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Title: WE-AB-BRB-00: Session in Memory of Robert J. Shalek: High Resolution Dosimetry from 2D to 3D to Real-Time 3D

Abstract

Despite widespread IMRT treatments at modern radiation therapy clinics, precise dosimetric commissioning of an IMRT system remains a challenge. In the most recent report from the Radiological Physics Center (RPC), nearly 20% of institutions failed an end-to-end test with an anthropomorphic head and neck phantom, a test that has rather lenient dose difference and distance-to-agreement criteria of 7% and 4 mm. The RPC report provides strong evidence that IMRT implementation is prone to error and that improved quality assurance tools are required. At the heart of radiation therapy dosimetry is the multidimensional dosimeter. However, due to the limited availability of water-equivalent dosimetry materials, research and development in this important field is challenging. In this session, we will review a few dosimeter developments that are either in the laboratory phase or in the pre-commercialization phase. 1) Radiochromic plastic. Novel formulations exhibit light absorbing optical contrast with very little scatter, enabling faster, broad beam optical CT design. 2) Storage phosphor. After irradiation, the dosimetry panels will be read out using a dedicated 2D scanning apparatus in a non-invasive, electro-optic manner and immediately restored for further use. 3) Liquid scintillator. Scintillators convert the energy from x-rays and proton beams into visible light, whichmore » can be recorded with a scientific camera (CCD or CMOS) from multiple angles. The 3D shape of the dose distribution can then be reconstructed. 4) Cherenkov emission imaging. Gated intensified imaging allows video-rate passive detection of Cherenkov emission during radiation therapy with the room lights on. Learning Objectives: To understand the physics of a variety of dosimetry techniques based upon optical imaging To investigate the strategies to overcome respective challenges and limitations To explore novel ideas of dosimeter design Supported in part by NIH Grants R01CA148853, R01CA182450, R01CA109558. Brian Pogue is founder and president of the company DoseOptics LLC, dedicated to developing and commercializing the first dedicated Cerenkov imaging camera and system for radiation dose imaging. Work reported in this talk does not involve the use of DoseOptics technology.; H. Li, this work was supported in part by NIH Grant No. R01CA148853; S. Beddar, NIH funding R01-CA182450.« less

Publication Date:
OSTI Identifier:
22654089
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:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BIOMEDICAL RADIOGRAPHY; DOSEMETERS; DOSIMETRY; OPTICS; PROTON BEAMS; QUALITY ASSURANCE; RADIATION DOSE DISTRIBUTIONS; RADIOTHERAPY; VISIBLE RADIATION; X RADIATION

