• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.2
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• pp.3-12
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• 2011

Purpose: With increasing medical use of radiation and radioactive isotopes, there is a need to better manage the risk of radiation exposure. This study aims to grasp and analyze the individual radiation exposure situations of radiation-related workers in a medical facility by specific job, in order to instill awareness of radiation danger and to assist in safety and radiation exposure management for such workers. Materials and Methods: From January 1, 2010 December 31, 2010, medical practitioners working in the radiation is classified as a regular personal radiation dosimetry, and subsequently one year 540 people managed investigation department to target workers, dose sectional area, working period, identify the job function-related tasks for a deep dose, respectively, the annual average radiation dose were analyzed. Frequency analysis methods include ANOVA was performed. Results: Medical radiation workers in the department an annual radiation dose of Nuclear and 4.57 mSv a was highest, dose zone-specific distribution of nuclear medicine and in the 5.01~19.05 mSv in the high dose area distribution showed departmental radiation four of the annual radiation dose of Nuclear and 7.14 mSv showed the highest radiation dose. More work an average annual radiation dose according to the job function related to the synthesis of Cyclotron to 17.47 mSv work showed the highest radiation dose, Gamma camera Cinema Room 7.24 mSv, PET/CT Cinema Room service is 7.60 mSv, 2.04 mSv in order of intervention high, were analyzed. Working period, according to domain-specific average annual dose of radiation dose from 10 to 14 in oral and maxillofacial radiology practitioners as high as 1.01~3.00 mSv average dose showed the Department of Radiology, 1-4 years, 5-9 years, respectively, 1.01 workers~8.00 mSv in the range of the most high-dose region showed the distribution, nuclear medicine, and the 1-4 years, 5-9 years 3.01~19.05 mSv, respectively, workers of the highest dose showed the distribution of the area in the range of 10 to 14 years, Workers at 15-19 3.01~15.00 mSv, respectively in the range of the high-dose region were distributed. Conclusion: These results suggest that medical radiation workers working in Nuclear Medicine radiation safety management of the majority of the current were carried out in the effectiveness, depending on job characteristics has been found that many differences. However, this requires efforts to minimize radiation exposure, and systematic training for them and for reasonable radiation exposure management system is needed.

• Progress in Medical Physics
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• v.17 no.2
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• pp.114-122
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• 2006

The two commonly used methods in delivering intensity modulated radiation therapy (IMRT) plan are the dynamic (sliding window) and static (stop and shoot) mode. In this study, the two IMRI delivery techniques are compared by measuring point dose and dose distributions. Using treatment planning system, clinical target volume (CTV) was created as a sphere with various diameter (3 cm, 7 cm, 12 cm). Two IMRT plans were peformed to deliver 200 cGy to the CTV in dynamic and static mode. The two plans were delivered on a phantom and central point dose and dose distributions were measured. The central point dose differences between static and dynamic IMRT delivery were 0.2%, 0.2% and 0.4% when the diameter of CTV was 3 cm, 7 cm, and 12 cm, respectively. The differences In volume receiving 90% of the proscribed dose were 2.7%, 2.2%, and 2.9% for the diameter of CTV was 3 cm, 7 cm, and 12 cm, respectively. For lung cancer patients, the differences in central point dose were 0.2%, 0.2%, and 0.4% when the volume of CTV was 35.5 cc, 296.8 cc, and 903.5 cc, respectively. The differences in volume receiving 90% of the prescribed dose were 2.7%, 4.8%, and 9.1% when the volume of CTV was 35.5 cc, 296.8 cc, and 903.5 cc, respectively. In conclusion, it was possible to deliver IMRT plans using dynamic mode of MLC operation although the loaves are In motion during radiation delivery.

• Radiation Oncology Journal
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• v.18 no.2
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• pp.150-156
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• 2000

