bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐739: The Logistic Regression and Cox Regression Model for Predicting Local Recurrence, Distant Metastases, and Overall Survival of Rectal Cancer Patients
Authors: Zhou Z , Zhang Z , Hu W , Zhong H , Wang J 
Published: June 2015

Purpose:The purpose was to develop predicting models for the local recurrence, distant metastases, and overall survival for rectal cancer patients treated with chemoradiotherapy. These models were based on different statistical methods for indicating various relationships between clinical features and follow‐up results, which may provide support on decision‐making in treatment.Methods:Models were developed based on logistic regression and cox proportional hazards model using patient data (N=277) from Fudan University Shanghai Cancer Center. The patient data set was randomly split into two proportions as the training and validation datasets. The clinical features used as variables include sex, age, tumor location, RT dose, adjuvant chemotherapy, surgery procedure, clinical tumor stage, and pTNM stage. The Bootstrapping was used for constructing confidence intervals; and the model performance was evaluated by the concordance index (c‐index).Results:The logistic regression model is easy to use because the conditional independence assumption is unnecessary. The Cox regression model can dispose data with time factors so follow‐up over a certain time period can be predicted. For the logistic regression model, the c‐index for validation are 0.73 (LR), 0.77 (DM), and 0.76(OS), while numerical values for the cox regression model are 0.72 (LR), 0.77 (DM), and 0.70(OS). Both models show the probability to predict follow‐up events based on c‐index. Clinical tumor stage and pathologic stage are crucial features for both models (p<0.05).Conclusion:The Logistic Regression and Cox Regression Model can be used for Predicting Local Recurrence, Distant Metastases, and Overall Survival of Rectal Cancer Patients. The performance of models can be further improved with additional parameters provided from different facilities.
SU‐E‐T‐744: The Study of Total Marrow Irradiation Based On Rotational Intensity‐Modulated Techniques
Authors: Xu S , Xie C , Qu B , Yu W , Xu W , Ge R , Cong X 
Published: June 2015

Purpose:This study is to compare the dosimetric characteristics and efficiency of RapidArc and Tomotherapy in total marrow irradiation (TMI) for hematologic malignancies in order to get the reference data for the choice of clinical application.Methods:Eight patient plans were retrospectively designed and analyzed for RapidArc and Tomotherapy. Total bone morrow was contoured as clinical target volume excluding the cubitus and hand part, then plus a 3.0mm margin as planning target volume. The prescription was 12Gy in 10 fractions. ArcCHECK system was used for dose verification, and the safety and accuracy of clinical delivery would be evaluated.Results:It showed that the two techniques could well achieve the target coverage. The conformity indexes of RapidArc and Tomotherapy were 0.54±0.05 vs 0.52±0.07 (p=0.45), but Tomotherapy plans have a visible advantage over RapidArc plans in the dose uniformity of target. The homogeneity indexes were 0.19±0.02 vs 0.13±0.02 (p=0.00). Tomotherapy plans showed better in sparing of the critical organs apart from the whole brain, oral, parotid gland, the small intestine, rectum, and the maximum dose of lens of Tomotherapy plans was reduced by 41% comparing to RapidArc plans. The MUs and treatment delivery time of RapidArc and Tomotherapy were 2608MU/560s vs 12842MU/891s. The γ‐analysis passing rates for head‐neck, chest‐abdomen, pelvic were 98.9±1.9%, 98.4±1.8%, 97.4±2.1% for RapidArc and 94.3±1.5%, 96.5±1.2%, 94.1±1.9% for Tomotherapy plans.Conclusion:The two methods using RapidArc and Tomotherapy could achieve the acceptable dose of TMI, and the delivery efficiency of RapidArc was better than Tomotherapy. Two kinds of techniques are promising and can solve the clinic implementation of TMI.This work was supported in part by the grant from Chinese Natural Science Foundation (Grant No. 11105225).
SU‐E‐T‐752: Three‐Dimensional Carcinogenic Maps Induced by Photons and Protons
Authors: Manem V , Paganetti H 
Published: June 2015

