• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.33-41
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• 2019

Purpose: The purpose of this study is to improve the reduction of coverage of PTVs adjacent to organ at risk (OAR) by setting up overlapping Planning Target Volume (PTV) during Volumetric Modulated Arc Therapy(VMAT). Materials and Methods: In patients who received Whole Brain, Gall Bladder and Rectum radiation therapy, We compared the cover change, maximum dose, Homogenicity Index and Conformity Index of PTV and also compared the maximum dose and average dose change of Organ At Risk by organizing treatment plans that are not applied overlaped PTV and treatment plans that are applied overlaped PTV in areas where coverage is insufficient. Results: overage of treatment plans with overlapping PTVs was increased in all patients, and overall coverage was also increased in each of the four patients. The maximum dose for PTV was increased in five patients, and the Homogenicity Index and Conformity Index for all patients did not differ much. The maximum dose of the lens was increased by 1.12 times, and the maximum dose was decreased in two patients for brain stem. The mean dose of the eyeball was increased by a maximum of 1.15 times, and there was no significant difference between both parotid gland. In case of gallbladder cancer patients, the mean dose in the liver and colon was decreased, and the mean dose in the duodenum was increased. In the case of rectal cancer patients, the mean dose was reduced for both femur and bladder set as OARs. The overall MU was shown to be similar in four patients, excluding one. Conclusion: If the critical dose of OAR is considered and used properly, I think it is a useful way to improve coverage of PTV.

• YAKHAK HOEJI
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• v.50 no.2
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• pp.84-92
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• 2006

The present study investigated an effect of arsenic trioxide on the urethane-induced lung carcinogenesis in mice. To understand its carcinogenesis, we examined proliferating cell nuclear antigen (PCNA), apoptotic index as well as cell cycle-related proteins (cyclin D1, p21, and p27). Urethane was injected intraperitoneally in ICR mice, and then they were sacrificed at 5, 15, or 25 weeks following treatment of arsenic trioxide. Arsenic trioxide was given with tap water at a concentration of 1 mg/l (low-dose) and 5mg/1 (high-dose) for 25 weeks. During the carcinogenesis, sequential histological changes from hyperplasia to adenomas, and ultimately to overt carcinomas were noted. The development of hyperplasias, adenomas, and carcinomas in the lung were slightly increased by the treatment of low-dose arsenic trioxide. However, there is no correlation between dose and tumor multiplicity. The administration of low-dose arsenic trioxide, significantly increased the tumor size. The proliferative index observed on 5 weeks after significantly increased. Cyclin D1 and p21 protein, cell cycle related proteins, were more significantly increased in hyperplasia and adenoma in low dose arsenic treated group than urethane alone group. The p27 protein expression did not show any significantly changes with arsenic treated or untreated group. Low dose exposure to arsenic trioxide resulted in increased expression of cyclin D1 and p21 protein. The present results indicate that low-dose treatment of arsenic trioxide, but not high dose of it, partly modulate the cellular proliferation, cyclin D1, and p21 protein expression, and that this effect may contribute to accelerated development of lung adenocarcinomas in urethane-induced mice.

• Progress in Medical Physics
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• v.28 no.2
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• pp.54-60
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• 2017

This study was designed to measure transit dose with an electronic portal imaging device (EPID) in eight patients treated with intensity modulated radiotherapy (IMRT), and to verify the accuracy of dose delivery to patients. The calculated dose map of the treatment planning system (TPS) was compared with the EPID based dose measured on the same plane with a gamma index method. The plan for each patient was verified prior to treatment with a diode array (MapCHECK) and portal dose image prediction (PDIP). To simulate possible patient positioning errors during treatment, outcomes were evaluated after an anthropomorphic phantom was displaced 5 and 10 mm in various directions. Based on 3%/3 mm criteria, the $mean{\pm}SD$ passing rates of MapCHECK, PDIP (pre-treatment QA) for 47 IMRT were $99.8{\pm}0.1%$, $99.0{\pm}0.7%$, and, respectively. Besides, passing rates using transit dosimetry was $90.0{\pm}1.5%$ for the same condition. Setup errors of 5 and 10 mm reduced the mean passing rates by 1.3% and 3.0% (inferior to superior), 2.2% and 4.3% (superior to inferior), 5.9% and 10.9% (left to right), and 8.9% and 16.3% (right to left), respectively. These findings suggest that the transit dose-based IMRT verification method using EPID, in which the transit dose from patients is compared with the dose map calculated from the TPS, may be useful in verifying various errors including setup and/or patient positioning error, inhomogeneity and target motions.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.383-387
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• 2015

