bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐680: Comparison between XVMC Monte Carlo and Eclipse AAA Dose Calculations for Rapidarc Plans
Authors: Laub W 
Published: November 2011

Purpose: To investigate the dose calculation accuracy of the Eclipse AAA dose calculation algorithm for Rapidarc treatment plans by means of recalculating Rapidarc plans with the fast Monte Carlo code XVMV.Methods: The fast Monte Carlo code XVMC was commissioned for a Trilogy linear accelerator (Varian, Palo Alto) with a 6x photon beam. Dose calculation tests with XVMC in solid water demonstrated the high accuracy of the beam model for different field sizes compared to measurements and calculations with the clinically commissioned AAA algorithm in Eclipse (Varian, Palo Alto). Dose calculations for conventional treatment plans in the absence of large areas of high or low density inhomogeneities for 3D conformal treatment plans, like 4‐field pelvis plans, also demonstrated a high level of agreement. Clinical Rapidarc treatment plans of prostate and H&N cases were recalculated with XVMC.Results: Comparison between AAA and XVMC dose calculations of Rapidarc plans show differences in the presence of inhomogeneities as they have already been discussed in a variety of publications comparing AAA or Collapsed Cone calculations with Monte Carlo results. In addition we found that the overall dose is overestimated in Eclipse by several Gray (see Fig. 2). A typical prostate or H&N plan will show a dose of 3–4 Gy less in the XVMC dose calculation compared to AAA calculations Conclusions: This work indicates that in addition to the well known limitations of AAA or Collapsed Cone algorithms with respect to how they handle and correct for lateral electron scatter and electron disequilibrium the accuracy of absolute dose calculations with AAA may also be limited in Rapidarc treatment planning. This can be explained with the extremely small islands of dose and the high percentage of area blocked by the MLCs as it can often be observed for control point of Rapidarc treatment plans.The author of this abstract holds a Varian research grant, is a guest speaker for Brainlab and has a part‐time commitment with Computerized Medical Systems.
SU‐E‐T‐687: Experimental Assessment of the Accuracy of a Semi‐Empirical Model and a Monte Carlo System for Proton Dose Calculations for Highly Inhomogeneous Media
Authors: Mohan R , Mirkovic D , Titt U , Song X , Li H , Zhu X , Gillin M 
Published: November 2011

Purpose: To experimentally assess the accuracy of proton dose distributions, computed with a semi‐empirical algorithm and a Monte Carlo (MC) system, for inhomogeneous media. Methods: A complex range compensator for a lung patient, being treated with passively‐scattered proton therapy (PSPT) was used to represent the inhomogeneity. Planar dose distributions for a PSPT beam of exactly the same characteristics as the one used to treat the patient, incident normally on a water equivalent phantom, were measured at a series of depths using a calibrated chamber array detector. Semi‐empirical algorithm and MC (MCNPX) calculations were performed with exactly the same geometry. Absolute depth doses and lateral profiles at multiple depths were compared. Results: Agreement between MC and measured depth dose data was found to be within 2% or 2 mm except at the distal edge where the dose gradient was the highest. The corresponding differences between measurements and the semi‐empirical model were up to 5% in the regions of low gradients and distance to agreement in the distal edge region exceeded 1 cm. Comparison of measured vs. MC vs. se‐empirical profiles showed that, in some regions measured data agreed better with MC, whereas in other regions the agreement was better with semi‐empirical model. Generally, the agreement within the beam boundary was superior for measured vs. MC. The gamma analysis (points within 3% and 3 mm) indicated that the percentage of points passing was comparable for both modes of calculations. Conclusions: The differences between measured and semi‐empirical model dose distributions might be explainable based on the approximations in the latter. However, differences between measurements and MC require further examination of numerous sources of uncertainties, e.g., in modeling of beams and compensators, and the measurements (e.g., the depth of sensitive region of the chamber).NCI P01CA021239
SU‐E‐T‐688: McCloud: Toward 10 Million Monte Carlo Primaries in 5 Minutes for Clinical Use
Authors: Keyes R , Arnold D , Reynaud A , Luan S 
Published: November 2011

