Phase Contract Mra by rst60617

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									The University of Louisville                      CVIP Lab

      Medical Image Processing
                   M. Sabry Hassouna
                         Ph.D.
        Computer Vision & Image Processing Laboratory (CVIP)
                         Louisville, Kentucky
               Medical Imaging
The study of medical imaging is concerned with

  Interaction of all forms of radiation with tissue.

 The development of appropriate technology to
 extract clinically useful information, usually in
 the form of an image from the observed
 technology.
                             X-Ray
Image Formation
   A beam of X-rays is directed through a patient onto a film.
   The film provides a measure of the ray attenuation in tissue.
Nov 8, 1895
Wilhelm Konrad Röntgen
reported discovery of new “rays”
(Nobel Prize in physics in 1901).

Jan 13, 1896
First clinical use of X-rays by 2
British doctors to find a needle
in a hand.

+ Excellent for imaging bones.
- No depth information, bad for soft tissue, excessive radiation
Sample X-Ray Slices
           Computed Tomography (CT)
Image Formation
The object is viewed from a number of different angles and then a cross-
sectional image of it can be computed (reconstructed).

Nov 8, 1895
G. Hounsfield (computer expert)
and A.M Cormack (physicist)
(Nobel Prize in Medicine in 1979).

+ Provide 3D anatomical information
+ Preserves topology (bones)
- Excessive radiation
- Not good for all soft tissues
Sample CT Slices
        CT Acquisition Techniques




 slice-by-slice scanning




Spiral (volume) scanning
        (Very Fast)        3D Reconstruction
      Magnetic Resonance Imaging (MRI)
 Image Formation
 - Hydrogen nuclei (protons) under a strong magnetic field spin
  in phase with one another and align with the field.
- Relaxed protons induce a measurable radio signal.
1952
F. Bloch and E. Purcel, extended by R. Ernst)
(Bloch & Purcel: Nobel Prize in Physics in 1952)
(Ernst: Nobel Prize in Chemistry in 1991)

+ Main modality for image guided surgery.
+ Superb ability to discriminate between
  subtle differences in tissue characteristics.
+ Very safe.
- Less accurate for bone scanning.
Sample MRI Slices
                        Ultrasound (US)
Image Formation
An ultrasonic energy is propagated into the patient from a
transducer placed on the skin and back-scattered echo signal is
recorded by the same transducer.

1979: Samuel H. Maslak
+ Noninvasive
+ Clean & safe
+ In-expensive
- Noisy
- Gas filled and bony structures cannot be imaged
  because they absorb ultrasound waves.
     Positron Emission Tomography (PET)
 Image Formation
 - Detection of radiation from the emission of positrons.
 1998-2001:
 Dr. David Townsend and Dr. Ron Nutt.




+ Valuable technique for some diseases
   and disorders.
+ Amount of radiation is small
- Invasive (inject radioactive material)
Magnetic Resonance Angiography (MRA)
Image Formation
Imaging the blood vessels (moving spins) using MRI scanner.

   TOF (time-of-flight)
   PCA (phase contract angiography)
   (CEA) (contrast enhanced angiography)
   (CTA) (computer tomography angiography)
   (DSA) (digital subtraction angiography)




     DSA              CTA                     TOF
Medical Image Processing
                    Data Processing
1. Preprocessing
  Filtering, registration
2. Detection
  Finding objects (nodules, polyps, organs)
3. Segmentation
  Exact delimitation of objects
4. Analysis
  Measurement (volume, curvature)
5. Classification/diagnoses
           Preprocessing
Original                   Enhanced
                        Detection
Find location of objects of interest without prior knowledge
about their location/existence

• Bones
• Organs
• Polyps in colon
• Nodules in lungs
                     Segmentation
Exactly delimitate objects, once they are detected.

- Vessels
- Liver
- Cardiac imaging (left ventricle)
- Brain
                       Analysis
• Measurement
 Volume - growth
 Vessel stenosis

• Functional imaging
 Stroke
 Cardiac perfusion
 Tumor perfusion

• Cardiac function
 LV motion
 Injection fraction
      Classification / Diagnoses
• Comparison to developed atlases
• Use of knowledge databases
• Classify as normal/abnormal (brain)
• Classify lung nodules as benign/malignant
• Determine cancer/non-cancer

								
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