From living being to medical image--bridging the dimensionality gap

The human body is viewed, in the context of medical imaging, as a multiplicity of three-dimensional time-varying images, coinciding in time and space. Medical imaging modalities that are well established, or are undergoing clinical trials, or are at the tentative proposal stage, are tabulated. Also listed are the types of radiation and other physical processes employed to gather the image data, the physical parameters which can be imaged, and the physiological attributes represented by these parameters. Image reconstruction algorithms are reviewed and possible improvements are assessed. The processing of multidimensional information is emphasised as of primary concern for future progress in medical imaging. Such processing is seen to be developing along two converging paths: the processing of information from coincident images of different parameter distributions, and the processing of time-sequential images of a single parameter distribution. The images referred to have three spatial dimensions, implying that a challenge for future medical imaging systems is conjectured to be the efficient distillation of useful information (which must include the most effective means of image display) from multiple sets of time-varying volume data. Medical diagnosis can always profit from improved interpretation of information provided by the multifarious types of radiation and other physical processes which are employed in established and tentative medical imaging techniques. There is a premium on parameter sets that provide independent information and on processes, such as magnetic fields, ultrasound, and low frequency electric currents, which are free of the stigma associated with ionising radiations. Promising avenues of exploration are identified.