Purpose: At AAPM 2010, we presented the concept of using Cloud Computing to speed up clinical Monte Carlo calculations. Cloud Computing refers to a set of technologies that offers on‐demand computing resources using a pay‐as‐you‐go pricing model. We presented a feasibility study that included a variety of clinical relevant calculations using protons, electrons, and photons in water and a voxel patient geometry (Zubal phantom). While our initial study was designed for proof‐of‐concept, this research presents a more refined platform with an emphasis on particle therapy and demonstrates its potential to enable Monte Carlo dose calculation for routine clinical use.Methods: A Cloud Computing based distributed Monte Carlo dose calculation system called McCloud was developed. The system is based on Amazon EC2, Fluka, and a variety of “glue” technologies. The calculation involves these key steps: (1) A cluster is allocated in the Cloud. (2) A Monte Carlo task is launched on each node in the cluster. Extra care is used for random seed generations to ensure the correctness of the simulations. (3) The progress of the computation is dynamically monitored. (4) Once the computation is finished in the cluster, the results are aggregated using a linear model or a tree‐based distributive model, and a final dose distribution is returned to the user. Results: We found that for 14 Million 75MeV protons, an analog Monte Carlo simulation can be completed in 5 minutes 36 seconds. For this particular computation, the cost is less than 2 USD (based on official pricing at 8 cents per node per hour). Studies using various cluster sizes have shown the 1/n speed up expected from analytical Monte Carlo simulations Conclusions: Our implementations demonstrate the power of the existing cloud computing model, an extremely promising new paradigm for clinical and research computing. Further research is underway.Supported in part by NSF CBET‐0853157 and NSF CBET‐0755054.
SU‐E‐T‐690: Fast Monte Carlo Treatment Planning for Prostate Brachytherapy: A Comparison with VariSeed
Authors: Abboud F , Scalliet P , Vynckier S 
Published: November 2011

Purpose: Treatment planning for prostate Brachytherapy with seeds uses mainly the TG43 algorithm for dose calculations. It doesnˈt take into account the interseed attenuations (known as the interseed effect) due to its complexity. A fast Monte Carlo dose calculation engine, taking into account the interseed effect, has been developed, using the MCNP5 code. Methods: Three MC techniques were used to calculate the dose distributions of the prostate implants: MCOSST, FMCT and MCOSSIT. The two last techniques take into account the interseed effect. IsoSeed (Bebig) seeds were chosen for this work. A 3D comparison has been performed to validate the new MC techniques for 8 patients. Dose distributions are compared on each ultrasound imaging slide. Moreover, a DVH comparison is also performed for some organs. Results: The interseed effect was investigated by comparing MCOSST with FMCT. It leads to the appearance of cold spots in the planar dose distribution which varies from 4% to 6%. It depends on number, position and composition of seeds. Moreover, the interseed effect becomes more important as the number of implanted seeds increases. We can especially notice it at the end of the strand and also behind set of seeds implanted each 5 mm in the same plane. DVH comparison between VariSeed and MC techniques was also performed. VariSeed overestimates the average dose deposited in the prostate by 3% up to 5%. MCOSSIT can be considered being a more accurate and faster (2–3 sec) calculation method in a near future as it taks into account the interseed effect and can also be applied on line Conclusions: MCOSSIT is a new calculation technique of dose distribution for prostate Brachytherapy that can be used for all types of seeds. All these advantages make from MCOSSIT very accurate and fast system for online permanent brachytherapy of the prostate.This work is submited by UCL University to get a patent.
SU‐E‐T‐708: Validation of the New GATE 6.0 Monte Carlo Platform for Radiation Therapy. Investigations on Simulation Parameters
Authors: Perrot Y , Donnarieix D , Breton V , Maigne L 
Published: November 2011

