EP-1481 COMPARISON OF PTV MARGINS CALCULATED BY VARIOUS IGRT METHODS FOR PROSTATE CANCER

EP-1481 COMPARISON OF PTV MARGINS CALCULATED BY VARIOUS IGRT METHODS FOR PROSTATE CANCER

ESTRO 31 small. However, it appears that the dosimetric impact of the systematic shifts is more significant. Conclusions: It is shown that it is feas...

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ESTRO 31

small. However, it appears that the dosimetric impact of the systematic shifts is more significant. Conclusions: It is shown that it is feasible and use eful to have an independent point dose validation for the helica al tomotherapy modality. For the selected patient database, resultts showed good agreement between the clinical treatment pllanning system calculations and the independent point dose ca alculations. The dosimetric impact of the systematic and random inter--fractional setup variations were found to be small and statistically insiggnificant.

EP-1479 THE INFLUENCE OF BOWEL AND BLADDER PREPARATIION PROTOCOLS FOR RADIOTHERAPY OF PROSTATE CANCER S. Heng1, J. Low1, S. Kandaiya2 1 Pantai Hospital Kuala Lumpur, Cancer Institute, Kuala a Lumpur, Malaysia 2 University Sains Malaysia, School of Physics, Penang, Malaysia M Objective: To determine the influence of bladd der and bowel preparation protocols on the dose-volume histograms (DVHs) of these organs using cone beam CT (CBCT)-based IMRT treatment planning for prostate cancer patients in our institution, Pantai Hospital Kuala Lumpur. Control patients did not undergo these protoccols. Methods: The pelvic DVHs of 12 prostate cancer patien nts were studied using CBCT images obtained immediately before each h treatment. Six patients had bladder and bowel preparation protocol whilst w the other six patients were the control group. All the patients had gold-seed markers inserted prior to simulation. Contoured blad dder and rectal volumes on CBCT images were compared with plannin ng CT (pCT). All patients were treated with intensity modulated radio otherapy (IMRT) with 7800cGy in 39 fractions over 8 weeks. Results: Compared with the patient with bladd der preparation protocol, patients without bladder preparation instrucction had higher bladder volume and dose variation. The maximum variiation in bladder volume was as high as 75% in the control group. Without bowel preparation protocol, the rectal volumes were smalller initially, but increased during the first 10 fractions, and the ere were more variability. Due to the changes in rectal ?lling on o the day of treatment, the maximum variation in rectal volume was as high as +98%. With bowel preparation protocol, the maximum m rectum volume variations were less than 25%. The changes in prosttate target dose compared to planning dose were minimal as would be e expected from positioning with daily image guidance and gold seed im mplant. Conclusions: There was a large variation in bladder an nd rectal DVH in control group and hence the constraints defined in RTOG-0126 protocol varied from day to day. Patients with blad dder and bowel preparation protocols had improved and consistent vollumes and doses for these organs. EP-1480 IGRT FOR SHORT-TIME RT OF RECTAL CANCER: IMP PACT OF SETUP TECHNIQUE ON THE DOSE DISTRIBUTION J. Alvarez Moret1, R. Loeschel2, N. Repp1, O. Koelbl1, F. F Pohl1, B. Dobler1 1 Regensburg University Medical Center, Department off Radiotherapy, Regensburg, Germany 2 University of Applied Sciences, Department of Compu uter Science and Mathematics, Regensburg, Germany

