bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐59: The Effect of Radiotherapy Dose On Immunoadjuvants
Authors: Moreau M , Yasmin‐Karim S , Hao Y , Ngwa W 
Published: July 2016

Purpose:Combining radiotherapy with immunotherapy is a promising approach to enhance treatment outcomes for cancer patients. This in‐vitro study investigated which radiotherapy doses could adversely affect the function of anti‐CD40 mAb, which is one of the key immunoadjuvants under investigations for priming such combination therapy.Methods:Human monocyte derived THP‐1 cells were treated with 100ng/mL of PMA in chamber slides to differentiate into macrophage. The THP‐1 differentiated macrophages were treated with 2uL/ml of the anti‐CD40 mAb and incubated at 37°C and 5% CO2 for 24 hours. Anti‐CD40 mAb treated cells were then irradiated at different doses of x‐rays: (0, 2, 4, 6, 8, and 12) Gy using the Small Animal Radiotherapy Research Platform (SARRP). After radiation, the cells were left at 4°C for 2 hours followed by immunofluorescence assay. A Nikon inverted live‐cell imaging system with fluorescence microscope was used to image the cells mounted on a slide fixed with Dapi. For comparison, an ELISA assay was performed with the antibody added to 3mL of PBS in multiple 10mm dishes. The 10mm dishes were irradiated at different x‐ray dose: (0, 2, 4, 6, 8. 10, 12, and 15) Gy using the SARRP.Results:The anti‐CD40 mAb activating the macrophages starts to lose their viability due to radiation dose between 8Gy to 12Gy as indicated by the immunofluorescence assay. The ELISA assay, also indicated that such high doses could lead to loss of the mAb's viability.Conclusion:This work suggests that high doses like those employed during Stereotactic Ablative Radiotherapy may affect the viability of immunoadjuvants such as anti‐CD 40. This study avails in‐vivo experiments combining radiotherapy with anti‐cd40 to get synergistic outcomes, including in the treatment of metastatic disease.
SU‐F‐T‐60: A Quick Dose Calculation Check for Accuboost Breast Treatment
Authors: Sen A 
Published: July 2016

Purpose:Accuboost treatment planning uses dwell times from a nomogram designed with Monte Carlo calculations for round and D‐shaped applicators. A quick dose calculation method has been developed for verification of the HDR Brachytherapy dose as a second check.Methods:Accuboost breast treatment uses several round and D‐shaped applicators to be used non‐invasively with an Ir‐192 source from a HDR Brachytherapy afterloader after the breast is compressed in a mammographic unit for localization. The breast thickness, source activity, the prescription dose and the applicator size are entered into a nomogram spreadsheet which gives the dwell times to be manually entered into the delivery computer. Approximating the HDR Ir‐192 as a point source, and knowing the geometry of the round and D‐applicators, the distances from the source positions to the midpoint of the central plane are calculated. Using the exposure constant of Ir‐192 and medium as human tissue, the dose at a point is calculated as: D(cGy) = 1.254 × A × t/R2, where A is the activity in Ci, t is the dwell time in sec and R is the distance in cm. The dose from each dwell position is added to get the total dose.Results:Each fraction is delivered in two compressions: cranio‐caudally and medial‐laterally. A typical APBI treatment in 10 fractions requires 20 compressions. For a patient treated with D45 applicators and an average of 5.22 cm thickness, this calculation was 1.63 % higher than the prescription. For another patient using D53 applicators in the CC direction and 7 cm SDO applicators in the ML direction, this calculation was 1.31 % lower than the prescription.Conclusion:This is a simple and quick method to double check the dose on the central plane for Accuboost treatment.
SU‐F‐T‐68: Characterizes of Microdetectors in Electron Beam Dosimetry
Authors: Das I , Andersen A , Akino Y 
Published: July 2016

