Dosimetry Systems for Use in Radiation Processing:

Chu, R. D. H.; McLaughlin, W.L.; Miller, Albert J.; Sharpe, Peter

doi:10.1093/jicru/ndn032

Cited by 5 publications

(6 citation statements)

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“…The selection of suitable dosimetry systems that was used for the assessment, was made on the basis of international recommendations, reviews and standards elaborated for high dose rate field radiation processing facilities. [40][41][42] Alanine, [41] Fricke [43] and ceric−cerous [44] dosimeters are classified as reference-standard dosimeters (type I), in contrast to Perspex dosimeters which are classified as routine (type II) dosimeters. [41] The advantage of type I dosimeters is that they are of high metrological quality: different quantifiable influences are very well identified and can be compensated by using correction factors.…”

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confidence: 99%

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

et al. 2020

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The recycling of minor actinides from dissolved nuclear fuels by hydrometallurgical separation is one challenging strategy for the management of spent fuel. These future separation processes will likely be based on solvent extraction processes in which an organic solvent system (extractant and diluent) will be contacted with highly radioactive aqueous solutions. To establish a separation between different elements in spent nuclear fuel, many extractants have been studied in the past. A particular example is N,N,N′,N′-tetraoctyl diglycolamide (TODGA), which co-extracts lanthanides and actinides from nitric acid solutions into an organic phase (e.g. TODGA in n-dodecane). The radiolytic stability of these extractants is crucial, since they will absorb high doses of ionizing radiation during their usage. Worldwide, different gamma irradiation facilities are employed to expose extractants to ionizing radiation and gain insight in their radiation stability. The facilities differ in many ways, such as their environment (pool-type or dry), configuration and gamma sources (often 60Co or spent nuclear fuel). In this paper, a dosimetric assessment is made using different dosimeter systems in a pool-type irradiation facility, which has the advantage to be flexible in its arrangement of 60Co sources. It is shown that Red Perspex dosimeters can be used to accurately characterize this high dose rate gamma irradiation field (approx. 13.6 kGy h−1), after comparison with alanine, Fricke and ceric-cerous dosimetry in a lower dose rate gamma irradiation field (approx. 0.5 kGy h−1). A final validation of the whole chain of techniques is obtained by reproduction of the dose constants for TODGA in n-dodecane.

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confidence: 99%

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

et al. 2020

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“…Small‐field dosimetry, known to be challenging due to volume averaging effects and a lack of charged particle equilibrium (CPE), has been extensively discussed in the literature 6, 7. The problems associated with small‐field dosimetry for flattened beams are likely to be compounded in flattening filter free (FFF) beams, given their inherently higher dose gradients, not just the penumbral region but also in the central beam, and higher doses per pulse 8, 9…”

Section: Introductionmentioning

confidence: 99%

“…These would ideally have a small water‐equivalent sensitive volume (SV), allowing for high positioning accuracy, and show negligible energy, dose rate, and directional dependence 12. Although commercially available detectors do not satisfy all of the above criteria, it has been common practice to perform measurements with at least two types of dosimeters to cross‐check the consistency of results,13 as recently recommended by an ICRU report 6…”

Section: Introductionmentioning

confidence: 99%

“…Solid‐state detectors thus have the potential to offer comparable performance to Gafchromic film, though with a real‐time read‐out. Their use is recommended by a recent IAEA‐AAPM dosimetry protocol,7 but only single detectors used with various scanning techniques have been shown to offer submillimeter spatial resolution 6. When used for small‐field dosimetry, correction factors need to be applied to account for beam perturbations, due to their SVs and extracameral components.…”

Section: Introductionmentioning

confidence: 99%

“…When used for small‐field dosimetry, correction factors need to be applied to account for beam perturbations, due to their SVs and extracameral components. These factors depend on detector design, treatment head design, beam quality, field size, and measurement conditions 6. Monte Carlo (MC) codes are commonly used for modeling linac beam lines, and have been shown to be an effective tool in characterizing detector response in small radiation fields and their required correction factors 16.…”

Section: Introductionmentioning

confidence: 99%

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CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

