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, 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 Imaging Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, Figure comes from the Wikipedia, 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 KeV Hard X rays ◦ Wavelengths shorter than 0.1 nm up to 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 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.

39 P 50N K L O 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 keV 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,

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

Figure comes from the Wikipedia, White radiation Also called Bremsstrahlung radiation spectrum

An X-rat generation tube with rotating anode Figure comes from the Wikipedia,

Figure comes from the Wikipedia,

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 X-ray Screen Film X-ray Screen 3-D Object or Patient 2-D Projection Image 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 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 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.

X-ray Source X-ray Screen Film X-ray Screen Compressed Breast Moving Anti-scatter Grid Compression Device 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, Figure 4.4. X-ray film-screen mammography image of a normal breast.

Normal (left) versus cancerous (right) Figure comes from the Wikipedia,

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,

Figures come from the textbook: Medical Image Analysis, Second Edition, by Atam P. Dhawan, IEEE Press, y x z X-Y Slices Figure 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, x z y I in (x; y,z) I out (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, Figure 4.7: The translate-rotate parallel-beam geometry of first generation CT scanners.

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, Ring of Detectors Source Rotation 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, Figure 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, Figure The pathological image of the selected slice shown with the X- ray CT image in Figure 4.10

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 37.4KeV ◦ 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.