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Title: SU-E-T-575: Novel Quality Assurance Procedure for the Small Animal Radiation Research Platform Using Commercial OSLDs

Abstract

Purpose: To support radiobiological research with the Xstrahl small animal radiation research platform (SARRP) by developing a simple and effective method using commercially available optically stimulated luminescent dosimeters (OSLDs) that ensures dose output consistency. Methods: The SARRP output is calibrated according to the vendor standards and TG-61 protocol utilizing an ADCL calibrated ion chamber and electrometer at 2 cm depth of solid water. A cross calibration is performed by replacing the ion chamber with five OSLDs at the 2 cm depth. The OSLDs are irradiated to 500 cGy with 220 keV at 13 mA (78s delivery time) with a copper filter for an uncollimated 17×17 cm{sup 2} aperture. Instead of the absolute dose, the total amount of raw counts are collected from the OSLD reader and used for analysis. This constancy procedure was performed two more times over the course of three weeks with two OLSDs for validity. Results: The average reading for all OSLDs is 494939 with a 1-sigma standard deviation of the 5.8%. With an acceptable dose output range of ±10%, the OSLD readings have a counts range of [445445, 544433]. Conclusion: This method of using nanoDot™ OSLDs to perform output constancy checks for the SARRP ensures themore » output of the device is within 10% from the time of calibration and is convenient as well as time efficient. Because this, the frequency of output checks can be increased, which can improve the output stability for research with this device. The output trend of the SARRP will continue to be monitored in the future to establish a timeline for constancy checks and recalibration.« less

Authors:
; ;  [1];  [2]
  1. Thomas Jefferson University, Philadelphia, PA (United States)
  2. Xstrahl Inc., Suwanee, GA (United States)
Publication Date:
OSTI Identifier:
22496289
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 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; 60 APPLIED LIFE SCIENCES; 62 RADIOLOGY AND NUCLEAR MEDICINE; ANIMALS; DOSEMETERS; DOSIMETRY; IONIZATION CHAMBERS; KEV RANGE 100-1000; QUALITY ASSURANCE; RADIATION DOSES; RADIOBIOLOGY

