Rad Tech unit 2 Exam

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92 Terms

1

Attenuation

The process by which a beam of x-ray photons is reduced as it passes through matter is known as:

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Photostimulable phosphor plate (PSP)

Computed radiography uses which of the following as its image receptor:

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125

What mAs value would result using the 500 mA setting at 0.25 secs:

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130

A radiograph is made using 40 mAs at a 40 inch SID.  If the image must be repeated at a 72 inch SID, what mAs value is necessary to maintain the same exposure?

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kVp

The 15% rule helps explain the effect of ____ on exposure

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X-ray Tube

The component of the radiographic system that produces radiation is the:

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Operator control console

The control of exposure factors such as mAs and kVp is performed at the:

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8

Anode and Cathode

The primary components of the x-ray tube are the:

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9

Fluoroscopy

It permits “real time” imaging of dynamic patient functions

Modern-day fluoroscopy systems record images electronically rather than using cassettes

Dose reduction features such as last image hold (LIH), pulsed fluoroscopy, and electronic shuttering are essential. 

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10

What is necessary for x-rays to be produced

A source of electrons

Rapid particle acceleration

Instantaneous deceleration

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11

Photoelectric interaction

The interaction of x-rays with matter that constitutes the greatest hazard to patients in diagnostic radiography is:

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12

14 mR

The intensity of radiation from a radiographic tube was 35 mR at a distance of 2.5 m from the tube.  What would the intensity be at a distance of 4 m from the tube, if all other factors remained the same?

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13

200 rem

An exposure of 2 Sv is received.  How many rem is this equivalent to? 

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14

The Photoelectric Effect

Lead absorbs x-rays through the process of ____.

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15

X-Ray Production Requirements

1.     X-ray tube with a vacuum inside

2.     Source of electrons (from a filament)

·      Cathode

3.     Method to accelerate electrons to great speed

·      Voltage (kVp)

4.     Method to stop electrons

·      Target

·      Anode

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16

<1%

What % of electrons hit the target are actually produced in to x-rays?

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17

Primary radiation

is the first initial one out of the tube (air only)

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18

Scatter radiation

went in a different direction

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19

Absorbed radiation

in the patient’s body

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Remnant radiaton

what is left after the patient has absorbed some/ goes to make image

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Attenuation

is the loss of radiation energy as a result of passing through an absorbing material, such as the human body

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radiopaque

High attenuation occurs in what kind of matter (whiter)

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23

radiolucent

Low attenuation occurs in what kind of matter (able to go through easier, darker area)

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24

Film-Screen radiography

·      Uses x-rays to create a permanent image on a piece of polyester film

·      Consists of x-rays directed at a radiographic cassette with an intensifying screen

·      Intensifying screens convert the x-ray energy to light, and light energy creates chemical changes in film

·      Needed to be processed in a dark room

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25

Computed Radiology (CR)

·      Still needs a reader to process the image

·      Aka: Cassette-based DR

·      Filmless

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Digital Radiography (DR)

·      Cassette-less system

·      Direct capture

·      Indirect Capture

·      Most popular

 

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Photographic Qualities

how good it looks

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Geometric Qualities

should look a certain way

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Photogenic Qualities: Image Density (Intensity)

·      The overall darkness or blackness of an image

·      Directly related to x-ray exposure hitting the receptor

·      Primarily affected by milliamperage (mA), exposure time (S), source-to-image (SID)

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mA is a Primary Factor of Density

·      mA represents the quantity of x-ray production

·      Direct relationship (if you turn the mass up, it gets darker)

·      mAs is calculated by simple multiplication of mA and seconds

·      Regardless of the mA and time combinations, the same mAs value will yield the same exposure

·      mAs reciprocity law

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Kilovoltage Peak (kVp)

·      controls x-ray beam penetration

·      Quality

·      Direct relationship

·      X-ray beam is polyenergetic or heterogenous

·      15% rule

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Distance

·      Displayed as source-to-image distance (SID)

·      X-ray production is similar to a point light source (flashlight)

·      Behaves according to the laws of light and intensity as a function of distance

·      Inverse square law

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Grids

·      Used to reduce the amount of scatter radiation reaching the image receptor= Scatter Control

·      Intercept a portion of the remnant radiation

·      Improve image quality.

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Exposure Index (EI)

·      A numeric (quantity) representation of total x-ray exposure to the receptor

·      Not an indicator of the patient’s absorbed dose

·      Values can vary greatly among manufacturers= different results have different #s per brand

·      S#

·      In the future: Deviation Index (DI) will be used to measure patient exposure used by the radiographer

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Geometric Qualities

·      Contribute to image quality by affecting.

