bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐593: Outcomes and Toxicities From a Clinical Trial of APBI Using MERT+IMRT with the Same XMLC
Authors: Jimenez‐Ortega E. , Miguez‐Sanchez C. , Palma B. , Ureba A. , Miras H. , Arrans R. , Barbeiro A.R. , Baeza J.A. , Carrasco F. , Plaza A. Leal 
Published: June 2015

Purpose:We present the results from a clinical trial of accelerated partial breast irradiation (APBI), using mixed modulated photon and electron beams (MERT+IMRT) with the same photon multileaf collimator (xMLC).Methods:Seven patients were enrolled in the first year of the APBI clinical trial. Patients were selected following the conditions included in the NSABP B‐39/RTOG 0413 protocol. The targets and clinically relevant normal structures were contoured on the CT images following this protocol for APBI‐EBRT. All treatments were delivered using combined modulated electron and photon beams by means of the same xMLC installed in a SIEMENS Primus linac, with a reduced SSD equal to 60 cm for electron beams. The plans were performed with a treatment planning system based on full Monte Carlo simulations, called CARMEN, developed by our group. Simultaneously, an alternative IMRT plan was calculated with the commercial TPS PINNACLE v8.0m (Philips), and both plans were compared. An ad‐hoc breast phantom with semi‐spherical geometry called NAOMI was designed for a specific QA protocol. Patients received a total dose of 38.5 Gy, delivered in 10 fractions over 5 consecutive days, with a twice‐a‐day hypofractionated schema.Follow‐up visits during 2.5 years on average were repeated at 1 month post‐treatment, every 3 months for the first year, and every 6 months for the second year. Toxicity was scored according to National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE version 3.0).Results:This APBI technique achieved high loco‐regional control rates and showed low acute toxicity (grade 1 of CTCAE) and no toxicities from first month onwards. Photographic assessment of cosmesis showed skin excellent results.Conclusion:The clinical results achieved with MERT+IMRT by using the same xMLC are comparable or even better than those obtained with other APBI techniques, thanks to a software solution without any additional equipment or specific device.
SU‐E‐T‐607: Performance Quantification of the Nine Detectors Used for Dosimetry Measurements in Advanced Radiation Therapy Treatments
Authors: Markovic M , Stathakis S , Jurkovic I , Mavroidis P , Papanikolaou N 
Published: June 2015

Purpose:The purpose of this study was to quantify performance of the nine detectors used for dosimetry measurements in advanced radiation therapy treatments.Methods:The 6 MV beam was utilized for measurements of the field sizes with the lack of lateral charge particle equilibrium. For dose fidelity aspect, energy dependence was studied by measuring PDD and profiles at different depths. The volume effect and its influence on the measured dose profiles have been observed by measuring detector's response function. Output factor measurements with respect to change in energy spectrum have been performed and collected data has been analyzed. The linearity of the measurements with the dose delivered has been evaluated and relevant comparisons were done.Results:The measured values of the output factors with respect to change in energy spectrum indicated presence of the energy dependence. The detectors with active volume size ≤ 0.3 mm3 maximum deviation from the mean is 5.6% for the field size 0.5 × 0.5 cm2 while detectors with active volume size > 0.3 mm3 have maximum deviation from the mean 7.1%. Linearity with dose at highest dose rate examined for diode detectors showed maximum deviation of 4% while ion chambers showed maximum deviation of 2.2%. Dose profiles showed energy dependence at shallow depths (surface to dmax) influenced by low energy particles with 12 % maximum deviation from the mean for 5 mm2 field size. In relation to Monte Carlo calculation, the detector's response function σ values were between (0.42±0.25) mm and (1.2±0.25) mm.Conclusion:All the detectors are appropriate for the dosimetry measurements in advanced radiation therapy treatments. The choice of the detectors has to be determined by the application and the scope of the measurements in respect to energy dependence and ability to accurately resolve dose profiles as well as to it's intrinsic characteristics.
SU‐E‐T‐608: Perturbation Corrections for Alanine Dosimeters in Different Phantom Materials in High‐Energy Photon Beams
Authors: von Voigts‐Rhetz P , Anton M , Czarnecki D , Zink K 
Published: June 2015