Citation Formats

NONE. WE-AB-BRB-00: Session in Memory of Robert J. Shalek: High Resolution Dosimetry from 2D to 3D to Real-Time 3D. United States: N. p., 2016. Web. doi:10.1118/1.4957725.
NONE. WE-AB-BRB-00: Session in Memory of Robert J. Shalek: High Resolution Dosimetry from 2D to 3D to Real-Time 3D. United States. doi:10.1118/1.4957725.
NONE. 2016. "WE-AB-BRB-00: Session in Memory of Robert J. Shalek: High Resolution Dosimetry from 2D to 3D to Real-Time 3D". United States. doi:10.1118/1.4957725.
@article{osti_22654089,
title = {WE-AB-BRB-00: Session in Memory of Robert J. Shalek: High Resolution Dosimetry from 2D to 3D to Real-Time 3D},
author = {NONE},
abstractNote = {Despite widespread IMRT treatments at modern radiation therapy clinics, precise dosimetric commissioning of an IMRT system remains a challenge. In the most recent report from the Radiological Physics Center (RPC), nearly 20% of institutions failed an end-to-end test with an anthropomorphic head and neck phantom, a test that has rather lenient dose difference and distance-to-agreement criteria of 7% and 4 mm. The RPC report provides strong evidence that IMRT implementation is prone to error and that improved quality assurance tools are required. At the heart of radiation therapy dosimetry is the multidimensional dosimeter. However, due to the limited availability of water-equivalent dosimetry materials, research and development in this important field is challenging. In this session, we will review a few dosimeter developments that are either in the laboratory phase or in the pre-commercialization phase. 1) Radiochromic plastic. Novel formulations exhibit light absorbing optical contrast with very little scatter, enabling faster, broad beam optical CT design. 2) Storage phosphor. After irradiation, the dosimetry panels will be read out using a dedicated 2D scanning apparatus in a non-invasive, electro-optic manner and immediately restored for further use. 3) Liquid scintillator. Scintillators convert the energy from x-rays and proton beams into visible light, which can be recorded with a scientific camera (CCD or CMOS) from multiple angles. The 3D shape of the dose distribution can then be reconstructed. 4) Cherenkov emission imaging. Gated intensified imaging allows video-rate passive detection of Cherenkov emission during radiation therapy with the room lights on. Learning Objectives: To understand the physics of a variety of dosimetry techniques based upon optical imaging To investigate the strategies to overcome respective challenges and limitations To explore novel ideas of dosimeter design Supported in part by NIH Grants R01CA148853, R01CA182450, R01CA109558. Brian Pogue is founder and president of the company DoseOptics LLC, dedicated to developing and commercializing the first dedicated Cerenkov imaging camera and system for radiation dose imaging. Work reported in this talk does not involve the use of DoseOptics technology.; H. Li, this work was supported in part by NIH Grant No. R01CA148853; S. Beddar, NIH funding R01-CA182450.},
doi = {10.1118/1.4957725},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: The authors evaluate the capability of a beryllium oxide (BeO) ceramic fiber-coupled luminescence dosimeter, named radioluminescence/optically stimulated luminescence (RL/OSL) BeO FOD, for dosimetric verification of high dose rate (HDR) treatments. The RL/OSL BeO FOD is capable of RL and OSL measurements. Methods: The RL/OSL BeO FOD is able to be inserted in 6F proguide needles, used in interstitial HDR treatments. Using a custom built Perspex phantom, 6F proguide needles could be submerged in a water tank at 1 cm separations from each other. A second background fiber was required to correct for the stem effect. The stem effect, dosemore » linearity, reproducibility, depth-dose curves, and angular and temperature dependency of the RL/OSL BeO FOD were characterised using an Ir-192 source. The RL/OSL BeO FOD was also applied to the commissioning of a 10 mm horizontal Leipzig applicator. Results: Both the RL and OSL were found to be reproducible and their percentage depth-dose curves to be in good agreement with those predicted via TG-43. A combined uncertainty of 7.9% and 10.1% (k = 1) was estimated for the RL and OSL, respectively. For the 10 mm horizontal Leipzig applicator, measured percentage depth doses were within 5% agreement of the published reference calculations. The output at the 3 mm prescription depth for a 1 Gy delivery was verified to be 0.99 ± 0.08 Gy and 1.01 ± 0.10 Gy by the RL and OSL, respectively. Conclusions: The use of the second background fiber under the current setup means that the two fibers cannot fit into a single 6F needle. Hence, use of the RL is currently not adequate for the purpose of in vivo brachytherapy dosimetry. While not real-time, the OSL is shown to be adequate for in vivo brachytherapy dosimetry.« less
  • Real time spectroscopic ellipsometry (RTSE) has been applied to characterize compositionally graded amorphous silicon-carbon alloy (a-Si{sub 1{minus}x}C{sub x}:H) thin films, prepared using continuous variations in the flow ratio z=[CH{sub 4}]/{l_brace}[SiH{sub 4}]+[CH{sub 4}]{r_brace} during rf plasma-enhanced chemical vapor deposition. Triangular variations in z versus time, yielding 50{endash}130-{Angstrom}-thick a-Si{sub 1{minus}x}C{sub x}:H graded layers with 0.02{le}x{le}0.24, were applied in order to assess the performance of the RTSE data analysis procedure. This procedure employs a four-medium virtual interface approximation, and returns the time evolution of (i) the near-surface C content, (ii) the instantaneous growth rate, and (iii) the surface roughness layer thickness. In themore » depth profiles of the graded structures, an apparent resolution of {approximately}10 {Angstrom} is obtained with a composition uncertainty of {plus_minus}0.004. {copyright} {ital 1997 American Institute of Physics.}« less
  • This study details the differences in real-time hydration between pure tricalcium aluminate (cubic C{sub 3}A or 3CaO {center_dot} Al{sub 2}O{sub 3}) and Na-doped tricalcium aluminate (orthorhombic C{sub 3}A or Na{sub 2}Ca{sub 8}Al{sub 6}O{sub 18}), in aqueous solutions containing sulfate ions. Pure phases were synthesized in the laboratory to develop an independent benchmark for the reactions, meaning that their reactions during hydration in a simulated early age cement pore solution (saturated with respect to gypsum and lime) were able to be isolated. Because the rate of this reaction is extremely rapid, most microscopy methods are not adequate to study the earlymore » phases of the reactions in the early stages. Here, a high-resolution full-field soft X-ray imaging technique operating in the X-ray water window, combined with solution analysis by {sup 27}Al nuclear magnetic resonance (NMR) spectroscopy, was used to capture information regarding the mechanism of C{sub 3}A hydration during the early stages. There are differences in the hydration mechanism between the two types of C{sub 3}A, which are also dependent on the concentration of sulfate ions in the solution. The reactions with cubic C{sub 3}A (pure) seem to be more influenced by higher concentrations of sulfate ions, forming smaller ettringite needles at a slower pace than the orthorhombic C{sub 3}A (Na-doped) sample. The rate of release of aluminate species into the solution phase is also accelerated by Na doping.« less
  • Localization of an undescended testis was attempted in 23 instances in 20 patients using both computed tomography (CT) and high-resolution real-time ultrasonography. The testis was identified and correctly localized 16 times by CT and 15 times by ultrasound. There was one false-negative diagnosis by CT and two by ultrasound. False-positive diagnoses were not made with either modality in the six cases in which the testis was not found during exploratory surgery. CT showed 94% sensitivity, 100% specificity, and 96% accuracy; ultrasound resulted in 88% sensitivity, 100% specificity, and 91% accuracy. The authors recommend high-resolution real-time ultrasound as the modality ofmore » choice for this procedure because it is simple, accurate, and avoids the use of ionizing radiation. CT may be used when ultrasound findings are negative or equivocal. Angiography should rarely be required.« less