bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Fluid Dynamics Evaluations of Unconventional Film Cooling Scaling Parameters on a Simulated Turbine Blade Leading Edge
Authors: Rutledge James L. , Polanka Marc D.
Published: July 2014

While it is well understood that certain nondimensional parameters, such as freestream Reynolds number and turbulence intensity, must be matched for proper design of film cooling experiments; uncertainty continues on the ideal method to scale film cooling flow rate. This debate typically surrounds the influence of the coolant to freestream density ratio (DR) and whether mass flux ratio or momentum flux ratio properly accounts for the density effects. Unfortunately, density is not the only fluid property to differ between typical wind tunnel experiments and actual turbine conditions. Temperature differences account for the majority of the property differences; however, attempts to match DR through the use of alternative gases can exacerbate these property differences. A computational study was conducted to determine the influence of other fluid properties besides density, namely, specific heat, thermal conductivity, and dynamic viscosity. Computational fluid dynamics (CFD) simulations were performed by altering traditional film cooling nondimensional parameters as well as others such as the Reynolds number ratio, Prandtl number ratio, and heat capacity ratio (HCR) to evaluate their effects on adiabatic effectiveness and heat transfer coefficient. A cylindrical leading edge with a flat afterbody was used to simulate a turbine blade leading edge region. A single coolant hole was located 21.5 deg from the leading edge, angled 20 deg to the surface and 90 deg from the streamwise direction. Results indicated that thermal properties can play a significant role in understanding and matching results in cooling performance. Density effects certainly dominate; however, variations in conductivity and heat capacity can result in 10% or higher changes in the resulting heat flux to the surface when scaling ambient rig configurations to engine representative conditions.
Multiple Mode Spatial Vibration Reduction in Flexible Beams Using H2- and H∞-Modified Positive Position Feedback
Authors: Omidi Ehsan , Nima Mahmoodi S.
Published: July 2014

This paper develops H2 modified positive position feedback (H2-MPPF) and H∞-MPPF controllers for spatial vibration suppression of flexible structures in multimode condition. Resonant vibrations in a clamped–clamped (c–c) and a cantilever beam are aimed to be spatially suppressed using minimum number of piezoelectric patches. These two types of beams are selected since they are more frequently used in macro- and microscale structures. The shape functions of the beams are extracted using the assumed-modes approach. Then, they are implemented in the controller design via spatial H2 and H∞ norms. The controllers are then evaluated experimentally. Vibrations of multiple points on the beams are concurrently measured using a laser vibrometer. According to the results of the c–c beam, vibration amplitude is reduced to less than half for the entire beam using both H2- and H∞-MPPF controllers. For the cantilever beam, vibration amplitude is suppressed to a higher level using the H2-MPPF controller compared to the H∞-MPPF method. Results show that the designed controllers can effectively use one piezoelectric actuator to efficiently perform spatial vibration control on the entire length of the beams with different boundary conditions.
SU‐E‐T‐329: Tissue‐Equivalent Phantom Materials for Neutron Dosimetry in Proton Therapy
Authors: Halg R , Clarke S , Wieger B , Pryser E , Arghal R , Pozzi S , Bashkirov V , Schneider U , Schulte R , Lomax A
Published: July 2014

Purpose:

To characterize tissue equivalence of phantom materials in terms of secondary neutron production and dose deposition from neutrons produced in radiation therapy phantom materials in the context of proton therapy using Monte Carlo simulations and measurements.

Methods:

In order to study the influence of material choice on neutron production in therapeutic proton beams, Monte Carlo simulations using the Geant4 and MCNPX‐PoliMi transport codes were performed to generate the neutron fields produced by protons of 155 and 200 MeV. A simple irradiation geometry was used to investigate the effect of different materials. The proton beams were stopped in slab phantoms to study the production of secondary neutrons. The investigated materials were water, Lucite, and tissue‐equivalent phantom materials (CIRS Inc., Norfolk, VA). Neutron energy spectra and absorbed dose by neutrons and their secondary particles were scored. In addition, simulations were performed for reference tissues (ICRP/ICRU) to assess tissue equivalence with respect to neutron generation and transport. In order to benchmark the simulation results, measurements were performed with a system developed at the University of Michigan; organic liquid scintillators were used to detect the neutron emissions from the irradiation of tissue‐equivalent materials. Additionally, the MPPost code was used to calculate the scintillator response from the MCNPX‐PoliMi output.

Results:

The simulated energy spectra and depth dose curves of the neutrons produced in different phantom materials showed similar shape. The differences of spectra and fluences between all studied materials and reference tissues were well within the achievable precision of neutron dosimetry. The shape of the simulated detector response of the liquid scintillators agreed well with measurements on the proton beamline.

Conclusion:

Based on Geant4 and MCNPX‐PoliMi simulations, the investigated materials appear to be suitable to study the production of neutrons in proton therapy. MC simulations were verified with neutron measurements in therapeutic proton beams.

This work was funded in part by the ANDANTE grant of the European Commission in the 7th Framework Program.
SU‐E‐T‐336: Transition From Frame Based SRS to Frameless SRS Procedures: A Community Based Hospital Experience
Authors: Workie D , Hasson B , Geraghty C
Published: July 2014

Purpose:

The project intent is to transit from frame based SRS to frameless SRS procedure and workflow in a community hospital setting.

