bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐84: Measurement and Monte‐Carlo Simulation of Electron Phase Spaces Using a Wide Angle Magnetic Electron Spectrometer
Authors: Englbrecht F , Lindner F , Bin J , Wislsperger A , Reiner M , Kamp F , Belka C , Dedes G , Schreiber J , Parodi K 
Published: July 2016

Purpose:To measure and simulate well‐defined electron spectra using a linear accelerator and a permanent‐magnetic wide‐angle spectrometer to test the performance of a novel reconstruction algorithm for retrieval of unknown electron‐sources, in view of application to diagnostics of laser‐driven particle acceleration.Methods:Six electron energies (6, 9, 12, 15, 18 and 21 MeV, 40cm × 40cm field‐size) delivered by a Siemens Oncor linear accelerator were recorded using a permanent‐magnetic wide‐angle electron spectrometer (150mT) with a one dimensional slit (0.2mm × 5cm). Two dimensional maps representing beam‐energy and entrance‐position along the slit were measured using different scintillating screens, read by an online CMOS detector of high resolution (0.048mm × 0.048mm pixels) and large field of view (5cm × 10cm). Measured energy‐slit position maps were compared to forward FLUKA simulations of electron transport through the spectrometer, starting from IAEA phase‐spaces of the accelerator. The latter ones were validated against measured depth‐dose and lateral profiles in water. Agreement of forward simulation and measurement was quantified in terms of position and shape of the signal distribution on the detector.Results:Measured depth‐dose distributions and lateral profiles in the water phantom showed good agreement with forward simulations of IAEA phase‐spaces, thus supporting usage of this simulation source in the study. Measured energy‐slit position maps and those obtained by forward Monte‐Carlo simulations showed satisfactory agreement in shape and position.Conclusion:Well‐defined electron beams of known energy and shape will provide an ideal scenario to study the performance of a novel reconstruction algorithm using measured and simulated signal. Future work will increase the stability and convergence of the reconstruction‐algorithm for unknown electron sources, towards final application to the electrons which drive the interaction of TW‐class laser pulses with nanometer thin target foils to accelerate protons and ions to multi‐MeV kinetic energy.Cluster of Excellence of the German Research Foundation (DFG) “Munich‐Centre for Advanced Photonics”
SU‐F‐T‐85: Energy Modulated Electron Postmastectomy Unreconstructed (PU) Chest Wall (CW) Irradiation Technique to Achieve Heart Sparing
Authors: Hong L , Ballangrud A , McCormick B , Mechalakos J 
Published: July 2016

Purpose:For left‐sided PU patients requiring CW and nodal irradiation, sometimes partial wide tangents (PWT) are not feasible due to abnormal chest wall contour or heart position close to the anterior chest wall or unusual wide excision scar. We developed an energy modulated electron chest wall irradiation technique that will achieve heart sparing.Methods:Ten left‐sided PU patients were selected for this dosimetry study. If PWT were used, the amount of the ipsilateral lung would be ranged 3.4 to 4.4 cm, and the amount of heart would be ranged 1.3 to 3.8 cm. We used electron paired fields that matched on the skin to achieve dose conformity to the chest wall. The enface electron fields were designed at extended SSD from a single isocenter and gantry angle with different energy beams using different cutout. Lower energy was used in the central chest wall part and higher energy was used in the periphery of the chest wall. Bolus was used for the electron fields to ensure adequate skin dose coverage. The electron fields were matched to the photon supra‐clavicle field in the superior region. Daily field junctions were used to feather the match lines between all the fields. Target volumes and normal tissues were drawn according to institutional protocols. Prescription dose was 2Gy per fraction for a total 50Gy. Dose calculations were done with Eclipse EMC_11031 for Electron and AAA_11031 for photons.Results:Six patients were planned using 6/9MeV, three using 9/12MeV and one 6/12MeV. Target volumes achieved adequate coverage. For heart, V30Gy, V20Gy and Mean Dose were 0.6%±0.6%, 2.7%±1.7%, and 3.0Gy±0.8Gy respectively. For ipsilateral lung, V50Gy, V20Gy, V10Gy and V5Gy were 0.9%±1.1%, 34.3%±5.1%, 51.6%±6.3% and 64.1%±7.5% respectively.Conclusion:For left‐sided PU patients with unusual anatomy, energy modulated electron CW irradiation technique can achieve heart sparing with acceptable lung dose.
SU‐F‐T‐87: Comparison of Advanced Radiotherapy Techniques for Post‐ Mastectomy Breast Cancer Patients
Authors: Heins D , Zhang R , Hogstrom K , Sanders M 
Published: July 2016

