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Intro to Radiography

Radiographic Imaging Chapter 7

4 basic requirements for the production of x-rays 1. Vacuum (tube housing) 2. Source of electrons (filament) 3. Method to accelerate electrons rapidly (Voltage) 4. Method to stop the electrons (target)
Beam of x-rays, mechanically produced by passing high voltage through a cathode ray tube, transverses a patient and is partially absorbed in the process. Basic mechanism of radiographic image production.
4 Basic methods of Imaging the body: 1. X-rays (Radiography & CT) 2. Gamma Rays (Nuclear medicine) 3. Sound waves (Ultrasound) 4. Magnetism (MRI)
In making x-rays, electrons are created at the ________ and accelerated to the _______? Cathode; Anode
In making x-rays, the kinetic energy of the electrons is converted into what? Heat (99%+) and X-Rays (less than 1%)
Electrons always move to what direction? Toward Positive
Cathode is what charge? Negative
Anode is what charge? Positive
This is the measure of the electrical current passing through the x-ray tube. Milliamperage
mAs directly controls the _________ of x-ray photons produced. Quantity
What is the measure of electrical pressure (potential difference) forcing the current through the tube? kVp (Kilovolt peak)
This primarily affects the quality but also the quantity of the x-ray photons produced. kVp
The distance between the point of x-ray emission in the x-ray tube and the image receptor. SID (Source to Image Distance)
The "C-Arm" is primarily used in this setting? Surgery
Name the 3 things that make up DENSITY. 1. Primary Radiation (radiation exiting the tube) 2. Remnant Radiation (the primary radiation that passes through the patient producing the image) 3. Scatter or Secondary Radiation (primary radiation that changes direction)
This radiation is the image producing radiation that passes through the patient Remnant Radiation
This radiation produces bad images and makes the image look more gray. Scatter or Secondary Radiation
This radiation is the primary reason for Collimation. Scatter Radiation
The process by which the nature of the primary radiation is changed (partially absorbed) as it travels through the patient. Attenuation
Name the 2 types of Luminescence: 1. Fluoroscence 2. Phosphorescence
The emission of visible light only during stimulation of an outside force. Fluoroscence
The continued emission of light after stimulation has ended. Phosphorescence
Phosphorescence in an intensifying screen is called ___________ or ___________ and can be objectionable (not good) Screen lag; Afterglow
95% of the ___________ on a radiography is from light emitted from a screen. Density
The invisible image inside the base of the radiographic film Latent Image
A light-tight holder for the film: Cassette
Remnant radiation that hits the buckie tray and bounces back: Backscatter
The back of this type of cassette will have a low atomic number material to allow remnant x-rays to reach the photo-timer thus ending the exposure when the image is received: Photo-Timed cassette
This type of cassette has a _______ atomic material to absorb backscatter radiation. High
Cassettes should have these 2 types of characteristics: 1. Compression device (felt or rubber to maintain a close film/screen contact) 2. Back
The 2 basic properties of the X-Ray Beam: Quantity and Quality
Name the 4 properties of Quantity: (NIME) 1. # of Photons 2. mAs (milliampere seconds) 3. Intensity 4. Exposure
Name the 3 properties of Quality: (SPH) 1. Strength 2. Penetrating Power 3. Hardness
Density is the amount of _________ on the film. Blackness
mAs is _______ __________ to Density. Directly proportional (mAs = Density)
60 kV = __________ volts 60,000
1 Kilo = 1000
1 millisecond is equal to? 1/1000 of a second
Convert to decimal: 30milliamps .03 amps
Convert to decimal: 4milliamps .004
Convert to decimal: 500milliamps .5
_____ = mA x time in seconds mAs
Convert to milliseconds: 0.25 sec 250milliseconds
Convert to milliseconds: 3/10 sec 3/10 = 0.3 = 300milliseconds
Solve for mAs: 1. 100mA at 1/2 second 2. 200mA @ 0.4 second 3. 400mA @ 250millisecond 1. 100 x 1/2 = 50mAs 2. 200 x 0.4 = 80mAs 3. 250milliseconds = .25 seconds: 400 x .25 = 100mAs
The controlling factor for Contrast is? kVp
The controlling factor for Density is? mAs
Formula in solving for Intensity and Distance: I(original)/I(new) = Density(new)squared/Density(original)squared
A 15% increase in kVp will result in a DOUBLING the density and a 15% decrease in kVp will result in cutting the density in HALF kVp 15% Rule
Why would increasing the SID decrease the intensity of the beam? Divergence of the beam
There must be at least ___% change in distance to cause a visable change in density and require an adjustment in technique. 20%
Inverse square law of SID and Density Intensity = 1/Distance squared
Thin patients will have more or less density on the radiographic image? More
Fat, muscle and air will have more or less density on a radiographic image? More
What is the major controlling factor for Contrast? kVp
An increase in kVp will increase or decrease contrast? Decrease Contrast
Increasing kVp will do what to Density? Increase Density
kVp in relation to Density follows what rule? 15% rule
The 15% rule means what? Increasing kVp 15% doubles Density; Decreasing kVp 15% cuts Density in half
How much more kVp would double the density if the original kVp was 80? 12 more kVp would be 92kVp which would double density
What would be the new kVp to Half the density if the original kVp was 60? 15% of 60 = 9, the new kVp to cut the density in half would be 51kVp
Intesity is measured in ______ mR (milliRoentgen)
