bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐631: Preliminary Results for Analytical Investigation Into Effects of ArcCHECK Setup Errors
Authors: Kar S , Tien C 
Published: June 2015

Purpose:As three‐dimensional diode arrays increase in popularity for patient‐specific quality assurance for intensity‐modulated radiation therapy (IMRT), it is important to evaluate an array's susceptibility to setup errors. The ArcCHECK phantom is set up by manually aligning its outside marks with the linear accelerator's lasers and light‐field. If done correctly, this aligns the ArcCHECK cylinder's central axis (CAX) with the linear accelerator's axis of rotation. However, this process is prone to error. This project has developed an analytical expression including a perturbation factor to quantify the effect of shifts.Methods:The ArcCHECK is set up by aligning its machine marks with either the sagittal room lasers or the light‐field of the linear accelerator at gantry zero (IEC). ArcCHECK has sixty‐six evenly‐spaced SunPoint diodes aligned radially in a ring 14.4 cm from CAX. The detector response function (DRF) was measured and combined with inverse‐square correction to develop an analytical expression for output. The output was calculated using shifts of 0 (perfect alignment), +/−1, +/−2 and +/−5 mm. The effect on a series of simple inputs was determined: unity, 1‐D ramp, steps, and hat‐function to represent uniform field, wedge, evenly‐spaced modulation, and single sharp modulation, respectively.Results:Geometric expressions were developed with perturbation factor included to represent shifts. DRF was modeled using sixth‐degree polynomials with correlation coefficient 0.9997. The output was calculated using simple inputs such as unity, 1‐D ramp, steps, and hat‐function, with perturbation factors of: 0, +/−1, +/−2 and +/−5 mm. Discrepancies have been observed, but large fluctuations have been somewhat mitigated by aliasing arising from discrete diode placement.Conclusion:An analytical expression with perturbation factors was developed to estimate the impact of setup errors on an ArcCHECK phantom. Presently, this has been applied to simple functions, but is being developed to handle more realistic clinical cases.
SU‐E‐T‐632: Preliminary Study On Treating Nose Skin Using Energy and Intensity Modulated Electron Beams with Monte Carlo Based Dose Calculations
Authors: Jin L , Eldib A , Li J , Price R , Ma C 
Published: June 2015

Purpose:Uneven nose surfaces and air cavities underneath and the use of bolus present complexity and dose uncertainty when using a single electron energy beam to plan treatments of nose skin with a pencil beam‐based planning system. This work demonstrates more accurate dose calculation and more optimal planning using energy and intensity modulated electron radiotherapy (MERT) delivered with a pMLC.Methods:An in‐house developed Monte Carlo (MC)‐based dose calculation/optimization planning system was employed for treatment planning. Phase space data (6, 9, 12 and 15 MeV) were used as an input source for MC dose calculations for the linac. To reduce the scatter‐caused penumbra, a short SSD (61 cm) was used. Our previous work demonstrates good agreement in percentage depth dose and off‐axis dose between calculations and film measurement for various field sizes. A MERT plan was generated for treating the nose skin using a patient geometry and a dose volume histogram (DVH) was obtained. The work also shows the comparison of 2D dose distributions between a clinically used conventional single electron energy plan and the MERT plan.Results:The MERT plan resulted in improved target dose coverage as compared to the conventional plan, which demonstrated a target dose deficit at the field edge. The conventional plan showed higher dose normal tissue irradiation underneath the nose skin while the MERT plan resulted in improved conformity and thus reduces normal tissue dose.Conclusion:This preliminary work illustrates that MC‐based MERT planning is a promising technique in treating nose skin, not only providing more accurate dose calculation, but also offering an improved target dose coverage and conformity. In addition, this technique may eliminate the necessity of bolus, which often produces dose delivery uncertainty due to the air gaps that may exist between the bolus and skin.
SU‐E‐T‐633: Preparation and Planning of a VMAT Multi ‐ Arc Radiation Therapy Technique for Full Scalp Treatment
Authors: Araujo C , Bardock A , Berkelaar S , Gillund D , McGee K , Mohamed I , Lapointe C 
Published: June 2015

