• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3017-3026
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• 2022

The ¹³¹Cs radioisotope with a short half-life time and high average radiation energy can treat the cancer effectively in prostate brachytherapy. The typical ¹³¹Cs production processes have a separation step of the cesium from ¹³¹Ba to obtain a high specific radioactivity. Herein, we suggested a novel ¹³¹Cs separation method based on the Ba²⁺ adsorption of alginate beads. It is necessary to reduce the affinity of alginate beads to cesium ions for a high production yield. The carboxyl group of the alginate beads was replaced by a sulfonate group to reduce the cesium affinity while reinforcing their affinity to barium ions. The modified beads exhibited superior Ba²⁺ adsorption performances to native beads. In the fixed-bed column tests, the saturation time and adsorption capacity could be estimated with the Yoon-Nelson model in various injection flow rates and initial concentrations. In terms of the Cs elution, the modified alginate showed better performance (i.e., an elution over 88%) than the native alginate (i.e., an elution below 10%), indicating that the functional group modification was effective in reducing the affinity to cesium ions. Therefore, the separation of cesium from the barium using the modified alginate is expected to be an additional option to produce ¹³¹Cs.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.172-178
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• 2021

Purpose: This study aimed to develop a deep learning architecture combining two task models to generate synthetic computed tomography (sCT) images from low-tesla magnetic resonance (MR) images to improve metallic marker visibility. Methods: Twenty-three patients with cervical cancer treated with intracavitary radiotherapy (ICR) were retrospectively enrolled, and images were acquired using both a computed tomography (CT) scanner and a low-tesla MR machine. The CT images were aligned to the corresponding MR images using a deformable registration, and the metallic dummy source markers were delineated using threshold-based segmentation followed by manual modification. The deformed CT (dCT), MR, and segmentation mask pairs were used for training and testing. The sCT generation model has a cascaded three-dimensional (3D) U-Net-based architecture that converts MR images to CT images and segments the metallic marker. The performance of the model was evaluated with intensity-based comparison metrics. Results: The proposed model with segmentation loss outperformed the 3D U-Net in terms of errors between the sCT and dCT. The structural similarity score difference was not significant. Conclusions: Our study shows the two-task-based deep learning models for generating the sCT images using low-tesla MR images for 3D ICR. This approach will be useful to the MR-only workflow in high-dose-rate brachytherapy.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1871-1877
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• 2023

The main goal of the coordinated project development of therapeutic radiopharmaceuticals of Y-90 and Re-188 is to exploit advancements in radionuclide production technology. Here, direct and indirect production methods with medium reactor and cyclotron are compared to evaluate derived neutron flux and production yield. First, nano-sized ¹⁸⁶W and ⁸⁹Y specimens are suspended in water in a quartz vial by FLUKA simulation. Then, the solution is irradiated for 4 days under 9E+14 n/cm2/s neutron flux of reactor. Also, a neutron activator including three layers-lead moderator, graphite reflector, and polyethylene absorbent- is simulated and tungsten target is irradiated by 60 MeV protons of cyclotron to generate induced neutrons for ¹⁸⁸W and ⁹⁰Sr production via neutron capture. As the neutron energy reduced, the flux gradually increased towards epithermal range to satisfy (n/2n,γ) reactions. The obtained specific activities at saturation were higher than the reported experimental values because the accumulated epithermal flux and nano-sized specimens influence the outcomes. The beta emitters, which are widely utilized in brachytherapy, appeal an alternative route to locally achieve a rational yield. Therefore, the proposed method via neutron activator may ascertain these broad requirements.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4426-4430
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• 2023

In this article, Exposure Buildup Factor(EBF) and the Energy Absorption Buildup Factor(EABF) have been determined for blood, brain, and muscle using the Monte Carlo method which is represented by MCNP5 codes and compared with geometric progression(G-P) fitting method which is represented by Phy-X/PSD online platform. The novelty of the present work is used an energy source of less than 0.1 MeV to determine buildup factors using MCNP5 and using Phy-X/PSD for some human tissues. thus, the energy range used in this case study was 0.06-3 MeV for penetration depths covered 0.5-3 MFP. Results of MCNP5 and Phy-X/PSD are validated against reference values of water that were reported at ANS-6.4.3. present results of EABFs and EBFs for the previously mentioned human tissues appeared good agreement between MCNP5 in comparison with Phy-X/PSD, whereas, the maximum average relative deviation did not exceed 2.37%. results of our article can be used in different medical applications, such as brachytherapy, radiotherapy, and diagnostics.

