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

• Radiation Oncology Journal
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• v.1 no.1
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• pp.21-24
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• 1983

The thickness of the part being irradiated is finite. Percent depth dose tables being used routinely are generally obtained from dosimetry in a phantom much thickner than usual patient. At or close to exit surface, the dose should be less than that obtained from the percent depth dose tables, because of insufficient volume for backscattering. To know the difference between the true absorbed dose and the dose obtained from percent depth dose table, the doses at or close to the exit surface were measured with plate type ionization chamber with volume of 0.5ml. The results are as follows; 1. In the case of $^{60}Co$, percent depth dose at a given depth increases with underlying phantom thickness up to the 5cm. 2. In the case of $^{60}Co$, the dose correction factor at exit surface which is less than 1, increases with part thickness and decreases with field size. 3. Exposure time may not be corrected when the part above 10cm in thickness is treated by $^{60}Co$. 4. In the case of 10MV x-ray, the dose correction factor is nearly 1 and constant for the underlying phantom thickness and field size, so the correction of monitor unit is not necessary for part thickness.

• Journal of radiological science and technology
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• v.18 no.1
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• pp.63-70
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• 1995

In this pauper, the back, forward, side and $45^{\circ}$ oblique scatter dose were measured the X-ray exposure conditions 60, 80, 100, 120kV, FFD 100cm, FS $20\times20cm$, toward the $25\times25cm\times10\sim20cm$ of solid water, paraffin and MiX-DP phantom, and Pb, Cu, Al, and styrofoam meterials, by the electrometer and 5.3 cc ionization chamber. The obtained results are summarized as following. 1. The percentage depth dose(PDD) at the range of the diagnostic x-ray energy were appeared 50 % depth dose at the 2 cm depth with 60 kV, and 5 cm depth with 120 kV X-ray, 10 % depth dose at the 10 cm depth with 60 kV and 14 cm depth with 120 kV X-ray, 5 % below depth dose at the 20 cm depth. 2. The back scatter dose which were generated the surface of Pb, Cu and Al metal plates were 10 % below, and than the back scatter dose at the Pb plate were a most amount of these which were about 10 %, and were appeared the order of Cu and Al. 3. The percentage forward scatter were appeared from 50 % to 65 %, and the more phantom thicknees become, the more forward scatter were increased with the ratio of 5 % per 5 cm thickness. 4. The percentage back scatter which were generated the tissue equivalence meterials solid water, paraffin and MiX-DP were from 20 % to 40 %, and than the back scatter dose at the solid water were a mest amount of those, and paraffin and MiX-DP were appeared with the next values. 5. The percentage $90^{\circ}$ lateral and $45^{\circ}$ oblique side scatter dose were measured from 4 % to 12 %. a most amount of scatter dose which were generated from the patient in radiography were the forward scatter, the next values were the back scatter, the third values were the $90^{\circ}$ lateral scatter.

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.161-169
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• 2017

The cone beam computed tomography(CBCT) which can acquire 3-dimensions images is widely used for confirmation of patient position before radiation therapy. In this study, through the simulation using the Monte Carlo technique, we will analyze the exposure dose by cone beam computed tomography and present the standardized data. For the experiment, MCNPX(ver. 2.5.0) was used and the photon beam spectrum was analyzed after Cone beam was simulated. As a result of analyzing the photon beam spectrum, the average energy ranged from 25.7 to 37.6 keV at the tube voltage of 80 ~ 120 kVp and the characteristic X-ray energy was 9, 60, 68 and 70 keV. As a result of using the water phantom, the percentage depth dose was measured, and the maximum dose appeared on the surface and decreased with depth. The absorbed dose also decreased as the depth increased. The absorbed dose of the whole phantom was 9.7 ~ 18.7 mGy. This is a dose which accounts for 0.2% of about 10 Gy, which is generally used for radiation therapy per week, which is not expected to have a significant effect on the treatment effect. However, it should not be overlooked even if it is small compared with prescription dose.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.110-114
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• 2014

