Exposures chapter 22

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Medicine - Radiology

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Scatter is affected by _____, field size, and part thickness.

Increased kVp results in increased _____

Increased field size results in increased _____

More matter results in more _____

Increased scatter results in decreased _____ _____

What are the different ways an image can react to x-rays? Choose from: large angle scatter, small angle scatter, transmission, and absorption.

Large angle scatter occurs when x-rays interact with the patient and scatter _____ from the IR.

Small angle scatter occurs when x-rays interact with the patient and scatter _____ the IR.

Absorption occurs when x-rays interact with the patient and are _____ within the patient.

Transmission occurs when x-rays _____ through the patient without interaction to strike the IR.

What is the result of Compton interactions? The x-ray photon loses energy and _____ direction.

The amount and energy of scatter is affected by kVp, x-ray beam field size, and _____ of tissue.

Increased kVp results in decreased _____ _____

Increased kVp results in increased _____ _____

What level of kVp is required for large patients to ensure adequate penetration of the part being imaged? A _____ kVp is needed.

High kVp results in less photoelectric absorption and more _____ scatter.

Less photoelectric absorption due to high kVp results in fewer total interactions with tissue, higher transmission of x-rays through tissue, and _____ patient dose.

Low kVp results in more photoelectric absorption and less _____ scatter.

More photoelectric absorption due to low kVp results in more total interactions with tissue, less transmission of x-rays with tissue, fewer x-rays meet the IR, and _____ patient dose.

Increased mAs results in plenty of _____ at the expense of _____ _____

Making a small increase to _____ results in more scatter but less patient dose.

To reduce scatter, you can _____ the beam.

Increasing field size results in using less collimation, which increases scatter, reduces image contrast, and _____ patient dose.

Decreasing field size results in more collimation, which decreases scatter, improves image contrast, and _____ patient dose.

What are three important dimensions of grid construction? They include the width of grid strip, width of inner space material, and _____ of grid.

What does k stand for in the context of grids? It is the ratio of image contrast with a grid to image contrast without a grid.

What is the contrast improvement factor range? It typically ranges from _____ to _____

What are three beam restricting devices? They include aperture diaphragm, cones or cylinders, and _____

What are three things that affect scatter? They include kVp, x-ray field size, and _____ thickness.

What does scatter affect? It affects contrast resolution and _____ contrast.

When you increase kVp, what happens to scatter? You'll have _____ scatter.

What happens if you increase the x-ray field size? There is an increase in _____

What happens if you have a thicker body part? There is an increase in _____

If there is more scatter, what may decrease? _____ contrast may decrease.

What happens at high kVp? There is less photoelectric absorption, higher transmission of x-rays through tissue, and _____ patient dose.

What composes image-forming x-rays? They include transmitted x-rays and _____ x-rays.

What is the aperture diaphragm? It is the simplest beam restriction device, made of lead or lead-lined metal attached to the x-ray tube head.

What are the cones/cylinders? They are modifications of the aperture diaphragm, useful for imaging sinuses and skull work, but can be difficult to align.

What does a cylinder do better than a cone? It limits _____ more effectively.

What is the light localizing variable aperture collimator also known as? It is known as a _____ beam limitation device.

What does the light localizing variable aperture collimator do? It reduces patient dose and improves _____ contrast.

The collimator misalignment should be less than _____ of the SID used.

What are some advantages of using a grid? It cleans up scatter and improves _____ contrast.

What are disadvantages of the grids? They increase patient dose due to an increase in _____

When was the grid invented and by whom? It was invented in 1913 by _____

When should a grid be used? If part thickness is over 10cm, and if kVp is over _____

Describe the structure of a grid. It consists of radiopaque lead strips that absorb x-rays and radiolucent interspace that _____ photons.

What percentage of scatter will a high-quality grid clean up? It cleans up _____ to _____%

Large angle scatter is more likely to be _____ by lead strips.

Small angle scatter is more likely to be _____

When is an aperture diaphragm used? It is used when x-ray field cut off can occur if the diaphragm is not properly _____

An aperture diaphragm should always allow x-rays to expose an area that is just _____ than the image receptor.

What are some ways that x-rays can interact? They can interact with the patient and scatter away from the IR, scatter toward the IR, be absorbed by the patient, or be _____ through the patient.

As kVp increases, what happens to photoelectric absorption? It _____

What is the result of Compton interactions? The x-ray photon loses energy and _____ direction.

What results from an increase in field size? There is less collimation, scatter increases, image contrast reduces, and patient dose _____

What can collimation reduce and improve? It reduces patient radiation dose and improves _____ contrast.

What do imaging forming x-rays do? They exit and interact with the _____

As scatter radiation increases, what happens to the image? It loses contrast and appears _____ and gray.

Define image-forming x-rays. They are x-rays that exit and interact with the _____ receptor.