Methods:

The clinic has strong experience in a wide verity of frame based SRS procedures using Novalis 600N linac equipped with BrainLab Micro‐MLC and ExacTrac systems. The addition of new Novalis TX system has opened an opportunity to explore and implement frameless SRS treatment procedure. Phantom End to End studies were performed for this purpose. A calibrated Ionization Chamber was inserted into the phantom and the phantom was positioned on the CT scan couch and SRS immobilization mask was made. A CT scan of the Immobilized phantom was generated with the localization box in place. The CT scan was localized and the ionization Chamber active volume was contoured as a target on the IPlan planning system. A 5 Dynamic Conformal Arcs plan was generated on the Iplan planning system. The Phantom was positioned on the treatment Couch with the SRS Mask and frameless array system in place, and the initial target treatment ISO position was achieved. The chamber was then connected to an electrometer. The two Orthogonal KV images were taken and the final treatment position was achieved within 1mm and 1 degree using ExacTrac. The Five arcs were delivered and the electrometer reading was noted. In addition, RPC SRS head phantom study was performed following RPC procedure.

Results:

The average absolute dose delivered to the in‐house phantom target was in agreement within 1.5% of the planning dose. The RPC SRS phantom results were within the criteria set by RPC.

Conclusion:

This work gave the confidence to our clinic to move from invasive frame based to non invasive and efficient frameless SRS and SRT treatments. The clinic has now frameless SRS and SRT treatment procedures and workflow.
SU‐E‐T‐337: Treatment Planning Study of Craniospinal Irradiation with Spot Scanning Proton Therapy
Authors: Tasson A , Beltran C , Laack N , Childs S , Tryggestad E , Whitaker T
Published: July 2014

Purpose:

To develop a treatment planning technique that achieves optimal robustness against systematic position and range uncertainties, and interfield position errors for craniospinal irradiation (CSI) using spot scanning proton radiotherapy.

Methods:

Eighteen CSI patients who had previously been treated using photon radiation were used for this study. Eight patients were less than 10 years old. The prescription dose was 23.4Gy in 1.8Gy fractions. Two different field arrangement types were investigated: 1 posterior field per isocenter and 2 posterior oblique fields per isocenter. For each field type, two delivery configurations were used: 5cm bolus attached to the treatment table and a 4.5cm range shifter located inside the nozzle. The target for each plan was the whole brain and thecal sac. For children under the age of 10, all plan types were repeated with an additional dose of 21Gy prescribed to the vertebral bodies. Treatment fields were matched by stepping down the dose in 10% increments over 9cm. Robustness against 3% and 3mm uncertainties, as well as a 3mm inter‐field error was analyzed. Dose coverage of the target and critical structure sparing for each plan type will be considered. Ease of planning and treatment delivery was also considered for each plan type.

Results:

The mean dose volume histograms show that the bolus plan with posterior beams gave the best overall plan, and all proton plans were comparable to or better than the photon plans. The plan type that was the most robust against the imposed uncertainties was also the bolus plan with posterior beams. This is also the plan configuration that is the easiest to deliver and plan.

Conclusion:

The bolus plan with posterior beams achieved optimal robustness against systematic position and range uncertainties, as well as inter‐field position errors.
SU‐E‐T‐341: Use of Patient Geometry and Multiple Linear Regression to Predict Prescription Dose for Pleurectomy/decortication Cases in Malignant Pleural Mesothelioma
Authors: Dumane V , Yuan Y , Rimner A , Yorke E , Rosenzweig K
Published: July 2014

Purpose:

To identify patient geometric parameters that correlate with the prescription dose in the treatment of malignant pleural mesothelioma (MPM) so as to build a model that could assist in the prediction of the same apriori and this help in planning.

Methods:

Planning CT scans for ten right sided and ten left sided patients were examined to extract five parameters for each case, which involved ratio of the ipsilateral lung volume to the total lung volume (X1), volume of PTV overlap with ipsilateral lung to ipsilateral lung volume (X2), volume of the PTV overlap with ipsilateral lung to total lung volume (X3), volume of the PTV overlap with ipsilateral lung to PTV volume (X4) and ratio of contralateral lung volume to total lung volume (X5). Each patient for this study was planned with VMAT using 6 MV on Eclipse V11 to a prescription dose that kept the mean total lung dose just under 20 Gy. Correlation coefficients were obtained between the parameters and the dose prescribed. Those that significantly correlated were combined using multiple linear regression. The model built was tested on 9 new cases.

Results:

All geometric parameters investigated except X2 showed significant correlation with the prescription dose. The correlation coefficients were r = −0.5421 for X1 (p = 0.0135), r = −0.6891 for X3 (p = 0.0008), r = −0.6797 for X4 (p = 0.001) and r = 0.5421 for X5 (p = 0.0135). The predictive model D = 4192.2×1 – 3577.1×3 – 471.6×4 + 6253.4×5 had a higher correlation (r = 0.86, p = 1.0657e‐06) with dose. For 8 out of the 9 test cases, the predicted dose was either equal to or upto 1 fraction of the prescription dose.

