CT/OCT Scans of the Brain

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CT/OCT Scans of the Brain Powered By Docstoc
					CT/OCT Scans of the
     Brain
  Manish Padhiar, Sheetal Shukla
         Outline for Presentation
•   What is a CT scanner?
•   How does a CT scanner work?
•   What are CT scans used for?
•   What is the CT scanner used for?
•   How is a CT scan prepared for?
•   How is CT scan carried out?
•   Does a CT scan hurt?
•   Is a CT scan dangerous?
•   How is a CT scan read?
•   Applications to the Brain
CT scans
    • Computerized
      tomography (CT)
      scanners are a special
      kind of X-ray machine.
    • Several beams are sent
      out from different
      angles.
    • More detailed than
      regular X-rays.
   How does a CT scanner work?



• The strength of the X-ray beams passing through the body is
  measured.
• Stronger beams are those that pass through less dense tissue
  (lungs).
• Weaker beams are those that pass through more dense tissue
  (bone).
• Computer makes cross-section of body using relative densities of
  the tissues examined.
• Displayed as a 2-D picture on computer screen.
   How does a CT scanner work?




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• An x-ray beam is passed through a thin slice of the
  body and is recognized by detectors when it emerges.
• The beam is rotated around the subject, until all angles
  have been covered. Then the next slice is surveyed.
How does a CT scanner work?
     What are CT scans used for?
• 3-D images can be created
  using more modern CT
  scanners, which can lead to
  virtual images for surgeons
  during an operation.
• Doctors can now assess the
  inside of the body without
  performing surgery or
  examinations.
• Very helpful in pinpointing
  tumors and planning
  radiotherapy treatment
  schedules.
What is the CT scanner used for?
• Initially, CT scanner was made to picture the brain, but
  now can picture any part of the body.
• Extremely good at testing for internal bleeding in the
  brain, brain tumors, brain damage, and aneurysms,
  condition in which the wall of an artery swells up.
   – CT scans help the doctor identify the exact location of the
     tumor.
   – Then, a computer helps the doctor regulate the dose of
     radiation.
• Used to examine internal injuries without surgery, like a
  torn kidney, spleen or liver; or a spinal injury.
• Can be used to guide biopsies.
Body Scans
     • Spiral CT scanning is the new
       technology that medical
       professionals use to assess
       their patients.
     • The "full body" scan is used
       to recognize early signs of
       cancer in the lungs, kidneys,
       liver and colon.
     • The advantage is that trouble
       spots are detected earlier that
       they would have been.
     • Medical professionals still
       insist on regular screening
       through physical exams.
  How is a CT scan prepared for?
• For abdomen scan, the
  patient cannot eat 6 hrs prior
  to the scan. Gastrografin, an
  X-ray dye that makes the
  intestines easier to see, will
  be given 45 minutes before
  the scan.
• Sometimes a liquid X-ray dye
  is injected into the veins,
  which makes it easier to see
  blood vessels, and therefore
  tumors.
   How is CT scan carried out?
• Scanner looks like a large donut.
• Patient lies on a bed, which then moves
  backwards and forwards to allow the scanner to
  take the necessary pictures. It never touches the
  patient.
• Length of the test depends on the number of
  pictures that need to be taken and the different
  angles that are needed.
A CT Scanner
How is CT scan carried out?
            Does a CT scan hurt?
 • No, it does not hurt although people might find it
   slightly uncomfortable to lie on the bed for so long,
   especially if they are claustrophobic.
 • The machine makes a whirring noise.

         Is a CT scan dangerous?
• There are more X-rays involved in a CT scan, so without
  adequate medical reason, doctors don’t recommend it.
• Allergic reactions might result from the liquid dye injected.
• In certain people, the dye might cause damage to already weak
  kidneys.
          How is a CT scan read?




