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Intro to Radiography
Radiographic Imaging Chapter 7
| Question | Answer |
|---|---|
| 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 |
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