• Journal of radiological science and technology
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• v.31 no.2
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• pp.171-175
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• 2008

The aim of this study is to assess the dose reduction of eye lens and availability of bismuth garments resulting from the use of radioprotective bismuth garments to shield the eyes of patients undergoing head CT. Rando phantom and TLDs were used to determine the amount of dose reduction by bismuth shielding of the eye in the following simulated CT scans : (a) scanning of the head including orbits, (b) scanning of the whole head, and (c) $20^{\circ}$ angled scanning of the head excluding orbits. The average dose reduction of eye lens was 43.2%, 36.0% and 1.4% for the three CT scans listed above. Significant reduction in the eye lens dose was achieved by using superficial orbital bismuth shielding during head CT scans. However, bismuth shields should not be used for the patients when their eyes are excluded from the primarily exposed region.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.742-749
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• 2009

The use of cone-beam computed tomography(CBCT) has been proposed for guiding the delivery of radiation therapy. A kilovoltage imaging system capable of radiography, fluoroscopy, and cone-beam computed tomography(CT) has been integrated with a medical linear accelerator. A standard clinical linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) with an on-board electronic portal imager can be used to treat palliative patient and verify the patient's position prior to treatment. On-board CBCT images are used to generate patient geometric models to assist patient setup. The image data can also, potentially, be used for dose reconstruction in combination with the fluence maps from treatment plan. In this study, the accuracy of Hounsfield Units of CBCT images as well as the accuracy of dose calculations based on CBCT images of a phantom and compared the results with those of using CT simulator images. Phantom and patient studies were carried out to evaluate the achievable accuracy in using CBCT and CT stimulator for dose calculation. Relative electron density as a function of HU was obtained for both planning CT stimulator and CBCT using a Catphan-600 (The Phantom Laboratory, USA) calibration phantom. A clinical treatment planning system was employed for CT stimulator and CBCT based dose calculations and subsequent comparisons. The dosimetric consequence as the result of HU variation in CBCT was evaluated by comparing MU/cCy. The differences were about 2.7% (3-4MU/100cGy) in phantom and 2.5% (1-3MU/100cGy) in patients. The difference in HU values in Catphan was small. However, the magnitude of scatter and artifacts in CBCT images are affected by limitation of detector's FOV and patient's involuntary motions. CBCT images included scatters and artifacts due to In addition to guide the patient setup process, CBCT data acquired prior to the treatment be used to recalculate or verify the treatment plan based on the patient anatomy of the treatment area. And the CBCT has potential to become a very useful tool for on-line ART.)

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.1159-1166
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• 2009

The use of cone-beam computed tomography(CBCT) has been proposed for guiding the delivery of radiation therapy. A kilovoltage imaging system capable of radiography, fluoroscopy, and cone-beam computed tomography(CT) has been integrated with a medical linear accelerator. A standard clinical linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) with an on-board electronic portal imager can be used to treat palliative patient and verify the patient's position prior to treatment. On-board CBCT images are used to generate patient geometric models to assist patient setup. The image data can also, potentially, be used for dose reconstruction in combination with the fluence maps from treatment plan. In this study, the accuracy of Hounsfield Units of CBCT images as well as the accuracy of dose calculations based on CBCT images of a phantom and compared the results with those of using CT simulator images. Phantom and patient studies were carried out to evaluate the achievable accuracy in using CBCT and CT stimulator for dose calculation. Relative electron density as a function of HU was obtained for both planning CT stimulator and CBCT using a Catphan-600 (The Phantom Laboratory, USA) calibration phantom. A clinical treatment planning system was employed for CT stimulator and CBCT based dose calculations and subsequent comparisons. The dosimetric consequence as the result of HU variation in CBCT was evaluated by comparing MU/cCy. The differences were about 2.7% (3-4MU/100cGy) in phantom and 2.5% (1-3MU/100cGy) in patients. The difference in HU values in Catphan was small. However, the magnitude of scatter and artifacts in CBCT images are affected by limitation of detector's FOV and patient's involuntary motions. CBCT images included scatters and artifacts due to In addition to guide the patient setup process, CBCT data acquired prior to the treatment be used to recalculate or verify the treatment plan based on the patient anatomy of the treatment area. And the CBCT has potential to become a very useful tool for on-line ART.)

• Journal of the Korean Society of Radiology
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• v.16 no.1
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• pp.45-51
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• 2022

This study compared DLP values along with phantom entrance surface doses and the image quality of chest CT scans made using a Care Dose 4D+Care kV System, scans that are made using only the Care Dose 4D function, and scans that are made with changes made by applying 80 kVp, 100 kVp, 120 kVp, and 140 kVp to the Care Dose 4D and tube voltage to search for methods to maintain the highest image quality with minimal patient doses. It was shown that DLP values decreased 6.727% when scans were taken with Chest Care Dose 4D + Care kV semi 100 and 6.481% when scans were taken with Chest Care Dose 4D + Care kV. With Chest Non as a standard, skin surface doses decreased 16.519% when scans were taken with Chest Care Dose 4D + Care kV semi 100 and 15.705% when scans were taken with Chest Care Dose 4D + Care kV. With comparisons of image quality, when comparisons were made with Chest Non, comparisons made of SNR values and CNR values in all scanning conditions including Care Dose 4D + Care kV showed that there were no significant differences at P>0.05. Imaging using Chest Care Dose 4D + Care kV in chest CT showed that exposure doses decreased similarly to result values gained from the best conditions through manual adjustments of kV and mAS, and there were no significant differences in image SNR and CNR. If the Chest Care Dose 4D + Care kV function is used, image quality is maintained and patient exposure to radiation can be reduced.

