bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sci‐Thur AM: YIS – 09: Treatment Time Optimization for Trajectory‐Based Deliveries
Authors: Wilson Byron , Gete Ermias 
Published: August 2016

Introduction:Couch‐gantry trajectory based deliveries are capable of producing high quality Stereotactic Radiosurgery (SRS) treatments in a time efficient manner. In this work we present two methods for treatment time optimization of these deliveries.Methods:Dosimetrically optimal plans were calculated by optimizing MLC and dose rates along a trajectory which encapsulates 4π geometry. This trajectory was used to benchmark time optimization methods. Two methods of treatment time optimization were developed in this study. The first of which relies on a trajectory which samples phase space variably dependent on a selected sampling frequency. Treatment plans were created with decreased sampling frequencies until the treatment quality was deleteriously effected and the most time efficient delivery was selected. The second method uses a gradient descent algorithm to remove time inefficient sections of a trajectory and subsequently re‐optimizes the MLC and dose rates to form a new, time optimized trajectory.Results:Both methods were capable of producing treatment plans which were dose equivalent to the benchmark 4π geometry plan. The methods reduced treatment time of 12Gy fractions by 18% and 13% for the first and second method respectively. Both methods had a more pronounced time saving benefits for 2Gy fractions, for which delivery time was decreased by 53% and 34% for the first and second method respectively.Conclusion:The methods presented were capable of producing highly conformal SRS treatment plans. These treatments took an average time of 109 seconds for fractionated deliveries and 394 seconds as single fraction deliveries.
Poster – 13: Evaluation of an in‐house CCD camera film dosimetry imaging system for small field deliveries
Authors: Lalonde Michel , Alexander Kevin , Olding Tim , Schreiner L. John , Kerr Andrew T. 
Published: August 2016

Purpose:Radiochromic film dosimetry is a standard technique used in clinics to verify modern conformal radiation therapy delivery, and sometimes in research to validate other dosimeters. We are using film as a standard for comparison as we improve high‐resolution three‐dimensional gel systems for small field dosimetry; however, precise film dosimetry can be technically challenging. We report here measurements for fractionated stereotactic radiation therapy (FSRT) delivered using volumetric modulated arc therapy (VMAT) to investigate the accuracy and reproducibility of film measurements with a novel in‐house readout system. We show that radiochromic film can accurately and reproducibly validate FSRT deliveries and also benchmark our gel dosimetry work.Methods:VMAT FSRT plans for metastases alone (PTVMET) and whole brain plus metastases (WB+PTVMET) were delivered onto a multi‐configurational phantom with a sheet of EBT3 Gafchromic film inserted mid‐plane. A dose of 400 cGy was prescribed to 4 small PTVMET structures in the phantom, while a WB structure was prescribed a dose of 200 cGy in the WB+PTVMET iterations. Doses generated from film readout with our in‐house system were compared to treatment planned doses. Each delivery was repeated multiple times to assess reproducibility.Results and Conclusions:The reproducibility of film optical density readout was excellent throughout all experiments. Doses measured from the film agreed well with plans for the WB+PTVMET delivery. But, film doses for PTVMET only deliveries were significantly below planned doses. This discrepancy is due to stray/scattered light perturbations in our system during readout. Corrections schemes will be presented.
Poster ‐ 15: Air kerma rate measurements using a cylindrical free‐air ionization chamber on the 05B1‐1 beamline at the Canadian Light Source
Authors: Anderson Danielle , Siegbahn Albert , Fallone Gino , Warkentin Brad 
Published: August 2016