• Radiation Oncology Journal
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• 제1권1호
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• pp.95-102
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• 1983

The radical treatment of uterine cervical cancer by interacavitary radium or cesium, in combination with teletherapy are well known. Although the result of such treatment should not give rise to complacency, problem of radiation exposure to medical staff had not been resolved. Fortunately, many attempts have been made to reduce this hazard, most of which take the form of afterloading applicators with a suitably shielded radioisotope. In order to avoid hazardous radiation exposure to staffs concerned with brachytherapy, RALS using high intensity source of Co-60, have been employed at Yonsei Cancer Center since May, 1979. It allows rectal and bladder doses to be kept low, while maintaining a satifactory usual dose distribution of the other type of applicators, and the short treatment time allow four or five patients to be treated per hour. It also removes much patient's discomfort and the difficulties of nursing these patients. Since the first introduction in Korea, over seven hundred cases with various stage of uterine cervical cancer have been treated on a radical basis at this center last 4 years. These authors have strongly attracted attention to the results in terms of local control rate, survival s and morbidity compared with those of conventional low dose rate radiotherapy. Retrospective interim analysis of data was preliminarily accomplished through the labored follow-up study of 340 cases treated during initial 2 years and the radiobiologic standpoint of high dose rate intracavitary irradiation will be discussed.

• 한국의학물리학회지:의학물리
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• 제8권1호
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• pp.37-45
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• 1997

차폐된 질 원주기구를 이용한 강내치료시 Co-60 선원에 대한 정확한 흡수선량을 결정 하고자 선원을 교정하고, 질 원주기구에 의한 선량분포변화를 조사하였다. 선량분포의 변화량은 직경 2.5 cm 차폐된 질 원주기구를 폴리스틸렌 팬톰에 설치하여 전리함으로 측정하였으며, 부채꼴 모양인 0.55cm 두께의 9$0^{\circ}C$ 연으로 차폐된 면과 차폐되지 않은 면의 선량분포에 대한 영향을 상대선량 감소율로 측정하였다. 측정된 선량분포의 변화량을 제작사의 선량분포도 및 다점 분할방식으로 구한 선량율표와 비교하였다. 질 원주기구를 이용한 선량 감소율은 차폐되지 않은 변의 경우 원주기구 표면 1cm 거리에서 4.4%를 보였고, 차폐된 면에서는 원주기구 표면에서 20.4% 를 나타냈다. 9$0^{\circ}C$연 차폐된 질 원주기구의 선량감쇄효율은 Co-60 선원에서 평균 0.2가 되었다. Co-60 이동형 선원의 선량분포는 다 점분할방식의 선량율표와 4.1% 이내로 일치하였다.

• 한국의학물리학회지:의학물리
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• 제6권1호
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• pp.13-18
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• 1995

고선량의 RALS(Remote Afterloding Syetem)를 이용한 근접조사에서 선원의 위치에 따라 선량분포는 거리제곱의 반비례 형태로 변화되므로, 관심점의 흡수선량은 선원의 교정에 의해 크게 영향을 받는다. 자궁경부암 강내치료시 정확한 흡수선량을 결정하고자 선원을 교정하고, 선원의 위치에 따른 선량분포도에 의한 계산값과 반도체 검출기와 전리함을 이용한 설측값과 차이를 비교하고 보정 방법을 논의 하였다. Bulcher-RALS를 이용하여 치료에 사용된 선원의 교정은 공기커마와 사각형 아크랄 팬톰을 이용하여 r 인자에 의한 거리 역자승법칙으로 계산하였고, Co-60 선원의 8cm 거리에서 검교정된 측정기를 이용한 선량율을 비교치로 이용하였다. 선량측정치의 재현성은 팬톰내에서 0.3~1.1% 였으며, 측정치의 분포는 Bulcher-RALS 선량분포도에 의한 계산값과 팬톰측정치의 비교에서 -3~17%, 강내치료를 받은 18 명의 환자를 대상으로한 직장내 흡수선량에서 체내 실측값과 차이는 환자와 선원의 위치에 따라 -6~＋21%로 측정값이 평균 6.3% 높게 나타났다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2279-2285
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• 2014

