Upload
antonymuringathiriyil
View
274
Download
0
Embed Size (px)
Citation preview
Near infrared (NIR) brain imaging study: neurological responses in the pre-frontal area during
reading vs relaxing
ByAntony ThomasBejoy V MathaiNaveen Balaji
ACKNOWLEDGEMENTS
• We would like the thank Dr. Hanli Lui for providing us with this opportunity to do this hands on project and guiding us through, from beginning till the end.
• We are also thankful to Venkatagiri for his advise and guidance.
• We are very much thankful to Dr. Fenghua Tian, Manish and Sabin for teaching us the basics of the NIRx Instrument and helping us with the data collection.
Introduction• Functional Near Infrared Spectroscopy (fNIRS), is a non-
invasive imaging modality that allows to detect brain activity (or activation) through monitoring of blood oxygenation and blood volume in different region of brain.
• NIRS measures the attenuation of the biological tissue in near infrared spectrum. i.e., using longer wavelengths than those of visible light region that falls between 700 nm – 1000 nm.
• Other brain imaging techniques like MRI and PET are highly expensive, sensitive to motion artifacts, confines the subject to restricted position and expose the subject to harmful material (PET) and loud noise (MRI).
Absorption spectra for oxy and deoxy- haemoglobin
•700 to 900 nanometres is called a “window of transparency” because itallows light to propagate relatively deeply into the tissue before getting absorbed.
Ref:-INVESTIGATION OF BRAIN ACTIVITIES USING TWO STATE-OF-THE-ART DIFFUSE OPTICAL IMAGERS by SURESH PRAJAPATI
Ref:- www.nirx.net
•We are interested in prefrontal area
•This study is useful because it provides unique insights in the field of developmental neuroscience with a non-invasive approach.
Ref:-http://www.beliefnet.com
General block diagram
•Sensor- source and detector ( 760nm and 830nm).•Data acquisition unit.•Processor.
Ref:- International Journal of human-computer interaction, Brain imaging during cognitive task by Izzetoglu et.al
Probe Placement
Probe #1Probe # 20
Probe Arrangement
Protocol:
5 13791113151719
20 18 16 14 12 10 8 6 4 2
19 cms
3 cms
Relaxing20 sec
Reading 20 sec
Relaxing20 sec
•The reading material was based on general knowledge material based on general topics like geography, history, economics etc.
•The room was dark to reduce the interference of external light
Instrumentation
DYNOT System
Ref:- www.nirx.net
Figure: Shows the Front and Back view of the DYNOT System, with labels for various Components
PMD
Fiber optics cableLaser diode controller
Monitoring PC with Keyboard unit
Laser diode
Power supplyOptical Switch
Ref:- www.nirx.net
LD – Laser diode
LDD-Laser diode driver
TECD-Thermo-electric cooler driver
DPS- Digital Phase shifterf1&f2-Laser modulation frequencies
Optical time division multiplexer
Figure: Shows Block Diagram of DYNOT Instrument performing it’s function
Ref:- www.nirx.net
Figure: Shows how multiple optical tomographic data sets are acquired in a continuous fashion at high repetition rates (about several images per second)
Sample rate = 2.42 frames/second
LEGENDTarget
Target
Source
Detector
Direction of activation of source and detector around the target
Process of obtaining One tomographic data set
Ref:- www.nirx.net
Processing
• The raw optical data is processed in MATLAB to obtain the NIRS file.
• HOMER is used to process the NIRS file for Image Reconstruction.
• Images is reconstructed from the oxy and deoxy-hemoglobin using delta Concentration display .
• The spectrally weighted average of the wavelength specific forward models are used.
Raw Optical Data NIRS Data HMR DataImage Reconstruction (HBO , HBR & HBT obtained using delta Concentration)
Result:
Hemodynamic activity of HbOSubject 1 Subject 2 Subject 3
WhileRELAXING
WhileREADING
LeftRight Right Left
Left Left Left
LeftRight
RightRightRight
Hemodynamic activity of HbR
Subject 1 Subject 2 Subject 3
WhileRELAXING
WhileREADING
Right Left
RightRightRight
RightRight
LeftLeftLeft
LeftLeft
Block Averaged Hemodynamic responseSubject 1
dCon
cent
ratio
n (M
olar
)
Time (sec)
HbO
Hb
While RELAXING
While READING
Block Averaged Hemodynamic responseSubject 2
Time (sec)
dCon
cent
ratio
n (M
olar
)
HbO
Hb
While RELAXING
While READING
Block Averaged Hemodynamic responseSubject 3
dCon
cent
ratio
n (M
olar
)
Time (sec)
HbO
Hb
While RELAXING
While READING
Conclusion
• The rise in HbO activity shows the activation of neural activity in the pre frontal region while performing a cognitive task.
• Thus, fNIRS offers the possibility of directly investigating functional connectivity during rest and activation.
• For most language tasks the advantage of the left hemisphere (LH) is one of the best-established facts about the brain.
• Accumulated evidence shows the activity of bilateral components. When it comes to comprehending complex, natural language, the right hemisphere (RH) might play an important role.
Reference
• Prajapati, Suresh “INVESTIGATION OF BRAIN ACTIVITIES USING TWO STATE-OF-THE-ART DIFFUSE OPTICAL IMAGERS”.
• www.nirx.net • en.wikipedia.org• HomER Program User’s Guide Stand-alone executable
version (Version 4.0.0) Release July 28th, 2005
Written by: Theodore Huppert, M.Sc.
David A. Boas, Ph.D.
Thank you&
Questions