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Purpose/Objective: The objective of the study was to assess the influence of patient setup technique on n the cumulative dose distribution in patients with rectal cancerr. Dose distributions are compared for setup based on light markers on nly (a) and Cone Beam CT based setup with only translational couch corrections (b) and translational and rotational couch correcctions using the robotic HexaPOD treatment table (c). Materials and Methods: 10 patients who received short-term radiotherapy treatment for rectal cancer (25 5 Gy in 5 fractions) were included in this study. Patients were set up u using light markers, a CBCT study was acquired prior to each fractio on, and setup errors were calculated with the Elekta XVI software, and d the patient position was corrected accordingly. The magnitude of tra anslational and rotational patient setup errors was recorded. For invesstigation of the influence of setup technique on dose distribution,, the planning CT was transformed using an in-house developed software, simulating the setup errors calculated by the XVI software,, since CBCT data cannot be used for accurate dose calculation. Internal organ movements were not taken into account. Three dose distribu utions were computed on transformed planning CT for each fraction: one for the case with setup to light markers only, one for the case e with translational couch correction and one for translational and rotational couch correction. Back-transformation and summation of the ob btained dose distributions represents the achieved cumulative dose e distribution for each scenario. The resulting DVH were compare ed with regard to target coverage. Results: The mean translational setup error in x axis (left-right) was 3.1 mm, 3.2 mm in y (cranio-caudal) and 3.7 7 in z (anterior-posterior). The mean rotational setup error in α (pitch) was 2.2°, 1.5° in β (roll) and 1.0° in γ (yaw). The mean value of the translational setup error over all fractions in x direction was 3.1 mm, 3.3 mm in y and 3.8 mm in z axis. For the rotational setup errors, α mean value was 2.1°, β was 1.6° and γ 1.0. The translational errorrs were at least 5 mm in 20.8% of the measurements. The rotational errors e were > 3° in 14.6% of the measurements. No correlation bettween translational and rotational errors was found. Compared with the original treatment plan, setup using light markers resulted in n reduction of the dose achieved to 95% of the PTV from 96.9% % to 71.8%, setup with translational couch corrections according to XVI X to 76.9% Conclusions: The use of CBCT based correction in 6 degrees of freedom is essential for equitable PTV coverage in short-term radiation therapy of rectal cancer. EP-1481 COMPARISON OF PTV MARGINS CALCULA ATED BY VARIOUS IGRT METHODS FOR PROSTATE CANCER R. Kawamorita1, W. Okada1, R. Nakahara1, K. Ichioka1, K. Ishii1, T. Nakajima1, Y. Nishimura2 1 TANE general hospital, Department of Radia ation Oncology, Osaka, Japan 2 Kinki University School of Medicine, Departm ment of Radiation Oncology, Osaka, Japan Purpose/Objective: In 3D-IGRT for prosta ate cancer, we adopted anterior rectal wall matching instead of prostate p matching not to include the rectal wall in the high dose PTV V region. The purpose of the present study was to compare calculated PTV margins for prostate cancer by 3D-IGRT with anterior rectal walll matching, 2D-IGRT with pelvic bone matching, or no IGRT. Materials and Methods: The 2D-IGRT using ExacTrac system (BrainLab, Feldkirchen, Germany), and 3D-IG GRT using cone-beam CT installed in the Novalis Tx (BrainLab, Feld dkirchen, Germany) were used in this study. Twenty-two patients with h prostate cancer treated by VMAT (VARIAN Medical Systems, USA ) we ere included. All patients were immobilized with a vacuum cushion (Va acLok; MedTech). In total, 1326 images of 2D- and 3D-IGRT were used to o measure inter-fractional setup error (InterFSE), inter-fractional organ n motion (InterFOM), and inter-fractional organ distance (InterFOD). InterFOD is the distance between the posterior edge of prostate and a the anterior wall of rectum which were measured on cone-beam CT of 3D-IGRT. Intrafractional organ motion (IntraFOM) was meassured using165 images for 11 patients. PTV margin was calculated by th he equation of 2.5Σ +0.7σ reported by Van Herk (Σ:systematic error, σ:rrandom error). Results: No IGRT PTV margins calculated frrom InterFSE alone were AP:0.6 cm, CC:0.3 cm, and RL:0.5 cm, re espectively. 2D-IGRT PTV margins calculated from RSS (root sum of square) of InterFOM and IntraFOM were AP:0.6 cm, CC:0.4 cm, and RL:0.1 cm, respectively. 2D-IGRT PTV margins were nearly equal to those of no IGRT except for the RL direction. 3D-IGRT PTV margins calculated from RSS of

