• Journal of radiological science and technology
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• v.36 no.2
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• pp.111-122
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• 2013

This study was carried out to reduce patient dose through focus-detector distance, kilovoltage, and a combination of copper filters. In the C, L-spine lateral, Skull AP views were obtained by making changes of 60-100 kV in tube voltage and of 100-200 cm in focus-detector distance and by adding a copper filter when using an auto exposure control device in the digital radiography equipment. The incident dose showed 90 kV, 0.3 mmCu in C-spine lateral with 0.06 mGy under the condition of 200 cm; 100 kV, 0.3 mmCu with 0.40 mGy under the condition of 200 cm and 90 kV 0.3 mmCu in Skull AP with the lowest value of 0.24 mGy under the condition of 140 cm. It was observed that entrance surface dose decreased the most when was increased by 150 cm, 70 kV (C-spine lateral), 81 kV (L-spine lateral). It was also found out that as the between the focus-detector increased in the expansion of the video decreased but the difference was not significant when the distance was 180 cm or more. Skull AP showed the most reduction in the entrance surface dose when the tube voltage was changed by 80 kV, 0.1 mmCu, and 120 cm. Therefore, when using the automatic exposure control device, it is recommended to use the highest tube voltage if possible and to increase focus-detector distance at least by 150~200 cm in wall and 120~140 cm in table in consideration of the radiotechnologist's physical conditions, and to combine 0.1~0.3 mmCu and higher filters. It is thus expected to reduce patient dose by avoiding distortion of images and reducing the entrance surface dose.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.245-251
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• 2017

This study measured the exposure dose during abdominal-pelvic CT exam which occupies 70% of CT exam and tried to propose a protocol for optimized exposure dose in abdomen and pelvis without affecting the imagery interpretation. The study scanned abdomen-pelvis using the current clinical scan method, the 120 kVp, auto exposure control(AEC), as 1 phase. As for the newly proposed 2 phase scan method, the study divided into 1 phase abdomen exam and 2 phase pelvis exam and each conducted tube voltage 120 kVp, AEC for abdomen exam, and fixed tube current method in 120 kVp, 100, 150, 200, 250, 300, 350, 400 mA for pelvis exam. The exposure dose value was compared using $CTDI_{VOL}$, DLP value measured during scan, and average value of CT attenuation coefficient, noise, SNR from each scan image were obtained to evaluate the image. As for the result, scanning of 2 phase showed significant difference compared to 1 phase. In $CTDI_{VOL}$ value, the 2 phase showed 26% decrease in abdomen, 1.8~59.5% decrease in pelvis for 100~250 mA, 12.7%~30% increase in pelvis for 300~400 mA. Also, DLP value showed 53% decrease in abdomen and 41~81% decrease in pelvis when scanned by 2 phase compared to 1 phase, but it was not statistically significant. As for the SNR, when scanning 2 phase close to heart, scanning 1 phase close to pelvis, scanning and scanning 1 phase at upper and lower abdomen, it was higher when scanning 2 phase for 200~250 mA. Also, the CT number and noise was overall similar, but the noise was high close to pelvis. However, when scanning 2 phase for 250 mA close to pelvis, the noise value came out similar to 1 phase, and did not show statistically significant difference. It seems when separating pelvis to scan in 250 mA rather than 400 mA in 1 phase as before, it is expected to have reduced effect of exposure dose without difference in the quality of image. Thus, for patients who often get abdominal-pelvic CT exam, fertile women or children, this study proposes 2 phase exam for smaller exposure dose with same image quality.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.29-34
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• 2012

