• Journal of radiological science and technology
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• v.46 no.2
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• pp.99-106
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• 2023

The height of the table should be considered important during computed tomography (CT) examination, but according to previous studies, not all radiology technologists set the table at the patient's center at the examination, which affects the exposure dose and image quality received by the patient. Therefore, this study intends to study the image quality exposure dose according to the height of the table to realize the optimal image quality and dose during the brain CT scan. The head phantom images were acquired using Philips Brilliance iCT 256. When the image was acquired, the table height was adjusted to 815, 865, 915, 965, 1015, and 1030 mm, respectively, and each scan was performed 3 times for each height. For the exposure dose measurement, optically stimulated luminescence dosimeter (OSLD) was attached to the front, side, eye, and thyroid gland of the head phantom. In the signal to noise ratio (SNR) measurement result, The SNR values for each table height were all lower than 915 mm. As a result of exposure dose, the exposure dose on each area increased as the table height decreased. The height of the table has a close relationship with the patient's radiation exposure dose in the CT scan.

• Journal of radiological science and technology
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• v.46 no.4
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• pp.295-301
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• 2023

In addition to protocol adjustments during CT examinations, the height of the CT table can also affect image quality. Therefore, this study aimed to investigate the change in image quality depending on the height of the table in brain CT, which accounts for a large proportion of CT examinations, by measuring signal to contrast to noise ratio (CNR) and noise power spectrum (NPS) using the head phantom and evaluating them. The head phantom images were acquired using Philips Brilliance iCT 256. When the image was acquired, the table height was adjusted to 815, 865, 915, 965, 1015, and 1030 mm, respectively, and each scan was performed 3 times for each height. The CNR result showed the highest value at 965 mm, which is the height adjacent to the center of the head phantom. NPS showed the lowest NPS at 915 mm, the center of the head phantom in the low frequency region. From these results, it can be seen that the height of the table in CT examination is closely related to the image quality, and it can be seen the characteristics of image quality according to CT table through quantitative evaluation methods such as CNR and NPS.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.367-373
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• 2021

A quality assurance of computed tomography(CT) have done seven items that were water attenuation coefficient, noise, homogeneity, spatial resolution, contrast resolution, slice thickness, artifact using by standard phantom. But there is no quality assurance items and methods for CT simulator at domestic institutions yet. Therefore the study aimed to access the CT dose index(CTDI), table tilting, image distortion, laser accuracy, table movement accuracy and CT seven items for CT simulator quality assurance. The CTDI at the center of the head phantom was 0.81 for 80 kVp, 1.55 for 100 kVp, 2.50 for 120 mm, 0.22 for 80 kVp at the center of the body phantom, 0.469 for 100 kVp, and 0.81 for 120 kVp. The table tilting was within the tolerance range of ±1.0° or less. Image distortion had 1 mm distortion in the left and right images based on the center, and the laser accuracy was measured within ±2 mm tolerance. The purpose of this study is to improve the quality assurance items suitable for the current situation in Korea in order to protect the normal tissues during the radiation treatment process and manage the CT simulator that is implemented to find the location of the tumor more clearly. In order to improve the accuracy of the CT simulator when looking at the results, the error range of each item should be small. It is hoped that the quality assurance items of the CT simulator will be improved by suggesting the quality assurance direction of the CT simulator in this study, and the results of radiation therapy will also improve.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1367-1368
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• 2013

• Journal of the Korean Society of Radiology
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• v.11 no.6
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• pp.453-458
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• 2017

Computed Tomography (CT) provides information on the Diagnostic Reference Level Computed Tomography Dose Index (CTDI) and Dose Length Product (DLP) for accurate diagnosis of patients. However, it does not provide a dose change according to the table height for the diagnostic reference level provided by the CT equipment. The purpose of this study was to evaluate the image and dose according to the table height change using phantom (PMMA: Polymethyl Methacrylate) in order to find the optimal image and the minimum dose during computed tomography examination. When examining using a 32 cm PMMA phantom with the same thickness as the abdomen of an adult, there was little change in dose with table height. However, the noise evaluation of the image caused a high fluctuation of noise depending on the table height. and in the case of the 16 cm PMMA phantom, the change of the noise was small, but the dose change was about 30%. In conclusion, the location of the patient and the center of the detector are important during computed tomography (CT) examinations. In addition, table height setting is considered to be important for examinations with optimized image and minimum dose.