• Types of tissue in the body can be distinguished using a CT scan
  (muscle vs. fatty tissue).
• For an abdomen scan, the separate organs can be differentiated
  (pancreas, spleen, liver).
• For a lung scan, small shadows might signify lung cancer.
• For a brain scan, the areas that contain the liquid dye signify the
  ventricles, which are clearly shown.
    Common Uses of CT Scans
 Detection of bleeding, brain damage and
  skull fractures in patients with head injuries.
 Perfusion CT:
   Quantitative flow assessment.
   Noninvasive and can be performed in an
    emergency setting.
   Good for acute stroke patients, and patients
    with chronic steno-occlusive vascular disease.
Future Developments…
       Future Developments…
• CT imaging of the heart and coronary arteries to
  screen for heart disease very early.
• Emergency room CT scanning to assist in
  diagnosis of trauma patients.
• Blood flow imaging for stroke detection.
• 3D and virtual-reality imaging of the colon and
  lung interiors.
           Same Basic Questions
•   What is a OCT scanner?
•   How does a OCT scanner work?
•   What are OCT scans used for?
•   What is the OCT scanner used for?
•   How is a OCT scan read?
•   How is a OCT scan prepared for?
•   How is OCT scan carried out?
•   Does a OCT scan hurt?
•   Is a OCT scan dangerous?
•   Applications to the Brain
 Optical Coherence Tomography
                              • Optical Coherence
                                 Tomography (OCT)
                                 scanners are a new
                                 noninvasive, subsurface
                                 imaging of biological
                                 tissue microstructure
                                 with micron-scale (1~10
                                 μm) resolution (in vivo!!!).
• Like Ultrasound, it bounces waves off of a sample and
  extracts imaging data from reflected signals. Ultrasound
  uses acoustic pulses, whereas OCT uses light. [More
  detailed than Ultrasound or MRI]
How does a OCT scanner work?
 How does a OCT scanner work?
• Light (830 nm-1300 nm) is used to illuminate a
  Michelson interferometer.
• In the interferometer, light from the source is divided
  by a beamsplitter into sample and reference arms.
• Light retro-reflected from the sample and reference
  arms is recombined by the same beamsplitter and
  directed into an optical detector.
• Depth information (noting the fringe pattern) of the
  sample is converted to a cross sectional image by
  application of mathematical algorithms.
 How does a OCT scanner work?
• Short pulses of light are very expensive – therefore use
  coherence length-from a superluminescent diode
  (SLD).
• NOTE: short coherence length – interference only
  when path lengths of the two retro-reflected lights
  match within the coherence length.
 How does a OCT scanner work?
• Low coherence light source “has the potential to
  produce interference fringes when integrated
  with light from the same source that has traveled
  the same distance”
• DOUBLE SLIT DIFFRACTION PRINCIPLE!
• ULTRASOUND!
How does a OCT scanner work?
How does a OCT scanner work?
  What are OCT scans used for?
• 3-D images can be created using more modern
  OCT scanners, which can lead to virtual images
  for doctors to use for study of tissue-diseases.
• Doctors can now assess the inside of the body
  without performing surgery or examinations!!
  (histology)
• Very engaged in retinal scanning-we’ll get to the
  brain.
 What is the OCT scanner used for?
• It can replace/supplement standard histology
  approaches with imaging techniques.
• Initially, OCT scanner was made to picture the
  eye, but now researching is beginning
  concerning all types of tissue-“optical biopsy”!
• Advances in fiber optics = small
  catheter/endoscopes = in-vivo imaging.
How is a OCT scan read?
How is a OCT scan read?


                  A-SCAN:
                  longitudinal
                  (2-D depth)




                   B-SCAN:
                   transverse
                   (3-D)
NOTE: Resolution!
                         NOTE: Resolution!
  •   Resolution (log)
        a



 1 mm                                                  Standard
                                                       clinical
                                       Ultrasound
                         High
100 mm                   frequency


10 mm
                               OCT

 1 mm

                                                    Penetration depth (log)


                                1 mm        1 cm           10 cm
 What is the OCT scanner used for?
• Usually retinal
  scans:
What is the OCT scanner used for?
How is a OCT scan prepared for?
• No preparations needed-not for exo-imaging.



  How is OCT scan carried out?
• Traditionally, with the longitudinal and
  transverse paths. New endoscopes call for
  swallowing the a pill-like endoscope-in vivo
  imaging.
How is OCT scan carried out?




  NOTE: Images are take at or near real-time!!!
        Does a OCT scan hurt?
• No.

     Is a OCT scan dangerous?
• No.
• OCT uses light in the infrared part of the EM
  spectrum-little absorption by blood and tissue.

        How is a OCT scan read?
• Types of cells in a tissue section can be
  distinguished using a OCT scan.
      Applications to the Brain
NOTE: Optical contrast is often the limiting factor in the imaging
of live biological tissue.
         Applications to the Brain
• Journal of Biomedical Optics 105, 051603 September/October
  2005
• “Optical coherence tomography in the diagnosis and
  treatment of neurological disorders” – Jafri
• Studies were conducted in postmortem human brain to identify
  clinical applications- look for high-resolution images for
  myelinated fiber tracts and blood vessels.
• To improve the efficacy and safety of a neurosurgical procedure
  to treat Parkinson’s disease called deep brain stimulation DBS.
• 25 brains studied: The results suggest that catheterbased OCT
  has the resolution and contrast necessary for DBS targeting. The
  results also demonstrate the ability of OCT to detect blood
  vessels with high sensitivity, suggesting a possible means to avoid
  their laceration during DBS.
• Other microscopic structures in the human brain with high
  optical contrast are pathological vacuoles-include diseases such
  as Mad Cow disease and Creutzfeldt-Jakob disease.
Applications to the Brain
Applications to the Brain
        Applications to the Brain
• “Functional optical coherence tomography of
  neurophysiology” – Boppart
• Limitations in recording techniques for neurophysiology
  and neural networks-single point recordings with
  micropipette electrodes.
• Functional optical coherence tomography (fOCT) detects
  optical changes in cells and tissue during physiological
  events, such as electrical excitation (action potentials!!!).
       Applications to the Brain
• Imaged nerve
  fibers from the
  abdominal
  ganglion of the
  sea slug Aplysia
  californica.
         Applications to the Brain
• Figure shows a sequence of averaged fOCT images obtained
  before, during, and after stimulation, parts A, B, C respectively.
• B shows localized regions of increased scattering during
  stimulation, which subside after stimulation as the cells began to
  repolarize (C).
• D shows a plot of the total pixel intensity over the time-course
  of this experiment.
• The optical scattering changes observed with fOCT are
  consistent with earlier findings that light scattering from nerve
  fibers increases in response to electrical stimulation.
Applications to the Brain
                  Conclusion
•   Ophthalmology - clinical impact realized
•   Cardiology - clinical impact
•   Dermatology - clinical potential
•   Neurology - clinical potential

				
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