• Asian Pacific Journal of Cancer Prevention
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• v.15 no.20
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• pp.9033-9038
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• 2014

Background: The purpose of this study was to assess the feasibility of deep inspiration breath-hold (DIBH) based volumetric modulated arc therapy (VMAT) for locally advanced left sided breast cancer patients undergoing radical mastectomy. DIBH immobilizes the tumor bed providing dosimetric benefits over free breathing (FB). Materials and Methods: Ten left sided post mastectomy patients were immobilized in a supine position with both the arms lifted above the head on a hemi-body vaclock. Two thermoplastic masks were prepared for each patient, one for normal free breathing and a second made with breath-hold to maintain reproducibility. DIBH CT scans were performed in the prospective mode of the Varian real time position management (RPM) system. The planning target volume (PTV) included the left chest wall and supraclavicular nodes and PTV prescription dose was 5000cGy in 25 fractions. DIBH-3DCRT planning was performed with the single iso-centre technique using a 6MV photon beam and the field-in-field technique. VMAT plans for FB and DIBH contained two partial arcs ($179^{\circ}-300^{\circ}CCW/CW$). Dose volume histograms of PTV and OAR's were analyzed for DIBH-VMAT, FB-VMAT and DIBH-3DCRT. In DIBH mode daily orthogonal ($0^{\circ}$ and $90^{\circ}$) KV images were taken to determine the setup variability and weekly twice CBCT to verify gating threshold level reproducibility. Results: DIBH-VMAT reduced the lung and heart dose compared to FB-VMAT, while maintaining similar PTV coverage. The mean heart $V_{30Gy}$ was $2.3%{\pm}2.7$, $5.1%{\pm}3.2$ and $3.3%{\pm}7.2$ and for left lung $V_{20Gy}$ was $18.57%{\pm}2.9$, $21.7%{\pm}3.9$ and $23.5%{\pm}5.1$ for DIBH-VMAT, FB-VMAT and DIBH-3DCRT respectively. Conclusions: DIBH-VMAT significantly reduced the heart and lung dose for left side chest wall patients compared to FB-VMAT. PTV conformity index, homogeneity index, ipsilateral lung dose and heart dose were better for DIBH-VMAT compared to DIBH-3DCRT. However, contralateral lung and breast volumes exposed to low doses were increased with DIBH-VMAT.

• Progress in Medical Physics
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• v.18 no.4
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• pp.221-225
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• 2007

Monte Carlo calculations were performed to demonstrate the dose modulation with dynamic magnetic fields in phantom. The goal of this study is to obtain the uniform dose distributions at a depth region as a target on the central axis of photon beam under moving transverse magnetic field. We have calculated the depth dose curves for two cases of moving magnetic field along a depth line, constant speed and optimal speed. We introduced step-by-step shift and time factor of the position of the electromagnet as an approximations of continuous moving. The optimal time factors as a function of magnetic field position were calculated by least square methods using depth dose data for static magnetic field. We have verified that the flat depth dose is produced by varying the speed of magnetic field as a function of position as a results of Monte Carlo calculations. For 3 T magnetic field, the dose enhancement was 10.1% in comparison to without magnetic field at the center of the target.

• Korean Journal of Head & Neck Oncology
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• v.21 no.2
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• pp.132-138
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• 2005