Purpose:The target volume for angiosarcoma of the scalp encompasses the entire scalp. Full scalp radiotherapy (FSRT) requires careful design of required bolus, immobilization and marking of the field before the patient CT is acquired. A VMAT multi‐arc technique was designed to deliver FSRT for a patient with angiosarcoma of the scalp to a dose of 6000cGy in 25 fractions.Methods:A custom bolus helmet was fabricated from a 0.5 cm thick sheet of aquaplast material, which was molded to the patient's head. With the bolus helmet in place the patient was then positioned supine on a H&N immobilization board. A custom vaclock bag positioned on a standard headrest and a thermoplastic mask were used to immobilize the patient. Additional bolus to cover the remaining treatment area was attached to the mask. We acquired two CT scans of the patient's head, one in treatment position and an additional scan without the immobilization mask with wires marking the treatment area that the oncologist had delineated on the patient's skin. The second scan was registered to the first and used to define the treatment CTV. A four‐arc VMAT treatment planned using Varian‐Eclipse was optimized to cover the skin with a PTV margin while sparing the brain and limiting the dose to the optic apparatus and lacrimal glands. Daily treatment setup was verified using anterior and lateral kV on‐board‐imaging. To verify the treated dose, TLDs were positioned on the patient's scalp during one fraction.Results:With full dose coverage to the PTV, the mean dose to the brain was less than 24 Gy. The dose measured by the TLDs (mean difference 1%, standard deviation 4%)showed excellent agreement with the treatment planning calculation.Conclusion:FSRT delivered with a bolus helmet and a VMAT multi‐arc technique can be accurately delivered with high dose uniformity and conformality.
SU‐E‐T‐635: Process Mapping of Eye Plaque Brachytherapy
Authors: Huynh J , Kim Y 
Published: June 2015

Purpose:To apply a risk‐based assessment and analysis technique (AAPM TG 100) to eye plaque brachytherapy treatment of ocular melanoma.Methods:The role and responsibility of personnel involved in the eye plaque brachytherapy is defined for retinal specialist, radiation oncologist, nurse and medical physicist. The entire procedure was examined carefully. First, major processes were identified and then details for each major process were followed.Results:Seventy‐one total potential modes were identified. Eight major processes (corresponding detailed number of modes) are patient consultation (2 modes), pretreatment tumor localization (11), treatment planning (13), seed ordering and calibration (10), eye plaque assembly (10), implantation (11), removal (11), and deconstruction (3), respectively. Half of the total modes (36 modes) are related to physicist while physicist is not involved in processes such as during the actual procedure of suturing and removing the plaque.Conclusion:Not only can failure modes arise from physicist‐related procedures such as treatment planning and source activity calibration, but it can also exist in more clinical procedures by other medical staff. The improvement of the accurate communication for non‐physicist‐related clinical procedures could potentially be an approach to prevent human errors. More rigorous physics double check would reduce the error for physicist‐related procedures. Eventually, based on this detailed process map, failure mode and effect analysis (FMEA) will identify top tiers of modes by ranking all possible modes with risk priority number (RPN). For those high risk modes, fault tree analysis (FTA) will provide possible preventive action plans.
SU‐E‐T‐638: Proton Beam Delivery to a Moving Lung Tumor and Monte Carlo Simulation with TOPAS
Authors: Coruh M , Demez N , Ewell L 
Published: June 2015

