bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐102: An Efficient Method to Quantitatively Detect Sub‐Millimeter MLC Bank Alignment Errors Using a Well‐Known QA Device
Authors: Nguyen A , Patton K , Paul T , Duggar W , Yang C 
Published: June 2015

Purpose:To introduce an ultra‐sensitive procedure that can detect and quantify systematic MLC bank alignment error down to 0.2 mm or less. The procedure takes only 5 minutes to run and employs the familiar MapCheck2 device.Methods:Elekta iCOM v13.0 was used to create and deliver a modified 4‐Quadrant field on the Elekta Infinity Linac. The 2D dose distribution was collected on the MapCheck2, at 100 Source‐Detector‐Distance with no external buildup. Using SNC Patient v6.2.3 this planar dose was compared against a reference planar dose established preferably right after commissioning or the most recent Annual QA. To obtain baseline results and tolerance levels leaf bank alignment shifts ranging from −1.0 mm (in‐field) to +1 mm (out‐of‐field) in 0.1 mm increment were intentionally induced. Each shifted field is matched against a reference field with zero shift. A Y‐profile through the CAX, perpendicular to MLC traveling direction, was selected in the software. Percentage dose differences at selected points on this profile were recorded. The mean dose differences were then plotted against the corresponding shift distances.Results:The test is extremely sensitive in picking up MLC alignment error. Shift down to 0.2 mm can be easily detected. Furthermore, the relationship between dose deviations and MLC bank alignment errors is shown to be quite linear. For our setup, each 0.1 mm shift in MLC bank would Result in approximately 2.7% dose deviation from baseline. Based on this Result, monthly QA tolerance level at was set at +/−7%, which translates roughly to 0.25 mm in alignment error.Conclusion:A novel method to quantify MLC alignment error was introduced. The test is short, simple yet very effective. It's been implemented clinically as part of our institution monthly machine QA.
SU‐E‐T‐120: Analytic Dose Verification for Patient‐Specific Proton Pencil Beam Scanning Plans
Authors: Chang C , Mah D 
Published: June 2015

Purpose:To independently verify the QA dose of proton pencil beam scanning (PBS) plans using an analytic dose calculation model.Methods:An independent proton dose calculation engine is created using the same commissioning measurements as those employed to build our commercially available treatment planning system (TPS). Each proton PBS plan is exported from the TPS in DICOM format and calculated by this independent dose engine in a standard 40 × 40 × 40 cm water tank. This three‐dimensional dose grid is then compared with the QA dose calculated by the commercial TPS, using standard Gamma criterion. A total of 18 measured pristine Bragg peaks, ranging from 100 to 226 MeV, are used in the model. Intermediate proton energies are interpolated. Similarly, optical properties of the spots are measured in air over 15 cm upstream and downstream, and fitted to a second‐order polynomial. Multiple Coulomb scattering in water is approximated analytically using Preston and Kohler formula for faster calculation. The effect of range shifters on spot size is modeled with generalized Highland formula. Note that the above formulation approximates multiple Coulomb scattering in water and we therefore chose not use the full Moliere/Hanson form.Results:Initial examination of 3 patient‐specific prostate PBS plans shows that agreement exists between 3D dose distributions calculated by the TPS and the independent proton PBS dose calculation engine. Both calculated dose distributions are compared with actual measurements at three different depths per beam and good agreements are again observed.Conclusion:Results here showed that 3D dose distributions calculated by this independent proton PBS dose engine are in good agreement with both TPS calculations and actual measurements. This tool can potentially be used to reduce the amount of different measurement depths required for patient‐specific proton PBS QA.
SU‐E‐T‐122: Anisotropic Analytical Algorithm (AAA) Vs. Acuros XB (AXB) in Stereotactic Treatment Planning
Authors: Mynampati D , Kuo H , Yaparpalvi R , Scripes P Godoy , Tome W 
Published: June 2015

