bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐690: Sensitivity Analysis to Machine Error: Comparisons of VMAT QA Systems
Authors: Liang B , Liu B , Yin F , Zhou F , Wu Q 
Published: June 2015

Purpose:In VMAT delivery, the gantry angles, dose rate and the MLC positions are all modulated. It is therefore necessary to perform pre‐treatment QA to detect any possible errors either in the plan or machine delivery system. Previously we developed a QA technique for VMAT using EPID in cine mode on a TrueBeam LINAC. The purpose of this study is to compare the technique with commercially available VMAT QA systems on the sensitivity to machine error.Methods:In our technique, the VMAT plan was delivered with EPID acquiring cine images simultaneously. The measured portal dose (PD) is derived from the acquired images. The predicted PD is calculated using the control point information in the plan and the delivery information in the EPID images. 3D γ analysis with the 3rd axis being gantry angle is performed between predicted and measured PD. The commercial VMAT QA system was Delta‐4 system from ScandiDose. The QA of the original plan is the reference. Several types of machine errors were simulated and evaluated: gantry angle, MLC position, and output. The original plan is modified by introducing intentional errors of various magnitudes. The modified plan is delivered and the measured PD is compared with the original predicted PD to determine the sensitivity to machine errors.Results:For the reference, in Delta‐4, the γ passrate is 99.6% for 3%/3mm criteria, and our technique has γ passrate of 98.5% for 3%/3mm/2° criteria. When errors are introduced, the passrate decreases. The sensitivity of Deltat4 (EPID) to gantry angle, MLC, and output are 1.4%/° (2.8%/°), 22%/mm(6%/mm), and 0%/% (0.1%/%), respectively. Similar results were observed under different criteria.Conclusion:Compared with Delta‐4 system, the EPID technique is more sensitive to gantry angle error, but less sensitive to MLC positioning error. Delta‐4 system is insensitive to the machine output error.This work was partially supported by the National Natural Science Foundation of China (61171005) and the China Scholarship Council (CSC).
SU‐E‐T‐693: Should We Use RapidArc (VMAT) for Breast Treatments? A Dosimetric Comparison of IMRT Versus VMAT Optimization in Whole Breast Irradiation of Early Stage Breast Cancer
Authors: Sedeh N Moshiri , Pella S , Leventouri T , Littlejohn D , Costantino T 
Published: June 2015

Purpose:The purpose of this study is to compare the dose‐volumetric results of intensity modulated radiation therapy (IMRT) with RapidArc (RA Varian Medical Systems, Palo Alto, CA) for whole breast irradiation.Methods:25 whole left breast patient's plans (either RapidArc plan or IMRT) previously treated were the subjects of this study. Eclipse v 11.0.47 was used to create the alternative plans for each case using the same CT images, contours, energy, Linac and normalization. The prescription dose to the planning target volume was 50 Gy in 25 fractions. All plans were normalized such that 100% of the dose covered 95% of planning target volume (PTV).Results:V10, V20 and Dmean Gy of left lung differ significantly between the two plans (p‐value <0.0001, =0.0473 and <0.0001 respectively). However, V30 Gy does not (p‐value 0.463). V25, D33 and Dmean Gy of heart differ significantly between the two plans (p‐value =0.034, <0.0001 and 0.01 respectively). However V10 Gy does not (p‐value 0.058). V5 of both right breast and right lung differs significantly between the two plans (p‐value <0.0007 and =0.0112, respectively). Dmean of both right breast and right lung differs significantly between the two plans (p‐value <0.0001 for both). The mean conformity index did not differ significantly, p‐value 0.142. There was a significant difference between the mean MUs of the two plans as well, p‐value <0.0001.Conclusion:Mean doses to left lung, heart, right lung and right breast were significantly different in RapidArc than IMRT plans. IMRT treatment delivery was faster than RapidArc in terms of the total monitor units used (mean of 382 vs 707 respectively). In fact, since it was observed that both plans have the same mean of conformity index, IMRT is not only faster but also safer regarding not irradiating the organs at risk.
SU‐E‐T‐696: Similar‐Case‐Based Framework of Beam Angle Configurations Using Treatment‐Plan‐Related Features in Lung Stereotactic Body Radiation Therapy
Authors: Imai M , Arimura H , Nonaka A , Nakamura K , Shioyama Y , Honda H , Hirata H 
Published: June 2015