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IntraFOM and InterFOD were AP:0.4 cm, CC:0.4 cm, and RL:0.1 cm, respectively. Conclusions: PTV margins in IGRT depended on the method of image guidance. The PTV margins were the smallest for the 3D-IGRT method due to the smallest systematic error. The PTV margins for the RL direction in 2D or 3D-IGRT were both 0.1cm. However, these values were considered to be too small clinically. The PTV margin recipe proposed by Van Herk may underestimate PTV margins due to high weight of the systematic error. Because systematic errors became small in IGRT, a new PTV margin recipe with high weight of random errors may be necessary for IGRT. EP-1482 SETUP CORRECTION PROTOCOL FOR IMAGE-GUIDED RADIOTHERAPY OF THE PROSTATE USING SERRATED GOLD COIL MARKERS G. Martín-Martín1, B. Caballero Perea2, M.V. de Torres Olombrada2, B. Ludeña Martinez2, A. López Férnandez1 1 Hospital Universitario de Fuenlabrada, Department of Radiophysics, Madrid, Spain 2 Hospital Universitario de Fuenlabrada, Department of Radiation Oncology, Madrid, Spain Purpose/Objective: The purpose of this study was to develop an evidence-based setup correction protocol for systematic errors in prostate radiation therapy. Specific aims were to determine: (1) how many images (n) should be averaged to define the systematic error; (2) on which treatment fraction should the protocol be initiated; (3) if this protocol could accurately substitute the daily cone-beam protocol; and (4) to evaluate time trends in displacements during the course of the treatment. Materials and Methods: Daily Megavoltage cone-beam CT volumetric images were acquired for patients with serrated gold coils (VisicoilTM) markers implanted within the prostate gland. A total of 307 volumetric images for a set of 16 patients were analyzed. Field displacements were measured and corrected in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions for each treatment fraction. The setup protocol corrects the mean field displacement found from 5 consecutives images, starting at the first fraction of treatment. Simulations were performed with the measured data to asses the minimum averaged images required to determine the systematic error, and on which treatment fraction should the protocol be initiated. Daily measurements for each direction were evaluated for the 38 fractions of the treatment (for 16 patients) in order to evaluate prostate positional time trends. Results: A correction based on a single image taken on the first fraction actually increased the systematic error compared with no correction; the systematic error was slightly increased by starting the setup protocol in the first fraction. More accurate correction of systematic errors was achieved with increasing number of images averaged, with only small benefit after 4 images. There was evidence of time trends in positioning for the AP and SI directions: In the AP direction there was predominantly a field drift anteriorly and in the SI direction superiorly (maximum mean position ± 1 SD: 0.6±0.8 cm and 0.3±0.5 cm, respectively). Conclusions: The most suitable setup correction protocol in our Department would be to shift the patients by the mean displacement of three consecutive fractions, starting the protocol on the second fraction of the treatment. Such a correction protocol along with weekly measurements to take into account time trends, could appropriately substitute the daily CB setup protocol.

ELECTRONIC POSTER: PHYSICS PROFESSIONAL AND EDUCATIONAL ISSUES

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EP-1483 EXPERIENCE WITH SYSTEMATIC AND MULTI-PROFESSIONAL MANAGEMENT OF RADIOTHERAPY DATAFLOW 1 2 3 B. Wennberg , A. Sundeman , O. Tullgren , O. Dahllöf1 1 Karolinska Universitetssjukhuset, Medical Physics, Stockholm, Sweden 2 Karolinska Universitetssjukhuset, Radiotherapy, Stockholm, Sweden 3 Karolinska Universitetssjukhuset, Oncology, Stockholm, Sweden Purpose/Objective: In 2006 two radiotherapy (RT) sites in Stockholm, Sweden were merged. The combined clinic (situated on 3 sites) had 12 linearaccelerators and also brachytherapy. Over 6.000 new patients are received yearly. The two departments had several doseplanningsystems for external radiotherapy (3) and also several