Purpose:To evaluate dosimetric differences between superposition beam model (AAA) and determinant photon transport solver (AXB) in lung SBRT and Cranial SRS dose computations.Methods:Ten Cranial SRS and ten Lung SBRT plans using Varian, AAA _11.0 were re‐planned using Acuros _XB_11.0 with fixed MU. 6MV photon Beam model with HD120_MLC used for dose calculations. Four non‐coplanar conformal arcs used to deliver 21Gy or 18Gy to SRS targets (0.4 to 6.2cc). 54Gy (3Fractions) or 50Gy (5Fractions) was planned for SBRT targets (7.3 to 13.9cc) using two VAMT non‐coplanar arcs. Plan comparison parameters were dose to 1% PTV volume (D1), dose to 99% PTV volume( D99), Target mean (Dmean), Conformity index (ratio of prescription isodose volume to PTV), Homogeneity Index [ (D2%‐D98%)/Dmean] and R50 (ratio of 50% of prescription isodose volume to PTV). OAR parameters were Brain volume receiving 12Gy dose (V12Gy) and maximum dose (D0.03) to Brainstem for SRS. For lung SBRT, maximum dose to Heart and Cord, Mean lung dose (MLD) and volume of lung receiving 20Gy (V20Gy) were computed. PTV parameters compared by percentage difference between AXB and AAA parameters. OAR parameters and HI compared by absolute difference between two calculations. For analysis, paired t‐test performed over the parameters.Results:Compared to AAA, AXB SRS plans have on average 3.2% lower D99, 6.5% lower CI and 3cc less Brain_V12. However, AXB SBRT plans have higher D1, R50 and Dmean by 3.15%, 1.63% and 2.5%. For SRS and SBRT, AXB plans have average HI 2 % and 4.4% higher than AAA plans. In both techniques, all other parameters vary within 1% or 1Gy. In both sets only two parameters have P>0.05.Conclusion:Even though t‐test results signify difference between AXB and AAA plans, dose differences in dose estimations by both algorithms are clinically insignificant.
SU‐E‐T‐134: Assessing the Capabilities of An MU Model for Fields as Small as 2cm in a Passively Scattered Proton Beam
Authors: Simpson R , Ghebremedhin A , Gordon I , Patyal B 
Published: June 2015

Purpose:To assess and expand the capabilities of the current MU model for a passively scattered proton beam. The expanded MU model can potentially be used to predict the dose/MU for fields smaller than 2cm in diameter and reduce time needed for physical calibrations.Methods:The current MU model accurately predicted the dose/MU for more than 800 fields when compared to physical patient calibrations. Three different ion chambers were used in a Plastic Water phantom for physical measurements: T1, PIN, and A‐16. The original MU model predicted output for fields that were affected by the bolus gap factor (BGF) and nozzle extension factor (NEF). As the system was tested for smaller treatment fields, the mod wheel dependent field size factor (MWDFSF) had to be included to describe the changes observed in treatment fields smaller than 3cm. The expanded model used Clarkson integration to determine the appropriate value for each factor (field size factor (FSF), BGF, NEF, and MWDFSF), to accurately predict the dose/MU for fields smaller than 2.5cm in effective diameter.Results:The expanded MU model demonstrated agreement better than 2% for more than 800 physical calibrations that were tested. The minimum tested fields were 1.7cm effective diameter for 149MeV and 2.4cm effective diameter for 186MeV. The inclusion of Clarkson integration into the MU model enabled accurate prediction of the dose/MU for very small and irregularly shaped treatment fields.Conclusion:The MU model accurately predicted the dose/MU for a wide range of treatment fields used in the clinic. The original MU model has been refined using factors that were problematic to accurately predict the dose/MU: the BGF, NEF, and MWDFSF. The MU model has minimized the time for determining dose/MU and reduced the time needed for physical calibrations, improving the efficiency of the patient treatment process.
SU‐E‐T‐135: Assessing the Clinical Impact of Approximations in Analytical Dose Calculations for Proton Therapy
Authors: Schuemann J , Giantsoudi D , Grassberger C , Paganetti H 
Published: June 2015