Purpose:Alanine dosimeters are often used for in‐vivo dosimetry purposes in radiation therapy. In a Monte Carlo study the influence of 20 different surrounding/phantom materials for alanine dosimeters was investigated. The investigations were performed in high‐energy photon beams, covering the whole range from 60Co up to 25 MV‐X. The aim of the study is the introduction of a perturbation correction kenv for alanine dosimeters accounting for the environmental material.Methods:The influence of different surrounding materials on the response of alanine dosimeters was investigated with Monte Carlo simulations using the EGSnrc code. The photon source was adapted with BEAMnrc to a 60Co unit and an Elekta (Enom=6, 10, 25 MV‐X) linear accelerator. Different tissue‐equivalent materials ranging from cortical bone to lung were investigated. In addition to available phantom materials, some material compositions were taken and scaled to different electron densities. The depth of the alanine detectors within the different phantom materials corresponds to 5 cm depth in water, i.e. the depth is scaled according to the electron density (ne/ne,w) of the corresponding phantom material. The dose was scored within the detector volume once for an alanine/paraffin mixture and once for a liquid water voxel. The relative response, the ratio of the absorbed dose to alanine to the absorbed dose to water, was calculated and compared to the corresponding ratio under reference conditions. Results: For each beam quality the relative response r and the correction factor for the environment kenv was calculated. kenv=0.9991+0.0049 *((ne/ne,w)−0.7659)3Conclusion:A perturbation correction factor kenv accounting for the phantom environment has been introduced. The response of the alanine dosimeter can be considered independent of the surrounding material for relative electron densities (ne/ne,w) between 1 and 1.4. For denser materials such as bone or much less dense surroundings such as lung, a small correction would be appropriate.
SU‐E‐T‐610: Phosphor‐Based Fiber Optic Probes for Proton Beam Characterization
Authors: Darafsheh A , Soldner A , Liu H , Kassaee A , Zhu T , Finlay J 
Published: June 2015

Purpose:To investigate feasibility of using fiber optics probes with rare‐earth‐based phosphor tips for proton beam radiation dosimetry. We designed and fabricated a fiber probe with submillimeter resolution (<0.5 mm3) based on TbF3 phosphors and evaluated its performance for measurement of proton beam including profiles and range.Methods:The fiber optic probe with TbF3 phosphor tip, embedded in tissue‐mimicking phantoms was irradiated with double scattering proton beam with energy of 180 MeV. Luminescence spectroscopy was performed by a CCD‐coupled spectrograph to analyze the emission spectra of the fiber tip. In order to measure the spatial beam profile and percentage depth dose, we used singular value decomposition method to spectrally separate the phosphors ionoluminescence signal from the background Cerenkov radiation signal.Results:The spectra of the TbF3 fiber probe showed characteristic ionoluminescence emission peaks at 489, 542, 586, and 620 nm. By using singular value decomposition we found the contribution of the ionoluminescence signal to measure the percentage depth dose in phantoms and compared that with measurements performed with ion chamber. We observed quenching effect at the spread out Bragg peak region, manifested as under‐responding of the signal, due to the high LET of the beam. However, the beam profiles were not dramatically affected by the quenching effect.Conclusion:We have evaluated the performance of a fiber optic probe with submillimeter resolution for proton beam dosimetry. We demonstrated feasibility of spectral separation of the Cerenkov radiation from the collected signal. Such fiber probes can be used for measurements of proton beams profile and range. The experimental apparatus and spectroscopy method developed in this work provide a robust platform for characterization of proton‐irradiated nanophosphor particles for ultralow fluence photodynamic therapy or molecular imaging applications.
SU‐E‐T‐613: Physics Considerations for Single‐Isocenter Volumetric Modulated Arc Radiosurgery for Treatment of Multiple Intracranial Targets
Authors: Stanhope C , Chang Z , Wang Z , Yin F , Kim G , Salama J , Kirkpatrick J , Adamson J 
Published: June 2015

