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RDTC 118 Unit 5

Scatter Control, IR

WTF is this?No Shit Sherlock
Scatter is a result of __ Interactions? Compton
↑ Tissue Volume = __ Scatter
Factors of Scatter PRODUCTION kVp & Tissue Volume
Tissue Volume includes __ & __ Part Thickness & Field Size
__ is the natural Cone Shaped border of the Primary Beam? Unrestricted Beam
Another term for Collimation Beam Restricting Device
↑ Collimation = __ Tissue Irradiated = __ Scatter ↑ Collimation = ↓ Tissue Irradiated = ↓ Scatter
What change in mAs for SIGNIFICANT Collimation? +30-50% mAs
Another term for Automatic Collimation PBL - Positive Beam Limiting Device
Simplest beam restriction device? Aperture Diaphragm
Aperture Diaphragms have a flat piece of lead (diaphragm/aperture) with a hole or (diaphragm/aperture)? Diaphragm, Aperture
Disadvantages of Aperture Diaphragm Unadjustable & Proximity to focal spot causes Unsharpness around image
When were Grids invented by whom? 1913 - Gustav Bucky
Most effective way to LIMIT Scatter reaching IR? Grids
Grids control Scatter Production (T/F)? False - No Impact PRODUCTION
Expresses the # of lead lines per unit length? Grid Frequency
Grid Frequency Value Range 25-45 lines/cm (60-110 lines/inch)
Ratio of Height of lead strips to Distance btwn? Grid Ratio
Grid Ratio Formula Grid Ratio = Height/Distance
Higher Grid Ratios decrease Scatter & need LOWER mAs (T/F)? False - ↓ Quantity=↑ mAs
__ Grid Patterns can be Parallel or Focused & allow for CR Angulation? Linear Grid
__ Grid Patterns are more efficient but do not allow for CR Angulation? Crossed (cross-hatched) Grid
__ Linear Grid Focus types are commonly used in mobiles & fluoro? Parallel Grids
Which type of Linear Grid Focus allows more Transmitted photons to IR? Focused Grids
__ is the intersection of imaginary lines from the lead strip(s) of a Focused Grid? Convergent Point (Convergent Line)
__ is the recommended range of SIDs for a Focused Grid? Focal Range
__ is the distance btwn the grid & Convergent line/point? Focal Distance
Both Parallel & Focused Grids have Focal Ranges (T/F)? False - Focused Grids only
Types of Stationary Grids Wafer, Grid Cassette, Grid Cap
How do Buckys move? Why? Lateral movement to Blur LEAD Lines from image
Long & Short Dimension Grids have lead strips running in relation to __ of the grid? Axis (Long or Short)
Grid Conversion Formula mAs1/mAs2=GCF1/GCF2
Grid decisions must balance image __ with patient __ ? Quality, Protection
Grid cutoff is more likely with LOWER Grid Ratios (T/F)? False - Higher
This type of Grid Cutoff has grid lines going opposite the angle of divergence? Upside-Down
Grid Cutoff errors that show an OVERALL decrease in IR exposure? Off Level & Off Centering
This type of Grid Cutoff is caused by a misalignment (off angle) of the Tube or IR? Off Level Grid
Most common type of Grid Cutoff? (example) Off Level (Ports)
This type of Grid Cutoff occurs when the central beam is not aligned with the Grid? Off Centering
This type of Grid Cutoff is from using an SID outside the recommended Focal Range, which misaligns the Divergence? Off Focus
Grid Cutoff errors that show decreased IR exposure on the LATERAL Edges? Upside-Down & Off Focus
Typical Grid Pattern? Typical Grid Focus? Typical Grid Ratio? Typical Focal Range? Linear, Focused, 8:1-12:1, 40"-72"
10" Air Gap is comparable to __ Scatter clean up? 15:1
How often should unused CR cassettes be erased? 48 hrs
__ Uses an IP that contains a PSP? CR
Large phosphor crystals provide higher resolution (T/F)? False - Smaller
CR Latent Image is stored in the __ as __? PSP as Trapped Electrons
