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Clinical implementation of MOSFET detectors for dosimetry in electron beams.
Radiother Oncol ; 80(3): 288-95, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16916563
ABSTRACT
BACKGROUND AND

PURPOSE:

To determine the factors converting the reading of a MOSFET detector placed on the patient's skin without additional build-up to the dose at the depth of dose maximum (D(max)) and investigate their feasibility for in vivo dose measurements in electron beams. MATERIALS AND

METHODS:

Factors were determined to relate the reading of a MOSFET detector to D(max) for 4 - 15 MeV electron beams in reference conditions. The influence of variation in field size, SSD, angle and field shape on the MOSFET reading, obtained without additional build-up, was evaluated using 4, 8 and 15 MeV beams and compared to ionisation chamber data at the depth of dose maximum (z(max)). Patient entrance in vivo measurements included 40 patients, mostly treated for breast tumours. The MOSFET reading, converted to D(max), was compared to the dose prescribed at this depth.

RESULTS:

The factors to convert MOSFET reading to D(max) vary between 1.33 and 1.20 for the 4 and 15 MeV beams, respectively. The SSD correction factor is approximately 8% for a change in SSD from 95 to 100 cm, and 2% for each 5-cm increment above 100 cm SSD. A correction for fields having sides smaller than 6 cm and for irregular field shape is also recommended. For fields up to 20 x 20 cm(2) and for oblique incidence up to 45 degrees, a correction is not necessary. Patient measurements demonstrated deviations from the prescribed dose with a mean difference of -0.7% and a standard deviation of 2.9%.

CONCLUSION:

Performing dose measurements with MOSFET detectors placed on the patient's skin without additional build-up is a well suited technique for routine dose verification in electron beams, when applying the appropriate conversion and correction factors.
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Coleções: Bases de dados internacionais Base de dados: MEDLINE Assunto principal: Garantia da Qualidade dos Cuidados de Saúde / Radiometria / Pele / Planejamento da Radioterapia Assistida por Computador / Neoplasias da Mama / Elétrons Tipo de estudo: Guia de prática clínica Aspecto clínico: Diagnóstico / Terapia Limite: Humanos Idioma: Inglês Revista: Radiother Oncol Ano de publicação: 2006 Tipo de documento: Artigo País de afiliação: Holanda