Purpose: The purpose of this study was to establish general guidelines for the treatment of patients with early glottic cancer(T1-2N0M0), by assessing the role of primary radiation therapy and by analyzing the tumor-related and treatment-related factors that influence treatment results. We also studied the results of hypofractionated radiation therapy for early glottic cancer. Material and Methods: This retrospective study comprised 48 patients who suffered from early glottic cancer and were treated by primary radiotherapy at Inha University Hospital, between May 1997 and October 2004. T-stage distribution showed 38 patients as T1 and 10 patients as stage T2. Thirty-eight patients underwent hypofractionated radiotherapy using a 6 MY photon beam, a total tumor dose of 63Gy, in 5 weekly fractions of 2.25Gy, with an overall radiation treatment time of 38 days. Ten patients in the T2 stage tolerated a total dose of 63-72 Gy(median 68.4Gy) in 5 weekly fractions of 1.8-2.0Gy, with an overall radiation treatment time of 40-87 days(median 51 days). All patients were followed up for at least 3 years. Univariate and multivariate analyses were performed to identify the prognostic factors affecting the treatment results. Result: The 5-year survival rate was 92% for all patients, 94% for T1 patients and 91% for T2 patients. The local control rate was 93.5% for all patients, 95% for T1 and 92.2% for T2 patients. Three patients suffered a relapse following radiotherapy, and underwent subsequent salvage surgery. We included T-stage, tumor location, total radiation dose, field size and overall radiation treatment time as potential prognostic factors. Only T-stage was found to be statistically significant in the univariate analysis, but in the multivariate analysis, it was not found to be significant. Conclusion: High curative and voice preservation rates were obtained with hypofractionated radiotherapy. Further study with a larger number of patients is needed to determine the prognostic factors affecting treatment results.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.156-166
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• 1995

Total body irradiation (TBI) requires large radiation field and extended source to axis distance (SAD), therefore in needs large size treatment room and it needs compensators which components. Appropriate thickness beam spoiler should be used to raise skin dose. Treatment machine, photon energy, total dose, dose rate, dose fractionation, patient position, shield of normal tissues and organs were known to important parameters for TBI. TBI disturbes regular daily treatment schedule and significantly overloads Radiation on oncology departments and during the treatment session it requires accurate reproduction of radiation field and patient position. We were enable to TBI in small size treatment room and short SAD with parallel opposing lateral fields technique and achieved homogenious whole body dose distribution using pb compensators and controled lung dose by lung shield blocks. Drawing a patient shadow on the wall, we could shortened set up time and possible to accurate reproduction of radiation field and patient position.

• Progress in Medical Physics
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• v.25 no.4
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• pp.288-297
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• 2014

Dynamic conformal arc therapy (DCAT) and flattening-filter-free (FFF) beams are commonly adopted for efficient conformal dose delivery in stereotactic body radiation therapy (SBRT). Off-axis geometry (OAG) may be necessary to obtain full gantry rotation without collision, which has been shown to be beneficial for peripheral targets using flattened beams. In this study dose distributions in OAG using FFF were evaluated and the effect of mechanical rotation induced uncertainty was investigated. For the lateral target, OAG evaluation, sphere targets (2, 4, and 6 cm diameter) were placed at three locations (central axis, 3 cm off-axis, and 6 cm off-axis) in a representative patient CT set. For each target, DCAT plans under the same objective were obtained for 6X, 6FFF, 10X, and 10FFF. The parameters used to evaluate the quality of the plans were homogeneity index (HI), conformality indices (CI), and beam on time (BOT). Next, the mechanical rotation induced uncertainty was evaluated using five SBRT patient plans that were randomly selected from a group of patients with laterally located tumors. For each of the five cases, a plan was generated using OAG and CAG with the same prescription and coverage. Each was replanned to account for one degree collimator/couch rotation errors during delivery. Prescription isodose coverage, CI, and lung dose were evaluated. HI and CI values for the lateral target, OAG evaluation were similar for flattened and unflattened beams; however, 6FFF provided slightly better values than 10FFF in OAG. For all plans the HI and CI were acceptable with the maximum difference between flattened and unflattend beams being 0.1. FFF beams showed better conformality than flattened beams for low doses and small targets. Variation due to rotational error for isodose coverage, CI, and lung dose was generally smaller for CAG compared to OAG, with some of these comparisons reaching statistical significance. However, the variations in dose distributions for either treatment technique were small and may not be clinically significant. FFF beams showed acceptable dose distributions in OAG. Although 10FFF provides more dramatic BOT reduction, it generally provides less favorable dosimetric indices compared to 6FFF in OAG. Mechanical uncertainty in collimator and couch rotation had an increased effect for OAG compared to CAG; however, the variations in dose distributions for either treatment technique were minimal.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.8-14
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• 2009

