Final Review: image Receptor Exposure Flashcards by Melissa Unknown

Two photographic properties allow detail to be seen on radio graphic images

-IR Exposure
-Contrast

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-monitor control
-not the same as density term
-window level controls

Brightness

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Window leveling

Moving mouse up and down
-up (blacker image)
Down- (whiter image)

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What is your Receptor exposure?
-mAs or kvp?

mAs

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What is your contrast?
-mAs or kvp?

kvp

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Traditional term “density” no longer applicable in digital world. What was it replaced with?

Image Receptor (IR) exposure

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Details not recorded on underexposed image is due to

Due to quantum mottle/noise

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What can eliminate excess information on overexposed image?

Digital post processing

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This happens when saturation occurs.

Over exposure

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When enough photons do not reach the IR. mAs needs to be increased.

Quantum Mottle

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Receptor exposure (mAs) + Contrast (kvp) =

Visibility of detail

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What percentage is needed in changes in mAs for visible density change?

minimum 30%

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Factors Affecting IR Exposure:

Controlling or influencing:
-mAs as controlling factor(in film)
-Multitude of influencing factors

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Make changes in doubles or halves:

15% rule
-decrease kvp by 15% and double mAs
-Increase kvp by 15% and reduce mAs by a half

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Low Contrast

-Long scale (many grays)
- increase kvp (chest xrays)
-wide window width
-wide latitude
-elephant herd

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High Contrast

-short scale (fewer grays)
-decrease kvp (hand xray)
-Narrow window width
- narrow latitude
-zebra

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what happens to contrast when you decrease kvp

increase contrast

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Intensity of radiation at given distance from point source is inversely related to the square of distance between object and source.

Inverse Square Law

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Provides technique correction for change in SID and maintains same image density/ IR Exposure

Direct Square Law

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What is being changed in these situations?
The minimum 30 percent for visible density change and making changes in doubles and halaves

Changes in mAs

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Image Noise

-Impairs diagnostic acuity
-anything unwanted on an image

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Three types of noise

-Quantum noise
-system noise
-ambient noise

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what noise is the largest contributor to total noise?

Quantum noise (controlled with mAs)

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Regarding image noise what is wanted:

High signal, low noise

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what is the primary influencing factor of IR exposure

mAs

This number helps determine how much was reached

e.i. #

Relationship between mAs and IR exposure

directly proportional

Ideal IR exposure

1 mR

a reference point

Exposure index # (e.i.#)

Combination of technical inflencing factors :

mAs kvp SID filtration grids collimation IR sensitivity Body Part Heel Effect Focal spot

Total exposure to the image receptor

Image quality

How is IR exposure best controlled by?

Controlling AEC and technique charts

AEC

Automatic Program Control

APR

Anatomically programmed radiography

increased grid ratio also increases:

patient dose

CR compared to DR

CR- higher technique needed DR- more sensitive

Is a monitor control function that can change the lightness and darkness of the image on a display monitor but it is not related to IR exposure.

Brightness

Overall blackening that is the result of black metallic silver deposited in the emulsion of film.

Density

Describes digital post processing that produces changes in brightness, so it appropriate to use when controlling the display of an image.

Window Level

Larger focal spots utilize a greater incident electron stream than small focal spots. Small focal spots can not withstand as much heat.

Focal Spot Size

Alters the intensity of radiation and therefore the IR exposure between the anode and cathode ends of the xray tube. (FAT CAT- IR exposure is always greater at the cathode end)

Anode Heel Effect

According to the inverse square law what alters the intensity of the beam reaching the IR?

SID

Relationship with Filtration and IR exposure

Inverse- IR exposure decreases when filtration increases

Restricting the beam, collimating, or reducing the primary beam field size reduces the total photons available what does this reduce overall?

Reduces the amount of scatter radiation and therefore reduces the overall IR exposure.

More matter=

More scatter

Technical factor compensation for changes in IR exposure is required only under the following circumstances:

-large anatomical part -high kilovoltage -low grid efficiency -non-grid examinations

What happens to the IR exposure when tissue thickness, average atomic number of tissue, and/or tissue density increases?

IR exposure decreases

How do you move the window width for contrast

left and right

The more efficient the grid is, how is the IR exposure effected.

The less will be the IR exposure

Grids absorb scatter so how does that affect the IR exposure

It adds exposure to the IR and density to the film

What controls the average energy of xray photons at anode target

kvp

kvp change is not recommended to control?

Image noise

Affects average energy of beam -only consider when changing from single phase to high frequency, multi-phase

Generator Configuration

When kvp is increased how does that affect quality and quantity

quality and quantity are increased

More matter= more scatter= Compton scatter which is what dose?

Occupational Dose

this number helps determine how much was reached

E.I. #

Built into processing of computer. Pre processing with digital creating picture perfect image. Compares to the image taken.

Histogram

what is the best generator

High frequency- generates more heat

What does Focal Spot Affect

ONLY Resolution does not affect contrast or receptor exposure

More pronounced with wider collimation

Anode Heel Effect

Alters intensity of beam across cathode/anode axis

Anode Heel Effect

IR exposure up to 45% greater at cathode side of beam

Anode Heel Effect

Words to describe inverse square law:

-Intensity -mR -inversely

Words to describe Direct Square Law:

-Maintain -mAs -direct

How is filtration related to Ir exposure

Inversely -Increased filtration will decrease IR exposure -Increased filtration increases average energy of beam but reduces intensity of beam (quantity)

Relationship between anatomical part and IR exposure

Inversely

How is beam restriction and IR exposure related

inversely - increased beam restriction decreases IR exposure - Reduces total amount of remnant radiation striking IR (reduced scatter and secondary)

What can impact the histogram?

Tight collimation (small field size) tight collimation works against histogram analysis and equalization

decreased field of view, increase collimation does what to the receptor exposure

decreases

what does increase filtration affect

decreases exposure. (cleans it up, more quality image)

How does the additive pathology affect the IR

Decreases density/ IR exposure

How does Destructive pathology affect the IR

Increases density/ Ir exposure

Is additive pathology radiolucent or radiopaque

radiopaque

is destructive pathology radiolucent or radiopaque

radiolucent

is barium additive or destructive

additive (increase technique)

is iodine additive or destrictive

additive (increase technique)

Is air and gas additive or destructive

destructive ( decrease technique)

what happens to Ir exposure when there is a increase in grid ratio

Decrease receptor exposure

When using positive and negative additives what needs to happen to the contrast material

Double the contrast material