Purpose:Our goal of this study was to investigate a computational framework for beam angle configurations based on similar cases using treatment‐plan‐related features in lung stereotactic body radiation therapy.Methods:A radiation treatment planning database including 81 lung cancer cases and 10 test cases were employed for development and test of the proposed framework. A lung shape feature, which is a shape similarity of two‐dimensional (2D) lung region using a Dice's similarity coefficient (DSC), was newly introduced as a treatment‐plan‐related feature. First, ten cases with slice levels similar to a test case were selected based on a 2D lung shape similarity at an isocenter plane. Second, five similar cases were chosen using additional treatment‐plan‐related features with respect to lung and spinal cord. Finally, five beam angle configurations of the test case were determined from 5 similar cases by performing an affine linear registration of the lung region between the similar case and the test case. For evaluation of the proposed framework, dose evaluation indices with respect to planning target volume (PTV), lung, and spinal cord were computed to select a usable plan among five similar‐case‐based plans. Dose evaluation indices of usable plans produced by the proposed and conventional frameworks for 10 test cases were compared with original plans designed by radiation oncologists.Results:The average homogeneity index in PTVs and V10 in lung for usable plans made by the proposed framework were statistically lower than those for original plans (p<0.05), whereas there were no statistically significant differences between the conventional framework and original plans in any evaluation indices.Conclusion:The proposed framework with treatment‐plan‐related features had a potential to suggest usable plans, which can produce more homogeneous dose distributions in PTV and lower volumes with more than 10 Gy in lung, compared with the conventional framework.
SU‐E‐T‐698: Simplified Pencil Beam Kernel For Unfiltered Energies
Authors: Erturk M , Kocar C , Tombakoglu M , Gurdalli S 
Published: June 2015

Purpose:Aim of the study was to evaluate pencil beam kernel, with minimum kernel parameters, for unfiltered photon energies by using measured broad beam data.Methods:Double exponential function (A_z*exp(‐a_z*r)+B_z(‐b_z*r), which required 4 parameters for each depth, was chosen as pencil beam kernel function. When first term was assumed as primary dose kernel and the second exponential term was assumed as scattered dose kernel only Bz, which was magnitude of the scattered dose component relative to primary dose component, was leaved as a function of depth. Profile at air was used as intensity data for each depth, so depth dependency of intensity was also neglected. MATLAB optimization toolbox (“fminsearch”) was used to minimize differences between computed and measured profiles. Penalty function was created with global gamma analysis by using 1% — 1mm criteria. Interested dose point threshold was set as 5% of the maximum dose. Profiles of 10×10 field at five standard depths were used as comparison data. Work flow started with suggestion of kernel parameters, then dose distribution of five standard depths was computed and compared with measured data by using gamma analysis, this calculation was iterated until convergence.Results:After convergence, it was seen that Bz could be described as a first order polynomial of depth (R^2=0.985 when parameters were fitted with relevant depth). Then B_z was defined as (b0*r+b1) and kernel was reoptimized. All points on 5×5 and 10×10 field profiles at five depths were in the criteria of 1% — 1mm global gamma analysis. For 20×20 there were no any failed points when criteria was %2–2mm for threshold %20 of the macximum dose.Conclusion:It is possible to reduce pencil beam kernel parametres for unfiltered photon energies. Improvement required for large fields.
SU‐E‐T‐701: Single Isocenter Volumetric Modulated Arc Therapy (VMAT) With Or Without Field Overlap in the Treatment of Left Sided Breast and Regional Lymphatic Tissue: Impact On Surrounding OAR Doses
Authors: Algan O , Hossain S , Lee G , Ahmad S 
Published: June 2015

Purpose:To investigate the impact of field overlap on dosimetric outcomes for patients receiving radiation therapy to the whole breast as well as the supraclavicular and internal mammary nodal regions.Methods:Seven patients with left sided breast cancer were evaluated on this IRB approved study. Four 200° partial arcs were used to optimize single isocenter VMAT plans using 2 different techniques: Technique 1 utilized treatment plans with no field overlap (NFOL) and 30 or 330 degree collimation. Technique 2 utilized 2cm field overlap (FOL) and 30 degree collimation. A single physician contoured all PTV and contralateral breast volumes. The same PTV and OAR volumes were used for both treatment planning techniques. The prescription dose was 46Gy delivered in 23 fractions with a minimum of 95% of the volume receiving 95% of the dose. A two‐sided paired t‐test was used to compare evaluated dosimetric parameters.Results:The mean PTV volume was 923cc (range 589–1218cc). In general, use of FOL resulted in a reduction (though not statistically significant, unless otherwise stated) in OAR dosimetric parameters when compared to NFOL. For left lung, mean dose was 14.3 vs. 13.6Gy, the V20Gy was 23.4% vs. 20.8%, and V30Gy was 10.8% vs. 7.1% (p < 0.01), for NFOL and FOL, respectively. Similarly, for total lung, mean dose was 9.2 vs. 8.8Gy, V20Gy was 11.2% vs. 9.9%, and V30Gy was 5.1 vs. 3.4% (p < 0.01), for heart, mean dose was 4.9 vs. 4.6Gy, V5Gy was 29.7 vs. 27.9%, and the V10Gy was 4.7 vs. 4.0%. Right breast was least impacted with the use of FOL: mean dose 2.6Gy vs. 2.6Gy, D2% of 9.0Gy vs. 9.4Gy (p = 0.5).Conclusion:Use of a 2cm FOL with VMAT treatment plans resulted in reduced doses to the lung and heart with minimal increase in right breast dose.
SU‐E‐T‐702: SIR‐Spheres Dose Vial Activity Assay Cross‐Calibration with An Outside Radiopharmacy
Authors: Gress D , Erwin W 
Published: June 2015