Purpose: In this study, we validate the accuracy of the new GATE 6.0 Monte Carlo platform (using GEANT4 9.2 Standard Electromagnetic Physics Package) to model accurate treatment plans in radiation therapy using 18 MV photon beams. Furthermore, we investigate how the specifications of the particle transport management, physic processes and geometry influence the dosimetric accuracy of the results to propose recommendations on the usage of GATE 6.0. Methods: 3D conformational plans were simulated for a lung irradiation using 18MV photon beams from a Varian Clinac 2100C accelerator. The patient volume was derived from CT images and converted into specific format in order to use different voxel sizes. Treatment plans were computed using GATE 6.0 and EGSnrc. Treatment plans obtained with both of the codes were compared using a gamma index evaluation (acceptance criteria 3%/3mm). Investigations on the influence of simulation parameters related to physics or algorithm were examined by qualitative comparisons of DVHs in several regions of interest: PTV and OARs. Results: At first, GATE 6.0 is able to reproduce complex dosimetry in agreement with the well validated Monte Carlo code EGSnrc. Nevertheless, the choice of specific simulation parameters such as cuts, particle production threshold or stepping algorithm showed differences on treatment plans. Users have to fix parameters according to the geometry simulated to ensure a good tracking of particles by taking into account the computation time efficiency. Conclusions: GATE 6.0 provides convivial tools for realistic treatment planning and give comparable results with EGSnrc while the parameters of the simulation are well fixed. These investigations highlight several issues of general interest to users of GATE 6.0 who wish to calculate accurate treatment plans.We wish to thank the GEANT4 collaboration and the OpenGATE collaboration to their scientific and technical suuport.This work was partly supported by grants from the European Commission (through the EGI inititative project), by the French National Grid Inititative (France Grilles), and regional authorites (Conseil Général de lˈAllier and Conseil Régional dˈAuvergne).
SU‐E‐T‐795: Measuring Uncertainty in Dose Delivered to the Cochlea Due to Setup Error during External Beam Treatment of Patients with Cancer of the Head & Neck
Authors: Yan M , Lovelock D , Hunt M , Mechalakos J , Hu Y , Pham H , Jackson A 
Published: November 2011

Purpose: To understand the relationship between hearing loss and cochlea dose in patients treated for cancers of the head and neck with external beam IMRT, uncertainties in planned and delivered cochlea doses must be known. We use treatment cone beam scans to determine the positional and dosimetric uncertainty for the cochlea. Methods: Data from 6 head & neck patients with 6 planning CT and 29 Cone Beam CTs taken at time of treatment are used in this study. Patients were treated 70 Gy to the primary target, and between 50–60 Gy to nodal and sub‐clinical disease using IMRT dose painting. We use 6 dimensional rigid body registration to find translational and rotational setup error between the planning CT and Cone Beam CT scans. The Planning CT is rotated and translated so that the cochlea positions match those seen in the cone beam scans and cochlea doses recalculated. Results: We found most probable value of the magnitude of mean error in cochlea position is 0.25&#61617;0.02cm, but it can increase to 7mm in some patients. Uncertainty in the dose to cochlea depends on each treatment plan and relative positions of the cochlea and target volumes. Most of differences in doses to cochlea in our study are around 2% of planned dose. But for some patients this may be as large as 5–9%. Conclusions: Patient setup error introduces uncertainty in the position of the cochlea. Consequent uncertainties in dose heavily depends on the relative position of cochlea w.r.t. the target volumes and the individual treatment plan. Results from this study will be used to model the uncertainty in the dose response of hearing loss.This research is supported in part by NIH under RO1‐CA129182.
SU‐E‐T‐807: Measured Data Set for Validation of Bolus Electron Conformal Therapy
Authors: Kavanaugh J , Chu C , Perrin D , Hogstrom K 
Published: November 2011

Purpose: To measure sample planes of two 3D dose distributions that can be used to evaluate the accuracy of planning and delivery of bolus electron conformal therapy (ECT). Method: The planning target volumes (PTV) from a parotid and a chest wall patient were modified to a CT image set of a cylindrical polystyrene phantom. A bolus ECT plan for each PTV was developed using .decimal p.d software to design a custom bolus and dose was calculated using Pinnacle. Once acceptable, .decimal fabricated the bolus from machinable wax. Approximately 45 cGy given dose was delivered for each bolus ECT plan, and planar dose measurements were taken in the mid‐sagittal and five transverse phantom planes (±5cm, ±2.5cm, 0cm) using Kodak XV radiographic film sealed within the in‐phantom cassettes. Films were developed and digitized to (0.5mm pixels) using a Vidar DosimetryPRO Advantage, and converted to dose using a film calibration curve created at the time of measurement. Four film measurements were taken in each plane, with the mean dose and standard error being determined at each pixel. The precision of the data was quantified in the low gradient regions (Dose > 90% and Dose <10%) by the mean percent standard error of all pixels and in the high gradient region (90% > Dose > 10%) by the mean distance to dose agreement. Results: The percent average standard errors in the low gradient, high dose region were less than 1.5% for parotid and chest wall measurements and less than 3% in the low gradient, low dose regions. Average distances to agreement in the high gradient region were less than 0.6 mm. Conclusions: For two PTVs bolus, ECT dose distributions in 6 planes were measured and their precision quantified for three dose regions. These data are well‐suited for comparison with calculated electron dose distributions.This work was supported in part by a research grant from .decimal, Inc.
SU‐E‐T‐841: The Potential of Probablistic Optimization for Tumor Motion with IMRT
Authors: Kissick M , Flynn R , Mackie T , Mo X , Zhao D , Campos D , Yan Y 
Published: November 2011

