SUFT78: Minimum Data Set of Measurements for TG 71 Based Electron MonitorUnit Calculations
Abstract
Purpose: Building up a TG71 based electron monitorunit (MU) calculation protocol usually involves massive measurements. This work investigates a minimum data set of measurements and its calculation accuracy and measurement time. Methods: For 6, 9, 12, 16, and 20 MeV of our Varian ClinacSeries linear accelerators, the complete measurements were performed at different depth using 5 square applicators (6, 10, 15, 20 and 25 cm) with different cutouts (2, 3, 4, 6, 10, 15 and 20 cm up to applicator size) for 5 different SSD’s. For each energy, there were 8 PDD scans and 150 point measurements for applicator factors, cutout factors and effective SSDs that were then converted to airgap factors for SSD 99–110cm. The dependence of each dosimetric quantity on field size and SSD was examined to determine the minimum data set of measurements as a subset of the complete measurements. The “missing” data excluded in the minimum data set were approximated by linear or polynomial fitting functions based on the included data. The total measurement time and the calculated electron MU using the minimum and the complete data sets were compared. Results: The minimum data set includes 4 or 5 PDD’s and 51 to 66 point measurementsmore »
 Authors:
 University of Maryland School of Medicine, Baltimore, MD (United States)
 Publication Date:
 OSTI Identifier:
 22642326
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; APPROXIMATIONS; DEPTH; LINEAR ACCELERATORS; POLYNOMIALS; RADIATION MONITORING; RADIATION MONITORS
Citation Formats
Xu, H, Guerrero, M, Prado, K, and Yi, B. SUFT78: Minimum Data Set of Measurements for TG 71 Based Electron MonitorUnit Calculations. United States: N. p., 2016.
Web. doi:10.1118/1.4956214.
Xu, H, Guerrero, M, Prado, K, & Yi, B. SUFT78: Minimum Data Set of Measurements for TG 71 Based Electron MonitorUnit Calculations. United States. doi:10.1118/1.4956214.
Xu, H, Guerrero, M, Prado, K, and Yi, B. Wed .
"SUFT78: Minimum Data Set of Measurements for TG 71 Based Electron MonitorUnit Calculations". United States.
doi:10.1118/1.4956214.
@article{osti_22642326,
title = {SUFT78: Minimum Data Set of Measurements for TG 71 Based Electron MonitorUnit Calculations},
author = {Xu, H and Guerrero, M and Prado, K and Yi, B},
abstractNote = {Purpose: Building up a TG71 based electron monitorunit (MU) calculation protocol usually involves massive measurements. This work investigates a minimum data set of measurements and its calculation accuracy and measurement time. Methods: For 6, 9, 12, 16, and 20 MeV of our Varian ClinacSeries linear accelerators, the complete measurements were performed at different depth using 5 square applicators (6, 10, 15, 20 and 25 cm) with different cutouts (2, 3, 4, 6, 10, 15 and 20 cm up to applicator size) for 5 different SSD’s. For each energy, there were 8 PDD scans and 150 point measurements for applicator factors, cutout factors and effective SSDs that were then converted to airgap factors for SSD 99–110cm. The dependence of each dosimetric quantity on field size and SSD was examined to determine the minimum data set of measurements as a subset of the complete measurements. The “missing” data excluded in the minimum data set were approximated by linear or polynomial fitting functions based on the included data. The total measurement time and the calculated electron MU using the minimum and the complete data sets were compared. Results: The minimum data set includes 4 or 5 PDD’s and 51 to 66 point measurements for each electron energy, and more PDD’s and fewer point measurements are generally needed as energy increases. Using only <50% of complete measurement time, the minimum data set generates acceptable MU calculation results compared to those with the complete data set. The PDD difference is within 1 mm and the calculated MU difference is less than 1.5%. Conclusion: Data set measurement for TG71 electron MU calculations can be minimized based on the knowledge of how each dosimetric quantity depends on various setup parameters. The suggested minimum data set allows acceptable MU calculation accuracy and shortens measurement time by a few hours.},
doi = {10.1118/1.4956214},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}

Purpose: Monitor units calculated by electron Monte Carlo treatment planning systems are often higher than TG71 hand calculations for a majority of patients. Here I’ve calculated tables of geometry and heterogeneity correction factors for correcting electron hand calculations. Method: A flat water phantom with spherical volumes having radii ranging from 3 to 15 cm was created. The spheres were centered with respect to the flat water phantom, and all shapes shared a surface at 100 cm SSD. D{sub max} dose at 100 cm SSD was calculated for each cone and energy on the flat phantom and for the spherical volumesmore »

SUFT54: Determination of the AAPM TG43 Brachytherapy Dosimetry Parameters for A New TitaniumEncapsulated Yb169 Source by Monte Carlo Calculations
Purpose: To determine the AAPM TG43 brachytherapy dosimetry parameters of a new titaniumencapsulated Yb169 source designed to maximize the dose enhancement during gold nanoparticleaided radiation therapy (GNRT). Methods: An existing Monte Carlo (MC) model of the titaniumencapsulated Yb169 source, which was described in the current investigators’ published MC optimization study, was modified based on the source manufacturer’s detailed specifications, resulting in an accurate model of the titaniumencapsulated Yb169 source that was actually manufactured. MC calculations were then performed using the MCNP5 code system and the modified source model, in order to obtain a complete set of the AAPM TG43 parametersmore » 
SUFT248: FMEA Risk Analysis Implementation (AAPM TG100) in Total Skin Electron Irradiation Technique
Purpose: Total Skin Electron Irradiation (TSEI) is a radiotherapy treatment which involves irradiating the entire body surface as homogeneously as possible. It is composed of an extensive multistep technique in which quality management requires high consumption of resources and a fluid communication between the involved staff, necessary to improve the safety of treatment. The TG100 proposes a new perspective of quality management in radiotherapy, presenting a systematic method of risk analysis throughout the global flow of the stages through the patient. The purpose of this work has been to apply TG100 approach to the TSEI procedure in our institution. Methods:more » 
SUFT458: Tracking Trends of TG142 Parameters Via Analysis of Data Recorded by 2D Chamber Array
Purpose: With increasing QA demands of medical physicists in clinical radiation oncology, the need for an effective method of tracking clinical data has become paramount. A tool was produced which scans through data automatically recorded by a 2D chamber array and extracts relevant information recommended by TG142. Using this extracted information a timely and comprehensive analysis of QA parameters can be easily performed enabling efficient monthly checks on multiple linear accelerators simultaneously. Methods: A PTW STARCHECK chamber array was used to record several months of beam outputs from two Varian 2100 series linear accelerators and a Varian NovalisTx−. In conjunctionmore » 
SUET552: Minimum Monitor Unit Effects On Plan Quality for MultiField Optimized Spot Scanning Proton Therapy
Purpose: To investigate the influence of the minimum monitor unit (MU) on the quality of clinical treatment plans for scanned proton therapy. Methods: Delivery system characteristics limit the minimum number of protons that can be delivered per spot, resulting in a minMU limit. Plan quality can be impacted by the minMU limit. Two sites were used to investigate the impact of minMU on treatment plans: pediatric brain tumor at a depth of 510 cm; a head and neck tumor at a depth of 120 cm. Three field intensity modulated spot scanning proton plans were created for each site with themore »