Intracranial Pressure Monitoring
Calibration and Setup
Ashish V M
What is intracranial pressure?
Intracranial pressure (ICP)
is the pressure inside the
skull and thus in the brain
tissue and cerebrospinal
fluid (CSF).
Normal values: 7-15 mmHg
Abnormal values: > 20-25 mmHg
Increased ICP indicates Hydrocephalus and Edema
Measured during TBI (Traumatic brain injuries )&
Neurosurgeries.
Why Calibration…
To determine the functionality of the whole setup and to check
whether all the electronics being implemented onto the sensor
output is working or not, calibration of sensor is needed. The
sensor needs to be exposed to the pressure ranges from 0 to
50mm Hg in order to determine its sensitivity, hysteresis as well
as drift in the output voltage with time and pressure.
Need for a Pressure Calibrator:
• For stable temperature and pressure characterization of IISc
intracranial pressure sensor over a long period of time.
•To reproduce an in-vitro environment, this mimics the
conditions inside the brain.
ICP calibrator: Schematic Design
ICP calibrator
•Water bath assembly for temperature variation
•Vertical glass column for pressure variation
•Horizontal glass column with standard pressure sensor and multiple ICP
sensor insertion points
•Temp control and data recording through a PC
•Provision to calibrate 10 sensors at a time
Water Bath Assembly
•Water tank internal dimensions WxDxH (mm): 400 x 180 x 150
•Temperature range: 5 to 50 deg C
•Heater and compressor assembly
•PID temperature controller
•RS-232 interface for control and data readout
•Front viewing window, illuminated interior
Horizontal Glass Column :
•Square stainless steel tube (40 x 40 x 200mm) with a front glass window to
view the sensors’ position
•Glass window marked with mm scale
•Provision to insert 10 ICP sensors from top surface
•5 temp sensors (Pt1000) also placed to record the precise temp reading in
the proximity of ICP sensors
•1 standard pressure sensor for benchmarking and 1 temp sensor (Pt1000)
for temp control
Vertical Glass Column:
•Acrylic; Internal dia 10 mm; Height 1500 mm
•Detachable
•Marked with mm scale
•Zero coincides with the centre of the horizontal column
•Two solenoid switches for attaching pressure generator and pulse generator,
if required
•Valve to drain out the water
What has been done so far…
•Talks/discussions have been going on with a potential vendor regarding the
development of such a setup.
•Slight changes to the above model has been suggested by the vendor(For
instance, building the cooling assembly and display behind the horizontal tank
as opposed to the design in the image which suggests sideways)
•Meanwhile, the operation of the ICP monitoring and signal conditioning
device used by Kush Tripathi is being studied to see if it can be incorporated
into the setup.
Status as of today:
•Purchase order yet to be released as vendor needs more time to disclose new
quotations.
THANK YOU
Catheter(above)
Dimensions: 1 mm x 1 mm Square membrane
(400 um x 400 um) 200 um x 200 um
Aluminium pads
Plan for the
Fabricated Sensor
Off-chip circuit for electronic
interfacing(above). Pressure and
Temperature values are extracted
from the sensor by completing the
Wheatstone’s bridge using this
circuit.
Signal conditioning circuit(left)
Overview of the actual ICP monitoring system