Purpose:To determine if bolus electron conformal therapy (Bolus‐ECT) combined with intensity modulated x‐ray therapy (IMXT) and flattening filter free volumetric modulated arc therapy (FFF‐VMAT (6x and 10x)) can maintain equal or better dose coverage than standard volumetric modulated arc therapy (Std‐VMAT) while reducing doses to organs at risk (OARs).Methods:Bolus‐ECT with IMXT, FFF‐VMAT, and Std‐VMAT treatment plans were produced for ten post‐mastectomy radiotherapy (PMRT) patients previously treated at our clinic. The treatment plans were created on commercially available treatment planning system (TPS) and all completed treatment plans were reviewed and approved by a radiation oncologist. The plans were evaluated based on planning target volume (PTV) coverage, tumor control probability (TCP), dose homogeneity index (DHI), conformity index (CI), and dose to organs at risk (OAR).Results:All techniques produced clinically acceptable PMRT plans. Overall, Bolus‐ECT with IMXT exhibited higher maximum dose compared to all VMAT techniques. Bolus‐ECT with IMXT and FFF‐VMAT10x had slightly improved TCP over FFF‐VMAT6x and Std‐VMAT. However, all VMAT techniques showed improved CI and DHI over Bolus‐ECT with IMXT. All techniques showed very similar mean lung dose. Bolus‐ECT with IMXT exhibited a reduced mean heart dose over Std‐VMAT. Both FFF‐VMAT techniques had higher mean heart dose compared to Std‐VMAT. In addition, Bolus‐ECT with IMXT was able to reduce mean dose to the contralateral breast compared to Std‐VMAT and both FFF‐VMAT techniques had comparable but slightly reduced dose compared to Std‐VMAT.Conclusion:This work has shown that Bolus‐ECT with IMXT produces clinically acceptable plans while reducing OAR doses. Both FFF‐VMAT techniques are comparable to Std‐VMAT with slight improvements. Even though all VMAT techniques produce more homogenous and conformal dose distributions, Bolus‐ECT with IMXT is a viable option for treating post‐mastectomy patients possibly leading to reduced risks of normal tissue complications.
SU‐F‐T‐89: Investigation of Simultaneous Optimization of Photon and Electron Apertures for Mixed Beam Radiotherapy Based On An Academic Case
Authors: Mueller S , Joosten A , Fix MK , Henzen D , Volken W , Frei D , Stampanoni MFM , Manser P 
Published: July 2016

Purpose:To estimate the dosimetric potential of mixed beam radiotherapy (MBRT) by using a single process optimizing the shape and weight of photon and electron apertures simultaneously based on Monte Carlo beamlet dose distributions.Methods:A simulated annealing based direct aperture optimization capable to perform simultaneous optimization was developed to generate treatment plans for MERT, photon‐IMRT and MBRT. Both photon and electron apertures are collimated with the photon‐MLC and are delivered in a segmented manner. For dosimetric comparison and for investigating the dependency on the number of apertures, photon‐IMRT, MERT and MBRT plans were generated for an academic case consisting of a water phantom containing two shallow PTVs differing in the maximal depth of 5 and 7 cm, respectively and two OARs in distal and lateral direction to the PTVs.Results:For the superficial PTV, the dose homogeneity (V95%–V107%) and the mean dose (in percent of the prescribed dose) to the distal and the lateral OARs of the MBRT plan (94.9%, 16.9%, 17.8%) are superior or comparable to those for the MERT (74%, 18.4%, 15.4%) and the photon‐IMRT plan (89.4%, 20.8%, 24.7%). For the enlarged PTV, the dosimetric superiority of MBRT compared to MERT and photon‐IMRT is even more pronounced. Furthermore, an MBRT plan with 12 electron and 10 photon apertures lead to an objective function value 38% lower than that of a photon‐IMRT plan with 40 apertures.Conclusion:The results of simultaneous optimization for MBRT are promising with regards to further OAR sparing and improved dose coverage to the PTV compared to photon‐IMRT and MERT. Especially superficial targets with deeper subparts (>5 cm) could substantially benefit. Moreover, MBRT seems to be a possible solution of two downsides of photon‐IMRT, namely the extended low dose bath and the requirement of numerous apertures. This work was supported by Varian Medical Systems.This work was supported by Varian Medical Systems.
SU‐F‐T‐93: Breast Surface Dose Enhancement Using a Clinical Prone Breast Board
Authors: Guerra M , Jozsef G 
Published: July 2016