Biasi

Petasecca

Guatelli

et al. 2018

J Applied Clin Med Phys

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PurposeThe challenges of accurate dosimetry for stereotactic radiotherapy (SRT) with small unflattened radiation fields have been widely reported in the literature. In this case, suitable dosimeters would have to offer a submillimeter spatial resolution. The CyberKnife® (Accuray Inc., Sunnyvale, CA, USA) is an SRT‐dedicated linear accelerator (linac), which can deliver treatments with submillimeter positional accuracy using circular fields. Beams are delivered with the desired field size using fixed cones, the InCise™ multileaf collimator or a dynamic variable‐aperture Iris™ collimator. The latter, allowing for field sizes to be varied during treatment delivery, has the potential to decrease treatment time, but its reproducibility in terms of output factors (OFs) and dose profiles (DPs) needs to be verified.MethodsA 2D monolithic silicon array detector, the “Octa”, was evaluated for dosimetric quality assurance (QA) for a CyberKnife system. OFs, DPs, percentage depth‐dose (PDD) and tissue maximum ratio (TMR) were investigated, and results were benchmarked against the PTW SRS diode. Cross‐plane, in‐plane and 2 diagonal dose profiles were measured simultaneously with high spatial resolution (0.3 mm). Monte Carlo (MC) simulations with a GEANT4 (GEometry ANd Tracking 4) tool‐kit were added to the study to support the experimental characterization of the detector response.ResultsFor fixed cones and the Iris, for all field sizes investigated in the range between 5 and 60 mm diameter, OFs, PDDs, TMRs, and DPs in terms of FWHM measured by the Octa were accurate within 3% when benchmarked against the SRS diode and MC calculations.ConclusionsThe Octa was shown to be an accurate dosimeter for measurements with a 6 MV FFF beam delivered with a CyberKnife system. The detector enabled real‐time dosimetric verification for the variable aperture Iris collimator, yielding OFs and DPs consistent with those obtained with alternative methods.

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Assessment of dose‐volume histogram precision for five clinical systems

et al. 2022

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To investigate the dependency of dose-volume histogram (DVH) behavior and precision on underlying discretization using shapes and dose distributions with known analytical DVHs for five commercial DVH calculators. Methods: DVHs and summary metrics were extracted from all five systems using synthetic cone and cylinder objects for which the true volume and DVH curves were known. Trends in the curves and metrics were explored by varying the underlying voxelization of the CT image, structure set, and dose grid as well by varying the geometry of the structure and direction of a linear dose gradient. Using synthetic structures allowed for comparison with ground truth DVH curves to assess their accuracy while an algorithm was additionally developed to assess the precision of each system. The precision was calculated with a novel algorithm that treats any "stair step" behavior in a DVH curve as an uncertainty band and calculates the width, characterized as a percent difference, of the band for various DVH metrics. The underlying voxelization was additionally changed and DVHs were extracted for two clinical examples. The details of how each system calculated DVHs were also investigated and tendencies in the calculated curves, metrics, and precision were related to choices made in the calculation methodology. Results: Calculation methodology differences that had a noticeable impact on the DVH curves and summary metrics include supersampling beyond the input grids and interpretation of the superior and inferior ends of the structures. Among the systems studied, the median precision ranged from 0.902% to 3.22%, and interquartile ranges varied from 1.09% to 3.91%. Conclusions: Commercial dose-evaluation solutions can calculate different DVH curves, structure volume measures, and dose statistics for the same input data due to differences in their calculation methodologies. This study highlights the importance of understanding and investigating the DVH calculation when considering a new clinical system and when using more than one system for data transfer. K E Y W O R D S dose-volume histogram, DVH analysis, treatment planning systems

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Dosimetry Systems for Use in Radiation Processing:

Cited by 5 publications

References 0 publications

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

Assessment of dose‐volume histogram precision for five clinical systems

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Dosimetry Systems for Use in Radiation Processing:

Cited by 5 publications

References 0 publications

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

Dosimetry and methodology of gamma irradiation for degradation studies on solvent extraction systems

CyberKnife® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array

Assessment of dose‐volume histogram precision for five clinical systems

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CyberKnife^® fixed cone and Iris™ defined small radiation fields: Assessment with a high‐resolution solid‐state detector array