Sludge settleability detection using automated SV30 measurement and comparisons of feature extraction methods

Changwon Kim,김예진,Hoonsik Yeom,Soojung Choi,Hyeon Bae 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.3

The need for automation and measurement technologies to detect the process state has been a driving force in the development of various measurements at wastewater treatment plants. While the number of applications of automation & measurement technologies to the field is increasing, there have only been a few cases where they have been applied to the area of sludge settling. It is not easy to develop an automated operation support system for the detection of sludge settleability due to its site-specific characteristics. To automate the human operator’s daily test and diagnosis work on sludge settling, an on-line SV30 measurement was developed and an automated detection algorithm on settleability was developed that imitated heuristics to detect settleability faults. The automated SV30 measurement is based on automatic pumping with a predefined schedule, the image capture of the settling test with a digital camera, and an analysis of the images to detect the settled sludge height. To detect settleability faults such as deflocculation and bulking from these images, two feature extraction methods were used and their performance was evaluated.

1)디지털화재구성사진(Digitally Reconstructed Radiograph)을 이용한 정위방사선수술 및 치료의 치료위치 확인

조병철(Byung Chul Cho),오도훈(Do Hoon Oh),배훈식(Hoonsik Bae) 대한방사선종양학회 1999 Radiation Oncology Journal Vol.17 No.1

목 적 : 정위방사선치료에서 디지털화재구성사진(Digitally Reconstructed Radiograph, DRR) 과 조사문사진을 비교함으로써 환자의 치료위치를 직접 확인할 수 있는 방법을 개발하고자 한다. 대상 및 방법 : 분할정위방사선치료를 위해 thermoplastic mask 틀에 고정시킨 1명의 환자를 대상으로 4회 촬영한 전후 방향(AP) 및 측면 방향(lateral)에 대한 조사문사진과 DRR을 비교하였다. 치료위치 setup 후에, 혈관조영용 표적조준기와 같은 fiducial marker가 부착된 표적조준기를 정위수술용 틀에 부착한 후 치료용 원형 콜리메이터의 설치 전과 후에 겹조사 방식으로 촬영하여 전후방향 및 측면 방향의 조사문사진을 얻었다. 병변 및 중요 장기와 fiducial marker의 위치를 합성시킨 DRR 영상을 만들어 조사문사진과 동일한 확대율 및 크기로 투명 필름에 인쇄하여 비교하였다. 이로부터 DRR과 조사문사진상에 표시된 해부학적 구조와 치료중심점의 거리 오차(전체 치료 오차), 해부학적 구조와 fiducial marker간의 오차(환자고정 오차), 그리고 치료중심점과 fiducial marker간의 오차(치료조준 오차)를 각각 구하였다. 결 과 : 치료조준 오차는 각각 1.5±0.3mm(AP), 0.9±0.3mm(lateral) 이었고 , 환자고정 오차는 1.9±0.5mm(AP), 1.9 ±0.4mm(lateral), 그리고 전체 치료 오차는 AP 상에서 1.6±0.9mm, lateral 상에서 1.3±0.4mm 이었다 . 또한 AP 와 lateral 오차로 인해 발생될 수 있는 3차원 공간상의 최대 가능 오차(sqrt{ (Delta AP)^2 + (Delta Lat)^2} )는 치료조준 오차가 1.7±0.4mm, 환자고정 오차가 2.6±0.6mm, 그리고 전체 치료 오차는 2.3±0.7mm로 나타났다. 결 론 : DRR 영상을 재구성하는 프로그램을 개발하였으며, DRR 영상을 조사문사진과 비교함으로써 정위방사선치료에서 직접적인 치료위치 확인이 가능하였다. Purpose : To develop a method for verifying a treatment setup in stereotactic radiotherapy by matching portal images to DRRs. Materials and Methods : Four pairs of orthogonal portal images of one patient immobilized by a thermoplastic mask frame for fractionated stereotactic radiotherapy were compared with DRRs. Portal images are obtained in AP (anterior/posterior) and lateral directions with a target localizer box containing fiducial markers attached to a stereotactic frame. DRRs superimposed over a planned isocenter and fiducial markers are printed out on transparent films. And then, they were overlaid ov er orthogonal portal images by matching anatomical structures. From three different kind of objects (isocenter, fiducial markers, anatomical structure) on DRRs and portal images, the displacement error between anatomical structure and isocenters (overall s etup error), the displacement error between anatomical structure and fiducial markers (immobilization error), and the displacement error between fiducial markers and isocenters (localization error) were measured. R e s u l t s : Localization errors were 1.5±0.3 mm (AP), 0.9±0.3 mm (lateral), and immobilization errors were 1.9±0.5 mm (AP), 1.9±0.4 mm (lateral). In addition, overall setup errors were 1.6±0.9 mm (AP), 1.3±0.4 mm (lateral). From these orthogonal displacement errors, maximum 3D displacement errors(sqrt{ (Delta AP)^2 + (Delta Lat)^2}) were found to be 1.7±0.4 mm for localization, 2.6±0.6 mm for immobilization, and 2.3±0.7mm for overall treatment setup. Conclusion : By comparing orthogonal portal images with DRRs, we find out that it is possible to v erify treatment setup directly in stereotactic radiotherapy.