Purpose:To address physics challenges associated with single isocenter radiosurgery for multiple intracranial metastases (SIRMIT). Because the Varian High Definition MLC has thicker leaves >4cm from the isocenter, we predict inferior dose falloff and plan quality for small targets located >4cm from isocenter. To address this concern, we evaluate various isocenter placement strategies including one that places the isocenter closer to smaller targets. We also evaluate the significance of arc geometry avoidance angles to limit lens dose.Methods:11 SIRMIT plans with isocenter at centroid were retrospectively analyzed to determine the relationship between relevant dosimetric indices and distance from isocenter (e.g. relative tumor volume). We investigated three isocenter placements for four SIRMIT patients whose lesions had larger variations in target volume; placements included: centroid, Eclipse's built‐in method, and an “inverse center of mass” (ICM) method that weights the isocenter towards smaller lesions. Three VMAT SIRMIT plans were prepared according to institutional and Clark et al.'s guidelines to investigate the effect of arc geometry on lens dose.Results:Dose conformity and gradient fall‐off tended to be better for larger tumors (>1cc) close to isocenter. For the four largest tumors (per plan), centroid CI, GI, and HI values were 9±9%, 12±4%, and 3.8±4.9% better than the next best isocenter placement strategy. None of the methods yielded significantly higher conformity for small tumors, however ICM GI and HI values were better for three of the small tumors by 6±12% and 1.8±2.2% respectively. Lens dose range decreased from [3.3%, 11.4%] to [0.1%, 0.5%] by avoiding arc geometries that enter/exit through the eyes.Conclusion:CI and GI values were poorer for small distal targets, especially >6cm. Large tumors benefited from centroid placement more than small tumors did from ICM. It is necessary to consider arc geometry avoidance angles to adequately reduce lens dose.
SU‐E‐T‐614: Plan Averaging for Multi‐Criteria Navigation of Step‐And‐Shoot IMRT
Authors: Guo M , Craft D , Gao H 
Published: June 2015

Purpose:Step‐and‐shoot IMRT is fundamentally discrete in nature, while multi‐criteria optimization (MCO) is fundamentally continuous: the MCO planning consists of continuous sliding across the Pareto surface (the set of plans which represent the tradeoffs between organ‐at‐risk doses and target doses). In order to achieve close to real‐time dose display during this sliding, it is desired that averaged plans share many of the same apertures as the pre‐computed plans, since dose computation for apertures generated on‐the‐fly would be expensive. We propose a method to ensure that neighboring plans on a Pareto surface share many apertures.Methods:Our baseline step‐and‐shoot sequencing method is that of K. Engel (a method which minimizes the number of segments while guaranteeing the minimum number of monitor units), which we customize to sequence a set of Pareto optimal plans simultaneously. We also add an error tolerance to study the relationship between the number of shared apertures, the total number of apertures needed, and the quality of the fluence map re‐creation.Results:We run tests for a 2D Pareto surface trading off rectum and bladder dose versus target coverage for a clinical prostate case. We find that if we enforce exact fluence map recreation, we are not able to achieve much sharing of apertures across plans. The total number of apertures for all seven beams and 4 plans without sharing is 217. With sharing and a 2% error tolerance, this number is reduced to 158 (73%).Conclusion:With the proposed method, total number of apertures can be decreased by 42% (averaging) with no increment of total MU, when an error tolerance of 5% is allowed. With this large amount of sharing, dose computations for averaged plans which occur during Pareto navigation will be much faster, leading to a real‐time what‐you‐see‐is‐what‐you‐get Pareto navigation experience.Minghao Guo and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500).
SU‐E‐T‐618: Plan Robustness Study of Volumetric‐Modulated Arc Therapy Vs. Intensity‐Modulated Radiation Therapy for Head and Neck Cancer
Authors: Liu W , Patel S , Shen J , Harrington D , Stoker J , Ding X , Hu Y , Wong W , Halyard M , Schild S , Ezzell G , Bues M 
Published: June 2015

Purpose:Lack of plan robustness may contribute to local failure in volumetric‐modulated arc therapy (VMAT) to treat head and neck (H&N) cancer. Thus we compared plan robustness of VMAT with intensity‐modulated radiation therapy (IMRT).Methods:VMAT and IMRT plans were created for 9 H&N cancer patients. For each plan, six new perturbed dose distributions were computed — one each for ± 3mm setup deviations along the S‐I, A‐P and L‐R directions. We used three robustness quantification tools: (1) worst‐case analysis (WCA); (2) dose‐volume histograms (DVHs) band (DVHB); and (3) root‐mean‐square‐dose deviation (RMSD) volume histogram (DDVH). DDVH represents the relative volume (y) on the vertical axis and the RMSD (x) on the horizontal axis. Similar to DVH, this means that y% of the volume of the indicated structure has the RMSD at least × Gy[RBE].The width from the first two methods at different target DVH indices (such as D95 and D5) and the area under the DDVH curves (AUC) for the target were used to indicate plan robustness. In these robustness quantification tools, the smaller the value, the more robust the plan is. Plan robustness evaluation metrics were compared using Wilcoxon test.Results:DVHB showed the width at D95 from IMRT to be larger than from VMAT (unit Gy) [1.59 vs 1.18 (p=0.49)], while the width at D5 from IMRT was found to be slightly larger than from VMAT [0.59 vs 0.54 (p=0.84)]. WCA showed similar results [D95: 3.28 vs 3.00 (p=0.56); D5: 1.68 vs 1.95 (p=0.23)]. DDVH showed the AUC from IMRT to be slightly smaller than from VMAT [1.13 vs 1.15 (p=0.43)].Conclusion:VMAT plan robustness is comparable to IMRT plan robustness. The plan robustness conclusions from WCA and DVHB are DVH parameter dependent. On the other hand DDVH captures the overall effect of uncertainties on the dose to a volume of interest.NIH/NCI K25CA168984; Eagles Cancer Research Career Development; The Lawrence W. and Marilyn W. Matteson Fund for Cancer Research Mayo ASU Seed Grant; The Kemper Marley Foundation
SU‐E‐T‐625: Potential for Reduced Radiation Induced Toxicity for the Treatment of Inoperable Non‐Small‐Cell Lung Cancer Using RapidArc Planning
Authors: Pokhrel D , Sood S , Badkul R , Jiang H , Saleh H , Wang F 
Published: June 2015

