Intro Flashcards
Refers to imaging in which the energy source is outside the body
Transmission imaging
Refers to each point on the image corresponds to information along a straight line trajectory thru the patient
Projection imaging
Mammography system in which the xray tube (in some cases the detector) moves in an arc from approximately 7 to 40 degrees around the breast
Tomosynthesis
Tomography means
Picture (graph)
Slice (tomo)
MRI is approximately _____ times stronger than the earth’s magnetic field
10,000 to 60,000 times stronger
Nuclear medicine produces ______ images, because the radioisotopes emit their energy from inside the patient
Emission
2D maps of 3D radioisotope distribution and are helpful in evaluation of a large number of disorders
Planar nuclear images
Roentgen discovered xray in year
1895
Refers to continuous acquisition of a sequence of xray images over time, essentially a real time xray movie of a patient
Fluoroscopy
_____ energy xrays are used to reduce conspicuity of the ribs and other bones to permit better visualization of air spaces and soft tissue structures in the thorax
High energy xrays
Dark areas (high film optical density) correspond to ____ attenuation
Low
Bright areas (low film optical density) correspond to _____ attenuation
High
First imaging modality made possible by the computer
Computed tomography
Produced by passing xrays thru the body at a large number of angles, by rotating the xray tube around the body
CT
Modern CT scanners can acquire _____ mm-thick tomographic images along a ___ cm length of patient in ____ seconds
0.50 - 0.62 mm
50 cm
5 seconds
In MRI, proton has a magnetic moment, and when placed in a 1.5 T magnetic field, proton ______ (wobbles) about its axis, and preferentially absorbs radio wave energy at the resonance frequency of about ___ million cycles per second
Precesses
64 million
In MRI, Pulse of radio waves is generated by _____ positioned around the patient
Antennas/coils
By slightly changing the strength of the magnetic field as a function of position in the patient using magnetic field gradients, the proton resonancr frequency varies as a function of position, since frequency is _______ to magnetic field strength
Proportional
An area of MR data collection that allows for analysis of metabolic products in the tissue is _____, whereby a single voxel or multiple voxels may be analyzed using specialized MRI sequences
MR spectroscopy
Tomographic counterpart of nuclear medicine planar imaging
Single photon emission computed tomography
Positively charged electrons
Positrons
Similar to gamma rat emission, except that 2 photons are produced, and they are emitted simultaneously in almost exactly opposite directions
Annihilation radiation
Ultilizes rings of detectors that surround the patient, and has special circuitry that is capable of identifying the photon pairs produced during annihilation
Positron emission tomography
More sensitive to the presence of radioisotopes than SPECT cameras
PET detector system
Contrast in _____ imaging depends upon the tissues ability to concentrate the radioactive material
Nuclear imaging
Contrast in ____ imaging is related primarily to the proton density and to relaxation phenomena
MRI
Contrast in ______ imaging is largely determined by the acoustic properties of the tissues being imaged, the difference between acoustic impedances
Ultrasound
Imaging that shows the amplitude and direction of blood flow by analyzing the frequency shift in the reflected signal and thus motion is the source of contrast
Doppler ultrasound
Ability to see small detail
Spatial resolution
Size of the smallest object that an imaging system can resolve
Limiting spatial resolution
Highest resolution modality
Mammography
At 3.5 mHz, the wavelength of sound in soft tissue is about
500 um
At 10 Mhz, the wavelength is
150 um
Energy that travels thru space or matter
Radiation
No mass, unaffected by either electric or magnetic fields, and has a constant speed in a given medium. It does not require matter to propagate
Electromagnetic radiation
Interaction of EM radiation can occur by
Scattering
Absorption
Transformation
EM radiation is commonly characterized by
Wavelength, frequency, energy per photon
Emitted by the nuclei of radioactive atoms
Gamma rays
Produced outside the nuclei of atoms. Used in radiography, fluoroscopy and CT
Xrays
Produced when xrays or gamma rays interact with various scintillators in the detectors used in several imaging modalities and is also used to display images
Visible light
There are two correct ways pf describing EM radiation, as ____ and as discrete particle-like packers or quanta of energy called ______
Waves and photon
“Billiard-ball” type of collision between an xray photon and an orbital electron during a _______ scattering event
Compton
Xrays photon’s energy is completely absorbed by, and results in the ejection of an orbital electron (a photoelectron), in the _______ effect
Photoelectric effect
Intensity of the wave
Amplitude
Distance between any two identical points on adjacent cycles
Wavelength
Time required to complete one cycle of a wave
Period
Number of periods that occur per second is the
Frequency
Temporal shift of one wave with respect to the other
Phase
Because the speed of EM radiation is constant in a given medium, its frequency and wavelength are ______ proportional
Inversely
Wavelengths of xrays and gamma rays are typically measured in fractions of
Nanometers
Frequency is expressed in
Hertz (Hz)
Planck’s constant represents the
Energy of a photon
Energies of photons are commonly expressed in
Electron volts
Defined as the energy acquired by an electron as it traverses an electrical potential difference (voltage) of one volt in a vacuum
One electron volt
An atom or molecule that has lost or gained one or more electrons has a net electrical charge and is called
Ion
Photons of higher frequency than the far UV region of the spectrum (wavelengths greater than 200nm) have sufficient energy per photon to remove bound electrons from atomic shells, thereby producing ionized atoms and molecules. Radiation in this portion of the spectrum is called
Ionizing radiation
Minimum energies necessary to remove an electron
Ionization energy
Electrons emitted by the nuclei of radioactive atoms are referred to as
Beta particles
Negatively charge beta-minus particles or
Negatrons
Positively charge electrons, referred to as
Beta-plus particles or positrons
An uncharged nuclear particle that has a mass slightly greater than that of a proton. They are released by nuclear fission and are used for radionuclide production
Neutrons
Consists of 2 protons and 2 neutrons, it has +2 charge and is identical to the nucleus of a helium atom
Alpha particle
Emitted by many high atomic number radioactive elements such as uranium, thorium and radium
Alpha particles
The smallest division of an element in which the chemical identity of the element is maintained
Atom
The outer electron shell of an atom called _______, Determines the chemical properties of the element
Valence shell
Energy required to remove an orbital electron completely from the atom is called its
Orbital binding energy
Emissions from transitions exceeding ____ eV are called characteristic or fluorescent xray
100
An electron cascade does not always result in the production of a characteristic xray or xrays. A competing process that predominates in low Z elements is
Auger electron emision
The probability that the electron transition will result in the emission of a characteristic xray is called
Fluorescent yield
Number of protons in nucleus
Atomic number (Z)
Total number of protons and neutrons within the nucleus is the
Mass number (A)