Source:http://linkedlifedata.com/resource/umls/id/C0011321
MSH: The measurement of the density of a material by measuring the amount of light or radiation passing through (or absorbed by) the material.,CSP: determination of variations in density by comparison with that of another material, or with a certain standard.,NCI: Measuring the optical density of a substance by shining light on it and measuring its transmission. (WordNet)