Purpose:The use of specialized patient set‐up devices in radiotherapy, such as prone breast boards, may have unwanted dosimetric effects. The goal of this study was to evaluate the effect of a clinically used prone breast board on skin dose due to buildup.Methods:GafChromic film (EBT3) was used for dose measurements on the surface of a solid water phantom shaped to mimic the curvature of the breast. We investigated two setup scenarios: the medial field border placed at the medial edge of the board and 1 cm contralaterally from that edge. A strip of film was taped to the medial surface of the phantom. Gantry angles varied from 10 to 30 degrees below the lateral gantry position, representing anterior oblique fields. The measurements were performed with and without the presence of the board; the ratio of their corresponding doses (dose enhancement) was evaluated.Results:For the cases where the field edge is at the edge of the board, the dose enhancement is negligible for all the tested angles. When the field edge is 1 cm inside the board, the maximum surface dose enhancement varies depending on the gantry angle between 2.2 for 30 degrees and 3.2 for 20 degrees. The length on the film at which the presence of the board is detectable (i.e. where there is dose enhancement) is longer for the shallower angles.Conclusion:Even the low‐density, thin carbon fiber board with a thin soft foam pad on the top can produce significant dose enhancement on the skin in prone breast treatment due to loss of buildup. However, it happens only when the patient mid‐sternum is over the board, i.e. the medial edge of the field traverses through the board and pad. Even then, the effect occurs only at the field edge, i.e. the penumbral region.
SU‐F‐T‐95: An Automatic Data Verification Method During An Eclipse/Aria Version Upgrade Using Cryptographic Secure Hash Algorithm
Authors: Xu Z , Baker J , Ryu S 
Published: July 2016

Purpose:To develop an efficient way to verify that patient plan and dose information does not change during an Eclipse/Aria database version upgrade.Methods:Eclipse Scripting Application Programming Interface (ESAPI) was used to create a script to retrieve plan information from the Eclipse database before and after the database upgrade for each patient on treatment. Using Cryptographic Secure Hash Algorithm (SHA256), fixed length digest hash values are generated from the plan parameters for each patient. The script is run twice to create two hash values, HVbefore and HVafter, before and after the Aria database upgrade. Separately, the delivered dose information for all patients was verified by comparing two hash values based on a crystal report summary for all patients treated within a date range. Lastly, an Excel macro is used to import the generated hash values for comparison.Results:If HVbefore is the same as HVafter, then the database is considered unchanged based on the collision resistant property of the cryptographic hash function. Otherwise, we conclude that the patient data may have been altered during the upgrade process. In testing the process, all patients passed the comparison. Without using this method, the time to verify a single patient's information was about five minutes. This would result in five hours of work for sixty patients. With this method, we can verify sixty patients in less than thirty minutes before and after the upgrade. This results in time savings of four hours.Conclusion:An automatic database verification method has been developed using ESAPI, SHA‐256 Cryptographic Hash Algorithm and Microsoft Excel. We found that the time to verify the database for sixty patients is less than one hour. The scripts can be integrated into Eclipse or can be run as a stand‐alone executable program for a more automated process and increased time savings.
SU‐F‐T‐102: Automatic Curation for a Scalable Registry Using Machine Learning
Authors: Ruan D , Shao W , Wong J , Veruttipong D , Steinberg M , Low D , Kupelian P 
Published: July 2016

