XP Midterm Flashcards
What’s another term for SPATIAL QUALITY?
Geometric characteristics
What 3 factors must be correct to produce OPTIMUM CONTRAST?
Film type
Film processing
Exposure factors
Contrast is MEASURED and given a ____ value.
Numerical value
How is CONTRAST determined in FILM BASED IMAGING?
The difference between the OBJECT + BACKGROUND.
Ratio of brightness
“OBJECT : BACKGROUND”
How is CONTRAST determined in MAMMOGRAPHY?
A measured DENSITY LEVEL
DIGITAL IMAGE CONTRAST is obtained by
Proper digital processing
Adjustment of the display + window
What 2 compounds are used to ADD CONTRAST to low contrast objects in radiography?
Barium - high physical contrast
Iodine
*Good x-ray absorbers bc of ATOMIC # (size)
The source of MRI contrast is
Proton density
T1 LONGITUDINAL relaxation time
T2 TRANSVERSE relaxation time
Fluid movement
Do MRIs use x-rays?
Nope.
Uses the MAGNETIC field + radio frequency PULSES
NOISE ___ VISIBILITY of low contrast items.
Reduces
In NUCLEAR MEDICINE IMAGING, contrast depends on
Variation of radioactivity in a certain section of the body.
Differential uptake of the NUCLIDE + DISTRIBUTION …
What are associated with the differential uptake of the NUCLIDE + DISTRIBUTION?
the PHYSIOLOGICAL function
PATHOLOGICAL conditions.
ULTRASOUND PHYSICAL CONTRAST comes from
Echo made by differences in ACOUSTICAL IMPEDANCE of tissues
RBC movement
Define “Artifacts”
Objects that are NOT part of the patient, but are VISIBLE on the image
What is another term for “blur”?
Unsharpness
Projection imaging is ___ + ___
Radiography
Flouroscopy
Types of Tomographic Imaging
Tomography CT MRI PET SPECT Ultrasound
*produce slices
3D Imaging is COMPUTER BASED ___ + ___
CT
MRI
The amount of BLURRING is dependent upon
Blur characteristic of imaging modality
Selection of technique factors/protocol of procedure
____ CAMERA NUCLEAR MEDICINE produces the ____ NOISE.
Gamma Camera NM
Most noise
___ produces the LEAST NOISE.
Plain film radiography
Highest BLUR
Gamma camera nuclear medicine
Lowest BLUR
Mammography
Image noise + blur PRODUCE
“Curtain of invisibility”
“Window of invisibility”
Modalities with HIGH BLUR use ____ time to produce the image.
Longer
CT produces ___ or ___ of TISSUE information.
Voxels or
Cubes
The ability to detect an object generally INCREASES with
Background brightness
When VIEWER CONTRAST is LOW, what must the OBJECT have in order to be seen?
High SUBJECT contrast
Observer contrast sensitivity is effected by
Glare
Viewing distance
Object size
Background structure
MASKING extra light from around the IMAGE can
Improve visibility of DETAIL
Low contrast film (reduces/increases) NOISE?
Reduces
What is the main difference between DIGITAL and FILM RADIOGRAPHY?
Digital Imaging doesn’t have a DISTINCT or FIXED SENSITIVITY
What is “Image Integration” used for in FLUOROSCOPY?
To reduce noise
“Photon fluctuation” is dependent on
The photon concentration of exposure
What are the MAJOR FACTORS that affect “Radiographic receptor sensitivity”
Film sensitivity
Screen CONVERSION efficiency
Screen ABSORPTION efficiency
“Round Blur”
Intensifying screens of image intensifiers
“Square Blur”
Digital imaging
*Includes CT
“Elongation Blur”
Motion
“Focal Spot Blur”
Various patterns
What is the “Composite Modulation Transfer Function” used for?
To evaluate various components of an imaging system.
It’s a GRAPHICAL representation of the MODALITY BLUR.
In order for ENERGY to be useful in imaging, what does it need to do?
Must be able to penetrate the body.
What’s the relationship between ENERGY and WAVELENGTH?
