• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.25-30
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• 2023

As 3D printing technology is used in the medical field, interest in metal materials is increasing. The Department of Radiation Oncology uses a shielding block to shield the patient's normal tissue from unnecessary exposure during electron beam therapy. However, problems such as handling of heavy metal materials such as lead and cadmium, reproducibility according to skill level and uncertainty of arrangement have been reported. In this study, candidate materials that can be used for metal 3D printing are selected, and the physical properties and radiation dose of each material are analyzed to develop a customized shielding block that can be used in electron beam therapy. As candidate materials, aluminum alloy (d = 2.68 g/cm³), titanium alloy (d = 4.42 g/cm³), and cobalt chromium alloy (d = 8.3 g/cm³) were selected. The thickness of the 95% shielding rate point was derived using the Monte Carlo Simulation with the irradiation surface and 6, 9, 12, and 16 energies. As a result of the simulation, among the metal 3D printing materials, cobalt chromium alloy (d = 8.3 g/cm³) was similar to the existing shielding block (d = 9.4 g/cm³) in shielding thickness for each energy. In a follow-on study, it is necessary to evaluate the usefulness in clinical practice using customized shielding blocks made by metal 3D printing and to verify experiments through various radiation treatment plan conditions.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.163-170
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• 2014

Purpose : If electron, chosen for superficial oncotherapy, was applied with bolus, it could work as an important factor to a therapy result by showing a drastic change in surface dose. Hence the calculation value and the actual measurement value of surface dose of Treatment Planning System (TPS) according to four variables influencing surface dose when using bolus on an electron therapy were compared and analyzed in this paper. Materials and Methods : Four variables which frequently occur during the actual therapies (A: bolus thickness - 3, 5, 10 mm, B: field size - $6{\time}6$, $10{\time}10$, $15{\time}15cm2$, C: energy - 6, 9, 12 MeV, D: gantry angle - $0^{\circ}$, $15^{\circ}$) were set to compare the actual measurement value with TPS(Pinnacle 9.2, philips, USA). A computed tomography (lightspeed ultra 16, General Electric, USA) was performed using 16 cm-thick solid water phantom without bolus and total 54 beams where A, B, C, and D were combined after creating 3, 5 and 10 mm bolus on TPS were planned for a therapy. At this moment SSD 100 cm, 300 MU was investigated and measured twice repeatedly by placing it on iso-center by using EBT3 film(International Specialty Products, NJ, USA) to compare and analyze the actual measurement value and TPS. Measured film was analyzed with each average value and standard deviation value using digital flat bed scanner (Expression 10000XL, EPSON, USA) and dose density analyzing system (Complete Version 6.1, RIT, USA). Results : For the values according to the thickness of bolus, the actual measured values for 3, 5 and 10 mm were 101.41%, 99.58% and 101.28% higher respectively than the calculation values of TPS and the standard deviations were 0.0219, 0.0115 and 0.0190 respectively. The actual values according to the field size were $6{\time}6$, $10{\time}10$ and $15{\time}15cm2$ which were 99.63%, 101.40% and 101.24% higher respectively than the calculation values and the standard deviations were 0.0138, 0.0176 and 0.0220. The values according to energy were 6, 9, and 12 MeV which were 99.72%, 100.60% and 101.96% higher respectively and the standard deviations were 0.0200, 0.0160 and 0.0164. The actual measurement value according to beam angle were measured 100.45% and 101.07% higher at $0^{\circ}$ and $15^{\circ}$ respectively and standard deviations were 0.0199 and 0.0190 so they were measured 0.62% higher at $15^{\circ}$ than $0^{\circ}$. Conclusion : As a result of analyzing the calculation value of TPS and measurement value according to the used variables in this paper, the values calculated with TPS on 5 mm bolus, $6{\time}6cm2$ field size and low-energy electron at $0^{\circ}$ gantry angle were closer to the measured values, however, it showed a modest difference within the error bound of maximum 2%. If it was beyond the bounds of variables selected in this paper using electron and bolus simultaneously, the actual measurement value could differ from TPS according to each variable, therefore QA for the accurate surface dose would have to be performed.

