Medical Image Analysis Medical Imaging Modalities XRay Imaging

Medical Image Analysis Medical 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, Xray 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 Imaging Conrad Roentgen ◦ Discovered X rays in 1895 ◦ Received the Nobel Prize in 1901 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.

Soft X rays ◦ Wavelengths from 10 nm to 0. 1 nm, corresponding to 120 e. V to 12. 3 Ke. V Hard X rays ◦ Wavelengths shorter than 0. 1 nm up to 0. 001 nm Diagnostic ◦ 12. 3 Ke. V to 123 Ke. V Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

X-Ray Generation Principle ◦ 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.

Ejected Electron 39 P 50 N K L N O X-ray Photon Incident Electron 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. Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

Tungsten ◦ K-shell binding energy level: 69. 5 ke. V ◦ L-shell binding energy level: 10. 2 ke. V ◦ An emission of X-ray photon of 59. 3 ke. V X-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.

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. Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

White radiation Also called Bremsstrahlung radiation spectrum Figure comes from the Wikipedia, www. wikipedia. org.

An X-rat generation tube with rotating anode Figure comes from the Wikipedia, www. wikipedia. org.

Figure comes from the Wikipedia, www. wikipedia. org.

X-ray 2 -D Projection Imaging Diagnostic 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 detectors Digital 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.

X-ray Source 3 -D Object or Patient Anti-scatter Grid X-ray Screen Film X-ray Screen 2 -D Projection Image 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.

Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

X-ray 2 -D Projection Imaging Scattering ◦ 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 Mammography Target material ◦ Molybdenum: K-, L-, M-shell binding energies levels are 20, 2. 8, 0. 5 ke. V. The characteristic X-ray radiation is around 17 ke. V. ◦ Phodium: K-, L-, M-shell binding energies levels are 23, 3. 4, 0. 6 ke. V. The characteristic X-ray radiation is around 20 ke. V. A small focal spot of the order of Figures come from the textbook: Medical Image Analysis, Second 0. 1 mm Edition, by Atam P. Dhawan, IEEE Press, 2011.

X-ray Source Compression Device Compressed Breast Moving Anti-scatter Grid X-ray Screen Film X-ray Screen 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. Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

Normal (left) versus cancerous (right) Figure comes from the Wikipedia, www. wikipedia. org.

X-ray Computed Tomography 3 -D 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 z X-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.

y x m(x, y; z) m 15 z m 12 Iin(x; y, z) m 22 m 42 m 52 m 62 m 72 m 82 m 92 Iout(x; y, z) m 11 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. Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

X-ray Computed Tomography Generations ◦ 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.

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 Rotation Path Source 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 Xray CT image in Figure 4. 10 Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.

Spiral X-ray CT Spiral 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 gantry

Contrast Agent, Spatial Resolution, and SNR Contrast agent ◦ Barium sulfate, to enhance contrast in upper gastrointestinal (GI) tract imaging ◦ Barium atom has a K-edge at 37. 4 Ke. V ◦ 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. 2 Ke. V Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, 2011.