A method to detect certain regions in thermal images of human faces is presented. In this approach, the following steps are necessary to locate the periorbital and the nose regions: First, the face is segmented from the background by thresholding and morphological filtering. Subsequently, a search region within the face, around its center of mass, is evaluated. Automatically computed temperature thresholds are used per subject and image or image sequence to generate binary images, in which the periorbital regions are located by integral projections. Then, the located positions are used to approximate the nose position. It is possible to track features in the located regions. Therefore, these regions are interesting for different applications like human-machine interaction, biometrics and biomedical imaging. The method is easy to implement and does not rely on any training images or templates. Furthermore, the approach saves processing resources due to simple computations and restricted search regions.
Diagnosis of allergic immediate-type reactions is dependent on the visual assessment of the attending physician. With our novel non-obtrusive, camera-based photoplethysmography imaging (PPGI) setup, perfusion in the allergic testing area can be quantified and results displayed with spatial resolution in functional mappings. Thereby, each PPGI camera pixel can be assumed to be a classical (skin-based) reflective mode PPG sensor. An algorithm for post-processing of collected PPGI video sequences was developed to transfer black-and-white PPGI images into virtual 3D perfusion maps. For the first time, frequency selected perfusion quantification was assessed. For the presented evaluation, PPGI data from our clinical study were used . For this purpose, different concentrations of histamine dilutions were administered to 27 healthy volunteers. Our results show clear trends in an increase in heartbeat synchronous perfusion rhythms and, simultaneously, a decrease of lower frequency vasomotor rhythms in these areas. These results, published for the first time, allow new insight into the distribution of skin perfusion dynamics and demonstrate the intuitive clinical usability of the proposed system.
Photoplethysmography imaging (PPGI) and infrared thermography imaging (IRTI) are contactless camera-based measurement methods for monitoring a wide range of basic vital parameters. In particular, PPGI enhances the classical contact-based photoplethysmography. Approved evaluation algorithms of the well-established PPG method can easily be adapted for detection of heart rate, heart rate variability, respiration rate (RR), respiratory variability (RV), and vasomotional activity with PPGI. The IRTI method primarily records temperature distribution of the observed object, but information on RR and RV can also be derived from IRTI by analyzing the development of temperature distribution in the nasal region. The main advantages of both monitoring methods are unobtrusive data acquisition and the possibility of assessing spatial assignment between vital parameters and body region. Hence, these methods enable long-term monitoring or the monitoring of effects with special local characteristics. Because the two systems supplement each, a combined hybrid application is proposed and its feasibility discussed.