Evaluation of the PTW microDiamond in edge‐on orientation for dosimetry in small fields

Brace, Owen J.; Alhujaili, S.; Paino, Jason; Butler, Duncan; Wilkinson, Dean; Oborn, Bradley M; Rosenfeld, Anatoly B.; Lerch, Michael L. F; Petasecca, Marco; Davis, Joel

doi:10.1002/acm2.12906

Cited by 21 publications

(22 citation statements)

References 34 publications

(38 reference statements)

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“…The non-coplanar angular dependence of the diamond detector was found to be within 5% for a range of clinically deliverable gantry and couch angles. These results agree with studies performed by Brace et al [18] and Veselsky et al [25] who found similar angular dependencies for gantry angles up to 70 • , but very large angular dependencies of up to 30% when irradiating through the stem of the detector. These beam angles would not be clinically deliverable in SRS treatment plans delivered on a conventional linac, and have therefore not been considered by in this study.…”

Section: Discussionsupporting

confidence: 93%

“…For SRS and SBRT this concept is extended, as the treatment delivery may involve non-coplanar couch and gantry angles. Angular dependence of the diamond detectors in a perpendicular orientation has been investigated, however angular correction factors have not been presented [18]. In addition, direct dose measurements are not typically reported.…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Shaw¹,

Lye²,

Alves³

et al. 2021

Physics and Imaging in Radiation Oncology

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Background and purpose: Synthetic diamond detectors offer real time measurement of dose in radiotherapy applications which require high spatial resolution. Additional considerations and corrections are required for measurements where the diamond detector is orientated at various angles to the incident beam. This study investigated diamond detectors for end-to-end testing of Stereotactic Body Radiotherapy (SBRT) and Stereotactic Radiosurgery (SRS) in the context of dosimetry audits. Material and methods: Seven individual diamond detectors were investigated and compared with respect to warm up stability, dose-rate dependence, linearity, detector shadowing, energy response, cross-calibration, angular dependence and positional sensitivity in SBRT and SRS. Results: Large variation in the cross calibration factors was found between the seven individual detectors. For each detector, the energy dependence in the cross calibration factor was on average <0.6% across the beam qualities investigated (Co-60 Gamma Knife, and MV beams with TPR 20,10 0.684-0.733). The angular corrections for individual fields were up to 5%, and varied with field size. However, the average angular dependence for all fields in a typical SRS treatment delivery was <1%. The overall measurement uncertainty was 3.6% and 3.1% (2σ) for an SRS and SBRT treatment plan respectively. Conclusion: Synthetic diamond detectors were found to be reliable and robust for end-to-end dosimetry in SBRT and SRS applications. Orientation of the detector relative to the beam axis is an important consideration, as significant corrections are required for angular dependence.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Shaw¹,

Lye²,

Alves³

et al. 2021

Physics and Imaging in Radiation Oncology

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“…PDDs were acquired using a PTW (Freiburg, Germany) Semiflex 3D ionization chamber for fields ≥ 4 cm 2 and a PTW microdiamond 19 in the edge‐on orientation 20 for fields <4 cm 2 in a PTW Beamscan water tank under the following field sizes: 1 × 1, 2 × 2, 4 × 4, 10 × 10, and 28 × 28 cm 2 . Profiles were acquired using the same detector and water tank, but only under field sizes of 4 × 4, 10 × 10 and 28 × 28 cm 2 and depths of 1.3 cm (D max ), 10.0 and 20.0 cm.…”

Section: Methodsmentioning

confidence: 99%

“…PDDs were acquired using a PTW (Freiburg, Germany) Semiflex 3D ionization chamber for fields ≥ 4 cm 2 and a PTW microdiamond 19 in the edge-on orientation 20 and a microdiamond in the edge-on orientation for fields < 4 cm 2 , with the detector sitting at 10 cm depth and 90 cm SSD in a water tank. Readings were referenced back to that of 10 × 10 cm 2 through daisy-chaining 21 to calculate output factors.…”

Section: A1 | Pdds and Profiles Of Standard Square Fieldsmentioning

confidence: 99%

Validation of the preconfigured Varian Ethos Acuros XB Beam Model for treatment planning dose calculations: A dosimetric study

