• Journal of the Korean Society of Radiology
• /
• v.18 no.3
• /
• pp.239-248
• /
• 2024

Radiation therapy uses high energy, which can have side effects on the human body. Therefore, it is important to ensure that the appropriate dose is set for irradiation and to have confidence in the radiation produced by the generator. The EPR/Alanine dosimetry system is characterized by water equivalence, dose response linearity, and low fading, which makes it useful for quality control of radiation therapy equipment. In this study, we compared the signal and dose response curves of EPR/Alanine dosimetry by mass of alanine using 6 MV energy of a LINAC. An alanine dosimeter and EPR spectrometer from Burker, and a LINAC from Elekta, were used. A dose response curve and a 1st order regression equation were constructed from the irradiated dose and the EPR signal from the alanine dosimeter. We compared the signal magnitude and dose response curve with mass and checked the confidence through the measurement uncertainty of the dose response curve. As a result, it was found that the magnitude of the EPR signal increased by about 1.3 times at 64.5 mg, and the sensitivity of the dose response curve increased as the mass increased. The measurement uncertainty was evaluated to be between 5.84 % and 8.93 %. Through this study, it is expected that the EPR/alanine dosimetry system can be applied to the quality assurance and quality control of a LINAC.

• Progress in Medical Physics
• /
• v.18 no.1
• /
• pp.13-19
• /
• 2007

The purpose of study Is to Investigate whether glass rod detector (GRD) would be suitable for dosimeter of radiotherapy units. A GRD Is used for the measurement of the ou4put factors and x-axis beam profiles from Gamma Knife. The output factors measured with GRD from the 14, 8 and 4mm collimators relative to the 18mm collimator are $0.980{\pm}0.013,\;0.949{\pm}0.013\;and\;0.872{\pm}0.012$, respectively. The output factors obtained with a GRD are within 1.0% In good agreement with the values recommended by the manufacture. The full width at half maximum (FWHM) of x-axis beam profiles measured with GRD are 5.9mm at a 4mm collimator.

• Journal of the Korean Society of Radiology
• /
• v.9 no.5
• /
• pp.279-285
• /
• 2015

The eye of human is a radiation sensitive organ and this organ should be shielded from radiation exposure during brain CT procedures. In the brain CT procedures, bismuth protector using to reduce the radiation exposure dose for eye. But protecting the bismuth always accompanies problem of the image quality reduction including artifact. This study aim is the eye radiation exposure dose and image quality evaluation of the new tube current modulation such as new organ based-tube current modulation, longitudinal-TCM, angular-TCM between shielding scan technique using bismuth and lead glasses. As a result, radiation dose of eye is reduced 25.88% in new OB TCM technique then reference scan technique and SNR new OB TCM is 6.05 higher than bismuth shielding scan technique and lower than reference scan technique. In clinical brain CT, new OB TCM technique will contribute to reduction of radiation dose for eye without decrease of image quality.

• Journal of radiological science and technology
• /
• v.40 no.4
• /
• pp.621-626
• /
• 2017

In this paper, an optical dosimetric system for radiation dose measurement is developed and characterized for 100 MeV proton beams in KOMAC(Korea Multi-Purpose Accelerator Complex). The system consists of 10 wt% Ultima GoldTM liquid organic scintillator in the ethanol, a camera lens(50 mm / f1.8), and a high sensitivity CMOS(complementary metal-oxide-semiconductor) camera (ASI120MM, ZWO Co.). The FOV(field of view) of the system is designed to be 150 mm at a distance of 2 m. This system showed sufficient linearity in the range of 1~40 Gy for the 100 MeV proton beams in KOMAC. We also successfully got the percentage depth dose and the isodose curves of the 100 MeV proton beams from the captured images. Because the solvent is not a human tissue equivalent material, we can not directly measure the absorbed dose of the human body. Through this study, we have established the optical dosimetric procedure and propose a new volume dose assessment method.

• Journal of the Korean Society of Radiology
• /
• v.16 no.6
• /
• pp.681-686
• /
• 2022

In this study, a scintillation resin for 3D printing was fabricated with 1.0 wt% of PPO organic scintillator, 5.0 wt% of MMA, and commercial acrylic resin. Using the scintillation resin, 3D-shaped plastic scintillator radiation sensors were successfully fabricated quickly and inexpensively with a commercial 3D DLP printer. The 3D printed plastic scintillator has a good dose-output linearity of R-square 0.998 was obtained in the range of 1 to 10 nA of beam current of the 45 MeV proton beam. The developed 3D plastic scintillator has low light output, so there is a limit to its use in low-dose-rate gamma-ray or X-ray dosimetry. However, it was confirmed that the tissue equivalent material could be usefully used for measuring high energy or high dose rates radiation, such as proton beams and ultra-high dose rate beams.