• Journal of the Korean Society of Radiology
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• v.12 no.1
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• pp.47-52
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• 2018

Brain perfusion CT scanning is often employed usefully in clinical conditions as it accurately and promptly provides information about the perfusion state of patients having acute ischemic stroke with a lot of time constraints and allows them to receive proper treatment. Despite those strengths of it, it also has a serious weakness that Lens may be exposed to a lot of dose of radiation in it. In this study, as a way to reduce the dose of radiation to Lens in brain perfusion CT scanning, this researcher conducted an experiment with Bismuth shielding and change of patients' position. TLD (TLD-100) was placed on both lens using the phantom (PBU-50), and then, in total 4 positions, parallel to IOML, parallel to IOML (Bismuth shielding), parallel to SOML, and parallel to SOML (Bismuth shielding), brain perfusion scanning was done 5 times for each position, and dose to Lens were measured. Also, to examine how the picture quality changed in different positions, 4 areas of interest were designated in 4 spots, and then, CT number and noise changes were measured and compared. According to the results of conducting one-way ANOVA on the doses measured, as the significance probability was found to be 0.000, so there was difference found in the doses of radiation to crystalline lenses. According to the results of Duncan's post-hoc test, with the scanning of being parallel to IOML as the reference, the reduction of 89.16% and 89.66% was observed in the scanning of being parallel to SOML and that of being parallel to SOML (Bismuth shielding) respectively, so the doses to Lens reduced significantly. Next, in the scanning of being parallel to IOML (Bismuth shielding), the reduction of 37.12% was found. According to the results, reduction in the doses of radiation was found the most significantly both in the scanning of being parallel to SOML and that of being parallel to SOML (Bismuth shielding). With the limit of the equivalent dose to Lens as the reference, this researcher conducted comparison with the dose to occupational exposure and dose to Public exposure in the scanning of being parallel to IOML and found 39.47% and 394.73% respectively; however in the scanning of being parallel to SOML (Bismuth shielding), considerable reduction was found as 4.08% and 40.8% respectively. According to the results of evaluation on picture quality, every image was found to meet the evaluative standards of phantom scanning in terms of the measurement of CT numbers and noise. In conclusion, it would be the most useful way to reduce the dose of radiation to Lens to use shields in brain perfusion CT scanning and adjust patients' position so that their lens will not be in the field of radiation.

• Journal of the Korea Convergence Society
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• v.9 no.12
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• pp.107-113
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• 2018

The purpose of this study was to evaluate the dose and image quality according to the rotation of the X-axis direction in the abdominal CT scan, and to find ways to reduce the exposure dose. The phantom was scanned by rotating in the X-axis direction at 0, 5, 10, and 15 degrees, respectively. The CTDIvol value, HU, noise, and signal-to-noise ratio were measured at each rotation. ANOVA analysis was performed using the SPSSWIN (ver 19.0) program. The radiation exposure dose was 5.44mGy, 5.70mGy, 5.98mGy and 6.38mGy at 0, 5, 10 and 15 degrees, respectively. HU, noise, and signal-to-noise ratio were not statistically significant. In the CT scan, if the patient is located in the isocenter of the gantry aperture and there is no rotation in the X-axis direction, the exposure dose is reduced.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.1
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• pp.15-24
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• 2013

Purpose: In Asan Medical Center, Two parallel opposite beams are employed for total body irradiation. Patients are required to be in supine position where two arms are attached to mid axillary line. Normally, physical compensators are required to compensate the large dose difference for different parts of body due to the different thicknesses compared to the umbilicus separation. There was the maximum dose difference up to 30% in lung and chest wall compared to the prescription dose. In order to resolve the dose discrepancy occurring on different body regions, the feasibility of using Fieid-in-Field Technique is investigated in this study. Materials and Methods: CT scan was performed to The RANDO Phantom with fabricated two arms and sent to Eclipse treatment planning system (version 10.0, Varian, USA). Conventional plan with physical lead compensator and new plan using Field-in-Field Technique were established on TPS. AAA (Anisotropic Analytical Algorithm) dose calculation algorithm was employed for two parallel opposite beams attenuation. Results: The dose difference between two methods was compared with the prescription dose. The dose distribution of chest and anterior chest wall uncovered by patient arms was 114~124% for physical lead compensator while Field-in-Field Technique gave 106~107% of the dose distribution. In-vivo dosimetry result using TLD showed that the dose distribution to the same region was 110~117% for conventional physical compensator and 104~107% for Field-in-Field Technique. Conclusion: In this study, the feasibility of using FIF technique has been investigated with fabricated arms attached Rando phantom. The dose difference was up to 17% due to the attached arms. It is shown that the dose homogeneity is within ${\pm}10%$ with the CT based 3-dimensional 4 step FIF technique. The in-vivo dosimetry result using TLD was showed that 95~107% dose distribution compared to prescription dose. It is considered that CT based 3-dimensional Field-in-Field Technique for the total body irradiation gives much homogeneous dose distribution for different body parts than the conventional physical compensator method and might be useful to evaluate the dose on each part of patient body.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.131-134
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• 2010

