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Freshman exit exam

Physics/equipment

TermDefinition
Nucleus small, dense center that contains the nucleons (protons and neutrons together), protons and neutrons.
atom smallest particle of an element that possesses the chemical property of that element. It’s electrically neutral, meaning that if has equal number of electrons and protons. When 2 or more atoms are chemically united, they form molecules.
Molecules are the smallest particle of a compound possessing characteristics of the compound
• Atomic Structure: o Nucleus: small, dense center that contains the nucleons (protons and neutrons together), protons and neutrons. o Electrons that orbit the nucleus.
• Atomic number (z): number of protons or electrons in the in the atom
• Atomic Mass: is the total amount of protons and neutrons in the nucleus.
• The shells around the nucleus are named starting from the inner one: o K: 2 electrons (is the shell with the higher binding energy) o L: 8 electrons o M: 16 electrons. o N: 32 electrons.
• The number of shells in an atom Principal Quantum Number.
• Octet Rule: an atom cannot have more than 8 electrons in order of it to be stable.
• Fundamental Particles of an Atom: o Electrons: negative charge. They have no mass. o Protons: positive charge. They have a mass of 1 unit. o Neutrons: neutral charge. They have a mass of 1 unit.
• Valance electron: the number of electrons in the outer shell.
3. Various Nuclear Arrangements Atomic# Atomic Mass Neutrons Number Isotope Same Different Same Isomer Same Same Same Isotone Different Different Same Isobar Different Same Different
• Centrifugal the force pushing out.
• Centripetal the force pushing in or binding energy.
4. Types of Ionizing Radiation particulate radiation: alpha and beta electromagnetic radiation: xrays and gamma rays
• Radioactivity or Radioactive Disintegration: o When the atom is instable (isotope), meaning that it has more than 8 electrons in the outer shell, it starts emitting energy, among them alpha particles, beta particles, or gamma radiation, until it becomes stable again.
o Unit for radioactivity: Curie or Becquerel. A becquerel is one disintegration (decay) per second.
• Half-life: is the time required for a quantity of radioactivity to be reduced to one-half its original value.
photons are known as electromagnetic energy. and is the smallest quantity of any type of electromagnetic energy, just as an atom is the smallest quantity of an element.
examples of electromagnetic energy. X-rays, visible light, and radiofrequencies
quantum an xray photon,
o Energy of a photon:  The energy of a photon is directly proportional to its frequency.  Higher the frequency, higher the energy  Higher the frequency higher the penetration.  Shorter the wavelength, higher the frequency Shorter the wavelength, higher the penetration
o Frequency  Frequency is the number of wavelengths that pass a point of observation per second.  The shorter the wavelength (λ), the higher is the frequency.
wavelength the distance from one crest to another, from one valley to another, or from any point on the sine wave to the next corresponding point.
 Wavelength = ____________ Velocity/Frequency
Amplitude one-half the range from crest to valley over which the sine wave varies.
o Velocity (3x10^8 m/s) =  V=f λ (frequency x wavelength)
• Frequency and Wavelength relationship: o At a given velocity, wavelength and frequency are inversely proportional.
o Electrostatics is the study of fixed or stationary electric charge.
the smallest units of electric charge. o Electrons and protons
o Electric charge associated with an electron and a proton have the same __________ but opposite sign. magnitude
o Protons are fixed, _______ are free to move electrons
• Electrostatic Law #1: Unlike charges attract, like charges repel.
• Electrostatic Law #2: Electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of distance between them. (Coulomb’s Law). The magnitude of the electrostatic force is given by this law.
• Electrostatic Law #3 When an object becomes electrified, the electric charges are uniformly distributed through the object or on its surface.
• Electrostatic Law #4 The electric charge of a conductor is concentrated along the sharpest curvature of its surface
7. Ohm’s Law states that the voltage across the total circuit or any portion of the circuit is equal to the current multiplied by the resistance V=IR (I= current and R= resistance. V= voltage).
types of circuits series and parallel
• The magnetic field lines go always from N to S, but inside the magnet goes from : S to N because they form a closed loop
o Diamagnetic Also known as nonmagnetic.
o Ferromagnetic strongly attracted by a magnet.
o Paramagnetic slightly attracted to a magnet
• Magnetic Laws: oEvery magnet has a north pole and a south pole. oLike magnetic poles repels, unlike magnetic poles attract. oMagnetic lines of forces leaves the north pole and return to the south pole. oFerromagnetic materials can be. Made into magnets by induction.
oThe magnetic force is proportional to the product of the magnetic pole strengths divided by : the square of the distance between them
9. Transformer Law •The change in voltage is directly proportional to the ratio of the number of turns (windings) of the secondary coil (Ns) to the number of turns in the primary coil (Np).