When changing the kVp 15% what must you do to mAs to maintain the same exposure? increasing kVp 15% requires you 1/2 mAs; Decreasing kVp 15% requires you to double mAs
What is the formula for solving for Intensity and Distance? Inverse square law: I(1)/I(2) = D(2)Squared/D(1)squared
Intensity is the ___________ of photons in the beam. Number
Increases the SID does what to the intensity? Decreases because of divergence
Changing the SID by _____% will cause a visible change in Density and require an adjustment in techniqe 20%
When solving for distance and beam intensity what is the formula? I=1/d squared
What is the intensity if the distance is 3 m? I=1/9
What is the intensity if the distance is 8 m? I=1/64
The filtration made possible by the glass envelope and the cooling oil which the beam must pass through is called ____________ filtration Inherent filtration
Inherent plus added filtration is called __________ Total filtration
A sheet of metal through which the x-rays must pass before striking the object to be examined or treated is called? Filter
Tube housing (vacuum) is usually made of what substance? Lead
This term describes the hardness, penetrating ability or quality of the beam. Half Value Layer (HVL)
The thickness of a specified material (filter) that will reduce the original intensity of the beam to half its initial value is called? Half Value Layer
The measurement of kVp is Half value layer
Increasing mAs does what to Density? Contrast? Increases Density; nothing to contrast
Increasing kVp does what to Density? Contrast? Increases Density; Decreases Contrast
Increasing film speeds does what to density? Contrast? Increases Density; decreases Contrast
Increasing film processing chemicals does what to Density? What to Contrast? Increases Density; only a 2degree increase will increase contrast more than that will decrease contrast
Increasing collimation does what to density? Contrast? Decreases Density; Increases Contrast
Increasing grid ratio does what to Density? Contrast? Decreases density; Increases Contrast
Increasing screen speed does what to density? Contrast? Increases Density; Increases Contrast
Increases in processing by 2 degrees or 2 seconds does what to contrast? Increases contrast
Increases in OID does what to contrast? Increases contrast
Anything that reduces scatter does what to contrast? Increases contrast
Contrast media does what to contrast? Increases contrast
Positive contrast media does what to Density? Contrast? Decreases density; Increases Contrast
Negative contrast media does what to Density? Contrast? Increases Density; Increases contrast
These factors have no effect on contrast: mAs; time; FSS; SID
Detail/Distortion is also referred to as? Resolution
The sharpness of structural line or minute details on the radiograph Detail
The 2 parts to detail are: Visibility of Detail (can be seen but not measured); Geometric (can be measured)
4 ways to reduce motion: Short exposure techniques; Immobilization; Suspension of respiration; COMMUNICATION
The image proper or true image is known as: umbra
The light hazy area surrunding the true image penumbra
3 factors that affect Geometric Detail: SID (Increases in SID reduces penumbra) OID (Increasing OID increases penumbra) FSS (Increasing FSS increases penumbra)
Best Detail in Radiographs have these geometric qualities: Longest possible SID; Shortest possible OID; Smalles possible FSS
Misrepresentation of the true size and or shape of the object is known as: Distortion
2 types of distortion: Size (true distortion) Shape (false distortion)
Magnification: If OID must be increased what should be done to SID to compensate for the loss of Detail and increase in magnification? Increase SID
Foreshortening happens when the object is not __________ with the film Parallel
_________ happens when the tube is angled. elongation
This type of imaging is dynamic in nature. Fluoroscopic Imaging
What is caused by the misalignment of the tube? Shape distortion
This is part of the electromagnetic spectrum and is used in imaging techniques in the form of x-rays-for conventional radiography & computed tomography-or gamma rays for imaging in nuclear medicine. Ionizing Radiation
This is the forming part of the beam: Remnant Radiation
Negative contrast media will do what to the image? Darken (lessen the atomic number)
Positive contrast media will do what to your image? What is the change in atomic number? Lighten the image (Increases the atomic number)
Which would have higher contrast Regular speed screen or an extremity cassette? Regular speed screen
Increasing OID does what to density and contrast? Higher contrast (reduces scatter) and lower density
What 4 things have no effect on Contrast? mAs, Time, FSS, SID
What 3 things give the BEST geometric detail? Increasing SID, Decreasing OID, Small FSS
Thomas Edison invented this type of phosphor material: Calcium Tungstate
Radiolucent material has more or less density? More
What percent of density is from light emitted on a screen? 95%
kVp affects what 2 things of the x-ray photon? Wavelength and frequency
How does kVp affect Density? 15% rule
What are automatic collimators called? Positive Beam Limitation (PBL)
This is a device designed to remove as many scattered x-ray photons as possible: Grids
Anything bigger than ______ should use a "Bucky" 12cm
Increase in OID does what to contrast? Increases contrast
Increasing screen speed does what to detail? Decreases detail
An increase in screen speed does what to density; what to contrast? Increases density; increases contrast
What 3 things give the best detail? Increase SID Short OID Smallest FSS
Created by: foster1317