Purpose : Stereotactic radiation therapy (SRT) can deliver highly focused radiation to a small and spherical target lesion with very high degree of mechanical accuracy. For non-spherical and large lesions, however, inclusion of the neighboring normal structures within the high dose radiation volume is inevitable in SRT This is to report the beam shaping using the partial closure of the independent jaw in SRT and the verification of dose calculation and the dose display using a home-made soft ware. Materials and Methods : Authors adopted the idea to partially close one or more independent collimator jaw(5) in addition to the circular collimator cones to shield the neighboring normal structures while keeping the target lesion within the radiation beam field at all angles along the arc trajectory. The output factors (OF's) and the tissue-maximum ratios (TMR's) were measured using the micro ion chamber in the water phantom dosimetry system, and were compared with the theoretical calculations. A film dosimetry procedure was peformed to obtain the depth dose profiles at 5 cm, and they were also compared with the theoretical calculations, where the radiation dose would depend on the actual area of irradiation. Authors incorporated this algorithm into the home-made SRT software for the isodose calculation and display, and was tried on an example case with single brain metastasis. The dose-volume histograms (DVH's) of the planning target volume (PTV) and the normal brain derived by the control plan were reciprocally compared with those derived by the plan using the same arc arrangement plus the independent collimator jaw closure. Results : When using 5.0 cm diameter collimator, the measurements of the OF's and the TMR's with one independent jaw set at 30 mm (unblocked), 15.5 mm, 8.6 mm, and 0 mm from th central beam axis showed good correlation to the theoretical calculation within 0.5% and 0.3% error range. The dose profiles at 5 cm depth obtained by the film dosimetry also showed very good correlation to the theoretical calculations. The isodose profiles obtained on the home-made software demonstrated a slightly more conformal dose distribution around the target lesion by using the independent jaw closure, where the DVH's of the PTV were almost equivalent on the two plans, while the DVH's for the normal brain showed that less volume of the normal brain receiving high radiation dose by using this modification than the control plan employing the circular collimator cone only. Conclusions : With the beam shaping modification using the independent jaw closure, authors have realized wider clinical application of SRT with more conformal dose planning. Authors believe that SRT, with beam shaping ideas and efforts, should no longer be limited to the small spherical lesions, but be more widely applied to rather irregularly shaped tumors in the intracranial and the head and neck regions.

• Progress in Medical Physics
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• v.22 no.4
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• pp.178-183
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• 2011

The applicability and feasibility of TomoTherapy in the lung radiation surgery was analyzed by comparison of the calculated dose distribution in TomoTherapy planning with the results of conventional IMRS (intensity modulated radiation surgery) using LINAC (linear accelerator). The acquired CT (computed tomograph) images of total 10 patients whose tumors' motion were less than 5 mm were used in the radiation surgery planning and the same prescribed dose and the same dose constraints were used between TomoTherapy and LINAC. The results of TomoTherapy planning fulfilled the dose requirement in GTV (gross tumor volume) and OAR (organ at risk) in the same with the conventional IMRS using LINAC. TomoTherapy was superior in the view point of low dose in the normal lung tissue and conventional LINAC was superior in the dose homogeneity in GTV. The calculated time for treatment beam delivery was long more than two times in TomoTherapy compared with the conventional LINAC. Based on the results in this study, TomoTherapy can be evaluated as an effective way of lung radiation surgery for the patients whose tumor motion is little when the optimal planning is produced considering patient's condition and suitability of dose distribution.

• Journal of the Korean Society of Radiology
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• v.11 no.1
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• pp.9-17
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• 2017

A high degree of precision and accuracy in Gamma Knife Radiosurgery(GKRS) is a fundamental requirement for therapeutical success. Elaborate radiation delivery and dose gradients with the steep fall-off of radiation are clinically applied thus necessitating a dedicated Quality Assurance(QA) program in order to guarantee dosimetric and geometric accuracy and reduce all the risk factors that can occur in GKRS. In this study, as a part of QA we verified the accuracy of single-shot dose profiles used in the algorithm of Gamma Knife Perfexion(PFX) treatment planning system employing Variable Ellipsoid Modeling Technique(VEMT). We evaluated the dose distributions of single-shots in a spherical ABC phantom with diameter 160 mm on Gamma Knife PFX. The single-shots were directed to the center of ABC phantom. Collimating configurations of 4, 8, and 16 mm sizes along x, y, and z axes were studied. Gamma Knife PFX treatment planning system being used in GKRS is called Leksell GammaPlan(LGP) ver 10.1.1. From the verification like this, the accuracy of GKRS will be doubled. Then the clinical application must be finally performed based on precision and accuracy of GKRS. Specifically the width at the 50% isodose level, that is, Full-Width-of-Half-Maximum(FWHM) was verified under such conditions that a patient's head is simulated as a sphere with diameter 160mm. All the data about dose profiles along x, y, and z axes predicted through VEMT were excellently consistent with dose profiles from LGP within specifications(${\leq}1mm$ at 50% isodose level) except for a little difference of FWHM and PENUMBRA(isodose level: 20%~80%) along z axis for 4 mm and 8mm collimating configurations. The maximum discrepancy of FWHM was less than 2.3% at all collimating configurations. The maximum discrepancy of PENUMBRA was given for the 8 mm collimator along z axis. The difference of FWHM and PENUMBRA in the dose distributions obtained with VEMT and LGP is too small to give the clinical significance in GKRS. The results of this study are considered as a reference for medical physicists involved in GKRS in the whole world. Therefore we can work to confirm the validity of dose distributions for all collimating configurations determined through the regular preventative maintenance program using the independent verification method VEMT for the results of LGP and clinically assure the perfect treatment for patients of GKRS. Thus the use of VEMT is expected that it will be a part of QA that can verify and operate the system safely.

