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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 |
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