• Radiation Oncology Journal
• /
• v.33 no.3
• /
• pp.242-249
• /
• 2015

Purpose: The purpose of this study is to compare the dosimetry of electron beam (EB) plans and three-dimensional helical tomotherapy (3DHT) plans for the patients with left-sided breast cancer, who underwent breast conserving surgery. Materials and Methods: We selected total of 15 patients based on the location of tumor, as following subsite: subareolar, upper outer, upper inner, lower lateral, and lower medial quadrants. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clip plus 1 cm margin. The conformity index (CI), homogeneity index (HI), quality of coverage (QC) and dose-volume parameters for the CTV, and organ at risk (OAR) were calculated. The following treatment techniques were assessed: single conformal EB plans; 3DHT plans with directional block of left anterior descending artery (LAD); and 3DHT plans with complete block of LAD. Results: 3DHT plans, regardless of type of LAD block, showed significantly better CI, HI, and QC for the CTVs, compared with the EB plans. However, 3DHT plans showed increase in the $V_{1Gy}$ at skin, left lung, and left breast. In terms of LAD, 3DHT plans with complete block of LAD showed extremely low dose, while dose increase in other OARs were observed, when compared with other plans. EB plans showed the worst conformity at upper outer quadrants of tumor bed site. Conclusion: 3DHT plans offer more favorable dose distributions to LAD, as well as improved target coverage in comparison with EB plans.

• Nuclear Engineering and Technology
• /
• v.53 no.4
• /
• pp.1189-1198
• /
• 2021

When performing remote tasks using robots in nuclear power plants, a 3D shape measurement system is advantageous in improving the efficiency of remote operations by easily identifying the current state of the target object for example, size, shape, and distance information. Nuclear power plants have high-radiation and underwater environments therefore the electronic parts that comprise 3D shape measurement systems are prone to degradation and thus cannot be used for a long period of time. Also, given the refraction caused by a medium change in the underwater environment, optical design constraints and calibration methods for them are required. The present study proposed a method for developing an underwater 3D shape measurement system with improved radiation tolerance, which is composed of commercial electric parts and a stereo camera while being capable of easily and readily correcting underwater refraction. In an effort to improve its radiation tolerance, the number of parts that are exposed to a radiation environment was minimized to include only necessary components, such as a line beam laser, a motor to rotate the line beam laser, and a stereo camera. Given that a signal processing circuit and control circuit of the camera is susceptible to radiation, an image sensor and lens of the camera were separated from its main body to improve radiation tolerance. The prototype developed in the present study was made of commercial electric parts, and thus it was possible to improve the overall radiation tolerance at a relatively low cost. Also, it was easy to manufacture because there are few constraints for optical design.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.12
• /
• pp.6251-6255
• /
• 2012

Radiation proctitis and radiation cystitis are major complications for patients with cervical carcinoma following radiotherapy. In the present study, we aimed to determine the potential risk factors for the development of radiation proctitis and radiation cystitis after irradiation. A total of 1,518 patients with cervical carcinoma received external beam radiotherapy (EBRT) followed by high-dose-rate intracavitary brachytherapy (HDRICB) in our hospital. The incidences of radiation proctitis and radiation cystitis were recorded and associations with different factors (age, time period, tumor stage) were analyzed with ${\chi}^2$ (chi-squared) and Fisher exact tests. We found that 161 and 94 patients with cervical carcinoma were diagnosed with radiation proctitis and radiation cystitis, respectively, following radiotherapy. The prevalence of Grade I-II radiation proctitis or radiation cystitis was significantly lower than that of Grade III (radiation proctitis: 3.82% vs. 6.76%, P < 0.05; radiation cystitis: 2.31% vs. 3.87%, P < 0.05) and was significantly enhanced in patients with late stage (IIIb) tumor progression compared to those in early stage (Ib, IIa) (P < 0.05). Moreover, the incidence of radiation proctitis and cystitis was not correlated with age or, time period following radiation, for each patient (P > 0.05). These observations indicate that a late stage of tumor progression is a potential risk factor for the incidence of radiation proctitis and cystitis in cervical carcinoma patients receiving radiotherapy.

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

• Journal of the Korean Magnetics Society
• /
• v.27 no.1
• /
• pp.18-22
• /
• 2017

The purpose of this study was to present an improved method of dose modulation over the increase of build-up for existing 6 MV photon beam. Two neodymium permanent magnets with a strength of 0.5 T (Tesla) were applied with a magnetic field perpendicular to the photon beam. The effects of dose on build-up region with or without the magnetic field were measured according to the magnet-to-magnet distance (MMS) and the magnet-to-surface distance (MSD). For MMS = 6 cm and MSD = 2.5 cm, $D_{0mm}$, $D_{2mm}$, $D_{5mm}$, and $D_{10mm}$ showed improved doses of 6.8 %, 14.6 %, 6.9 %, and 2.1 %, respectively, as compared with 6 MV open beam. In this study, the device with low strength magnetic field can be applied directly to the outside of the human body when the target volume located close to the skin is delivered with radiation. It is expected that the method of build-up modulation using a low strength magnetic field will be feasible in the clinical applications.