Purpose:Electron beam dosimetry requires high resolution data due to finite range that can be accomplished with small volume detectors. The small‐field used in advance technologies in photon beam has created a market for microdetectors, however characteristics are significantly variable in photon beams and relatively unknown in electron beam that is investigated in this study.Methods:Among nearly 2 dozen microdetectors that have been investigated in small fields of photon beam, two popular detectors (microDiamond 60019 (PTW)) and W1 plastic scintillator detector (Standard Imaging)) that are tissue equivalent and have very small sensitive volume are selected. Electron beams from Varian linear accelerators were used to investigate dose linearity dose rate dependence, energy dependence, depth dose and profiles in a reference condition in a water phantom. For W1 that has its own Supermax electrometer point by point measurements were performed. For microDiamond, a PTW‐scanning tank was used for both scanning and point dose measurements.Results:W1 detector showed excellent dose linearity (r2 =1.0) from 5–500 MU either with variation of dose rate or beam energy. Similar findings were also observed for microdiamond with r2=1.0. Percent variations in dose/MU for W1 and microDiamond were 0.2–1.1% and 0.4–1.2%, respectively among dose rate and beam energy. This variation was random for microDiamond, whereas it decreased with beam energy and dose rate for W1. The depth dose and profiles were within ±1 mm for both detectors. Both detectors did not show any energy dependence in electron beams.Conclusion:Both microDiamond and W1 detectors provided superior characteristics of beam parameters in electron beam including dose, dose rate linearity and energy independence. Both can be used in electron beam except W1 require point by point measurements and microdiamond requires 1500 MU for initial quenching.
SU‐F‐T‐75: Dosimetry Considerations in the Use of Hanging‐Eye Block for Lesions of the Conjunctiva
Authors: Grelewicz Z , Lee B , Cutright D , Kang Z , Gopalakrishnan M , Sathiaseelan V , Zhang H 
Published: July 2016

Purpose:Superficial lesions in the conjunctiva are frequently treated with en face electrons, using a hanging block to spare dose to the lens of the eye. Dose to the tumor and lens depend on the design and setup of the block and supporting apparatus. We performed in phantom measurements in order to characterize the dose sparing effects of the block as well as the under‐dosing effect under the supporting apparatus for 6 MeV treatment.Methods:The commercial hanging block studied uses a 1.2 cm diameter tungsten cylinder supported by a 3 mm diameter acrylic rod. Point dose measurements under the hanging block, under an unblocked part of the field, and under the acrylic rod were performed using MOSFET detectors. In addition, EBT3 film was used for both PDD and profile measurements at a depth in phantom of 3 mm for both 105 and 103 cm SSD.Results:MOSFET measurements reported a dose reduction of 95% under the tungsten block when using an SSD of 103 cm, and 86% when using an SSD of 105 cm at a depth in phantom of 3 mm. Film measurements showed that the area under the acrylic rod may be under‐dosed by as much as 30% when using 103 SSD. MOSFET measurements confirmed that when using an SSD of 103 cm, the area under the acrylic rod is under‐dosed by up to 30% at 3mm depth, compared to the unblocked part of the field.Conclusion:The effectiveness of the commercial hanging block apparatus depends on setup, with 95% lens sparing possible with an SSD of 103 cm. This short SSD is necessary for sharp penumbra. At this SSD, substantial under‐dosing under the acrylic support rod is possible. This must be mitigated with either feathering, or using an alternative method of support for the tungsten block.
SU‐F‐T‐77: A Novel Test for Coincidence Between Light Fields and Electron Radiation Fields
Authors: Gibbard G , Shang C , Khanal S 
Published: July 2016

Purpose:To validate a novel real time quality assurance device, as a means to test coincidence of light fields to electron radiation fields. Method and Materials: Use a Raven™ (LAP of America Laser Applications) detector, both light fields and electron radiation fields of various electron cones and cutouts from two Clinacs (Varian Medical) were sensed by the phosphor screen and registered by a CCD camera of the device. During measurements, the screen surface of Raven was placed at ISO center level facing the radiation field at any setup angle. Subsequently the light field and the electron radiation field (with 100 MU) were captured separately by the device. The measurements were then analyzed using the Raven software with a maximal 25 by 25 cm^2 field size and 0.25 mm resolution. The results were further compared against those using chromic graphic film (EBT3). To ensure consistence only the dimensions through the central axis were recorded. All the films were analyzed with Dose Lab Pro™ v6.70. Coincidence comparisons were done within the tests on one Clinac and between the two Clinacs.Results:The similar difference means of the field coincidence are indicated from the 18 samples by EBT films and 34 by the Raven as 1.33 ± 0.87 mm verses 1.06 ± 0.58 mm (p = 0.74). The mean differences of the field coincidence between the two Clinacs, 1.16 ± 0.68 mm (n=16) and 1.16 ± 0.48 mm (n=18) respectively, also suggest no statistical difference (p= 0.40).Conclusion:The Raven™ is a comparable quality verification device to the chromic graphic film (EBT3) in checking the coincidence between light and electron radiation fields. In this investigation, the Raven device provided highly reproducible results with real time analysis. Further improvements in its resolution and automatic analyzing capability are warranted.
SU‐F‐T‐83: Infant Total Skin Electron Therapy Using Five Fields Technique
Authors: Saleh H , Howlin T , Massey V 
Published: July 2016

