Mebin progress

Notes on Using the ISS Imagent for Callibrated multi-distance

measurements

Imagent

The Instrument

While the ISS OxiplexTS is designed specifically for Calibrated Multi-distance Measurements; the Imagent can also be used for this purpose. However the Imagent is more flexible.

O X I P L E X T S

Instrument Setup

O X I P L E X T S

1. Setup

2. Check Instrument Function

3. Calibration

4. Measurement/Record

Imagent Setup

O X I P L E X T S

Attach all the cables.(See hardware manual and appendix 1 for USB systems)

Imagent Setup

O X I P L E X T S

Start the system• Turn on the computer (if a Magma docking station is

used, it should be powered first.)

• Insure detectors are off (or covered) Turn on instrument

• Start Boxy software

• “ Warm up ” system for 10-30 minutes

Imagent Setup

O X I P L E X T S

Start the system• Turn on the computer

• Insure detectors are off (or covered)

• Turn on Imagent system

• Start software

• “Warm up” system for 10 minutes

Imagent Setup

O X I P L E X T S

Select Sensor• Flexible or Rigid. The “rigid” muscle sensor is easier

to calibrate and more accurate. The “flexible” sensors can be used in places the rigid sensor will not work.(sensor must be continuous, even contact with the skin)

•Select longer emitter-detector distances for thick

superficial layers

Imagent Setup

O X I P L E X T S

Attach Sensor(s)1. Attach the detector bundle2. Attach source-fibers to both diodes of two

wavelengths.Most ISS sensors have 8 and 1 detector bundle, 4-source-detector distances 2-source-fibers at each distance (to support two wavelengths.

Detector Bundle

Source-Fiber locations

Source Fiber # 1,5 2,4 3,5 4,8

Imagent Setup

O X I P L E X T S

Possible fiber attachments depends on the switch-mode. There are multiple correct ways to attach the source fibers.

Rules:The 2 fibers connected to the same source-detector distance group must be connected to diodes of two wavelength. No two diodes can have the same external mux # (number/signal #). That is, two of the light source used with one sensor can not be on at the same time. The detector can only distinguish the signal form diodes not simultaneously on.

Imagent Setup

O X I P L E X T S

While there are multiple correct ways to attach the sensors, the softwaresetting must match and describe the physical attachment .

Example 1: (for switch-32 only)

O X I P L E X T S

Example 2: (works with any switch mode)

O X I P L E X T S

Attach Sensor To Calibration Block

Instrument/Sensor Check

• Start Data Acquisition (with sensor on cal. block).

• Adjust “Optimize The Detector Bias Voltage (Gain)

• All un-calibrated AC values associated with (“used”) source channels (diodes) should be within a factor of 2-4 times the smallest AC value.

• Using a1Hz overall measurement rate, the stdev(phase)should be <

0.15 degrees.

• Uncalibrated modulation ratio should be > 35%

Instrument/Sensor Check

Check (Correct) Software Settings• Open program settings file• Check\setup calibration block set properties.• Check\setup source\distance settings (must match fiber

connections).• Check\setup phase reference.• All the other settings




Check Instrument function PART2

Hold Sensor On Calibration Block

• Sensor must be flat against block.• Sensor may be held by hand, or with strap but … Be sure sensor is completely flat against block.• Only one sensor at a time! • Cover sensor with dark cloth to block bright room light• (not shown)

If using Flexible Sensor

• Select flat or curved surface to match sample.

• If using the flat surface of the block, remove block plastic cover.

• Use fingers to insure sensor makes contact at all point with the calibration block.

• Use of the strap to hold the sensor during calibration may allow the sensor to arch up in the middle, and not be in full contact with the block. This is particularly true when using the flat surface.

• Optical coupling gel may improve the accuracy of the calibration

Use Fingers to Hold Sensor Against Block. Press in Middle

No Strap on Flat

Careful with Strap on Curved Surface (also use fingers)


Finally, Run The Calibration Process In the Software use the “Calibrate for Optical Properties and Multiple Distances” option


USE OF “REAL TIME” CALCULATIONS:-- of best fit slopes, optical properties and hemoglobin concentration (“Real time” is an option, it can be done “offline” only.)

Optional Real Time Calculations

• Use program settings file suitable for real time multi-distance calculations. Or setup user calculations using your own math library (or ISS example math library bml_w2_c4.dll).

• Adjust user calculation parameters as desired.

• Insure weighting for all signals used is not 0 in the source\distance settings dialog.

• Use existing graph examples, or create desired graphs for real time display

With real time calculations we can perform more checks and examine data quality real time

1. Cross-Calibration Test

• After calibrating, place the sensor on a calibration block with different absorption and scattering values from the one that was used to calibrate the channel

• Optimize the detector gain (insure no overvoltage warnings).

• The instrument should now be measuring the properties of the second block within about +/-15% (for the most optimal configurations +/- 10%)

(Turn Detector Off During Transfer, and Whenever The Sensor Is Not Connected to a Subject or a Block)

With real time calculations we can perform more checks and examine data quality real time

2. Check Correlation Coefficient of the linear regression analysis

Measure / Record

Use Of Average Scattering

Optional Real Time Calculations

The following example settings are taken from the example program settings file

This is an example of using 4 multi-distanceISS two wavelength sensors with an Imagent in Switch-8 mode.

P L E A S E V I S I T U S W W W. I S S . C O M

Business

Mebin progress