Purpose:To estimate the clinical relevance of approximations made in analytical dose calculation methods (ADCs) used for treatment planning on tumor coverage and tumor control probability (TCP) in proton therapy.Methods:We compared dose distributions planned with ADC to delivered dose distributions (as determined by TOPAS Monte Carlo (MC) simulations). We investigated 10 patients per site for 5 treatment sites (head‐and‐neck, lung, breast, prostate, liver). We evaluated differences between the two dose distributions analyzing dosimetric indices based on the dose‐volume‐histograms, the γ‐index and the TCP. The normal tissue complication probability (NTCP) was estimated for the bladder and anterior rectum for the prostate patients.Results:We find that the target doses are overestimated by the ADC by 1–2% on average for all patients considered. All dosimetric indices (the mean dose, D95, D50 and D02, the dose values covering 95%, 50% and 2% of the target volume, respectively) are predicted within 5% of the delivered dose. A γ‐index with a 3%/3mm criteria had a passing rate for target volumes above 96% for all patients. The TCP predicted by the two algorithms was up to 2%, 2.5%, 6%, 6.5%, and 11% for liver and breast, prostate, head‐and‐neck and lung patients, respectively. Differences in NTCP for anterior‐rectum and bladder for prostate patients were less than 3%.Conclusion:We show that ADC provide adequate dose distributions for most patients, however, they can Result in underdosage of the target by as much as 5%. The TCP was found to be up to 11% lower than predicted. Advanced dose‐calculation methods like MC simulations may be necessary in proton therapy to ensure target coverage for heterogeneous patient geometries, in clinical trials comparing proton therapy to conventional radiotherapy to avoid biases due to systematic discrepancies in calculated dose distributions, and, if tighter range margins are considered.Fully funded by NIH grants.
SU‐E‐T‐137: Attenuation of Carbon Fiber IGRT Couch Top for SBRT By Using a MapCheck 2 and Ion Chamber
Authors: Dou K , Li B , Jacobs M , Laser B , Lerma F , Sarfaraz M 
Published: June 2015

Purpose:It is common to use posterior oblique beams in intensity‐modulated radiation therapy (IMRT) and volumetric‐modulated arc therapy (VMAT) for regular and stereotactic body radiotherapy (SBRT). Beam attenuation by the treatment couch is not negligible when the couch is in the beam portal. In this study, we have correlated relative dose versus beam angle through a MapCheck 2TM diode array and an ionization chamber measurement.Methods:A Varian TrueBeam linear accelerator equipped with the image‐guided radiation therapy (IGRT) carbon fiber couch was used for delivery of radiation with different photon energies of 6MV, 15MV and 6MV FFF. A MapCHECK 2TM diode array with a MapPhan was employed for the measurement at three field sizes (3 by 3, 5 by 5, and 10 by 10 cm). The independent measurement was performed with an ionization chamber placed at the center of an acrylic cylindrical phantom at the isocenter. The measured data with the MapCHECK 2TM diode array were averaged over the central 2×2 cm diodes for each measurement. The couch attenuation was deduced from the angular dependence with and without the couch involvement.Results:For the MapCHECK 2TM with MapPhan used only the obvious attenuation was observed at the beam angle between 5 and 10 degree from the angular dependence using a 6MV photon beam. The similar Result was obtained for the MapCHECK 2TM /MapPhan with the couch involvement. The couch attenuation was then deduced from the difference of these two sets of data measurements. Maximum couch attenuation was found up to 4.2% which was verified with the ion chamber measurement.Conclusion:A maximum attenuation of 4.2% was found for the carbon fiber couch top using the MapCHECK 2TM/MapPhan, which is consistent with the ion chamber measurement.
SU‐E‐T‐138: Automated Chart Review Module Including Cross‐Vendor Data Transfer Verification Developed for IHE‐RO Initiative
Authors: Brewer M , Gordon C , Tien C 
Published: June 2015

Purpose:To follow the Integrating Healthcare Enterprise ‐ Radiation Oncology (IHE‐RO) initiative of proper cross‐vendor technology integration, an automated chart checker (ACC) was developed. ACC compares extracted data from an approved patient plan in the Eclipse treatment planning system (TPS) against data existing in the Mosaiq treatment management system (TMS). ACC automatically analyzes these parameters using built‐in quality checklists to provide further aid in chart review.Methods:Eclipse TPS data are obtained using Eclipse scripting API (ESAPI) while Mosaiq TMS data are obtained from a radiotherapy‐treatment‐planning (RTP) file. Using this information, ACC identifies TPS‐TMS discrepancies in 18 primary beam parameters including MU, energy, jaw positions, gantry angle, table angle, accessories, and bolus for up to 31 beams. Next, approximately 40 items from traditional quality checklists are evaluated such as prescription consistency, DRR graticule placement, plan approval status, global max dose, and dose tracking coefficients. Parameters were artificially modified to determine if ACC would detect an error in data transfer and to test each component of quality checklists.Results:Using ESAPI scripting and RTP file‐processing, ACC was able to properly aggregate data from TPS and TMS for up to 31 beams. Errors were artificially introduced into each plan parameter, and ACC was able to successfully detect all of them within seconds. Next, ACC was able to successfully detect mistakes in the chart by identifying deviations with its quality checklists, within seconds.Conclusion:ACC effectively addresses the potential issue of faulty cross‐vendor data transfer, as described by IHE‐RO. In addition, ACC was also able to detect deviations from its built‐in quality checklists. ACC is already an invaluable tool for efficient and standardized chart review and will continue to improve as its incorporated checklists become more comprehensive.
SU‐E‐T‐146: Beam Energy Spread Estimate Based On Bragg Peak Measurement
Authors: Anferov V , Derenchuk V , Moore R , Schreuder A 
Published: June 2015

