Rt 204: Radiographic Density

Radiographic Density

• the opacity of the radiograph, also described as the amount of blackening on the film

• The traditional definition of density was the degree of overall blackening from the black metallic silver deposited in the emulsion of film

• Decreased

Tissue density

• Decreased

• Inversely proportional

Increased mAs

kVp produces scatter radiation, then scatter radiation produces fog, fog is referred as unwanted densities on the film. What happens to density?

base

What is green?

Protective layer

What is light blue?

Phosphor

What is red?

Film emulsion

What is dark blue?

Fluorescence or light photons

What is yellow?

xray photon

What is orange?

Gelatin binder

What is 1?

Silver halide crystals in suspension

What is 2?

Celluloid base

What is 3?

Physical Handling protective back coat

What is 4?

• gelatin binder

• Silver halide crystals in suspension

• celluloid base

• Physical handling back coat

What are the basic structure of film?

Amount of exposure

reaching the film determines the amount of density on the finished radiograph

View box

• It is a wall-mounted or portable device with fluorescent light bulbs that is covered with white transparent material

• The light can be seen coming through in some areas where less density (blackening) is present, and some areas are found with little or no density (clear/white). Little or no light will come through in areas with more density

TRUE

• Information is recorded on an image that is overexposed but may not exist at all on a radiograph that is underexposed

• The underexposed image has not received the information in the first place and is not capable of being manipulated to reveal details that were never recorded

If information is recorded on an image, but may not exist at all on a radiograph that is underexposed. What would be the exposure be?

Overexposed image

Overexposed Image

Whenever a choice must be made between excess and insufficient density, the wise decision is always the choice that will produce the?

Underexposed Image

If image has not received the information in the first place and is not capable of being manipulated to reveal details that were never recorded

Hot lamps

it is a high intensity viewing device used in film radiography to emit a concentrated beam of strong enough to penetrate dense, overexposed or dark areas of a processed radiograph to reveal a hidden anatomical detail

It is a device that measures the percentage of light that has been transmitted through the film.

What is the use of densitometer?

Densitometer

It differentiates the degrees of blackening being measured by

Density unit

What is the device that measures the percentage of light that has been transmitted through the film?

Brightness

describes the concept of density as it displayed on a soft-copy monitor for digital images

Window level

describes the digital processing that produces changes in density/brightness, so it also appropriate to use when controlling image density

Density

is also described as the nature of tissue

Contrast media

are high-atomic or radio-opaque substance administered to a patient to alter the absorption rate of xray photons or radiofrequency signals on the surrounding tissues

Reduction of intesity

Define attenuation?

Total absorption

What is the total energy that is fully deposited into a medium?

yes, air is a classified as a negative contrast medium, because is has a low atomic number and a low physical density relative to surrounding body tissues

Can contrast media be administered in air?

Attenuation

• means a reduction in the x-ray intensity due to absorption and scattering

• Areas of the beam with almost complete attenuation produce very little radiographic density and the parts of the beam with very little attenuation procude areas of greater optical density

Window glass

Transparent

Frosted glass

Translucent

Black glass

Opaque

FALSE, ATTENUATION

Remnant Radiation of the beam causes different density levels to be present on the radiograph (T or F, & correct answer if F)

Primary Controlling Factor

mAs

mAs

It is the amount of electrons hitting the anode controlled by?

X-ray Quantity

Other word of mAs?

X-ray Quality

Other word for kVp?

kVp

It is the energy of electrons hitting the anode

• Directly proportional to mAs

• mAs is used as the primary controller

Since density is primarily determined by the amount of exposure a receptor receives, and since exposure is _______________, _________________ of image receptor exposure and film density

30%

Minimum change necessary to cause visible shift in film density if

Double or halves

The general rule of thumb for mAs changes is to make adjustments in increments or

• kVp

• Focal Spot Size

• Anode Heel Effect

• Distance

• Filtration

• Beam Restriction/Collimation

• Grids

• Film-screens speed

• Anatomy/Pathology

• Film processing

what are the types of influencing factors?

