• Radiation Oncology Journal
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• v.16 no.4
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• pp.517-529
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• 1998

Purpose : Although many studies have investigated the dosimetric aspects of stereotactic radiosurgery in terms of target volume, the absorbed doses at extracranial sites: especially the lens or thyroid - which are sensitive to radiation for deterministic or stochastic effect -have infrequently been reported. The aim of this study is to evaluate what effects the parameters of radiosurgery have on the absorbed doses of the lens and thyroid in patients treated by stereotactic radiosurgery, using a systematic plan in a humanoid phantom. Materials and Methods : Six isocenters were selected and radiosurgery was planned using the stereotactic radiosurgery system which the Department of Therapeutic Radiology at Seoul National University College of Medicine developed. The experimental radiosurgery plan consisted of 6 arc planes per one isocenter, 100 degrees for each arc range and an accessory collimator diameter size of 2 cm. After 250 cGy of irradiation from each arc, the doses absorbed at the lens and thyroid were measured by thermoluminescence dosimetry. Results : The lens dose was 0.23$\pm$0.08$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the lens and was 0.76$\pm$0.12$\%$ of the maximum dose for each isocenter when the exit beam passed through the lens. The thyroid dose was 0.18$\pm$0.05$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the thyroid and was 0.41$\pm$0.04$\%$ of the maximum dose for each isocenter when the exit beam Passed through the thyroid. The passing of the exit beam is the most significant factor of organ dose and the absorbed dose by an arc crossing organ decides 80$\%$ of the total dose. The absorbed doses of the lens and thyroid were larger as the isocenter sites and arc planes were closer to each organ. There were no differences in the doses at the surface and 5 mm depth from the surface in the eyelid and thyroid areas. Conclusion : As the isocenter and arc plane were placed closer to the lens and thyroid, the doses increased. Whether the exit beams passed through the lens or thyroid greatly influenced the lens and thyroid dose. The surface dose of the lens and thyroid consistently represent the tissue dose. Even when the exit beam passes through the lens and thyroid, the doses are less than 1$\%$ of the maximum dose and therefore, are too low to evoke late complications, but nevertheless, we should try to minimize the thyroid dose in children, whenever possible.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.38-46
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• 1977

오늘날 에너지 공급(供給)을 위한 새로운 해결책(解決策)의 하나로서 등장(登場)한 원자력발전소(原子力發電所), 재래(在來)의 X선(線) 진료(診療) 이외(以外)에 의학계(醫學界)에 도입(導入)된 방사선원(放射線源), 그리고 각종(各種) 전자생산품(電子生産品) 등(等)의 증가현상(增加現象)은 방사선(放射線) 방어(防禦) 문제(問題)와 관련(關聯)하여 보건의학분야(保健醫學分野)에서 종사(從事)하는 사람들에게 지대(至大)한 관심(關心)거리가 되고있다. 그래서, 우선(于先) 방사선(放射線)에 관(關)한 사항(事項)중에서 가장 기초(基礎)가되는 방사선량계측(放射線量計測)에 있어서 그 양(量)과 단위(單位) 문제(問題)가 체계적(體系的)으로 서술(敍述)되었다. 즉(卽) 방사선(放射線)이 인체(人體)에 끼칠 수 있는 해(害)로운 영향(影響)에 그 주안점(主眼點)을 두어 조사선량(照射線量), 흡수선량(吸收線量), 선량당량(線量當量), 그리고 그들의 관계(關係) 및 방사능등(放射能等)에 관(關)하여 토론(討論)되었다. 특(特)히 조사선량률(放射線量率), X는 비(比)감마선선상수(線常數), ($\Gamma$)를 포함(包含)하는 함수(函數)로 표현(表現)되었고, 끝으로 인체(人體) 내부(內部)에 축적(蓄積)된 방사능(放射能)으로부터의 영향(影響)에 의(依)한 이른바 생물학적효과(生物學的效果) (Somatic or Genetic Effects)와 관련(關聯)되는 내부흡수선량율(內部吸收線量率)은 평형흡수선량상수(平衡吸收線量常數)($\Delta_i$)와 흡수율($F_i$)를 포함(包含)하는 수학적(數學的) 모델로 소개(紹介)되었다. 한편 방사능(放射能)은 방사선원(放射線源) 물질(物質)의 자연붕괴율(自然崩壞率)이므로 다른 방사선량(放射線量)들 즉(卽) 조사선량(照射線量), 흡수선량(吸收線量)그리고 선량당량(線量當量)과는 별도(別途)로 취급(取扱)하였음을 부언(附言)한다.