Purpose:We were presented with a 9 month old boy with Relapsed Acute Myeloid Leukemia (AML) involving the skin. The plan was to treat the entire skin using 6 MeV electrons with the infant under complete anesthesia. The purpose of this work is to commission the 6 MeV electron beam and to develop a technique that can be used to deliver total skin dose to infants with minimal patient immobilization.Methods:A baby mannequin phantom that mimics the child's length was used to determine the best technique to treat the infant. The 76 cm long phantom was placed on the floor. The phantom was placed in four unique immobilization devices to simulate four different treatment positions (anterior, posterior, left lateral and right lateral). Radiochromic films were used to determine beam profile in both axial and radial directions, and percent depth dose (PDD). Absolute calibration of the machine output at 214 cm distance was measured using an Exradin A11 parallel‐plate ion chamber. A 1.0 cm plexiglass scatter plate was inserted in the collimator. Mosfet dosimeters were used for dose verification for phantom and and patient.Results:At 214 cm source to surface distance (SSD) using gantry angle of + 20o from vertical beam flatness is + 10% in the radial direction over a region of 70 cm and + 4% in the axial direction over 60 cm. A five field arrangement was determined to optimally deliver the desired dose with > 90% uniformity. The fifth field was used to boost the head vertex.Conclusion:It is possible to treat sedated infants with total skin dose using five positions. Four positions were enough to cover the body and the fifth position boosts the vertex of the head. All fractions can be reproduced accurately daily because of the patient's stable immobilization.
SU‐F‐T‐88: Field's Metal for Electron Beam Inserts and Blocks
Authors: Ha J , Gallogly A , Cui J , Jennelle R 
Published: July 2016

Purpose:The aim of this work is to show that Field's metal can be used as a viable alternative material to lead‐based low‐melting temperature alloys (e.g., Cerrobend) for electron beam inserts and blocks. The goal is to eliminate exposure risks associated with lead and cadmium.Methods:Field's metal (51% Indium, 32.5% Bismuth, 16.5% Tin) is a low‐melting point eutectic alloy, and is proposed as a lead‐free replacement for Cadmium‐free alloy (52.5% Bismuth, 32% Lead, 15.5% Tin). The experiments were done using a Varian 21EX linac equipped with 6, 9, 12, and 16 MeV beams. The 10×10 cone was used with 1.8cm thick insert made of Fields metal, Cd‐Free alloy or open field. The transmitted radiation was measured using a diode at various depths in water. Block transmission factor (BTF) is determined as the ratio of maximum transmission radiation dose over the dose at dmax of the open field.Results:The data shows BTFs for both alloys are very similar, well below 5% for 6, 9, and 12 MeV beams. For 16 MeV, the BTF of the Fields metal is about 5.3%; the Cd‐free metal 4.2%. The peak dose of the transmitted radiation occurs less than 1 cm below the water surface, at a much shallower depth than the dmax of the electron beam in the open field. The beam profile shows the maximum block transmission is along the central axis of the beam.Conclusion:The present study shows that Fields metal can be used to make electron cutouts and blocks for 6, 9, 12, and 16 MeV beams. Because it has a similar density as other lead‐based alloys, the same thickness of Fields metal would be adequate for shielding the electron beams. This means that it can be used as a replacement without modification to the existing block holder.
SU‐F‐T‐97: Outlier Identification in Radiation Therapy Knowledge Modeling
Authors: Sheng Y , Ge Y , Yuan L , Li T , Yin F , Wu Q 
Published: July 2016