Purpose: The advancement in PET/CT test devices has decreased the test time and popularized the test, and PET/CT tests have continuously increased. However, this increases the exposure dose of radiation workers, too. This study aims to measure the radiation shielding rate of $^{18}F-FDG$ with a strong energy and the shielding effect when worker wore an apron during the PET/CT test. Also, this study compared the shielding rate with $^{99m}TC$ to minimize the exposure dose of radiation workers. Materials and Methods: This study targeted 10 patients who visited in this hospital for the PET/CT test for 8 days from May 2nd to 10th 2013, and the $^{18}F-FDG$ distribution room, patient relaxing room (stand by room after $^{18}F-FDG$ injection) and PET/CT test room were chosen as measuring spots. Then, the changes in the dose rate were measured before and after the application of the APRON. For an accurate measurement, the distance from patients or sources was fixed at 1M. Also, the same method applied to $^{99m}TC's$ Source in order to compare the reduction in the dose by the Apron. Results: 1) When there was only L-block in the $^{18}F-FDG$ distribution room, the average dose rate was $0.32{\mu}Sv$, and in the case of L-blockK+ apron, it was $0.23{\mu}Sv$. The differences in the dose and dose rate between the two cases were respectively, $0.09{\mu}Sv$ and 26%. 2) When there was no apron in the relaxing room, the average dose rate was $33.1{\mu}Sv$, and when there was an apron, it was $22.3{\mu}Sv$. The differences in the dose and dose rate between them were respectively, $10.8{\mu}Sv$ and 33%. 3) When there was no APRON in the PET/CT room, the average dose rate was $6.9{\mu}Sv$, and there was an APRON, it was $5.5{\mu}Sv$. The differences in the dose and dose rate between them were respectively, $1.4{\mu}Sv$ and 25%. 4) When there was no apron, the average dose rate of $^{99m}TC$ was $23.7{\mu}Sv$, and when there was an apron, it was $5.5{\mu}Sv$. The differences in the dose and dose rate between them were respectively, $18.2{\mu}Sv$ and 77%. Conclusion: According to the result of the experiment, $^{99m}TC$ injected into patients showed an average shielding rate of 77%, and $^{18F}FDG$ showed a relatively low shielding rate of 27%. When comparing the sources only, $^{18F}FDG$ showed a shielding rate of 17%, and $^{99m}TC$'s was 77%. Though it had a lower shielding effect than $^{99m}TC$, $^{18}F-FDG$ also had a shielding effect on the apron. Therefore, it is considered that wearing an apron appropriate for high energy like $^{18}F-FDG$ would minimize the exposure dose of radiation workers.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.1
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• pp.44-49
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• 2017

