bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐E‐T‐216: TPS QC Supporting Program by a Third‐Party Evaluation Agency in Japan
Authors: Fukata K , Minemura T , Kurokawa C , Miyagishi T , Itami J
Published: June 2012

Purpose: To equalize the quality of radiation therapy in Japan by supporting quality control of radiation treatment planning system. Methods: Center for Cancer Control and Information Service in National Cancer Center supports the QA‐QC of the cancer core hospitals in Japan as a third‐party evaluation agency. Recently, a program for assessing the quality of treatment planning system (TPS) began as a part of our QA‐QC supporting activities. In this program, a questionnaire about TPS was sent to 45 prefectural cancer core hospitals in Japan. The object of this questionnaire is to assess the proper commissioning, implement and applications of TPSs. The contents of the questionnaire are as follows; 1) calculate MUs which deliver 1000 cGy to the point of SSD = 100 cm, 10 cm depth with field sizes ranging from 5×5 to 30 × 30 cm2, and obtain doses at several depths for the calculated MUs, 2) calculate MUs which deliver 1000 cGy to the point of SSD = 100 cm, 10 cm depth for wedge fields whose angles are from 15 to 60 degrees, and obtain doses at several depths with the MUs, 3) calculate MU which deliver 1000 cGy to the point of STD = 100 cm, 10 cm depth with 10×10 cm2 field size and obtain doses at several depths with the MU. Results: In this program, 179 beam data from 44 facilities were collected. Data were compared in terms of dose per MU, output factor, wedge factor and TMR. It was found that 90% of the data agreed within 2%. Conclusions: The quality of the treatment planning system was investigated through the questionnaire including the information of essential beam data. We compared 179 beam data in TPSs sent from 44 facilities and 90% of the data showed good agreement.
SU‐E‐T‐217: Automated Data Mining of Lung SBRT Cases for Predicting Dosimetric Indices in Prospective Plans
Authors: Atwood T , Xing L , Hristov D
Published: June 2012

Purpose: To develop an automated technique for evaluating lung stereotactic body radiotherapy (SBRT) plan quality and predicting achievable lung dose constraints. Methods: We examined the workflow scripting capabilities of a radiation oncology software package (MIM Software Inc) for automatically generating mean dose gradients and overlap volume histograms (OVHs) for lung SBRT plans. Mean dose gradients were created to assess plan quality by quantifying the dose fall‐off from the planning target volume (PTV) into the ipsilateral lung. OVHs were created to evaluate potential predictors of achievable lung dose constraints by measuring the amount of ipsilateral lung volume overlapping the uniformly expanded PTV. Based on the knowledge that OVHs will depend on the size and spatial relationship of the lung and PTV structures, we hypothesize that OVH‐derived indices will therefore serve as predictors of achievable lung dose. The workflow scripts were evaluated in a pilot study of 10 lung SBRT plans (50 Gy in 5 fractions) with varying PTV sizes and locations. Results: The scripted workflows were successful in automatically generating mean dose gradients and OVHs for the PTV and ipsilateral lung. The workflows were able to produce the aforementioned data in a matter of seconds (per patient), which would have otherwise been excessively time consuming and labor intensive. From the pilot study, the average mean dose gradient was ‐ 4.1 ± 0.6, indicating that all evaluated patients had similar and acceptable plan quality. Furthermore, the OVH data indicated that a 0 mm PTV expansion and a 10 mm PTV expansion correlated with the mean lung dose (correlation coefficients of 0.71 and 0.56, respectively). Conclusions: Our current data demonstrate that mean lung dose correlates to multiple OVH indices. These results indicate that automated large‐scale mining of retrospective data is a highly promising approach for predicting dosimetric indices in prospective lung SBRT plans.
SU‐E‐T‐219: A Free and Open Source DICOM Solution: DicomPack
Authors: Zhang B
Published: June 2012

Purpose: DicomPack aims to provide a Perl DICOM library to isolate DICOM complexity and facilitate creation of DICOM applications. Methods: DicomPack was initially designed for research projects to process and exchange radiotherapy medical images and treatment plans among research institutions, as well as between treatment planning systems and Open Radiological Archiving and Communication System (ORACS) research database. DicomPack uses an extensible internal data structure to store any encoded information observing DICOM's tag/element structure. Therefore, DicomPack either populates a data structure by DICOM information or converts a populated data structure into DICOM format. In this way, DicomPack creates a DICOM file either from scratch or using an existing DICOM template upfront. And this design also enables DicomPack to handle nested sequence data and multi‐frame images easily. Along with DicomPack∷IO, DicomPack∷Network provides a comprehensive solution of exchanging DICOM information through DIMSE (DICOM Message Service) protocol. Its callback plugin design provides a universal interface to all DIMSE commands (DIMSE‐C and DIMSE‐N). Each time a new DIMSE command needs to be implemented, users only need to provide callback procedures to answer some basic questions, such as where to retrieve/store DICOM information. In addition, DicomPack provides examples, e.g., DicomDumper, DicomAnonymizer, DicomStore, under DicomPack∷Util to demonstrate how to develop DICOM applications through DicomPack. Results: Conclusions: DicomPack is a pure Perl package, which means DicomPack only has dependency on core Perl functions. As free software, DicomPack can be redistributed and/or modified as Perl. The easiest way to install DicomPack is through cpan.org (Comprehensive Perl Archive Network). However, DicomPack is in no way intended to to interpret DICOM information and/or enforce DICOM conformance, which will be up to application developers.
SU‐E‐T‐220: A Web‐Based Research System for Outcome Analysis of NSCLC Treated with SABR
Authors: Le A , Yang Y , Michalski D , Heron D , Huq M
Published: June 2012