Purpose : Presently, hardwares and softwares for reducing radiation exposure are continually developed for PET/CT examination. Purpose of this study is to evaluate effectiveness of reducing radiation exposure dose of CT and SUV changes of PET when applied each kernel to ACCT (Attenuation Correction Computed Tomography) according to adopted IRIS (Iterative Reconstruction in Image Space) software. Materials and Methods : Biograph mCT (Siemens, Germany) was used as a PET/CT scanner. Using AAPM CT performance phantom, from standard (120 kVp, 100 mAs), 7 scans were conducted by reducing 15 mAs each. After image reconstruction by FBP (Filtered Back Projection) and IRIS, noise and spatial resolution were evaluated. The same method was applied to anthropomorphic chest phantom and acquired images were compared. NEMA IEC body phantom was used for SUV evaluation. Injected dose rate for hot sphere (hot) and background cylinder (BKG) were 1:8. CT dose condition (120 kVp, 50 mAs) was the same for each scan and PET scan durations were 1, 2, 3 and 4min. After scanning, each kernel of IRIS was applied to ACCT. And PET images were reconstructed by ACCT adopted IRIS for comparing SUV changes. Results : AAPM phantom test for noise evaluation, SD for FBP 100 mAs, IRIS 55 mAs were 8.8 and 8.9. FBP 85 mAs, IRIS 40 mAs were 9.5 and 9.7. FBP 70 mAs, IRIS 25 mAs were 11.9 and 11.1. Above mAs condition for FBP and IRIS, SD showed similar values. And for spatial resolution test, there was no significant difference. For chest phantom test, when applied the same mAs and kernel to both of FBP and IRIS, every applied kernels showed reduced noise. Lower mAs and higher kernel value showed higher noise reduction. There was no considerable difference only except for I70 very sharp kernel for SUV comparison using NEMA IEC body phantom. Conclusion : In this study, low mAs (55 mAs) applied IRIS and standard mAs (100 mAs) applied FBP showed similar noise. And only except for I70 kernel, there was no significant SUV changes. It is possible to reduce needless radiation exposure and acquire better image quality than FBP's through applying appropriate kernel of IRIS to PET/CT.

• The Journal of the Korea Contents Association
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• v.14 no.1
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• pp.356-363
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• 2014

Recently pediatric CT has been performed by reduced dose according to tube current modulation이라고, this fact has a possibility more reduce a dose because of strong affect depend on tube current modulation. Almost all MDCT snow show and allow storage of the volume CT dose index (CTDIvol), dose length product (DLP), and effective dose estimations on dose reports, which are essential to assess patient radiation exposure and risks. To decrease these radiation exposure risks, the principles of justification and optimization should be followed. justification means that the examination must be medically indicated and useful. Results is using tube current modulation이라고 tend to the lower kV, the lower effective dose. In case of use a low dose CT protocol, we found a relatively lower effective dose than using tube current modulation. Average effective dose of our studies(brain, chest, abdomen-pelvis) less than 47%, 13.8%, 25.7% of germany reference dose, and 55.7%, 10.2%, 43.6% of UK(United Kingdom) reference dose respectively. when performed examination for reduced dose, we must use tube current modulation and low dose CT protocol including body-weight based tube current adaption.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.151-152
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• 2015

유방 검사에서 Tomosynthesis는 Mammogram과 비교하여 유방 병변 구별에 우수하고 확연한 대조도 차이를 보이며 추가적인 유방촬영 검사나 재촬영을 감소시킴으로서 장기적으로 환자의 피폭선량이 감소하는 효과를 보이므로 유방 병변 진단의 효과를 높일 수 있는 유용한 검사이다.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.25-28
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• 2012

Purpose : It is important to reduce radiation dose associated with computed tomography (CT) scanning to as low as reasonably achievable (ALARA). With Dose Modulation Technic, user select a desired image quality and the system adapts tube current to obtain the desired image quality with greater radiation dose efficiency. In this paper, we presents a comprehensive description of fundamentals, clinical applications and radiation dose benefits of Dose Modulation Technic depending on Body Mass Index(BMI). Materials and Methods : In this study, 149 patients were examined(The mean age : $58{\pm}12.4$ years old). Biograph True Point 40 (Siemens, USA) and Gemini TF 64 (Philips. Cleveland) were used for equipment. When we used Care Dose 4D (Siemens, USA) and D-dom (Philips, Cleveland), we measured dose reduction and Computed Tomography Dose Index (CTDI) depending on BMI. Then we analyze data using SPSS Ver.18. Results : When we used Care Dose 4D, p-value is considered statistically significant by groups with the result that we compared Care Dose 4D with D-dom. On the other hand, p-value isn't considered statistically significant by groups using D-dom. Conclusion : Dose modulation based on the projection angle didn't affect degree of obesity. And When using Care Dose 4D, dose reduction rate in the normal patients were higher than the obese. In this study, there are errors on somato type. So I think more research have to be done. Then application of Dose Modulation technic can help in maintaining acceptable image quality while reducing radiation dose by 20-60% in most instances.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.41-44
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• 2010