In a laser-plasma wakefield accelerator, the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal wave or plasma bubble in a way similar to the excitation of a wake wave behind a boat as it propagates on the water surface. Electric fields inside the plasma bubble can be several orders of magnitude higher than those available in conventional RF-based particle accelerator facilities which are limited by material breakdown. Therefore, if an electron bunch is properly phase-locked with the bubble's acceleration field, it can gain relativistic energies within an extremely short distance. Here, in the bubble regime we show the generation of stable and reproducible sub GeV, and GeV-class electron beams. Supported by three-dimensional particle-in-cell simulations, our experimental results show the highest acceleration gradients produced so far. Simulations suggested that the plasma bubble elongation should be minimized in order to achieve higher electron beam energies.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.613-620
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• 2017

Planning dose must be delivered accurately for radiation therapy. Also, It must be needed accurately setup. However, patient positioning images were need for accuracy setup. Then patient positioning images is followed by additional exposure to radiation. For 45 points in the phantom, we measured the doses for 6 MV and 10 MV photon beams, OBI(On Board Imager) and CBCT(Conebeam Computed Tomography) using OSLD(Optically Stimulated Luminescent Dosimeter). We compared the differences in the cases where posture confirmation imaging at each point was added to the treatment dose. Also, we tried to propose a photography cycle that satisfies the 5% recommended by AAPM(The American Association of Physicists in Medicine). As a result, a maximum of 98.6 cGy was obtained at a minimum of 45.27 cGy at the 6 MV, a maximum of 99.66 cGy at a minimum of 53.34 cGy at the 10 MV, a maximum of 2.64 cGy at the minimum of 0.19 cGy for the OBI and a maximum of 17.18 cGy at the minimum of 0.54 cGy for the CBCT.The ratio of the radiation dose to the treatment dose is 3.49% in the case of 2D imaging and the maximum is 22.65% in the case of 3D imaging. Therefore, tolerance of 2D image is 1 exposure per day, and 3D image is 1 exposure per week. And it is need to calculation of separate in the parallelism at additional study.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.479-485
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• 2022

At the Korea Institute of Radiological and Medical Sciences, physical human phantoms were developed to evaluate various radiation protection quantities, based on the mesh-type reference computational phantoms of the International Commission on Radiological Protection. The physical human phantoms were fabricated such that a radiophotoluminescent glass dosimeter (RPLGD) with a Tin filter, namely GD-352M, could be inserted into them. A Tin filter is used to eliminate the overestimated signals in low-energy photons below 100 keV. The measurement uncertainty of the RPLGD reader system based on GD-352M should be analyzed for obtaining reliable protection quantities before using it for practical applications. Generally, the measurement uncertainty of RPLGD systems without Tin filters is analyzed for quality assurance of radiotherapy units using a high-energy photon beam. However, in this study, the measurement uncertainty of GD-352M was analyzed for evaluating the protection quantities. The measurement uncertainty factors in the RPLGD include the reference irradiation, regression curve, reproducibility, uniformity, energy dependence, and angular dependence, as described by the International Organization for Standardization (ISO). These factors were calculated using the Guide to the Expression of Uncertainty in Measurement method, applying ISO/ASTM standards 51261(2013), 51707(2015), and SS-ISO 22127(2019). The measurement uncertainties of the RPLGD reader system with a coverage factor of k = 2 were calculated to be 9.26% from 0.005 to 1 Gy and 8.16% from 1 to 10 Gy. A blind test was conducted to validate the RPLGD reader system, which demonstrated that the readout doses included blind doses of 0.1, 1, 2, and 5 Gy. Overall, the E_n values were considered satisfactory.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.1
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• pp.7-16
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• 2016

