• Journal of the Korean Society of Radiology
• /
• v.8 no.4
• /
• pp.203-210
• /
• 2014

Chest radiography has been typically performed at SID of 180 cm. Image quality and patient dose were investigated between 180 cm and 340 cm by 20 cm intervals at 120 kVp and 320 mAs with the AEC. VGA was performed for qualitative assessment and SNR was analysed for quantitative assessment on the image of the chest phantom. Patients dose was measured by ESAK and PCXMC was used for effective dose. As a result, when using the standard of SID of 180 cm which is typically used in the clinical practice, in the case of ESAK, 240 cm, 280 cm, and 320 cm were 8.7%, 11.47%, and 13.56% respectively therefore significant reduction was confirmed. In the case of effective dose, 2.89%, 4.67%, and 6.41% in the body and 5.08%, 6.09%, and 9.6% in lung were reduced. In the case of SNR, 9.04%, 8.24%, and 11.46% were respectively decreased especially, by 8.03% between SID of 260 cm and 300 cm, but SNR was 5.24 up to 340 cm. There were no significant differences in VGA thus the image is valuable in diagnosis. It is predicted that increasing SID up to 300 cm in digital chest radiography can reduce patient dose without decreasing image quality.

• Journal of the Korean Society of Radiology
• /
• v.12 no.7
• /
• pp.845-852
• /
• 2018

This study aimed to investigate the difference of X-ray exposure by comparing and analyzing absorbed dose according to changes in the number of frames in coronary angiography, also depending whether the zoom mode is FOV enlargement or Zoom Live. Moreover, for appropriate frame selection measures for examination, including the effect of frame change on the image quality, were sought by measuring the noise strength expressed by the standard deviation (SD), the signal to noise ratio (SNR) and contrast to noise ratio (CNR). The study was conducted with an anthropomorphic phantom on an angio-system. The linear relationship between the frame rate and the radiation dose was evident. On the contrary, the indices of image quality (SD, SNR, and CNR) were almost constant irrespective of the number of frames. The difference depending on the zoom mode was not statistically significant for DAP, air kerma, and SD (p > 0.05). However, SNR and CNR were statistically different between FOV enlargement and Zoom Live. In conclusion, since the image quality was not degraded significantly with the decreasing frame rate from 30, 15, to 7.5 f/s and the radiation dose evidently decreases in almost exactly linear proportion to the decreasing frame rate, the number of frames per second needs to be maintained as low as reasonably achievable. As for the dependence on the zooming mode, the Live Zoom mode showed statistically significant improvement in the image quality indices of SNR and CNR and it justifies active use of the Live Zoom mode which enables real-time image enlargment without additional radiation dose.

• Journal of Radiation Protection and Research
• /
• v.47 no.3
• /
• pp.158-166
• /
• 2022

Background: The effects of radiation on the health of radiation workers who are constantly susceptible to occupational exposure must be assessed based on an accurate and reliable reconstruction of organ-absorbed doses that can be calculated using personal dosimeter readings measured as H_p(10) and dose conversion coefficients. However, the data used in the dose reconstruction contain significant biases arising from the lack of reality and could result in an inaccurate measure of organ-absorbed doses. Therefore, this study quantified the biases involved in organ dose reconstruction and calculated the bias-corrected H_p(10)-to-organ-absorbed dose coefficients for the use in epidemiological studies of Korean radiation workers. Materials and Methods: Two major biases were considered: (a) the bias in H_p(10) arising from the difference between the dosimeter calibration geometry and the actual exposure geometry, and (b) the bias in air kerma-to-H_p(10) conversion coefficients resulting from geometric differences between the human body and slab phantom. The biases were quantified by implementing personal dosimeters on the slab and human phantoms coupled with a Monte Carlo method and considered to calculate the bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients. Results and Discussion: The bias in H_p(10) was significant for large incident angles and low energies (e.g., 0.32 for right lateral at 218 keV), whereas the bias in dose coefficients was significant for the posteroanterior (PA) geometry only (e.g., 0.79 at 218 keV). The bias-corrected H_p(10)-to-organ-absorbed dose conversion coefficients derived in this study were up to 3.09- fold greater than those from the International Commission on Radiological Protection publications without considering the biases. Conclusion: The obtained results will aid future studies in assessing the health effects of occupational exposure of Korean radiation workers. The bias-corrected dose coefficients of this study can be used to calculate organ doses for Korean radiation workers based on personal dose records.