Film Processing

The condition of the film processing solutions can dramatically alter film density

• Thickness of the part

• Tissue Density

• Anatomic Number

3 Things to remember under Anatomy & Pathology

Anatomy/pathology

Because the patient is the prime attenuator of the beam, the anatomical part being examined has a great deal of influence on image receptor exposure and film density

Additive Pathology

will appear with less radiographic density

Destructive Pathology

will appear with increased radiographic density

Additive Pathology

Destructive pathology

TRUE

In Anatomy/Pathology there is a inverse relationship between tissue density and radiographic density

screen-speed/ relative speed

increases, density will increase; less exposure is needed to keep density

Relative Speed (RS) numbers

are the most useful parameters for intensifying screen combinations

Intensifying Screens

increase density on the film by intensifying the action of x-rays

Film Types

that contain increased amounts of silver halide crystals will increase density

• Intensifying Screens

• Relative Speed (RS) numbers

• screen-speed/ relative speed

What are the film types?

ID Window

answer for 1?

cassette

answer for 2?

Screens

answer for 3?

Light-tight seal

Answer for 4?

Film

Answer for 5?

Grids

• Absorbs scatter radiation

• which would otherwise add exposure to the image receptor and density to the film

• Scatter Clean up

• Increase Contrast

Recommend to increase mAs instead

under grids: Because the primary purpose of a grid is the improvement of contrast, compensating for film density changes by varying the kVp is not recommended.

Beam Restriction/Collimation

This devices are used to restrict the beam field size and the actual area exposed on the patient

therefore, less density

As field size decrease, smaller areas are exposed and less scatter radiation.

Filtration

Filters are thin aluminum or metal devices located between the x- ray tube and beam restriction device. The purpose of filtration is to absorb the low-energy x-ray photons in the beam as they exit the tube

Air Gap Technique

• OID also alters the amount of density reaching the film. This is done through the

• is an alternative to the use of a radiographic grid. It purposely increases OID to allow scatter to exit the patient and not reach the image receptor

Distance

SID alters the intensity of the beam reaching the image receptor, according to the inverse square law.

Inverse square law

states that the intensity of the x-ray beam is inversely proportional to the sqaure of the distance from the source

INCREASE SID by 2

= DECREASE Density/Intensity by 4

what is the formula of inverse square law?

Positive Anode Negative Cathode

what is PANC?

Anode heel Effect

• alters the intensity of radiation and therefore the density, between the anode and cathode ends of the x-ray tube. The density produced on the cathode end is more prominent

• The anode heel effect may be converted to an advantage in examinations of objects with greater subject density at one end than at another.

Advantage

When the anode heel effect becomes

apparent, it can be minimized or

converted to an _____?

Focal Spot Size

Larger focal spots utilize a greater incident electron stream than small focal spots. Therefore, it requires increase mAs

• Effective Focal Spot

• Large

• Penumbra

• Increased density

what does this image shows?

• Effective Focal Spot

• Small

• Decrease mAs

what does the image shows?

Moderate kVp

Describe the image?

High kVp

Describe the image?

Fog is increased

unwanted density on the radiograph. Its main source is scatter radiation

• increase in image fog

• more density

An increase in kVp also increases scatter radiation. Scatter radiation results to ______________. Image fog adds to _________ on the film

= Decrease mAs by half

Increase kVp 15%

= Increase mAs by double

Decrease kVp by 15%

Decrease by 15%

If mAs is doubled, how should kVp be changed in order to maintain the same exposure to the IR?

• Increase in kVp by 15% = X2 Density (doubled)

• A decrease in kVp by 15% = ½ Density (halved)

What is the 15% kVp Rules?

15 % rule

is used to predict changes in density levels with kVp

quantity

• Additionally, because of the increase in energy, there is also increase in penetrability, intensity and _______?

• The relationship between kVp and radiographic density is not one of proportion

• kVp

• Focal Spot Size

• Anode Heel Effect

• Distance

• Filtration

• Beam Restriction/Collimation

• Grids

• Film-screen speed

• Anatomy/Pathology

• film-Processing

Influencing Factors

mAs

Controlling factors

• Radiographic

• Tissue

Density

• View box

• Densitometer

Tools to help assess

Latent image formation & processing: Unexposed State

silver halide crystals reside suspended within the gelatin binder without light energy interaction

Latent image formation & processing: Exposure

Light photons from the intensifying screen interacts with the silver halide crystals in the emulsion, creating a latent image center

Latent image formation & processing: Development

Chemical processing converts the exposed silver halide crystals containing latent image centers into metallic silver grains (Ag grain), while unexposed or soluble silver complexes (soluble Ag complex) remains distinct

• increased processing/Immersion time

• Increased solution temperature

• Faster replenishment rate

Film density increases with?

Latent image formation & processing: Fixing & Final Image

Unexposed silver halide crystals and soluble complexes are dissolved and washed away during fixing, leaving the dark metallic silver grains embedded in the gelatin