Purpose:growing partnership and contributors to registry efforts an efficient way to perform data integration, de‐duplication, and cleansing, amongst other tasks. This project aims to develop an automatic curation module to discover, clean, and transform new data, and semantically integrate them with the composite hosting registry upon de‐duplication.Methods:We have investigated various similarity metrics for various attributes and value types in the registry. More specifically, cosine word similarity, cosine term frequency‐inverse document frequency, cosine trigram similarity are used to measure similarity between free text fields; Jaccard similarity and histogram matching are used for categorical values, Naive Bayesian probability in combination with Welch's t‐test values are used to measure likelihood of matching for numerical fields. A supervised learning framework is then adopted where these similarity values are used as input to regress out a decision of amongst {“automatic aggregation with high confidence”, “no match (hence expand current registry)”, and “likely match upon confirmation”}. Multi‐class logistic regression, and classification and regression tree (CART) techniques were used. Seven previous rolling versions of the registry with variations in terminology and data duration were used in a cross‐validation setting to test the applicability of the proposed approach.Results:Initial results showed that automatic curation can properly label more than 80% of the label and data fields, significantly alleviating the burden of human operator and the risk of human error. The major limitation of the current approach is ambiguity, e.g., an input tag “MRI” yields multiple potential match. We are investigating the incorporation of context knowledge to reduce such ambiguity to facilitate both automatic curation and human confirmation.Conclusion:(Semi‐)automatic curation provides a sustainable pathway to integrate data both longitudinally and across multiple institutions and data sources. Our preliminary effort has demonstrated the feasibility and potential efficacy of utilizing machine learning techniques for such purposes.This work is supported in part by a Varian research grant.
SU‐F‐T‐107: Correlations Between Dosimetric Indices of Pharyngeal Constrictors and Proximal Esophagus with Associated Patient‐Reported Outcomes Six Months After Radiation Therapy for Head and Neck Cancer
Authors: Chera B , Price A , Kostich M , Amdur R , Mendenhall W , Sheets N , Green R , Marks L , Das S , Mavroidis P 
Published: July 2016

Purpose:To compare the correlations between different dosimetric indices derived from the pharyngeal constrictor muscles and proximal esophagus with patient‐reported difficulty in swallowing 6 months post radiotherapy using a novel patient reported outcome version of CTCAE (PRO‐CTCAE).Methods:Forty‐three patients with oropharyngeal squamous cell carcinoma were treated on a prospective multi‐institutional study. All patients received de‐intensified 60 Gy intensity modulated radiotherapy. We investigated correlations of individual patient dosimetric data of the superior (SPC), middle (MPC), inferior (IPC) pharyngeal constrictor muscles, the superior esophagus (SES), and the inferior esophagus (IES) to their self‐reported 6 month post‐treatment swallowing difficulty responses. Mild (≥ Grade 1) swallowing difficulty responses were used as the clinical endpoint indicating response. The predictive efficacy of Dmean and dose‐volume (VD) points were assessed through the area under the Receiver Operating Characteristic curve (ROC) and Odds Ratio (OR).Results:The SES and SPC had more favorable area under the curves (AUC) for the Dmean (0.62 and 0.70) while the Dmean to the IPC, MPC, and IES produced suboptimal AUCs (0.42, 0.48, and 0.52). Additionally, over the range of VD, the V54 and V55 for the SES and SPC demonstrated the highest AUCs: AUC(SES) = 0.76–0.73 and AUC(SPC) = 0.72–0.69, respectively. The IES, IPC, and MPC had worse AUC results over the range of VD. An optimal OR can be found when V54 = 96% for the SPC, where OR = 3.96 (1.07–14.62).Conclusion:The V45 and V55 of the SES and SPC had the highest correlation to the clinical endpoint compared to the commonly used dosimetric index, Dmean for both the esophagus and constrictor muscles. The reported dosimetric data demonstrates that new dosimetric indices may need to be considered in the setting of dose de‐escalation and self‐reported outcomes.
SU‐F‐T‐115: Uncertainty in the Esophagus Dose in Retrospective Epidemiological Study of Breast Cancer Radiotherapy Patients
Authors: Mosher E , Kim S , Lee C , Pelletier C , Jung J , Jones E , Lee C 
Published: July 2016