Purpose: To establish a web‐based software system, an electronic patient record (ePR), to consolidate and evaluate clinical data, dose delivery and treatment outcomes for non small cell lung cancer (NSCLC) patients treated with hypofractionated stereotactic ablative radiation therapy (SABR) across institutions. Methods: The new trend of information technology in medical imaging and informatics is towards the development of an electronic patient record (ePR), in which all health and medical information of each patient are organized under the patient's name and identification number. The system has been developed using the Wamp Server, a package of Apache web server, PHP and MySQL database to facilitate patient data input and management, and evaluation of patient clinical data and dose delivery across institution using web technology. The data of each patient to be recorded in the database include pre‐treatment clinical data, treatment plan in DICOM‐RT format and follow‐up data. The pre‐treatment data include demographics data, pathology condition, cancer staging. The follow‐up data include the survival status, local tumor control condition and toxicity. The clinical data are entered to the system through the web page while the treatment plan data will be imported from the treatment planning system (TPS) using DICOM communication. Results: The collection of data of NSCLC patients treated with SABR stored in the ePR is always accessible and can be retrieved and processed in the future. The core of the ePR is the database which integrates all patient data in one location. Conclusions: The web‐based DICOM RT ePR system utilizes the current state‐of‐the‐art medical informatics approach to investigate the combination and consolidation of patient data and outcome results. This will allow clinically‐driven data mining for dose distributions and resulting treatment outcome in connection with biological modeling of the treatment parameters to quantify the efficacy of SABR in treating NSCLC patients.
SU‐E‐T‐228: The Beauty and the Beast: Transition from Film/paper Charts to Paperless Environment with a New TrueBeam/ARIA System in a Small Community Hospital on a Tight Budget
Authors: Chu K , Rasmussen B
Published: June 2012

Purpose: To review the issues a physicist may encounter in a community hospital during the transition from film/paper charts to a paperless environment with ARIA and a TrueBeam LINAC. With a lean budget, it was necessary for the physics group to take on the project management responsibilities in order save costs. This work highlights the lessons learned during the planning and execution of our project. Methods: Like many hospitals around the county, our hospital was caught in the economic downturn and was unable to provide all of the capital necessary to upgrade to the radiation oncology department. However, with the support of the hospital foundation, a total of $6M was secured for new LINAC, ARIA and CT simulator. To save costs on facilities and computers, it was necessary for the physics group to be involved in creating architectural drawings for shielding calculations, finding a vendor to remove the old linac, assisting the foundation to raise money, submission of the ‘Certificate of Need’ approval with the state, negotiation with vendors, IT infrastructure, reviews with the general contractor and vendor's project team, and ultimately writing the commissioning reports for the new systems as well as developing new policies and procedures. Results: During a period of 4 months, the old LINAC was removed, facility renovations made, the TrueBeam linac was installed, accepted, and commissioned and first patients were treated. In addition, we transitioned from a film/paper environment to a paperless environment. However, this was very stressful for staff and it may be advisable to stage such a project over a longer period of time. There was also significant lost revenue (∼$2M) during downtime of construction, installation, and commissioning. Conclusions: The radiation oncology department was upgraded (The Beauty) on a tight budget but at the cost of added stress (The Beast) to the staff.
SU‐E‐T‐230: Field Factor Verification in Small Fields
Authors: Jia Y , Zhang H , Desrosiers C , Das I
Published: June 2012

Purpose: Small field is being commonly used in radiosurgery and IMRT, however dosimetry is challenging due to source size, electronic disequilibrium and detector size. Correction factor, K, has been published for a limited set of detectors and beam energies. Validity of K for several detectors is investigated. Also extrapolation ion chamber could be used using reciprocity theorem for small fields which is attempted in this study. Methods: Various small volume detectors: IBA SFD, PTW TN60012 diode, and PTW Pinpoint N31006, Standard Imaging A16, along with Nuclear Associate N2339IT extrapolation chamber were used to measure output of square fields from 1×1 to 10×10 cm2 for Varian 6 and 16 MV beams. Measurements were made in a water phantom at 1.5cm depth for 6MV photon and 3.0cm depth for 15MV photon with SSD 100cm. Extrapolation chamber was used in solid water. Published correction factors (Francescon et al, MP, 2011)1, K were used for the detectors used in this study. The K value was derived for extrapolation chamber by modeling based on the difference between its detector output and the average output factor from the diodes and pinpoints. Results: The variation in output as measured from different detector is significant (±7.0%) for field sizes = 3×3 cm2 and converges after large field sizes for both energies. The output factor for the extrapolation chamber was out of range from diodes/pinpoints in both 6MV and 16 MV beams. After applying detector K, the field size factors agree each other within ±2.2% for all field sizes. Conclusions: The value of K provides reasonably good data for field factors irrespective of detector and the field factors can be matched within 2.2%. A mathematical function for extrapolation chamber also provides field factors comparable to the other detectors.
SU‐E‐T‐234: LET Measurement Using Nuclear Emulsion and Monte Carlo Simulation for Proton Beam
Authors: Shin J , Cho S , Park S , Lee S , Kwak J , Kim S , Morishima K
Published: June 2012

