• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.687-695
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• 2022

To find a 3D printer material that can replace lead used as a shield for high-energy electron beam treatment, the shielding composites were simulated by using MCNP6 programs. The Percent Depth Dose (PDD), Flatness, and Symmetry of linear accelerators emitting high-energy electron beams were measured, and the linear accelerator was compared with MCNP6 after simulation, confirming that the source term between the actual measurement and simulation was consistent. By simulating the lead shield, the appropriate thickness of the lead shield capable of shielding 95% or more of the absorbed dose was selected. Based on the absorption dose data for lead shield with a thickness of 3 mm, the shielding performance was analyzed by simulating 1, 5, 10, and 15 mm thicknesses of ABS+W (10%), ABS+Bi (10%), and PLA+Fe (10%). Each prototype was manufactured with a 3D printer, measured and analyzed under the same conditions as in the simulation, and found that when ABS+W (10%) material was formed to have a thickness of at least 10mm, it had a shielding performance that could replace lead with a thickness of 3mm. The surface morphology and atomic composition of the ABS+W (10%) material were evaluated using a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDS). From these results, it was confirmed that replacing the commercialized lead shield with ABS+W (10%) material not only produces a shielding effect such as lead, but also can be customized to patients using a 3D printer, which can be very useful for high-energy electron beam treatment.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.457-466
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• 2014

During irradiation of lesions in cancer treatment with high energy electrons, normal tissue and critical organs are protected by the shielding material. Scattered radiation that generated the shielding materials affect the depth dose and atomic number. Therefore, we want to examine secondary particles and the scattered photons through calculation and its associated analysis, and compare the measurement for the aluminum, copper, and lead shielding substance of which thickness has 95% charge reduction. Dose change rate which effected scattering radiation was found to be +0.88% for material thickness, +0.43% for atomic number, and +19.70%, +15.20%, +12.40% for measurement, +25.00%, +15.10%, +13.70% for calculation on the aluminum, copper, and lead materials of which thickness has 95% charge reduction, respectively, As a result, we found that scattering rate was dependent on thickness than atomic number. In the dose increasing rate, scattered electrons are more important than scattered photon. For the above mentioned reasons, I think that high atomic number materials should be applied to reduce scattered radiation that generated with thickness effect.

• The Journal of the Korean bone and joint tumor society
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• v.15 no.2
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• pp.122-129
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• 2009

Purpose: To evaluate treatment outcomes of malignant melanoma and to analyze the factors that contributes to outcomes. Materials and Methods: We reviewed the 51 cases of malignant melanoma from March, 1997 to March, 2004 and were followed up more than 5 years. Average age was 49.4. We compared 5-year survival rate for each age, gender, site of occurrence, depth of tumor, metastasis of regional lymph node and immuno-chemo therapy. Results: 5-year survival rate was 88.5% for the age group below 65, 88.0% for the age group 65 and above, 62.5% for male and 100% for female. 5-year survival rate for the site of occurrence showed 100% in upper extremities, and 80.0% in lower extremities and 100% in other sites. 5-year survival rate was 100% for the stage below Clark stage III and 79.3% for the stage above IV. In surgical resection, 5-year survival rate was 66.7% for lymph node metastasis group and 94.9% for non-lymph node metastasis group. Conclusion: The prognostic factors of malignant melanoma were gender, tumor site, depth of tumor (Clark's stage) and metastasis of regional lymph node. But, there was no relation between the age and the survival rate in our study.

• The Korean Journal of Nuclear Medicine
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• v.31 no.4
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• pp.433-439
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• 1997

$^{166}Ho$-chitosan complex, or $^{166}Ho$-CHICO, is a candidate pharmaceutical for intracavitary radiation therapy of cystic brain tumors because of the desirable nuclear characteristics of $^{166}Ho$ for therapeutic use and the suitable biological and chemical characteristics of chitosan, not to mention its ready producibility The amount of $^{166}Ho$-CHICO to be administered to obtain the goal therapeutic effect can be suggested by predicting the dose to the cyst wall for a varying pharmaceutical dose. When $^{166}Ho$-CHICO is infused into the cyst, the major part of the energy delivery by beta particles emitted from $^{166}Ho$ occurs in the cyst wall within 4mm in depth from the cyst wall surface. Also, realizing the attachment of $^{166}Ho$-CHICO to the cyst wall surface would change the predictions of dose to the cyst wall.

