Determination of X-ray spectra incident on and transmitted through breast tissue

X-ray spectra incident on and transmitted through breast tissue were measured using a fresh whole excised breast. These spectra and corresponding radiographs show that hardening of the beam from a molybdenum-anoda x-ray tube by a 0.5-mm AI filter instead of the conventional 0.03-mm Mo filter allows shorter exposure times and reduces patient exposure. Acceptable image contrast is preserved in mammography of thick or dense breasts.