Chemical lesions classification

Yet another classification system refers to the nature of the host s response to the causative agent. Some agents, referred to as intrinsic hepatotoxicants, will cause hepatotoxicity in most individuals of most species. In the case of idiosyncratic hepatotoxicants, where a chemical s toxic effects are a function of unusual susceptibility of the exposed individual, it may not be clear whether the lesion is a manifestation of the hepatotoxic properties of the substance in question or a manifestation of the individual s untoward response to the agent. This response may mean hypersensitivity (allergic) reactions or exaggerated responses to minor alterations in liver function. For example, anabolic or contraceptive steroids cause diminished biliary excretion (cholestasis) in most... 

A.2.2.2.2 Animal irritant responses within a test can be quite variable, as they are with corrosion. A separate irritant criterion accommodates cases when there is a significant irritant response but less than the mean score criterion for a positive test. For example, a substance might be designated as an irritant if at least 1 of 3 tested animals shows a very elevated mean score throughout the study, including lesions persisting at the end of an observation period of normally 14 days. Other responses could also fulfil this criterion. However, it should be ascertained that the responses are the result of chemical exposure. Addition of this criterion increases the sensitivity of the classification system. 

One of the limitations of CT is that tissues of different chemical composition but the same X-ray attenuation have the same Flounsfield values. This makes the differentiation and classification of tissue types challenging. Classical examples are the differentiation between calcified plaques and iodinated blood or hyper-dense and contrast-enhanced lesions. 

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