Purpose:To estimate the dose delivered to a moving lung tumor by proton therapy beams of different modulation types, and compare with Monte Carlo predictions.Methods:A radiology support devices (RSD) phantom was irradiated with therapeutic proton radiation beams using two different types of modulation: uniform scanning (US) and double scattered (DS). The Eclipse© dose plan was designed to deliver 1.00Gy to the isocenter of a static ∼3×3×3cm (27cc) tumor in the phantom with 100% coverage. The peak to peak amplitude of tumor motion varied from 0.0 to 2.5cm. The radiation dose was measured with an ion‐chamber (CC‐13) located within the tumor. The time required to deliver the radiation dose varied from an average of 65s for the DS beams to an average of 95s for the US beams.Results:The amount of radiation dose varied from 100% (both US and DS) to the static tumor down to approximately 92% for the moving tumor. The ratio of US dose to DS dose ranged from approximately 1.01 for the static tumor, down to 0.99 for the 2.5cm moving tumor. A Monte Carlo simulation using TOPAS included a lung tumor with 4.0cm of peak to peak motion. In this simulation, the dose received by the tumor varied by ∼40% as the period of this motion varied from 1s to 4s.Conclusion:The radiation dose deposited to a moving tumor was less than for a static tumor, as expected. At large (2.5cm) amplitudes, the DS proton beams gave a dose closer to the desired dose than the US beams, but equal within experimental uncertainty. TOPAS Monte Carlo simulation can give insight into the moving tumor — dose relationship.This work was supported in part by the Philips corporation.
SU‐E‐T‐639: Proton Dose Calculation for Irregular Motion Using a Sliding Interface
Authors: Phillips J , Gueorguiev G , Grassberger C , Paganetti H , Sharp G 
Published: June 2015

Purpose:While many techniques exist to evaluate dose to regularly moving lung targets, there are few available to calculate dose at tumor positions not present in the 4DCT. We have previously developed a method that extrapolates an existing dose to a new tumor location. In this abstract, we present a novel technique that accounts for relative anatomical shifts at the chest wall interface. We also utilize this procedure to simulate breathing motion functions on a cohort of eleven patients. Amplitudes exceeding the original range of motion were used to evaluate coverage using several aperture and smearing beam settings.Methods:The water‐equivalent depth (WED) technique requires an initial dose and CT image at the corresponding tumor position. Each dose volume was converted from its Cartesian geometry into a beam‐specific radiological depth space. The sliding chest wall interface was determined by converting the lung contour into this same space. Any dose proximal to the initial boundary of the warped lung contour was held fixed, while the remaining distal dose was moved in the direction of motion along the interface.Results:V95 coverage was computed for each patient using the updated algorithm. Incorporation of the sliding motion yielded large dose differences, with gamma pass rates as low as 69.7% (3mm, 3%) and V95 coverage differences up to 2.0%. Clinical coverage was maintained for most patients with 5 mm excess simulated breathing motion, and up to 10 mm of excess motion was tolerated for a subset of patients and beam settings.Conclusion:We have established a method to determine the maximum allowable excess breathing motion for a given plan on a patient‐by‐patient basis. By integrating a sliding chest wall interface into our dose calculation technique, we have analyzed the robustness of breathing patterns that differ during treatment from at the time of 4DCT acquisition.
SU‐E‐T‐642: PTV Is the Voxel‐Wise Worst‐Case of CTV in Prostate Photon Therapy
Authors: Harrington D , Schild S , Wong W , Vora S , Liu W 
Published: June 2015

