Original Article 2012-12-25 2012-12-25 0 422 477

방사선치료분야에서 의학물리사의 적정인력 분석

Study on Staffing of Medical Physicist in the Field of Radiation Therapy

황의중*ㆍ임영경^†ㆍ김동욱^‡ㆍ신동오^§ㆍ김성규^∥ㆍ정해조^¶ㆍ지영훈^¶

Ui-Jung Hwang*, Young Gyung Lim, Dong Wook Kim, Dong Oh Shin, Sung Kyu Kim, Haijo Jung, Young Hoon Ji

Abstract

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Recently, an adequate number of qualified medical physicist is needed for achieving effective treatment and securing safety to the patient, staff and the public on the course of radiation therapy, since the equipment and the technique of radiation therapy are being developed fast and becoming complex. The studies on medical physics staffing level in United State and European countries were investigated. These results were applied to the domestic situation in order to anticipate indirectly the adequate number of medical physicist in Korea. The current number of medical physicists of 6 (middle to large sized) hospitals in Korea was less than 50% of number recommended in the study. Further detailed research specified on the domestic situation is needed in order to expect adequate number of medical physicist more accurately, and particle beam therapy has to be also considered in the research since the facility site is increasing gradually.

Original Article 2012-12-25 2012-12-25 0 375 209

유방암의 접선 세기조절 방사선치료 선량 특성 분석

Analysis on the Dosimetric Characteristics of Tangential Breast Intensity Modulated Radiotherapy

윤미선ㆍ김용협ㆍ정재욱ㆍ남택근ㆍ안성자ㆍ정웅기ㆍ송주영

Mee Sun Yoon, Yong-Hyeob Kim, Jae-Uk Jeong, Taek-Keun Nam, Sung-Ja Ahn, Wong-Ki Chung, Ju-Young Song

Abstract

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The tangential breast intensity modulated radiotherapy (T-B IMRT) technique, which uses the same tangential fields as conventional 3-dimensional conformal radiotherapy (3D-CRT) plans with physical wedges, was analyzed in terms of the calculated dose distribution feature and dosimetric accuracy of beam delivery during treatment. T-B IMRT plans were prepared for 15 patients with breast cancer who were already treated with conventional 3D-CRT. The homogeneity of the dose distribution to the target volume was improved, and the dose delivered to the normal tissues and critical organs was reduced compared with that in 3D-CRT plans. Quality assurance (QA) plans with the appropriate phantoms were used to analyze the dosimetric accuracy of T-B IMRT. An ionization chamber placed at the hole of an acrylic cylindrical phantom was used for the point dose measurement, and the mean error from the calculated dose was 0.7±1.4%. The accuracy of the dose distribution was verified with a 2D diode detector array, and the mean pass rate calculated from the gamma evaluation was 97.3±2.9%. We confirmed the advantages of a T-B IMRT in the dose distribution and verified the dosimetric accuracy from the QA performance which should still be regarded as an important process even in the simple technique as T-B IMRT in order to maintain a good quality.

Original Article 2012-12-25 2012-12-25 0 364 151

의료용 선형가속기 출력측정용 듀얼윈도우 팬텀 개발

Development of Dual-Window Phantom for Output Measurement of Medical Linacs

정동혁ㆍ곽동원ㆍ문영민ㆍ강영록ㆍ김정기ㆍ이만우

Dong Hyeok Jeong, Dong Won Kwak, Young Min Moon, Yeong-Rok Kang, Jeung Kee Kim, Man Woo Lee

Abstract

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A small water phantom (dual-window phantom) was developed to improve the output measurement efficiency of medical linacs. This phantom is suitable for determining the quality index and output dose for high-energy photon beams. The phantom has two opposite windows and two independently rotating axes. The two axes measure the tissue phantom ratio (TPR) and the percentage depth dose (PDD) simply without requiring chamber movement by rotating the phantom around its axis. High-energy photon beams from a Co-60 irradiator and a medical linac were used to evaluate the phantom. The measured quality index is in good agreement with the reference values; the measured and reference values are within 0.2% of each other for the Co-60 gamma rays and within 1.4% for 6 and 10 MV X-rays. This phantom is more practical for routine output measurements, resulting in the prevention of potential human errors.