• Journal of the Korean Society of Radiology
• /
• v.17 no.4
• /
• pp.589-595
• /
• 2023

If complete coronary artery occlusion occurs due to severer coronary spasm, malignant arrhythmias can lead to death. Therefore, early screening for coronary artery spasm angina is essential. Among the test methods, the drug injection test through coronary angiography is generally performed. Therefore, the purpose of this study was to evaluate the advantages of ergonovine drug test for vasospasitc angina examination during coronary angiography, such as the relationship between the procedure time, contrast medium usage, and radiation exposure effects of coronary angiography. Follow-up data of 142 patients who underwent coronary angiography and variant angina examination from september 2021 to february 2023 were used. As a result of analyzing contrast usage dose and dose area product and air kerma dose and number of imaging series and procedure time, variant angina examination was statistically significantly higher than coronary angiography. (p<0.001) In conclusion, variant angina examination other than coronary artery angiography are radiologically negative. Therefore, we think it is better to avoid excessive inspection. Nevertheless, in the case of the provocation test, the longer the examination time, the higher the fluoroscopy time and the amount of contrast medium used, so it is better to conduct the test as quickly as possible or shorten it.

• Journal of the Korean Society of Radiology
• /
• v.17 no.4
• /
• pp.551-556
• /
• 2023

Angiography equipment is used to evaluate and treat coronary artery disease. As a common feature of equipment, radiation is used, and function development for dose reduction is being carried out by each company. Therefore, the difference depending on whether DCR installed in angiography equipment is used is analyzed from a radiological point of view to prove the effect. Among 431 patients who underwent coronary artery intervention from March 2021 to February 2023, 250 patients with retrospective data were selected. And than among the 250 subjects obtained, 91 patients used the cardiovascular roadmap function during single-vessel intervention, and 159 patients did not use the roadmap. When DCR was used, total dose area product (34.57 uGy/m² : 69.15 uGy/m²), total air kerma dose (688.47 mGy : 1640.4 mGy), fluoroscopy dose (23.87 uGy/m² : 49.91 uGy/m²) and fluoroscopy time (723.55 s : 366.03 s), total number of images (17 : 26) showed lower values and were statistically significant than those not used. The use of DCR function in single vessel coronary intervention is thought to be radiologically safer as single vessel coronary intervention using dynamic cardiovascular DCR showed lower perspective time and perspective dose than procedures performed without the DCR.

• Korean Journal of Radiology
• /
• v.23 no.5
• /
• pp.548-554
• /
• 2022

Objective: To evaluate the safety and feasibility of prostatic artery embolization (PAE) via transradial access (TRA) compared with transfemoral access (TFA). Materials and Methods: This retrospective study included 53 consecutive men with lower urinary tract symptoms (LUTS) who underwent PAE between September 2018 and September 2021. Thirty-one patients (mean age ± standard deviation: 70.6 ± 8.4 years) were treated with TFA, including 14 patients treated before adopting TRA. Since December 2019, TRA has also been attempted with the procedure's selection criteria of patent carpal circulation and a height ≤ 172 cm, with 22 patients treated via TRA (69.1 ± 9.6 years). Parameters of technical success (defined as successful bilateral embolization), clinical success (defined as LUTS improvement), procedural time, radiation dose, and adverse events were compared between the two groups using the Fisher's exact test, independent sample t test, Wilcoxon signed-rank test, or Mann-Whitney test. Results: All patients received at least one-side PAE. Technical success of PAE was achieved in most patients (TRA, 21/22; TFA, 30/31; p > 0.999). No technical problem-related conversion from TRA to TFA occurred. The clinical success rate was 85% (11/13) in patients with TRA, and 89% (16/18) in patients with TFA for follow-up > 2 weeks post-PAE (median, 3 months) (p > 0.999). The median procedure time was similar in both groups (TRA, 81 minutes vs. TFA, 94 minutes; p = 0.570). No significant dose differences were found between the TRA and TFA groups in the dose-area product (median Gycm², 95 [range, 44-255] for TRA and 84 [34-255] for TFA; p = 0.678) or cumulative air kerma (median mGy, 609 [236-1584] for TRA and 634 [217-1594] for TFA; p = 0.551). No major adverse events occurred in either of the groups. Conclusion: PAE via TRA is a safe and feasible method comparable to conventional TFA. It can be safely implemented by selecting patients with patent carpal circulation and adequate height.