Citation Formats

Keller, J, Lockamy, V, Harrison, A, and Glenn, S. SU-E-T-575: Novel Quality Assurance Procedure for the Small Animal Radiation Research Platform Using Commercial OSLDs. United States: N. p., 2015. Web. doi:10.1118/1.4924937.
Keller, J, Lockamy, V, Harrison, A, & Glenn, S. SU-E-T-575: Novel Quality Assurance Procedure for the Small Animal Radiation Research Platform Using Commercial OSLDs. United States. doi:10.1118/1.4924937.
Keller, J, Lockamy, V, Harrison, A, and Glenn, S. Mon . "SU-E-T-575: Novel Quality Assurance Procedure for the Small Animal Radiation Research Platform Using Commercial OSLDs". United States. doi:10.1118/1.4924937.
@article{osti_22496289,
title = {SU-E-T-575: Novel Quality Assurance Procedure for the Small Animal Radiation Research Platform Using Commercial OSLDs},
author = {Keller, J and Lockamy, V and Harrison, A and Glenn, S},
abstractNote = {Purpose: To support radiobiological research with the Xstrahl small animal radiation research platform (SARRP) by developing a simple and effective method using commercially available optically stimulated luminescent dosimeters (OSLDs) that ensures dose output consistency. Methods: The SARRP output is calibrated according to the vendor standards and TG-61 protocol utilizing an ADCL calibrated ion chamber and electrometer at 2 cm depth of solid water. A cross calibration is performed by replacing the ion chamber with five OSLDs at the 2 cm depth. The OSLDs are irradiated to 500 cGy with 220 keV at 13 mA (78s delivery time) with a copper filter for an uncollimated 17×17 cm{sup 2} aperture. Instead of the absolute dose, the total amount of raw counts are collected from the OSLD reader and used for analysis. This constancy procedure was performed two more times over the course of three weeks with two OLSDs for validity. Results: The average reading for all OSLDs is 494939 with a 1-sigma standard deviation of the 5.8%. With an acceptable dose output range of ±10%, the OSLD readings have a counts range of [445445, 544433]. Conclusion: This method of using nanoDot™ OSLDs to perform output constancy checks for the SARRP ensures the output of the device is within 10% from the time of calibration and is convenient as well as time efficient. Because this, the frequency of output checks can be increased, which can improve the output stability for research with this device. The output trend of the SARRP will continue to be monitored in the future to establish a timeline for constancy checks and recalibration.},
doi = {10.1118/1.4924937},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • Purpose: Use of Small Animal Radiation Research Platform (SARRP) systems for conducting state-of-the-art image guided radiotherapy (IGRT) research on small animals has become more common over the past years. The purpose of this work is to develop and test the suitability and performance of a comprehensive quality assurance (QA) phantom for the SARRP. Methods: A QA phantom was developed for carrying out daily, monthly and annual QA tasks including imaging, dosimetry and treatment planning system (TPS) performance evaluation of the SARRP. The QA phantom consists of nine (60×60×5 mm3) KV-energy tissue equivalent solid water slabs that can be employed formore » annual dosimetry QA with film. Three of the top slabs are replaceable with ones incorporating Mosfets or OSLDs arranged in a quincunx pattern, or a slab drilled to accommodate an ion chamber insert. These top slabs are designed to facilitate routine daily and monthly QA tasks such as output constancy, isocenter congruency test, treatment planning system (TPS) QA, etc. One slab is designed with inserts for image QA. A prototype of the phantom was applied to test the performance of the imaging, planning and treatment delivery systems. Results: Output constancy test results showed daily variations within 3%. For isocenter congruency test, the phantom could be used to detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Using the Mosfet in phantom as target, the difference between TPS calculations and measurements was within 5%. Image-quality parameters could also be assessed in terms of geometric accuracy, CT number accuracy, linearity, noise and image uniformity, etc. Conclusion: The developed phantom can be employed as a simple tool for comprehensive performance evaluation of the SARRP. The study provides a reference for development of a comprehensive quality assurance program for the SARRP, with proposed tolerances and frequency of required tests.« less
  • Purpose: Three dimensional (3D) Grid Therapy using MLC-based inverse-planning has been proposed to achieve the features of both conformal radiotherapy and spatially fractionated radiotherapy, which may deliver very high dose in a single fraction to portions of a large tumor with relatively low normal tissue dose. However, the technique requires relatively long delivery time. This study aims to develop a collimator-based 3D grid therapy technique. Here we report the development of the technique in a small animal radiation research platform. Methods: Similar as in the MLC-based technique, 9 non-coplanar beams in special channeling directions were used for the 3D gridmore » therapy technique. Two specially designed grid collimators were fabricated, and one of them was selectively used to match the corresponding gantry/couch angles so that the grid opening of all 9 beams are met in the 3D space in the target. A stack of EBT3 films were used as 3D dosimetry to demonstrate the 3D grid-like dose distribution in the target. Three 1-mm beams were delivered to the stack of films in the area outside the target for alignment when all the films were scanned to reconstruct the 3D dosimtric image. Results: 3D film dosimetry showed a lattice-like dose distribution in the 3D target as well as in the axial, sagittal and coronal planes. The dose outside the target also showed a grid like dose distribution, and the average dose gradually decreased with the distance to the target. The peak to valley ratio was approximately 5:1. The delivery time was 7 minutes for 18 Gy peak dose, comparing to 6 minutes to deliver a 18-Gy 3D conformal plan. Conclusion: We have demonstrated the feasibility of the collimator-based 3D grid therapy technique which can significantly reduce delivery time comparing to MLC-based inverse planning technique.« less