Purpose:To perform a dose calibrator (DC) cross‐calibration for assaying SIR‐Spheres patient doses after out‐sourcing dose dispensing to an outside radiopharmacy.Methods:The setting for our DC (CRC‐15R, Capintec) required for our assay to match that of the outside radiopharmacy (accounting for decay) was determined independently for 20 dispensed doses (v‐vial in acrylic shield). The mean of the twenty settings, plus and minus one and two standard deviations, as well as, minimum and maximum, were computed. For the next 20 doses, the activity was measured using the computed DC settings. From those measurements, a least squares fit of % error with respect to the outside radiopharmacy's specified activity versus DC setting was generated to indicate an optimum single dose calibrator setting for measuring future doses. An ionization chamber survey meter (451B, Fluke Biomedical) was used in a fixed geometry to measure the exposure rate of each of the first 20 dispensed doses, and generate a linear correlation of meter reading versus radiopharmacy‐specified activity, to provide an independent method of verifying that activity.Results:Survey meter measurements demonstrated reliability of the radiopharmacy's specified activities, with R2 equal to 0.99 and a conversion factor (slope) of 0.0584 [mR/hr]/mCi. The range of DC settings yielded activity readout range of ±5.25%. The least squares fit of % error relative to the radiopharmacy's specified activity versus computed DC setting had an R2 value of 0.999 and the fit passed through 0% error very near 63×10. Each data point in the fit was the mean of 20 measurements at each setting.Conclusion:An outside radiopharmacy's assay of SIR‐Spheres doses was validated, and our data suggest that a single DC setting may be used for an in‐house activity assay within approximately 5% of that from the outside radiopharmacy.
SU‐E‐T‐705: Skin Dosimetry Comparisons of CyberKnife and Tomotherapy for Head‐And‐Neck Stereotatic Body Radiotherapy
Authors: Yoon J , Woo J , Park J , Cho S , Lee E , Choi W , Park K , Lee H 
Published: June 2015

Purpose:To perform a comparative evaluation of the skin dose in CyberKnife and Tomotherapy to predict an accurate dose in head‐and‐neck SBRT.Methods:Arbitrarily‐defined planning target volume (PTV) near the skin was drawn on planning CT acquired from an anthropomorphic head‐and‐neck phantom that is used to perform the end‐to‐end test in CyberKnife. Calculation doses were obtained from Multiplan treatment planning system (TPS) using ray‐tracing and monte‐carlo (MC) algorithms for CyberKnife. For Tomotherapy, the skin dose was estimated with convolution superposition (CS) algorithm from Volo TPS. We selected 90% coverage of PTV in 3Gy prescription dose. We compared skin doses near target and at 5 cm far from the target. Optically‐stimulated luminescent dosimeter (OSLD) measurements of radiation dose to the skin over the head‐and‐neck were made during PTV delivery in CyberKnife and Tomotherapy. Individually‐calibrated OSLDs were placed on the surface of the phantom at a number of test positions. The measurement doses were compared with surface doses calculated from ray‐tracing, MC and CS algorithms.Results:The calculated skin doses near target were estimated to be 78∼93% in ray‐tracing, 50∼68% in MC and 78∼97% in CS. Skin doses near target were measured to be 54∼81% of the prescription dose in CyberKnife and to be 89∼104% of the target dose in Tomotherapy. The averaging differences between calculation and measurement values at the skin near target and at 5cm far from the target were 4.7%, 3.3%, and 4.8% in ray‐tracing, MC, and CS, respectively.Conclusion:We verified the skin dose comparisons based on three algorithms used in Cyberknife and Tomotherapy. By the measurement values using OSLD, we found that skin dose could be minimized in CyberKnife compared to using Tomotherapy, which lead to a lower skin dose in head‐and‐neck SBRT. In the aspect of correlation between measured and calculated doses, MC was superior to ray‐tracing and CS
SU‐E‐T‐715: Subacute Effects of Pulsed Low Dose Rate Radiotherapy and Conventional Radiotherapy On Normal Mouse Tissues
Authors: Cvetkovic D , Wang B , Chen L , Ma C 
Published: June 2015