Purpose: The significant issue of particle therapy such as proton and carbon ion biological effect on tumors and normal tissue. This effect closely connected with linear‐energy‐transfer (LET). This work presents a Monte Carlo study using GEANT4 and the verification using Nuclear Emulsion to show LET for proton beam. Methods: National Cancer Center (NCC) has IBA Beam Nozzle and cyclotron for proton therapy. We use proton beam bragg peak range 14cm. Also, we already developed the simulation using GEANT4 and finished validation for scattering proton beam. In our simulation, we make same condition with experimental setup.Nuclear emulsion films interleaved with tissue equivalent absorbers can be fruitfully used to reconstruct proton tracks with very high precision. This Nuclear emulsion film has been supported from Nagoya University, analyzed in Pusan University, was irradiated with a therapeutic proton beam at NCC. The Emulsion packs was located at entrance and bragg peak region of proton. This position means low and high LET region. The scanning of the emulsions has been performed at Nagoya University, where a fully automated microscopic scanning technology has been developed for the OPERA experiment on neutrino oscillations. Results: We could see the reconstructed track of proton scanning emulsion. From film scanning, we got the LET distribution at low and high LET region for several proton tracks. Simulation results was similar distribution within standard deviation in acceptance level. Also we got the RBE distribution using LET measurement for proton beam. Conclusions: We measured LET at entrance and bragg peak region using Monte Carlo study and Nuclear Emulsion film, for NCC proton beam. This results means the good observation of LET using the nuclear emulsion. And this method can be used successfully in medical field.
SU‐E‐T‐237: Leading 25 in 25: A Bibliometric Analysis of Classics Articles in IMRT
Authors: Sayed G , Hebshi A , Devic S , Moftah B
Published: June 2012

Purpose: Scientific publication in IMRT has experienced significant development since its introduction. Bibliometric analyses allow an understanding of how this publication trend is organized at an aggregated level. Citation analysis is one of the most widely used bibliometric tools of scientometrics. Analysis of classics, defined as an articles with 100 or more citations, is common in the biomedical sciences as it reflects an article's influence and the recognition it receives in its professional and scientific community. Our objective was to identify the 25 most frequently cited classic articles in IMRT in the past 25 years. Methods: The 25 most‐cited IMRT articles were identified by searching ISI's Web of Knowledge and Pubmed databases for all related publications from 1986 through 2011. Articles were evaluated for several characteristics such as author(s), institution, country of origin, publication year, type, and number of citations. An unadjusted categorical analysis was performed to compare all articles published in the search period. Results: Our search yielded a cumulative total of 37,197 entries for the publication period. Original research and clinical trial articles accounted for 25,827 and 312, respectively, for a total of 25,719 entries. The 25 most‐cited articles were identified from the latter sum and selected out of 123 classics. The number of citations per article ranged from 203 to 504. IMRT classics appeared in one general and five core journals. Conclusions: This study analyzed publication patterns focused on IMRT, its most influential classic articles, journals that published them, their authors and other salient characteristics. Such information is of importance to researchers and those who wish to study the history and development of the field.
SU‐E‐T‐240: Accuracy of Dose Attenuation Correction for a 6D Carbon Fiber Treatment Couch Using a Virtual Couch Technique Integrated into a Treatment Planning System
Authors: Shioiri K , Kurooka M , Yoshino S , Maehana W , Itou M , Kusano Y , Ide S , Onodera M , Nonaka T , Nakayama Y
Published: June 2012

Purpose: A commercial 6D carbon fiber radiotherapy treatment couch (Imaging Couch Top, BrainLAB) has recently been reported to attenuate photon beams and increase skin dose. To prevent skin toxicity and ensure the target dose, it is important to correct the attenuation properties of the treatment couch with the treatment planning system (TPS). In this study, we evaluated the accuracy of dose attenuation correction by a virtual couch technique integrated into the TPS. Methods: A virtual couch was modeled in the TPS (Eclipse v10.0, Varian). The CT value of the virtual couch was assigned with the CT value of the kilovoltage‐CT images of the treatment couch. A phantom consisting of several plastic water slabs was created. We selected an evaluation point within the phantom on the couch structure at a 9 cm depth from the couch surface, which was placed at the isocenter. The doses at this point were calculated and measured at several gantry angles, from 120 degree to 240 degree at 10 degree steps, and each field size was 10 cm × 10 cm. The prescribed dose was 100 monitor units for 6/10 MV photon beams and 6 MV‐SRS mode (Trilogy Tx, Varian). Dose measurements were performed with an ion chamber. Results: The largest difference between measured and calculated doses was 3.3% for a gantry angle of 120 degree and 6 MV‐SRS mode. The average dose difference was within 1.6% for all gantry angles and photon beams. In the case without attenuation correction, the largest difference was 8.2% and the average difference was 5.2%. Conclusions: Use of the virtual couch technique in TPS accomplished sufficient accuracy for dose attenuation correction of the 6D carbon fiber treatment couch, and it is an effective method for clinical use.
SU‐E‐T‐241: Proton Range Compared to the Treatment Planning Modeled Range
Authors: Tasson A
Published: June 2012

