The pathogenesis of radiation injury in complex tissues: an overview of problems and probes

The evaluation of radiation injury in complex organs has tended to lag behind comparable areas of investigative interest. This observation is somewhat surprising in view of the increased use of radiotherapy as a primary or adjuvant mode of therapy for malignant disease. In part, this problem appears to relate to the difficulty of identifying and quantifying the morphologic consequences of radiation injury in complex organs, in which the various component tissues exhibit a broad spectrum of radiosensitivities. Two approaches have been employed to address this problem: (1) utilization of sophisticated probes to evaluate the functional and morphologic sequelae of radiation injury and (2) segmentation of complex tissues into their component parts, which are then evaluated individually. Both approaches are illustrated in the papers presented in this issue. The purpose of this overview is to call attention to some of the attendant difficulties of the former approach, as seen in an ongoing investigative program concerned with radiation injury of the kidney.