A multi-institutional evaluation of small field output factor determination following the recommendations of IAEA/AAPM TRS-483.
Med Phys
; 49(8): 5537-5550, 2022 Aug.
Article
em En
| MEDLINE
| ID: mdl-35717637
ABSTRACT
PURPOSE:
The aim of this work was to test the implementation of small field dosimetry following TRS-483 and to develop quality assurance procedures for the experimental determination of small field output factors (SFOFs). MATERIALS ANDMETHODS:
Twelve different centers provided SFOFs determined with various detectors. Various linac models using the beam qualities 6 MV and 10 MV with flattening filter and without flattening filter were utilized to generate square fields down to a nominal field size of 0.5 cm × 0.5 cm. The detectors were positioned at 10 cm depth in water. Depending on the local situation, the source-to-surface distance was either set to 90 cm or 100 cm. The SFOFs were normalized to the output of the 10 cm × 10 cm field. The spread of SFOFs measured with different detectors was investigated for each individual linac beam quality and field size. Additionally, linac-type specific SFOF curves were determined for each beam quality and the SFOFs determined using individual detectors were compared to these curves. Example uncertainty budgets were established for a solid state detector and a micro ionization chamber.RESULTS:
The spread of SFOFs for each linac and field was below 5% for all field sizes. With the exception of one linac-type, the SFOFs of all investigated detectors agreed within 10% with the respective linac-type SFOF curve, indicating a potential inter-detector and inter-linac variability.CONCLUSION:
Quality assurance on the SFOF measurements can be done by investigation of the spread of SFOFs measured with multiple detectors and by comparison to linac-type specific SFOFs. A follow-up of a measurement session should be conducted if the spread of SFOFs is larger than 5%, 3%, and 2% for field sizes of 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 2 cm × 2 cm, respectively. Additionally, deviations of measured SFOFs to the linac-type-curves of more than 7%, 3%, and 2% for field sizes 0.5 cm × 0.5 cm, 1 cm × 1 cm, and field sizes larger than 1 cm × 1 cm, respectively, should be followed up.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Aceleradores de Partículas
/
Radiometria
Tipo de estudo:
Clinical_trials
/
Prognostic_studies
Idioma:
En
Revista:
Med Phys
Ano de publicação:
2022
Tipo de documento:
Article
País de afiliação:
Áustria