Purpose: To compare the range of the protons measured in the treatment room to the range predicted by Xio. Methods: Depth dose curves were measured using a multi layer ionization chamber for various ranges and modulations. Ranges and modulations were increased in one centimeter increments. The depth dose curves were then analyzed and the measured range was determined. The range is defined as the point where the distal edge of the depth dose curve is equal to 90% of the average value of the dose across the spread out bragg peak. The measured range was then compared to the range predicted by the treatment planning system. The treatment planning system used was Xio. Results: The maximum deviation was found to be 1.6 mm, with the majority of range/modulation combinations falling under 1 mm. Conclusions: The difference in range being modeled by the treatment planning system compared to the range measured in the teatment rooms is acceptable, and an uncertainty of 1.5mm is used for treatment planning.
SU‐E‐T‐243: Dosimeter Parameters Comparison of TrueBeam, Trilogy, and IX Machines
Authors: Li R , Xue T , Song C
Published: June 2012

Purpose: Besides flattening‐filter‐free beams, Varian TureBeam Linac also has conventional flattened photon beams. In our facility, we have TrueBeam, Trilogy and iX machines from Varian; they all have same energy specifications: 6 and 10 MV photon beams, as well as 6, 9, 12, 16 and 20 MeV electron beams. This study is to compare the photon and electron beams dosimeter parameters among the three machines. Methods: Beam data (including PDDs, inline and crossline profiles at various field sizes and various depths) were collected using Sun Nuclear Dosimetry 3D Scanner with nominal 100 cm SSD setup. These data were post processed using Sun Nuclear Dosimetry software, including normalization, interpolation and smoothing. The ion chambers used for scanning are IBA CC13. Results: Photon beams: The percentage depth doses with field sizes of 4×4, 6×6, 10×10, 15×15, 20×20, 30×30 and 40×40 cm × cm of 6 MV and 10 MV photon beams from the three machines are very close. Compared with Varian Golden Beam Data, the maximal variation of PDDs at depths of 5, 10, 15, 20, and 30 cm is 1.0%, with mean value 0.6% and standard deviation 0.28% for 6 MV; for 10 MV beams, they are 2.0% (at depth of 30 cm), 0.9%, and 0.48% respectively. Also, the three machines have very similar beam profiles; the profiles' shoulder, penumbra and umbra match well for both inline and crossline beam profiles at various field sizes and various depths.Electron beams: As compared the percentage surface doses (0.5 mm from the surface), dmax, R90, R80, R50, and R30 of electron beams with energy of 6, 9, 12, 16, and 20 MeV at 10 cm cone, the electron beams of TrueBeam and iX are almost identical. Conclusions: The 6 and 10 MV photon beam data of TrueBeam, Trilogy, and iX have a same variation range when comparing with Varian Golden Beam Data.
SU‐E‐T‐245: Survival Fractions for Head‐And‐Neck Cancer Derived from Tumor‐Volume Variation Curves Using a 2‐Level Cell Population Model
Authors: Chvetsov A , Stewart R
Published: June 2012

Purpose: Volumetric tumor response to radiotherapy is an integrated process which includes several radiobiological mechanisms, such as cell killing, cell proliferation, dead‐cell removal and tumor reoxygenation. Our goal is to reconstruct the information about these underlying radiobiological processes and specifically the cell survival fractions by fitting a 2‐level cell‐population tumor‐volume model to imaging‐derived tumor‐volume variation curves obtained during radiotherapy for head‐and‐neck cancer. Methods: Modeling tumor‐volume during radiotherapy is a challenging problem because it is described by a sum of exponentials; therefore, the problem of accurately fitting a model to measured data is ill‐posed. As an initial point of this research, we utilize a simplest 2‐level cell‐population tumor‐volume model which separates the entire tumor‐cell population into oxygenated viable cells and oxygenated lethally damaged cells. The 2‐level cell population tumor model has the advantage of being conditionally well‐posed. We integrated this parameterized radiobiological model with a least squares objective function and a simulated annealing optimization algorithm to characterize individual patients' time‐dependent tumor‐volume regression rates. The measured tumor‐volume variation curves were taken from a clinical study on tumor‐volume variation during radiotherapy for 14 head‐and‐neck cancer patients in which an integrated CT/linac system was used for tumor‐volume measurements. Results: The 2‐level tumor volume modeling is able to predict tumor behavior throughout an entire treatment for 8 of 14 patients. The average survival fraction 0.44 agrees very well with the published survival fraction of 0.45 for the head‐and‐neck squamous cell carcinoma. However, the 2‐level model cannot describe the variation of the cell disintegration rate which is observed at the end of treatment for some of the head‐and‐neck cancer patients. Conclusions: The 2‐level cell population model is an acceptable approximation for the tumor‐volume for some clinical cases, but it cannot describe all tumor‐volume regression cases. This may be explained by omitting hypoxia in the 2‐level model.
SU‐E‐T‐246: Preliminary Normal Tissue Complication Probability (NTCP) Analysis for Radiation Pneumonitis (RP) after Stereotactic Body Radiotherapy (SBRT)
Authors: Grimm J , Palma D , Xue J , Senan S
Published: June 2012