Original Article 2012-12-25 2012-12-25 0 429 257

Evaluation of the Radiochromic Film Dosimetry for a Small Curved Interface

휘어진 경계에서의 좁은 영역에 대한 Radiochromic 필름 도시메트리 평가
한림대학교 의과대학 방사선종양학교실

Sei-Kwon Kang, Soah Park, Taejin Hwang, Kwang-Ho Cheong, Taejin Han, Haeyoung Kim, Me-Yeon Lee, Kyoung Ju Kim, Hoonsik Bae

Abstract

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A tumor on the eyelid is often treated using a high-energy electron beam, with a metallic eye shield inserted between the eyelid and the eyeball to preserve the patient's sight. Pretreatment quality assurance of the inner eyelid dose on the metallic shield requires a very small dosimetry tool. For enhanced accuracy, a flexible device fitting the curved interface between the eyelid and the shield is also required. The radiochromic film is the best candidate for this device. To measure the doses along the curved interface and small area, a 3-mm-wide strip of EBT2 film was inserted between the phantom eyelid and the shield. After irradiation with 6 MeV electron beams, the film was evaluated for the dose profile. An acrylic eye shield of the same size as the real eye shield was machined, and CT images free from metal artifacts were obtained. Monte Carlo simulation was performed on the CT images, taking into account eye shield material, such as tungsten, aluminum, and steel. The film-based interface dose distribution agreed with the MC calculation within 2.1%. In the small (millimeter scale) and curved region, radiochromic film dosimetry promises a satisfactory result with easy handling.

Original Article 2012-12-25 2012-12-25 0 359 627

의료용 로봇 원격 응용을 위한 영상처리 시스템 개발

The Development of Image Processing System for Medical Robot Remote Application

김주영*ㆍ김중혁*ㆍ김정채*ㆍ김기덕^†ㆍ유선국*

Joo Young Kim*, Joong Hyuk Kim*, Jung Chae Kim*, Kee Deog Kim, Sun K. Yoo*

Abstract

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In this paper, web-base image processing system has been implemented for remote-controlled medical robot applications. The developed software system was hierarchically composed of diverse image processing and remote operation modules, and the hierarchical composition was satisfied the expandability to higher level application and the accessibility over the web. It can also support diverse file formats including DICOM, VRML, and CAD(STL) to display, transmit, store and share the processed images depending on application environment. Message-based data exchange, object-oriented module and open-source based software configuration will enable the dynamic combination associated with diverse remote medical application requirements.

Original Article 2012-12-25 2012-12-25 0 341 429

Micro-CT 시스템에서 제한된 조건의 Total Variation (TV) Minimization을 이용한 영상화질 평가

Evaluation of Image Quality in Micro-CT System Using Constrained Total Variation (TV) Minimization

조병두*ㆍ최종화*ㆍ김윤환*ㆍ이경호*ㆍ김대홍*^†ㆍ김희중*^†

Byung-Du Jo*, Jong-Hwa Choi*, Yun-Hwan Kim*, Kyung-Ho Lee*, Dae-Hong Kim*, Hee-Joung Kim*

Abstract

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The reduction of radiation dose from x-ray is a main concern in computed tomography (CT) imaging due to the side-effect of the dose on human body. Recently, the various methods for dose reduction have been studied in CT and one of the method is a iterative reconstruction based on total variation (TV) minimization at few-views data. In this paper, we evaluated the image quality between total variation (TV) minimization algorithm and Feldkam-Davis-kress (FDK) algorithm in micro computed tomography (CT). To evaluate the effect of TV minimization algorithm, we produced a cylindrical phantom including contrast media, water, air inserts. We can acquire maximum 400 projection views per rotation of the x-ray tube and detector. 20, 50, 90, 180 projection data were chosen for evaluating the level of image restoration by TV minimization. The phantom and mouse image reconstructed with FDK algorithm at 400 projection data used as a reference image for comparing with TV minimization and FDK algorithm at few-views. Contrast-to-noise ratio (CNR), Universal quality index (UQI) were used as a image evaluation metric. When projection data are not insufficient, our results show that the image quality of reconstructed with TV minimization is similar to reconstructed image with FDK at 400 view. In the cylindrical phantom study, the CNR of TV image was 5.86, FDK image was 5.65 and FDK-reference was 5.98 at 90-views. The CNR of TV image 0.21 higher than FDK image CNR at 90-views. UQI of TV image was 0.99 and FDK image was 0.81 at 90-views. where, the number of projection is 90, the UQI of TV image 0.18 higher than FDK image at 90-views. In the mouse study UQI of TV image was 0.91, FDK was 0.83 at 90-views. the UQI of TV image 0.08 higher than FDK image at 90-views. In cylindrical phantom image and mouse image study, TV minimization algorithm shows the best performance in artifact reduction and preserving edges at few view data. Therefore, TV minimization can potentially be expected to reduce patient dose in clinics.

