Introduction to Medical Imaging
Medical images are usually displayed this way because image intensity represents a measured physical quantity rather than color.
What is monochrome/grayscale?
Radiation with sufficient energy to remove an electron from an atom belongs to this category.
What is ionizing radiation?
This image-quality property describes the ability to distinguish two closely spaced objects.
What is spatial resolution?
In this interaction, an x-ray photon changes direction without ionizing the atom and without losing appreciable energy.
What is Rayleigh scattering?
This x-ray tube component supplies electrons through thermionic emission.
What is the cathode/filament?
In this type of imaging, energy passes through the patient before being detected.
What is transmission imaging?
Alpha particles and beta particles are examples of this general class of radiation.
What is particulate radiation?
A narrow PSF generally corresponds to this type of spatial resolution.
What is better/higher spatial resolution?
In this interaction, the incident photon is completely absorbed and an electron is ejected from an atom.
What is the photoelectric effect?
These two major types of x-rays make up the useful x-ray tube spectrum.
What are Bremsstrahlung and characteristic x-rays?
In this type of imaging, the detected energy originates from within the patient.
What is emission imaging?
This quantity represents the energy required to remove an electron from its atomic shell.
What is electron binding energy?
At higher spatial frequencies, this quantity generally decreases in a real imaging system.
What is MTF?
This equation links photon energy and wavelength.
What is E = hc/lambda?
This effect causes x-ray intensity to vary across the field because photons traveling toward one side of the anode encounter more target material.
What is the heel effect?
This general imaging approach collapses information along the direction of propagation onto a two-dimensional image.
What is projection imaging?
Within a given atom, electrons in shells closer to the nucleus generally have this relationship to binding energy.
What is greater/higher binding energy?
The Nyquist criterion requires the sampling frequency to be at least this multiple of the highest spatial frequency in the image.
What is two times?
A photoelectric interaction occurs with a 70-keV photon and an electron having a 20-keV binding energy. What is the kinetic energy of the emitted electron?
What is 50 keV?
Reducing the x-ray field using a collimator primarily changes this property of the beam outside the desired field while leaving the central beam relatively unaffected.
What is fluence?
This term describes the difference in image intensity between an object and its surrounding background.
What is contrast?
An outer-shell electron drops into an inner-shell vacancy. The difference between the two shell binding energies determines this quantity.
What is the energy of the emitted characteristic x-ray?
An imaging system must accurately represent structures containing spatial frequencies as high as 4 line pairs/mm. What is the minimum sampling frequency?
What is 8 samples/mm?
This interaction is more closely related to electron density than atomic number and is an important source of scattered radiation in tissue.
What is Compton scattering?
A transformer has 500 primary turns and must increase 240 V to 120 kV. Approximately how many secondary turns are required?
What are 250,000 turns?