Purpose: NTCP analysis was performed with Lyman model to study the dose tolerance limits for radiation‐induced pneumonitis (RP) in hypofractionated SBRT. Since SBRT is increasingly being applied for the treatment of large and central tumors, it is important from a clinical point of view to determine the dose tolerance limits for specific risk of toxicity. Methods: Eighteen consecutive patients who were treated using volumetric modulated arc therapy (RapidArc) for lung tumors exceeding 80cc were assessed. The evaluation of toxicity was scored using Common Toxicity Criteria AE4.0. Median follow‐up time was 12.8 months. Clinical outcomes have been published, and we performed an NTCP analysis to determine the complication rate in relation to statistical dose tolerance limits. The dose volume histogram (DVH) reduction techniques of the total lung V20Gy, V15Gy, V10Gy, V5Gy and mean lung dose (MLD) were each analyzed, as well as the ipsilateral lung V5Gy and the contralateral lung V5Gy. The framework of the Lyman Model was used except that each DVH reduction method was analyzed independently instead of using the power‐law relationship for volume dependence. Model parameters were fitted using the Maximum Likelihood technique. Results: RP was reported in 5 patients (CTC Grade 2 in 3, and Grade 3 in 2). Total lung V5Gy and contralateral lung V5Gy were the best predictors of RP (p < 0.0001 for both). For V5Gy, the 10% risk level for Grade 2‐3 RP was 28.4% for total lung and 21.6% for contralateral lung. Conclusions: Analysis of RP endpoints has identified total lung V5Gy and contralateral lung V5Gy as the best predictors of RP following RapidArc. These findings are based on limited clinical data, and longer follow‐up in larger patient cohorts is required in order to determine more accurate dose tolerance limits. Dr. Grimm developed the DVH Evaluator, described at www.DiversiLabs.com and distributed by www.LifeLineSoftware.com. The analysis presented here is part of that software.

Dr. Senan's department has received research funding from Varian Medical Systems, and Dr. Senan has received speakers honoraria from Varian.
SU‐E‐T‐248: An Extended Generalized Equivalent Uniform Dose Accounting for Dose‐Range Dependency of Radio‐Biological Parameters
Authors: Troeller A , Soehn M , Yan D
Published: June 2012

Purpose: Introducing an extended, phenomenological, generalized equivalent uniform dose (eEUD) that incorporates multiple volume‐effect parameters for different dose‐ranges. Methods: The generalized EUD (gEUD) was introduced as an estimate of the EUD that incorporates a single, tissue‐specific parameter ‐ the volume‐effect‐parameter (VEP) ‘a’. As a purely phenomenological concept, its radio‐biological equivalency to a given inhomogeneous dose distribution is not a priori clear and mechanistic models based on radio‐biological parameters are assumed to better resemble the underlying biology. However, for normal organs mechanistic models are hard to derive, since the structural organization of the tissue plays a significant role. Consequently, phenomenological approaches might be especially useful in order to describe dose‐response for normal tissues. However, the single parameter used to estimate the gEUD may not suffice in accurately representing more complex biological effects that have been discussed in the literature. For instance, radio‐biological parameters and hence the effects of fractionation are known to be dose‐range dependent. Therefore, we propose an extended phenomenological eEUD formula that incorporates multiple VEPs accounting for dose‐range dependency. Results: The eEUD introduced is a piecewise polynomial expansion of the gEUD formula. In general, it allows for an arbitrary number of VEPs, each valid for a certain dose‐range. We proved that the formula fulfills required mathematical and physical criteria such as invertibility of the underlying dose‐effect and continuity in dose. Furthermore, it contains the gEUD as a special case, if all VEPs are equal to ‘a’ from the gEUD model. Conclusion: The eEUD is a concept that expands the gEUD such that it can theoretically represent dose‐range dependent effects. Its practicality, however, remains to be shown. As a next step, this will be done by estimating the eEUD from patient data using maximum‐likelihood based NTCP modelling in the same way it is commonly done for the gEUD.
SU‐E‐T‐256: Radiation Dose Responses for Chemoradiation Therapy of Pancreatic Cancer: An Analysis of Compiled Clinical Data Using Biophysical Models
Authors: Moraru I , Tai A , Erickson B , Li X
Published: June 2012

Purpose: We have analyzed recent clinical data obtained from chemoradiation of unresectable, locally advanced pancreatic cancer in order to examine possible benefits from radiotherapy (RT) dose escalation as well as to propose possible dose escalated fractionation schemes. Methods: A modified linear quadratic (LQ) model was used to fit clinical tumor response data from chemoradiation treatments using different fractionations. Biophysical radiosensitivy parameters, a and α/β, tumor potential doubling time, Td, and delay time for tumor doubling during treatment, Tk, were extracted from the fits and were used to calculate feasible fractionation schemes for dose escalations. Results: Examination of published data from 20 institutions showed no clear indication of improved survival with raised radiation dose. However, an enhancement in tumor response was observed for higher irradiation doses, an important and promising clinical Result with respect to palliation and quality of life. The radiobiological parameter estimates obtained from the analysis are: α/β = 10 ± 3 Gy, a = 0.010 ± 0.003 Gŷ‐1, Td = 56 ± 5 days and Tk = 7 ± 2 days. Possible dose escalation schemes are proposed based on the calculation of the biologically equivalent dose (BED) required for a 50% tumor response rate. Conclusions: From the point of view of tumor response, escalation of the administered radiation dose leads to a potential clinical benefit, which when combined with normal tissue complication analyses may Result in improved treatments for certain patients with advanced pancreatic cancer. Based on this analysis, a dose escalation trial with 2.25 Gy/fraction up to 69.75 Gy is being initiated for unresectable pancreatic cancer at our institution. Partially supported by MCW Cancer Center Meinerz Foundation
SU‐E‐T‐265: Reducing Pacemaker Doses with a Lead Sheet: A Multi‐Detector Study
Authors: Bourgouin A , Varfalvy N , Beaulieu L , Archambault L
Published: June 2012