Purpose:ProNova is installing and commissioning a two room proton therapy system in Knoxville, TN. Beam energy out of the 230MeV cyclotron was measured on Jan 24, 2015. Cyclotron beam was delivered into a Zebra multi layered IC detector calibrated in terms of penetration range in water. The analysis of the measured Bragg peak determines penetration range in water which can be subsequently converted into proton beam energy. We extended this analysis to obtain an estimate of the beam energy spread out of the cyclotron.Methods:Using Monte Carlo simulations we established the correlation between Bragg peak shape parameters (width at 50% and 80% dose levels, distal falloff) and penetration range for a monoenergetic proton beam. For large uniform field impinging on a small area detector, we observed linear dependence of each Bragg peak parameter on beam penetration range as shown in Figure A. Then we studied how this correlation changes when the shape of Bragg peak is distorted by the beam focusing conditions. As shown in Figure B, small field size or diverging beam cause Bragg peak deformation predominantly in the proximal region. The distal shape of the renormalized Bragg peaks stays nearly constant. This excludes usage of Bragg peak width parameters for energy spread estimates.Results:The measured Bragg peaks had an average distal falloff of 4.86mm, which corresponds to an effective range of 35.5cm for a monoenergetic beam. The 32.7cm measured penetration range is 2.8cm less. Passage of a 230MeV proton beam through a 2.8cm thick slab of water results in a ±0.56MeV energy spread. As a final check, we confirmed agreement between shapes of the measured Bragg peak and one generated by Monte‐Carlo code for proton beam with 0.56 MeV energy spread.Conclusion:Proton beam energy spread can be estimated using Bragg peak analysis.
SU‐E‐T‐147: Beam Specific Planning Target Volumes Incorporating 4DCT for Pencil Beam Scanning Proton Therapy of Thoracic Tumors
Authors: Lin L , Kang M , Huang S , Mayer R , Thomas A , McDonough J , Solberg T , Simone C 
Published: June 2015

Purpose:The purpose of this study is to determine whether organ sparing and target coverage can be simultaneously maintained for pencil beam scanning (PBS) proton therapy treatment of thoracic tumors in the presence of motion, stopping power uncertainties and patient setup variations.Methods:Ten consecutive patients that were previously treated with proton therapy to 66.6/1.8 Gy (RBE) using double scattering (DS) were replanned with PBS. Minimum and maximum intensity images from 4DCT were used to introduce flexible smearing in the determination of the beam specific PTV (BSPTV). Datasets from eight 4DCT phases, using ±3% uncertainty in stopping power, and ±3 mm uncertainty in patient setup in each direction were used to create 8*12*10=960 PBS plans for the evaluation of ten patients. Plans were normalized to provide identical coverage between DS and PBS.Results:The average lung V20, V5, and mean doses were reduced from 29.0%, 35.0%, and 16.4 Gy with DS to 24.6%, 30.6%, and 14.1 Gy with PBS, respectively. The average heart V30 and V45 were reduced from 10.4% and 7.5% in DS to 8.1% and 5.4% for PBS, respectively. Furthermore, the maximum spinal cord, esophagus and heart dose were decreased from 37.1 Gy, 71.7 Gy and 69.2 Gy with DS to 31.3 Gy, 67.9 Gy and 64.6 Gy with PBS. The conformity index (CI), homogeneity index (HI), and global maximal dose were improved from 3.2, 0.08, 77.4 Gy with DS to 2.8, 0.04 and 72.1 Gy with PBS. All differences are statistically significant, with p values <0.05, with the exception of the heart V45 (p= 0.146).Conclusion:PBS with BSPTV achieves better organ sparing and improves target coverage using a repainting method for the treatment of thoracic tumors. Incorporating motion‐related uncertainties is essentialThis work was supported by the US Army Medical Research and Materiel Command under Contract Agreement No. DAMD17‐W81XWH‐07‐2‐0121 and W81XWH‐09‐2‐0174.
SU‐E‐T‐152: Building An Ultrafast, Earthquake Proof Treatment Planning System
Authors: Bush K , Freeman J , Zavalkovskiy B 
Published: June 2015