Explain the relationship between kVp and scatter. As kVp increases, Compton scatter increases, leading to reduced _____ contrast.

How much of the x-ray beam incident on the patient is transmitted through the patient without interaction to become part of the image-forming beam? Approximately _____%

Describe how photoelectric interactions influence the appearance of the radiographic image. More photoelectric absorption results in more total interactions with tissue, but less transmission of x-rays through tissue, therefore, fewer x-rays interact with the _____

Explain how Compton scatter contributes to reduced image quality. The x-ray photon loses energy and changes direction, causing scatter, and the more Compton scatter, the less it interacts with the _____

List the 3 primary factors influencing the intensity of scatter in the image-forming beam. They include field size, increasing kVp, and patient _____

Explain the relationship between kVp and patient dose. A small increase in kVp is usually sufficient to provide enough x-rays, and this can be done at a much _____ patient dose.

Explain the relationship between kVp and photoelectric interactions. As kVp increases, photoelectric interactions _____

Explain the relationship between field size and scatter radiation. As field size increases, scatter radiation _____

Explain several ways contrast resolution is improved. Contrast resolution is affected by scatter radiation, but dynamic range and post-processing allow for much enhanced _____ resolution.

A fixed aperture diaphragm should leave a _____ cm unexposed border on the radiographic image.

What is the most commonly used beam restricting device? It is the light-localizing variable-aperture _____

Explain how the use of a compression device will improve image contrast. Compression of anatomy improves spatial resolution and image contrast and lowers patient dose by bringing the anatomy closer to the _____

Explain the relationship between kVp and image contrast. When kVp is increased, image contrast is reduced because the level of _____ increases.

Explain how collimation improves contrast and reduces patient dose. Proper collimation of the x-ray beam has the primary effect of reducing patient radiation dose by restricting the volume of _____ tissue.

What is the purpose of the PBL? It automatically collimates to the IR size, but even with PBL, the technologist should always manually _____ more tightly.

Explain how the mAs should change when an air-gap technique is used. When an air-gap technique is used, the mAs is increased about _____% for every cm of air gap.

Explain when a grid should be used. It is best used when the part is 10cm or greater and kVp is greater than _____

Define Convergent Point. It is the point at which imaginary lines drawn from each lead line in a linear focused grid _____

Describe the most common type of grid cut off with mobile radiography. Grid cutoff can occur with any type of grid if the grid is improperly positioned, but it is most common with _____ grids.

When does a Crossed Grid have grid cutoff? It occurs when the grid is not properly aligned and when taken at distances other than those _____

When does a Focused Grid have grid cutoff? It occurs when it isn't aligned correctly and when taken at distances other than those _____

Explain the purpose of the first-stage entrance shutters of a variable aperture collimator. They control off-focus radiation by protruding from the top of the collimator into the x-ray tube _____

How much scatter will high-quality grids clean up? They attenuate _____% to _____% of scatter radiation.

Explain the relationship between collimation and the quantity of photons that reach the IR. Reducing your collimation will reduce the quantity of photons that reach your _____

Describe the construction of a grid. It includes lead strips used for absorption and aluminum or plastic interspace for _____

Know who invented the bucky and when. It was invented by _____ in 1913.

Focused vs Parallel grids: Focused grids allow more transmission of x-ray photons and grid strips are angled to match the divergence of the beam, while parallel grids are non-focused, grid strips run parallel to each other, absorb more transmitted photons, and are good for _____ and mobile imaging.

List the names/types of moving grids. They include reciprocating grids and _____ grids.

Explain the relationship between SID and mAs in regards to using an air-gap technique. When using an air-gap technique, the IR is moved 10-15 cm from the patient, reducing the amount of scatter hitting the IR, and your mAs should increase approximately _____% for every cm of air gap.

Grid frequency ranges from _____ to _____ lines/cm.

Explain the importance of controlling scatter from the standpoints of image quality, patient dose, and occupational dose. Controlling scatter will help increase your image quality, therefore, decreasing your patient dose and _____ dose.

Define the moiré effect. It is a radiographic artifact that results from using a stationary grid with _____ imaging.

Define convergent line. It is the imaginary line formed when convergent points at each end of the grid are _____

Define focal distance. It is the distance between the grid and the convergent point or line, used to determine _____ range.

What is the simplest beam restriction device? It is the _____ diaphragm.

What are some advantages to using aluminum interspace material? It has a higher atomic number, is non-hygroscopic, and is easy to _____

What are some disadvantages to aluminum interspace material? It absorbs the primary beam at _____ kVp.

What are some advantages to plastic interspace material? It has less absorption of the primary beam at _____ kVp.

What are some disadvantages of plastic interspace material? Gridlines are more apparent and it is hygroscopic, meaning it absorbs _____

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Exposures chapter 22

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