• The Journal of Korean Society for Radiation Therapy
• /
• v.17 no.2
• /
• pp.133-140
• /
• 2005

Purpose : This test is designed to identify the validity of treatment plan by implementing real-time dosimetry by means of dose that is absorbed into PTV and OAR when preparing doses of 3D and POP plans. Materials and Methods : In treatment. error can be calculated be comparing Exp. Dose with the actual dose, which has been converted from 'the reading value obtained by placing diode detector on the area to be measured'. Same test can be repeated using Alderson-Rando phantom. Results : Errors were found: A patient(POP plan): 197.6/199=-1.2%, B patient(3D-plan): 199.9/198.7=+0.6%, C patient: 196/200=-1.5%. In addition, considering the resulted value of measuring OAR besides target-dose for C patient showed 96/200, representing does of 47%, the purpose of protection was judged to be duly accomplished. Also it was acknowledged the resulted value of -3.7% met the targeted dose within the range of ${\pm}5%$. Conclusion : Aimed for identifying the usefulness of pre-treatment dose measurement using diode detector, this test was useful to evaluate the validity of curing because it resulted in the identification of category to be protected as well as t dose. Moreover, it is thought to have great advantage in ascertaining the dose of target, dose of which is not calculated yet. Similar to L-gram before treatment, this test is thought to be very effective so that it can bring great advantages in the aspects such as validity of curing method and post-treatment plan as well.

• Progress in Medical Physics
• /
• v.21 no.3
• /
• pp.253-260
• /
• 2010

Most brachytherapy treatment planning systems employ a dosimetry formalism based on the AAPM TG-43 report which does not appropriately consider tissue heterogeneity. In this study we aimed to set up a simple Monte Carlo-based intracavitary high-dose-rate brachytherapy (IC-HDRB) plan verification platform, focusing particularly on the robustness of the direct Monte Carlo dose calculation using material and density information derived from CT images. CT images of slab phantoms and a uterine cervical cancer patient were used for brachytherapy plans based on the Plato (Nucletron, Netherlands) brachytherapy planning system. Monte Carlo simulations were implemented using the parameters from the Plato system and compared with the EBT film dosimetry and conventional dose computations. EGSnrc based DOSXYZnrc code was used for Monte Carlo simulations. Each $^{192}Ir$ source of the afterloader was approximately modeled as a parallel-piped shape inside the converted CT data set whose voxel size was $2{\times}2{\times}2\;mm^3$. Bracytherapy dose calculations based on the TG-43 showed good agreement with the Monte Carlo results in a homogeneous media whose density was close to water, but there were significant errors in high-density materials. For a patient case, A and B point dose differences were less than 3%, while the mean dose discrepancy was as much as 5%. Conventional dose computation methods might underdose the targets by not accounting for the effects of high-density materials. The proposed platform was shown to be feasible and to have good dose calculation accuracy. One should be careful when confirming the plan using a conventional brachytherapy dose computation method, and moreover, an independent dose verification system as developed in this study might be helpful.

• The Journal of Korean Society for Radiation Therapy
• /
• v.19 no.1
• /
• pp.27-33
• /
• 2007