• Progress in Medical Physics
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• v.9 no.2
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• pp.65-71
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• 1998

The aims are to evaluate the effects of an 1.0 cm acrylic plate and SSD on the dose profile and depth dose distribution of 9 MeV electron beam and to analyse adequacy for using an acrylic plate to reduce energy of electron beams. An acrylic plate of 1.0 cm thickness was used to reduce energy of 9 MeV electron beam to 7 MeV. The plate was put on an electron applicator at 65.4 cm distance from x-ray target. The size of the applicator was 10${\times}$l0cm at 100 cm SSD. For 100cm, l05cm and 110cm SSD, depth dose on beam axis and dose profiles at d$\_$max/ on two principal axes were measured using a 3D water phantom. From depth dose distributions, d$\_$max/, d$\_$85/, d$\_$50/ and R$\_$p/, surface dose, and mean energy and peak energy at surface were compared. From dose profiles flatness, penumbra width and actual field size were compared. For comparison, 9 MeV electron beams were measured. Surface dose of 7 MeV electron beams was changed from 85.5% to 82.2% increasing SSD from 100 cm to 110 cm, and except for dose buildup region, depth dose distributions were independent of SSD. Flatness of 7 MeV ranged from 4.7% to 10.4% increasing SSD, comparing 1.4% to 3.5% for 9 MeV. Penumbra width of 7 MeV ranged from 1.52 cm to 3.03 cm, comparing 1.14 cm to 1.63 cm for 9 MeV. Actual field size increased from 10.75 cm to 12.85 cm with SSD, comparing 10.32 cm to 11.46 cm for 9 MeV. Virtual SSD's of 7 and 9 MeV were respectively 49.8 cm and 88.5cm. In using energy reducer in electron therapy, depth dose distribution were independent of SSD except for buildup region as well as open field. In case of using energy reducer, increasing SSD made flatness to deteriorate more severely, penumbra width more wide, field size to increase more rapidly and virtual SSD more short comparing with original electron beam. In conclusion, it is desirable to use no energy reducer for electron beam, especially for long SSD.

• The Journal of Korean Society for Radiation Therapy
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• v.17 no.2
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• pp.161-166
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• 2005

Purpose : Electron is used for the treatment of skin cancer, breast cancer, and head and neck cancer in clinic. Our study is performed to check the isodose distribution in source surface distance(SSD)and source bolus distance(SBD)setup, nipple influence to isodose distribution of electron, junctional area isodose variation of photon and electron field. Materials and Methods : The electron dose distribution measures the diameter for 20 cm hemisphere paraffin phantom 2 made. It inserted the film between 2 paraffin phantom and it investigated it got radiation and dose distribution curve. Results : The 8% of isodose difference is with the surface distance(SSD)and source bolus distance(SBD)setup. The electon when the nipple exists inside the field, as nipple size it cuts the bolus and when it puts out and there is a possibility of getting the dose distribution which is homogeneous. When in the junction of electron and photon it uses the bolus it uses in the electron field whole, there is a possibility of getting the dose distribution which is homogeneous. Conclusion : The dose distribution decrease from the SBD setup. To reduce the influence of nipple, corresponding volume of bolus should be removed. And bolus covering all the electron field reduced hot and cold spot of junctional area of photon. In the future becomes the research which sees an effective electron therapy.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.517-522
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• 2020

Electron beam have many factors that affect dose distribution, so even if identical settings are used, they should be identified and used for radiation treatment, and the effects on the structures in the body are sensitive, making it difficult to investigate uniform dose distribution on tumors. In this study, a dosimeter was produced using PbI₂ which is a photoelectric material, and electrical characteristics were analyzed for 6, 9, and 12 MeV electronics in linear accelerators. The reproducibility test results showed that RSD were 1.1215%, 1.0160%, and 0.05137% respectively at 6, 9, and 12 MeV energies, indicating that the output signals were stable. The linearity evaluation results showed that the R² values of the reliability indicator for straight line trend lines were 0.9999, 0.9999, and 0.9994, respectively, at 6, 9, and 12 MeV, to confirm that the output signal was proportional to PbI₂ as dose increased. The PbI₂ dosimeter in this study is judged to be highly applicable to electromagnet measurement and is thought to be able to be used as a basic study of electron detector through photoelectric material.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.841-848
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• 2020

In the field of radiation therapy using photon beams and electron beams, since each patient has a different sensitivity to radiation, skin side effects may occur even at the same dose. Therefore, if there is a risk of excessive dose to the skin, a dosimeter is attached to verify whether the correct dose is being investigated. However, since the skin dosimeter checks the attachment site visually by measuring a point dose, it is difficult to confirm an accurate dose distribution. As a result, the measurement and simulation errors of the material HgI₂ in the 6 MV photon beam were 3.73% and 5.24%, respectively, at the minimum thickness of 25 ㎛, and the material PbI₂ was 4.73% and 5.65%, respectively. On the other hand, as a result of the 6 MeV electron beam, the measurement and simulation errors of the material HgI₂ were 1.35% and 1.12%, respectively, at a minimum thickness of 25 ㎛, and the material PbI₂ showed relatively low attenuation error, 1.67% and 1.20%, respectively. Therefore, it was evaluated that the thickness of the photon beam within 25 ㎛ and the electron beam within 100 ㎛ is suitable to have a reduction rate error within 5%. This study presents a new research direction for a flexible dosimeter attached to the human body that is required in clinical practice and the construction conditions of a future skin dosimeter.

