An empirical relationship for determining photon beam quality in TG-21 from a ratio of percent depth doses

Followill, David S; Tailor, Ramesh; Tello, Victor M.; Hanson, W. F.

doi:10.1118/1.598396

Cited by 37 publications

(20 citation statements)

References 3 publications

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“…25. Measurements made by Followill et al 26 on 685 photon beams from 45 different accelerators with energies ranging from 4 MV to 25 MV have shown very few TPR 20,10 values above 0.8 approximately, and their estimated water/air stopping-power ratios for the entire data set had a spread of Ϯ0.25%. For the few beams with TPR 20,10 higher than 0.75 or so, the steep gradient of the stopping-power ratio vs TPR 20,10 curve could result in the propagation of possible errors in measuring TPR 20,10 into larger variations in stopping-power ratios, and therefore in k Q , than for lower beam qualities but these variations will, in most cases, not be larger than 0.5%.…”

Section: Advantages and Disadvantages Of Tpr 2010mentioning

confidence: 98%

On the beam quality specification of high‐energy photons for radiotherapy dosimetry

Andreo

2000

Medical Physics

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An overview of common photon beam quality specifiers used in radiotherapy dosimetry introduces a reasoned discussion on the advantages and disadvantages of TPR20,10 and PDD(10)x. It is shown that some of the potential advantages of PDD(10)x are also present in other well known beam quality specifiers such as d80. However, all PDD-based beam quality indices, including PDD(10)x, are subject to electron contamination and their determination is affected by practical limitations. The proposed filtration of contaminant electrons by Kosunen and Rogers [Med. Phys. 20, 1181-1188 (1993)] and by Li and Rogers [Med. Phys. 21, 791-798 (1994)] is questioned, not only with regard to the adequacy of using lead as an electron filter, but also in relation to its efficiency (if there were no contamination, restrictions for beam calibrations at dmax would be removed) and practical measurement. It is argued that (i) there is no unique beam quality specifier that works satisfactorily in all possible conditions, for the entire energy range of photon energies used in radiotherapy and all possible accelerators used in hospitals and in standards laboratories, and (ii) TPR20,10 remains to be the most appropriate specifier for clinical photon beams as it has less practical drawbacks than PDD-based quality indices. The final impact on clinical photon beam dosimetry resulting from the use of different photon beam quality specifiers, is that they are not expected to yield a significant change (i.e., more than 0.5% and in most cases well within 0.2%) in the absorbed dose to water in reference conditions for most clinical beams.

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Section: Advantages and Disadvantages Of Tpr 2010mentioning

confidence: 98%

On the beam quality specification of high‐energy photons for radiotherapy dosimetry

Andreo

2000

Medical Physics

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“…According to Followill et al [21], this approach introduces an uncertainty of AE0.01 (with a coverage factor k Z 2) in the calculation of TPR 20 10 .…”

Section: Radiation Sourcesmentioning

confidence: 99%

“…This index is given by the ratio of the dose absorbed in water at depths of 20 and 10 cm, with a distance between the source and the measurement depths of 100 cm and a field at these depths of 10 Â 10 cm. Instead we calculate TPR 20 10 according to [2,21] TPR 20 10 Z1:2661$PDD 20 10 À 0:0595; ð8Þ…”

Section: Radiation Sourcesmentioning

confidence: 99%

Calculation of beam quality correction factors for various thimble ionization chambers using the Monte Carlo code PENELOPE

Erazo

Lallena

2013

Physica Medica

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“…At a minimum, however, a golden beam dataset is an excellent source of quality assurance for verifying the user's commissioning results. These data along with those available from the Radiological Physics Center at MD Anderson Cancer Center [6][7][8] can be used to ensure that the user's beam data are in reasonably good agreement with those from other institutions. Monte Carlo simulation could also provide good standard data.…”

Section: Ib1 Need For Commissioning Datamentioning

confidence: 99%

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

Das

Cheng

Watts³

et al. 2008

Medical Physics

422

424

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For commissioning a linear accelerator for clinical use, medical physicists are faced with many challenges including the need for precision, a variety of testing methods, data validation, the lack of standards, and time constraints. Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. To achieve this goal, Task Group 106 (TG-106) of the Therapy Physics Committee of the American Association of Physicists in Medicine was formed to review the practical aspects as well as the physics of linear accelerator commissioning. The report provides guidelines and recommendations on the proper selection of phantoms and detectors, setting up of a phantom for data acquisition (both scanning and no-scanning data), procedures for acquiring specific photon and electron beam parameters and methods to reduce measurement errors (<1%), beam data processing and detector size convolution for accurate profiles. The TG-106 also provides a brief.discussion on the emerging trend in Monte Carlo simulation techniques in photon and electron beam commissioning. The procedures described in this report should assist a qualified medical physicist in either measuring a complete set of beam data, or in verifying a subset of data before initial use or for periodic quality assurance measurements. By combining practical experience with theoretical discussion, this document sets a new standard for beam data commissioning.

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An empirical relationship for determining photon beam quality in TG-21 from a ratio of percent depth doses

Cited by 37 publications

References 3 publications

On the beam quality specification of high‐energy photons for radiotherapy dosimetry

On the beam quality specification of high‐energy photons for radiotherapy dosimetry

Calculation of beam quality correction factors for various thimble ionization chambers using the Monte Carlo code PENELOPE

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

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