Conclusion:

The multiple regression model developed here could serve as a guide for dose prescribed in treatment of MPM.
SU‐E‐T‐342: Use of Patient Geometry Measurements to Predict Dosimetric Gain with VMAT Over 3D for Chestwall and Regional Nodal Radiation
Authors: Dumane V , Hunt M , Steinberger E , Knoll M , Green S , Bakst R
Published: July 2014

Purpose:

To predict the dosimetric gain of VMAT over 3D for the treatment ofchestwall/IMN/supraclavicular nodes using geometric parameters acquired during simulation

Methods:

CT scans for 20 left and 20 right sided patients were retrospectively analyzed toobtain percent ipsilateral lung volume included in the PWT and supraclavicular fields, central lung depth (CLD), maximum lung depth (MLD), separation, chestwall concavity (defined here as the product of CLD and separation) and the maximum heart depth (MHD). VMAT, PWT and P/E plans were done for each case. The ipsilateral lung V20 Gy and mean, total lung V20 Gy and mean, heart V25 Gy and mean were noted for each plan. Correlation coefficients were obtained and linear regression models were built using data from the above training set of patients and then tested on 4 new patients.

Results:

The decrease in ipsilateral lung V20 Gy, total lung V20 Gy, ipsilateral lung mean and total lung mean with VMAT over PWT significantly (p<0.05) correlated with the percent volume of ipsilateral lung included in the PWT and supraclavicular fields with correlation coefficient values of r = 0.83, r = 0.77, r = 0.78 and r = 0.75 respectively. Significant correlations were also found between MHD and the decrease in heart V25 Gy and mean of r = 0.77 and r = 0.67 respectively. Dosimetric improvement with VMAT over P/E plans showed no correlation to any of the geometric parameters investigated in this study. The dosimetric gain predicted for the 4 test cases by the linear regression models given their respective percent ipsilateral lung volumes fell within the 95% confidence intervals around the best regression fit.

Conclusion:

The percent ipsilateral lung volume appears to be a strong predictor of the dosimetric gain on using VMAT over PWT apriori.
SU‐E‐T‐345: Validation of a Patient‐Specific Monte Carlo Targeted Radionuclide Therapy Dosimetry Platform
Authors: Besemer A , Bednarz B
Published: July 2014

Purpose:

There is a compelling need for personalized dosimetry in targeted radionuclide therapy given that conventional dose calculation methods fail to accurately predict dose response relationships. To address this need, we have developed a Geant4‐based Monte Carlo patient‐specific 3D dosimetry platform for TRT. This platform calculates patient‐specific dose distributions based on serial CT/PET or CT/SPECT images acquired after injection of the TRT agent. In this work, S‐values and specific absorbed fractions (SAFs) were calculated using this platform and benchmarked against reference values.

Methods:

S‐values for 1, 10, 100, and 1000g spherical tumors with uniform activity distributions of I‐124, I‐125, I‐131, F‐18, and Ra‐223 were calculated and compared to OLINDA/EXM reference values. SAFs for monoenergetic photons of 0.01, 0.1, and 1 MeV and S factors for monoenergetic electrons of 0.935 MeV were calculated for the liver, kidneys, lungs, pancreas, spleen, and adrenals in the Zubal Phantom and compared with previously published values. Sufficient particles were simulated to keep the voxel statistical uncertainty below 5%.

Results:

The calculated spherical S‐values agreed within a few percent of reference data from OLINDA/EXM for each radionuclide and sphere size. The comparison of photon SAFs and electron S‐values with previously published values showed good agreement with the previously published values. The S‐values and SAFs of the source organs agreed within 1%.

Conclusion:

Our platform has been benchmarked against reference values for a variety of radionuclides and over a wide range of energies and tumor sizes. Therefore, this platform could be used to provide accurate patientspecific dosimetry for use in radiopharmaceutical clinical trials.
SU‐E‐T‐486: Effect of the Normalized Prescription Isodose Line On Target Dose Deficiency in Lung SBRT Based On Monte Carlo Calculation
Authors: Zheng D , Zhang Q , Zhou S
Published: July 2014

Purpose:

To investigate the impact of normalized prescription isodose line on target dose deficiency calculated with Monte Carlo (MC) vs. pencil Beam (PB) in lung SBRT. RTOG guidelines recommend prescription lines between 60% and 90% for lung SBRT. How this affects the magnitude of MC‐calculated target dose deficiency has never been studied.

Methods:

Under an IRB‐approved protocol, four lung SBRT patients were replanned following RTOG0813 by a single physicist. For each patient, four alternative plans were generated based on PB calculation prescribing to 60–90% isodose lines, respectively. Each plan consisted of 360o coplanar dynamic conformal arcs with beam apertures manually optimized to achieve similar dose coverage and conformity for all plans of the same patient. Dose distribution was calculated with MC and compared to that with PB. PTV dose‐volume endpoints were compared, including Dmin, D5, Dmean, D95, and Dmax. PTV V100 coverage, conformity index (CI), and heterogeneity index (HI) were also evaluated.

Results:

For all 16 plans, median (range) PTV V100 and CI were 99.7% (97.5–100%) and 1.27 (1.20–1.41), respectively. As expected, lower prescription line resulted in higher target dose heterogeneity, yielding median (range) HI of 1.26 (1.05–1.51) for all plans. Comparing MC to PB, median (range) D95, Dmean, D5 PTV dose deficiency were 18.9% (11.2–23.2%), 15.6% (10.0–22.7%), and 9.4%(5.5–13.6%) of the prescription dose, respectively. The Dmean, D5, and Dmax deficiency was found to monotonically increase with decreasing prescription line from 90% to 60%, while the Dmin deficiency monotonically decreased. D95 deficiency exhibited more complex trend, reaching the largest deficiency at 80% for all patients.

