정위적 방사선뇌수술을 위한 선형가속기의 정확도 확인 및 소조사야의 선량분포 계측에 관한 연구

尹亨根 단국대학교 1995 論文集 Vol.29 No.-

Dosimetric characteristics of 6 MV circular x-ray beams ranging in size from 3 mm to 38 mm were studied. These characteristics included the measurement of CTMR (Calibrated Tissue Maximum Ratio) and beam profiles. Measurements of these parameters were performed in a water equivalent solid phantom using film and ion chamber. CTMR curves represented peak value at 1.5 cm phantom depth and after then showed decreasing tendency with increasing depth. The shape of CTMR curves were very similar to those curves measured in large size x-ray field. On the other hand, be proper adjustment of beam aligning laser and tertiary collimator holder in our Varian Clinac 1800 linear accelerator, we could achieve sufficient accuracy for stereotactic radiosurgery.

피부 T세포 림프 종의 전 피부 전자선 치료

윤형근 단국대학교 1997 論文集 Vol.31 No.-

CTCL (Cutaneous T-Cell Lymphoma) is a T-cell lymphoma that arises in the skin and progresses at highly variable rates and its incidence is very rare in Korea. The most effective treatment is skin directed. TSEBT (total skin electron beam treatment) is one of the most important component of the treatment but is technically very complicated. I treated one patient with CTCL stage IIB (T3NOMO) with TSEBT. I used standard Stanford six-dual field technique. I used electron beam with nominal energy 4 MeV. SSD (source to surface distance) was 390 cm and gantry angles of dual fields were 76° and 104°. The clinical response at the end of the treatment was complete remission. In this paper, I described the pretreatment dosimetric procedures and treatment procedures in detail.

의료용 선형가속기의 일상 점검을 위해 개발한 이온전리함의 특성 연구

윤형근,신교철,김영식 단국대학교 2000 論文集 Vol.35 No.-

The dosimetric system consisting of parallel plate type of air-filled ionization chamber and charge-to-voltage converter was designed to do daily constancy check of the high energy photon beam of Clinac 1800C linear accelerator(Varian Co., Pola Alto, California, USA). The ionization chamber was fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The sensitive volume of the chamber was 1.6cc. High voltage generator was fabricated using the conventional 9V batteries to apply the high voltage(300V) to the electrode of the ionization chamber. Also the charge-to-voltage converter was designed to collect the electrons produced in the ionization chamber cavity. The output reading was converted into the digital signal using the commercially available digital multimeter to produce four-digit readings. The major parameters of the chamber characteristics such as reproducibility. linearity. leakage current. zero drift. timer error. dose-rate effect and polarity effect etc. were measured. These data were comparable to those of the QA-purpose dosimetric system commercially available in the market. Also this dosimetric system can be extended to do the flatness/symmetry check of the photon as well as the constancy check of the various electron beams for the purpose of outputs as well as energy measurements.

Transmission Dose Estimation Algorithm for in vivo Dosimetry

Yun, Hyong-Geun,Huh, Soon-Nyung,Lee, Hyoung-Koo,Woo, Hong-Gyun,Shin, Kyo-Chul,Ha, Sung-Whan The Korean Association for Radiation Protection 2003 방사선방어학회지 Vol.28 No.1

Purpose : Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Materials and Methods : Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with a acrylic phantom for 6 MV and 10 MV X-ray Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 cc Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed for estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. Results : The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ${\pm}0.5%$. For elongated radiation field, the errors were limited to ${\pm}1.0%$. Conclusion : The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.

An 87-year-old patient with repeated oligorecurrences over six years whose disease were treated with radiotherapy alone

Yun, Hyong Geun The Korean Society for Radiation Oncology 2014 Radiation Oncology Journal Vol.32 No.4

In the clinical state of oligometastases or oligorecurrence, a transitional state between localized and widespread systemic disease, local control of the disease may yield improved systemic control. Radiotherapy may be a good means for controlling oligometastatic tumors, particularly in very old patients for whom surgery may be infeasible. A combination of systemic therapy and local therapy is necessary to prevent systemic progression. Some kinds of cancers found in the elderly are known to be somewhat indolent for systemic progression. So, for very old patients who refuse or cannot tolerate chemotherapy, the use of radical radiotherapy alone to treat oligorecurrences may be very helpful. We successfully treated an 87-year-old patient who had been diagnosed with oligorecurrences three times over six years with radiotherapy alone. The patient is now, about four years after his first radiotherapy for liver metastasis, alive without any evidence of cancer and with fully active performance status.

