medical image analysis medical imaging modalities: x-ray imaging figures come from the textbook:...
TRANSCRIPT
Medical Image AnalysisMedical Image AnalysisMedical Imaging Modalities: X-Ray Imaging
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Anatomical or structural◦X-ray radiology, X-ray mammography,
X-ray CT, ultrasound, Magnetic Resonance Imaging
Functional or metabolic◦Functional MRI, (Single Photon
Emission Computed Tomography) SPECT, (Positron Emission Tomography) PET, fluorescence imaging
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-ray ImagingX-ray Imaging
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure comes from the Wikipedia, www.wikipedia.org.
Conrad Roentgen◦Discovered X
rays in 1895◦Received the
Nobel Prize in 1901
Soft X rays◦Wavelengths from 10 nm to 0.1 nm,
corresponding to 120eV to 12.3 KeVHard X rays
◦Wavelengths shorter than 0.1 nm up to 0.001 nm
Diagnostic◦12.3 KeV to 123 KeV
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-Ray GenerationX-Ray GenerationPrinciple
◦An accelerated electron loses energy in interaction with an atom and the loss of energy emits X-ray photons in a scattered direction
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
39 P50N K
LO
N
Ejected Electron
Incident Electron
X-ray Photon
Figure 4.1. Atomic structure of a tungsten atom. An incident electron with energy greater than K-shell binding energy is shown interacting with a K-shell electron for the emission of an X-ray photon.
Tungsten◦K-shell binding energy level: 69.5 keV◦L-shell binding energy level: 10.2 keV◦An emission of X-ray photon of 59.3
keVX-ray generation
◦Electrons are released by the source cathode and are accelerated toward the target anode in a vacuum under the potential difference ranging from 20,000 to 150,000 volts
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure comes from the Wikipedia, www.wikipedia.org.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure comes from the Wikipedia, www.wikipedia.org.
Figure comes from the Wikipedia, www.wikipedia.org.
White radiationAlso called Bremsstrahlung
radiation spectrum
X-ray 2-D Projection X-ray 2-D Projection ImagingImagingDiagnostic radiology
◦2-D projection of the three-dimensional anatomical structure of the human body
◦Localized sum of attenuation coefficients of material: air, blood, tissue, bone
◦Film or 2-D array of detectorsDigital radiographic system
◦Use scintillation crystals optically coupled with photomultiplier
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-ray Source
X-ray ScreenFilmX-ray Screen
3-D Object orPatient
2-D ProjectionImage
Anti-scatter Grid
Figure 4.2. (a). A schematic diagram of a 2-D X-ray film-screen radiography system. A 2-D projection image of the 3-D object is shown at the bottom. (b). X-ray radiographic image of a normal male chest.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-ray 2-D Projection X-ray 2-D Projection ImagingImagingScattering
◦Create artifacts and artificial structures
Reduce scattering◦Anti-scattered grids and collimators
X-ray intensifying screen
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-ray MammographyX-ray MammographyTarget material
◦Molybdenum: K-, L-, M-shell binding energies levels are 20, 2.8, 0.5 keV. The characteristic X-ray radiation is around 17 keV.
◦Phodium: K-, L-, M-shell binding energies levels are 23, 3.4, 0.6 keV. The characteristic X-ray radiation is around 20 keV.
A small focal spot of the order of 0.1mm
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
X-ray Source
X-ray ScreenFilmX-ray Screen
CompressedBreast
MovingAnti-scatter Grid
CompressionDevice
Figure 4.3. A film-screen X-ray mammography imaging system.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure 4.4. X-ray film-screen mammography image of a normal breast.
X-ray Computed X-ray Computed TomographyTomography3-D
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
dxzyx
inout ezxyIzxyI),,(
),;(),;(
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure comes from the Wikipedia, www.wikipedia.org.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
y
x
zX-Y Slices
Figure 4.5. 3-D object representation as a stack of 2-D x-y slices.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
x
z
y
Iin(x; y,z)Iout(x; y,z)
(x,y; z)
11
22 92
15
12 42 52 62 72 82
Figure 4.6. Source-Detector pair based translation method to scan a selected 2-D slice of a 3-D object to give a projection along the y-direction.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure 4.7: The translate-rotate parallel-beam geometry of first generation CT scanners.
X-ray Computed X-ray Computed TomographyTomographyGenerations
◦First: an X-ray source-detector pair that was translated in parallel-beam geometry
◦Second: a fan-beam geometry with a divergent X-ray source and a linear array of detectors. Use translation to cover the object and rotation to obtain additional views
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Generations◦Third: a fan-beam geometry with a
divergent X-ray source and an arc of detectors. Without translation. Additional views are obtained by simultaneous rotation of the X-ray source and detector assembly. “Rotate only”
◦ Fourth: use a detector ring around the object. The X-ray source provides a divergent fan-beam of radiation to cover the object
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure 4.8. The first generation X-ray CT scanner
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Ring of Detectors
Source
SourceRotation Path
X-rays
Object
Figure 4.9. The fourth generation X-ray CT scanner geometry.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure 4.10. X-ray CT image of a selected slice of cardiac cavity of a cadaver.
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.
Figure 4.11. The pathological image of the selected slice shown with the X-ray CT image in Figure 4.10
Spiral X-ray CTSpiral X-ray CTSpiral CT
◦The patient bed is moved at a constant speed
◦The gantry is rotated within the circular opening
◦Provide the data along a spiral or helical path
◦Pitch: : slice thickness : the movement of bed one complete
ratation (360 degrees) of gantryt
dp
td
Contrast Agent, Spatial Contrast Agent, Spatial Resolution, and SNRResolution, and SNRContrast agent
◦Barium sulfate, to enhance contrast in upper gastrointestinal (GI) tract imaging
◦Barium atom has a K-edge at 37.4KeV◦Iodine-based, used in angiography,
urography, and intra-arterial DSA to improve visibility of arteries and blood vessels
◦Iodine has a K-edge at 33.2KeV
Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.