Purpose: To demonstrate the feasibility of using probabilistic optimization for helical tomotherapy (HT) treatment planning of intrafraction moving targets: an alternative to motion management by active tracking. Methods: Realistic but regular purely transverse elliptical motion was produced with the Washington University 4D Motion Phantom to supplement previous work that contained either transverse and longitudinal or just longitudinal motions with varying amount of randomness and drifts. Dose perturbations due to motion were measured with Gafchromatic EBT film. A small (12cm diameter, 12 cm long) Virtual WaterTM cylindrical phantom is used in a Hi‐Art IITM (TomoTherapy Inc., Madison, WI) HT device. The treatment plan consists of a 9 cm ring target (98% gets the prescribed dose) with a 4 cm diameter central avoidance region (gets half the prescribed dose on average) for 9 cm along the length of the cylinder. Results: The transverse motion needs to be much larger than average transverse respiratory motions for lung tumors for the motion to cause unacceptable blurring. This and other studies demonstrate that HT is robust to breathing motion interference with the beamlet modulation, but care must be taken in the longitudinal direction for irregular breathing with a low frequency drift that interferes with the couch motion. Within the target, less than a 1% dose perturbation is observed between 0.10 < (gantry period)/(breathing period) < 10. Conclusions: With reasonable care to approximately regularize the patientˈs breathing, the dose distribution exhibits a dominantly ‘blurred’ response to the motion, so a single motion probability distribution function (pdf) can approximate the respiratory motion well enough to enable the use of probabilistic optimization. HTˈs delivery over multiple gantry rotations and patient breathing cycles enables sufficient dose smoothing for probabilistic optimization to apply to hypofractionated HT deliveries.The author, T. Mackie, has ownership interests in TomoTherapy, Inc., which is commercializing helical tomotherapy. This work was funded by NIH/NCI K25 CA119344.
SU‐E‐T‐846: Considering Marker Visibility during Planning Optimization for Dynamic Intensity‐Modulated Radiation Therapy
Authors: Zhao B , Dai J 
Published: November 2011

Purpose: To retrospectively compare different topogram‐based patient body size indices and to determine if attenuation‐area product (AAP) is more accurate as a basis for optimizing scan protocol and minimizing patient dose in body CT of adults. Method: Thirty‐seven non‐contrast CT scans of thorax or abdomen exam were studied retrospectively, with patient age ranges from 21 to 67 years old. The individual patient body attenuation of the scanned region was computed from reconstructed images as the gold standard, after first converting image pixel values from HU values to &#956;a values (&#956; is the attenuation coefficient and a is the area per pixel). Four topogram‐based body size indices (diameter (D), girth (G), projection area (sqrtPA), and AAP) were computed and compared to the gold standard using regression analysis. D was calculated by averaging the coronal and sagittal diameters, G by modeling the patient cross‐section as an ellipsoid, sqrtPA as the square root of the summation of the detector channel data. AAP was computed by multiplying the sqrtPA by the area per pixel, after accounting for patient mis‐centering, table attenuation, scanner geometry and detector pitch angle. The goodness of fitted linear models in correlation with gold standard was described by 95% confidence intervals (CIs). Results: Regression analysis resulted in different linear models. Preliminary results showed diameter and girth were similar in correlation with patient body attenuation with 95% CIs of ±2.8cm and 3.1cm. PA was better than both D and G; however, AAP was most accurate with a 95% CI of 1.3cm. At this time, we are analyzing more patient data sets. Conclusion: AAP may potentially be an automated, accurate patient size index as a basis for protocol optimization and dose minimization in adult body CT. Patient mis‐centering and pixel area corrections are critical for accurately estimating patient body size from topograms.This research work was funded by National Natural Science Foundation of China (Grant No. 10975187)
SU‐E‐T‐849: Optimal Sequencing to Reduce Treatment Time while Improving the Quality of Intensity‐Modulated Brachytherapy with Fixed‐Angular Fan‐Beams
Authors: Liu Y , Flynn R , Kim Y , Wu X 
Published: November 2011