Purpose: Evaluate the usability of lead shielding to reduce the dose to pacemakers. The efficiency and risk of this type of skin block will be presented. Methods: A solid water phantom was used and all measurements were made at a depth of 0.5 cm for 6 MV and 23 MV photon beams. Measurements were performed with a parallel plate ion chamber and with a plastic scintillation detector (PSD) prototype. Measurements were made for fields of 10, 20 and 30 cm square. For every field, measurements were made in increment of 5 cm from the center of the field to the edge of the 60 cm long phantom for anterior and posterior beams. All measures have been made with and without a 1.6 mm of lead shielding wrapped in a thermoplastic. Results: For all measurements, both detectors agree to 0.6%, well within the uncertainties of the detectors. With antero‐posterior fields, the benefit of shielding is more important at 23MV (reduction of dose by65%) compared to 6MV (reduction of dose by 46%) when the shielding is out of the field. For distances larger than 35 cm, no benefits are measured. In the case were the lead is completely inside the fields, the dose is increased by the presence of shielding. The same observation is made for postero‐anterior fields. For shielding out of field, the dose is slightly increased. Conclusions: The used of lead shielding with antero‐posterior field is advised and provided an easy way to decrease dose to pacemaker. For a postero‐anterior field, it is preferable to avoid shielding, but it could be used if it stays outside fields in the case of a multiple beams treatment. PSD has been shown to be an excellent candidate for in vivo monitoring dose to pacemakers and also site like foetus.
SU‐E‐T‐268: Evaluation of Photoneutron Contamination in Elekta Synergy‐S High‐Energy Linear Accelerator and Indigenous Novel Solution: The AIIMS Experience
Authors: Subramani V , Singh M , Sharma S , Bisht R , Gopishankar N , Rath G
Published: June 2012

Purpose: The photoneutron contamination problem was encountered due to laminated barrier wall and short maze. The purpose of this study was to report our experience in evaluating the photoneutron contamination during radiation safety survey and solution. Methods: The photoneutron contamination measurement was carried out in Elekta Synergy‐S high‐energylinear accelerator for 15MV beam. A NE Neutron survey meter and for photon, Victoreen and RADOS survey meters were used. The laminated barrier wall composed of 37cm steel with 30cm concrete both side and short maze length of 5 meter. During safety survey, higher photoneutron levels for 15MV X‐rays at treatment room door found. The effect of photoneutron contamination as function of neutron shielding materials of wood, polyethylene and boron and thickness, distance, locations and directions to the control console at distance upto 7 meter were investigated for 4 gantry angles at locations of treatment room entry doors namely door1(A), door2(B), console(C), conduit (D) and above‐ceiling(G) for 15MV. Results: The initial safety survey showed that neutron level of 47mR/h and photon leakage of 3.2mR/hr at the treatment entry room door1. The neutron values could bring down to the level of acceptance at the treatment entry door2, but the photon values are not acceptable. Therefore, 30cm concrete wall block was made at the location of door2 and another bend was taken. Finally, treatment entrance room door was made using 3cm polyethylene neutron shielding materials in order to achieve the both neutron contamination and photon leakage within the acceptable levels. Conclusions: The neutron sliding‐door is operated manually in finger‐push by technologist for day‐to‐day usage. This simple solution is cost effective and increases the patient throughput. This study underlines that one needs to take appropriate safety measures prior to facility design whenever the space constraints situations arises for high energy linear accelerator.
SU‐E‐T‐270: Optimized Shielding Calculations for Medical Linear Accelerators (LINACs)
Authors: Muhammad W , Lee S , Hussain A
Published: June 2012

Purpose: The purpose of radiation shielding is to reduce the effective equivalent dose from a medical linear accelerator (LINAC) to a point outside the room to a level determined by individual state/international regulations. The study was performed to design LINAC's room for newly planned radiotherapy centers. Methods: Optimized shielding calculations were performed for LINACs having maximum photon energy of 20 MV based on NCRP 151. The maximum permissible dose limits were kept 0.04 mSv/week and 0.002 mSv/week for controlled and uncontrolled areas respectively by following ALARA principle. The planned LINAC's room was compared to the already constructed (non‐optimized) LINAC's room to evaluate the shielding costs and the other facilities those are directly related to the room design. Results: In the evaluation process it was noted that the non‐optimized room size (i.e., 610 × 610 cm2 or 20 feet × 20 feet) is not suitable for total body irradiation (TBI) although the machine installed inside was having not only the facility of TBI but the license was acquired. By keeping this point in view, the optimized INAC's room size was kept 762 × 762 cm 2. Although, the area of the optimized rooms was greater than the non‐planned room (i.e., 762 × 762 cm 2 instead of 610 × 610 cm 2), the shielding cost for the optimized LINAC's rooms was reduced by 15%. When optimized shielding calculations were re‐performed for non‐optimized shielding room (i.e., keeping room size, occupancy factors, workload etc. same), it was found that the shielding cost may be lower to 41 %. Conclusions: In conclusion, non‐ optimized LINAC's room can not only put extra financial burden on the hospital but also can cause of some serious issues related to providing health care facilities for patients.
SU‐E‐T‐274: Monte Carlo Simulations of Output Factors for a Small Animal Irradiator
Authors: Pidikiti R , Stojadinovic S , Song K , Speiser M , Solberg T
Published: June 2012