Conclusion:

Dependence on prescription isodose line was found for MC‐calculated PTV dose deficiency of lung SBRT. When comparing reported MC dose deficiency values from different institutions, their individual selections of prescription line should be considered in addition to other factors affecting the deficiency magnitude.
SU‐E‐T‐487: Impact of Geometric Uncertainties in Accelerated Partial Breast Irradiation Using the Strut‐Adjusted Volume Implant (SAVI)
Authors: Akino Y , Slessinger E , Srivastava S , Das I
Published: July 2014

Purpose:

Single‐entry multi‐catheter devices have been developed for accelerated partial breast irradiation (APBI). Rotational and translational uncertainties are usually mitigated by quality assurance, however its actual dosimetric impact has not been addressed, which is presented here for SAVI applicator.

Methods:

Under Institutional Review Board exemption status, we retrospectively analyzed 48 APBI treatment plans using SAVI applicator. For quick calculation of dose‐volume histogram (DVH) considering geometric uncertainties, the coordinate of each voxel of critical organs after rotation or translation along the central catheter was calculated using an in‐house software instead of rotating or translating the entire dose distribution.

Results:

For most cases, the skin doses increased with rotation to both directions. At 10 degree of rotation, the increase of Dmax (percent prescribed dose) at 50% (median), 75%, 90%, and 100% (maximum) percentile were 0.3%, 1.7%, 5.6% and 25.0%, respectively. The increase of chest wall Dmax at 50%, 75%, 90%, and 100% percentile were 0.1%, 1.0%, 10.3% and 38.8%, respectively. The increase of skin Dmax of the patients with the distance between skin surface and lumpectomy cavity surface ≤16 mm was significantly larger than those with the distance >16 mm. Similarly, patients with the distance between lung and lumpectomy cavity surface ≤20 mm showed higher sensitivity of chest wall Dmax against rotation than patients with the distance <20 mm. Translation of the applicator showed larger impact on the skin dose than rotation, although the effects on chest wall was less than 2% even at 10 mm displacement. At 5 mm of translation, increase of skin Dmax at 50%, 75%, 90%, and 100% percentile were 2.3%, 8.0%, 15.3% and 77.7%, respectively.

Conclusion:

The impacts of the geometric uncertainties (rotation and translation) of SAVI applicator were investigated. The skin‐lumpectomy cavity and lung‐lumpectomy cavity distances showed significant relationship with skin and chest wall doses, respectively.
SU‐E‐T‐489: Plan Comparisons of Re‐Irradiation Treatment of Three Intensity Modulated Techniques
Authors: Lian J , Tang X , Liu R
Published: July 2014

Purpose:

There have been controversial reports on the comparison of dosimetric quality of TomoTherapy (Tomo), VMAT and IMRT. One of the main reasons is the sampled cases are often not dosimetrically challenging enough to test the limit of optimization/delivery modalities. We chose difficult re‐irradiation cases when certain organ at risk (OAR) requires extremely low dose to examine the ability of OAR sparing of three main intensity modulated techniques.

Methods:

Three previous treated patients with disease site on head and neck (HN), brain and lung are planned for reirradiation treatment. The Tomo planning used jaw 2.5cm and pitch 0.3. VMAT and IMRT were planned on Pinnacle for a Varian 21iX Linac with MLC leaf width 5mm. VMAT plan used 2 Arcs and IMRT plan had beams 11–13. The dosimetric endpoints and treatment time were compared for each technique of each patient.

Results:

Plans of three techniques cover PTV similarly. The HN case requires PTV dose 60Gy but to limit dose of cord which is 8mm away <12Gy. The cord dose of Tomo, VMAT and IMRT plan is 11.6Gy, 11.3Gy and 11.0Gy, respectively. The brain case has PTV prescription 50.4 Gy while requiring the dose of brainstem < 28Gy. Tomo, VMAT and IMRT plan generate brainstem dose 27.6Gy, 27.6Gy and 27.1Gy respectively. For the lung case, PTV was prescribed 42.5Gy but cord dose constraint was 22.5Gy. The cord dose is optimized to 22.3Gy, 20.8Gy and 21.4Gy by Tomo, VMAT and IMRT, respectively. The delivery time if normalized to Tomo is 47.0%/145.6% (VMAT/IMRT), 33.3%/106.3% and 74.1%/245.4% for HN, brain and lung case, respectively.

Conclusion:

Difficult re‐irradiation cases were used to test the limit of three intensity modulated techniques. Tomo, VMAT and IMRT show similar dosimetry while VMAT is the most efficient one and IMRT is the least.
SU‐E‐T‐493: Analysis of the Impact of Range and Setup Uncertainties On the Dose to Brain Stem and Whole Brain in the Passively Scattered Proton Therapy Plans
Authors: Sahoo N , Zhu X , Zhang X , Poenisch F , Li H , Wu R , Lii M , Umfleet W , Gillin M , Mahajan A , Grosshans D
Published: July 2014

Purpose:

To quantify the impact of range and setup uncertainties on various dosimetric indices that are used to assess normal tissue toxicities of patients receiving passive scattering proton beam therapy (PSPBT).