Original Article 2012-12-25 2012-12-25 0 322 373

디지털 유방촬영기기와 3차원 디지털 유방단층영상합성기기의 비교연구

Comparison of Digital Mammography and Digital Breast Tomosynthesis

김예슬*^†ㆍ박혜숙*^†ㆍ최재구^‡ㆍ최영욱^‡ㆍ박준호^§ㆍ이재준^§ㆍ곽수빈*^†ㆍ김은혜*^†ㆍ김주연*^† 정현정*^†ㆍ이행화*^†ㆍ배규원*^†ㆍ이미영*^†ㆍ김희중*^†

Ye-seul Kim*, Hye-Suk Park*, Jae-Gu Choi, Young-Wook Choi, Jun-Ho Park, Jae-Jun Lee, Su-bin Kwak*, Eun-hye Kim*, Ju-Yeon Kim*, Hyun-Jung Jung*, Haeng-hwa Lee*, Gyu-won Bae*Mi-young Lee*, Hee-Joung Kim*

Abstract

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Breast cancer is the second leading cause of women cancer death in Korea. The key for reducing disease mortality is early detection. Although digital mammography (DM) has been credited as one of the major reasons for the early detection to decrease in breast cancer mortality observed in the last 20 years, DM is far from perfect for several limitations. Digital breast tomosynthesis (DBT) is expected to overcome some inherent limitations of conventional mammography caused by overlapping of normal tissue and pathological tissue during the standard 2D projections for the improved lesion margin visibility and early breast cancer detection. In this study, we compared a DM system and DBT system acquired with different thickness of breast phantom. We acquired breast phantom data with same average glandular dose (AGD) from 1 mGy to 4 mGy under same experimental condition. The contrast, micro-calcification measurement accuracy and observer study were conducted with breast phantom images. As a result, the higher accuracy of lesion detection with DBT system compared to DM system was demonstrated in this study. Furthermore, the pain of patients caused by severe compression can be reduced with DBT system. In conclusion, the results indicated that DBT system play an important role in breast cancer detection.

Original Article 2012-12-25 2012-12-25 0 687 268

두경부암 방사선치료 시 선량 균일도 향상을 위한 Thermoplastic 구강 보상체의 개발

Development of a Thermoplastic Oral Compensator for Improving Dose Uniformity in Radiation Therapy for Head and Neck Cancer

최준용*^†‡ㆍ원영진^§ㆍ박지연*^†ㆍ김종원*^†∥ㆍ문봉기^§ㆍ윤형근^‡ㆍ문수호^‡ㆍ전종병^‡ㆍ서태석*^†

Joon-Yong Choi*, Young-Jin Won, Ji-Yeon Park*, Jong-Won Kim*, Bong-Ki Moon, Hyong-Geun Yoon, Soo-Ho Moon, Jong-Byeong Jeon, Tae-Suk Suh*

Abstract

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Aquaplast Thermoplastic (AT) is a tissue-equivalent oral compensator that has been developed to improve dose uniformity at the common boundary and around the treated area during radiotherapy in patients with head and neck cancer. In order to assess the usefulness of AT, the degree of improvement in dose distribution and physical properties were compared to those of oral compensators made using paraffin, alginate, and putty, which are materials conventionally used in dental imprinting. To assess the physical properties, strength evaluations (compression and drop evaluations) and natural deformation evaluations (volume change over time) were performed; a Gafchromic EBT2 film and a glass dosimeter inserted into a developed phantom for dose verification were used to measure the common boundary dose and the beam profile to assess the dose delivery. When the natural deformation of the oral compensators was assessed over a two-month period, alginate exhibited a maximum of 80% change in volume from moisture evaporation, while the remaining tissue-equivalent properties, including those of AT, showed a change in volume that was less than 3%. In a free-fall test at a height of 1.5 m (repeated 5 times as a strength evaluation), paraffin was easily damaged by the impact, but AT exhibited no damage from the fall. In compressive strength testing, AT was not destroyed even at 8 times the force needed for paraffin. In dose verification using a glass dosimeter, the results showed that in a single test, the tissue-equivalent (about 80 Hounsfield Units [HU]) AT delivered about 4.9% lower surface dose in terms of delivery of an output coefficient (monitor unit), which was 4% lower than putty and exhibited a value of about 1,000 HU or higher during a dose delivery of the same formulation. In addition, when the incident direction of the beam was used as a reference, the uniformity of the dose, as assessed from the beam profile at the boundary after passing through the oral compensators, was 11.41, 3.98, and 4.30 for air, AT, and putty, respectively. The AT oral compensator had a higher strength and lower probability of material transformation than the oral compensators conventionally used as a tissue-equivalent material, and a uniform dose distribution was successfully formed at the boundary and surrounding area including the mouth. It was also possible to deliver a uniformly formulated dose and reduce the skin dose delivery.