Purpose: Measurement of dosimetric parameters of small photon beams, with field sizes as small 1 mm in diameter, is particularly challenging. This work utilizes Monte Carlo techniques to calculate percent depth dose (PDD) and output factors for small photon fields from a kV x‐ray based small animal irradiator. Methods: Absolute dose calibration of a commercial small animal stereotactic irradiator (XRAD225, Precision X‐ray) was performed in accordance with the recommendations of AAPM TG‐61 protocol. Both in‐air and in‐water calibrations were performed at a 30.4 cm source‐to‐surface distance (SSD) for a reference collimator 50 mm in diameter. The BEAM/EGS was used to model 225 kV photon beams used for most therapeutic applications. The Monte Carlo model was provided good agreement with measured beam characteristics, e.g. PDD and off‐axis ratios. Subsequently, output factors for various square and circular applicators were measured using an ionization chamber and radiochromic film, and compared with MC simulations. Directional Bremsstrahlung splitting (DBS) was utilized for variance reduction to improve efficiency of the output factor simulations. The statistical uncertainty on the MC‐ calculated results is between 0.5% and 1% for most points. Results:The absolute dose measured for reference collimator at 30.4 cm SSD in water and in air is 4.1 and 4.12 Gy/min. The agreement between simulated and measured output factors was excellent, ranging from 1% to 2.84%. The MC‐ simulated and measured depth dose data, normalized at the surface, show excellent agreement, with a maximum deviation is approximately 2.5 %. Conclusions: Monte Carlo simulation provides an indispensible tool for validating measurements of the smallest field sizes used in preclinical small animal irradiation.
SU‐E‐T‐281: Secondary Light‐Ions in Carbon‐Ion Therapy: A GEANT4 Simulation of LET and Dose Contributions
Authors: Johnson D , Chen Y , Ahmad S
Published: June 2012

Purpose: The purpose of this investigation was to reveal the dosimetric characteristics and contributions of the secondary light ions produced from carbon‐ion beams in water via a GEANT4 simulation. Methods: GEANT4 low energy electromagnetic physics processes were used for all ions. The hadronic interactions of protons and neutrons are simulated using low energy elastic interactions while inelastic scattering is simulated with a binary cascade (BIC) model. Other inelastic light‐ion interactions are being simulated through the application of a quasi‐molecular dynamics (QMD) model. A 27 liter cubic water phantom consisting of 3000 packed rectangular detector sheets (30 cm × 30 cm × 0.1mm) was used in this simulation. A 1 mm diameter pencil beam of 1 million incident carbon‐ions was used in all simulations presented. The incident energies per nucleon of the carbon beams studied were selected 155 MeV, 262 MeV and 369 MeV. The energy deposition, total kinetic energy, fluence, and dose averaged LET of each secondary particle produced within each detection sheet was determined to study their variations with depth. The particles investigated were gamma, neutron, electron, positron, proton, deuteron, triton, alpha, He‐ 3, Li‐6, Li‐7, Be‐7, Be‐9, Be‐10, B‐10, B‐1 1, C‐1 1, C‐12, C‐13, C‐14, N‐13, N‐14, N‐15, O‐16. Results:The relative dose contributions of four secondary ions (B‐11, C‐1 1, Alpha and Proton) were found to be each greater than 1%. The highest dose averaged LET value was from N‐13, though its averaged dose contribution was less than 5×10−4 %. Conclusions: The secondary particles contribute small portion to the total dose deposited from primary carbon beam. Though heavier ions (N, O) show significant higher LET values, their relative dose contributions were negligible.
SU‐E‐T‐285: Flatness as a Measure of Changes in Photon Energy for Megavoltage X‐ Ray Radiotherapy
Authors: Gao S , Rose M , Simon W , Balter P
Published: June 2012

Purpose: To compare the sensitivity of flatness based energy metrics versus an attenuation based metric (percent depth dose) as a function of energy changes from the linac's nominal clinical energy. Methods: Energy changes were accomplished by adjusting the bending magnet current (BMI) ±15% away from the value used clinically. Two metrics for flatness, relative flatness in the central 80% of the field (flatness) and average maximum dose along the diagonals normalized by central axis (CAX) dose (diagonal normalized flatness, DNF), were measured using a commercially available ion chamber array (IC profiler, Sun Nuclear, Melbourne FL). Percent depth dose was measured in water for depths of 5 and 10 cm in 3×3 and 10×10 cm̂2 field sizes. Results:The sensitivity of percent depth dose (PDD) and flatness to energy changes were smaller than changes in DNF. For 6X the changes in PDD were from −1+ to +3% and the changes in flatness were from ‐5% to +2% for energy changes of ±15% from the nominal energy, for 18X the PDD changed from −0.5% to +2.5% and the flatness from ‐5% to +2% over this energy range. DNF changed from +12% to −8% for 6X and from +8% to ‐6% for 18X over a ±15% change from the nominal energy and showed a near linear correlation with energy. In addition DNF was the only metric that was found to be sensitive to both increases and reductions of energy for both the 6 and 18 MV beams. Conclusions: Diagonal normalizedflatness was found to be the most sensitive metric to energy changes for photon beams of 6 and 18 MV. The IC profiler allows this metric to be conveniently measured as part of routine linac quality assurance. Sun Nuclear Corporation provided the IC profiler.
SU‐E‐T‐287: Patterns of Patient Specific Dosimetry in Total Body Irradiation
Authors: Akino Y , McMullen K , Das I
Published: June 2012