Methods:

Robust analysis of sample treatment plans of six brain cancer patients treated with PSPBT at our facility for whom the maximum brain stem dose exceeded 5800 CcGE were performed. The DVH of each plan was calculated in an Eclipse treatment planning system (TPS) version 11 applying ±3.5% range uncertainty and ±3 mm shift of the isocenter in x, y and z directions to account for setup uncertainties. Worst‐case dose indices for brain stem and whole brain were compared to their values in the nominal plan to determine the average change in their values. For the brain stem, maximum dose to 1 cc of volume, dose to 10%, 50%, 90% of volume (D10, D50, D90) and volume receiving 6000, 5400, 5000, 4500, 4000 CcGE (V60, V54, V50, V45, V40) were evaluated. For the whole brain, maximum dose to 1 cc of volume, and volume receiving 5400, 5000, 4500, 4000, 3000 CcGE (V54, V50, V45, V40 and V30) were assessed.

Results:

The average change in the values of these indices in the worst scenario cases from the nominal plan were as follows. Brain stem; Maximum dose to 1 cc of volume: 1.1%, D10: 1.4%, D50: 8.0%, D90:73.3%, V60:116.9%, V54:27.7%, V50: 21.2%, V45:16.2%, V40:13.6%,Whole brain; Maximum dose to 1 cc of volume: 0.3%, V54:11.4%, V50: 13.0%, V45:13.6%, V40:14.1%, V30:13.5%.

Conclusion:

Large to modest changes in the dosiemtric indices for brain stem and whole brain compared to nominal plan due to range and set up uncertainties were observed. Such potential changes should be taken into account while using any dosimetric parameters for outcome evaluation of patients receiving proton therapy.
SU‐E‐T‐500: Dose Escalation Strategy for Lung Cancer Patients Using a Biologically‐ Guided Target Definition
Authors: Shusharina N , Khan F , Choi N , Sharp G
Published: July 2014

Purpose:

Dose escalation strategy for lung cancer patients can lead to late symptoms such as pneumonitis and cardiac injury. We propose a strategy to increase radiation dose for improving local tumor control while simultaneously striving to minimize the injury of organs at risk (OAR). Our strategy is based on defining a small, biologically‐guided target volume for receiving additional radiation dose.

Methods:

106 patients with lung cancer treated with radiotherapy were selected for patients diagnosed with stage II and III disease. Previous research has shown that 50% of the maximum SUV threshold in FDG‐PET imaging is appropriate for delineation of the most aggressive part of a tumor. After PET‐ and CT‐derived targets were contoured, an IMRT treatment plan was designed to deliver 60 Gy to the GTV as delineated on a 4D CT (Plan 1). A second plan was designed with additional dose of 18 Gy to the PET‐derived volume (Plan 2). A composite plan was generated by the addition of Plan 1 and Plan 2.

Results:

Plan 1 was compared to the composite plan and increases in OAR dose were assessed. For seven patients on average, lung V5 was increased by 1.4% and V20 by 4.2% for ipsilateral lung and by 13.5% and 7% for contralateral lung. For total lung, V5 and V20 were increased by 4.5% and 4.8% respectively. Mean lung dose was increased by 9.7% for the total lung. The maximum dose to the spinal cord increased by 16% on average. For the heart, V20 increased by 4.2% and V40 by 5.2%.

Conclusion:

It seems feasible that an additional 18 Gy of radiation dose can be delivered to FDG PET‐derived subvolume of the CT‐based GTV of the primary tumor without significant increase in total dose to the critical organs such as lungs, spinal cord and heart.
SU‐E‐T‐502: Biometrically Accepted Patient Records
Authors: Basavatia A , Kalnicki S , Garg M , Fret J , Lukaj A , Yaparpalvi R , Hong L , Tome W
Published: July 2014

Purpose:

To implement a clinically useful palm vein pattern recognition biometric system to treat the correct treatment plan to the correct patient each and every time and to check‐in the patient into the department to access the correct medical record.

Methods:

A commercially available hand vein scanning system was paired to Aria and utilized an ADT interface from the hospital electronic health system. Integration at two points in Aria, version 11 MR2, first at the appointment tracker screen for the front desk medical record access and second at the queue screen on the 4D treatment console took place for patient daily time‐out. A test patient was utilized to check accuracy of identification as well as to check that no unintended interactions take place between the 4D treatment console and the hand vein scanning system. This system has been in clinical use since December 2013.

Results:

Since implementation, 445 patients have been enrolled into our biometric system. 95% of patients learn the correct methodology of hand placement on the scanner in the first try. We have had two instances of patient not found because of a bad initial scan. We simply erased the scanned metric and the patient enrolled again in those cases. The accuracy of the match is 100% for each patient, we have not had one patient misidentified. We can state this because we still use patient photo and date of birth as identifiers. A QA test patient is run monthly to check the integrity of the system.

Conclusion:

By utilizing palm vein scans along with the date of birth and patient photo, another means of patient identification now exits. This work indicates the successful implementation of technology in the area of patient safety by closing the gap of treating the wrong plan to a patient in radiation oncology.

FOJP Service Corporation covered some of the costs of the hardware and software of the palm vein pattern recognition biometric system.
SU‐E‐T‐505: CT‐Based Independent Dose Verification for RapidArc Plan as a Secondary Check
Authors: Tachibana H , Kamima T , Takahashi R , Baba H
Published: July 2014

Purpose:

To design and develop a CT‐based independent dose verification for the RapidArc plan and also to show the effectiveness of inhomogeneous correction in the secondary check for the plan.

