• The Journal of Korean Society for Radiation Therapy
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• v.21 no.2
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• pp.89-95
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• 2009

Purpose: The purpose is to evaluate efficiency of the CT simulator QA phantom manufactured for daily QA. Materials and Methods: We made holes ($1{\times}100{\times}1\;mm$) to verify accuracy between image and real measurement in polystyrene phantom and made 1 mm holes to verify table movement accuracy at superior and inferior 100 mm to the center of the phantom and inserted radiopacity material. To evaluate laser alignment, we made cross mark on the right and left side at phantom and to evaluate CT number accuracy we made 3 cylindrical holes and inserted equivalence material of bone, water, air in them. After CT scanning the phantom, We evaluated accuracy between image and real measurement, accuracy of table movement, laser, and CT number using exposed image. Results: It was measured that the accuracy between image and real measurement was ${\pm}0.3\;mm$, table movement accuracy was ${\pm}0.3\;mm$, laser accuracy was ${\pm}0.5\;mm$ from 7th January to 7th March in 2008 as within the reference point ${\pm}1\;mm$. In the CT number accuracy of bone was ${\pm}10\;HU$, air was ${\pm}5\;HU$, water was ${\pm}5\;HU$ as within the reference point is ${\pm}10\;HU$. Conclusion: We was able to perform CT simulator QA and laser equipment QA more conveniently and fast using manufactured phantom at the same time. We will be able to make more accurate treatment plan that added to QA procedures using images at previous daily QA.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.301-306
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• 2021

The use of tin filters as a way to reduce the medical radiation in computed tomography (CT). However, due to the changed X-ray spectrum with the use of tin filters, disease diagnosis could be affected because it appears as images of different impressions from previous images. Therefore, this study evaluates the changes in images when using tin filter and high pitch in chest low-dose CT. In this study, images were acquired in groups of three for comparison. Group 1 did not apply to tin filter, and used the existing pitch 0.8. Group 2 used a tin filter, pitch 0.8, Group 3 used a tin filter, and pitch 2.5. To compare the image quality, the natural image quality evaluator (NIQE) and the blind/referenceless image quality evaluator (BRISQUE) were used among the blind quality evaluation factors depended on a no-reference basis. As a result, the NIQE values were low in the order of Group 1, Group 3, and Group 2. BRISQUE values were low in the order of Group 3, Group 2 and Group 1. This study confirms the superiority of images of tin filter and high pitch techniques in chest low-dose CT, which is considered to be a fundamental study for acquiring accurate images of patients with difficult breathing control.

• The Journal of Korean Society for Radiation Therapy
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• v.21 no.2
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• pp.83-88
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• 2009

Purpose: Cone beam computed tomography (CBCT) using an on board imager (OBI) can check the movement and setup error in patient position and target volume by comparing with the image of computer simulation treatment in real.time during patient treatment. Thus, this study purposed to check the change and movement of patient position and target volume using CBCT in IMRT and calculate difference from the treatment plan, and then to correct the position using an automated match system and to test the accuracy of position correction using an electronic portal imaging device (EPID) and examine the usefulness of CBCT in IMRT and the accuracy of the automatic match system. Materials and Methods: The subjects of this study were 3 head and neck patients and 1 pelvis patient sampled from IMRT patients treated in our hospital. In order to investigate the movement of treatment position and resultant displacement of irradiated volume, we took CBCT using OBI mounted on the linear accelerator. Before each IMRT treatment, we took CBCT and checked difference from the treatment plan by coordinate by comparing it with the image of CT simulation. Then, we made correction through the automatic match system of 3D/3D match to match the treatment plan, and verified and evaluated using electronic portal imaging device. Results: When CBCT was compared with the image of CT simulation before treatment, the average difference by coordinate in the head and neck was 0.99 mm vertically, 1.14 mm longitudinally, 4.91 mm laterally, and 1.07o in the rotational direction, showing somewhat insignificant differences by part. In testing after correction, when the image from the electronic portal imaging device was compared with DRR image, it was found that correction had been made accurately with error less than 0.5 mm. Conclusion: By comparing a CBCT image before treatment with a 3D image reconstructed into a volume instead of a 2D image for the patient's setup error and change in the position of the organs and the target, we could measure and correct the change of position and target volume and treat more accurately, and could calculate and compare the errors. The results of this study show that CBCT was useful to deliver accurate treatment according to the treatment plan and to increase the reproducibility of repeated treatment, and satisfactory results were obtained. Accuracy enhanced through CBCT is highly required in IMRT, in which the shape of the target volume is complex and the change of dose distribution is radical. In addition, further research is required on the criteria for match focus by treatment site and treatment purpose.