Purpose : This study aimed to compare and evaluate between the efficiency of two respective devices, 3D-bolus and step-bolus when the devices were used for the treatment of patients whose chest walls were required to undergo the electron beam therapy after the surgical procedure of modified radical mastectomy, MRM. Materials and Methods : The treatment plan of reverse hockey stick method, using the photon beam and electron beam, had been set for six breast cancer patients and these 6 breast cancer patients were selected to be the subjects for this study. The prescribed dose of electron beam for anterior chest wall was set to be 180 cGy per treatment and both the 3D-bolus, produced using 3D printer(CubeX, 3D systems, USA) and the self-made conventional step-bolus were used respectively. The surface dose under 3D-bolus and step-bolus was measured at 5 measurement spots of iso-center, lateral, medial, superior and inferior point, using GAFCHROMIC EBT3 film (International specialty products, USA) and the measured value of dose at 5 spots was compared and analyzed. Also the respective treatment plan was devised, considering the adoption of 3D-bolus and stepbolus and the separate treatment results were compared to each other. Results : The average surface dose was 179.17 cGy when the device of 3D-bolus was adopted and 172.02 cGy when step-bolus was adopted. The average error rate against the prescribed dose of 180 cGy was -(minus) 0.47% when the device of 3D-bolus was adopted and it was -(minus) 4.43% when step-bolus was adopted. It was turned out that the maximum error rate at the point of iso-center was 2.69%, in case of 3D-bolus adoption and it was 5,54% in case of step-bolus adoption. The maximum discrepancy in terms of treatment accuracy was revealed to be about 6% when step-bolus was adopted and to be about 3% when 3D-bolus was adopted. The difference in average target dose on chest wall between 3D-bolus treatment plan and step-bolus treatment plan was shown to be insignificant as the difference was only 0.3%. However, to mention the average prescribed dose for the part of lung and heart, that of 3D-bolus was decreased by 11% for lung and by 8% for heart, compared to that of step-bolus. Conclusion : It was confirmed through this research that the dose uniformity could be improved better through the device of 3D-bolus than through the device of step-bolus, as the device of 3D-bolus, produced in consideration of the contact condition of skin surface of chest wall, could be attached to patients' skin more nicely and the thickness of chest wall can be guaranteed more accurately by the device of 3D-bolus. It is considered that 3D-bolus device can be highly appreciated clinically because 3D-bolus reduces the dose on the adjacent organs and make the normal tissues protected, while that gives no reduction of dose on chest wall.

• Progress in Medical Physics
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• v.21 no.1
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• pp.86-92
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• 2010

The purpose of this study was to measure curvature contour skin dose using radiochromic film and TLD for a conventional open field. We also attempted to quantify the degradation of skin sparing associated with use of immobilization devices for high energy photon beams and to calculate the skin dose with a help of Monte Carlo (MC) simulation. To simulate head-and-neck and shoulder treatment, a cylindrical solid water phantom 11 cm in diameter was irradiated with 6 MV x-rays using $40{\times}40\;cm^2$ field at 100 cm source axis distance (SAD) to the center of the phantom. Aquaplastic mesh mask was placed on the surface of the cylindrical phantom that mimicked relevant clinical situations. The skin dose profile was obtained by taking measurements from $0^{\circ}$ to $360^{\circ}$ around the circumference of the cylindrical phantom. The skin doses obtained from radiochromic film were found to be 47% of the maximum dose of $D_{max}$ at the $0^{\circ}$ beam entry position and 61% at the $90^{\circ}$ oblique beam position without the mask. Using the mask (1.5 mm), the skin dose received was 59% at $0^{\circ}$ incidence and 78% at $80^{\circ}$ incidence. Skin dose results were also gathered using thin thermoluminescent dosimeters (TLD). With the mask, the skin dose was 66% at $0^{\circ}$ incidence and 80% at $80^{\circ}$ incidence. This method with the mask revealed the similar pattern as film measurement. For the treatments of the head-and-neck and shoulder regions in which immobilization mask was used, skin doses at around tangential angle were nearly the same as the prescription dose. When a sloping skin contour is encountered, skin doses may be abated using thinner and more perforated immoblization devices which should still maintain immoblization.