X-ray spectral measurements for tungsten-anode from 20 to 49 kVp on a digital breast tomosynthesis system

• Published in: Medical physics (Lancaster) 2012-06, Vol.39 (6), p.3493-3500
• Main Authors: Zhang, Da, Li, Xinhua, Liu, Bob
• Format: Article
• Language: English
• Subjects: ALUMINIUM; ANODES; biomedical equipment; Biomedical instrumentation and transducers, including micro‐electro‐mechanical systems (MEMS); BIOMEDICAL RADIOGRAPHY; Computerised tomographs; computerised tomography; COMPUTERIZED TOMOGRAPHY; digital breast tomosynthesis; Digital mammography; Gamma Rays; II‐VI semiconductors; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; MAMMARY GLANDS; Mammography; Measurement of nuclear or x‐radiation; Medical imaging; Medical X‐ray imaging; PHOTONS; Radiographic Image Enhancement - methods; semiconductor counters; SEMICONDUCTOR DETECTORS; Solid‐state detectors; spectroscopy; Spectrum Analysis - methods; STRIPPING; Tomography - methods; Tubes for determining the presence, intensity, density or energy of radiation or particles; TUNGSTEN; X RADIATION; X-RAY SPECTRA; X-RAY SPECTROSCOPY; x-ray spectrum; X‐ and γ‐ray spectroscopy; X‐ray detectors; X‐ray spectrometers
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4719958

Purpose: This paper presents new spectral measurements of a tungsten-target digital breast tomosynthesis (DBT) system, including spectra of 43–49 kVp. Methods: Raw x-ray spectra of 20–49 kVp were directly measured from the tube port of a Selenia Dimensions DBT system using a CdTe based spectrometer. Two configurations of collimation were employed: one with two tungsten pinholes of 25 μ m and 200 μ m diameters, and the other with a single pinhole of 25 μ m diameter, for acquiring spectra from the focal spot and from the focal spot as well as its vicinity. Stripping correction was applied to the measured spectra to compensate distortions due to escape events. The measured spectra were compared with the existing mammographic spectra of the TASMIP model in terms of photon fluence per exposure, spectral components, and half-value layer (HVL). HVLs were calculated from the spectra with a numerical filtration of 0.7 mm aluminum and were compared against actual measurements on the DBT system using W/Al (target-filter) combination, without paddle in the beam. Results: The spectra from the double-pinhole configuration, in which the acceptance aperture pointed right at the focal spot, were harder than the single-pinhole spectra which include both primary and off-focus radiation. HVL calculated from the single-pinhole setup agreed with the measured HVL within 0.04 mm aluminum, while the HVL values from the double-pinhole setup were larger than the single-pinhole HVL by at most 0.1 mm aluminum. The spectra from single-pinhole setup agreed well with the TASMIP mammographic spectra, and are more relevant for clinical purpose. Conclusions: The spectra data would be useful for future research on DBT system with tungsten targets.