Fractal analysis--a new approach in brain receptor imaging

Improvements in detector technology and the development of radioligands for brain receptor imaging have introduced exiting new insights into the pathophysiology of various neuropsychiatric disorders and have improved the possibilities of optimizing the treatment for patients suffering from them. Positron emission tomography (PET) and single-photon emission tomography (SPET) with tailored radiopharmaceuticals provide information on the topographic physiological chemistry of the living human brain. The different patterns of brain receptor densities and distribution can be imaged and modelled with PET and SPET. The normal receptor distribution in the brain is broadly heterogeneous with different cortical layers, which show receptor densities varying from very low to high. Further exploration of the data shows that human neurophysiology and neural architectures possess fractal properties that may be altered during activation and in different neuropsychiatric disorders. This review highlights recent findings in SPET receptor imaging and the use of fractal analysis in the interpretation of images representing various neuropsychiatric disorders.