비 상업용 3차원 치료계획시스템인 Plunc의 임상적용 가능성에 대한 연구

조병철(Byung Chul Cho),오도훈(Do Hoon Oh),배훈식(Hoonsik Bae) 대한방사선종양학회 1998 Radiation Oncology Journal Vol.16 No.1

목 적 : 비 상업용 3차원 컴퓨터치료계획시스템인 Plunc의 구축 사례를 소개하고 이의 임상적용 가능성에 대하여 검증하고자 한다. 대 상 및 방법 : 미국 Nortth Caolina 대학에서 개발된 3차원 치료계획시스템인 Plunc 의 소스코드를 제공받아, PC용 Unix인 Linux 환경의 Pentium Pro 200MHz(128MB RAM, Millennium VGA)에서 설치하였다 . 본과의 6MV 광자선(Siemens MXE 6740)에 대한 출력인자, 최대산란비, 최대산란인자, 쐐기의 모양 및 감쇄인자 등의 빔데이터를 입력한 후, 일반적인 치료조건인 10cm 깊이의 회전중심점에서의 심부선량백분율, 선량측면도, oblique 입사빔 및 공기간격 하에서의 선량계산 결과를 물팬톰에서의 측정치와 비교, 분석하였다. 결 과 : Plunc는 원래 CT 영상데이터를 이용한 모의치료기로써 개발되어, 빔 설계가 매우 편리하도록 사용자 인터페이스가 구성되어 있으며, BEV,DRR 및 영상합성 등의 기능을 갖추고 있다. 선량계산은 10초 정도가 소요되는 3차원 선량분포나 선량체적히스토그람을 제외하고는 거의 실시간으로 실행되었다. 결 론 : Plunc의 광자선량계산의 정밀도는 일반적인 치료조건하에서 약 2-5% 내외의 오차로써, 측정치에 대한 보정에 근거한 알고리즘을 사용하는 일반 치료계획시스템과 비슷한 수준이라 사료된다. 현재로서는 전자선에 대한 선량계산이 불가능하기 때문에 완전한 형태의 치료계획시스템이 되기 위해서는 향후, 전자선에 대한 계산모듈의 개발과 광자선 선량계산 또한 보다 정밀한 선량계산이 가능한 컨벌류션 방법과 같은 3차원 선량계산모듈의 개발도 필요하다. Plunc는 상업용 3차원 치료계획 시스템의 사용이 현실적으로 어려운 여건의 병원에서 2차원 치료계획시스템과 상호 보완적으로 사용한다면 2차원 치료계획시스템이 갖는 많은 제약을 극복할 수 있을 것으로 사료된다. Purpose : The objective of this study is to introduce our installation of a non-commercial 3D planning system, Plunc and confirm it's clinical applicability in various treatment situations. Materials and Methods : We obtained source codes of Plunc, offered by University of North Carolina and installed them on a Pentium Pro 200MHz (128MB RAM, Millenium VGA) with Linux operating system. To examine accuracy of dose distributions calculated by Plunc, we input beam data of 6MV photon of our linear accelerator(Siemens MXE 6740) including tissue- maximum ratio, scatter-maximum ratio, attenuation coefficients and shapes of wedge filters. After then, we compared values of dose distributions(Percent depth dose; PDD, dose profiles with and without wedge filters, oblique incident beam, and dose distributions under air-gap) calculated by Plunc with measured values. Results : Plunc operated in almost real time except spending about 10 seconds in full volume dose distribution and dose-volume histogram(DVH) on the PC described above. As compared with measurements for irradiations of 90-cm SSD and 10-cm depth isocenter, the PDD curves calculated by Plunc did not exceed 1% of inaccuracies except buildup region. For dose profiles with and without wedge filter, the calculated ones are accurate within 2% except low -dose region outside irradiations where Plunc showed 5% of dose reduction. For the oblique incident beam, it showed a good agreement except low dose region below 30 % of isocenter dose. In the case of dose distribution under air-gap, there was 5% errors of the central-axis dose. Conclusion : By comparing photon dose calculations using the Plunc with measurements, we confirmed that Plunc showed acceptable accuracies about 2-5% in typical treatment situations, which was comparable to commercial planning systems using correction-based algorithms. Plunc does not have a function for electron beam planning up to the present. However, it is possible to implement electron dose calculation modules or more accurate photon dose calculation into the Plunc system. Plunc is shown to be useful to clear many limitations of 2D planning systems in clinics where a commercial 3D planning system is not available.