Methods:

To compute the radiological path from the body surface to the reference point and equivalent field sizes from the multiple MLC aperture shapes in the RapidArc MLC sequences independently, DICOM files of CT image, structure and RapidArc plan were imported to our in‐house software. The radiological path was computed using a three‐dimensional CT arrays for each segment. The multiple MLC aperture shapes were used to compute tissue maximum ratio and phantom scatter factor using the Clarkson‐method. In this study, two RapidArc plans for oropharynx cancer were used to compare the doses in CT‐based calculation and water‐equivalent phantom calculation using the contoured body structure to the dose in a treatment planning system (TPS).

Results:

The comparison in the one plan shows good agreement in both of the calculation (within 1%). However, in the other case, the CT‐based calculation shows better agreement compared to the water‐equivalent phantom calculation (CT‐based: ‐2.8% vs. Water‐based: ‐3.8%). Because there were multiple structures along the multiple beam paths and the radiological path length in the CT‐based calculation and the path in the water‐homogenous phantom calculation were comparatively different.

Conclusion:

RapidArc treatments are performed in any sites (from head, chest, abdomen to pelvis), which includes inhomogeneous media. Therefore, a more reliable CT‐based calculation may be used as a secondary check for the independent verification.
SU‐E‐T‐508: End to End Testing of a Prototype Eclipse Module for Planning Modulated Arc Therapy On the Siemens Platform
Authors: Huang L , Sarkar V , Spiessens S , Rassiah‐Szegedi P , Huang Y , Zhao H , Szegedi M , Salter B
Published: July 2014

Purpose:

The latest clinical implementation of the Siemens Artiste linac allows for delivery of modulated arcs (mARC) using full‐field flattening filter free (FFF) photon beams. The maximum doserate of 2000 MU/min is well suited for high dose treatments such as SBRT. We tested and report on the performance of a prototype Eclipse TPS module supporting mARC capability on the Artiste platform.

Method:

our spine SBRT patients originally treated with 12/13 field static‐gantry IMRT (SGIMRT) were chosen for this study. These plans were designed to satisfy RTOG0631 guidelines with a prescription of 16Gy in a single fraction. The cases were re‐planned as mARC plans in the prototype Eclipse module using the 7MV FFF beam and required to satisfy RTOG0631 requirements. All plans were transferred from Eclipse, delivered on a Siemens Artiste linac and dose‐validated using the Delta4 system.

Results:

All treatment plans were straightforwardly developed, in timely fashion, without challenge or inefficiency using the prototype module. Due to the limited number of segments in a single arc, mARC plans required 2‐3 full arcs to yield plan quality comparable to SGIMRT plans containing over 250 total segments. The average (3%/3mm) gamma pass‐rate for all arcs was 98.5±1.1%, thus demonstrating both excellent dose prediction by the AAA dose algorithm and excellent delivery fidelity. Mean delivery times for the mARC plans(10.5±1.7min) were 50‐70% lower than the SGIMRT plans(26±2min), with both delivered at 2000 MU/min.

Conclusion:

A prototype Eclipse module capable of planning for Burst Mode modulated arc delivery on the Artiste platform has been tested and found to perform efficiently and accurately for treatment plan development and delivered‐dose prediction. Further investigation of more treatment sites is being carried out and data will be presented.
SU‐E‐T‐511: Do Presage 3D Dosimeters Show Dose Fractionation Sensitivity?
Authors: Klawikowski S , Adamovics J , Alqathami M , Benning R , Ibbott G
Published: July 2014

Purpose:

To determine whether Presage 3D polymer dosimeter dose response is sensitive to dose delivery fractionation. Bang gels have demonstrated a dose fractionation related dependence in which a single 400 cGy irradiation would produce a different detector response than four 100 cGy irradiations even if delivered closely in time to one another. Such a fractional dependent response in Presage would be detrimental for measuring multi‐beam irradiations.

Methods:

Two separate batches of Presage were poured into cuvettes, and a third batch was molded into cuvette shaped blocks. A total of 37 cuvettes/blocks were irradiated in a Cobalt‐60 irradiator to 400 cGy within solid water phantoms in either one, eight, or sixteen fractions. Another group of 15 cuvettes were also kept unirradiated and used for background subtraction between the pre‐scan and post‐scan results. The times between fractional deliveries were held constant at 30 seconds and the Cobalt irradiator dose rate was 49 cGy/min. Each Presage batch has a separate dose sensitivity and therefore fractionation response comparisons were only performed within the same batch. The cuvettes were first pre‐scanned the day prior to irradiation and post‐scanned the day after irradiation. Other than approximately 3 hours warming time prior to each irradiation and optical density measurement the cuvettes were stored in a refrigerator. All cuvettes were stored in a lightless environment throughout manufacturing and testing. The cuvettes’ optical densities were optically measured at 632 nm with a spectrophotometer.

Results:

No noticeable dose fractionation dependence was detected for any of the three independent batches of Presage for either the eight or sixteen fraction irradiation schemes.

Conclusion:

These results indicate using Presage 3D dosimeters to measure multi‐beam photon irradiations common in IMRT, Gamma Knife, and Cyberknife treatment delivery schemes.

Presage dosimeters are made by and trademarked by Heuris Inc. Skillman, NJ. Dr. John Adamovics is a founder of Heuris Inc.
SU‐E‐T‐514: Simultaneously Determination of Radiation Isocentricity of Gantry, Collimator and Couch Using a Commercial Three‐Dimensional Dosimetry QA Apparatus
Authors: Yan S , Song H , Wu Q
Published: July 2014

Purpose:

Radiation isocentricity is an important benchmark for a LINAC and is typically determined by 3 separate film star‐shots. We developed a technique to simultaneously determine the radiation isocenter of gantry, collimator and couch with a commercial 3D QA apparatus.

