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1.
J Appl Clin Med Phys ; 20(6): 170-177, 2019 Jun.
Article in English | MEDLINE | ID: mdl-31106990

ABSTRACT

PURPOSE: Although breast density is considered a strong risk factor of breast cancer, its quantitative assessment is difficult. To investigate a quantitative method of measuring breast density using dual-energy mammographic imaging with central digital breast tomosynthesis in physically uniform and nonuniform phantoms. MATERIAL AND METHODS: The dual-energy imaging unit used a tungsten anode and silver filter with 30 kVp for high-energy images and 20 kVp for low-energy images. Uniform glandular-equivalent phantoms were used to calibrate a dual-energy based decomposition algorithm. The first study used uniform breast phantoms which ranged in thicknesses from 20 to 70 mm, in 10-mm increments, and which provided 30%, 50%, and 70% of breast density. The second study used uniform phantoms ranging from 10% to 90% of breast density. The third study used non-uniform phantoms (at an average density of 50%) with a thickness which ranged from 20 to 90 mm, in 10-mm increments. RESULTS: The root mean square error of breast density measurements was 2.64-3.34% for the uniform, variable thickness phantoms, 4.17% for the uniform, variable density phantoms, and 4.49% for the nonuniform, variable thickness phantoms. CONCLUSION: The dual-energy technique could be used to measure breast density with a margin of error of < 10% using digital breast tomosynthesis.


Subject(s)
Breast Density , Breast/pathology , Mammography/instrumentation , Mammography/methods , Phantoms, Imaging , Radiographic Image Enhancement/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Algorithms , Breast Neoplasms/diagnosis , Calibration , Computer Simulation , Female , Humans , Models, Biological
2.
Dentomaxillofac Radiol ; 46(4): 20160395, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28128650

ABSTRACT

OBJECTIVES: To propose an imaging protocol that provides satisfactory image quality for oral examination while minimizing radiation dosage using 320-slice multidetector CT (MDCT). METHODS: An anthropomorphic head phantom was scanned using 320 MDCT with protocols combining different scanning modes: volume scanning (whole or local) vs helical scanning (80- or 64-slice detectors); tube voltage settings (80 kVp, 120 kVp and 135 kVp); and tube current settings (60 mA, 80 mA, 100 mA and 120 mA). A total of six anatomical bone structures and three anatomical soft-tissue structures were assessed using quantitative and qualitative analysis in the three orthographic planes (axial, sagittal and coronal). A figure of merit (FOM) was used to determine the optimal imaging protocol in terms of tube voltage, tube current and scanning mode. RESULTS: The 80-kVp setting had the worst quantitative and qualitative results (both p < 0.001) compared with the 135-kVp and 120-kVp settings, especially for soft-tissue structures. A significant difference was noted for the scores obtained using a tube current between 120 mA and 60 mA by quantitative analysis, but not by qualitative analysis. Volume scans using either whole or local modes had a significantly higher FOM than helical scanning of 80 or 64 slices. CONCLUSIONS: In 320 MDCT, a protocol using 135 kVp, 80 mA and the volume-scanning mode (whole or local) offers adequate visualization of both soft-tissue and bone structures while keeping the radiation dose as low as possible. This may therefore be considered a first choice among a wide selection of scanning protocols for dentomaxillofacial CT.


Subject(s)
Imaging, Three-Dimensional/methods , Multidetector Computed Tomography/methods , Radiography, Dental/methods , Humans , Phantoms, Imaging , Radiation Dosage
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