Purpose:Situated 20 miles from 5 major fault lines in California's Bay Area, Stanford Universityhas a critical need for IT infrastructure planning to handle the high probability devastating earthquakes. Recently, a multi‐million dollar project has been underway to overhaul Stanford's radiation oncology information systems, maximizing planning system performance and providing true disaster recovery abilities. An overview of the project will be given with particular focus on lessons learned throughout the build.Methods:In this implementation, two isolated external datacenters provide geographical redundancy to Stanford's main campus datacenter. Real‐time mirroring is made of all data stored to our serial attached network (SAN) storage. In each datacenter, hardware/software virtualization was heavily implemented to maximize server efficiency and provide a robust mechanism to seamlessly migrate users in the event of an earthquake. System performance is routinely assessed through the use of virtualized data robots, able to log in to the system at scheduled times, perform routine planning tasks and report timing results to a performance dashboard. A substantial dose calculation framework (608 CPU cores) has been constructed as part of the implementation.Results:Migration to a virtualized server environment with a high performance SAN has resulted in up to a 45% speed up of common treatment planning tasks. Switching to a 608 core DCF has resulted in a 280% speed increase in dose calculations. Server tuning was found to further improved read/write performance by 20%. Disaster recovery tests are carried out quarterly and, although successful, remain time consuming to perform and verify functionality.Conclusion:Achieving true disaster recovery capabilities is possible through server virtualization, support from skilled IT staff and leadership. Substantial performance improvements are also achievable through careful tuning of server resources and disk read/write operations. Developing a streamlined method to comprehensively test failover is a key requirement to the system's success.
SU‐E‐T‐153: Burst‐Mode Modulated Arc Therapy with Flattening‐Filter‐Free Beams Versus Flattening‐Filtered Beams
Authors: Kainz K , Lawton C , Li X 
Published: June 2015

Purpose:To compare the dosimetry and delivery of burst‐mode modulated arc radiotherapy using flattening‐filter‐free (FFF) and flattening‐filtered (FF) beams.Methods:Burst‐mode modulated arc therapy (mARC, Siemens) plans were generated for six prostate cases with FFF and FF beam models, using the Elekta Monaco v. 5.00 planning system. One 360‐degree arc was used for five cases, and for one case two 360‐degree coplanar arcs were used. The maximum number of optimization points (OPs) per arc was set to 91, and OPs with less than 4 MU were disregarded. All plans were delivered on the Siemens Artiste linear accelerator with 6MV FF (300 MU/min) and comparable‐energy FFF (2000 MU/min, labeled as 7UF) beams.Results:For all cases studied, the plans with FFF beams exhibited DVHs for the PTV, rectum, and bladder that were nearly identical to those for the plans with FF beams. The FFF plan yielded reduced dose to the right femoral head for 5 cases, and lower mean dose to the left femoral head for 4 cases. For all but the two‐arc case, the FFF and FF plans resulted in an identical number of segments. The total number of MUs was slightly lower for the FF plans for five cases. The total delivery time per fraction was substantially lower for the FFF plans, ranging from 25 to 50 percent among all cases, as compared to the FF plans.Conclusion:For mARC plans, FFF and FF beams provided comparable PTV coverage and rectum and bladder sparing. For the femoral heads, the mean dose was slightly lower in most cases when using the FFF beam. Although the flat beam plans typically required slightly fewer MUs, FFF beams required substantially less time to deliver a plan of similar quality.This work was supported by Siemens Medical Solutions and the MCW Cancer Center Fotsch Foundation.