Purpose: Total body irradiation (TBI) is commonly used for conditioning prior to transplant in hematologic and immunologic diseases. Due to variability in body thickness, achieving dose uniformity across body within ±10% of the prescribed dose is challenging. The dose uniformity is further complicated by, techniques and beam energy used, lung shielding and selection of detector. The translational table technique for TBI could compensate for estimated delivered dose to whole body by adjusting couch speed during treatment. However, it is difficult to accurately estimate the dose by calculation and hence in vivo dosimetry (IVD) is routinely performed for TBI. The patterns of patient specific dosimetry, IVD are presented in this study. Methods: Under IRB exempt status, 161 patients who received TBI treatment between 2006 and 2011 were retrospectively analyzed using the treatment records from Cobalt‐60 teletherapy unit and translational treatment couch. During treatment, IVD detectors (TLD, diode, or MOSFET) were placed on patient surface; both entrance and exit dose were recorded at the patient's head, neck, mediastinum, umbilicus, and knee. When large differences between prescribed and measured dose were observed, the dose delivery was corrected for subsequent fractions by adjustment in couch speed and/or bolus placement. Results:Across the entire cohort, the mean (range) percent variance between calculated and measured dose were −2.3% (−66.2 − 35.3), 1.1% (−62.2 − 40.3), ‐1.9% (‐66.4 ‐ 46.6), −1.1% (−35.2 − 42.9), and 3.4% (−47.9 − 108.5) for head, neck, mediastinum, umbilicus, and knee, respectively. When the dose differences for multiple fractions were averaged, the compliance (±10%) between prescription and measured dose was improved as at umbilicus from 83.9% to 98.5%. Conclusions: Actual dose measurement analysis of TBI patients reveals a potentially wide variance from calculated dose. Dose uniformity can be significantly improved with immediate feedback after the first fraction prior to subsequent treatments. This work was supported by the JSPS Core‐to‐Core Program No. 23003.
SU‐E‐T‐291: Dosimetry of Double Scattered Proton Beam Fields Used for Cranio‐Spinal Irradiation
Authors: Song X , Sahoo N , Wu R , Taylor M , Georges R , Zhu X , Summers P , Gillin M
Published: June 2012

Purpose: To investigate the effect of source to surface distance on treatment field lateral penumbra width and the consequence of setup error on the dose distribution in the junction between two spinal fields of double scattered proton beams. Methods: The CT images of the Spine Phantom from Radiological Physics Center was used to design a double scattered proton beam treatment plan using Varian Eclipse treatment planning system. PTV included spinal cord, vertebral body and part of spinous process. The PTV was divided into superior and inferior parts and two posterior fields were used to cover the targets with the prescribed dose. 2D dose was measured using IBA MatriXX and EBT2 film at a depth close to the center of SOBPs of both the fields located both at the nominal source to axis distance (SAD) of 270 cm and at an extended SAD. The field separation was changed by ±1 mm to study the effect of setup error. The measured and TPS calculated dose distributions in verification plans in a water phantom were compared. Results:The measured 2‐D doses agreed very well with planned ones for individual fields. 99% of pixels pass 3%/3 mm dose/distance agreement criteria. The CAX dose differences are within 2%. The 80% to 20% penumbra widths at nominal SAD are 7.4/7.7/7.8 mm for planned/MatriXX/EBT2 film respectively, and about 1 mm wider for the extended SAD. The measured maximum dose was about 10% higher than that from the plan, and decreased/increased about 7% when the fields were separated by ±1 mm. Conclusions: The penumbra width is modestly affected by the extended SSD often used for patient treatment. Dose in the junction of two fields is very sensitive to the setup error and the accuracy of the TPS dose calculation in this region may be limited.
SU‐E‐T‐301: A Novel Daily QA Device for Proton Therapy
Authors: Ding X , Zheng Y , Mascia A , Hsi W , Kang Y , Ramirez E , Zeidan O , Foster R , Gao M , Laub S , Pankuch M , Schreuder N , Harris B
Published: June 2012

Purpose: We describe the design and use of a daily QA device for proton therapy. The device is designed for therapists to check the readiness of the IBA Proton Therapy System (IBA, Louvain‐la‐Neuve, Belgium) during morning QA. The checks include connectivity, positioning, mechanical, imaging and dosimetric parameters of the proton therapy system. Methods: The device consists of a commercial QA device, (rf‐DailyQA3 ‐Sun Nuclear Corporation, Melbourne, FL), in conjunction with a home‐made acrylic phantom and mechanical indexing jig. The indexing jig indexes the rf‐DailyQA3 to treatment couch. Fiducial markers embedded in the phantom are used for checking the x‐ray image and alignment accuracy of the imaging system (VeriSuite, MedCom, Darmstadt‐ Germany). The rf‐ DailyQA3 is used to check the proton beam output, range and symmetry, which are acquired during one single beam delivery of 100 monitor units. We developed in‐house software to calculate the variation of beam range and symmetry, based on readings from the various ion chambers inside the rf‐DailyQA3. Results: The device has been employed to perform daily QA since June 2010 at two operational proton treatment centers and will soon be implemented at ProCure's New Jersey center. All QA tests are performed by radiation therapists and reviewed by the medical physicist on duty. Due to the simplicity of the device and the associated processing software, the QA time is less than 20 minutes per room. The measurement data collected by the device during daily QA are recorded in the OIS. The integrity of the data is validated by comparing against other independent measurements. Conclusions: The daily QA device has been proven to be robust, reliable and user‐friendly. The performance of this system has been proven to be stable and accurate using trend analyses. Key words:proton therapy, daily QA, output, range, symmetry