Purpose:Evaluate the excess relative risk (ERR) induced by photons and protons in each voxel of the lung, and display it as a three‐dimensional map, known as the ERRM (i.e. excess relative risk map) along with the dose distribution map. In addition, we also study the effect of variations in the linear energy transfer (LET) distribution on ERRM for a given proton plan.Methods:The excess relative risk due to radiation is estimated using the initiation‐inactivation‐proliferation formalism. This framework accounts for three biological phenomenon: mutation induction, cell kill and proliferation. Cell kill and mutation induction are taken as a function of LET using experimental data. LET distributions are calculated using a Monte Carlo algorithm. ERR is then estimated for each voxel in the organ, and displayed as a three dimensional carcinogenic map.Results:The differences in the ERR's between photons and protons is seen from the three‐dimensional ERR map. In addition, we also varied the LET of a proton plan and observed the differences in the corresponding ERR maps demonstrating variations in the ERR maps depend on features of a proton plan. Additionally, our results suggest that any two proton plans that have the same integral dose does not necessarily imply identical ERR maps, and these changes are due to the variations in the LET distribution map.Conclusion:Clinically, it is important to have a three dimensional display of biological end points. This study is an effort to introduce 3D ERR maps into the treatment planning workflow for certain sites such as pediatric head and neck tumors.
SU‐E‐T‐753: Three‐Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code
Authors: Park M , Kim G , Ji Y , Kim K , Park S , Jung H 
Published: June 2015

Purpose:The purpose of this study is to estimate the three‐dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles.Methods:The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm3, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). The shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm3. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross‐sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability.Results:The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg‐peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation.Conclusion:The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg‐peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.
SU‐E‐T‐760: Tolerance Design for Site‐Specific Range in Proton Patient QA Process Using the Six Sigma Model
Authors: Lah J , Shin D , Kim G 
Published: June 2015

Purpose:To show how tolerance design and tolerancing approaches can be used to predict and improve the site‐specific range in patient QA process in implementing the Six Sigma.Methods:In this study, patient QA plans were selected according to 6 site‐treatment groups: head &neck (94 cases), spine (76 cases), lung (89 cases), liver (53 cases), pancreas (55 cases), and prostate (121 cases), treated between 2007 and 2013. We evaluated a model of the Six Sigma that determines allowable deviations in design parameters and process variables in patient‐specific QA, where possible, tolerance may be loosened, then customized if it necessary to meet the functional requirements. A Six Sigma problem‐solving methodology is known as DMAIC phases, which are used stand for: Define a problem or improvement opportunity, Measure process performance, Analyze the process to determine the root causes of poor performance, Improve the process by fixing root causes, Control the improved process to hold the gains.Results:The process capability for patient‐specific range QA is 0.65 with only ±1 mm of tolerance criteria. Our results suggested the tolerance level of ±2–3 mm for prostate and liver cases and ±5 mm for lung cases. We found that customized tolerance between calculated and measured range reduce that patient QA plan failure and almost all sites had failure rates less than 1%. The average QA time also improved from 2 hr to less than 1 hr for all including planning and converting process, depth‐dose measurement and evaluation.Conclusion:The objective of tolerance design is to achieve optimization beyond that obtained through QA process improvement and statistical analysis function detailing to implement a Six Sigma capable design.
SU‐E‐T‐765: Treatment Planning Comparison of SFUD Proton and 4Ï€ Radiotherapy for Prostate Cases
Authors: Tran A , Zhang J , Woods K , Yu V , Nguyen D , Sheng K 
Published: June 2015

Purpose:Single‐Field Uniform Dose (SFUD) proton scanning beams and non‐coplanar 4π intensity‐modulated radiation therapy (IMRT) represent the most advanced treatment methods based on heavy ion and X‐rays, respectively. Here we compare their performance for prostate treatment.Methods:Five prostate patients were planned using 4π radiotherapy and SFUD to an initial dose of 54Gy to a planning target volume (PTV) that encompassed the prostate and seminal vesicles, then a boost prescription dose of 25.2Gy to the prostate for a total dose of 79.2 Gy. 4π plans were created by inversely selecting and optimizing 30 beams from 1162 candidate non‐coplanar beams using a greedy column generation algorithm. The SFUD plans utilized two coplanar, parallel‐opposing lateral scanning beams. The SFUD plan PTV was modified to account for range uncertainties while keeping an evaluation PTV identical to that of the X‐ray plans for comparison. PTV doses, bladder and rectum dose volumes (V40, V45, V60, V70, V75.6, and V80), R50, and PTV homogeneity index (D95/D5) were evaluated.Results:Compared to SFUD, 4π resulted in 6.8% lower high dose spillage as indicated by R50. Bladder and rectum mean doses were 38.3% and 28.2% lower for SFUD, respectively. However, bladder and rectum volumes receiving >70Gy were 13.1% and 12% greater using proton SFUD. Due to the parallel‐opposing beam arrangement, SFUD resulted in greater femoral head (87.8%) and penile bulb doses (43.7%). 4π PTV doses were slightly more homogeneous (HI 0.99 vs. 0.98) than the SFUD dose.Conclusion:Proton is physically advantageous to reduce the irradiated normal volume and mean doses to the rectum and bladder but it is also limited in the beam orientations and entrance dose, which resulted in greater doses to the femoral heads and penile bulb, and larger volumes of rectum and bladder exposed to high dose due to the required robust PTV definition.This project is supported by Varian Medical Systems.
SU‐E‐T‐766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy
Authors: Zhang R , Xiaomei F , Bai W , Zhang X , Gao Y 
Published: June 2015