Purpose:The BioMedical Imaging and Therapy (BMIT) beamlines at the Canadian Light Source offer the opportunity for investigating novel imaging and therapy applications of synchrotron radiation. A necessary component in advancing this research, and in progressing toward clinical applications, is the availability of accurate dosimetry that is traceable to a standards institution. However, dosimetry in this setting is challenging. These beams are typically small, non‐uniform, and highly intense. This work describes air kerma rate measurements on a BMIT beamline using a free‐air ionization chamber (FAC).Methods:The measurements were taken at the 05B1‐1 beamline (∼8 – 100 keV) for several beam qualities with mean energies between 20.0 and 84.0 keV. The Victoreen Model 480 cylindrical FAC, with a specially fabricated 0.52 mm diameter aperture, was used to measure air kerma rates. The required correction factors were determined using a variety of methods: tabulated data, measurements, theoretical calculations and Monte Carlo simulations (EGSnrc user code egs_fac).Results:The experimental air kerma rates measured between 0.270 ± 13.6% and 312 ± 2.7% Gy/min. At lower energies (low filtration), the most impactful correction factors were those for ion recombination and for x‐ray attenuation.Conclusions:These measurements marked the first absolute dosimetry performed at the BMIT beamlines. The experimental and Monte Carlo methods developed will allow air kerma rates to be measured under other experimental conditions, provide a benchmark to which other dosimeters will be compared, and provide a reference for imaging and therapy research programs on this beamline.
Poster ‐ 18: New features in EGSnrc for photon cross sections
Authors: Ali Elsayed , Mainegra‐Hing Ernesto , Rogers David W.O. 
Published: August 2016

Purpose:To implement two new features in the EGSnrc Monte Carlo system. The first is an option to account for photonuclear attenuation, which can contribute a few percent to the total cross section at the higher end of the energy range of interest to medical physics. The second is an option to use exact NIST XCOM photon cross sections.Methods:For the first feature, the photonuclear total cross sections are generated from the IAEA evaluated data. In the current, first‐order implementation, after a photonuclear event, there is no energy deposition or secondary particle generation. The implementation is validated against deterministic calculations and experimental measurements of transmission signals. For the second feature, before this work, if the user explicitly requested XCOM photon cross sections, EGSnrc still used its own internal incoherent scattering cross sections. These differ by up to 2% from XCOM data between 30 keV and 40 MeV. After this work, exact XCOM incoherent scattering cross sections are an available option. Minor interpolation artifacts in pair and triplet XCOM cross sections are also addressed. The default for photon cross section in EGSnrc is XCOM except for the new incoherent scattering cross sections, which have to be explicitly requested. The photonuclear, incoherent, pair and triplet data from this work are available for elements and compounds for photon energies from 1 keV to 100 GeV.Results:Both features are implemented and validated in EGSnrc.Conclusions: The two features are part of the standard EGSnrc distribution as of version 4.2.3.2.
Poster ‐ 34: Clinical Implementation of Prone Breast Treatment
Authors: Jiang Runqing , Fleming Katrina , Kobeleva Sofya , Osei Ernest 
Published: August 2016

Purpose:Prone breast treatment is used to reduce acute and late toxicities for large or pendulous breast patients. This study developed and implemented the clinical workflow of prone breast radiotherapy treatment.Methods:Varian kVue Access360™ Prone Breast Couchtop was used as prone breast board. The treatment planning (TP)is performed in Eclipse TP system. TP comparisons between supine deep inspiration breathing hold (DIBH) and prone breast; prone forward field‐in‐field (FinF) planning and inverse IMRT planning were performed and discussed. For the daily setup, breast coverage was assessed in the room using light field and MV imaging was used at day 1 and weekly.Results:The first ten patients are CT scanned and planned both supine and prone. The coverage was all excellent for supine DIBH plan and prone breast plan. The plan in the prone position demonstrated improvements in lung sparing comparing to the DIBH plan. Both forward FinF plan and inverse IMRT plan achieved acceptable coverage of the breast, and heart dose is comparable. Considering the daily setup variations and MLC leakage, forward FinF plan was recommended for routine clinical use. The procedure has been tested in phantom and patients were treated clinically.Conclusions:Prone breast irradiation has been advocated for women with large pendulous breasts in order to decrease acute and late toxicities. The workflow for prone breast radiation therapy has been developed and the technique is ready to treat patients.
Poster ‐ 37: Pre‐clinical geometric, dosimetric and timing assessment of head and neck OARs using an in‐house atlas‐based auto‐segmentation (ABAS) tool
Authors: Khawandanh Eman , McVicar Nevin , Duzenli Cheryl 
Published: August 2016