• Korean Journal of Radiology
• /
• v.23 no.2
• /
• pp.256-263
• /
• 2022

Objective: This study aimed to evaluate the image quality and dose reduction of low-dose three-dimensional (3D) rotational angiography (RA) for evaluating intracranial aneurysms. Materials and Methods: We retrospectively evaluated the clinical data and 3D RA datasets obtained from 146 prospectively registered patients (male:female, 46:100; median age, 58 years; range, 19-81 years). The subjective image quality of 79 examinations obtained from a conventional method and 67 examinations obtained from a low-dose (5-seconds and 0.10-μGy/frame) method was assessed by two neurointerventionists using a 3-point scale for four evaluation criteria. The total image quality score was then obtained as the average of the four scores. The image quality scores were compared between the two methods using a noninferiority statistical testing, with a margin of -0.2 (i.e., score of low-dose group - score of conventional group). For the evaluation of dose reduction, dose-area product (DAP) and air kerma (AK) were analyzed and compared between the two groups. Results: The mean total image quality score ± standard deviation of the 3D RA was 2.97 ± 0.17 by reader 1 and 2.95 ± 0.20 by reader 2 for conventional group and 2.92 ± 0.30 and 2.95 ± 0.22, respectively, for low-dose group. The image quality of the 3D RA in the low-dose group was not inferior to that of the conventional group according to the total image quality score as well as individual scores for the four criteria in both readers. The mean DAP and AK per rotation were 5.87 Gy-cm² and 0.56 Gy, respectively, in the conventional group, and 1.32 Gy-cm² (p < 0.001) and 0.17 Gy (p < 0.001), respectively, in the low-dose group. Conclusion: Low-dose 3D RA was not inferior in image quality and reduced the radiation dose by 70%-77% compared to the conventional 3D RA in evaluating intracranial aneurysms.

• Progress in Medical Physics
• /
• v.22 no.4
• /
• pp.163-171
• /
• 2011

The purpose of this study was to investigate the effect of various technical parameters for the dose optimization in pediatric chest radiological examinations by evaluating effective dose and effective detective quantum efficiency (eDQE) including the scatter radiation from the object, the blur caused by the focal spot, geometric magnification and detector characteristics. For the tube voltages ranging from 40 to 90 kVp in 10 kVp increments at the FDD of 100, 110, 120, 150, 180 cm, the eDQE was evaluated at the same effective dose. The results showed that the eDQE was largest at 60 kVp when compares the eDQE at different tube voltage. Especially, the eDQE was considerably higher without the use of an anti-scatter grid on equivalent effective dose. This indicates that the reducing the scatter radiation did not compensate for the loss of absorbed effective photons in the grid. When the grid is not used the eDQE increased with increasing FDD because of the greater effective modulation transfer function (eMTF). However, most of major hospitals in Korea employed a short FDD of 100 cm with an anti-scatter grid for the chest radiological examination of a 15 month old infant. As a result, the entrance surface air kerma (ESAK) values for the hospitals of this survey exceeded the Korean DRL (diagnostic reference level) of $100{\mu}Gy$. Therefore, appropriate technical parameters should be established to perform pediatric chest examinations on children of different ages. The results of this study may serve as a baseline to establish detailed reference level of pediatric dose for different ages.