Purpose:To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques.Methods:Treatment plans were graded four (Low, Moderate, Moderate‐High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate‐High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X‐rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose.Results:Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate‐High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk.Conclusion:The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted.This work was supported by The Medical Science Foundation of The health department of Hebei Province (No. 20130253)
SU‐E‐T‐769: T‐Test Based Prior Error Estimate and Stopping Criterion for Monte Carlo Dose Calculation in Proton Therapy
Authors: Hong X , Gao H , Schuemann J , Paganetti H 
Published: June 2015

Purpose:The Monte Carlo (MC) method is a gold standard for dose calculation in radiotherapy. However, it is not a priori clear how many particles need to be simulated to achieve a given dose accuracy. Prior error estimate and stopping criterion are not well established for MC. This work aims to fill this gap.Methods:Due to the statistical nature of MC, our approach is based on one‐sample t‐test. We design the prior error estimate method based on the t‐test, and then use this t‐test based error estimate for developing a simulation stopping criterion. The three major components are as follows.First, the source particles are randomized in energy, space and angle, so that the dose deposition from a particle to the voxel is independent and identically distributed (i.i.d.).Second, a sample under consideration in the t‐test is the mean value of dose deposition to the voxel by sufficiently large number of source particles. Then according to central limit theorem, the sample as the mean value of i.i.d. variables is normally distributed with the expectation equal to the true deposited dose.Third, the t‐test is performed with the null hypothesis that the difference between sample expectation (the same as true deposited dose) and on‐the‐fly calculated mean sample dose from MC is larger than a given error threshold, in addition to which users have the freedom to specify confidence probability and region of interest in the t‐test based stopping criterion.Results:The method is validated for proton dose calculation. The difference between the MC Result based on the t‐test prior error estimate and the statistical Result by repeating numerous MC simulations is within 1%.Conclusion:The t‐test based prior error estimate and stopping criterion are developed for MC and validated for proton dose calculation.Xiang Hong and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500).
SU‐E‐T‐770: Tumor Control in Ion Beam Radiotherapy with Different Ions in Presence of Hypoxia
Authors: Attili A , Torriani F , Russo G , Dalmasso F , Giordanengo S , Ourhaleb F , Battistoni G , Kraan A , Cirio R 
Published: June 2015

Purpose:The reduced concentration of oxygen in cells (hypoxia) results in a lower cell death rate after irradiation that can lead to treatment failure. The effect can be expressed by the oxygen enhancement ratio (OER). So far, only few attempts to include OER in treatment planning for ion beam therapy were made, which are based on the dose averaged LET estimates and do not distinguish among ion species and fractionation schemes. To overcome these limitations, we implemented a new OER model and used it to estimate tumor control in clinical cases.Methods:The model, based on the microdosimetric kinetic model, was benchmarked with in‐vitro data from different ions irradiation. It was included in the simulation of treatments of a set of clinical cases (glioblastoma) using p, Li, He, C and O ion beams. Tumor Control Probability (TCP) was estimated as a function of oxygen partial pressure, dose per fraction and primary ion type.Results:The modelized OER was found to be strongly dependent on both LET and ion type, and showed a decreasing OER for increasing dose per fraction with a slope that depends on the LET and ion type, in good agreement with the experimental data. In the clinical cases studied, an increase in TCP by increasing ion charge and dose per fraction (more than 30% variation from p to O for moderate hypoxia) was found. Higher OER decrease rates as function of dose per fraction were found for lighter ions (up to 20% varying from 2 to 8 Gy(RBE)).Conclusions:A novel modeling of the OER that explicitly includes the dependence on ion type and dose per fraction was implemented. The model was exploited to evaluate the impact of hypoxia in ion beam radiotherapy, facilitating the identification of the treatment condition optimality, including fractionation scheme and ion type.
SU‐E‐T‐771: Two Dimensional Raman Mapping of Carbon Bonds of Radiochromic Films: An Approach to Micro‐Dosimetry
Authors: Heo T , Ye S 
Published: June 2015