__ Crystals are naturally harvested and randomly distributed throughout the phosphor layer? Turbid Phosphor
__ Crystals are manmade for uniform size and shape to provide less light divergence & better Recorded Detail? Needle (Columnar)
Which PSP Crystals are made of Cesium Iodide? Needle
Steps of Latent Image Formation with CR 1-PSP crystals absorb income xray energy. 2-Excited electrons move from resting in VALANCE Band to high energy CONDUCTIVE Band. 3-Migrating electrons caught in F Trap create Latent Image
What creates the Latent Image with CR? Electrons held in F-Trap of PSP
3 Steps to convert Analog to Digital Image? Scanning, Sampling, Quanization
__ is the receptor's ability to respond to different exposure levels? Dynamic Range
Film Screen receptors have a greater dynamic range than digital (T/F)? False - Digital
__ is the range of acceptable exposures for an image? Exposure Latitude
Of the Radiation hitting the IR, __ is the % of energy ABSORBED? Absorption Efficiency
Of the Radiation absorbed by the IR, __ is the % of energy absorbed that is CONVERTED to useable output? Conversion Efficiency
__ is the % of energy that hits the IR that results in a useful output signal? Detective Quantum Efficiency (DQE)
Detective Quantum Efficiency is the product of __ & __? DQE = Amt Absorbed + Amt Converted
↑ SNR = __ Resolution ↑ SNR = ↑ Resolution
SNR Signal to Noise Ratio
__ is a solid state sensing device alternative for CCDs? CMOS
CMOS Complementary Metal Oxide Semiconductor Receptor
↑ DEL Size = __ Spatial Resolution ↑ DEL Size = ↓ Spatial Resolution
↑ DEL Fill Factor = __ Spatial Resolution ↑ Fill Factor = ↑ Spatial Resolution
__ is the % of DEL surface space dedicated to sensing/receiving xray beam data? Fill Factor
Individual storage units on a Thin Film Transistor array of DR? DEL - Detector ELement
What part of the DR collects the electrons that represent each piece of a digital image? DELs
DEL size can be changed (T/F)? False - Fixed Size
TFTs or ___ can be made of __ or __ Thin Film Transistors - Amorphous Selenium or Amorphous Silicon
How are CR Cassettes erased? How often for unused cassettes? Bright light releases any remnant electrons. Every 48 hrs.
How long can a CR-PSP store a Latent Image? What is the rate of fading? 24 hrs, 25% fade in 8 hrs
What does DR use to absorb radiation and convert energy to electric signals? Flat Panel Direct Capture Detector Array
What is the Latent Image for DR? Electric charge stored in transistor
Direct Conversion for DR uses __ to convert remnant xray beam directly to electrons? Amorphous Selenium
Manmade phosphor crystals form what shape? They are made of __ ? Needle, Cesium Iodide
Naturally harvested PSP phosphor crystals are called __? (example) Turbid, Gadolinium Oxysulfide
Which type of DR receptor uses Amorphous Selenium to convert xrays directly to electrons? Nonscintillator Based (Direct Conversion)
With Nonscintillator (Direct) DR, what converts xrays to electrons? Amorphous Selenium
Which type of DR receptor uses Amorphous Silicon to convert light into electrons? Scintillator Based (Indirect Conversion)
2 types of Scintillator materials and formation? Cesium Iodide Needle or Gadolinium Oxysulfide Turbid
What does the Scintillator material do? Converts remnant xrays into LIGHT
For Indirect DR receptors, what happens after the Scintillator material converts xrays to light? Amorphous SILICON converts light to electrons
What is the photoconductive MATERIAL used in Scintillator based DR receptors? Where does it send its electrons? Amorphous Silicon, to TFTs
What collects the electrons in DR receptors? What does this unit do? TFT (Thin Film Transistors) produces electric signal
Created by: RadTechTKD