Transformer law explains how electric current, and voltage change from the primary coil to the secondary coil • Vs/Vp=Ns/Np
operating console allows the tech to control the x-ray tube current and voltage so that useful x-ray beam is of proper quantity and quality.
o Line Monitor Compensator measures the voltage provided to the x-ray imaging system and adjusts that voltage at precisely 220 V.
o Autotransformer is where the power is first delivered. It works under the self-induction principle. It only has one winding and one core. The single winding has a number of connections along its length.
o Automatic Exposure Control (AEC) It terminates the radiation exposure at a preset level. It is used to optimize radiographic technique and maximize patient safety.
what are the 2 types of AEC's? ionization chamber (placed between the patient and the IR; is the one we use now a days) or photodiode (placed behind the IR).
o Falling Load Generator provided the maximum permissible x-ray tube current at the start of the exposure with an automatic continuous decrease in current during the exposure that avoid overheating of the tube.
o Spatial Resolution is the ability to image small objects that have high subject contrast. (Can also be called detail and sharpness) - Controlling factor for density mAs.
 Optical Density the degree of blackening on an image. It has a precise numerical value.
 Factors Affecting Spatial Resolution: - Motion Blur - Geometric Blur - SID - OID
o Contrast resolution: is the ability to image two separate objects and visually distinguish one from the other  Controlling factor kVp.
 Radiographic contrast is the product of 2 separated factors: - IR contrast - Subject contrast
 Factors affecting contrast resolution: - Collimation - kVp (lower the better) - Grid
o Noise Radiographic noise is the random fluctuation in the OD of the image.
 Components of noise: - Quantum mottle/noise: The use of high mAs, low kVp settings and slower image receptors reduces quantum mottle. You can minimize it by using high mAs, low kVp (reduces scatter) and slower IR.
• Factors that affect scatter production: - Collimation (field size) - Lowe kVp - Tissue mass density (patient thickness), that can be controlled by compression. o Artifacts
2. 15% Rule • A 15 % increase in the kVp will have the same effect than doubling the mAs. Meaning that it would double the density.
3. Inverse Square Law • It describes the relationship between radiation intensity and disturbance from the radiation source. (Relationship between distance and exposure) • I1/I2= (D2/D1)2
4. Geometric Factors magnification, distortion, blur
• Magnification Images appear larger than objects
• Magnification Factor = Image Size/Object Size or SID/SOD
• Minimizing Magnification: o Long SID o Short OID o Compression
• Distortion Unequal magnification of different portions of the same object
o Spatial distortion the misrepresentation in the image of the actual spatial relationships among objects.
o Factors Contributing to Distortion:  Object thickness  Object Position  Shape of the Object:
- Foreshortening if the image of an object is smaller than the object.
- Elongation if the image of an object is larger than the object.
- Shape distortion: collectively these conditions of foreshortening and elongation.
• Focal Spot Blur: o Is a region of un-sharpness on the image over which the tech has little control. We can also call it penumbra and geometric un-sharpness. o It is the most important factor in determining spatial resolution.
o How to reduce focal spot blur:  Short effective focal spot  Long SID  Short OID
o Focal Spot Blur is more in the _______ because effective focal spot size is larger on the cathode side. cathode side
o Focal Spot Blur = Effective Focal Spot x OID/SOD
5. Subject Contrast difference in the intensity transmitted through the different parts of an object.
• Factors that affect subject contrast: oPatient thickness oTissue density mass density oAtomic number: the higher the atomic # the better the contrast. oObject shape okVp or energy of the beam : lower the kVp higher the subject contrast because it produces less scatter. -motion blur
 How to reduce motion blur: - Short exposure time - Proper instructions to the patient - Use restraining devices - Large SID - Short OID
• Devices that can minimize the amount of scatter that reaches the IR: o Grid o Beam restrictors o Air gap technique
• The_______ must be used when the part is greater than 10 cm or more than 60 kVp is needed for the exam. grids
• The linear and low grid ratio have ______ positioning latitude more
• High grid ratio has _______ contrast improvement factor and _______ pt dose. higher, more
• Types of grids: o Parallel Grid o Crossed Grids (produces more contrast) o Focused Grid o Moving Grids (most common type)
grid Problems: o Off level: overall decrease in density. o Off center: overall decrease in density. o Off focus: loss of density on the sides. o Upside-down: loss of density on the sides
• Indirect DR: o X-rays are absorbed by a thin layer of cesium iodine (CsI), a scintillation phosphor, which. Then produces a flash of light. This light interacts with a layer of amorphous silicon photodiode to create the electric charge.
• Direct DR: o X-ray interact directly with a layer of amorphous selenium, which then produces the electric charge (this one is faster).
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