• Korean Journal of Digital Imaging in Medicine
• /
• v.14 no.2
• /
• pp.23-31
• /
• 2012

There are AEC mode and fix mode to exposure when the whole spine antero-posterior radiography is done by using DR equipment. This study compared the utility of fix mode to AEC mode, by evaluating organ dose and effective dose and by examining the quality of radiographic image. GE DEFINIUM 8000 and ART-200X Rando Phantom manufactured by Flukebiometical were used for this study. The Rando phantom was set in front of wall detector of X-rays equipment. AEC mode was set at 80kVp and Fix mode was set at 80kVp, 25mAs, 32mAs, 40mAs, and 50mAs. Whole spine AP image were aquired by combining C, T-L and L-S spine images obtained through 3 exposures. When obtaining C, T-L and L-S spine images, were checked for Air kerma (mGy) value calculated by UNFORS Xi meter attached at the phantom surface of center of radiation field. The effective and organ doses were compared by PCXMC program (PC-Based Monte Carlo Program). The quality of obtained radiographic image was evaluated visually by 3 radiologists using resolution chart. When the effective doses was calculated based on tissue weighting factor of ICRP-103, 1.278mSv was measured by AEC mode, and Fix mode measured 0.405mSv at 25mAs, 0.518mSv at 32mAs, 0.649mSv at 40mAs, and 0.810mSv at 50mAS. In addition, the organ dose measured with esposure at 25mAs by Fix mode was almost equivalent to the organ dose by AEC mode, at the esophagus, thyroid, oral mucosa, salivaly glands located at the cervical spine part, while the organ dose by Fix mode was in general lower than the organ dose by AEC mode at the other organs. When Fix mode at 32mAs, 40mAs, and 50mAs was compared to AEC mode for organ dose in 26 organs, AEC mode had higher measurement in 21 organs but not for than brain, trachea, thyroid, oral mucosa, and salivaly glands which are located at the cervical spine part. The image quality evaluated by resolution test chart was much higher with AEC mode than the quality with Fix mode at all exposure conditions. However, while the image quality of cervical spine exposured at 50mAs by Fix mode was lower than the quality of AEC mode, thoraco-lumbar spine and lumbo-sacral spine were calculated and the quality was similar to AEC mode. Scoliosis occurs mainly at thoraco-lumbar and lumbo-sacral spine, not at cervical spine. Compared to AEC mode, Using the appropriate protocol (80kVp, 50mAs) of fix mode for whole spine AP radiography was thought to be useful because the image quality of the thoraco-lumar and lumbo-sacral spine was similar on AEC mode, Also organ and effective doses can be decreased with Fix mode. Therefore, It is considered that fix mode can be used properly with AEC mode for whole spine AP radiography when considering patient's body posture.

• Progress in Medical Physics
• /
• v.24 no.4
• /
• pp.315-322
• /
• 2013

The aim of this work is to verify the self-quality assurances in medical institutions in Korea through the external audits by the group of experts and have a mutual discussion of the systematic problems. In order to validate the external audits 30 of 80 medical institutions across the nation were picked out considering the regional distribution and the final 25 institutions applied voluntarily to take part in this work. The basic rules were setup that any information of the participants be kept secrete and the measurements be performed with the dosimetry system already verified through intercomparision. The outputs for 2 or more photon beams, the accuracy of gantry rotation and collimator rotation and the poistional accuracy of MLC movement were measured. The findings for the output measurement showed the differences of -0.8%~4.5%, -0.79%~3.01%, and -0.7%~0.07% with respect to that of the verified dosimetry system for the 6MV, 10MV, and 15MV, respectively. For the reference absorbed dose 8 (16%) of 50 photon beams in 25 medical institutions differed 2.0% or greater from the reference value. The coincidences of Field size with x-ray beam and radiation isocenters of Gantry roration and collimator rotation gave the results of within ${\pm}2$ mm for every institute except 2 institutions. The positional accuracy of MLC movement agreed to within ${\pm}1$ mm for every institute. For the beam qualities of 6 MV photon beams kQ values showed the distribution within 0.4% between maximum and minimum. For the protocols 21 institutions (84%) used absorbed dose to water based protocol while 4 insitutions (16%) used air kerma based one. 22 institutions employed the SSD technique while 3 institutions did the SAD one. External audit plays an important role in discovering the systematic problems of self-performing Quality Assurances and having in depth discussion for mutual complementation. Training experts of international level as well as national support system are required so that both the group of experts of medical physicists and government laboratory could perform together periodical and constant external audits.