Clinical Implementation of a Virtual-Micro MLC for Smoothing MLC Field Edge

조병철,박희철,배훈식,Cho Byung-Chul,Park Hee-Chul,Bae Hoonsik Korean Society of Medical Physics 2004 의학물리 Vol.15 No.3

지멘스(Siemens)사에서 개발된 가상미세다엽콜리메이터인 HD-270은, 전형적 다엽콜리메이터에 있어 폭의 유한성 때문에 불필요하게 발생하는 조사경계면의 요동현상을 완화시켜준다. 저자들은 이 기법을 사용했을 때의 선량분포의 변화를 확인하고, 치료계획단계에서 이를 평가해 볼 수 있도록 Pinnacle (Philips Radiation Oncology Systems, 미국) 전산화치료계획장치에 구현하였다. 그리고 임상적용에 앞서 선량학적 특성을 파악하기 위해, 가상미세다엽콜리메이터의 해상도, 조사경계면과 다엽콜리메이터가 형성하는 각도가 요동현상 및 유효반음영에 미치는 영향을 평가하였다. 또한 가상미세다엽콜리메이터 구현에 수반되는 치료테이블 움직임에 대한 위치 정확도를 평가하였다. HD-270의 임상적용을 위해 추가적으로 소요되는 치료계획과 치료 시간은 무시할 수 있음을 확인할 수 있었다. A Siemens HD-270 MLC$^{TM}$, a virtual-micro MLC, allows to the application of a smooth field edge method due to the finite leaf-width of MLC. This technique was implemented into a Pinnacle planning system in order to evaluate the dose distributions during the planning stage. The necessary dosimetric aspects, such as undulation and effective penumbra, were investigated with variations in the resolutions of a virtual-micro MLC and field edge angle. The positional accuracy of the couch movement was also assessed for clinical implementation. The overhead time for planning and treatment was confirmed as negligible.e.