• Journal of Radiation Protection and Research
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• v.36 no.3
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• pp.160-167
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• 2011

This study conducts cross-comparison through verification of treatment planning of using beam spoiler and bolus, according to the dose variation of different tumor bed and metastatic lymph node cancers, against ionization and optically stimulated luminescence detectors(OSLDs), in head and neck radiotherapy. Verification of treatment planning examined the feasibility of inserting detectors through simulated solid dry water slabs under identical irradiated conditions from treatment planning system to measure beam spoiler and 0.5, 1 cm bolus. In addition, two detectors were cross-compared for verification of treatment planning accuracy and reliability within ${\pm}$2%. The study found that, given a beam spoiler thickness of 0.5 cm and beam spoiler-to-skin distance of 10 cm subjected to optimal dose distribution given for metastatic lymph node cancers, the bolus low-level skin dose was less, and the tumor bed dose reduced slightly. Additionally, two detectors were cross-compared for accuracy within ${\pm}$1%. Accordingly, The use of beam spoiler was determined that reduces skin side effects and can deliver an optimal dose distribution for tumor, and to apply to future clinical studies should be performed.

• Journal of radiological science and technology
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• v.29 no.4
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• pp.267-274
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• 2006

The evaluation of GB stones with ultrasound has proved to be useful procedure in patient with symptoms of cholelithiasis. GB is evaluated for size, wall thickness, presence of internal reflections within the lumen and posterior acoustic shadowing or enhancement in Ultrsonography. The patient position should be shifted during procedure to demonstrate further the presence of stone within the GB. Patient scanned at the Rt. subcostal region in supine, right lateral, Lt. down decubitus, and upright sitting position. So GB stone should shift to dependent area of GB. Often, GB is not markedly distended in the presence of cholethiasis, and so the diagnosis becomes more difficult. One of the more difficult areas for detection of a GB stones are embeded in the cystic duct region. And since the GB is adjacent to the duodenum and hepatic flexure, its may be difficult to visualizing a GB stone. When patient study position changes frome supine to other position, stones displaced the site. But if its are polyps, not changes the site whatever patient positions. It is very important to what make different GB stones or polyps. We have studied about mobility of GB stones according to the patients position(supine, Lt. down decubitus, $30^{\circ} LAO. sitting and hand-knee). So we have a result, stones wherever localized within the GB, changed 100% its position in the hand-knee position and the others appeared at least 90%. In this study, when a large stones are located through fundus-body and body-neck, does not changing the stones position in spite of varied patient's positions. But hand-knee positions can identified GB stones, because its make changed the position of stons from posterior wall to anterior wall within the GB. We recommend the hand-knee position for differentiation GB stones from polyps.

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.801-806
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• 2018

Germanium crystals have a dead layer that causes efficiency deterioration because the layer is not useful for detection but strongly weakens the photons. Thus, when the data provided by the manufacturer is used in the detector simulation model, there is a slight difference between the calculated efficiency and the measured efficiency.The shape and dimensions of the high purity germanium (HPGe) detector were determined by CT scans to accurately characterize the shape for the Monte Carlo roll simulation. It is found that the adjustment of the dead layer is a good match with the relative deviation of ${\pm}3%$ between the measurement efficiency and the simulation efficiency at the energy range of 50 - 1500 keV. Simulation data were compared by varying the thickness of the dead layer. The new Monte Carlo simulations were compared with the experimental results to obtain new blank layer thicknesses. The difference in dead layer results for the 1.5 mm thick end cap simulation model in 1.4 and 1.6 mm thick End Cap simulation models was a systematic error due to the accuracy of the end cap dimensions. After considering all errors including statistical errors and systematic errors, the thickness of the detector was calculated as $1.02{\pm}0.14mm$. Therefore, it was confirmed that the increase in the thickness of the dead layer causes the effect to be effected on the efficiency reduction.

• Radiation Oncology Journal
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• v.9 no.2
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• pp.343-350
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• 1991

The quasi-conformation therapy was performed to get a homogeneous dose distributions for irregeular shaped tumor lesion by using the arc moving beam and beam modifying filter which was made by cerrobend alloy($\rho$=9.4 g/cc) metal. In our dose calcuation programme, it was fundmentally based on Clarkson's method to calcuate the irregular multi-step block field in rotation therapy. In this study, the expected relative depth doses under multipartial attenuator agree well with measured data at same plane. The results of comparison the dose computation with that of TLD measurement are very closed within ${\pm}5\%$ uncertainties in the irradiation to phantom with quasi-comformation method. And it has shown that irregular typed multi-step filter can be applied to quasi-conformation therapy in high energy radiation plannings.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.79-88
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• 2021