  • Purpose: To study the suitability of a novel 1D silicon monolithic array for dosimetry of small radiation fields and for QA of high dose gradient treatment modalities (IMRT and SBRT). Methods: A 1D array composed of 4 monolithic silicon modules of 64 mm length and 1 mm pixel pitch was developed by IBA Dosimetry. Measurements were carried out for 6MV and 15MV photons on two commercial different linacs (TrueBeam and Clinac iX, Varian Medical Systems, Palo Alto, CA) and for a CyberKnife G4 (Accuray Inc., Sunnyvale, CA). The 1D array was used to measure output factors (OF), profiles and offmore » axis correction factors (OACF) for the Iris CyberKnife variable collimator (5–60 mm). In addition, dose profiles (at the isocenter plane) were measured for multiple IMRT and SBRT treatment plans and compared with those obtained using EDR2radiographic film (Carestream Health, Rochester NY), a commercial 2D diode array and with the dose distribution calculated using a commercial TPS (Eclipse, Varian Medical Systems, Palo Alto, CA). Results: Due to the small pixel pitch of the detector, IMRT and SBRT plan profiles deviate from film measurements by less than 2%. Similarly, the 1D array exhibits better performance than the 2D diode array due to the larger (7 mm) pitch of that device. Iris collimator OFs measured using the 1D silicon array are in good agreement with the commissioning values obtained using a commercial stereotactic diode as well as with published data. Maximum deviations are < 3% for the smallest field (5 and 7.5mm) and below 1% for all other dimensions. Conclusion: We have demonstrated good performances of the array for commissioning of small photon fields and in patient QA, compared with diodes and film typically used in these clinical applications. The technology compares favorably with existing commercial solutions The presenting author is founded by a Marie Curie Early Initial Training Network Fellowship of the European Communitys Seventh Framework Programme under contract number (PITN-GA-2011-289198-ARDENT). The research activity is hosted by IBA Dosimetry, Gmbh.« less
  • Purpose: A successful VMAT plan delivery includes precise modulations of dose rate, gantry rotational and multi-leaf collimator shapes. The purpose of this research is to construct routine QA protocol which focuses on VMAT delivery technique and to obtain a baseline including dose error, fluence distribution and mechanical accuracy during VMAT. Methods: The mock prostate, head and neck (HN) cases supplied from AAPM were used in this study. A VMAT plans were generated in Monaco TPS according to TG-119 protocol. Plans were created using 6 MV and 10 MV photon beams for each case. The phantom based measurement, fluence measurement andmore » log files analysis were performed. The dose measurement was performed using 0.6 cc ion chamber, which located at isocenter. The fluence distribution were acquired using the MapCHECK2 mounted in the MapPHAN. The trajectory log files recorded inner 20 leaf pairs and gantry angle positions at every 0.25 sec interval were exported to in-house software developed by MATLAB and determined those RMS values. Results: The dose difference is expressed as a ratio of the difference between measured and planned doses. The dose difference for 6 MV was 0.91%, for 10 MV was 0.67%. In turn, the fluence distribution using gamma criteria of 2%/2 mm with a 50% minimum dose threshold for 6 MV was 98.8%, for 10 MV was 97.5%, respectively. The RMS values of MLC for 6 MV and 10 MV were 0.32 mm and 0.37 mm, of gantry were 0.33 degree and 0.31 degree. Conclusion: In this study, QA protocol to assess VMAT delivery accuracy is constructed and results acquired in this study are used as a baseline of VMAT delivery performance verification.« less
  • Purpose: To test the accuracy and reproducibility of both translational and rotational movements for a couch with six degrees of freedom (6DoF) using a novel phantom design Methods: An end-to-end test was carried out using two different phantoms. A 6 cm3 cube with a central fiducial BB (WL-QA Sun Nuclear) and a custom fabricated rectangular prism (31 cm x 8 cm x 8 cm), placed on a baseplate with known angular offsets for pitch, roll and yaw with a central fiducial BB and unique surface structures for registration purposes, were used. The end-to-end test included an initial CT simulation formore » a reference study, setup to an offset mark on each phantom, registration of the reference CT to the acquired cone-beam CT, and final Winston-Lutz delivery at four cardinal gantry angles. Results for both translational and rotational movements were recorded and compared for both phantoms. Results: Translational and rotational measurements were performed with a PerfectPitch (Varian) couch for 10 trials for both phantoms. Distinct translational shifts were [−5.372±0.384mm, −10.183±0.137mm, 14.028±0.155mm] for the cube and [7.520±0.159mm, −9.117±0.101mm, 16.273±0.115mm] for the prototype phantom for lateral, longitudinal, and vertical shifts, respectively. Distinct rotational adjustments were [1.121±0.102o, −1.067±0.235o, −2.662±0.380o] for the cube and [2.534±0.059o, 1.994±0.025o, 2.094±0.076o] for the prototype for pitch, roll, and yaw, respectively. Winston-Lutz test results performed after 6DoF couch correction from each cardinal gantry angle ranged from 0.26–0.72mm for the cube and 0.55–0.86mm for the prototype. Conclusion: The prototype phantom is more precise for both translational and rotational adjustments compared to a commercial phantom. The design of the prototype phantom allows for a more discernible visual confirmation of correct translational and rotational adjustments with the prototype phantom. Winston-Lutz results are more accurate for the commercial phantom but are still within tolerance for the prototype phantom.« less