Functional Imaging Introduction: Gaining ne wi nsight from biophotonic imaging

Mark B. CannellDepartment of Physiology,School of Medical Sciences,The University of Auckland, Auckland, NewZealandOver the past 2 decades, there has been an explosivegrowth in the range of measurement modalities available tothe physiologist. Today,avery large part of theelectromagnetic spectrum is used to probe and recordphysiological function from the levelofthe whole body totissue, cell and evenorg a nelle. This use of photonicmethods includes radio wav e sinthe form of nuclearmagnetic resonance imaging, through light in, for example,microscopyand video imaging, and on to real timefluoroscopywith Xrays. Even gamma rays fromradioisotopes find some imaging applications with gammaray cameras. Perhaps the most common use of photonics inphysiological research is in the area of microscopyand cellbiology.Here we see methods that employalmost most ofthe fundamental features of light itself to generatephysiological images; for example polarization andinterference are routinely used to help generate contrastwithin unlabelled cells.The effort to clarify cell function has been aided bythe development of a wide variety of probes that revealelements of cell function that cannot be directly observedthrough other contrast enhancement methods. With theseprobes we can nowimage intracellular ion levels, vesicletrafficking and evenprotein synthesis and degradationwithin living cells.Although today we talk about “cellbiology” , “neuroscience” and “developmental biology” ascutting edge disciplines, in reality theyare simplyphysiological research repackaged to detach the term“physiology”. It is possible that a part of this has arisenfrom the viewthat the more classical forms of physiologyinvolved rather more quantification, mathematics andphysics than is palatable for manystudents. This is a pity,for careful measurement can often be more revealing thancursory examination. For example, digital imagingmicroscopyisroutinely used in all of the above disciplinesbutdetailed analysis of the already digitized data is rarelyperformed. Unfortunately,the massive amount of real datacontained in microscopic images is frequently ignored andimage processing applied to only “beautify” images ratherthan provide feature extraction and quantification. I cannothelp but wonder what Bernstein and Starling would havemade of this “science”.Measurement within newimaging methods has givenpowerful insight in to cell function. As an example, ourdiscovery and quantification of microscopic calciumsparks