Background: To evaluate treatment outcomes of patients with stage I-III endometrial cancer treated with postoperative radiation. Materials and Methods: A retrospective review of 166 endometrial cancer patients, undergoing surgery and postoperative radiotherapy at Siriraj Hospital from 2005-2008 was performed. Pathology was reviewed. Results of treatment were reported with 5-year loco-regional recurrence free survival (LRRFS), 5-year overall survival (OS), patterns of failure and toxicity, and according to stage and risk groups. Results: Median follow up time was 62.8 months. Pathological changes were found in 36.3% of the patients after central reviews, leading to 19% changes in risk groups. Most of the patients (83.7%) received pelvic radiation (PRT) and vaginal brachytherapy (VBT). Five-year LRRFS and OS of all patients were 94.9% and 85.5%, respectively. There was no recurrence or death in low and low-intermediate risk groups. For the high-intermediate risk group, 5-year LRRFS and OS were 96.2% and 90.8%, respectively, and for the high risk group 90.5% and 71%. Late grade 3 and 5 gastrointestinal toxicity was found in 3% and 1.2% of patients, respectively. All of them received PRT 5,000 cGy in 25 fractions. Conclusions: Low and intermediate risk patients had good results with surgery and adjuvant radiation therapy. For high risk patients, postoperative radiation therapy alone appeared to be inadequate as the most common pattern of failure was distant metastasis.

• Radiation Oncology Journal
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• 제8권1호
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• pp.133-136
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• 1990

자궁암치료에서 재발되거나 치료가 어려운 종양에 대하여 방사선과 온열요법을 병행함으로서 치료 성과를 다소 향상시킬 수 있었다. 더욱이 방사선 근접조사와 강내온열치료는 주위 건강조직의 피해를 줄이면서 종양에 집중손상을 줄 수 있었으며 강내방사선조사 기구를 공동으로 이용하므로서 시술이 간단하고 치료부위를 정확히 조준할 수 있었다. 그러나 강내조사용 안테나는 그 모양과 구성에 따라 온열 분포가 변하며 재래식 쌍극철심형 안테나는 끝부분 또는 연결부위의 가온이 급증하여 균등한 온열분포를 기대할 수 없었다. 저자들은 안테나의 길이를 마이크로파의 약수 즉 3, 6, 12 cm로 하여 공명이 잘 이루어지도록 하였으며 끝이 굵고 접촉 부위가 가느다란 꼬깔형 (conical) 안테나를 제작하여 사용한 결과 안테나 축에 따라 거의 일정하거나 약간 타원형의 온도분포를 이루었으며 가온 깊이도 $2\~3\;cm$로서 비교적 깊은 곳까지 가열할 수 있어 강내 치료효과를 향상시킬 수 있다고 생각된다.

• Radiation Oncology Journal
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• 제11권1호
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• pp.91-96
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• 1993

From September 1989 to June 1992,22 patients with nasopharyngeal carcinoma were treated in Asan Medical Center with an external beam of 60 Gy followed by a boost dose of 15 Gy HDR brachytherapy. There were 5 females and 17 males with median age of 44 years (range: 20-69 years). All patients were histologically confirmed and staged by physical examination, CT scan and/or MRI. By the AJCC TNM staging system, there were 2 patients with stge II (T2NO), 4 with stage III (T3NO, T1-3N1), and 16 with stage IV (T4 or N2-3). Four patients received chemotherapy with 5-FU and cisplatin prior to radiotherapy. All patients were followed up periodically by a telescopic examination and radiologic imaging study of CT scan or MRI with a median follow-up time of 13 months (range: 3-34 months). Twenty one patients showed a complete response ore month after completing therapy and one patient showed a complete response after three months. At the time of this analysis, seventeen patients remain alive without evidence of disease, but four patients developed distant metastasis and one patient died a month after treatment. The local control rate was $100{\%}$ in a median follow-up time of 13 months. The two year overall and disease free survival rates by the Kaplan-Meier method were $94{\%}$ and $67{\%}$, respectively. Serious radiation sequelae have not been observed yet. Although longer follow-up is needed, this retrospective analysis suggests that HDR brachytherap. given as a boost therapy for nasoharyngeal carcinoma may improve the local control. To reduce the incidence of distant metastasis, we need to develop a more effective systemic chemotherapy.