Purpose:To study a feasibility of micro‐dosimetry with high dose‐sensitivity and resolution using two‐dimensional Raman mapping on the basis of carbon bonds concentration of radiochromic filmsMethods:Unlaminated EBT3 films with the purpose of maximal Raman data acquisition were irradiated by 6 MV beam from 5 MU to 1000 MU at the reference condition. Each film was irradiated with shielding material of lead blocking on the half of film as well as the jaw open in half for distinct dose contrast. Raman peaks of 2070 cm‐1, 2095 cm‐1, and 2115 cm‐1 were major subjects to study, which are assumed to be the spectroscopy of carbon triple bonds of monomers, carbon double bonds of polymers, and carbon triple bonds of polymers, respectively. Laser exposure for Raman spectroscopy generated peak's trend due to polymerization by laser output and this trend was utilized to find out basic peaks related to polymerization process. The relative dose contrast in each one film was detected by Raman spectroscopy with the aid of an auto‐scanning stage, comparing the dose contrast between non‐irradiated area and irradiated area. Raman spatial resolution was enhanced up to 20 micrometers, assuming the spatial uniformity of radio¬active rod‐shaped LiPCDA crystals. An optical scanner with 9600 dpi was used to scan the red‐channel intensity to read the dose contrast for 5 MU delivered film.Results:The peak intensity for Raman wavenumber of 2070 cm‐1 was used for mapping since it reflected the different peak intensities based on polymerization degree by irradiation. Dose contrast from 1000MU to 5 MU was distinguished by Raman mapping analysis, whereas optical intensity of red‐channel didn't show any difference.Conclusion:In consideration of laser effect, the quantitative analysis based on raw data of Raman mapping could provide more statistically reliable dosimetry than point measurements.
SU‐E‐T‐775: Use of Electronic Portal Imaging Device (EPID) for Quality Assurance (QA) of Electron Beams On Varian Truebeam System
Authors: Cai B , Yaddanapudi S , Sun B , Li H , Noel C , Mutic S , Goddu S 
Published: June 2015

Purpose:In a previous study we have demonstrated the feasibility of using EPID to QA electron beam parameters on a single Varian TrueBeam LINAC. This study aims to provide further investigation on (1) reproducibility of using EPID to detect electron beam energy changes on multiple machines and (2) evaluation of appropriate calibration methods to compare results from different EPIDs.Methods:Ad‐hoc mode electron beam images were acquired in developer mode with XML code. Electron beam data were collected on a total of six machines from four institutions. A custom‐designed double‐wedge phantom was placed on the EPID detector. Two calibration methods ‐ Pixel Sensitivity Map (PSM) and Large Source‐to‐Imager Distance Flood Field (LSID‐FF) ‐ were used. To test the sensitivity of EPID in detecting energy drifts, Bending Magnet Current (BMC) was detuned to invoke energy changes corresponding to ∼±1.5 mm change in R50% of PDD on two machines from two institutions. Percent depth ionization (PDI) curves were then analyzed and compared with the respective baseline images using LSID‐FF calibration. For reproducibility testing, open field EPID images and images with a standard testing phantom were collected on multiple machines. Images with and without PSM correction for same energies on different machines were overlaid and compared.Results:Two pixel shifts were observed in PDI curve when energy changes exceeded the TG142 tolerance. PSM showed the potential to correct the differences in pixel response of different imagers. With PSM correction, the histogram of images differences obtained from different machines showed narrower distributions than those images without PSM correction.Conclusion:EPID is sensitive for electron energy changes and the results are reproducible on different machines. When overlaying images from different machines, PSM showed the ability to partially eliminate the intrinsic variation of various imagers.Research Funding from Varian Medical Systems Inc.Dr. Sasa Mutic receives compensation for providing patient safety training services from Varian Medical Systems, the sponsor of this study.