Transmission Dose Estimation algorithm for in vivo Dosimetry

Hyong Geun Yun,Soon Nyung Huh,Hyoung Koo Lee,Hong Gyun Woo,Kyo Chul Shin,Sung Whan Ha 대한방사선방어학회 2003 방사선방어학회지 Vol.28 No.1

Clinical implication of Interim PET for predicting prognosis in patients with head and neck cancer

( Yun Jin Jeong ),( Do Yeun Kim ),( Hyong Geun Yun ),( Yun Sung Lim ),( Hyun Jung Lee ) 대한내과학회 2015 대한내과학회 추계학술대회 Vol.2015 No.1

Background: In the treatment of head and neck squamous cell carcinoma (HNSCC), the number of patients with HNSCC who were treated with radiotherapy has been increased over decades. The prognostic role of pretreatment 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) has been demonstrated in many studies. However, the prognostic and predictive value of interim 18F-FDG PET during radiotherapy is unclear. Objective: We investigated the prognostic value of interim 18 F-FDG PET in patients with HNSCC during radiotherapy. Methods: Patients with HNSCC who underwent radiotherapy with or without chemotherapy were selected. The pretreatment and interim FDG PET scans had been taken. The FGD uptake between pretreatment and interim FDG PET were measured using the maximum standard uptake value (mSUV). Overall survival (OS) and progression free survival (PFS) were analyzed according to the interim mSUV and reduction ratio of mSUV (SRR). Results: A total of 31 patients were include: median age 64 years (range, 33-83), M/F 24/7, Oropharynx/ Nasopharynx/ Hypopharynx 17/7/7, smoker 20 (64.6%), Stage I/II/III/IV 8/3/6/14. The median duration of follow up was 30months (range, 4-82). The median radiation dose was 74 Gy (range, 60.0-79.4). Low interim mSUV (mSUV0.61) had superior treatment outcome compared to patients with low SRR in 2YOSR (90%, 70.7%, respectively; p=0.188) and 2YPFSR (84.6%, 60.0%, respectively; p=0.260). Conclusions: SRR and interim mSUV of primary lesion was associated with favorable outcome following radiotherapy. Further validation with large prospective cohort to show the prognostic implication of interim 18F-FDG PET is warranted.

An 87-year-old patient with repeated oligorecurrences over six years whose disease were treated with radiotherapy alone

Hyong Geun Yun,MD,PhD 대한방사선종양학회 2014 Radiation Oncology Journal Vol.32 No.4

In the clinical state of oligometastases or oligorecurrence, a transitional state between localized and widespread systemic disease, local control of the disease may yield improved systemic control. Radiotherapy may be a good means for controlling oligometastatic tumors, particularly in very old patients for whom surgery may be infeasible. A combination of systemic therapy and local therapy is necessary to prevent systemic progression. Some kinds of cancers found in the elderly are known to be somewhat indolent for systemic progression. So, for very old patients who refuse or cannot tolerate chemotherapy, the use of radical radiotherapy alone to treat oligorecurrences may be very helpful. We successfully treated an 87-year-old patient who had been diagnosed with oligorecurrences three times over six years with radiotherapy alone. The patient is now, about four years after his first radiotherapy for liver metastasis, alive without any evidence of cancer and with fully active performance status.