This study investigated the size specific dose estimates of difference localizer on pediatric CT image. Seventy one cases of pediatric abdomen-pelvic CT (M:F=36:35) were included in this study. Anterior-posterior and lateral diameters were measured in axial CT images. Conversion factors from American Association of Physicists in Medicine (AAPM) report 204 were obtained for effective diameter to determine size specific dose estimate (SSDE) from the CT dose index volume (CTDIvol) recorded from the dose reports. For the localizer of mid-slice SSDE was 107.63% higher than CTDIvol and that of xiphoid-process slices SSDE was higher than 92.91%. The maximum error of iliac crest slices, xiphoid process slices and femur head slices between mid-slices were 7.48%, 17.81% and 14.04%. In conclusion, despite the SSDE of difference localizer has large number of errors, SSDE should be regarded as the primary evaluation tool of the patient radiation in pediatric CT for evaluation.

• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.287-293
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• 2015

Because of esophageal cancer has the long length of the lesion and also inhomogeneous in depth. So, the radiation dose distribution was inhomogeneous in radiation therapy. To overcomes the dose distribution uniformity using half beam method. Patient's CT image was used radiation treatment planning. We used two planning methods that one is the using normal beam and another is using half beam. Than comparing the two radiotherapy planning using target coverage, dose volume histogram, conformity index, homogeneity index and normal tissues - heart, spinal cord, lung -. In results, Treatment planning using half beam is little more than normal beam in target coverage, dose volume histogram, conformity index, homogeneity index and normal tissues covering. However, If the patient is not correct position patients may arise a side effect. Thus, the using in Half beam involving the geometrically exact under lung cancer is considered to advantage.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.857-862
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• 2022

The purpose of this study was to evaluate a three-dimensional conformal radiotherapy (3D-CRT) treatment plan with regard to head tilting in whole-brain radiotherapy (WBRT) using TomoDirect (TD) mode in Tomotherapy. WBRT 3D-CRT by TD was compared for a total of five head tilt angles (-20°, -10°, 0°. +10° and +20°). The dose homogeneity index (HI) and prescription dose index (CI) were calculated to confirm the target coverage. The maximum and average doses for critical organs such as the lens, eyeball and parotid glands were calculated for different angles of head tilting. The HI and CI were closet to the result value of 1 at the head tilted angle +10° and +20°. At a head tilted angle of +10°, the dose to the lens and eyeballs decreased by about 74% and about 30%, when compared with the reference angle (0°), respectively. The results of this study suggest that a head angle of +10 with chin-up would save adequate target coverage and reduce exposure dose to the lens.

• Progress in Medical Physics
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• v.9 no.3
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• pp.185-192
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• 1998

It is necessarily to evaluate the energy of X-ray emitted from linear accelerator in order to determine the accurate absorbed dose. The method of direct measurement for x-ray energy is very difficult and impractical. Therefore the method of using beam quality index is generally used. Several dosimetry protocols recommend the use of quality indices such as depth of dose maximum at radiation central axis, dose gradient, and dose level. The linear accelerator manufactures follow the recommendation as dosimetry protocols. The study was performed for us to select the most suitable parameter among the Quality indices as described above. For photon beams of 4, 6, 10, 15, and 21 MV nominal energies produced by four kinds of accelerators(Mitsubishi, Scanditronix, Siemens, Varian) in eleven institutions, We evaluated the x-ray energies obtained by the Quality indices as recommended by several dosimetry protocols and manufactures. Results showed that there were energy spreads according to the same accelerators and Quality indices even though nominal energies were same. It appeared that the percent depth dose at 10 cm (D$_{10}$(%)) gave the smallest deviation and spread of energies. As energies increased, the energy deviation increased for all the quality indices. It is desirable for the use of unified quality index to compare the evaluation of beam quality at different institutions.