Purpose:This study aims to validate the geometric and dosimetric performance of our in‐house ABAS tool using manual inter‐observer variation as benchmark data.Materials and methods:An in‐house ABAS constructed, using MIM MaestroTM version 6.5, from 36 previously treated head and neck cases. 15 OARs of eight nasopharynx patients were segmented via three observers from the same institution and using the in‐house ABAS. Percentage of volume differences (ΔV%,), degree of overlap (DICE), distance‐to‐agreement and the standard deviation of absolute dose difference ΔD SD(Gy) among the eight cases [ΔDmax SD(Gy) for serial organs and ΔDmean SD(Gy) for parallel organs] were compared between the manual segmentation and original ABAS contours for each OAR.Results:The geometric results indicated that ABAS ΔV% was within 1SD from the manual segmentation. DICE showed that manual segmentation marginally outperformed ABAS in the delineation of parotid glands, submandibular glands, and laryngopharynx, but ABSA performed as well as the manual segmentation or better for all other structures. The distance‐to‐agreement was <1.5 cm for 87% of ABAS structures. From a dosimetric perspective, only ABAS salivary glands demonstrated higher ΔD SD(Gy) compared to manual segmentation. For all other structures ABAS results were similar or better than the manual segmentation. The average time to segment a complete H&N OAR set was <3minutes versus 30minutes for manual segmentation.Conclusion:ABAS is a practical time‐saving tool. This study indicated up 90% time‐saving of the operator time per case. ABAS geometric and dosimetric results were within ±1SD inter‐observer variation for most of the structures.
Poster ‐ 54: Development and Evaluation of Normal Tissue Objective Parameters and Avoidance Regions for Prostate Bed VMAT Treatments
Authors: Hudon Luc , Pierce Greg , Roumeliotis Michael 
Published: August 2016

Purpose:A retrospective study was conducted to determine optimal NTO parameters on five patients that were treated with radical prostate doses of 66 Gy in 33 fractions to the prostate bed. The purpose of this work is to evaluate the effectiveness of various NTO settings and also provide insight into whether the use of multiple sparing techniques is beneficial or redundant for a given site.Methods:The effect of varying the NTO parameters were systematically examined in conjunction with the option of an avoidance region: a “ring” structure around the planning target volume. Within each of these groups, four plans were made; three with varying NTO settings as well as a fourth control plan not using the NTO. The three NTO settings used were the Varian default values, the automatic setting (a selectable option in the NTO function), and a developed set of test parameters (Manual NTO).Results:The site‐specific NTO plans showed the greatest improvement regardless of whether they were used in combination with the ring structure. The most striking improvement in OAR sparing occurred when using the Manual NTO settings without the ring structure. In this setting, the average reduction in mean bladder dose was 473 cGy. The automatic NTO and Varian default settings produced improvements of 146 cGy and 12 cGy, respectively.Conclusion:The use of site‐specific NTO parameters produced plans with marked improvement to normal tissue sparing in comparison to plans using the Varian default settings or the automatic NTO.
Poster ‐ 56: Preliminary comparison of FF‐ and FFF‐VMAT for prostate plans with higher rectal dose
Authors: Liu Baochang , Darko Johnson , Osei Ernest 
Published: August 2016

Purpose:A recent retrospective study found 53 patients previously treated to 78Gy/39 using flattened filtered (FF) 6X‐VMAT at GRRCC had rectal DVH more than one standard deviation higher than the average. This study was to investigate if using 6FFFor10FFF beams could reduce these DVHs without compromising target coverage.Methods:Twenty patients’ plans were re‐planed with 2‐arc 6X‐VMAT, 6FFF‐VMAT and 10FFF‐VMAT using the Eclipse TPS following departmental protocol. All plans had the same optimization and normalization, and were evaluated against the acceptance criteria from the QUANTEC and Emami. Statistical differences in the mean dose to OARs (Dm) and PTV homogeneity index (HI) between energies were tested using the paired sample Wilcoxon signed rank statistical method (p<0.05). Beam delivery accuracy was checked on five patients using portal dosimetry (PD).Results:The PTV HI for the 10FFF shows no statistical difference from the 6X. All the OARs, except left femoral head with 6FFF, have significantly lower Dm using 6FFF and 10FFF. There is no difference in the maximum doses to rectum and bladder and are limited by the prescribed doses. Measurements show good agreements in the gamma evaluation (3%/3mm) for all energies.Conclusion:This preliminary study shows that doses to the OARs are reduced using 10FFF for the same target coverage. The plans using 6FFF result in lower doses to some OARs, and statistically different PTV HI. All plans showed very good agreement with measurements.
Poster ‐ 57: Statistical analysis of setup correction for radical IMRT lung patients on a treatment couchtop with six degrees of freedom
Authors: Cisa‐Pare Elisabeth , Ali Elsayed , Nyiri Balazs 
Published: August 2016