• Progress in Medical Physics
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• v.15 no.1
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• pp.23-29
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• 2004

The relationship between the dose calculated with a radiotherapy treatment planning system (RTPS) and CT number verses the relative electron density curve was investigated for various CT voltages and beam qualifies. We obtained the relationship between the CT numbers and electron densities of the tissue equivalent materials for various CT voltages and beam qualifies. At lower CT voltages, the higher density materials, like cortical bone, showed larger CT numbers and the soft tissues showed no variations. We peformed a phantom study in a RTPS, where a phantom consisted of lung and bone legions in water. We calculated the dose received behind the lung and bone regions for 6 MV photon beams, in which the regions below the lung, water and bone received higher doses in this listed order. The result was the same for 10 MV photon beams. For the clinical application, the doses were calculated for the lung and pelvis. No difference was observed when using different electron density conversion tables with various CT voltages from a same CT. A relative dose difference of 1.5% was obtained when the CT machine for the density conversion table was different from that for the CT image for planning.

• Journal of radiological science and technology
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• v.38 no.2
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• pp.121-126
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• 2015

To image diagnosis in neurovascular diseases using Multi-Detector Computed Tomography(MDCT), injected the same contrast material when inspecting Brain Computed Tomography Angiography(BCTA) to examine radiation dose and Image quality on changing Cerebral Artery CT number by tube voltage. Executed an examination with same condition[Beam Collimation $128{\times}0.6mm$, Pitch 0.6, Rotation Time 0.5s, Slice Thickness 5.0mm, Increment 5.0mm, Delay Time 3.0sec, Care Dose 4D(Demension ; D)] except for tube voltage on 50 call patients for BCTA and divided them into two groups (25 people for a group, group A: 80, group B: 120kVp). From all the acquired images, set a ROI(Region of Interest) on four spots such as left cerebral artery, right cerebral artery, posterior cerebral artery and cerebral parenchyma to compare quantitative evaluation, qualitative evaluation and effective dose after measuring CT number value from Picture Archiving Communications System(PACS). Evaluating images with CT number acquired from BCTA examination, images with 80 kVp was 18% higher in Signal to Noise Ratio and 19% in Contrast to Noise Ratio than those with 120 kVp. It was seen that expose dose was decreased by over 50% with tube voltage 80 kVp than with 120 kVp. Group A (25 patients) was examination with tube voltage 80kVp while group B with 120 kVp to examine radiation dose and Image quality. It is considered effective to inspect with lower tube voltage than with conventional high kVp, which can reduce radiation dose without any affect on diagnosis.

• Journal of the Korean Society of Radiology
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• v.7 no.6
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• pp.383-387
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• 2013

Diagnostic imaging systems play a critical role in obtaining anatomical images, which increases the frequency of inspection all over the world. However the likelihood that patients are exposed to relatively high radiation dose increases, which may lead to an increase of patient dose due to unnecessary radiation exposure unless appropriate management is accompanied. Thus the revised edition of IEC 60601-2-44 which is constancy tests for CT equipment which is designated as special medical equipment and is subject to safety management was studied. The results suggested the 3rd has been revised rationally in order to overcome the limitations in the 2nd by adopting clear and enhanced references, which implies the replacement of IEC 60601-2-44 2nd edition with IEC 60601-2-44 3rd will prevent the patients from the harm from improper medical equipment.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.73-78
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• 2015

Purpose : Under the assumption of change to the amplitude based sorting, the study will use four dimensional computed tomography imaging (4DCT) arrayed using the phase based sorting to analyze the respiratory phase difference. Materials and Methods : The study analyzed the 4DCT (4-dimensional computed tomography) images of 10 liver cancer patients that were treated with respiratory gated radiotherapy from 2015 February to March. Using RPM respiratory gating (RPM 1.7.5, Varian, USA) equipment, imaging according to respiratory cycle of phase based sorting was acquired and using a treatment planning system (Pinnacle 9.2, Philips, USA) the acquired imaging according to respiratory cycle was used to measure the abdominal movement value by respiratory cycle. The measuring point was the point where the center point of the Marker Block and the body surface met in the 50% phase image and here the coordinate values Lateral, Vertical, Longitudinal (X, Y, Z) were set as reference points, and on the X, Z plane identical to the reference point, using the identical method the Y axis coordinate value of each 0%, 30%, 40%, 50%, 60%, 80% phase images were acquired to quantitatively measure the variation of distance to the Y axis. The abdominal movement value according to respiration was applied to the theoretical model that the value decreases linearly from maximum inhalation to maximum exhalation to divide the variation of my value to predict as amplitude value by respiratory cycle and conversely the variation in amplitude was recalculated with the phase variation deviation value to analyze. Results : The deviation value between expected value and actual location was the largest in the 30% phase with 0.24 cm, and standard deviation was also the largest in 30% phase with 0.13 cm. The effective value of the deviation value derived from the average of the deviation squared value of each patient appeared as minimum 0.7 cm, maximum 0.18 cm, average 0.12 cm, and standard deviation 0.4 cm. Also by dividing the actual movement distance value with the peak expiration value then converting it into %Phase, the deviation value with actual phase 16.5% in 30% phase, 10.0% and 40% phase, 10.0% and 60% phase, 15.4% and 80% phase, and overall average about 13%, and arraying based on amplitude, phase shift occurred and further it was from peak expiration the chance of deviation occurrence was increasingly measured. Conclusion : Based on the results of the study there were differences between value acquired based on theoretical model and actual value. Therefore in respiratory gated radiotherapy using external surrogates, there needs to be establishment of respiration gated radiation system that avoids the combination of two Sorting methods considering that there will be occurrence of treatment and corresponding clinical differences due to the phase difference that occur due to the Amplitude based Phase Sorting.

