Fractals. Physiologic complexity, scaling, and opportunities for imaging.

Fractal organization and behavior is an important and ubiquitous feature of biologic systems. Recognition of the properties and scaling relations can yield important clues regarding the underlying anatomy and physiology of most organs. Potential applications are many, and this brief article has considered only a few areas where there has been progress to date. Recognition of the importance of physiologic scaling has application regarding: proper extrapolation of drug doses from laboratory to human; understanding body mass and surface area relationships related to growth and development; the kinetics of basic biochemical reactions; stress-strain relationships of osteostructural development; and numerous other important processes. As imagers with access to a wide range of sophisticated instrumentation employing diverse probes to extract anatomic, and increasingly physiologic, information, radiologists are poised to use the features of fractals and nonlinear processes to expand the scope and precision of diagnostic information available for patient care.