• Journal of the Korean Society of Radiology
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• v.12 no.6
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• pp.763-768
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• 2018

Although the development of radiation therapy techniques has made the treatment more precise, exposure by radiation is unavoidable beyond the treatment site. In this study, we wanted to evaluate the absorbed dose according to the thickness of the bolus on the opposite side of the treatment in radiation treatment for breast cancer and to analyze the effect of dose reduction. An experiment was conducted on Rando phantom using VMAT treatment methods. Five points of A, B, C, D, and E were selected for the breast opposite the treatment, and when the dosimeters of 5, 10, 15, and 20 mm were used. The highest absorbed dose at point D closest to the treatment point was measured and lowest at point B furthest from the treatment point. The mean absorbed dose was 8.61 cGy When the bolus is not used and 8.10, 7.94, 8.06, and 8.10 cGy Depending on the thickness of the bolus. In this study, bolus was intended to be used to analyze the dose-reducing effects of breasts on the other side of the treatment. The results of the study showed the effect of dose reduction and the appropriate bolus thickness should be set up to reduce the dose in normal tissues.

• Journal of the Korean Society of Radiology
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• v.7 no.2
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• pp.137-143
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• 2013

This study presents comparison results between axial and spiral scanning in the head and chest region with 64 MDCT to evaluate organ doses in infants and toddlers, who are more radiosensitive to radiation than adults and rise in the number of CT examinations, during CT scanning. Organ doses were significantly lower in spiral scanning than axial scanning regardless of scanned regions. The average organ dose for the chest scan using pitch of 1.355 was found to be significantly higher(average -12.03%) than for the other two pitch settings(0.525 and 0.988) in the spiral scanning mode compared with the axial one. Organ doses in the spiral scanning mode were lower by average 20.54% than the axial scanning mode. The results of the study that evaluated organ doses with an anthropomorphic phantom will help to demonstrate the result values of Monte Carlo simulations and make a contribution to more accurate evaluations of organ doses in toddlers undergoing a CT examination.

• 대한방사선방어학회:학술대회논문집
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• 2009.04a
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• pp.284-285
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• 2009

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.3
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• pp.273-279
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• 2012

Purpose : This study was aimed to calculate effective dose from cone beam CT and compare effective dose from periapical and panoramic radiography for mesiodens. Materials and Methods : Upper anteiror periapical, panoramic radiography and cone-beam CT were taken for diagnosis of mesiodens. The effective dose were calculated by using an anthropomorphic phantom loaded with thermoluminescent dosimeters at the 23 sites related to sensitive organs. Results : The highest absorbed doses were received by the mandibular body, parotid gland and cheek from periapical, panoramic and cone-beam CT, respectively. The effective doses for periapical, panoramic radiography and cone-beam CT measured 2, 18 and 48 ${\mu}Sv$. Conclusion : Cone-beam CT, although providing additional diagnostic benefits, exposes patients to higher levels of radiation than conventional periapical and panoramic radiography.

• 대한방사선방어학회:학술대회논문집
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• 2011.11a
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• pp.282-283
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• 2011

• 대한방사선방어학회:학술대회논문집
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• 2011.04a
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• pp.76-77
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• 2011

• Journal of the Korean Society of Radiology
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• v.5 no.6
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• pp.343-349
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• 2011

This study was aimed to evaluate the absorbed dose in brain of dental radiography. For radiographic exposure, PLD(photoluminescence dosimetry) chips placed in Rando phantom to measurement the absorbed dose to pituitary gland, orbit, maxillary sinus and submandibular glands, thyroid gland, esophagus. Equipments were used Kodak 2200, Kodak 8000C dental radiographic systems and computed tomography(Lightspeed VCT). The absorbed doses were measured at the same exposure parameters and distance by the clinical factor(kV, mA, sec). The result were as follows ; The absorbed dose for intra-oral radiography were 0.02~2.47cGy, the greatest absorbed dose was 2.47cGy for thyroid gland in maxillary right molar projection. the lowest adsorbed dose was 0.02cGy for submandibular glands in lower anterior projection. The absorbed dose for extra-oral radiography were 0.36~3.44cGy of cephalometric method, 0.14~12.82cGy of panoramic method, 8.17~253.63cGy of computed tomography, the greatest adsorbed dose was 253.63cGy for submandibular glands in maxillary CT scan. the lowest adsorbed dose was 0.14cGy for orbit in panoramic method. As a result, extra-oral radiography was measured more than intra-oral radiography. In particular, method which used computed tomography was measured more than 100 times than intra-oral radiography highly. Therefore, you must show a guideline in extra-oral radiography and an effort to reduce absorbed dose is demanded.

• Nuclear Engineering and Technology
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• v.5 no.2
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• pp.87-93
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• 1973

Due to the Co-60 source size, the penumbra in Co-60 teletheraphy poses a serious problem, even if the extended collimators are used, Here an empirical formula for the calculation of integral absorbed dose in the penumbra region was derived. Through a numerical calculation, the penumbra effect on integral absorbed dose was investigated. The longer the source-to-skin distance, the larger the integral absorbed dose of penumbra region, and the larger the source diameter, the larger the integral absorbed dose of penumbra region. It was also found that in some case the integral absorbed dose in penumbra region becomes several times larger than the integral absorbed dose of treatment region itself if the source-to-skin distance becomes greater. Therefore, one must consider the penumbra effect in Co-60 teletherapy.