Original Article 2012-12-25 2012-12-25 0 399 662

다이오드 검출기를 이용한 초소형 X선관(Miniature X-ray Tube)의 반가층 측정

HVL Measurement of the Miniature X-Ray Tube Using Diode Detector

김주혜*ㆍ안소현*ㆍ오윤진*ㆍ지윤서*ㆍ허장용*ㆍ강창무^†ㆍ서현숙^‡ㆍ이레나^‡

Ju-Hye Kim*, So-Hyeon An*, Yoon-Jin Oh*, Yoon-Seo Ji*, Jang-Yong Huh*, Chang-Mu Kang, Hyunsuk Suh, Rena Lee

Abstract

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The X ray has been widely used in both diagnosis and treatment. Recently, a miniature X ray tube has been developed for radiotherapy. The miniature X ray tube is directly inserted into the body irradiated, so that X rays can be guided to a target at various incident angles according to collimator geometry and, thus, minimize patient dose. If such features of the miniature X ray tube can be applied to development of X ray imaging as well as radiation treatment, it is expected to open a new chapter in the field of diagnostic X ray. However, the miniature X ray tube requires an added filter and a collimator for diagnostic purpose because it was designed for radiotherapy. Therefore, a collimator and an added filter were manufactured for the miniature X ray tube, and mounted on. In this study, we evaluated beam characteristics of the miniature X ray tube for diagnostic X ray system and accuracy of measuring the HVL. We used the Si PIN Photodiode type Piranha detector (Piranha, RTI, Sweden) and estimated the HVL of the miniature X ray tube with added filter and without added filter. Through an another measurement using Al filter, we evaluated the accuracy of the HVL obtained from a direct measurement using the automatic HVL calculation function provided by the Piranha detector. As a result, the HVL of the miniature X ray tube was increased around 1.9 times with the added filter mounted on. So we demonstrated that the HVL was suitable for diagnostic X ray system. In the case that the added filter was not mounted on, the HVL obtained from use of the automatic HVL calculation function provided by Piranha detector was 50% higher than the HVL estimated using Al filter. Therefore, the HVL automatic measurement from the Piranha detector cannot be used for the HVL calculation. However, when the added filter was mounted on, the HVL automatic measurement value using the Piranha detector was approximately 15% lower than the estimated value using Al filter. It implies that the HVL automatic measurement can be used to estimate the HVL of the miniature X ray tube with the added filter mounted on without a more complicated measurement method using Al filter. It is expected that the automatic HVL measurement provided by the Piranha detector enables to make kV-X ray characterization ​​easier.

Original Article 2012-12-25 2012-12-25 0 486 546

기준 베타선장의 에너지 스펙트럼 측정

The Measurement of National Standard Ղ-Rays Energy Spectrum

김철항*^†ㆍ이철영*ㆍ김현문*ㆍ하석호*ㆍ전국진*

Chul-Hang Kim*, Chul-Young Yi*, Hyun-Moon Kim*, Suck-Ho Hah*, Gook-Jin Jeon*

Abstract

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In the present study, we measured the pure beta particle energy spectra of ¹⁴⁷Pm, ⁸⁵Kr, ⁹⁰Sr＋⁹⁰Y radionuclide sources. We confirmed the residual maximum energies of KRISS sources meet the requirement of ISO 6980 and calculated mass collision stopping power ratio, which is essential for absolute measurement of absorbed dose from the reference Ղ-rays. The residual maximum energies of KRISS ¹⁴⁷Pm, ⁸⁵Kr, ⁹⁰Sr＋⁹⁰Y sources are 0.14, 0.57 and 0.93 MeV, respectively and the mass collision stopping power ratios are 1.123, 1.120 and 1.109, respectively.