Quality Assurance and Commissioning

Schneider, Frank; Clausen, Sven; Eaton, David J.

doi:10.1007/978-3-642-39821-6_4

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…The dose at a reference depth is then related to a measurement made in air with the user's PTW 23342 chamber mounted in a QA tool (termed PAICH (probe adjuster/ionization chamber holder)), allowing for daily output verification (Hensley 2017). Any small differences in daily output are accounted for by adjusting the treatment time (Schneider et al 2014). While this QA system ensures that dose delivered by the INTRABEAM is reproducible, it does not provide a measure of absolute dose.…”

Section: P G F Watson Et Almentioning

confidence: 99%

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

Watson¹,

Popović²,

Seuntjens³

2017

Phys. Med. Biol.

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Electronic brachytherapy sources are widely accepted as alternatives to radionuclide-based systems. Yet, formal dosimetry standards for these devices to independently complement the dose protocol provided by the manufacturer are lacking. This article presents a formalism for calculating and independently verifying the absorbed dose to water from a kV x-ray source (The INTRABEAM System) measured in a water phantom with an ionization chamber calibrated in terms of air-kerma. This formalism uses a Monte Carlo (MC) calculated chamber conversion factor, [Formula: see text], to convert air-kerma in a reference beam to absorbed dose to water in the measurement beam. In this work [Formula: see text] was determined for a PTW 34013 parallel-plate ionization chamber. Our results show that [Formula: see text] was sensitive to the chamber plate separation tolerance, with differences of up to 15%. [Formula: see text] was also found to have a depth dependence which varied with chamber plate separation (0 to 10% variation for the smallest and largest cavity height, over 3 to 30 mm depth). However for all chamber dimensions investigated, [Formula: see text] was found to be significantly larger than the manufacturer reported value, suggesting that the manufacturer recommended method of dose calculation could be underestimating the dose to water.

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Section: P G F Watson Et Almentioning

confidence: 99%

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

Watson¹,

Popović²,

Seuntjens³

2017

Phys. Med. Biol.

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“…An additional Aluminum filter layer is embedded inside the small applicators (≤3 cm) to balance the beam hardening level and also protect the applicator shaft from the excess leakage. In greater applicator (≥3.5 cm) the thickness of the material creates sufficient beam hardening, so the Aluminum layer is eliminated in the construction of these big applicators [17]. All of the spherical applicator diameters and the bare probe alone were considered at this work.…”

Section: Simulation Of Released Secondary Electrons Around the Probe And Different Spherical Applicator Diametersmentioning

confidence: 99%

Impact of spherical applicator diameter on relative biologic effectiveness of low energy IORT X-rays: A hybrid Monte Carlo study

et al. 2020

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Low-kV IORT (Low kilovoltage intraoperative radiotherapy) using INTRABEAM machine and dedicated spherical applicators is a candidate modality for breast cancer treatment. The current study aims to quantify the RBE (relative biologic effectiveness) variations of emitted X-rays from the surface of different spherical applicators and bare probe through a hybrid Monte Carlo (MC) simulation approach. Materials and methods: A validated MC model of INTRABEAM machine and different applicator diameters, based on GEANT4 Toolkit, was employed for RBE evaluation. To doing so, scored X-ray energy spectra at the surface of each applicator diameter/bare probe were used to calculate the corresponding secondary electron energy spectra at various distances inside the water and breast tissue. Then, MCDS (Monte Carlo damage simulation) code was used to calculate the RBE values according to the calculated electron spectra. Results: Presence of spherical applicators can increase the RBE of emitted X-rays from the bare probe by about 22.3%. In return, changing the applicator diameter has a minimal impact (about 3.2%) on RBE variation of emitted X-rays from each applicator surface. By increasing the distance from applicator surface, the RBE increments too, so that its value enhances by about 10% with moving from 2 to 10 mm distance. Calculated RBE values within the breast tissue were higher than those of water by about 4% maximum value. Conclusion: Ball section of spherical IORT applicators can affect the RBE value of the emitted X-rays from INTRABEAM machine. Increased RBE of breast tissue can reduce the prescribed dose for breast irradiation if INTRABEAM machine has been calibrated inside the water.

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“…49 Suggested QA programmes have been published for the INTRABEAM 11,50 and Xoft devices. 51 These have been incorporated into Table 3 to give a suggested program for all EB devices.…”

Section: Dosimetry Auditmentioning

confidence: 99%

Electronic brachytherapy—current status and future directions

Eaton¹

2015

BJR

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In the past decade, electronic brachytherapy (EB) has emerged as an attractive modality for the treatment of skin lesions and intraoperative partial breast irradiation, as well as finding wider applications in intracavitary and interstitial sites. These miniature X-ray sources, which operate at low kilovoltage energies (,100 kV), have reduced shielding requirements and inherent portability, therefore can be used outside the traditional realms of the radiotherapy department. However, steep dose gradients and increased sensitivity to inhomogeneities challenge accurate dosimetry. Secondly, ease of use does not mitigate the need for close involvement by medical physics experts and consultant oncologists. Finally, further studies are needed to relate the more heterogeneous dose distributions to clinical outcomes. With these provisos, the practical convenience of EB strongly suggests that it will become an established option for selected patients, not only in radiotherapy departments but also in a range of operating theatres and clinics around the world.

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Quality Assurance and Commissioning

Cited by 5 publications

References 18 publications

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

Impact of spherical applicator diameter on relative biologic effectiveness of low energy IORT X-rays: A hybrid Monte Carlo study

Electronic brachytherapy—current status and future directions

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