Normalized glandular dose (DgN) coefficients from experimental mammographic x-ray spectra

Autor(es)

Santos, Josilene C. ^[1] ; Tomal, Alessandra ^[2] ; de Barros, Nestor ^[3] ; Costa, Paulo R. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Fis, BR-05508090 Sao Paulo, SP - Brazil

^[2] IFGW UNICAMP, Inst Fis Gleb Wataghin, BR-13083859 Campinas, SP - Brazil

^[3] Univ Sao Paulo, Fac Med, BR-05403900 Sao Paulo, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Physics in Medicine and Biology; v. 64, n. 10 MAY 2019.
• Citações Web of Science: 0

Resumo

Mean glandular dose is the quantity used for dosimetry in mammography and depends on breast-related characteristics, such as thickness and density, and on the x-ray spectrum used for breast imaging. This work aims to present an experimentally-based method to derive polyenergetic normalized glandular dose coefficients (DgN(p)) from the spectral difference between x-ray spectra incident and transmitted through breast phantoms with glandular/adipose proportions of 30/70 and 50/50 and thicknesses up to 4.5 cm. The spectra were produced by a Mammomat 3000 Nova system using radiographic techniques commonly applied for imaging compressed breast thickness lower than 6 cm (Mo/Mo, Mo/Rh and W/Rh spectra at 26 and 28 kVp). DgN(p) coefficients were compared with values estimated using Boones' method and data from breast images (DICOM Organ Dose and VolparaDose calculations). The DgN(p) were also evaluated in layers into the phantoms (depth-DgN(p)) using both x-ray spectra and thermoluminescent dosimeters (TLD-100). Maximum differences between DgN(p) from the method presented in this study and results using Boone's method was 11%, with larger differences for Mo/Rh spectra in relation to the Mo/Mo. The DgN(p) maximum differences to the coefficients obtained using patient images were 8.0%, for the DgN calculated using Volpara and 6.4% for the DgN from DICOM Organ Dose, for a 4.5 cm breast phantom with 30% glandularity. The DgN(p) estimated from the depth-DgN(p) distributions differ up to 5.2% to the coefficients obtained using the pair incident-transmitted spectra to calculate the DgN(p) directly in the whole phantom. The depth-DgN(p) distributions estimated with TLDs were consistent with the results observed using the experimental spectra, with maximum difference of 3.9%. In conclusion, polyenergetic x-ray spectrometry proved to be an applicable tool for research in dosimetry in mammography allowing spectral characterization. This approach can also be useful for investigation of the influence of x-ray spectra on glandular dose. (AU)

• Processo FAPESP: 13/07117-0 - Determinação experimental da distribuição da dose glandular média em diferentes qualidades de feixes mamográficos
• Beneficiário: Josilene Cerqueira Santos
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 10/12237-7 - Estudo experimental das relações entre Kerma no ar e equivalente de dose ambiente para o cálculo de barreiras primárias em salas radiológicas
• Beneficiário: Paulo Roberto Costa
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 15/21873-8 - Desenvolvimento e implementação de metodologias para otimização de técnicas de imagens em radiologia digital
• Beneficiário: Alessandra Tomal
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 08/57863-2 - P&D em metrologia das radiações
• Beneficiário: Linda Viola Ehlin Caldas
• Modalidade de apoio: Auxílio à Pesquisa - Temático