Angular dependence of an EDGE detector in small fields in clinical settings

Kim Me Young,Yoon Jai-Woong,Cheong Kwang-Ho,Kang Sei-Kwon,구태률,Ha Boram,Lee Me Yeon,Kim Kyoung Ju,Bae Hoonsik,박소아 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.11

Relative output dose was evaluated while changing the gantry angle and couch angle using an EDGE diode detector in a clinical setting. An ELEKTA cone collimator used in stereotactic radiosurgery (SRS) was used for measurements. We place the edge detector at a depth of 10 cm of solid phantom (30×30×20 cm3 ) with a source to axis distance (SAD) of 100 cm. The relative output dose obtained by the EDGE detector was measured while the cone was mounted and the gantry angle was changed under the conditions of 0°, 45°, 90°, 315°, and 270°. As the distance of the passing beam increases as the gantry angle increases at table angle 0°, the intensity of the beam decreases and has a minimum value at the angle of 56.3°, 123.7°, 236.3°, and 303.7°. The sensitivity of output was highest in the anterior direction, and it showed a tendency to decrease in the posterior direction. It can be seen that the relative dose decreases around 60 and 120 degrees according to the change of the table angle, which is thought to be due to the change in beam transmittance according to the beam passing distance and the structure of the EDGE detector, and the sensitivity of the detector. It is also meaningful to report the dependence of the output dose on the angle when measuring using the phantom used in actual clinical practice.

Beam Shaping by Independent Jaw Closure in Steveotactic Radiotherapy

안용찬,조병철,최동락,김대용,허승재,오도훈,배훈식,여인환,고영은,Ahn Yong Chan,Cho Byung Chul,Choi Dong Rock,Kim Dae Yong,Huh Seung Jae,Oh Do Hoon,Bae Hoonsik,Yeo In Hwan,Ko Young Eun The Korean Society for Radiation Oncology 2000 Radiation Oncology Journal Vol.18 No.2

서론 :정위방사선치료는 높은 정밀도로 크기가 작고 구형인 병변에 국한하여 방사선을 조사할 수 있는 기술이지만 병변의 모양이 구형이 아닌 경우에는 병변 주변의 정상조직에 고선량의 방사선이 조사될 수 있다. 본 연구는 독립턱을 부분적으로 폐쇄하여 방사선량 분포를 개선하는 방법, 선량계산과 선량분포의 도시방법을 보고하고자 한다. 방법 :정위방사선치료 시의 호의 궤적상 병변은 방사선조사영역 내에 포함하면서 주변 정상조직을 최대한 차폐하도록 원형 콜리메이터와 독립턱 부분페쇄를 적절히 조합하였다. 물 펜톰과 마이크로 전리함을 이용하여 출력인자와 조직최대선량비를 측정하여 이론적 계산치와 비교하였다. 필름선량측정계를 이용하여 5 cm 깊이에서의 심부선량분포를 측정하여 계산치와 비교하였다. 이와 같은 측정자료를 자가 개발한 치료계획 프로그램에 반영하여 뇌전이 환자의 정위 방사선치료 선량계산과 도시에 적용하여 원형 콜리메이터만을 이용하였을 경우와 독립턱 부분폐쇄를 추가하였을 경우의 병변과 정상 뇌의 선량체적표를 각각 비교하였다. 결과 : 5.0 cm 직경의 원형 콜리메이터를 사용하고 한 쪽 독립턱을 중심축으로부터 30 mm, 15.5 mm, 8.6 mm, 0 mm 까지 열었을 때 측정한 출력인자와 조직최대선량비는 계산치와 각각 0.5%와 0.3%의 오차범위로 잘 부합하였다. 필름선량계로 얻은 5 cm 깊이의 심부선량분포도 역시 계산치와 잘 부합하였다. 자가 개발한 치료계획 프로그램으로 병변과 정상 뇌의 선량체적표를의 상호 비교를 통하여 독립턱 부분폐쇄를 적용한 경우에 있어서 보다 개선된 선량분포를 얻을 수 있음을 확인하였다. 결론 : 정위방사선치료에 있어서 독립턱의 부분폐쇄를 적용함으로써 보다 개선된 선량분포계획을 얻을 수 있으며 이를 적용하여 비교적 크기가 크고 모양이 불규칙한 병변에 대하여도 정위방사선치료를 확대 적용할 수 있겠다. 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.