• Imaging Science in Dentistry
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• v.31 no.1
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• pp.1-7
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• 2001

Purpose : To evaluate the usefulness of the reconstructed 3-dimensional image on the personal computer in comparison with that of the CT workstation by quantitative comparison and analysis. Materials and Methods : The spiral CT data obtained from 27 persons were transferred from the CT workstation to a personal computer, and they were reconstructed as 3-dimensional image on the personal computer using V-works 2.0/sup TM/. One observer obtained the 14 measurements on the reconstructed 3-dimensional image on both the CT workstation and the personal computer. Paired Nest was used to evaluate the intraobserver difference and the mean value of the each measurement on the CT workstation and the personal computer. Pearson correlation analysis and % incongruence were also performed. Results: I-Gn, N-Gn, N-A, N-Ns, B-A, and G-Op did not show any statistically significant difference (p>0.05), B-O, B-N, Eu-Eu, Zy-Zy, Biw, D-D, Orbrd R, and L had statistically significant difference (p<0.05), but the mean values of the differences of all measurements were below 2 mm, except for D-D. The value of correlation coefficient y was greater than 0.95 at I-Gn, N-Gn, N-A, N-Ns, B-A, B-N, G-Op, Eu-Eu, Zy-Zy, and Biw, and it was 0.75 at B-O, 0.78 at D-D, and 0.82 at both Orbrd Rand L. The % incongruence was below 4% at I-Gn, N-Gn, N-A, N-Ns, B-A, B-N, G-Op, Eu-Eu, Zy-Zy, and Biw, and 7.18%, 10.78%, 4.97%, 5.89% at B-O, D-D, Orbrd Rand L respectively. Conclusion : It can be considered that the utilization of the personal computer has great usefulness in reconstruction of the 3-dimensional image when it comes to the economics, accessibility and convenience, except for thin bones and the landmarks which are difficult to be located.

• Radiation Oncology Journal
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• v.16 no.1
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• pp.63-69
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• 1998

Purpose : This study is to evaluate the efficacy of small bowel displacement system(SBDS) in post-operative pelvic radiation therapy(RT) of rectal cancer patients by measurement of small bowel volume included in the radiation fields receiving therapeutic dose. Materials and Method : Ten consecutive new rectal cancer patients referred to the department of Radiation Oncology of Samsung Medical Center in May of 1997 were included in this study. All patients were asked to drink $Castrographin^(R)$ before simulation and were laid prone for conventional simulation and CT scans with and without SBDS. The volume of opacified small bowel on CT scans, which was to be included in the radiation fields receiving therapeutic dose, was measured using Picture archiving and communication system (PACS). Results : The average small bowel volumes with and without SBDS were 176.0ml(5.2-415.6ml) and 185.1ml(54.5-434.2ml), respectively The changes of small bowel volume with SBDS compared to those without SBDS were more than $10\%$ decrease in three, less than 10% decrease in two, less than $10\%$ increase in three, and more than $10\%$ increase in two patients. Conclusion : No significant advantage of using SBDS in post-operative pelvic RT for rectal cancer patients has been shown by small bowel volume measurement using CT scan considering additional effort and time needed for simulation and treatment setup.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.203-209
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• 2022

One of the typical methods for lowering radiation dose while maintaining image quality of computed tomography (CT) is the use of model-based iterative reconstruction (MBIR). This study is to evaluate the image quality by adjusting the strength of the advanced modeled iterative reconstruction (ADMIRE), which is well known as a representative model of MBIR. The study was conducted using phantom, and CT images were obtained while adjusting the strength of ADMIRE in units of 1 to 5. Quantitative evaluation includes noise levels using coefficient of variation (COV) and contrast to noise ratio (CNR), as well as natural image quality evaluation (NIQE) and blind/referenceless image spatial quality evaluator (BRISQUE). As a result, in both noise level and blind quality evaluation results, the higher the strength of ADMIRE, the better the results were derived. In particular, it was confirmed that COV and CNR were improved 1.89 and 1.75 times at ADMIRE 5 compared to ADMIRE 1, respectively, and NIQE and BRISQUE were proved to be improved 1.35 and 1.22 times at ADMIRE 5 compared to ADMIRE 1, respectively. In conclusion, this study was proved that the reconstruction strength of ADMIRE had a great influence on the noise level and overall image quality evaluation of CT images.