4년간 17 전이부위에 방사선치료를 받은 위암 환자의 증례보고

윤형근(Hyong Geun Yun) 대한방사선종양학회 2011 Radiation Oncology Journal Vol.29 No.2

5년 반 전 처음 위암 발견 당시 45세였던 여자 환자로 처음부터 원격전이가 있었던 상태였으며 위절제술과 전이부위 절제를 포함한 수술과 항암제치료를 받았다. 그 후 4년 2개월 전부터 여러 차례 새로운 원격전이가 나타날 때마다 간헐적인 경구용 TS-1 항암제 치료와 함께 방사선치료를 시행 받았다. 방사선치료는 4년여에 걸쳐서 8차 시행하였으며 총 시행부위 수는 17 부위였다. 환자의 방사선치료 부위들 중에 근치적 방사선량의 치료를 받은 부위들은 그 뒤 수년의 시간이 흘러도 해당 부위의 국소조절 상태가 유지되었다. 환자는 현재 51세로 일상생활에는 별 지장이 없는 상태이다. Five and half years ago, a 45-year-old female metastatic gastric cancer patient underwent a metastatectomy and chemotherapy. Over the last 4 years and 2 months, she received radiotherapy for every new distant metastasis with intermittent TS-1 oral chemotherapy. She received 8 courses of radiotherapy at 17 metastatic sites for more than 4 years. Metastatic sites which received a curative radiation dose achieved and maintained local control. The patient is now 51 years of age and lives without difficulty in performing her daily activities.

부정형 방사선 조사면에 대한 투과선량 보정 알고리즘

윤형근(Hyong Geun Yun),지의규(Eui Kyu Chie),허순녕(Soon Nyung Huh),우홍균(Hyoung Koo Lee),이형구(Hong Gyun Wu),신교철(Kyo Chul Shin),김시용(Siyong Kim),하성환(Sung Whan Ha) 대한방사선종양학회 2002 Radiation Oncology Journal Vol.20 No.3

목적 : 방사선치료시 환자에 조사되는 방사선량을 매 치료시마다 간편하게 확인하기 위한 생체내(in vivo) 선량측정의 한 방법으로 투과선량을 이용하는 새로운 시스템에 필요한 알고리즘을 이미 개발한 바 있다. 본 연구에서는 조사면 일부가 차폐된 부정형 조사면에서 적용하기 위한 보정 알고리즘을 개발하고자 하였다. 재료 및 방법 : 알고리즘을 개발하기 위한 기본 자료를 마련하기 위하여 투과선량 측정을 시행하였다. 측정에는 선형가속기의 6 MV 및 10 MV의 X선을 이용하였고, 이온함형 측정기 및 전위계를 사용하였다. 측정조건으로는 조사면의 크기(collimator opening)는 2 x 2c㎡에서 32 x 32c㎡까지 한 변을 2 cm씩 증가시켜 16단계로 하였고, 팬톰 두께(phantom thickness Tp)는 0, 10, 20 및 30 cm, 팬톰과 측정기간의 거리(phantom chamber distance PCD)는 10, 30 및 50 cm으로 하였다. 이 때 조사면의 일부를 차폐하였으며 차폐되지 않은 유효조사면(effective field size)의 크기를 5 x 5,10 x 10,15 x 15 및 20 x 20c㎡으로 하였다. 결과 : 조사면의 일부가 차폐체에 의하여 차폐된 경우 종양선량이 감소되며 동시에 투과선량도 감소된다는 물리학적인 추론을 이용하여 방사선조사면 일부 차폐가 투과선량에 미치는 영향을 보정하기 위한 알고리즘을 개발하였으며 조사면 일부가 차폐된 여러 측정 조건에서 알고리즘을 이용한 계산치와 실제측정치 간의 오차는 ±1.0% 이내이었다. 결론 : 투과선량 계산 알고리즘은 조사면 일부가 차폐된 불규칙 조사면의 경우 {pm}1.0% 이하의 오차 범위로 정확히 투과선량을 계산할 수 있음을 확인하였다. Purpose : Measurement of transmission dose is useful for in vivo dosimetry. In this study, the algorithm for estimating the transmission dose for open radiation fields was modified for application to partially blocked radiation fields. Materials and Methods : The beam data was measured with a flat solid phantom with various blocked fields. A new correction algorithm for partially blocked radiation field was developed from the measured data. This algorithm was tested in some settings simulating clinical treatment with an irregular field shape. Results : The correction algorithm for the beam block could accurately reflect the effect of the beam block, with an error within ±1.0%, with both square fields and irregularly shaped fields. Conclusion : This algorithm can accurately estimate the transmission dose in most radiation treatment settings, including irregularly shaped field.