Evaluation of the Radiochromic Film Dosimetry for a Small Curved Interface

강세권,박소아,황태진,정광호,한태진,김해영,이미연,김경주,배훈식,Kang, Sei-Kwon,Park, Soah,Hwang, Taejin,Cheong, Kwang-Ho,Han, Taejin,Kim, Haeyoung,Lee, Me-Yeon,Kim, Kyoung Ju,Bae, Hoonsik Korean Society of Medical Physics 2012 의학물리 Vol.23 No.4

눈꺼풀에 발생한 종양의 치료를 위해서는 종종 고에너지 전자선이 이용되며, 이 경우 환자의 시력 보호를 위해 금속차폐체를 눈꺼풀과 안구 사이에 삽입하고 방사선 치료를 시행한다. 차폐체에 접한 눈꺼풀 안쪽의 방사선량 확인을 위해서는 매우 작은 측정도구가 필요하며, 굽은 경계면의 특성상 유연한 측정도구가 바람직한데, radiochromic 필름 도시메트리는 이 목적에 매우 적합하다. 작으면서도 휘어진 경계면을 따라서 선량을 측정하기 위해, 눈꺼풀 팬텀과 차폐체 사이에 3-mm 폭의 EBT2 필름 띠를 삽입하고, 6MeV의 전자선을 조사 후, 선량분포를 얻었다. 금속차폐체와 동일한 크기로 아크릴 재질의 차폐체를 제작하여, 금속인공영상물이 없는 CT 영상을 얻은 후, 이를 이용하여 몬테칼로 전산모사를 수행하였다. 전산모사에서는 실제 안구차폐체의 재질을 따라 텅스텐, 알루미늄 및 스테인레스 스틸 등의 물질 정보를 이용하였다. 이렇게 얻은 전산모사 결과는 필름 측정과 2.1% 내에서 일치하였다. 밀리미터 크기 정도로 작고 또한 휘어진 영역에서 radiochromic 필름 도시메트리는 취급도 용이할 뿐만 아니라 만족스런 정확도를 보여주고 있다. 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.

선량보강(Build-up) 영역에서의 광자선 깊이선량률 측정을 위한 검출기의 특성 비교

강세권,박석원,오도훈,박희철,김수산,배훈식,조병철,Kang Sei-Kwon,Park Suk Won,Oh Do Hoon,Park Hee Chul,Kim Su Ssan,Bae Hoonsik,Cho Byung Chul 한국의학물리학회 2005 의학물리 Vol.16 No.2

