Polygraph

Periorbital thermal signal extraction and applications.
Shastri D, Tsiamyrtzis P, Pavlidis I. Computational Physiology Lab, University of Houston, Houston, TX

We propose a novel method that localizes the thermal footprint of the facial and ophthalmic arterial-venous complexes in the periorbital area. This footprint is used to extract the mean thermal signal over time (periorbital signal), which is a correlate of the blood supply to the ocular muscle. Previous work demonstrated that the periorbital signal is associated to autonomic responses and it changes significantly upon the onset of instantaneous stress. The present method enables accurate and consistent extraction of this signal. It aims to replace the heuristic segmentation approach that has been used in stress quantification thus far. Applications in computational psychology and particularly in deception detection are the first to benefit from this new technology. We tested the method on thermal videos of 39 subjects who faced stressful interrogation for a mock crime. The results show that the proposed approach has improved the deception classification success rate to 82%, which is 20% higher compared to the previous approach.

Facial thermography is a sensitive and specific method for assessing food challenge outcome.
Clark AT, Mangat JS, Tay SS, King Y, Monk CJ, White PA, Ewan PW. Department of Allergy, Cambridge University Hospitals NHS Trust, Addenbrookes Hospital, Cambridge, UK.

BACKGROUND: Oral challenge is widely used for diagnosing food allergy but variable interpretation of
subjective symptoms may cause error. Facial thermography was evaluated as a novel, objective and
sensitive indicator of challenge outcome.

METHODS: A total of 24 children with a history of egg allergy underwent oral challenge, which were scored positive when objective symptoms occurred or negative after all doses were consumed without reaction. Facial temperatures were recorded at baseline and 10-min intervals. The difference between mean and baseline temperature (DeltaT), maximum DeltaT during challenge (DeltaT(max)) and area under curve of DeltaT against time (DeltaTAUC) were calculated for predefined nasal, oral and forehead areas, and related to objective challenge outcome.

RESULTS: There were 13 positive and 11 negative challenges. Median nasal DeltaTAUC and DeltaT(max) were greater in positive compared with negative challenges (231- and 5-fold, respectively; P < 0.05). In positive challenges, nasal temperatures showed an early transient rise at 20 min, preceding objective symptoms at median 67 min. There was a sustained temperature increase from 60 min, which was reduced by antihistamines. A cut-off for nasal DeltaT(max) of 0.8 degrees C occurring within 20 min of the start of the challenge predicted outcome with 91% sensitivity (positive predictive value [PPV] 100%) and 100%
specificity (negative predictive value [NPV] 93%). Subjective symptoms occurred in four of 13 positive and
three of 11 negative challenges.

CONCLUSIONS: Facial thermography consistently detects a significant early rise in nasal temperature during positive compared with negative food challenges, which is evident before objective symptoms occur.
Thermography may therefore provide a sensitive method to determine outcome of food challenges and investigate the pathophysiology of food allergic reactions.

Intraoperative application of thermography in extracranial-intracranial bypass surgery.
Okada Y, Kawamata T, Kawashima A, Hori T Department of Neurosurgery, Tokyo Women's Medical University, Tokyo, Japan. yokada@nij.twmu.ac.jp

OBJECTIVE: The extracranial-intracranial bypass may have the potential to improve hemodynamic cerebral ischemia caused by occlusive diseases of the main cerebral arteries. Intraoperative confirmation of effective distribution of blood flow via the donor arteries to the involved region will assure a successful bypass surgery.
METHODS: Infrared thermography was used to measure the temperature of the cortical surface at the operative field. Regional cerebral blood flow (rCBF) was measured with a laser Doppler flow meter. Changes in the cortical surface temperature before and after temporary occlusion of the bypass were compared with changes in rCBF values in the corresponding sites.
RESULTS: Thermographic examination demonstrated a heterogeneous increase of cortical surface temperature caused by the blood flow via the extracranial-intracranial bypass and was closely related to rCBF changes.
CONCLUSION: Thermography is useful not only to demonstrate the distribution of blood flow through the extracranial-intracranial bypass but also to quantitatively evaluate the rCBF changes in the operative field.

Neurophysiological study of thin myelinated and unmyelinated fibers.
Espinosa ML, Santiago S, Guzman JJ, Prieto J, Ferrer T; Laboratorio de SNA, Hospital General
La Paz, Madrid, Espana.

INTRODUCTION: Standard neurophysiological techniques evaluate thick myelinated fibers. Yet,
peripheral nerves are equally composed of thin myelinated and unmyelinated fibers. The latter are
responsible for autonomic function as well as temperature and pain perception.

DEVELOPMENT:
Microneurographic studies are restricted to investigation laboratories. Since the techniques are complex
and invasive, their performance is still poor for clinical purposes and some of the components to be
analyzed, such as cardiovagal, cannot be directly recorded. The clinical need to evaluate the functions
regulated by the autonomic nervous system (ANS) had led to devising a series of tests which, in most
cases, rely on reflex responses evoked by already known standardize stimuli. The battery chosen has to
be non invasive, reproducible, specific, providing relevant data to the investigated function, with a readily
available technology, which has to be managed being aware of the physiological and pathological factors
that might bear an influence on the results. The recent development of heart rate blood pressure power
spectral analysis, provides a new interesting insight for quantification of ANS abnormalities. The study of
thermography and thermometry of body surface brings forward evidence on the activity of other thin and
unmyelinated fibers components of the peripheral nerve spectrum.

CONCLUSION: The adequate
management of the above mentioned tests gives rise to a more extensive and appropriate knowledge of
the whole peripheral nerve fiber spectrum.