Purpose: To develop an optimal shield‐sequencing algorithm and evaluate its feasibility of a rotating shield intensity shield intensity modulated brachytherapy (RS‐IMBT) with a fixed emission angle.Methods: We use an electronic brachytherapy source (Xoft Axxent) with a tungsten (gold) partial‐shield, and test a range of emission angle (32 ∼ 76). Large tumor (>= 40cc) at BT was tested for cervical cancer. In shielding sequencing optimization, a nontrivial network transformation scheme was utilized which makes the global optimum is efficiently achieved with the shortest path and network flow algorithms. We employed the objectives that based upon GEC‐ESTRO recommendations. D90 of high risk CTV receives a prescription dose (Rx) while organs‐at‐risk (OAR: rectum & sigmoid (bladder) D2cc <=75 (90) EQD2 (equivalent dose in 2Gy fraction) Gy from external beam radiotherapy and BT. The feasibility was tested using the metric of plan conformality (D90 in high risk CTV and D2cc in OAR) and treatment delivery time. Results: The shielding sequencing algorithm improves significantly tumor coverage (D90) with favor OAR sparing in an acceptable delivery time increase. The D90 (100% Rx) was improved from 41% Rx from conventional, Point‐A plan. D2cc of OAR was kept under the recommended limits. The increase of delivery time was recorded as less than 5 times higher when 72 degree emission angle and with unshielded source combined. Optimization time was less than 2 seconds. Conclusion: Globally optimal shielding‐sequencing with beamlets overlapping significantly improves tumor coverage of high risk CTV for large tumor without compromising OAR sparing but with less than 5 times delivery time increase. RS‐IMBT technique shows promising approach for large, non‐isotropic shape tumor that is currently investigated using intracavitary plus interstitial approach or performed by conventional interstitial technique.The research was supported, in part, by NIH grants R01‐EB004640 and K25‐CA123112, andNSF grants CCF‐0830402 and CCF‐0844765.
SU‐E‐T‐855: The Correlation Analysis of IMRT Dosimetry Errors and Parameters of Beams
Authors: Liu D , Chi Z , Cao Y , Li R , Han C 
Published: November 2011

Purpose: To study the relationships of IMRT plansˈ beam characteristic parameters, furthermore in order to research the effect of parameters settings on the absolute dose accuracy. Methods: Forty‐three esophageal carcinoma cases were planned with the Pinnacle 7.6c TPS using appropriate optimization parameters and dose constraints. All the plans were transplanted into solid water phantom. DOSE1 dosimeter and 0.13cc ion Farmer Chamber (IBA Corp) were used to measure the absolute dose and obtained the dosimetry errors later. The parameters of the 43 casesˈ statistics were collected, and their relations were analyzed. Then we summarized the dosimetry errors, made comparison and analyzed the relativity between the beam parameters and absolute dose verification errors. Results: 1. The describing parameters of beams feature were related. (1) Beam numbers were significantly correlated with beam segment numbers and total MUs, both p‐values were equal to 0.000, but were not distinctly connected with average beam segment numbers and average MUs. (2) Beam segment numbers were prominently interrelated with average beam segment numbers, total MUs and average MUs. (3) Average beam segment numbers were negatively correlated with average MUs and the statistical correlation coefficient was −0.358, yet had no relationship with total MUs. (4) The relationship between total MUs and average MUs was significantly correlated, and the p‐value was 0.003. 2. There was an obvious interrelation between dose accuracy and parameter settings, all of the p‐values were almost 0.000. Dose deviation was positively correlated with the total number of fields, segments, MUs and average segment numbers, while was negatively connected with average MUs.Conclusions: For the purpose of decreasing the absolute dose verification errors, the quantity of beam angles and beam segments should be reduced, considered the aspect of the designing of treatment plans.