Image Receptor Exposure (Ch. 26)

Density

The overall degree of blackening on the film

Density must be within human visibility which is an optical density of ___ - ____ optical density units

.25 - 2.5

Density is measured with a _____

densitometer

With the advances of computers in Radiography two new terms describe IR exposure?

1. brightness

2. window level

Brightness

Lightness and darkness of the image on the monitor; controlled by LUT

Window level

Digital process that produces changes in brightness

Histogram

Graphic representation of the Exposure to the IR

IR exposure must be evaluated using the target ______

exposure index value

Insufficient Quantity of x-ray photons results in ________ or ________

quantum noise or quantum mottle

Factors affecting density/ IR exposure: mAs or milliamerperage seconds is ______

Primary influencer

mAs and exposure are _____ proportional to one another

Directly

mAs increases, exposure increase; therefore, IR exposure ______

Increases

mAs controls the _____ of x-rays reaching the image receptor

quantity

When using the “reciprocity law” will density change on the radiograph?

As long as the mAs is constant, any combination of mAs and exposure time values will create the same IR exposure

mA and time have a _____ relationship when maintaining radiographic exposure

Direct

30% Rule

A minimum change in necessary to see a visible or slight change on the radiograph

Rule of Thumb

To see a significant change on the radiograph mAs must be doubled or cut to 1/2

kVp controls the ____ of the x-ray photons produced at the anode

Energy

kVp controls the intensity of the beam which will affect _____ when all other factors remain the same

IR exposure

Using kVp will change IR exposure, but it will also change your ______ level

Subject contrast

15% Rule

A 15% increase kVp causes a doubling of exposure to the IR. A 15% decrease in kVp causes the exposure to be cut to 1/2

You must adjust ____ in addition to the kVp in order to maintain IR exposure on the image

mAs

X-ray generators are either:

Single phase or high frequency

The total number of higher energy photons in the x-ray tube emission spectrum is controlled by the amount of ____ in the waveform

Ripple

A single phase, two pulse unit will have lower average photon energy than a high frequency, because of this it produces less _____ on the radiograph

Exposure

Formula used to compensate for the change in IR exposure

mAs x conversion factor

There is ____ effect on IR exposure when using a large or small focal spot size

No

The _____ alters the intensity of radiation and alters IR exposure on the anode and cathode end of the tube

Anode heel effect

The image exposure will always be greater on the ____ end of the tube

Cathode

A ____ angle on the anode will have a more significant effect on the anode heel effect

Smaller

Always place the ______ at the cathode end

Thicker body part

SID will alter the ____ of the beam thus affecting IR exposure

Intensity

Inverse Square Law finds change in?

• intensity of the beam

• IR exposure

• dose

A change in the ____ is needed in order to compensate for a change in the distance

mAs

Exposure Maintenance Formula

Used to maintain IR exposure when we change distances (SID) and need a new mAs

IR exposure will ____ when any filter is used

decrease

An ____ in collimation (beam restriction) will decrease the IR exposure on the image

increase

By reducing the beam, it ____ the number of photons available in turn reducing the amount of scatter radiation which will ____ the overall IR exposure on the radiograph

Reduce

The amount of attenuation is dependent on the ____ and ____ of tissue being radiographed

Thickness, type

Tissue type is affect by ____ and the ____ of the tissue (how tightly packed)

Atomic number, density

Muscle is ___ to penetrate than fat

Harder

Contrast media is more ____ to penetrate

Difficult

Radiopaque

Difficult for x-ray beam to penetrate (ex. barium or iodine) will decrease IR exposure on the radiograph

Radiolucent

Easy to penetrate (ex. air or carbon dioxide) will increase IR exposure on the radiograph

Pathology can have either an ____ or ____ condition

Additive, destructive

Additive Diseases

Have increased attenuation, decrease in IR exposure

Destructive Diseases

Have decreased attenuation, increase in IR exposure

Casting material will affect ____ since it will affect the thickness of the anatomical part

Technique

Severe angles over ____ cause an ‘increase’ in part thickness

15 degrees

Grids absorb scatter which will affect ______

IR exposure

A 12:1 grid will have a greater effect on IR exposure (______) when compared to a 5:1 grid using the same technique

Decrease

More technique is needed for the 12:1 over then 5:1 grid to achieve the same amount of ____ on the radiograph

Density

GCF Conversion

GCF1/GCF2 = mAs1/mAs2

Grid Replacement Software

Digital post-processing algorithm that removes secondary scatter radiation information from the image

Both film and ____ will affect density/IR exposure

IRS

As the relative speed number _____ the amount of exposure needed is decreased

Increases

RS Conversion

mAs1/mAs2 = RS2/RS1

Digital systems use ____ to provide information regarding the exposure to the IR

Exposure indicators

Digital systems exhibit a wide _____

dynamic range

Digital systems create a _____ response to the x-ray exposure

linear

A linear response gives digital system an increased _____ over film/screen systems

Exposure latitude

Digital systems process the image after exposure and _____ the exposure into the visible range

Rescale

Appropriate ___ must still be selected with digital because it directly affects the amount of information the IR passes to the post-processing system

mAs

Increase mAs

+

Decrease mAs

-

Increase kVp

+

Decrease kVp

-

Increase filtration

-

Decrease filtration

+

Increase SID

-

Decrease SID

+

Increase patient thickness

-

Decrease patient thickness

+

Increase collimation/beam restriction

-

Decrease collimation/beam restriction

+

Increase grid ratio

-

Decrease grid ratio

+

Increasing # of pulses in generator waveform

+

Decreasing # of pulses in generator waveform

-

Using radiolucent contrast media

+

Using Radiopaque contrast media

-

Additive pathological conditions

-

Destructive pathological conditions

+