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RAD FINAL
| Question | Answer |
|---|---|
| Image Contrast | - Number of different densities in an image - Controlling factor is kVp - volts = energy - quality of beam |
| Receptor Exposure | - Overall blackness of an image - controlling factor is mAs - quantity = amount the IR receives - amp = current - goal is high mA, low time |
| IR exposure considerations | High kVp = wide latitude, low contrast Low kVP = high contrast |
| Spatial Resolution | How sharp the image appears, definition, recorded detail |
| good, clear sharp image | High SID, low OID, small FSS |
| poor image resolution | Low SID, high OID, large FSS |
| kVp | Measure of potential difference which controls beam quality |
| mAs | Milliamperage multiplied by exposure time in seconds, which controls the total quantity of the x ray photons |
| Factors affecting image resolution | - Spatial resolution (temporal resolution, beam geometry, FSS, SID, OID distortion, shape distortion, IR characteristics) Contrast resolution |
| Classic Coherent Scattering | - Low energy x rays - x ray interacts with atom as a whole - atom becomes excited and emits X ray with same energy - no ionization, no energy transfer, to patient or matter |
| Photoelectric Effect | - Incoming X ray photon is completely absorbed by collision w/ inner shell electron, responsible for larger contribution to patient exposure - photoelectron leaves atom, cascade/secondary radiations created - only ionized electron, NO SCATTERED PHOTON |
| Compton Scattering | - Incoming photon collides w/ outer shell electron, creating a free comptom electron (recoil), and an ion pair - Incoming photon loses some of its energy through collision, scatters off in a random direction (scatter angle) - Photon in, electron out, ph |
| Air Kerma | acronym - KERMA - Kinetic Energy Released in Matter - measured in J/Kg or Gray (Gy) |
| Exposure limits - fetal, educational, occupational annual, occupational cumulative | fetal .5 mSv educational 1 mSv occupational 50 mSv cumulative 10 mSv x age |
| Cardinal rules of protection | Time, distance, shielding |
| Fluoroscopy | Imaging technnique using x rays to produce real-time moving images of internal structures in the body |
| Difference between diagnostic efficacy and diagnostic yield | Yield - how well the modality is suited efficacy - accuracy of the depiction of patient's condition |
| Law of Bergonie and Trib | Immature and quickly duplicating cells are more radiosensitive |
| Popular monitoring technologies | - Pocket dosimeter - OSL (optically stimulated luminescence dosimeter) - TLD All are worn on collar, pregnant women wear an additional monitor on waist |
| LET | Linear energy transfer - dose response curve |
| Poor spatial resolution is a result of | Maximum OID, minimum SID |
| What affects receptor exposure? | mAs, OID, SID, FSS |
| What is the result of a photoelectric interaction? | absorption of X ray photon energy |
| ALARA | As low as reasonably achievable |
| Measure of exposure in air | coulomb/kg |
| Measure of absorbed dose | Gray (Gy) |
| Dose equivalent | Seivert (Sv) |
| Measure of radioactivity | Becquerel (Bq) |
| Factors Affecting Subject Contrast | kVp, amount and type of irradiated material, contrast media, mAs, beam modification, image receptor, grids |
Created by:
radleylittle