-image resolution (clarity), size, and shape

·      Also known as recorded detail, sharpness of detail, and definition

·      Complemented by visibility of detail, which is a photographic property

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Factors Affecting Recorded Detail:

·      Motion

·      Object unsharpness

·      Focal spot size

·      SID

·      Object-to-image distance (OID)

·      Material unsharpness

·      Distortion

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Distortion

Any misrepresentation of the true size or shape of the patient’s anatomy as demonstrated on the radiographic image

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Size distortion

·      The image is always slightly larger than the actual object size

·      Known as true size distortion, its minimized by using longer SIDS and minimum OIDS

·      Magnification

·      Reduce OID to avoid

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Shape distortion

·      Elongation

·      Foreshortening

·      Any misrepresentation of the true shape of the patient’s anatomy

·      Also called true distortion

·      Controlled it:

-Align central ray, patient’s anatomy and IR

·      May be deliberate to deal with superimposed structures

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40

Elongation

shape distortion resulting form improper alignment of the Image receptor

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Foreshortening

shape distortion resulting from improper alignment of the part

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Fluoroscopy

·      Use of x-rays to create real-time images of patient anatomy and function

·      Patient exposures are much MORE (higher) than radiographic exposures

·      Requires a radiographic/fluoroscopic (R/F)

·      Physicians can observe the body’s physiologic actions

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Diagnostic Yield:

how much good quality info can be gained from the exam or test ordered

·      Why one modality is chosen over the other

·      Dictated by the ACR considerations

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Diagnostic Efficacy

The accuracy of diagnostic info on a medical image is its

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45

X-Ray machine design features

·      X-ray and x-ray tube support

·      Collimator assembly- holds the tube

·      Radiographic table-

·      X-ray generator and control

·      Upright image receptor

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X-ray tube design

·      Tube is inside the lead- lined tube housing

·      Made of Pyrex Glass with High vacuum

·      Produces x-radiation when high-energy electricity passes through

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Collimator Assembly

·      Controls the size and shape of the x-ray field directed toward the patient

·      Projects high intensity light field on the patient, which represents the area of the x-ray field exposure

·      May be manual or automatic/positive beam limitation (PBL)

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Radiographic Table

·      May be fixed height or variable height

·      Typically has  a four way “floating” tabletop

·      Tabletop is highly Radiolucent (doesn’t stop radiation)

·      Some table designs permit a carriable- speed, tilting capability

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Tilting Radiographic Table

·      Utilized in Fluoroscopy

·      These designs will tilt the table from horizontal position to vertical upright position to Trendelenburg

·      Most tables have four-way tabletop travel

·      These tables typically do not have variable height capabilities

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50

Bucky Assembly

·      Consists of a receptor tray and radiographic grid

·      Used with Film Screen and computed radiography systems

·      The grid spins to blur out the lead grid lines

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Upright Bucky assembly

·      Upright Bucky with lateral chest support arm

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Generator Control (control console)

·      Control console is the interface between the radiographer and the sophisticated electronics of the x-ray machine

·      Set all the numbers, where all the info comes from

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X-ray Tube supports

·      Two basic designs

·      Facilitate easy and efficient positioning of the x-ray tube assembly around the patient in any orientation

·      Ergonomic (comfortable) Friendly

·      Capable of various motions depending on need

·      Detents (areas where it wants to lock into place) says you are in the right spot

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54

Image receptors (IR):

·      Cassette- based systems

·      Film-screen

·      Computed radiography (CR)

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Digital Radiography (DR) systems

Referred to as flat panel technology

DR systems use thin-film transistors (TFTs)

·      Indirect digital detector technology

·      Direct digital detector technology

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56

Fluoroscopy

·      Dynamic imaging

·      Provides live, real-time images of patients using x-rays

·      Used for a wide array of diagnostic procedures

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57

Mobile (C-Arm) Fluoroscopy system

·      Used in surgery and interventional exams

·      Uses a C-arm design

·      Image receptor is at a fixed SID and centered to x-ray tube

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58

Mobile X-ray imaging (Portables):

·      Mobile radiographic units are used extensively in hospitals

·      Bring into patient’s room

·      Needs to be charged

·      Easier on the patient

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59

Incident (primary) X-ray

is the x-ray that comes from the x-ray tube

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60

Coherent Scattering:

X-rays with energies BELOW 10 keV (low energy)

No ionization occurs due to no energy transfer

Called

Classical Scattering

Thompson (J.J Thompson)

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Scattered x-rays:

o   Wavelength is equal to the incident x-ray

o   Equal Energy to the incident x-ray

o   Direction Changes

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Compton Scattering:

·      X-rays that occur throughout the diagnostic range

·      Outer-shell electron interaction

o   Ejects it from the atom

Scatters x-ray in a different direction

X-ray loses energy

Ionizes the atom

·      Causes Scatter radiation to show on the image

·      Tighter the ray, the more energy

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Photoelectric Effect:

·      X-rays in diagnostic range

·      Ionizing interactions with inner-shell electrons

·      No scattering= totally absorbed

·      Albert Einstein= Nobel Prize in 1921

·      Photoelectron- electron that is removed from the atom

·      Energy is equal to the incident x-ray and the binding energy of the electron

·      Characteristic X-rays are produced after a photoelectric interaction

·      Vacant k Shell

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Pair Production:

·      Doesn’t occur within x-rays

o   Only in PET scans

·      Incident x-ray has sufficient energy that comes close to the nucleus of the atom (a nuclear field)

·      Causes x-ray to disappear.

o   Positive charged electron (positron)

o   Negative charged electron

·      Annihilation Radiation: When the positron unites with a free electron and mass of both particles is converted to energy

·      PET Scan: Positron Emission Tomography

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Photodisintegration:

·      X-rays with energy above 10 MeV (high energy)

·      Energy absorbed by the nucleus

·      Doesn’t occur in diagnostic imaging

·      Nucleus raised to an excited state and instantly emits a Nuclear Fragment

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66

Roentgen

·      Measures exposure in air and is not used to express absorbed dose to individuals

·      A measure of ionization in air as a result of exposure to x-rays or gamma rays

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Radiation Absorbed Dose

·      Expressed as rad

·      Measures amount of energy absorbed in any

·      1 Gy= 100 rad

·      Rad has been replaced by the gray (Gy)

·      Patient

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Radiation Equivalent Man

·      Measured as rem

·      Unit of dose equivalence (dose to you as the Tech)

·      1 Sv=100 rem

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Curie

·      Measures the activity of a radioactive material (radionuclide)

·      Used in nuclear medicine and radiation therapy

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Standards of Exposure

·      Standards are regulated by the FDA and its center for Devices and Radiologic Health (CDRH)

·      The annual whole-body effective dose limit for the occupational worker is 50 mSv (5 rem) (5000 mrem)

·      Use the Cardinal rules: time, distance, and shielding

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Radiation Monitoring

·      Any occupational worker is regularly exposed to ionizing radiation must be monitored to determine estimated exposure

·      Any worker who is likely to receive more than one tenth of the recommended dose-equivalent limit should be monitored

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Occupational Personnel Monitoring

·      Monitors/measures the quantity of radiation received on the basis of conditions in which the radiographer was placed

·      Worn at the collar level

·      Worn outside of lead apron

·      Decide should face forward

·      Pregnant radiographers may have a second device worn at waist level and under the apron

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Coherent Scattering:

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Compton Scattering:

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Photoelectric Effect:

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Pair Production:

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Photodisintegration:

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PACS (picture archiving and communication system)

used to securely store and digitally transport electronic images and clinically reverent reports

eliminates the need to manually file and store things

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HIS (hospital Info system)

improves efficiency and effectiveness of patient care

stores, manages and captures info related to activities of patients and statistical data

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RIS (radiology info system)

networked software system for managing medical imagery and associated data

tracks imaging order and billing info

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PBL (positive beam limitation)

the automatic or semiautomatic adjustment of an x-ray beam to the size the selected image receptor, whereby exposures can’t be made without such adjustment

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OTC (overhead tube crane motions)

transverse, vertebral, longitudinal movements

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AEC ( Automatic Exposure control)

density control decide that terminates the exposure when a predetermined amount of radiation has been reached

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ALARA (as low as reasonably achievable)

competent imaging professionals will strive to maximize diagnosis yield using a minimum of output factors

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Bq (becquerel)

SI unit of activity

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Ci (curie)

measures the activity of radioactive material

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Gy (gray)

1Gy=100rad

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R (roentgen)

unit measures radiation exposure

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Sievert

1sv=100rem

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rad (radiation absorbed dose)

measures the amount of energy in the patient

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