Methods:

The ArcCHECK from SunNuclear was used on two LINACs. It was aligned with room lasers. For gantry rotation, collimator and couch were set to zero and gantry was placed to 0, 49, 213 and 311 degrees. Similarly, a set of collimator/couch angles were chosen with the other two axes at neutral positions. The measured dose matrices were analyzed by an in‐house MATLAB program. For each shot, the central axis was determined by computing the FWHM of the diode arrays. The largest inscribed circle from these central axis lines was used to determine isocenter: the radius as the benchmark of isocentricity and the coordinates of the center as the discrepancy of radiation isocenter to the origin defined by lasers. To validate the method, the couch was shifted by ~5 mm in all three directions and measurements were repeated.

Results:

The radius of the largest inscribed circle for gantry, collimator and couch are (0.3, 0.5, 0.2) mm for one LINAC and (0.2, 0.3, 0.1) mm for the other, in agreement with the film star‐shots at annual QA. The discrepancies of radiation isocenter are generally within 1 mm, except gantry rotation on one LINAC due to the drift of foot laser. The differences in positions detected are consistent with the intentional predefined shift.

Conclusion:

We have demonstrated a technique for the simultaneous measurement of gantry, collimator, and couch isocentricity with a set of carefully chosen irradiation parameters based on the specific construction geometry of the 3D detector ArcCheck. This can replace the standard film star‐shots. The future work includes improving operation efficiency.
SU‐E‐T‐515: Field‐In‐Field Compensation Technique Using Multi‐Leaf Collimator to Deliver Total Body Irradiation (TBI) Dose
Authors: Lakeman T , Wang IZ
Published: July 2014

Purpose:

Total body irradiation (TBI) uses large parallel‐opposed radiation fields to suppress the patient's immune system and eradicate the residual cancer cells in preparation of recipient for bone marrow transplant. The manual placement of lead compensators has been used conventionally to compensate for the varying thickness through the entire body in large‐field TBI. The goal of this study is to pursue utilizing the modern field‐in‐field (FIF) technique with the multi‐leaf collimator (MLC) to more accurately and efficiently deliver dose to patients in need of TBI.

Method:

Treatment plans utilizing the FIF technique to deliver a total body dose were created retrospectively for patients for whom CT data had been previously acquired. Treatment fields include one pair of opposed open large fields (collimator=45°) with a specific weighting and a succession of smaller fields (collimator=90°) each with their own weighting. The smaller fields are shaped by moving MLC to block the sections of the patient which have already received close to 100% of the prescribed dose. The weighting factors for each of these fields were calculated using the attenuation coefficient of the initial lead compensators and the separation of the patient in different positions in the axial plane.

Results:

Dose‐volume histograms (DVH) were calculated for evaluating the FIF compensation technique. The maximum body doses calculated from the DVH were reduced from the non‐compensated 179.3% to 148.2% in the FIF plans, indicating a more uniform dose with the FIF compensation. All calculated monitor units were well within clinically acceptable limits and exceeded those of the original lead compensation plan by less than 50 MU (only ~1.1% increase).

Conclusion:

MLC FIF technique for TBI will not significantly increase the beam on time while it can substantially reduce the compensator setup time and the potential risk of errors in manually placing lead compensators.
SU‐E‐T‐517: Analytic Formalism to Compute in Real Time Dose Distributions Delivered by HDR Units
Authors: Pokhrel S , Palaniswaamy G , Rangaraj D , Loyalka S , Izaguirre E
Published: July 2014

Purpose:

Develop an analytical algorithm to compute the dose delivered by Ir‐192 dwell positions with high accuracy using the 3‐dimensional (3D) dose distribution of an HDR source. Using our analytical function, the dose delivered by an HDR unit as treatment progresses can be determined using the actual delivered temporal and positional data of each individual dwell. Consequently, true delivered dose can be computed when each catheter becomes active. We hypothesize that the knowledge of such analytical formulation will allow developing HDR systems with a real time treatment evaluation tool to avoid mistreatments.

Methods:

In our analytic formulation, the dose is computed by using the full anisotropic function data of the TG 43 formalism with 3D ellipsoidal function. The discrepancy between the planned dose and the delivered dose is computed using an analytic perturbation method over the initial dose distribution. This methodology speeds up the computation because only changes in dose discrepancies originated by spatial and temporal deviations are computed. A dose difference map at the point of interest is obtained from these functions and this difference can be shown during treatment in real time to examine the treatment accuracy.

Results:

We determine the analytical solution and a perturbation function for the 3 translational 3 rotational, and 1D temporal errors in source distributions. The analytic formulation is a sequence of simple equations that can be processed in any modern computer in few seconds. Because computations are based in an analytical solution, small deviations of the dose when sub‐millimeter positional changes occur can be detected.

Conclusions:

We formulated an analytical method to compute 4D dose distributions and dose differences based on an analytical solution and perturbations to the original dose. This method is highly accurate and can be
SU‐E‐T‐518: Dosiemtric Impact of Patient Positioning Uncertainty in SBRT Treatments
Authors: Abbas H , Abolfath R , Nath R , Chen Z
Published: July 2014

Purpose:

To investigate the dosimetric impact of patient positioning uncertainties on conventionally fractionated IMRT, hypofractionated and single‐fraction SBRT in light of the recently published AAPM practice guideline on IGRT quality assurance (MPPG2a) .

