Effective atomic number and electron density as measured with a computed tomography scanner: computation and...

The mathematical basis and methodology for determining the effective atomic number and electron density of a tissue are presented. Cranial computed tomography (CT) scanning is performed at two different energy levels, both with and without contrast enhancement. The histology of 15 brain tumors has been correlated with the effective atomic number and electron density of the tumor, with parameters of the linear attenuation coefficient, and with statistical values of the CT numbers. The most useful value in separating gliomas from meningiomas from metastases appears to be the percentage change of effective atomic number following contrast enhancement.