Scanning electron microscopy of tissue response to irradiation.

Much of the work done so far with scanning electron microscopy to explore tissue damage by irradiation has used mouse or rat small intestine as a model. Variations are described in the response of this model with time after radiation, with dosage, with the method of irradiation and with the type of radiation. In the mouse, damage is expressed as a progression from normal finger shaped villi through the following stages: lateral villous collapse, vertical villous collapse, conical villi, rudimentary villi and flat mucosa, sometimes with ulceration. The presence of giant enterocytes is described and their relationship to time after radiation is discussed. The response of other organs is compared with that of small intestine and different methods are discussed for the assessment of the surface effects of radiation. A new method is proposed for assessing the relative effects of different types of radiation by defining the dosages required to produce two clearly recognizable effects, vertical villous collapse and conical villi. In conclusion, radiation damage is compared with other mucosal lesions and the areas most needing further work are highlighted.