[Computer tomographic densitometry of formalin-fixed and frozen human tissue (author's transl)]

The degree of radiation absorption of various human tissues of known histology and known water content was measured at temperatures below freezing point and after fixation in formalin of various concentrations. Computer tomographic "density" showed the least change with tissues in 6% formalin. Higher and lower concentrations of formalin caused considerable changes in radiation absorption. Pure water below freezing point produces a reduction in density of 80 Hounsfield units; consequently, densitometry of frozen sections is pointless. Comparisons of CT density before and after freezing give some indications of chemical composition.