Purpose:To investigate the feasibility of using RapidArc (RA) treatment planning to reduce irradiation volume of normal lung and other organs at risk (OARs) in the treatment of inoperable non‐small‐cell lung cancer (NSCLC) patients.Methods:A retrospective treatment planning and delivery study was performed to compare target coverage and the volumes of the normal lung, spinal cord, heart and esophagus on 4D‐CT scan above their dose tolerances delivered by RA vs. IMRT for ten inoperable NSCLC patients (Stage I‐IIIB). RA plans consisted of either one‐full or two‐partial co‐planar arcs used to treat 95% of the planning target volume (PTV) with 6MV beam to a prescription of 66Gy in 33 fractions. IMRT plans were generated using 5–7 co‐planar fields with 6MV beam. PTV coverage, dose‐volume histograms, homogeneity/conformity indices (CI), total number of monitor units(MUs), beam‐on time and delivery accuracy were compared between the two treatment plans.Results:Similar target coverage was obtained between the two techniques. RA (CI=1.02) provided more conformal plans without loss of homogeneity compared to IMRT plans (CI=1.12). Compared to IMRT, RA achieved a significant median dose reduction in V10 (3%), V20 (8%), and mean lung dose (3%) on average, respectively. On average, V5 was comparable between the two treatment plans. RA reduced mean esophagus (6%), mean heart (18%), and maximum spinal cord dose (7%), on average, respectively. Total number of MUs and beam‐on time were each reduced almost by a factor of 2 when compared to IMRT‐patient comfort, reduced intra‐fraction‐motion and leakage dose. The average IMRT and RA QA pass rate was about 98% for both types of plans for 3%/3mm criterion.Conclusion:Compared to IMRT plans, RA provided not only comparable target coverage, but also improved conformity, treatment time, and significant reduction in irradiation of OARs. This may potentially allow for target dose escalation without increase in normal tissue toxicity.
SU‐E‐T‐627: Precision Modelling of the Leaf‐Bank Rotation in Elekta's Agility MLC: Is It Necessary?
Authors: Vujicic M , Belec J , Heath E , Gholampourkashi S , Cygler J 
Published: June 2015

Purpose:To demonstrate the method used to determine the leaf bank rotation angle (LBROT) as a parameter for modeling the Elekta Agility multi‐leaf collimator (MLC) for Monte Carlo simulations and to evaluate the clinical impact of LBROT.Methods:A detailed model of an Elekta Infinity linac including an Agility MLC was built using the EGSnrc/BEAMnrc Monte Carlo code. The Agility 160‐leaf MLC is modelled using the MLCE component module which allows for leaf bank rotation using the parameter LBROT. A precise value of LBROT is obtained by comparing measured and simulated profiles of a specific field, which has leaves arranged in a repeated pattern such that one leaf is opened and the adjacent one is closed. Profile measurements from an Agility linac are taken with gafchromic film, and an ion chamber is used to set the absolute dose. The measurements are compared to Monte Carlo (MC) simulations and the LBROT is adjusted until a match is found. The clinical impact of LBROT is evaluated by observing how an MC dose calculation changes with LBROT. A clinical Stereotactic Body Radiation Treatment (SBRT) plan is calculated using BEAMnrc/DOSXYZnrc simulations with different input values for LBROT.Results:Using the method outlined above, the LBROT is determined to be 9±1 mrad. Differences as high as 4% are observed in a clinical SBRT plan between the extreme case (LBROT not modeled) and the nominal case.Conclusion:In small‐field radiation therapy treatment planning, it is important to properly account for LBROT as an input parameter for MC dose calculations with the Agility MLC. More work is ongoing to elucidate the observed differences by determining the contributions from transmission dose, change in field size, and source occlusion, which are all dependent on LBROT.This work was supported by OCAIRO (Ontario Consortium of Adaptive Interventions in Radiation Oncology), funded by the Ontario Research Fund.
SU‐E‐T‐630: Predictive Modeling of Mortality, Tumor Control, and Normal Tissue Complications After Stereotactic Body Radiotherapy for Stage I Non‐Small Cell Lung Cancer
Authors: Lindsay WD , Berlind CG , Gee JC , Simone CB 
Published: June 2015