Purpose:To characterize the distributions of setup corrections for radical IMRT lung patients treated on a couchtop with six degrees of freedom (6DOF).Methods:Translational and rotational setup corrections were retrospectively analyzed for patients treated on the HexaPODTM 6DOF couchtop. Conventional and hypo‐fractioned radical IMRT lung treatments were included, for a total of 152 patients and 2,042 fractions. The distribution of setup corrections was analyzed for each DOF. Potential correlations between pairs of corrections were examined and possible causes identified. Intra‐patient variability of setup corrections was characterized.Results:For lateral, longitudinal and vertical setup corrections, the mean ± 1 S.D. (in mm) were: −0.6 ± 3.8, 2.8 ± 5.1, and 1.1 ± 3.9. Each of the three means is statistically significant from the theoretical population mean of zero (p<0.01). For rotations, the means were within 0.1° from zero, with a standard deviation of 1.3°. Moderate correlation (r = −0.45) was observed between longitudinal and pitch corrections, which can be caused by changes in the spinal column position, to which registration is mostly done. The standard deviation for intra‐patient corrections varies among patients: 2 – 10 mm for translations and 0.5 – 3° for rotations. Intra‐patient variability in translations has a positive correlation with that in rotations.Conclusions:In 6DOF setup corrections for lung patients, systematic translational corrections were observed, with moderate correlation between longitudinal and pitch corrections. Careful setups and custom immobilization may help reduce such offsets, correlations, and intra‐patient setup variability.
Sci‐Fri AM: Quality, Safety, and Professional Issues 07: Global Medical Physics Efforts: Closing the Gap
Authors: Van Dyk Jacob (Jake) 
Published: August 2016

Purpose:There is an increasing awareness of the disparity in Medical Physics needs between high income countries (HICs) and low‐to‐middle income countries (LMICs). This is especially evident with the growing incidence of cancer in LMICs. Projections from the recent Lancet Oncology Commission on Expanding Global Access to Radiotherapy indicate that an additional 22,000 Medical Physicists will be required by 2035 to provide uniform access to radiation therapy globally. This paper addresses possibilities and challenges associated with closing the Medical Physics gap between HICs and LMICs.Methods:Medical Physics and Oncology related organizations involved in providing support to enhance cancer therapy in LMICs were reviewed, especially as related to education, training and human resource development.Results:More than 35 organizations involved in addressing the cancer crisis in LMICs were found. Of these, 16 involve Medical Physics activities, with 7 being specific Medical Physics‐related organizations. Ten of the 16 are involved in some LMIC activities with 6 having a major emphasis on LMIC contexts.Conclusions:The development of Medical Physics human resource capacity is a major challenge for LMICs. Fifty‐five countries have no radiation therapy capabilities and by implication no capacity to train Medical Physicists. Overt attention with structured and altruistic actions by HIC contexts will help make inroads into the LMIC needs. Clear options throughout career structures in support of global health considerations combined with strong partnerships between interested parties in HICs and LMICs will enhance the development of safe and resource‐appropriate strategies for advancing Medical Physics capabilities.
Sci‐Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques ‐ 08: Retrospective Dose Accumulation Workflow in Head and Neck Cancer Patients Using RayStation 4.5.2
Authors: Wong Olive , Chan Biu , Moseley Joanne , McNiven Andrea , Lindsay Patricia , Bissonnette Jean‐Pierre , Waldron John , Giuliani Meredith , Zhang Beibei 
Published: August 2016