They’re INVERSELY proportional
When is the chance of PHOTON ABSORPTION greatly enhanced?
If it encounters matter with ELECTRON ENERGY close to that of the PHOTON.
High energy ELECTROMAGNETIC RADIATION is measured in
Multiples of electron volts
The “Radio frequency” portion of the SPECTRUM is measured in
Frequency
What is a POSITRON needed for?
To annihilate an electron
Electrical circuits must contain a ___ & ___ connected by CONDUCTORS.
Source
Load
“Alternating current” in North America is
Cycles between POSITIVE and NEGATIVE flow
60 times per SECOND
Direct current flows in how many directions?
One
Uno
Un
1 coulomb = ___ mAs
1000
What 3 types of energy can ELECTRONS possess?
Kinetic energy
Potential energy
Rest mass
What is “Kinetic Energy”
Energy in motion
The ELECTRON is the ___ unit of mass.
Smallest unit
What’s the difference between the POTENTIAL ENERGY between 2 conductors?
The voltage
The AMOUNT of energy TRANSFERRED depends upon what 3 things?
Voltage
Current
Duration of transfer
Conventional “Roentgen R”
SI Units COULOMB/kg
SI Unit Gray
Convention RAD
SI Becquerel
Conventional Curie
**?
SI Sievert
Conventional REM
The “Surface Integral Exposure” (SIE) is another way of expressing
Total exposure to the body
The possible STOCHASTIC RISKS of cancer relate more to ____ as opposed to Fluoroscopy.
The Surface Integral Exposure
What is an alternate name for “Surface Integral Exposure”?
Exposure Area Product
Why is the “R” or “Roentgen” still used?
- It honors the physicist that discovered x-ray
- The units are CONVENIENT for MEDICAL imagining
- It’s the right SIZE for imaging techniques
“Photoelectric Interactions” happen most often when?
Competition of Photons
Photon energy > Electron binding energy
Slightly more
The probability of “Photoelectric Interactions” is dependent on what?
(Competition of Photons)
Atomic # of the material
“Compton Interactions” occur most often with
Competition of Photons
Electrons with LOW binding energy
What is the “Linear Energy Transfer”?
The rate at which ELECTRONS transfer energy
What is “Filtration”?
The SELECTIVE ATTENUATION of the photons according to their energy BEFORE entering the patient
In terms of “Forward Scatter Radiation”, the BEAM SIZE or AREA of EXPOSURE impacts what?
The AMOUNT of forward scatter
In terms of “Forward Scatter Radiation”, the BODY SECTION THICKNESS ____ the SIZE of what?
Increases the SIZE of the
SOURCE of scatter
In terms of “Forward Scatter Radiation”, scatter is MORE PENETRATING with (higher/lower) kVp.
Higher kVp
In terms of “Forward Scatter Radiation”, HIGHER kVp scatter contributes more to what?
The RADIATION penetrating the body
In terms of “Forward Scatter Radiation”, LOW kVp PHOTONS are absorbed/scatter at the ____ of the body and DOES NOT impact ____.
Surface of the body
Doesn’t impact FORWARD SCATTER
Photoelectric interactions occur with ___ BOUND ATOMS.
Tightly bound atoms
___ + ___ increase with INCREASED kVp.
Compton
Forward scatter radiation
Better scatter penetration happens when kVp is (increased/decreased)?
Increased
The average range of a group of PHOTONS is ____ related to the ATTENUATION RATE (filtration).
Inversely related
(Increasing/decreasing) the rate of attenuation by CHANGING PHOTON ENERGY or TYPE OF MATERIAL (increases/decreases) the average photon range.
Increasing the rate of attenuation
Decreases average photon range
The average photon range is EQUAL to
the “Reciprocal Attenuation Coefficient”
Average Photon Range
1/A.C.
“Beam Quality”
The beam’s ability to PENETRATE
Stop humping the laser.
What 2 things make each imaging method unique?
- Tissue characteristics visible in image
2. Viewing perspective
What 3 things do blur affect?
Anatomical detail
Sharpness of objects
Spatial resolution
