[Radiation absorption (CT) and proton relaxation times (MR) in tissue samples of spongy bone]

The contents of the medullary space exercise an influence on the absorption of radiation by spongy tissue of cancellous bone. This quantifiable dependence qualifies the value of CT densitometry of the spongiosa, for the CT number alone will not allow proportionate determination of the three main components: bone mineral, haematopoietic marrow and fat marrow. CT densitometry is reliable only if one can assume constant composition of the marrow. MR reveals hitherto unknown possibilities of noninvasive determination of the fat content in cancellous bone. The present study is limited to the determination of proton relaxation times, among the wide application possibilities offered by spectroscopy.