Purpose: Along with recent advances in PET/CT instrumentation and imaging technology, the number of patients has also been steadily increasing. This resulted in the increased radiation exposure to radiation workers in PET/CT rooms. In this study, we installed a radiation shield and investigated whether it could reduce radiation exposure to the workers and thus enhance job satisfaction. Materials and Methods: A radiation shield is composed of 5 cm thick lead and has a structure in which a radiation worker sits and watches a patient through lead glass while injecting radiopharmaceutical to the patient. Quarterly absorbed dose of radiation workers was measured using thermoluminescence dosimeters (TLD) and the results were compared for six months each before and after installation of the radiation shield. Exposure dose was also measured using a pocket dosimeter placed at the same location in the front and the back of the radiation shield. In addition, frequency of use of the shield and job satisfaction of radiation workers were investigated using a survey. Results: Quarterly absorbed dose of radiation workers was 2.70 mSv on average before installation of new radiation shield, whereas that dropped to 2.13 mSv after installation of radiation shield, reducing radiation exposure dose by 21%. Exposure dose on the front side of the shield was 61.2 R, whereas that on the back side of shield was 2.8 R. According to the survey, 85% of workers used the shield and were satisfied with the outcome: each radiation worker made injections to patients average of 6.5 times/day and preferred sitting to standing while injecting radiopharmaceutical to patients. Conclusion: Use of radiation shield reduced the exposure dose of radiation workers, which is the ultimate goal of radiation protection to minimize radiation exposure and is an appropriate method for the improvement of hospital working environment. Furthermore, we found that use of radiation shield not only relieves physical and psychological burden of radiation workers but also enhances job satisfaction. This result indicates that use of radiation shield is important for improvement of the radiation workers' job environment in terms of radiation protection.

• Journal of radiological science and technology
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• v.39 no.3
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• pp.313-321
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• 2016

Placenta accrete patients whose mother mortality rates are rather high due to massive bleeding during childbirth need to have Prophylactic placement of Internal Iliac Artery Balloon Occlusion Catheters procedure to reduce amount of blood loss and inoperative transfusion. Nevertheless, studies for mothers inevitably exposed to dose during PIIABOCs procedure have not been published many yet. Therefore, this study is to investigate exact information on radiation dose exposed to fetus during PIIABOCs procedure. Average effective dose of fetus per organ is 2.38~8.83 mGy, measured highest at beam center and followed by eyeball, stomach and bladder. The result showed that the longer fluoroscopy time is used, the closer beam center is and the thicker abdominal thickness is, the more effective dose on fetus is increasing. When using the collimator and protection shown to decrease the effective dose and when using higher the patient table shown to decrease the effective dose. It has been reported that the threshold of deterministic effect is about 100mGy. Deterministic effect was regarded as a factor that would influence on fetus exposed by medical radiation than stochastic effect. Consequently, it concluded that dose exposed on fetus in PIIABOCs procedure was approximately 10% of threshold of deterministic effect with effective dose of 0.49~18.27 mGy.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.579-587
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• 2017

Although interventional procedures use very low tube currents, there is a high risk of exposure to radiation as well as the operator due to long-term radiation exposure. The purpose of this study is to investigate the effects of radiation dose on the quality of the operator by measuring the dose received by the operator in the interventional procedure of the cerebral vascular system and finding the shielding material and shielding method which can effectively shield the exposure from the medical radiation. And to find a way to minimize it to the extent that it does not. As a result, when the newly designed shielding system with Nano Tungsten material was used, it was confirmed that the mean dose was reduced by 7.95% on average by the operator. Also, the PSNR results were measured to be 38.44 dB when using the designed shielding material, and it was confirmed that Nano Tungsten does not affect the image quality. In conclusion, the Nano Tungsten shielding material proved to be capable of significantly reducing the operator radiation dose, without affecting the image quality. The use of the above materials is expected to solve the problems related to the harmfulness and economical efficiency of the human body and the environment, which have recently become an issue of shielding materials.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.473-478
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• 2015

Abdominal obesity is one of the most influential index to predict of insulin resistance syndrome/metabolic syndrome in social demographic characteristics. It is matter of fact that radiation dose are increasing with development of medical treatment and device. In this study, we estimated distortion between reference image and entrance surface dose when take a chest radiography forward chest phantom assumed abdominal obesity. When angle of chest phantom incline $5^{\circ}$ forward, thoracic transverse and longitudinal diameter increase 1.22% and 0.44% each. Also cardiac transverse diameter increase 1.01% and cardio-throracic ratio (CTR) decrease 0.27% in the same situation of incline to $5^{\circ}$ forward. Thoracic transverse diameter shows the largest increase, and CTR was decreased. But entrance surface dose to phantom increase significantly 6.12% when angle of chest phantom incline $5^{\circ}$ forward. In conclusion, we have to pay attention to accurate positioning, to prevent a distortion of image through incline, and make patients not to expose to additional radiation.