Purpose:While rates of local control have been well characterized after stereotactic body radiotherapy (SBRT) for stage I non‐small cell lung cancer (NSCLC), less data are available characterizing survival and normal tissue toxicities, and no validated models exist assessing these parameters after SBRT. We evaluate the reliability of various machine learning techniques when applied to radiation oncology datasets to create predictive models of mortality, tumor control, and normal tissue complications.Methods:A dataset of 204 consecutive patients with stage I non‐small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT) at the University of Pennsylvania between 2009 and 2013 was used to create predictive models of tumor control, normal tissue complications, and mortality in this IRB‐approved study. Nearly 200 data fields of detailed patient‐ and tumor‐specific information, radiotherapy dosimetric measurements, and clinical outcomes data were collected. Predictive models were created for local tumor control, 1‐ and 3‐year overall survival, and nodal failure using 60% of the data (leaving the remainder as a test set). After applying feature selection and dimensionality reduction, nonlinear support vector classification was applied to the resulting features. Models were evaluated for accuracy and area under ROC curve on the 81‐patient test set.Results:Models for common events in the dataset (such as mortality at one year) had the highest predictive power (AUC = .67, p < 0.05). For rare occurrences such as radiation pneumonitis and local failure (each occurring in less than 10% of patients), too few events were present to create reliable models.Conclusion:Although this study demonstrates the validity of predictive analytics using information extracted from patient medical records and can most reliably predict for survival after SBRT, larger sample sizes are needed to develop predictive models for normal tissue toxicities and more advanced machine learning methodologies need be consider in the future.
SU‐E‐T‐634: Pre‐Verification of FFF Prostate VMAT Plans with Gamma Method and DVHs Reconstructed Based On Measurements with 2D‐ARRAY (PTW 1500) and OCTAVIUS 4D
Authors: Kruszyna M , Adamczyk M 
Published: June 2015

Purpose:The aim of this work was to characterize the clinical correctness of FFF prostate treatment VMAT plans based on analysis of DVHs reconstructed from pre‐verification 2D‐arrays measurements.Methods:The new 2D ion chamber array 1500 with rotational phantom cylindrical Octavius 4D and Verisoft 6.1 software with DVH option (PTW, Freiburg) were used to determine the clinical usefulness of the treatment plans. Ten patients treated with VMAT high‐fractionated (2 fraction × 7,5 Gy) FFF prostate plans (TrueBeam, Varian) were analyzed using the 3D gamma analysis by local dose method with a 5% threshold for various tolerance parameters DTA [mm] and DD [%] were 1%/1, 2%/2, 3%/3. Additional, based on the measurements of irradiation dose distributions and patients’ CT scans with contoured structures of organs, the DVHs were reconstructed using a software. The obtained DVHs were compared to planned dose distributions and the deviations were analysed with parameters: for CTV D50, D98, D2, and D25, D50, Dmax for OARs — rectum, bladder and left/right femoral heads.Results:The analyzed treatment plans passed gamma criteria (3/3%; 95%), the results obtained were as follow: mean value and standard deviation of gamma score for criteria (DTA[mm]/DD[%]): 1/1% (L53.3±3.2); 2/2% (L87.0±2.2); 3/3% (L97.5±0.9). In the DVH analysis, the highest differences were observed for OARs (especially for bladder): the mean percentage differences values for rectum, bladder and left/right femoral heads were: D25 (1.67; 6.83)%, D50 (0.18; 7.18; 1.53; 0.30)%, Dmax (−0.84; −1.64; 0.37; −4.63)%, respectively. For the CTV mean relative deviations for proper parameters were in good agreement with TPS: D98 (0.95±2.21)%, D50 (1.93±0.67)%, D2 (1.76±0.76)%.Conclusion:The gamma method is recommended tool for pre‐verification analysis of correctness of treatment plans. Moreover, the scrutiny checking with reconstructed DVH gives additional, clinical information about quality of plan, especially about coverage of CTV and sparing of health tissues.