Medoc PATHWAY - 2 Overview; CHEPS Thermode; ATS Thermode

Pathway Technical Reference Manual
Proprietary 29 of 190
2. Overview
The PATHWAY Pain & Sensory Evaluation System is an advanced, computerized thermal
stimulator designed for advanced neurological and pain research. The PATHWAY System is
available in six main configurations, as it is a completely modular system with easy upgrade
capabilities. The PATHWAY system offers a specially designed software program, which can be
integrated with research programs such as “LabView” and “MatLab”, for controlling PATHWAY
stimulation protocols. PATHWAY system also allows synchronization with external devices such
as fMRI and EEG systems.
The PATHWAY system uses two types of active devices named Thermodes: a CHEPS (Contact
Heat Evoked Potential) Thermode and an ATS (Advanced Thermal Stimulator) Thermode.
These devices are attached to the skin of the tested subject for stimulation delivery. Both
Thermodes include the following components:
 Thermistors: Components that sense changes in temperature and send feedback to
the control unit. In response to the required temperature parameter, the
temperature control unit commands the heating or cooling of the Thermode.
 Peltier elements: Components that consist of semiconductor junctions, which
produce a temperature gradient between the upper and lower stimulator surfaces
produced by the passage of an electric current. The Peltier element emanates heat
from its upper surface, produced by the external foil. The lower surface of the Peltier
element is cooled by a coolant that circulates via flexible tubes to the External
Cooling Unit.
The unique characteristics of each of the two Thermode types are brought in details
hereunder:
2.1 CHEPS Thermode
 The CHEPS (Contact Heat Evoked Potentials)Thermode is comprised of two layers of
stimulators working together:
o An external layer, which consists of a heating foil that has two thermocouples
(electronic thermal sensors).
o A lower layer, which is a Peltier element with one thermistor (electronic thermal
sensors), and one water thermistor.
 The CHEPS Thermode external foil is isolated from the skin of the subject by an
electrically isolated plastic layer (Kapton
®
).
 The CHEPS Thermode can reach a very rapid heating rate of 70C/Sec. This effect is
enabled by the external foil.
 The CHEPS Thermode Achieves a rapid cooling rate of up to 40C/Sec, which is
enabled by the Peltier element.
 Sophisticated hardware and software control the counter balance or thermal (heat/
cool) integration at a rate of 200 times per second.
 The round activation area of the contact Thermode is 573 mm
2
(27 mm in diameter).
 Stimulation temperature range is 30C to 55C. Stimulation range can be widened,
by installing the Cold EP patch. See section 13 page 140.
2.2 ATS Thermode
 The ATS (Advanced Thermal Stimulator) Thermode is comprised of one stimulator
layer, which is constructed of a Peltier element with two thermistors (electronic
thermal sensors) and one water thermistor. The Surface contacting skin of subjects
is aluminum coated, for the purpose of heat dispersion.
 This device is capable of delivering heat or cold stimulations.
 The heating-up rate can reach 8C/Sec.