larger than or 20 mm, respectively. In our study, the size of proximal ureter stone with complete obstruction influenced noticeably on the success rate of extracorporeal shock wave lithotripsy (ESWL). We propose that the proximal ureter stones larger than or 10 mm with complete obstruction are treated by ureteroscopic manipulation than ESWL as the first line treatment modality.

• Journal of radiological science and technology
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• v.33 no.2
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• pp.85-91
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• 2010

Digital radiography has been replacing rapidly the analog radiography for diagnosis of pneumoconiosis. The purpose of this study is to compare quality control of digital radiography (DR) and analog radiography (AR) for chest radiography in medical institution for pneumoconiosis (MIP) For the first time, we visited MIP to evaluate the chest radiography which is used for patients with pneumoconiosis, including equipment, technical parameters and reading environment. There were 33 institutions. DR and AR were installed in 24 and 9 institutions, respectively. Between DR and AR, we compared the radiological technique (RT), image quality (IQ) and reading environment (RE) to use the guideline published by Occupational Safety and Health Research Institute (OSHRI). The image quality was rated by two experienced chest radiologists for pneumoconiosis with certified from OSHRI. The chest radiography equipment was not significantly difference between AR and DR, but there were significantly difference in tube voltage and grid ratio used for chest radiography except to tube current, exposure time. Statistically, DR is significantly higher in RT(70.3 vs. 43.8, p = 0.009), RE(77.7 vs. 33.3, p = 0.004) than AR, but it's not significantly difference in IQ (65.6 vs. 52.8, p = 0.050). AR and DR in RT were passed 33.3%, 75.0% respectively (p = 0.044) and 44.4%, 79.2% (p = 0.090) in IQ and 44.4%, 91.7% (p = 0.009) in RE. In MIP, DR needs to replace AR in diagnosis of pneumoconiosis.

• Journal of radiological science and technology
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• v.43 no.3
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• pp.155-159
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• 2020

The purpose of this study is to investigate the effect of posture changes(Anteroposterior projection, Posteroanterior projection) in the plain abdominal examination on breast dose and to examine its clinical usefulness. This study was used a human body phantom and a glass dosimeter. Glass dosimeters were directly inserted from the center and outside of medial and lateral. In this study, the deep dose was measured in the right breast and the surface dose in the left breast. During the abdominal examination, the central X-ray incident point was perpendicularly incident to the image receptor 5 cm above the iliac crest. The exposure parameters were 82 kVp, 320 mA, 50 ms, x-ray field size 14×17 inch The distance between the center X-ray and the detector was fixed at 110 cm, and only the top two AEC chambers were used. As a result of this study, the medial and lateral side doses of the right breast were 535.73±30.68 μGy and 414.46±33.52 μGy for erect AP, and 145.80±18.52 μGy and 148.76±12.92 μGy in erect PA. The superficial breast dose was 754.00±68.36 μGy on the medial side and 674.06±45.58 μGy on the lateral side in the erect AP, 70.66±7.98 μGy on the medial side, and 86.46±15.35 μGy on the lateral side in the erect PA. There was a statistically significant difference in the difference between the mean values of the medial and lateral side doses in the deep and superficial areas of the breast according to the postural change (p <0.01). As a result of this study, If the abdominal radiography was examined in the PA position, the dose reduction effect was 72.78% on the medial side, 64.10% on the lateral side of the deep breast, 90.62% on the medial side, and 87.17% on the lateral side of the superficial breast compared to the AP position.