• Progress in Medical Physics
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• v.28 no.1
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• pp.33-38
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• 2017

Creating individualized build-up material for superficial photon beam radiation therapy at irregular surface is complex with rice or commonly used flat shape bolus. In this study, we implemented a workflow using 3D printed patient specific bolus and describe our clinical experience. To provide better fitted build-up to irregular surface, the 3D printing technique was used. The PolyLactic Acid (PLA) which processed with nontoxic plant component was used for 3D printer filament material for clinical usage. The 3D printed bolus was designed using virtual bolus structure delineated on patient CT images. Dose distributions were generated from treatment plan for bolus assigned uniform relative electron density and bolus using relative electron density from CT image and compared to evaluate the inhomogeneity effect of bolus material. Pretreatment QA is performed to verify the relative electron density applied to bolus structure by gamma analysis. As an in-vivo dosimetry, Optically Stimulated Luminescent Dosimeters (OSLD) are used to measure the skin dose. The plan comparison result shows that discrepancies between the virtual bolus plan and printed bolus plan are negligible. (0.3% maximum dose difference and 0.2% mean dose difference). The dose distribution is evaluated with gamma method (2%, 2 mm) at the center of GTV and the passing rate was 99.6%. The OSLD measurement shows 0.3% to 2.1% higher than expected dose at patient treatment lesion. In this study, we treated Mycosis fungoides patient with patient specific bolus using 3D printing technique. The accuracy of treatment plan was verified by pretreatment QA and in-vivo dosimetry. The QA results and 4 month follow up result shows the radiation treatment using 3D printing bolus is feasible to treat irregular patient skin.

• Radiation Oncology Journal
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• v.3 no.1
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• pp.51-58
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• 1985

This study analyzes fifteen patients who underwent a course of radiation therpy for their vulva cancer in the Department of Radiation Oncology, College of Medicine, Yonsei University from January, 1971 to April, 1985. Four patients had initial surgery for their vulva cancer and were subsequently treated by a course of adjuvant radiation therapy. Eleven patients were given radiation therapy as the initial course of therapy, and one of these was in adjuvant setting before radical surgery. Treatment in each instance was individuilzed and usually consisted of some components of external beam, brachytherapy, and/or electron beam therapy. Primary local control rate in all cases was $53\%(8/15),\;40\%(4/10)$ in the radiation therapy alone group and $80\%(4/5)$ in the radiation therapy combined with surgery group. Treatment failures were noted in 7/10 in the radiation therapy alone group and 2/5 in the radiation therapy combined with surgery group. The most common failure site was primary site failure(vulva).

• Radiation Oncology Journal
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• v.7 no.1
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• pp.85-92
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• 1989

Dosimerty based on electron spin resonance (ESR) analysis of radiation induced free radicals in amino acids is relevant to biological dosimetry applications. Alanine detectors are without walls and are tissue equivalent. Therefore, alanine ESR dosimetry looks promising for use in the therapy level. The dose range of the alanine/ESR dosimetry system can be extended down to 1 Gy. In water phantom the absorbed dose of electrons generated by a medical linear accelerator of different initial energies $(6\~21MeV)$ and therapeutic dose levels (1~60 Gy) was measured. Furthermore, depth dose measurements carried out with alanine dosimeters were compared with ionization chamber measurements. As the results, the measured absorbed doses for shallow depth of initial electron energies above 15 MeV were higher by$2\~5\%$ than those calculated by nominal energy $C_E$ factors. This seems to be caused by low energy scattered beams generated from the scattering foil and electron cones of beam projecting device in medical linear accelerator.

• Radiation Oncology Journal
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• v.4 no.2
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• pp.165-172
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• 1986

In electron therapy, lead cutout or low-melting alloy block is used for shaping the field. Material for shaping electron field affects the output factor as wet 1 as the collimation system. The authors measured the output factors of electron beams for shaped fields from Clinac-18 using ionization chamber of Farmer type in polystyrene phantom. They analyzed the parameters that affect the output factors. The output factors of electron beams depend on the incident energy, collimation system and size of shaped field. For shaped field the variation of output factor for the field size (A/P) has appearence of a smooth curve for all energy and all applicator collimator combination. The output factors for open field deviate from the curves for shaped fields. An output factor for a given field can be calculated by equivalent field method such as A/P method, if a combination of applicator and collimator is fixed.