표면 선량을 포함한 선량보강(build-up) 영역에 대한 깊이선량률(percentage depth dose)을 측정하는 데 있어서 적절한 측정방법을 결정하기 위해 6 MV 광자선에 대해 Atiix와 Markus 평행평판형 이온함, 원통형이온함, 그리고 다이오드 검출기를 사용하여 측정, 비교하었다. Attix 이온함에 의한 측정을 기준으로 할 때, Markus 이온함의 측정은 민조사면(open field)에서 $2\%$ 내로 일치하였으나, 오염전자가 포함된 광자선의 경우에는 최대 $3.9\%$의 차이를 보였다. 원통형 이온함과 다이오드 선량계의 경우에는 이들 검출기가 물 팬텀에 완전히 잠긴 이후부터는 오염전자가 포함된 광자선에 대해서도 각각 $1.5\%$ 혹은 $1.0\%$ 내의 정확도를 보였다. 따라서 민조사면에서 표면선량을 포함한 깊이선량률을 정확히 측정하기 위해서는 평행평판형 이온함이 추천되나, 표면에서의 정확한 선량에 특별한 관심을 두는 경우가 아니면, 원통형 이온함이나 다이오드 선량계를 이용하여 선량보강영역의 깊이선량률을 측정하는 것은 양호한 결과를 준다고 할 수 있다. To determine the appropriate method out of various available methods to measure build-up doses, the measurements and comparisons of depth doses of build-up region including the surface dose were executed using the Attix parallel-plate ionization chamber, the Markus chamber, a cylindrical ionization chamber, and a diode detector. Based on the measurements using the Attix chamber, discrepancies of the Markus chamber were within $2\%$ for the open field and increased up to $3.9\%$ in the case of photon beam containing the contaminant electrons. The measurements of an cylindrical ionization chamber and a diode detector accord with those of the Attix chamber within $1.5\%\;and\;1.0\%$ and after those detectors were completely immersed in the water phantom. The results suggest that the parallel-plate chamber is the best choice to measure depth doses in the build-up region containing the surface, however, using cylindrical ionization chamber or diode detector would be a reasonable choice if no special care is necessary for the exact surface dose.

Evaluation of delivered monitor unit accuracy of gated step-and-shoot IMRT using a two-dimensional detector array.

Cheong, Kwang-Ho,Kang, Sei-Kwon,Lee, MeYeon,Kim, Su Ssan,Park, SoAh,Hwang, Tae-Jin,Kim, Kyoung Ju,Oh, Do Hoon,Bae, Hoonsik,Suh, Tae-Suk The American Association of Physicists in Medicine 2010 Medical physics Vol.37 No.3

<P>PURPOSE: To overcome the problem of organ motion in intensity-modulated radiation therapy (IMRT), gated IMRT is often used for the treatment of lung cancer. In this study, the authors investigated the accuracy of the delivered monitor units (MUs) from each segment during gated IMRT using a two-dimensional detector array for user-specific verification purpose. METHODS: The authors planned a 6 MV photon, seven-port step-and-shoot lung IMRT delivery. The respiration signals for gated IMRT delivery were obtained from the one-dimensional moving phantom using the real-time position management (RPM) system (Varian Medical Systems, Palo Alto, CA). The beams were delivered using a Clinac iX (Varian Medical Systems, Palo Alto, CA) with the Millennium 120 MLC. The MatriXX (IBA Dosimetry GmbH, Germany) was validated through consistency and reproducibility tests as well as comparison with measurements from a Farmer-type ion chamber. The authors delivered beams with varying dose rates and duty cycles and analyzed the MatriXX data to evaluate MU delivery accuracy. RESULTS: There was quite good agreement between the planned segment MUs and the MUs computed from the MatriXX within +/- 2% error. The beam-on times computed from the MatriXX data were almost identical for all cases, and they matched well with the RPM beam-on and beam-off signals. A slight difference was observed between them, but it was less than 40 ms. The gated IMRT delivery demonstrated an MU delivery accuracy that was equivalent to ungated IMRT, and the delivered MUs with a gating signal agreed with the planned MUs within +/- 0.5 MU regardless of dose rate and duty cycle. CONCLUSIONS: The authors can conclude that gated IMRT is able to deliver an accurate dose to a patient during a procedure. The authors believe that the methodology and results can be transferred to other vendors' devices, particularly those that do not provide MLC log data for a verification purpose.</P>

Multi-institutional Comparison of Intensity Modulated Radiation Therapy (IMRT) Planning Strategies and Planning Results for Nasopharyngeal Cancer

Park, Sung Ho,Park, Hee Chul,Park, Suk Won,Oh, Do Hoon,Choi, Youngmin,Kim, Jeung Kee,Ahn, Yong Chan,Park, Won,Suh, Hyun Sook,Lee, Rena,Bae, Hoonsik The Korean Academy of Medical Sciences 2009 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.24 No.2

<P>The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT.</P>