Purpose:Pulsed low‐dose‐rate radiotherapy (PLDR) can be used as a re‐irradiation technique for recurrent cancers. We hypothesized that PLDR induces less toxicity to normal mouse tissues than conventional radiotherapy (CRT) for the same dose and regimen.Methods:Experiment 1: 22 male BALB/c nude mice were randomly assigned into a non‐irradiated control group (n=2), a CRT group (n=10), and a PLDR group (n=10). The mice received 8Gy total body irradiation (TBI) either continuously at a dose rate of 300MU/min (CRT) or in 0.2Gyx40 pulses separated by 3min intervals (PLDR). The mice were weighed daily, sacrificed when terminally ill or by day 12, and various organs were removed, formalin‐fixed, paraffin‐embedded and stained with H&E. Morphological changes were observed under a microscope. Experiment 2: 10 male nude mice were assigned into a control group, a 7Gy CRT, a 7Gy PLDR, an 8Gy CRT, and an 8Gy PLDR group; n=2 for each group. Body weight, urine/feces output, and food and water consumption were recorded daily, mice sacrificed on day 7, and organs collected for histology.Results:Statistically significant differences were found in the weight and survival time (8 vs. 12 days) between the CRT and PLDR groups (Exp 1). The greatest body weight decline in Exp 2 was observed in the 8Gy CRT group. Histopathological analysis revealed atrophy in spleen, bone marrow and small intestine of all irradiated animals. The damage was mild to moderate in PLDR groups, and severe in CRT groups. Additionally, stomach atrophy was seen in all of the CRT cases, but only in 25% of PLDR cases. There was no apparent difference in the level of tissue radiation injury at 7Gy and 8Gy.Conclusion:Our results verified the hypothesis that PLDR reduces the normal tissue toxicity from radiotherapy. Therefore, PLDR is an effective treatment for recurrent cancers.
SU‐E‐T‐722: Technical and Clinical Experience with the 1st Single Room Proton Therapy System
Authors: Klein E , Zhao T , Sun B , Goddu S , Santanam L , Bradley J 
Published: June 2015

Purpose:In December, 2013 we treated our first patient with the Mevion S250 Proton Therapy System. This followed seven months of acceptance testing and commissioning, including; dosimetric data acquisition, safety checks, establishment of QA programs, mechanical and imaging checks, modeling validation, etc.Methods:The Mevion S250 possesses a compact synchrocyclotron attached to a gantry due to its small size (1.8m diameter) and light weight (22 tons). The system includes a 6D robotic couch allowing for any beam trajectory. The system provides 3D‐2D imaging via fixed x‐rays. Our TPS is Varian Eclipse, for which modeling and validation comprised most of the commissioning. The electronic medical record system is Elekta's MOSIAQ 2.5, which provides connectivity for setup, imaging and treatment.Results:The modeling and validation met gamma of 3%/1mm for 98% of points. The imaging quality is superior than our other existing systems. Neutron dose was <1.0mSv/Gy for most clinical fields. The isocentricity of gantry and couch was measured to be ±0.5 and ±0.6mm, respectively. Daily QA is a 30 minute procedure, including; couch isocentricity, interlocks, warning indicators, imaging, and dosimetric checks for options. Output, modulation flatness, range, field symmetry are measured with a single exposure for 3 options. We currently treat 20–24 patients per day and uptime for most months has been >95%. Over the first 14 months, for our first 150 cases, were predominantly; adult CNS, pediatrics (including CSI), lung, and liver. Thorax patients receive weekly scans for adaptive planning.Conclusion:The Mevion S250 has added a vital option to compliment our other modalities within our NCI Comprehensive Cancer Center.
MO‐FG‐303‐01: FEATURED PRESENTATION and BEST IN PHYSICS (THERAPY): Automating LINAC QA: Design and Testing of An Image Acquisition and Processing System Utilizing a Combination of Radioluminescent Phosphors, Embedded X‐Ray Markers and Optical Measurements
Authors: Jenkins C , Naczynski D , Yu S , Xing L 
Published: June 2015