• The Journal of Korean Society for Radiation Therapy
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• v.17 no.1
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• pp.41-43
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• 2005

Purpose : Wish to present degree management process that is efficient confirm radiation treatment exclusive use CT simulator's Q.A item that become Q.A and Differentiation of diagnosis area that present Report of the AAPM Task Group No.66 using Q.A tool that produce itself and secure safe and correct CT-simulation process and equip convenience. Method and material : Manufacture CT simulator's Q.A tool on source and confirm virtue between isocenter of wall laser system, patient table, CT scanner's imaging plane that present in Report of the AAPM Task Group No.66 by daily publication unit. Result : Confirmed measured value from Report of the AAPM Task Group No.66 to confirmation of presenting degree management item in wall laser's ${\pm}2mm$, table's ${\pm}2mm$, imaging plane's ${\pm}2mm$ tolerance extent. Conclusion : There is unconfirmed item from CT-simulation process for therapy to CT Q.A protocol of existent diagnosis area, premising suitable degree management of radiation treatment exclusive use CT-simulator equipment confirming presenting Q.A item in Report of the AAPM Task Group No.66 safe and correct CT-simulation process guarantee can

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.677-684
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• 2020

Miscentering in the left and right X axis direction during CT examination affects dose and quality. When the CT Gantry Isocenter and the center of the examination objective are matched using the Lateral Sliding Table, the image quality is improved and the exposure dose is reduced. CTDI Head Phantom (Kimda, Korea) and dosimeter (Ray Safe, Sweden) were used to measure dose comparison CTDI (mGy) due to center deviation, and Water Phantom (HITACHI, Japan) was used to measure noise to see the difference in uniformity due to center deviation. Measurements of doses for dose comparison CTDI (mGy) with a deviation showed that doses were consistently reduced and exact dose was not projected until they were moved to 80 mm by 20 mm from the Isocenter. SD values were measured to see the difference in uniformity due to center deviation and the noise continued to increase until it was moved by 20 mm to 80 mm. The range of collimation has increased by the extent of deviating from the center and the range of exposure has increased. Using the Lateral Sliding Table, you can easily adjust the Isocenter, increase the quality of the image by adjusting the Isocenter in areaa such as the cardiac examination of the location away from the Isocenter, Extreme bone and Shoulder, and greatly reduce the collimation to the Isocenter, so it can be used to reduce unnecessary exposure dose.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.697-698
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• 2012

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.254-261
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• 2009

This study suggested that the table of CT-simulator and the laser alignment system using diagnostic CT scanner have an efficient method for improvement in alignment between the planned target center of traverse image with CT scanner. It was conducted on the daily QA when presented in the AAPM TG66 with correcting the laser alignment system using geometric trigonometric functions and investigated the effectiveness of correction methods as compared with those before and after correction. Before correction error was 3.82mm between the planned target center of image, the table longitudinal axis was twisted with 0.436o. The laser alignment system using geometric trigonometric functions in after correction was satisfied with tolerance limits of ${\pm}2mm$ when occurred about 0.7mm in errors between the planned target center. The table correction to satisfy the geometric accuracy is very inefficient over against the time and economic loss as well as technical limits in the case of application as only radiation therapy associated with CT-simulator with diagnostic CT scanner in use. But, the method which corrects the laser alignment system is economic and relatively simple with possibility of getting well geometric accuracy and we suppose that it is efficient method for applying in the clinic.

• Progress in Medical Physics
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• v.24 no.4
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• pp.237-242
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• 2013

In the intracranial regions, an accurate delineation of the target volume has been difficult with only the CT data due to poor soft tissue contrast of CT images. Therefore, the magnetic resonance images (MRI) for the delineation of the target volumes were widely used. To calculate dose distributions with MRI-based RTP, the electron density (ED) mapping concept from the diagnostic CT images and the pseudo CT concept from the MRI were introduced. In this study, the look up table (LUT) from the fifteen patients' diagnostic brain MRI images was created to verify the feasibility of MRI-based RTP. The dose distributions from the MRI-based calculations were compared to the original CT-based calculation. One MRI set has ED information from LUT (lMRI). Another set was generated with voxel values assigned with a homogeneous density of water (wMRI). A simple plan with a single anterior 6MV one portal was applied to the CT, lMRI, and wMRI. Depending on the patient's target geometry for the 3D conformal plan, 6MV photon beams and from two to five gantry portals were used. The differences of the dose distribution and DVH between the lMRI based and CT-based plan were smaller than the wMRI-based plan. The dose difference of wMRI vs. lMRI was measured as 91 cGy vs. 57 cGy at maximum dose, 74 cGt vs. 42 cGy at mean dose, and 94 cGy vs. 53 at minimum dose. The differences of maximum dose, minimum dose, and mean dose of the wMRI-based plan were lower than the lMRI-based plan, because the air cavity was not calculated in the wMRI-based plan. These results prove the feasibility of the lMRI-based planning for brain tumor radiation therapy.