During the past decade, thermographic cameras with high thermal and temporal resolution of up to 30 mK and 50 Hz,
respectively, have been developed. These camera systems can be used to reveal thermal variations and heterogeneities of
tissue and blood. Thus, they provide a fast, sensitive, noninvasive, and label-free application to investigate blood
perfusion and to detect perfusion disorders. Therefore, time-resolved thermography is evaluated and tested for
intraoperative imaging of the cerebral cortex during neurosurgeries.
The motivation of this study is the intraoperative evaluation of the cortical perfusion by observing the temporal
temperature curve of the cortex during and after the intravenous application of a cold bolus. The temperature curve
caused by a cold bolus is influenced by thermodilution, depending on the temperature difference to the patient’s
circulation, and the pattern of mixing with the patient’s blood.
In this initial study, a flow phantom was used in order to determine the temperature variations of cold boli under stable
conditions in a vascular system. The typical temperature profile of cold water passing by can be approximated by a bi-
Gaussian function involving a set of four parameters. These parameters can be used to assess the cold bolus, since they
provide information about its intensity, duration and arrival time. The findings of the flow phantom can be applied to
thermographic measurements of the human cortex. The results demonstrate that time-resolved thermographic imaging is
a suitable method to detect cold boli not only at a flow phantom but also at the human cortex.