Purpose:We have developed a semi‐automated dose accumulation workflow for Head and Neck Cancer (HNC) patients to evaluate volumetric and dosimetric changes that take place during radiotherapy. This work will be used to assess how dosimetric changes affect both toxicity and disease control, hence inform the feasibility and design of a prospective HNC adaptive trial.Methods:RayStation 4.5.2 features deformable image registration (DIR), where structures already defined on the planning CT image set can be deformably mapped onto cone‐beam computed tomography (CBCT) images, accounting for daily treatment set‐up shifts and changes in patient anatomy. The daily delivered dose can be calculated on each CBCT and mapped back to the planning CT to allow dose accumulation. The process is partially automated using Python scripts developed in collaboration with RaySearch.Results:To date we have performed dose accumulation on 18 HNC patients treated at our institution during 2013–2015 under REB approval. Our semi‐automated process establishes clinical feasibility. Generally, dose accumulation for the entire treatment course of one case takes 60–120 minutes: importing all CBCTs requires 20–30 minutes as each patient has 30 to 40 treated fractions; image registration and dose accumulation require 60–90 minutes. This is in contrast to the process without automated scripts where dose accumulation alone would take 3–5 hours.Conclusions:We have developed a reliable workflow for retrospective dose tracking in HNC using RayStation. The process has been validated for HNC patients treated on both Elekta and Varian linacs with CBCTs acquired on XVI and OBI platforms respectively.
Sci‐Sat AM: Radiation Dosimetry and Practical Therapy Solutions ‐ 01: Optimization of an organic field effect transistor for radiation dosimetry measurements
Authors: Syme Alasdair 
Published: August 2016

Purpose:To use Monte Carlo simulations to optimize the design of an organic field effect transistor (OFET) to maximize water‐equivalence across the diagnostic and therapeutic photon energy ranges.Methods:DOSXYZnrc was used to simulate transport of mono‐energetic photon beams through OFETs. Dose was scored in the dielectric region of devices and used for evaluating the response of the device relative to water. Two designs were considered: 1. a bottom‐gate device on a substrate of polyethylene terephthalate (PET) with an aluminum gate, a dielectric layer of either PMMA or CYTOP (a fluorocarbon) and an organic semiconductor (pentacene). 2. a symmetric bilayer design was employed in which two polymer layers (PET and CYTOP) were deposited both below the gate and above the semiconductor to improve water‐equivalence and reduce directional dependence. The relative thickness of the layers was optimized to maximize water‐equivalence.Results:Without the bilayer, water‐equivalence was diminished relative to OFETs with the symmetric bilayer at low photon energies (below 80 keV). The bilayer's composition was designed to have one layer with an effective atomic number larger than that of water and the other with an effective atomic number lower than that of water. For the particular materials used in this study, a PET layer 0.1mm thick coupled with a CYTOP layer of 900 nm provided a device with a water‐equivalence within 3% between 20 keV and 5 MeV.Conclusions:organic electronic devices hold tremendous potential as water‐equivalent dosimeters that could be used in a wide range of applications without recalibration.
Sci‐Sat AM: Radiation Dosimetry and Practical Therapy Solutions ‐ 02: Dosimetric effects of gold nanoparticle surface coatings
Authors: Koger Brandon , Kirkby Charles 
Published: August 2016

Introduction:Gold nanoparticles (GNPs) can enhance radiation therapy within a tumour, increasing local energy deposition under irradiation, but experimental evidence suggests the enhancement is not as large as predicted by dose enhancement alone. Many studies neglect to account for surface coatings that are frequently used to optimize GNP uptake and biological distribution. This study uses Monte Carlo methods to investigate the consequences on local dose enhancement due to including these surface coatings.Methods:Using the PENELOPE Monte Carlo code system, GNP irradiation was simulated both with and without surface coatings of polyethylene glycol (PEG) of various molecular weights. Dose was scored to the gold, coating, and surrounding water, and the dosimetric differences between these scenarios were examined.Results:The simulated PEG coating absorbs a large portion of the energy that would otherwise be deposited in the medium. The mean dose to water was reduced by up to 2.5, 3.5, and 4.5% for GNPs of diameters 50, 20, and 10 nm, respectively. This effect was more pronounced for smaller GNPs, thicker coatings, and low photon source energies where the enhancement due to GNPs is the greatest. The molecular weight of the coating material did not have a significant impact on the dose.Conclusions:The inclusion of a coating material in GNP enhanced radiation may reduce the dose enhancement due to the nanoparticles. Both the composition and size of the coating play a role in the level of this reduction and should be considered carefully.