Methods:

Treatment plans of three prostate IMRT, three lungs SBRT and three spine SBRT patients were selected for this study. For each patient, uncertainties in isocenter positioning were simulated by displacing the planned isocenter with variable amount in three cardinal directions. The resulting dose distribution was obtained by recalculating the original treatment plan for each displaced isocenter position with the same planned monitor units. Dosimetric impact was assessed by comparing the isocenter‐shifted plan with the original plan with respect to the image‐treatment isocenter coincidence tolerance recommended in MPPG2a (1 mm for SRS and 2 mm for SBRT) .

Results:

For prostate IMRT, a 2‐mm uncertainty in lateral and superior‐inferior direction had minimal dosimetric impact on either PTV or rectum. However, a 2‐mm deviation in the anterior‐posterior position could Result in up to 8% change in PTV minimum dose (PTVDmin) and up to 7% increase in rectum D25. For lung SBRT, uncertainties of ≤ 2mm had minimal impact on PTV mean dose and mean lung dose. However, up to 21% reduction in PTVDmin was observed with a 2‐mm uncertainty in superior‐inferior direction. For single‐fraction spine SBRT, a 1‐mm uncertainty could cause up to 10% change in PTVDmin and cord maximum dose. Formal statistical analysis for patient‐specific impact over a given course of treatment is being performed .

Conclusion:

In addition to SRS, single‐fraction SBRT should require isocenter alignment tolerance to be ≤ 1 mm. The 2‐mm positioning tolerance for SBRT may not be sufficient for certain patients. Our analysis can be integrated into the treatment planning system for prospective prediction of the susceptibility of individual plans to setup uncertainties.
SU‐E‐T‐519: Emission of Secondary Particles From a PMMA Phantom During Proton Irradiation: A Simulation Study with the Geant4 Monte Carlo Toolkit
Authors: Lau A , Chen Y , Ahmad S
Published: July 2014

Purpose:

Proton therapy exhibits several advantages over photon therapy due to depth‐dose distributions from proton interactions within the target material. However, uncertainties associated with protons beam range in the patient limit the advantage of proton therapy applications. To quantify beam range, positron‐emitting nuclei (PEN) and prompt gamma (PG) techniques have been developed. These techniques use de‐excitation photons to describe the location of the beam in the patient. To develop a detector system for implementing the PG technique for range verification applications in proton therapy, we studied the yields, energy and angular distributions of the secondary particles emitted from a PMMA phantom.

Methods:

Proton pencil beams of various energies incident onto a PMMA phantom with dimensions of 5 x 5 x 50 cm3 were used for simulation with the Geant4 toolkit using the standard electromagnetic packages as well as the packages based on the binary‐cascade nuclear model. The emitted secondary particles are analyzed .

Results:

For 160 MeV incident protons, the yields of secondary neutrons and photons per 100 incident protons were ~6 and ~15 respectively. Secondary photon energy spectrum showed several energy peaks in the range between 0 and 10 MeV. The energy peaks located between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (~ 4.4 MeV) and 16O (~ 6 MeV), respectively. Most of the escaping secondary neutrons were found to have energies between 10 and 100 MeV. Isotropic emissions were found for lower energy neutrons (<10 MeV) and photons for all energies, while higher energy neutrons were emitted predominantly in the forward direction. The yields of emitted photons and neutrons increased with the increase of incident proton energies.

Conclusions:

A detector system is currently being developed incorporating the yields, energy and angular distributions of secondary particles from proton interactions obtained from this study.
SU‐E‐T‐522: A Multi‐Isocenter VMAT Technique for Cranio‐Spinal Irradiation
Authors: Aristophanous M , Chi P , Tung S , Pinnix C , Dabaja B
Published: July 2014

Purpose:

Develop a matching VMAT field technique and investigate planning feasibility for treating the entire central nervous system (CNS) using Cranio‐Spinal Irradiation (CSI) .

Methods:

Two patients diagnosed with acute myeloid leukemia (AML) presented with CNS involvement, received CSI, and were included in this study. The patients were treated with the traditional CSI technique: prone position, opposing lateral brain fields, two posterior fields (upper and lower spine), and 5mm junction shifts to improve dose uniformity. The patients were retrospectively re‐planned using volumetric arc therapy (VMAT). The spine and brain were contoured to create the clinical target volume (CTV) as well as normal tissues including kidneys, lung and heart for optimization. Three isocenters were used for planning: brain, upper and lower spine. The beams were allowed to overlap by approximately 10cm. Entire 360 degree rotations were used for the brain fields and posterior 120 degree arcs were used for the spine fields. The dosimetric coverage of the target between the VMAT and traditional plans was compared, as well as the dose to normal tissues.

Results:

Both VMAT plans achieved improved dose uniformity in the CTV (standard deviation < 2%), and reduced hot spots (<110%). Dose to the heart was reduced, with the V10 being 12.7% and 28.2%, compared to 44.6% and 50.2%, respectively, for the traditional plan. Dose to the total lung V5 increased for the VMAT plans for both patients (21.6% and 27.8% compared to 12% and 13% respectively). The results for the kidneys were mixed with the mean dose increasing for one patient and decreasing for the other .

Conclusion:

The efficacy of planning CSI treatments using a matching VMAT technique was demonstrated. The developed technique has the potential to improve dose uniformity to the target while at the same time reduce the risk of under or over dosing the spine.