Byrne

Archibald-Heeren

et al. 2020

J Applied Clin Med Phys

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Varian (Palo Alto, California, United States) recently released an online adaptation treatment platform, Ethos, which has introduced a new Dose Preview and Automated Plan Generation module despite sharing identical beam data with the existing Halcyon linac. The module incorporates a preconfigured beam model and the Acuros XB algorithm (Ethos AXB model) to generate final dose calculations from an initial fluence optimization. In this study, we comprehensively validated the accuracy of the Ethos AXB model by comparing it against the Halcyon AXB model, the Halcyon Anisotropic Analytical Algorithm (AAA) model, and measurements acquired on an Ethos linac. Results indicated that the Ethos AXB model demonstrated a comparable if not superior dosimetric accuracy to the Halcyon AXB model in basic and complex calculations, and at the same time its dosimetric accuracy in modulated and heterogeneous plans was better than that of the Halcyon AAA model. Despite the fact that the same algorithm was utilized, the Ethos AXB model and the Halcyon AXB model still exhibited variations across a range of tests, although these variations were predominantly insignificant in the clinical environment. The accuracy of the Ethos AXB model has been successfully verified in this study and is considered appropriate for the current clinical scope. On the basis of this study, clinical physicists can perform a data validation instead of a full data commissioning when implementing the Ethos system, thereby adopting a more efficient approach for Ethos installation.

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“…The detector housing also affects its directional dependence; it therefore seems to be very important to verify the response of the detector in the given set-up. This is true for silicon diodes [97], and for diamond detectors [98,99]. A suitable diamond dosimeter must be incorporated into a suitable probe's housing which should not introduce energy dependence.…”

Section: Detector Housingmentioning

confidence: 99%

Diamond Detectors for Radiotherapy X-Ray Small Beam Dosimetry

et al. 2021

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Many new X-Ray treatment machines using small and/or non-standard radiation fields, e.g., Tomotherapy, Cyber-knife, and linear accelerators equipped with high-resolution multi-leaf collimators and on-board imaging system, have been introduced in the radiotherapy clinical routine within the last few years. The introduction of these new treatment modalities has led to the development of high conformal radiotherapy treatment techniques like Intensity Modulated photon Radiation Therapy, Volumetric Modulated Arc Therapy, and stereotactic radiotherapy. When using these treatment techniques, patients are exposed to non-uniform radiation fields, high dose gradients, time and space variation of dose rates, and beam energy spectrum. This makes reaching the required degree of accuracy in clinical dosimetry even more demanding. Continuing to use standard field procedures and detectors in fields smaller than 3 × 3 cm2, will generate a reduced accuracy of clinical dosimetry, running the risk to overshadowing the progress made so far in radiotherapy applications. These dosimetric issues represent a new challenge for medical physicists. To choose the most appropriate detector for small field dosimetry, different features must be considered. Short- and long-term stability, linear response to the absorbed dose and dose rate, no energy and angular dependence, are all needed but not sufficient. The two most sought-after attributes for small field dosimetry are water equivalence and small highly sensitive (high sensitivity) volumes. Both these requirements aim at minimizing perturbations of charged particle fluence approaching the Charged Particle Equilibrium condition as much as possible, while maintaining high spatial resolution by reducing the averaging effect for non-uniform radiation fields. A compromise between different features is necessary because no dosimeter currently fulfills all requirements, but diamond properties seem promising and could lead to a marked improvement. Diamonds have long been used as materials for dosimeters, but natural diamonds were only first used for medical applications in the 80 s. The availability of reproducible synthetic diamonds at a lower cost compared to natural ones made the diffusion of diamonds in dosimetry possible. This paper aims to review the use of synthetic poly and single-crystal diamond dosimeters in radiotherapy, focusing on their performance under MegaVoltage photon beams. Both commercial and prototype diamond dosimeters behaviour are described and analyzed. Moreover, this paper will report the main related results in literature, considering diamond development issues like growth modalities, electrical contacts, packaging, readout electronics, and how do they affect all the dosimetric parameters of interest such as signal linearity, energy dependence, dose-rate dependence, reproducibility, rise and decay times.

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Evaluation of the PTW microDiamond in edge‐on orientation for dosimetry in small fields

Cited by 21 publications

References 34 publications

Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Characterisation of a synthetic diamond detector for end-to-end dosimetry in stereotactic body radiotherapy and radiosurgery

Validation of the preconfigured Varian Ethos Acuros XB Beam Model for treatment planning dose calculations: A dosimetric study

Diamond Detectors for Radiotherapy X-Ray Small Beam Dosimetry

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