Quality assurance of the dose delivered by small radiation segments.
Authors
Hansen, V NEvans, P M
Budgell, Geoff J
Mott, Judith
Williams, Peter C
Brugmans, M J
Wittkämper, F W
Mijnheer, B J
Brown, K
Affiliation
Joint Department of Physics, Royal Marsden NHS Trust and Institute of Cancer Research, Sutton, Surrey, UK.Issue Date
1998-09
Metadata
Show full item recordAbstract
The use of intensity modulation with multiple static fields has been suggested by many authors as a way to achieve highly conformal fields in radiotherapy. However, quality assurance of linear accelerators is generally done only for beam segments of 100 MU or higher, and by measuring beam profiles once the beam has stabilized. We propose a set of measurements to check the stability of dose delivery in small segments, and present measured data from three radiotherapy centres. The dose delivered per monitor unit, MU, was measured for various numbers of MU segments. The field flatness and symmetry were measured using either photographic films that are subsequently scanned by a densitometer, or by using a diode array. We performed the set of measurements at the three radiotherapy centres on a set of five different Philips SL accelerators with energies of 6 MV, 8 MV, 10 MV and 18 MV. The dose per monitor unit over the range of 1 to 100 MU was found to be accurate to within +/-5% of the nominal dose per monitor unit as defined for the delivery of 100 MU for all the energies. For four out of the five accelerators the dose per monitor unit over the same range was even found to be accurate to within +/-2%. The flatness and symmetry were in some cases found to be larger for small segments by a maximum of 9% of the flatness/symmetry for large segments. The result of this study provides the dosimetric evidence that the delivery of small segment doses as top-up fields for beam intensity modulation is feasible. However, it should be stressed that linear accelerators have different characteristics for the delivery of small segments, hence this type of measurement should be performed for each machine before the delivery of small dose segments is approved. In some cases it may be advisable to use a low pulse repetition frequency (PRF) to obtain more accurate dose delivery of small segments.Citation
Quality assurance of the dose delivered by small radiation segments. 1998, 43 (9):2665-75 Phys Med BiolJournal
Physics in Medicine and BiologyDOI
10.1088/0031-9155/43/9/017PubMed ID
9755953Type
ArticleLanguage
enISSN
0031-9155ae974a485f413a2113503eed53cd6c53
10.1088/0031-9155/43/9/017
Scopus Count
Collections
Related articles
- Dosimetric properties of a scanned beam microtron at low monitor unit settings: importance for conformal therapy.
- Authors: Humm JL, Larsson A, Lief EP
- Issue date: 1996 Mar
- Performance characterization of siemens primus linear accelerator under small monitor unit and small segments for the implementation of step-and-shoot intensity-modulated radiotherapy.
- Authors: Reena P, Dayananda S, Pai R, Jamema SV, Gupta T, Deepak D, Rajeev S
- Issue date: 2006 Oct
- Improvements in dose accuracy delivered with static-MLC IMRT on an integrated linear accelerator control system.
- Authors: Li J, Wiersma RD, Stepaniak CJ, Farrey KJ, Al-Hallaq HA
- Issue date: 2012 May
- A statistical analysis of ionometrically measured 6-MV x-ray beam parameters.
- Authors: Dawson DJ, Gribble MA
- Issue date: 1984 Sep-Oct
- A study of dose delivery in small segments.
- Authors: Malet C, Ginestet C, Hall K, Lafay F, Sunyach M, Carrie C
- Issue date: 2000 Sep 1