• Polymer(Korea)
• /
• v.36 no.1
• /
• pp.47-52
• /
• 2012

Abstract: In this study, PAN/$TiO_2$ fiber mats were fabricated from polyacrylonitrile (PAN) and titanium(IV) butoxide ($Ti(OBu)_4$) by an electrospinning method with various solution concentrations, applied voltages and solution flow rates. The fiber mats were irradiated with an electron beam to induce structural crosslinking and enhance photocatalytic activity. As a result, uniform and bead-free fibers without pits or cracks on surface were obtained at 5 wt% of $Ti(OBu)_4$ solution with 15 kV and 0.02 mL/min flow rate. The PAN/$TiO_2$ fiber mats were irradiated with an electron beam of 1.14 MeV acceleration voltage, 4 mA of current and $1{\times}10^4kGy$. Electron beam irradiation was enhanced the photocatalytic activity of PAN/$TiO_2$ nano fiber mat. The photocatalytic activity of the PAN/$TiO_2$ fiber mat was analyzed by degradation of methylene blue and volatile organic compounds.

• Radiation Oncology Journal
• /
• v.1 no.1
• /
• pp.41-45
• /
• 1983

To obtain 7 MeV electron beam which is suitable for treatment of the chest wall after radical of modified radical mastectomy, the authors reduced the energy of electron beam by means by Lucite plate inserted in the beam. To determine the proper thickness of the Lucite plate necessary to reduce the energy of 9 MeV electron beam to 6 MeV, dosimetry was made by using a parallel plate ionization chamber in polystyrene phantom. Separation between two adjacent fields, 7 MeV for chest wall and 12 MeV for internal mammary region, was studied by means of film dosimetry in both polytyrene phantom and Humanoid phantom. The results were as follows. 1. The average energy of 9 MeV electron beam transmitted through the Lucite plate was reduced. Reduction was proportional to the thickness of the Lucite plate in the rate of 1.7 MeV/cm. 2. The proper thickness of the Lucite plate necessary to obtain 6 MeV electron beam from 9 MeV was 1.2 cm. 3. 7 MeV electron beam, 80% dose at 2cm depth, is adequate for treatment of the chest wall. 4. Proper separation between two adjacent electron fields, 7 MeV and 12 MeV, was 5mm on both flat surface and sloping surface to produce uniform dose distribution.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.39 no.3
• /
• pp.273-279
• /
• 2012

Purpose : This study was aimed to calculate effective dose from cone beam CT and compare effective dose from periapical and panoramic radiography for mesiodens. Materials and Methods : Upper anteiror periapical, panoramic radiography and cone-beam CT were taken for diagnosis of mesiodens. The effective dose were calculated by using an anthropomorphic phantom loaded with thermoluminescent dosimeters at the 23 sites related to sensitive organs. Results : The highest absorbed doses were received by the mandibular body, parotid gland and cheek from periapical, panoramic and cone-beam CT, respectively. The effective doses for periapical, panoramic radiography and cone-beam CT measured 2, 18 and 48 ${\mu}Sv$. Conclusion : Cone-beam CT, although providing additional diagnostic benefits, exposes patients to higher levels of radiation than conventional periapical and panoramic radiography.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2004.11a
• /
• pp.69-71
• /
• 2004

The proton therapy of radiation therapy methods using Bragg Peak which is proton beam's characteristic dose distribution can give a normal tissue lower dose than cancer, comparing with the former existing radiation therapy methods. For exact treatment and patient' safety, we need to know proton beam's position in body, but a proton beam completely stops at treatment region and proton beam's range is uncertainly made by the variety of organs having each different density, so we aren't able to find a proton beam' position by suitable methods yet. With Monte Carlo Computing Method, as a result that we had simulated prompt gamma detection system using correlation of proton beam's absorbed dose distribution about water and prompt gamma distribution by nuclear interaction occurred by collisions of proton and water's hydrogen atoms, we could confirm that a proton beam's position was able to detect by using simulated prompt gamma detection system in body on the real-time

• Progress in Medical Physics
• /
• v.30 no.4
• /
• pp.112-119
• /
• 2019

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues. In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom. For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber. Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm. Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment. A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film. In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose. Results: The eye phantom was used for independent patient-specific QA. The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively. Conclusions: An eye phantom was developed and the performance was successfully validated. The phantom can be employed to verify the output and beam range for ocular proton therapy.