Purpose: We have performed SRS (stereotactic radiosurgery) for avm (arterry vein malformation) and brain cancer. In order to verify dose and localization of SRS, dose distributions from TPS ($X-Knife^{(R)}$ 3.0, Radionics, USA) and GafChromic $EBT^{(R)}$ film in a head phantom were compared. Materials and Methods: In this study, head and neck region of conventional humanoid phantom was modified by substituting one of 2.5 cm slap with five 0.5 cm acrylic plates to stack the GafChromic $EBT^{(R)}$ film slice by slice with 5 mm intervals. Four films and five acrylic plates were cut along the contour of head phantom in axial plane. The head phantom was fixed with SRS head ring and adapted SRS localizer as same as real SRS procedure. CT images of the head phantom were acquired in 5 mm slice intervals as film interval. Five arc 6 MV photon beams using the SRS cone with 2 cm diameter were delivered 300 cGy to the target in the phantom. Ten small pieces of the film were exposed to 0, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 cGy, respectively to calibrate the GafChromic $EBT^{(R)}$ film. The films in the phantom were digitized after 24 hours and its linearity was calibrated. The pixel values of the film were converted to the dose and compared with the dose distribution from the TPS calculation. Results: Calibration curve for the GafChromic $EBT^{(R)}$ film was linear up to 900 cGy. The R2 value was better than 0.992. Discrepancy between calculated from $X-Knife^{(R)}$ 3.0 and measured dose distributions with the film was less than 5% through all slices. Conclusion: It was possible to evaluate every slice of humanoid phantom by stacking the GafChromic EBT film which is suitable for 2 dimensional dosimetry, It was found that film dosimetry using the GafChromic $EBT^{(R)}$ film is feasible for routine dosimetric QA of stereotactic radiosurgery.

• Progress in Medical Physics
• /
• v.26 no.3
• /
• pp.119-126
• /
• 2015

The purpose of this study is to analyze motion-induced dose error generated by each tumor motion parameters of irregular tumor motion in helical tomotherapy. To understand the effect of the irregular tumor motion, a simple analytical model was simulated. Moving cases that has tumor motion were divided into a slightly irregular tumor motion case, a large irregular tumor motion case and a patient case. The slightly irregular tumor motion case was simulated with a variability of 10% in the tumor motion parameters of amplitude (amplitude case), period (period case), and baseline (baseline case), while the large irregular tumor motion case was simulated with a variability of 40%. In the phase case, the initial phase of the tumor motion was divided into end inhale, mid exhale, end exhale, and mid inhale; the simulated dose profiles for each case were compared. The patient case was also investigated to verify the motion-induced dose error in 'clinical-like' conditions. According to the simulation process, the dose profile was calculated. The moving case was compared with the static case that has no tumor motion. In the amplitude, period, baseline cases, the results show that the motion-induced dose error in the large irregular tumor motion case was larger than that in the slightly irregular tumor motion case or regular tumor motion case. Because the offset effect was inversely proportion to irregularity of tumor motion, offset effect was smaller in the large irregular tumor motion case than the slightly irregular tumor motion case or regular tumor motion case. In the phase case, the larger dose discrepancy was observed in the irregular tumor motion case than regular tumor motion case. A larger motion-induced dose error was also observed in the patient case than in the regular tumor motion case. This study analyzed motion-induced dose error as a function of each tumor motion parameters of irregular tumor motion during helical tomotherapy. The analysis showed that variability control of irregular tumor motion is important. We believe that the variability of irregular tumor motion can be reduced by using abdominal compression and respiratory training.

• Journal of Radiation Protection and Research
• /
• v.23 no.3
• /
• pp.123-138
• /
• 1998

Characteristics of element responses of Panasonic UD802 personnel dosimeters in the X, ${\beta}$, ${\gamma}$, ${\gamma}/X$, ${\gamma}/{\beta}$ and ${\gamma}$/neutron mixed fields were assessed. A dose-response algorithm has been developed to decide the high probability of a radiation type and energy by using the distribution in all six ratios of the multi-element TLD. To calculate the 4-element response factors and ratios between the elements of the Panasonic TLDs in the X, $\beta$, and $\gamma$ radiation fields, Panasonic’s UD802 TLDs were irradiated with KINS’s reference irradiation facility. In the photon radiation field, this study confirms that element-3 (E3) and element-4 (E4) of the Panasonic TLDs show energy dependent both in low- and intermediate-energy range, while element-1 (E1) and element-2 (E2) show little energy dependency in the entire whole range. The algorithm, which was developed in this study, was applied to the Panasonic personnel dosimetry system with UD716AGL reader and UD802 TLDs. Performance tests of the algorithm developed was conducted according to the standards and criteria recommended in the ANSI N13.11. The sum of biases and standard deviations was less than 0.232. The values of biases and standard deviations are distributed within a triangle of a lateral value of 0.3 in the ordinate and abscissa, With the above algorithm, Panasonic TLDs satisfactorily perform optimum dose assessment even under an abnormal response of the TLD elements to the energy imparted. This algorithm can be applied to a more rigorous dose assessment by distinguishing an unexpected dose from the planned dose for the most practical purposes, and is useful in conducting an effective personnel dose control program.