Purpose Radiation exposure management has been strictly regulated for the radiation workers, but there are only a few studies on potential risk of radiation exposure to non-radiation workers, especially nurses in a general ward. The present study aimed to estimate the exact total exposure of the nurse in a general ward by close contact with the patient undergoing nuclear medicine examinations. Materials and Methods Radiation exposure rate was determined by using thermoluminescent dosimeter (TLD) and optical simulated luminescence (OSL) in 14 nurses in a general ward from October 2015 to June 2016. External radiation rate was measured immediately after injection and examination at skin surface, and 50 cm and 1 m distance from 50 patients (PET/CT 20 pts; Bone scan 20 pts; Myocardial SPECT 10 pts). After measurement, effective half-life, and total radiation exposure expected in nurses were calculated. Then, expected total exposure was compared with total exposures actually measured in nurses by TLD and OSL. Results Mean and maximum amount of radiation exposure of 14 nurses in a general ward were 0.01 and 0.02 mSv, respectively in each measuring period. External radiation rate after injection at skin surface, 0.5 m and 1 m distance from patients was as following; $376.0{\pm}25.2$, $88.1{\pm}8.2$ and $29.0{\pm}5.8{\mu}Sv/hr$, respectively in PET/CT; $206.7{\pm}56.6$, $23.1{\pm}4.4$ and $10.1{\pm}1.4{\mu}Sv/hr$, respectively in bone scan; $22.5{\pm}2.6$, $2.4{\pm}0.7$ and $0.9{\pm}0.2{\mu}Sv/hr$, respectively in myocardial SPECT. After examination, external radiation rate at skin surface, 0.5 m and 1 m distance from patients was decreased as following; $165.3{\pm}22.1$, $38.7{\pm}5.9$ and $12.4{\pm}2.5{\mu}Sv/hr$, respectively in PET/CT; $32.1{\pm}8.7$, $6.2{\pm}1.1$, $2.8{\pm}0.6$, respectively in bone scan; $14.0{\pm}1.2$, $2.1{\pm}0.3$, $0.8{\pm}0.2{\mu}Sv/hr$, respectively in myocardial SPECT. Based upon the results, an effective half-life was calculated, and at 30 minutes after examination the time to reach normal dose limit in 'Nuclear Safety Act' was calculated conservatively without considering a half-life. In oder of distance (at skin surface, 0.5 m and 1 m distance from patients), it was 7.9, 34.1 and 106.8 hr, respectively in PET/CT; 40.4, 199.5 and 451.1 hr, respectively in bone scan, 62.5, 519.3 and 1313.6 hr, respectively in myocardial SPECT. Conclusion Radiation exposure rate may differ slightly depending on the work process and the environment in a general ward. Exposure rate was measured at step in the general examination procedure and it made our results more reliable. Our results clearly showed that total amount of radiation exposure caused by residual radioactive isotope in the patient body was neglectable, even comparing with the natural radiation exposure. In conclusion, nurses in a general ward were much less exposed than the normal dose limit, and the effects of exposure by contacting patients undergoing nuclear medicine examination was ignorable.

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.669-675
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• 2018

This study aimed to investigate the difference of X-ray exposure by comparing and analyzing entrance surface dose and absorbed dose according to the frame change in coronary angiography using an X-ray machine. Moreover, appropriate frame selection measures for examination, including the effect of frame change on the image quality, were sought by measuring and analyzing the SNR and CNR of the image through image J. The study was conducted on 30 patients (19 males and 11 females) who underwent CAG at this hospital from June 2017 to October 2017. In regard to the patients, their age range was 49-82 years (mean of $65{\pm}9$ years), body weight was 45-91 kg (mean of $67{\pm}8.9kg$), height was 150-179cm (mean of $165.1{\pm}8.9kg$), and BMI was 19.5-30.5(mean of $24.5{\pm}2.9$). For the entrance surface dose and absorbed dose, air kerma value and DAP were obtained and analyzed retrospectively. The SNR and CNR were measured and analyzed through imageJ, and the result values were derived by applying the values to the formula. As for the statistical analyses, the correlations between the entrance surface dose and absorbed dose, and between the SNR and CNR were analyzed by using the SPSS statistical program. The relationship between the entrance surface dose and absorbed dose was not statistically significant for both 10 f/s and 15 f/s (p>0.05). In terms of the relationship between the SNR and CNR, the SNR ($3.374{\pm}2.1297$) and CNR ($0.234{\pm}0.2249$) in 10 f/s were $1.43{\pm}0.4861$ and $0.132{\pm}0.0555$ lower, respectively, than the SNR ($4.929{\pm}2.8532$) and CNR ($0.391{\pm}0.3025$) in 15 f/s, which were not statistically significant (p>0.05). In the correlation analysis, statistically significant results were obtained among the BMI, air kerma, and DAP; between air kerma and DAP; and between SNR and CNR (p<0.001, p<0.001). In conclusion, there was no significant difference between the entrance surface dose and absorbed dose even when the images were taken by changing the frame from 10 f/s to 15 f/s at the time of the coronary angiography. SNR and CNR increased at 15 f/s than at 10 f/s, but they were not statistically significant. Therefore, this study suggests that the concern of the patient and practitioner regarding image quality degradation, as well as the problem of X-ray exposure caused by imaging at 10 f/s and 15 f/s, may be reduced.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.13-24
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• 2019