Purpose:Epidemiological studies of second cancer risks in breast cancer radiotherapy patients often use generic patient anatomy to reconstruct normal tissue doses when CT images of patients are not available. To evaluate the uncertainty involved in the dosimetry approach, we evaluated the esophagus dose in five sample patients by simulating breast cancer treatments.Methods:We obtained the diagnostic CT images of five anonymized adult female patients in different Body Mass Index (BMI) categories (16– 36kg/m2) from National Institutes of Health Clinical Center. We contoured the esophagus on the CT images and imported them into a Treatment Planning System (TPS) to create treatment plans and calculate esophagus doses. Esophagus dose was calculated once again via experimentally‐validated Monte Carlo (MC) transport code, XVMC under the same geometries. We compared the esophagus doses from TPS and the MC method. We also investigated the degree of variation in the esophagus dose across the five patients and also the relationship between the patient characteristics and the esophagus doses.Results:Eclipse TPS using Analytical Anisotropic Algorithm (AAA) significantly underestimates the esophagus dose in breast cancer radiotherapy compared to MC. In the worst case, the esophagus dose from AAA was only 40% of the MC dose. The Coefficient of Variation across the patients was 48%. We found that the maximum esophagus dose was up to 2.7 times greater than the minimum. We finally observed linear relationship (Dose = 0.0218 × BMI – 0.1, R2=0.54) between patient's BMI and the esophagus doses.Conclusion:We quantified the degree of uncertainty in the esophagus dose in five sample breast radiotherapy patients. The results of the study underscore the importance of individualized dose reconstruction for the study cohort to avoid misclassification in the risk analysis of second cancer. We are currently extending the number of patients up to 30.
SU‐F‐T‐119: Development of Heart Prediction Model to Increase Accuracy of Dose Reconstruction for Radiotherapy Patients
Authors: Mosher E , Choi M , Jones E , Lee C 
Published: July 2016

Purpose:To assess individual variation in heart volume and location in order to develop a prediction model of the heart. This heart prediction model will be used to calculate individualized heart doses for radiotherapy patients in epidemiological studies.Methods:Chest CT images for 30 adult male and 30 adult female patients were obtained from NIH Clinical Center. Image‐analysis computer programs were used to segment the whole heart and 8 sub‐regions and to measure the volume of each sub‐ region and the dimension of the whole heart. An analytical dosimetry method was used for the 30 adult female patients to estimate mean heart dose during conventional left breast radiotherapy.Results:The average volumes of the whole heart were 803.37 cm3 (COV 18.8%) and 570.19 cm3 (COV 18.8%) for adult male and female patients, respectively, which are comparable with the international reference volumes of 807.69 cm3 for males and 596.15 cm3 for females. Some patient characteristics were strongly correlated (R2>0.5) with heart volume and heart dimensions (e.g., Body Mass Index vs. heart depth in males: R2=0.54; weight vs. heart width in the adult females: R2=0.63). We found that the mean heart dose 3.805 Gy (assuming prescribed dose of 50 Gy) in the breast radiotherapy simulations of the 30 adult females could be an underestimate (up to 1.6‐fold) or overestimate (up to 1.8‐fold) of the patient‐specific heart dose.Conclusion:The study showed the significant variation in patient heart volumes and dimensions, resulting in substantial dose errors when a single average heart model is used for retrospective dose reconstruction. We are completing a multivariate analysis to develop a prediction model of the heart. This model will increase accuracy in dose reconstruction for radiotherapy patients and allow us to individualize heart dose calculations for patients whose CT images are not available.
SU‐F‐T‐120: How Many and Which Respiratory Phases Should Be Included During the 4D Robust Optimization Process
Authors: Ge S , Wang X , Mohan R 
Published: July 2016

Purpose:To study how many and which respiratory phases should be included to conduct an efficient 4D robust optimization since contouring CTV and critical organs at all 10 phases are time consuming.Methods:A 4D robust optimization algorithm which simultaneously optimizes dose distributions for all 10 respiratory phases has been developed to desensitize plan quality to various uncertainties. To study the possibility of reducing number of phases included during the optimization process while keep the plan quality, four strategies have been conducted and compared: A. including 2 phases: 0% and 50%; B. including 4 phases: 0%, 20%, 50% and 80%. C. including 5 phases: 0%, 20%, 50%, 60% and 80%; D. including all 10 phases during the optimization process. The resulting plans for two patients were evaluated at all 10 respiratory phases.Results:For patient one, reducing the number of phases included in optimization process will degrade CTV coverage while improve the normal tissue sparing. The possible worst CTV coverage at prescription dose (74Gy) for IMPT plans optimized for strategy A, B, C, D was 98.13%, 98.29%, 99.00% and 99.05% respectively. The CTV coverage is almost the same when including 5 phases compared to including 10 phases. For patient 2, reducing the number of phases included in optimization process will degrade CTV coverage, while the normal tissue sparing is not affected too much. The possible worst CTV coverage at prescription dose for IMPT plans optimized for strategy A, B, C, D was 95.85%, 99.01%, 99.18% and 99.72% respectively. The CTV coverage is similar when including 4 phases or 5 phases compared to including 10 phases.Conclusion:The preliminary data shows that at least 4 phases or 5 phases should be included during optimization process to achieve a high quality IMPT plan considering CTV coverage and normal tissue sparing.