• Progress in Medical Physics
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• v.23 no.2
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• pp.99-105
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• 2012

We investigated the influence of photon energy, couch and collimator angle differences between arcs on dose distribution of RapidArc treatment planning for prostate cancer. RapidArc plans were created for 6 MV and 10 MV photons using 2 arcs coplanar and noncoplanar fields. The collimator angle differences between two arcs were $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$. The plans were optimized using same dose constrains for target and OAR (organ at risk). To evaluate the dose distribution, plans were analyzed using CI (conformity index), HI (homogeneity index), QOC (quality of coverage), etc. Photon energy, couch and collimator angle differences between arcs had a little influence on the target and OAR. The difference of dosimetric indices was less than 3.6% in the target and OAR. However, there was significant increase in the region exposed to low dose. The increase of V15% in the femur was 6.4% (left) and 5.5% (right) for the 6 MV treatment plan and 23.4% (left), 24.1% (right) for the noncoplanar plan. The increase of V10% in the Far Region distant from target was 54.2 cc for the 6 MV photon energy, 343.4 cc for the noncoplanar and 457.8 cc for the no collimator rotation between arcs.

• Progress in Medical Physics
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• v.30 no.4
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• pp.160-166
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• 2019

This study examined the clinical use of two newly installed computed tomography (CT) simulators in the Department of Radiation Oncology. The accreditation procedure was performed by the Korean Institute for Accreditation of Medical Imaging. An Xi R/F dosimeter was used to measure the CT dose index for each plug of the CT dose index phantom. Image qualities such as the Hounsfield unit (HU) value of water, noise level, homogeneity, existence of artifacts, spatial resolution, contrast, and slice thickness were evaluated by scanning a CT performance phantom. All test items were evaluated as to whether they were within the required tolerance level. CT calibration curves-the relationship between CT number and relative electron density-were obtained for dose calculations in the treatment planning system. The positional accuracy of the lasers was also evaluated. The volume CT dose indices for the head phantom were 22.26 mGy and 23.70 mGy, and those for body phantom were 12.30 mGy and 12.99 mGy for the first and second CT simulators, respectively. HU accuracy, noise, and homogeneity for the first CT simulator were -0.2 HU, 4.9 HU, and 0.69 HU, respectively, while those for second CT simulator were 1.9 HU, 4.9 HU, and 0.70 HU, respectively. Five air-filled holes with a diameter of 1.00 mm were used for assessment of spatial resolution and a low contrast object with a diameter of 6.4 mm was clearly discernible by both CT scanners. Both CT simulators exhibited comparable performance and are acceptable for clinical use.

• Journal of the Korean Society of Radiology
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• v.11 no.1
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• pp.55-61
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• 2017

There are no recommended test conditions for digital photography in Chest PA examinations. However, each company recommends shooting examinations of the high voltage applied to the previous analog examination. The condition that satisfies the value of 200 ~ 800 which is the recommended Exposure Index value recommended by Philips was selected, and the dose was evaluated by Monte Carlo simulation, and the SNR and CNR were compared. As a result, it was possible to reduce the effective dose up to 77% by controlling the tube voltage, tube current, and additional filter, not the conventional high voltage imaging method. Although there were some differences according to the test conditions, the image evaluation results were similar to the images. We will compare the exposure dose according to changes in tube voltage, tube current, and additional filter at the digital chest radiograph and evaluate the image quality of the image to propose optimal conditions.