Purpose:To investigate the impact of outliers on knowledge modeling in radiation therapy, and develop a systematic workflow for identifying and analyzing geometric and dosimetric outliers using pelvic cases.Methods:Four groups (G1‐G4) of pelvic plans were included: G1 (37 prostate cases), G2 (37 prostate plus lymph node cases), and G3 (37 prostate bed cases) are all clinical IMRT cases. G4 are 10 plans outside G1 re‐planned with dynamic‐arc to simulate dosimetric outliers. The workflow involves 2 steps: 1. identify geometric outliers, assess impact and clean up; 2. identify dosimetric outliers, assess impact and clean up.1. A baseline model was trained with all G1 cases. G2/G3 cases were then individually added to the baseline model as geometric outliers. The impact on the model was assessed by comparing leverage statistic of inliers (G1) and outliers (G2/G3). Receiver‐operating‐characteristics (ROC) analysis was performed to determine optimal threshold. 2. A separate baseline model was trained with 32 G1 cases. Each G4 case (dosimetric outliers) was then progressively added to perturb this model. DVH predictions were performed using these perturbed models for remaining 5 G1 cases. Normal tissue complication probability (NTCP) calculated from predicted DVH were used to evaluate dosimetric outliers’ impact.Results:The leverage of inliers and outliers was significantly different. The Area‐Under‐Curve (AUC) for differentiating G2 from G1 was 0.94 (threshold: 0.22) for bladder; and 0.80 (threshold: 0.10) for rectum. For differentiating G3 from G1, the AUC (threshold) was 0.68 (0.09) for bladder, 0.76 (0.08) for rectum. Significant increase in NTCP started from models with 4 dosimetric outliers for bladder (p<0.05), and with only 1 dosimetric outlier for rectum (p<0.05).Conclusion:We established a systematic workflow for identifying and analyzing geometric and dosimetric outliers, and investigated statistical metrics for detecting. Results validated the necessity for outlier detection and clean‐up to enhance model quality in clinical practice.Research Grant: Varian master research grant
SU‐F‐T‐100: Development and Implementation of a Treatment Planning Tracking System Into the Radiation Oncology Clinic
Authors: Kabat C , Cline K , Li Y , Ha C , Stathakis S 
Published: July 2016

Purpose:With increasing numbers of cancer patients being diagnosed and the complexity of radiotherapy treatments rising it's paramount that patient plan development continues to stay fluid within the clinic. In order to maintain a high standard of care and clinical efficiency the establishment of a tracking system for patient plan development allows healthcare providers to view real time plan progression and drive clinical workflow. In addition, it provides statistical datasets which can further identify inefficiencies within the clinic.Methods:An application was developed utilizing Microsoft's ODBC SQL database engine to track patient plan status throughout the treatment planning process while also managing key factors pertaining to the patient's treatment. Pertinent information is accessible to staff in many locations, including tracking monitors within dosimetry, the clinic network for both computers and handheld devices, and through email notifications. Plans are initiated with a CT and continually tracked through planning stages until final approval by staff. Patient's status is dynamically updated by the physicians, dosimetrists, and medical physicists based on the stage of the patient's plan.Results:Our application has been running over a six month period with all patients being processed through the system. Modifications have been made to allow for new features to be implemented along with additional tracking parameters. Based on in‐house feedback, the application has been supportive in streamlining patient plans through the treatment planning process and data has been accumulating to further improve procedures within the clinic.Conclusion:Over time the clinic will continue to track data with this application. As data accumulates the clinic will be able to highlight inefficiencies within the workflow and adapt accordingly. We will add in new features to help support the treatment planning process in the future.
SU‐F‐T‐116: Predicting IQ and the Risk of Hearing Loss Following Proton Versus Photon Radiotherapy for Pediatric Brain Tumor Patients
Authors: Fortin D , Ng A , Tsang D , Sharpe M , Laperriere N , Hodgson D 
Published: July 2016

Purpose:The increased sparing of normal tissues in intensity modulated proton therapy (IMPT) compared to photon intensity modulated radiotherapy (IMRT) in brain tumor treatments should translate into improved neurocognitive outcomes. Models were used to estimate the intelligence quotient (IQ) and the risk of hearing loss 5 years post radiotherapy and to compare outcomes of proton against photon in pediatric brain tumors.Methods:Patients who had received radical IMRT were randomly selected from our retrospective database: 10 cases each of craniopharyngioma, ependymoma and medulloblastoma, and 20 cases of glioma. The existing planning CT and contours were used to generate IMPT plans. The RBE‐corrected dose to brain structures and cochleas were calculated for both IMPT and IMRT. A model was applied to estimate IQ using a Markov chain Monte Carlo technique. The reported incidence of hearing loss as a function of cochlear dose was used to estimate the rate of occurrence.Results:The average brain dose was less in all IMPT plans compared to IMRT: ranging from a 6.7% reduction (P=0.003) in the case of medulloblastoma to 38% (P=0.007) for craniopharyngioma. This dose reduction translated into a gain in IQ of 1.9 points on average for protons vs photons for the whole cohort at 5 years post‐treatment (P=0.011). In terms of specific diseases, the gains in IQ ranged from 0.8 points for medulloblastoma, to 2.7 points for craniopharyngioma. Hearing loss probability was evaluated on a per‐ear‐basis and was found to be systematically less for proton versus photon: overall 2.9% versus 7.2% (P < 0.001).Conclusion:A novel method was developed to predict neurocognitive outcomes in pediatric brain tumor patients on a case‐by‐case basis. A modest gain in IQ was systematically observed for proton in all patients. Given the uncertainties within the model used and our reinterpretation, these gains may be underestimated.
SU‐F‐T‐129: Impact of Radial Fluctuations in RBE for Therapeutic Proton Beams
Authors: Butkus M , Palmer T 
Published: July 2016