• Journal of the Korean Society of Radiology
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• v.18 no.6
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• pp.681-690
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• 2024

This study aimed to quantitatively analyze the effect of anode angle on the heel effect and image quality in digital radiography systems. For this purpose, two X-ray devices with anode angles of 12° and 16° (Accuray D6 and INNOVISION-SH) were used to compare the radiation dose distribution and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in thoracic spine images, using a chest phantom under identical imaging conditions. In the radiation dose distribution study, it was observed that the device with a 12° anode angle showed more pronounced dose distribution non-uniformity, with a sharp decrease in dose from the cathode side to the anode side. In contrast, the 16° anode angle device exhibited a more gradual dose decrease and a more uniform distribution than the 12° device. It was confirmed that a smaller anode angle intensified the heel effect, causing the radiation intensity to be distributed unevenly. In the thoracic spine image analysis, it was found that, with an anode angle of 16°, the SNR and CNR improved when the chest phantom was placed in the standard orientation (T12 on the cathode side and T1 on the anode side). This suggests that the anode angle and patient positioning influence the effect of the heel effect on image quality. Compared to the reverse orientation (T1 on the cathode side and T12 on the anode side), the standard orientation provided superior image quality. Based on these findings, it is recommended that, in clinical practice, awareness of the anode angle and accurate differentiation between standard and reverse positioning during thoracic spine imaging with digital radiography systems can enhance image quality and improve diagnostic reliability.

• Progress in Medical Physics
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• v.8 no.2
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• pp.27-34
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• 1997

In radiation therapy, the goal of three dimensional conformal radiation therapy(3DCRT) is to conform the apatial distribution of the prescribed radiation dose to the precise 3D configuration of the tomor, and at the same time, to minimize the dose to the surrounding normal tissues. To optimize treatment volume of tomor, treatment volume will be same tomor volume. Biological considerations need to be incorporated in the intensity modulation optimization process. Planning of intensity modulated treatment can irradiate more 20％ in tomor compare to conventional 3DCRT. In lung cancer and rectal cancer, planning of intensity modulated treatment showed optimizing dose distribution.

• Radiation Oncology Journal
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• v.14 no.2
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• pp.149-158
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• 1996

Purpose : To get an accute steepness of dose gradients at outside the target volume in intracranial lesion and a less limitation of beam selection avoiding the high dose at normal brain tissue, this Photon Knife Radiosurgery System was developed in order to provide the three-dimensional dose distribution through the reconstruction of CT scan and the combined stereotactic trans-multiarc beam mode based on linear accelerator photon beam. Materials and methods : This stereotactic radiosurgery, Photon Knife based on linear accelerator photon beam was provided the non-coplanar multiarc and trans-multiarc irradiations. The stereotactic trans-multiarc beam mode can be obtained from the patient position in decubitus. This study has provided the 3-dimensional isodose curve and anatomical structures with the surface rendering technique. The dose distribution from the combined two trans-multiarcs (2M 2TM) was compared to that of four non-coplanar multiarcs (4M) with same collimator size of 25 mm in a diameter and total gantry movements. Results : In this study, it shows that the dose distributions of stereotactic beam mode are significantly depended on the selected couch and gantry angle in same collimator size. Practical dose distribution of combined stereotactic trans-multiarc beam has shown a more small rim thickness than that of the non-coplanar multiarc beam mode in axial, sagittal and coronal plane in our study. 3-Dimensional dose line displayed with surface rendering of irregular target shape is helpful to determine the target dose and to predict the prognosis in follow-up radiosurgery. Conclusions : 3-Dimensional dose line displayed with surface rendering of irregular target shape is essential in stereotactic radiosurgery. This combined stereotactic trans-multiarc beam has shown a less limitation of the selection couch and gantry beam angles for the target surrounding critical organs. It has shown that the dose distribution of combined trans-multiarc beam greatly depended on the couch and gantry angles. In our experiments, the absorbed dose has been decreased to $27%$ / mm in maximum at the interval of $50\%$ to $80\%$ of isodose line.

• Journal of the Korean Society of Radiology
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• v.7 no.6
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• pp.409-414
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• 2013

In this study, we evaluated to the superiority of treatment techniques on prostate cancer, apply to each other treatment techniques-3D conformal therapy versus IMRT-using dose distribution and dose coverages. Obtained 10 patients CT simulation, divided tumor volume and critical organs. Prescription dose was 80 Gy on tumor volume and Each of plans was set by two different plans. As a result, Dose coverage was superior to IMRT. The IMRT's tumor absorbed dose(100.2%) was close to prescription doses. Normal tissue(bladder, rectal, bowel Lt Rt fumoral head) absorbed dose rate was superior. In other words, the radiation therapy of prostate cancer with intensity modulated radiation therapy was better than conformal radiation therapy on dose.

• 대한방사선방어학회:학술대회논문집
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• 2009.11a
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• pp.50-51
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• 2009