ATTENUATION OF MONOCHROMATIC X-RAYS BY NORMAL AND ABNORMAL BREAST TISSUES

RATIONALE AND OBJECTIVES. A prior study indicated that differences in the x-ray linear attenuation coefficients of cancerous and normal brea st tissues tend to increase as the energy of the incident beam decreas es. The authors investigated x-ray energies down to 20 keV. In the cur rent study, the linear attenuation coefficients for normal and selecte d cancerous breast tissues within the energy range of 14 to 18 keV wer e determined. METHODS. Fifty breast biopsy specimens consisting of a m ixture of breast malignancies, normal tissues, fat specimens, and tumo rs grown in rats were used. X-ray linear attenuation coefficients were measured for each sample within the energy range of 14.15 to 18 keV, using monoenergetic x-rays from beamline X-19A at the National Synchro tron Light Source at Brookhaven National Laboratory. Each sample was m easured at 130 different energies starting at 14.15 keV with step size s of 0.030 keV. Correlation of the measured attenuation coefficients f or cellular makeup was performed. RESULTS. The mean of linear attenuat ion coefficients for samples classified as ''cancers'' was 10.9% highe r mean of samples classified as ''normal'' breast tissues and was 66.5 % higher than the mean of samples classified as normal breast fat. CON CLUSIONS. Differences in the linear attenuation coefficients of monoch romatic x-rays between 14.15 and 18 keV do exist between normal and ca ncerous tissues, but there is some degree of overlap.