Purpose: TOMO therapy treatment for a relatively long run Beam time and temperature-sensitive detector, such as CT clinics in optimal temperature ($20~21^{\circ}$) to maintain a constant temperature in addition to its own Chamber Cooling system is activating. TOMO This clinic has been reduced in the patients' body temperature to keep the sheets and covers over the treated area. Therefore, these materials for any changes in the organization gives the dose were analyzed. Materials and Methods: To compare changes in the organization Dose Phantom cheese (Cheese Phantom) were used, CT-simulation taking the center point of the cheese phantom PTV (Planning Target Volume, treatment planning target volume) by setting Daily dose 200 cGy, 3 meetings planned treatment. PTV, PTV +7 cm, PTV +14 cm, the total count points on the phantom using the Ion chamber cover without any substance to measure the dose, and one of the most commonly used treatment, including the frequently used four kinds of bedding materials (febric 0.8 mm, gown 1.4 mm, rug, 3.3 mm, blanket 13.7 mm) and covered with a phantom and the dose measured at the same location were analyzed 3 times each. Results: PTV, PTV +7 cm, PTV +14 cm from the point of any substance measured in the state are covered with four kinds of materials (fabric, gown, rug, blanket) was measured in the covered states and compares their results, PTV respectively -0.17%, -0.44%, -0.53% and -0.9% change, PTV +7 cm, respectively -0.04%, +0.07%, +0.06%, +0.07%, were changed, PTV +14 cm, respectively 0%, -0.06%, -0.02%, +0.6%, respectively. Conclusion: These results TOMO treatment to patients to maintain their body mass by using PTV thickness of the material decreased in proportion to. PTV +7 cm, but showed slight changes in the point, PTV +14 cm at the point of the dose was increased a little. Sejijeom all the difference in treatment tolerance ${\pm}3%$ range, this is confirmed in the coming treatment will not affect the larger should be considered.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.77-84
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• 2017

Purpose: To evaluate the image quality improvement and dosimetric effects on virtual monochromatic images of a Dual Source-Dual Energy CT(DS-DECT) for radiotherapy planning. Materials and Methods: Dual energy(80/Sn 140 kVp) and single energy(120 kVp) scans were obtained with dual source CT scanner. Virtual monochromatic images were reconstructed at 40-140 keV for the catphan phantom study. The solid water-equivalent phantom for dosimetry performs an analytical calculation, which is implemented in TPS, of a 10 MV, $10{\times}10cm^2$ photon beam incident into the solid phantom with the existence of stainless steel. The dose profiles along the central axis at depths were discussed. The dosimetric consequences in computed treatment plans were evaluated based on polychromatic images at 120 kVp. Results: The magnitude of differences was large at lower monochromatic energy levels. The measurements at over 70 keV shows stable HU for polystyrene, acrylic. For CT to ED conversion curve, the shape of the curve at 120 kVp was close to that at 80 keV. 105 keV virtual monochromatic images were more successful than other energies at reducing streak artifacts, which some residual artifacts remained in the corrected image. The dose-calculation variations in radiotherapy treatment planning do not exceed ${\pm}0.7%$. Conclusion: Radiation doses with dual energy CT imaging can be lower than those with single energy CT imaging. The virtual monochromatic images were useful for the revision of CT number, which can be improved for target coverage and electron densities distribution.

• Progress in Medical Physics
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• v.24 no.1
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• pp.35-40
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• 2013

Recently, the uses of Multi-Detector Computed Tomography (MDCT) for radiation treatment simulation and planning which is used for intensity modulated radiation therapy with high technique are increasing. Because of the increasing uses of MDCT, additional doses are also increasing. The objective of this study is to evaluate the absorbed dose of body and skin undergoing in MDCT scans. In this study, the exposed dose at the surface and the center of the cylindrical water phantom was measured using an pencil ionization chamber, 30 cc ionization chamber and TL Powder. The results of MDCT were 31.84 mGy, 33.58 mGy and 32.73 mGy respectively. The absorbed dose at the surface showed that the TL reading value was 33.92 mGy from MDCT. These results showed that the surface dose was about 3.5% from the MDCT exposure higher than a dose which is located at the center of the phantom. These results mean that the total exposed dose undergoing MDCT 4 times (diagnostic, radiation therapy planning, follow-up et al.), is about 14 cGy, and have to be considered significantly to reduce the exposed dose from CT scan.