No abstract

The average glandular tissue dose in mammography is generally determined from published tables with knowledge of the breast entrance skin exposure, x-ray tube target material, beam quality (half-value layer [HVL]), breast thickness, and breast composition. Using a carefully designed and experimentally validated Monte Carlo simulation, the authors found that average glandular dose also depends on x-ray tube voltage and, to a lesser extent, on x-ray tube voltage waveform. For currently employed molybdenum target-molybdenum filter source assemblies, a difference in dose of 10% or more is possible in estimating the average glandular dose obtained with different x-ray tube voltages but with the same HVL. Presented are normalized average glandular tissue doses in units of radiation absorbed dose per unit entrance skin exposure for different tube voltages and tube voltage waveforms as well as for different breast thicknesses and compositions and beam filtrations.

DgN values presented permit practical evaluations of average glandular doses for Mo-Rh and Rh-Rh mammography. At a given potential, dose savings are realized with Mo-Rh and Rh-Rh source assemblies.

Theoretical foundation and design considerations of a clinical feasible x-ray phase contrast imaging technique were presented in this paper. Different from the analysis of imaging phase object with weak absorption in literature, we proposed a new formalism for in-line phase-contrast imaging to analyze the effects of four clinically important factors on the phase contrast. These are the body parts attenuation, the spatial coherence of spherical waves from a finite-size focal spot, and polychromatic x-ray and radiation doses to patients for clinical applications. The theory presented in this paper can be applied widely in diagnostic x-ray imaging procedures. As an example, computer simulations were conducted and optimal design parameters were derived for clinical mammography. The results of phantom experiments were also presented which validated the theoretical analysis and computer simulations.

Acceptable chest CT screening can be accomplished at an overall average effective dose of approximately 2 mSv as compared with an average effective dose of 7 mSv for a typical standard-dose chest CT examination.