Purpose:To examine the adequacy of the planning target volume (PTV) dose distribution as the worst‐case representation of clinical target volume (CTV) dose distribution in prostate volumetric‐modulated arc therapy (VMAT) plans.Methods:Ten intact prostate cancer cases treated by VMAT at our institution were randomly selected. Isocenter was shifted in the three cardinal directions by a displacement equal to the PTV expansion on the CTV (±3 mm) for a total of six shifted plans per original plan. Rotationally‐perturbed plans were generated with a couch rotation of ±1° to simulate patient yaw. The eight perturbed dose distributions were recalculated in the treatment planning system using the same, fixed fluence map as the original plan. The voxel‐wise worst‐case CTV dose distribution was constructed from the minimum value per voxel from the eight perturbed doses. The resulting dose volume histograms (DVH) were evaluated for statistical correlation between the worst‐case CTV and nominal PTV dose distributions based on D95% by Wilcoxon signed‐rank test with significance level p ≤ 0.05.Results:Inspection demonstrates the PTV DVH in the nominal dose distribution is bounded by the CTV DVH in the worst‐case dose distribution. Comparison of D95% for the two dose distributions by Wilcoxon signed‐rank test gives p = 0.131. Therefore the null hypothesis cannot be rejected since the difference in median values is not statistically significant.Conclusion:The assumption that the nominal dose distribution for PTV represents the worst‐case dose distribution for CTV appears valid for the ten plans under examination. Although the worst‐case dose distribution is unphysical since the dose per voxel is chosen independently, it serves as a lower bound for the possible CTV coverage. Furthermore, this is consistent with the unphysical nature of the PTV. Minor discrepancies between the two dose distributions are expected since the dose cloud is not strictly static.Funding Support: NIH/NCI K25CA168984, Eagles Cancer Research Career Development, The Lawrence W. and Marilyn W. Matteson Fund for Cancer Research, Mayo ASU Seed Grant, and The Kemper Marley Foundation
SU‐E‐T‐643: Pure Alanine Dosimeter for Verification Dosimetry in IMRT
Authors: Al‐Karmi Anan M. , Zraiqat Fadi 
Published: June 2015

Purpose:The objective of this study was evaluation of accuracy of pure alanine dosimeters measuring intensity‐modulated radiation therapy (IMRT) dose distributions in a thorax phantom.Methods:Alanine dosimeters were prepared in the form of 110 mg pure L‐α‐alanine powder filled into clear tissue‐equivalent polymethylmethacrylate (PMMA) plastic tubes with the dimensions 25 mm length, 3 mm inner diameter, and 1 mm wall thickness. A dose‐response calibration curve was established for the alanine by placing the dosimeters at 1.5 cm depth in a 30×30×30 cm3 solid water phantom and then irradiating on a linac with 6 MV photon beam at 10×10 cm2 field size to doses ranging from 1 to 5 Gy. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the absorbed dose in alanine. An IMRT treatment plan was designed for a commercial heterogeneous CIRS thorax phantom and the dose values were calculated at three different points located in tissue, lung, and bone equivalent materials. A set of dose measurements was carried out to compare measured and calculated dose values by placing the alanine dosimeters at those selected locations inside the thorax phantom and delivering the IMRT to the phantom.Results:The alanine dose measurements and the IMRT plan dose calculations were found to be in agreement within ±2%. Specifically, the deviations were −0.5%, 1.3%, and −1.7% for tissue, lung, and bone; respectively. The slightly large deviations observed for lung and bone may be attributed to tissue inhomogeneity, steep dose gradients in these regions, and uncontrollable changes in spectrometer conditions.Conclusion:The results described herein confirmed that pure alanine dosimeter was suitable for in‐phantom dosimetry of IMRT beams because of its high sensitivity and acceptable accuracy. This makes the dosimeter a promising option for quality control of the therapeutic beams, complementing the commonly used ionization chambers, TLDs, and films.
SU‐E‐T‐649: Quality Assurances for Proton Therapy Delivery Equipment
Authors: Arjomandy B , Klein E , Taylor P , Ainsley C , Safai S , Sahoo N , Pankuch M , Park S , Farr J , Kase Y , Flanz J , Yorke E , Followill D 
Published: June 2015