Objectives: Bolus, which combines 3D-bolus and Step-bolus, was produced and its usefulness is evaluated. Materials and Methods: A Bolus was manufactured with a thickness of 10mm and 5mm using a 3D printer (3D printer, USA), and a Step Bolus of 5mm was bonded to a 5mm thick bolus. In order to understand the characteristics of Step bolus and 3D bolus, the differences in relative electron density, HU value, and mass density of the two bolus were investigated. These two Bolus were applied to anthropomorpic phantom to confirm its effectiveness. After all contouring of the phantom, a treatment plan was established using the computed treatment planning system (Eclipse 16.1, Varian medical system, USA). Treatment plan was performed using electron beam 6MeV, nine dose measurement points were designated on the phantom chest, air-gap was measured at that point, and dose evaluation was performed at the same point for each bolus applied using a glass dosimeter (PLD). Results: Bolus, which combines 3D-bolus 5mm and Step-bolus 5mm, was manufactured and evaluated compared with 3D-bolus 1cm. The relative electron density of 3D Bolus was 1.0559 g/cm2 and the step Bolus was 1.0590 g/cm2, which was different by 0.01%, so the relative electron density was almost the same. In the lightweight measurement of air-gap, the combined bolus was reduced to 54.32% for all designated points compared to 3D-bolus. In the dose measurement using a glass dose meter (PLD), the consistency was high in phantom using combined bolus at most points except the slope point. Conclusion: Combined bolus made by combining 3D-bolus and Step-bolus has all the advantages of 3D-bolus and Step-bolus. In addition, by dose inaccuracy due to Air-gap, more improved dose distribution can be shown, and effective radiation therapy can be performed.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.1-10
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• 2002

High energy photon beams from medical linear accelerators produce large scattered radiation by various components of the treatment head, collimator and walls or objects in the treatment room including the patient. These scattered radiation do not provide therapeutic dose and are considered a hazard from the radiation safety perspective. Scattered dose of therapeutic high energy radiation beams are contributed significant unwanted dose to the patient. ICRP take the position that a dose of 500mGy may cause abortion at any stage of pregnancy and that radiation detriment to the fetus includes risk of mental retardation with a possible threshold in the dose response relationship around 100 mGy for the gestational period. The ICRP principle of as low as reasonably achievable (ALARA) was recommended for protection of occupation upon the linear no-threshold dose response hypothesis for cancer induction. We suggest this ALARA principle be applied to the fetus and testicle in therapeutic treatment. Radiation dose outside a photon treatment filed is mostly due to scattered photons. This scattered dose is a function of the distance from the beam edge, treatment geometry, primary photon energy, and depth in the patient. The need for effective shielding of the fetus and testicle is reinforced when young patients ate treated with external beam radiation therapy and then shielding designed to reduce the scattered photon dose to normal organs have to considered. Irradiation was performed in phantom using high energy photon beams produced by a Varian 2100C/D medical linear accelerator (Varian Oncology Systems, Palo Alto, CA) located at the Yonsei Cancer Center. The composite phantom used was comprised of a commercially available anthropomorphic Rando phantom (Phantom Laboratory Inc., Salem, YN) and a rectangular solid polystyrene phantom of dimensions $30cm{\times}30cm{\times}20cm$. the anthropomorphic Rando phantom represents an average man made from tissue equivalent materials that is transected into transverse 36 slices of 2.5cm thickness. Photon dose was measured using a Capintec PR-06C ionization chamber with Capintec 192 electrometer (Capintec Inc., Ramsey, NJ), TLD( VICTOREEN 5000. LiF) and film dosimetry V-Omat, Kodak). In case of fetus, the dosimeter was placed at a depth of loom in this phantom at 100cm source to axis distance and located centrally 15cm from the inferior edge of the $30cm{\times}30cm^2$ x-ray beam irradiating the Rando phantom chest wall. A acryl bridge of size $40cm{\times}40cm^2$ and a clear space of about 20 cm was fabricated and placed on top of the rectangular polystyrene phantom representing the abdomen of the patient. The leaf pot for testicle shielding was made as various shape, sizes, thickness and supporting stand. The scattered photon with and without shielding were measured at the representative position of the fetus and testicle. Measurement of radiation scattered dose outside fields and critical organs, like fetus position and testicle region, from chest or pelvic irradiation by large fie]d of high energy radiation beam was performed using an ionization chamber and film dosimetry. The scattered doses outside field were measured 5 - 10% of maximum doses in fields and exponentially decrease from field margins. The scattered photon dose received the fetus and testicle from thorax field irradiation was measured about 1 mGy/Gy of photon treatment dose. Shielding construction to reduce this scattered dose was investigated using lead sheet and blocks. Lead pot shield for testicle reduced the scatter dose under 10 mGy when photon beam of 60 Gy was irradiated in abdomen region. The scattered photon dose is reduced when the lead shield was used while the no significant reduction of scattered photon dose was observed and 2-3 mm lead sheets refuted the skin dose under 80% and almost electron contamination. The results indicate that it was possible to improve shielding to reduce scattered photon for fetus and testicle when a young patients were treated with a high energy photon beam.