RADT 1085 Unit 1 Test Questions and Answers All Correct
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Course
RADT 1085
Institution
RADT 1085
RADT 1085 Unit 1 Test Questions and Answers All Correct
When increased OID is unavoidable, SID should be - Answer-increased slightly to compensate.
In Computed radiography - Resolving power determined by - Answer-PSP and scanning system frequency (sampling); the greater the frequency the gre...
RADT 1085 Unit 1 Test Questions
and Answers All Correct
When increased OID is unavoidable, SID should be - Answer-increased slightly to
compensate.
In Computed radiography - Resolving power determined by - Answer-PSP and scanning
system frequency (sampling); the greater the frequency the greater the resolution
In Direct radiography - Resolving power determined primarily by - Answer-the detector
element size (DEL), but detector system can influence too
- (Cesium Iodide/Amorphous Silicon vs. Amorphous Selenium)
Amorphous Selenium = better resolution (no light)
What is the purpose of tube filtration? - Answer-to absorb longwavelength photons
before they reach patient
How does tube filtration affect the x-ray beam? - Answer-filtration increases average
energy of the x-ray beam and reduces the dose to the patient by as much as 80%
Tube Filtration has the ability to ... - Answer-...alter beam intensity and alter IR
exposure.
• IR exposure decreases when tube filtration
is increased.
There is an _____ relationship between tissue thickness/type and image receptor
exposure. - Answer-inverse;
- Thick anatomic part decreases IR exposure.
- Thin anatomic part increases IR exposure.
pixel size is determined by - Answer-DEL size; smaller DEL size = smaller pixel pitch =
greater spatial resolution
Quantum Mottle (Noise) - Affects spatial resolution - Answer-when extremely low mAs is
used.
• CR & DR with low exposure index
• If exposure index is low, we must always check for quantum mottle.
- Low Signal to Noise Ratio (SNR) - Answer-Not enough signal (transmitted photons) to
over
take the inherent noise produced by the type of IR
magnification factor formula - Answer-MF = SID/SOD
, Image Size formula - Answer-image size = object size/MF
pixel size formula - Answer-pixel size = FOV/matrix size
Grid ration formula - Answer-Grid Ratio = height/distance between strips
Exposure maintenance formula - Answer-mAs1/mAs2 = D1 squared/D2 squared
- to maintain exposure when distance changes
- also called Direct Square Law
Radiographic distortion - Answer-The misrepresentation of the size or shape of a
structure recorded in the radiographic image.
• A geometric property affecting the radiographic quality.
• Geometric Integrity
2 types of distortion - Answer-size - influenced by OID and SID
shape - influenced by alignment of the CR, part or image receptor and angulation
degree and direction
Magnification - Answer-• Generally, decreases the spatial resolution of the image...
• However, it can be used to image very small structures • Must be used with a small
focal spot size
Exposure - Answer-the amount of radiation that reaches a particular area of the image
receptor
What is the primary controller of image receptor exposure? - Answer-mAs (intensity)
(mGy or mR) - As mAs increases, x-ray exposure increases (intensity) proportionally
Reciprocity law - Answer-Exposure at the IR should remain unchanged as long as
intensity and duration of xray exposure (controlled by mAs) remain unchanged
30% rule: - Answer-minimum change in mAs necessary to cause a significant change in
IR exposure.
As a General rule, make mAs changes ... - Answer-in doubles or halves
How does kVp influence receptor exposure? - Answer-alters intensity of the beam
reaching image receptor - higher kVp levels produce
higher-energy photons that will pass more easily through the body
As kVp increases, the number of primary photons does too,
why? - Answer-because tube current's kinetic energy is more efficiently converted into
x-rays
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