Purpose:The number of proton therapy centers has increased dramatically over the past decade. Currently, there is no comprehensive set of guidelines that addresses quality assurance (QA) procedures for the different technologies used for proton therapy. The AAPM has charged task group 224 (TG‐224) to provide recommendations for QA required for accurate and safe dose delivery, using existing and next generation proton therapy delivery equipment.Methods:A database comprised of QA procedures and tolerance limits was generated from many existing proton therapy centers in and outside of the US. These consist of proton therapy centers that possessed double scattering, uniform scanning, and pencil beams delivery systems. The diversity in beam delivery systems as well as the existing devices to perform QA checks for different beam parameters is the main subject of TG‐224. Based on current practice at the clinically active proton centers participating in this task group, consensus QA recommendations were developed. The methodologies and requirements of the parameters that must be verified for consistency of the performance of the proton beam delivery systems are discussed.Results:TG‐224 provides procedures and QA checks for mechanical, imaging, safety and dosimetry requirements for different proton equipment. These procedures are categorized based on their importance and their required frequencies in order to deliver a safe and consistent dose. The task group provides daily, weekly, monthly, and annual QA check procedures with their tolerance limits.Conclusions:The procedures outlined in this protocol provide sufficient information to qualified medical physicists to perform QA checks for any proton delivery system. Execution of these procedures should provide confidence that proton therapy equipment is functioning as commissioned for patient treatment and delivers dose safely and accurately within the established tolerance limits. The report will be published in late 2015.
SU‐E‐T‐656: Quantitative Analysis of Proton Boron Fusion Therapy (PBFT) in Various Conditions
Authors: Yoon D , Jung J , Shin H , Kim M , Jang H , Suh T 
Published: June 2015

Purpose:Three alpha particles are concomitant of proton boron interaction, which can be used in radiotherapy applications. We performed simulation studies to determine the effectiveness of proton boron fusion therapy (PBFT) under various conditions.Methods:Boron uptake regions (BURs) of various widths and densities were implemented in Monte Carlo n‐particle extended (MCNPX) simulation code. The effect of proton beam energy was considered for different BURs. Four simulation scenarios were designed to verify the effectiveness of integrated boost that was observed in the proton boron reaction. In these simulations, the effect of proton beam energy was determined for different physical conditions, such as size, location, and boron concentration.Results:Proton dose amplification was confirmed for all proton beam energies considered (< 96.62%). Based on the simulation results for different physical conditions, the threshold for the range in which proton dose amplification occurred was estimated as 0.3 cm. Effective proton boron reaction requires the boron concentration to be equal to or greater than 14.4 mg/g.Conclusion:We established the effects of the PBFT with various conditions by using Monte Carlo simulation. The results of our research can be used for providing a PBFT dose database.
SU‐E‐T‐658: Quantitative Comparison of VMAT Arc Geometry for Locally Advanced Lung Cancer with Large PTVs
Authors: Zhu T , Wilkinson J , Burger P , Matuszak M 
Published: June 2015

Purpose:Overall low dose to lung for patients with locally advanced lung cancer with large PTVs is a concern, prompting investigation into the preferred arc geometry for lung VMAT.Methods:8 subjects (6 males, 64±7 years, stage III/IV=5/3) were enrolled with a mean PTV size of 595±303cc. A standard dose scheme of 60Gy in 30 fractions was used for all subjects. For each subject, four VMAT plans with different combinations of the number of arcs (1 arc vs. two arcs) and the arc range (full vs. partial arc) were generated in Eclipse. Dosimetric characteristics for each plan were evaluated by PTV coverage and OAR sparing. PTV coverage was quantified by mean, max dose, homogeneity index HI5/95 defined as (D5%–D95%)/Mean_dose and conformity index (CI). OAR sparing was measured by mean, V10 and V20 for lung minus GTV, mean, max, V30 and V40 for heart and max dose for cord. For each metric abovementioned, a two‐way repeated ANOVA analysis was performed to evaluate whether the number of arcs and the arc range will significantly affect dose distribution of VMAT plans.Results:In general partial arc geometry provided better PTV coverage with significantly smaller HI5/95 (p<0.05) and higher mean dose (p=0.15) when keeping the total MU similar. For OAR sparing, partial arc geometry resulted in more dose sparing to the contralateral lung with significantly reduced mean lung dose (p=0.006). On the other hand, full arc geometry significantly reduced mean dose to the ipsilateral lung (p=0.02) as well as dose to the heart and the cord (p<0.05) especially with a two‐full arc geometry.Conclusion:Results of this study suggest that choice of an optimal VMAT geometry depends on clinical goals. For example, partial arc geometry should be preferred over full arc when considering overall low lung dose for patients with poor lung functions.