Measurements of the Influence of Thermoplastic Mask in High Energy Photon Beams: Gel Dosimeter or Ionizing Chamber?

Journal Article · Wed Dec 02 04:00:00 EST 2009 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3275652· OSTI ID:21371331

Moreira, M V ^[1]; Petchevist, C D ^[2]; Almeida, A de ^[1]

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1. Departamento de Fisica e Matematica, FFCLRP-USP, Av. Bandeirantes, 3900-CEP 14040-901, Bairro Monte Alegre-Ribeirao Preto, SP (Brazil)
2. Instituto de Radioterapia e Megavoltagem-IRMEV, Rua Sete de Setembro 1150, Higienopolis, Ribeirao Preto, SP (Brazil)

The influence of the immobilization mask material on the absorbed dose distribution in patients exposed to radiotherapy treatment with photon beams has been investigated for photons from a 60Co source and a 6 MV Linac. Absorbed dose values have been inferred at different depths and in the build-up region. Dose measurements were obtained using Fricke Xylenol Gel dosimeter and the cylindrical PTW Freiburg TM 31016-0.016 cc ionizing micro chamber; their discrepancies are discussed. The affinities of FXG and PTW ICMicro for measurements with high energy photons and the difference in the effective atomic numbers due to their compositions are most likely the most important factors that contribute to the measured dose in the build-up region. The measured values show that the use of the mask material contributes to increase the absorbed doses near the surface of the tissue. The result also shows that the build-up effect for {sup 60}Co is significantly smaller than that for 6 MV photons; however, the variations noted in the final doses of the radiotherapic treatments with photons of high energy do not represent alterations in the total doses received by the patients submitted to the radiotherapy.

• OSTI ID: 21371331
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1194; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
ACCELERATORS
BEAMS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BOSONS
BUILDUP
COBALT 60
COBALT ISOTOPES
COLLOIDS
DISPERSIONS
DOSEMETERS
DOSES
DOSIMETRY
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
GAMMA DOSIMETRY
GAMMA RADIATION
GELS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZATION CHAMBERS
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LINEAR ACCELERATORS
MASSLESS PARTICLES
MATERIALS
MEASURING INSTRUMENTS
MEDICINE
MINUTES LIVING RADIOISOTOPES
MONITORING
NUCLEAR MEDICINE
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PATIENTS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHOTON BEAMS
PHOTONS
PLASTICS
POLYMERS
RADIATION DETECTORS
RADIATION DOSES
RADIATION MONITORING
RADIATIONS
RADIOISOTOPES
RADIOLOGY
RADIOTHERAPY
SYNTHETIC MATERIALS
THERAPY
THERMOPLASTICS
YEARS LIVING RADIOISOTOPES