Purpose: CT scan range is insufficient for various reasons in head and neck Tomotherapy^®. To solve that problem, Re-CT simulation is good because CT scan range affects accurate dose calculations, but there are problems such as increased exposure dose, inconvenience, and a change in treatment schedule. We would like to evaluate the minimum CT scan range required by changing the plan setup parameter of the existing CT scan range. Materials and methods: CT Simulator(Discovery CT590 RT, GE, USA) and In House Head & Neck Phantom are used, CT image was acquired by increasing the image range from 0.25cm to 3.0cm at the end of the target. The target and normal organs were registered in the Head & Neck Phantom and the treatment plan was designed using ACCURAY Precision^®. Prescription doses are Daily 2.2Gy, 27 Fxs, Total Dose 59.4Gy. Target is designed to 95%~107% of prescription dose and normal organ dose is designed according to SMC Protocol. Under the same treatment plan conditions, Treatment plans were designed by using five methods(Fixed-1cm, Fixed-2.5cm, Fixed-5cm, Dynamic-2.5cm Dynamic-5cm) and two pitches(0.43, 0.287). The accuracy of dose delivery for each treatment plan was analyzed by using EBT3 film and RIT(Complete Version 6.7, RIT, USA). Results: The accurate treatment plan that satisfying the prescribed dose of Target and the tolerance dose in normal organs(SMC Protocol) require scan range of at least 0.25cm for Fixed-1cm, 0.75cm for Fixed-2.5cm, 1cm for Dynamic-2.5cm, and 1.75cm for Fixed-5cm and Dynamic-5cm. As a result of AnalysisAnalysis by RIT. The accuracy of dose delivery was less than 3% error in the treatment plan that satisfied the SMC Protocol. Conclusion: In case of insufficient CT scan range in head and neck Tomotherapy^®, It was possible to make an accurate treatment plan by adjusting the FW among the setup parameter. If the parameter recommended by this author is applied according to CT scan range and is decide whether to re-CT or not, the efficiency of the task and the exposure dose of the patient are reduced.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.110-114
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• 2017

Because the arm can't be sutured due to fracture during a elbow CT scan, a CT scan is proceeded in a state of abdomen and L-spire are overlapped which beam hardening artifact is done many times, and it often lowers the quality of elbow CT images. So there are many difficulties in reading and due to increase in radiation dose from it, the number of patient's exposure keeps increasing. In this research, it plans to improve the quality of the images by avoiding overlap with abdomen, and increasing the number of photon overlapped with lung field which the line attenuation is relatively small. The way of experiment is based on patient's right elbow and place him as head first position, then place his elbow at L2-3 level in supine position, turn about 30 degrees to the left in non-control breathing and in supine position, and compared with full inspiration after overlapping with lung. After figuring out the average value and standard deviation data using Image J program 5 times each for 16, 128 channels, the evaluation is proceeded by measuring each of CNR, MSR are statistically analyzed using SPSS program. Therefore, through positioning and inspiration during elbow CT scan, the way of inspection minimized the exposure radiation dose, and seems to be meaningful in a way to improve the quality of the images.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.355-363
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• 2015

Advancement in the medical field provides an opportunity for the development of medical equipment and also enable accurate diagnosis for the inspection and the treatment of diseases. The aging of equipment due to the frequent operation produce uncertainty in the patient exposure dose, so a quality control was implemented by establishing a safety management system on a regular basis. The x-ray tube voltage (kVp), which is directly involved in the patient exposure dose and the life of the equipment, needs periodic performance for the quality control, but it has a limitation due to the time and the cost. In this study, we proposed a new method for measuring the kVp with ease by using the Y and Cu to solve the problem of the time and cost. We also evaluated the usefulness and the effectiveness of the new method and its accuracy through the kVp measurement. After securing the condition, the amount of the tube current and evaluating the usefulness and effectiveness of kVp measured using Y and Cu. The density range used was at 0.5-1.0, kVp was in the range of ${\pm}10%$, then, we recorded the change in concentration as % of Y and Cu. This experiment showed that when Cu and Y was at 75 kVp, concentration was the same, and when the kVp was changed to 65 ~ 85 %, a gradual increase in concentration to 85 ~ 110 % was noted.