Purpose:To evaluate the off axis relative biological effectiveness (RBE) for actively scanned proton beams and determine if a constant radial RBE can be assumed.Methods:The PHITS Monte Carlo code paired with a microscopic analytical function was used to determine probability distribution functions of the lineal energy in 0.3µm diameter spheres throughout a water phantom. Twenty million primary protons were simulated for a 0.6cm diameter pencil beam. Beam energies corresponding to Bragg Peak depths of 50, 100, 150, 200, 250, and 300mm were used and evaluated transversely every millimeter and radially for annuli of 1.0, 2.0, 3.0, 3.2, 3.4, 3.6, 4.0, 5.0, 10.0, 15.0, 20.0 and 25.0mm outer radius. The acquired probability distributions were reduced to dose‐mean lineal energies and applied to the modified microdosimetric kinetic model, for human submandibular gland (HSG) cells, to calculate relative biological effectiveness (RBE) compared to 60Co beams at the 10% survival threshold.Results:RBE was generally seen to increase as distance from the central axis (CAX) increased. However, this increase was only seen in low dose regions and its overall effects on the transverse biological dose remains low. In the entrance region of the phantom (10mm depth), minimum and maximum calculated RBEs varied between 15.22 and 18.88% for different energies. At the Bragg peak, this difference ranged from 3.15 to 26.77%. Despite these rather large variations the dose‐weighted RBE and the CAX RBE varied by less than 0.14% at 10mm depth and less than 0.16% at the Bragg peak. Similarly small variations were found at all depths proximal of the Bragg peak.Conclusion:Although proton RBE does vary radially, its overall effect on biological dose is minimal and the use of a radially constant RBE in treatment planning for scanned proton beams would not produce large errors.
SU‐F‐T‐142: An Analytical Model to Correct the Aperture Scattered Dose in Clinical Proton Beams
Authors: Sun B , Liu S , Zhang T , Zhao T , Yang D , Grantham K , Goddu S , Bradley J , Mutic S 
Published: July 2016

Purpose:Apertures or collimators are used to laterally shape proton beams in double scattering (DS) delivery and to sharpen the penumbra in pencil beam (PB) delivery. However, aperture‐scattered dose is not included in the current dose calculations of treatment planning system (TPS). The purpose of this study is to provide a method to correct the aperture‐scattered dose based on an analytical model.Methods:A DS beam with a non‐divergent aperture was delivered using a single‐room proton machine. Dose profiles were measured with an ion‐chamber scanning in water and a 2‐D ion chamber matrix with solid‐water buildup at various depths. The measured doses were considered as the sum of the non‐contaminated dose and the aperture‐scattered dose. The non‐contaminated dose was calculated by TPS and subtracted from the measured dose. Aperture scattered‐dose was modeled as a 1D Gaussian distribution. For 2‐D fields, to calculate the scatter‐dose from all the edges of aperture, a sum of weighted distance was used in the model based on the distance from calculation point to aperture edge. The gamma index was calculated between the measured and calculated dose with and without scatter correction.Results:For a beam with range of 23 cm and aperture size of 20 cm, the contribution of the scatter horn was ∼8% of the total dose at 4 cm depth and diminished to 0 at 15 cm depth. The amplitude of scatter‐dose decreased linearly with the depth increase. The 1D gamma index (2%/2 mm) between the calculated and measured profiles increased from 63% to 98% for 4 cm depth and from 83% to 98% at 13 cm depth. The 2D gamma index (2%/2 mm) at 4 cm depth has improved from 78% to 94%.Conclusion:Using the simple analytical method the discrepancy between the measured and calculated dose has significantly improved.