Effect of dosimeter type for commissioning small photon beams on calculated dose distribution in stereotactic radiosurgery

García‐Garduño, Olivia Amanda; Rodriguez-Ponce, M.; Gamboa‐deBuen, I.; Rodríguez‐Villafuerte, M.; Cruz, O. O. Galván de la; Rivera-Montalvo, T.

doi:10.1118/1.4892176

Cited by 10 publications

(15 citation statements)

References 36 publications

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“…The microLion has been discontinued by manufacturer and is not available commercially. For the Gafchromic EBT2/3 films, proper precautions and experience is needed for achieve comparable data (59)(60)(61). User should also evaluate the criterion for correction-less dosimetry if there is any doubt as discussed by Kamio and Bouchard (57).…”

Section: Discussionmentioning

confidence: 99%

“…The notation f ref denotes the conventional reference field in dosimetry protocols for which the calibration coefficient of an ionization chamber in terms of absorbed dose to water is provided by a standard laboratory and Q is the beam quality of f ref . The f msr is the machinespecific-reference field, N D,w is the chamber specific calibration coefficient in terms of absorbed dose to water for 60 Co, and k Q,Qo is chamber specific beam quality calibration factor. Unfortunately the last term in Eq 1 the k values are not readily available and there is some variability in the literature.…”

Section: Iaea Approachmentioning

confidence: 99%

See 1 more Smart Citation

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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Section: Discussionmentioning

confidence: 99%

Section: Iaea Approachmentioning

confidence: 99%

Small field dosimetry: What have we learnt?

Das

Morales

Francescon

2016

AIP Conference Proceedings

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“…The calculation grid size was set to 2 mm (see Fig 2E–2G ). Note that García-Garduño et al [ 2 ] previously showed that the gamma index criteria were not sensitive to the calculation grid size for circular cone-based radiosurgery.…”

Section: Methodsmentioning

confidence: 98%

“…Problems related with the dosimetry of small radiotherapy photon beams have been extensively discussed in the literature [ 1 ]. In response these problems, many detectors have been manufactured specifically for the dosimetry of small photon beams with certain advantages and disadvantages [ 2 ]. In particular, silicon-diode-based detectors have been commonly used because of their relatively small volumes and high sensitivity to ionizing radiation [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

“…These correction factors are of interest because they may modify the dosimetry data used to commission treatment planning systems (TPS) and impact the calculation of dose distributions. According to the American Association of Physicists in Medicine (AAPM) Task Group 53, an important source of uncertainty in the dose calculation is the accuracy of the original measured data [ 2 , 11 ]. Therefore, the impact of these factors on the calculated dose distributions performed by the TPS in the commissioning of small photon beams must be better understood.…”

Section: Introductionmentioning

confidence: 99%

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Detector-specific correction factors in radiosurgery beams and their impact on dose distribution calculations

2018

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Silicon-diode-based detectors are commonly used for the dosimetry of small radiotherapy beams due to their relatively small volumes and high sensitivity to ionizing radiation. Nevertheless, silicon-diode-based detectors tend to over-respond in small fields because of their high density relative to water. For that reason, detector-specific beam correction factors () have been recommended not only to correct the total scatter factors but also to correct the tissue maximum and off-axis ratios. However, the application of to in-depth and off-axis locations has not been studied. The goal of this work is to address the impact of the correction factors on the calculated dose distribution in static non-conventional photon beams (specifically, in stereotactic radiosurgery with circular collimators). To achieve this goal, the total scatter factors, tissue maximum, and off-axis ratios were measured with a stereotactic field diode for 4.0-, 10.0-, and 20.0-mm circular collimators. The irradiation was performed with a Novalis® linear accelerator using a 6-MV photon beam. The detector-specific correction factors were calculated and applied to the experimental dosimetry data for in-depth and off-axis locations. The corrected and uncorrected dosimetry data were used to commission a treatment planning system for radiosurgery planning. Various plans were calculated with simulated lesions using the uncorrected and corrected dosimetry. The resulting dose calculations were compared using the gamma index test with several criteria. The results of this work presented important conclusions for the use of detector-specific beam correction factors ( in a treatment planning system. The use of for total scatter factors has an important impact on monitor unit calculation. On the contrary, the use of for tissue-maximum and off-axis ratios has not an important impact on the dose distribution calculation by the treatment planning system. This conclusion is only valid for the combination of treatment planning system, detector, and correction factors used in this work; however, this technique can be applied to other treatment planning systems, detectors, and correction factors.

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The impact of corrected field output factors based on IAEA/AAPM code of practice on small‐field dosimetry to the calculated monitor unit in eclipse™ treatment planning system

Mamesa

Oonsiri

Sanghangthum

et al. 2020

J Applied Clin Med Phys

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The objective of this study was to investigate the effect of field output factors (FOFs) according to the current protocol for small‐field dosimetry in conjunction to treatment planning system (TPS) commissioning. The calculated monitor unit (MU) for intensity‐modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans in Eclipse™ TPS were observed. Micro ion chamber (0.01 CC) (CC01), photon field diode (shielded diode) (PFD), and electron field diode (unshielded diode) (EFD) were used to measure percentage depth doses, beam profiles, and FOFs from 1 × 1 cm2 to 10 × 10 cm2 field sizes of 6 MV photon beams. CC01 illustrated the highest percentage depth doses at 10 cm depth while EFD exhibited the lowest with the difference of 1.6% at 1 × 1 cm2. CC01 also produced slightly broader penumbra, the difference with other detectors was within 1 mm. For uncorrected FOF of three detectors, the maximum percent standard deviation (%SD) was 5.4% at 1 × 1 cm2 field size. When the correction factors were applied, this value dropped to 2.7%. For the calculated MU in symmetric field sizes, beam commissioning group from uncorrected FOF demonstrated maximum %SD of 6.0% at 1 × 1 cm2 field size. This value decreased to 2.2% when the corrected FOF was integrated. For the calculated MU in IMRT‐SRS plans, the impact of corrected FOF reduced the maximum %SD from 6.0% to 2.5% in planning target volume (PTV) less than 0.5 cm3. Beam commissioning using corrected FOF also decreased %SD for VMAT‐SRS plans, although it was less pronounced in comparison to other treatment planning techniques, since the %SD remained less than 2%. The use of FOFs based on IAEA/AAPM TRS 483 has been proven in this research to reduce the discrepancy of calculated MU among three beam commissioning datasets in Eclipse™ TPS. The dose measurement of both symmetric field and clinical cases comparing to the calculation illustrated the dependence of the types of detector commissioning and the algorithm of the treatment planning for small field size.

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Effect of dosimeter type for commissioning small photon beams on calculated dose distribution in stereotactic radiosurgery

Cited by 10 publications

References 36 publications

Small field dosimetry: What have we learnt?

Small field dosimetry: What have we learnt?

Detector-specific correction factors in radiosurgery beams and their impact on dose distribution calculations

The impact of corrected field output factors based on IAEA/AAPM code of practice on small‐field dosimetry to the calculated monitor unit in eclipse™ treatment planning system

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