Purpose:The recent development of phosphors to visualize radiation beams from linear accelerators (LINAC) offers a unique opportunity for evaluating radiation fields within the context of the treatment space. The purpose of this study was to establish an automated, self‐calibrating prototype system for performing quality assurance (QA) measurements.Methods:A thin layer of Gd₂O₂S:Tb phosphor and fiducial markers were embedded on several planar faces of a custom‐designed phantom. The phantom was arbitrarily placed near iso‐center on the couch of a LINAC equipped with on‐board megavoltage (MV) and kilovoltage (kV) imagers. A plan consisting of several beams and integrated image acquisitions was delivered. Images of the phantom were collected throughout the delivery. Salient features, such as fiducials, crosshairs and beam edges were then extracted from these images used to calibrate the system, adjust for variations in phantom placement, and perform measurements. Beam edges were visualized by imaging the light generated by the phosphor on the phantom enabling direct comparison with the light field and laser locations. Registration of MV, kV and optical image data was performed using the embedded fiducial markers, enabling comparison of imaging center locations. Measurements specified by TG‐142 were calculated and compared with those obtained from a commercially available QA system.Results:The system was able to automatically extract the location of the fiducials, lasers, light field and radiation field from the acquired images regardless of phantom positioning. It was also able to automatically identify the locations of fiducial markers on kV and MV images. All collected measurements were within TG‐142 guidelines. The difference between the prototype and commercially available system were less than 0.2 mm.Conclusion:The prototype system demonstrated the capability of accurately and autonomously evaluating various TG‐142 parameters independent of operator input and phantom setup.
MO‐FG‐204‐05: Evaluation of a Novel Algorithm for Improved 4DCT Resolution
Authors: Glide‐Hurst C , Klahr P , Briceno J , Chetty I. J. 
Published: June 2015

Purpose:Accurate tumor motion characterization is critical for increasing the therapeutic ratio of radiation therapy. To accommodate the divergent fan‐beam geometry of the scanner, the current 4D‐CT algorithm utilizes a larger temporal window to ensure that pixel values are valid throughout the entire FOV. To minimize the impact on temporal resolution, a cos2 weighting is employed. We propose a novel exponential weighting (“exponential”) 4DCT reconstruction algorithm that has a sharper slope and provides a more optimal temporal resolution.Methods:A respiratory motion platform translated a lung‐mimicking Styrofoam slab with several high and low‐contrast inserts 2 cm in the superior‐inferior direction. Breathing rates (10–15 bpm) and couch pitch (0.06–0.1 A.U.) were varied to assess interplay between parameters. Multi‐slice helical 4DCTs were acquired with 0.5 sec gantry rotation and data were reconstructed with cos2 and exponential weighting. Mean and standard deviation were calculated via region of interest analysis. Intensity profiles evaluated object boundaries. Retrospective raw data reconstructions were performed for both 4DCT algorithms for 3 liver and lung cancer patients. Image quality (temporal blurring/sharpness) and subtraction images were compared between reconstructions.Results:In the phantom, profile analysis revealed that sharper boundaries were obtained with exponential reconstructions at transitioning breathing phases (i.e. mid‐inhale or mid‐exhale). Reductions in full‐width half maximum were ∼1 mm in the superior‐inferior direction and appreciable sharpness could be observed in difference maps. This reduction also yielded a slight reduction in target volume between reconstruction algorithms. For patient cases, coronal views showed less blurring at object boundaries and local intensity differences near the tumor and diaphragm with exponential weighted reconstruction.Conclusion:Exponential weighted 4DCT offers potential for improving image sharpness in 4DCT. Comparisons with true object extent using static CTs of varied phantom positions are necessary to confirm these findings. Future work with additional patient cases is warranted.Research partially sponsored by Philips Healthcare
MO‐FG‐207‐00: Technological Advances in PET/MR Imaging
Authors: Shao Yiping 
Published: June 2015

The use of integrated PET/MRI systems in clinical applications can best benefit from understanding their technological advances and limitations. The currently available clinical PET/MRI systems have their own characteristics. Thorough analyses of existing technical data and evaluation of necessary performance metrics for quality assurances could be conducted to optimize application‐specific PET/MRI protocols. This Symposium will focus on technical advances and limitations of clinical PET/MRI systems, and how this exciting imaging modality can be utilized in applications that can benefit from both PET and MRI.Learning Objectives:

To understand the technological advances of clinical PET/MRI systems
To correctly identify clinical applications that can benefit from PET/MRI
To understand ongoing work to further improve the current PET/MRI technology
Floris Jansen is a GE Healthcare employee.