read-and-verify systems (5) in use, but the goal were to have ONE integrated system for dose-planning, booking and treatments in order to have an effective workflow through the whole RT process. In 2008 one common information system (IFS) was launched based on one database with common methods and terminology for handling the IFS. Materials and Methods: After the formal decision of provider of the IFS a multi-professional system manager group (SMG) were formed to plan the implementation and also to continue to manage the running of the IFS. In the management of the IFS the following were included: education of all staff in methods and terminology used in the IFS, documenting and updating methods used within the IFS, manage local user support groups, analysing incidences or problems stemming from use of the IFS, inform users of known risks (bugs) within the IFS, handle request for changes, handle and documenting all contact with hospital IT-department and/or the supplier of the IFS, planning for upgrades including updating methods and educating staff. A total of 200 users are known in the system with 120 simultaneously log-ins. The SMG answer directly under the management of the combined RT department and have administrator rights in the IFS. Local system supporters are used to help users with day to day question but have no additional rights in the system but can relay suggestions of method improvements to the SMG. Information flow from the SMG to the users is for the formal methods done in the hospitals document management system and for other information web-based in the hospitals intra-web or by an email-based news letter and also via the local support team. Requests from users are done to the local user support groups or directly to the SMG designated email-box. Results: The system was implemented before schedule and has also gone through several successful upgrades since 2008. No major unplanned stops have been recorded. Acceptances of staff have been high of adjusting methods to combine the two clinics into one with the help of the new IFS. Education to staff in how to use the IFS according to local methods by local support staff instead of from the system provider has made an impact on how well local methods are conformed to. Conclusions: Introducing and continuous management of an IFS in RT with a multi-professional group have been successful. Acceptance of methods has been high as several aspects in the clinic are taken into account by the SMG when introducing and/or adjusting methods. EP-1484 CONSTRUCTION OF THE COOPERATION BETWEEN THE HIS AND TMS BY USING IHE ESI INTEGRATION PROFILE M. Mukai1, Y. Okuda1, Y. Yokooka1, M. Seki2, Y. Ando3, H. Tsuji4 1 National Institute of Radiological Sciences (NIRS), Medical infotmatics Section, Chiba, Japan 2 Global forCo., technical division, Tokyo, Japan 3 National Institute of Radiological Sciences (NIRS), Research Center Hospital for Charged Particle Therapy, Chiba, Japan Purpose/Objective: National Institute of Radiological Sciences (NIRS) is a hospital located in Chiba and a single radiation department which has 100 beds and 200 outpatients daily. The diagnosis specialized in the radiation/particle therapy. In 1961, radiation therapy by X rays was begun at NIRS. In addition, charged particle therapy (carbon ion) was begun in 1994, and over 6,500 examples were treated by January, 2012. We have multiple systems such as electronic medical Record systems (EMR), radiology information systems (RIS), laboratory information system (LIS), Picture Archiving and Communication system (PACS), and charged particle therapy treatment management system (TMS). Each system cooperates in a patient demographics information and order information which ordered by CPOE system and realizes a normal use work flow. Our electric medical system and charged particle therapy treatment management system will be updated in March, 2012. We aim to improve interoperability; we report management system that provides linkage between the charged particle therapy treatment management system and electronic medical records system. Materials and Methods: To develop this mechanism, we adopted the ESI (Enterprise Schedule workflow) integration profile which proposed by radiation oncology domain of IHE. IHE (Integrating the Healthcare Enterprise) is the international project. IHE is an initiative by healthcare professionals and industry to improve the way computer systems in healthcare share information. IHE promotes the coordinated use of established standards such as DICOM and HL7 to address specific clinical need in support of optimal patient care. Enterprise Schedule Integration Profile involves the exchange of Schedule, Order, and Results information between Electrical Medical systems and Radiation Oncology treatment management systems. ESI