RT204 - Beam Restrictors and Film Processing

Wetting

• Swells the emulsion to permit subsequent chemical penetration

• Manual: 15s

• Automatic: —

Developing

• Produces a visible image from the latent image

• Manual: 5mins

• Automatic: 22s

Rinsing in stop bath

• Terminates development and removes excess chemical from emulsion

• Manual: 30s

• Automatic: —

Fixing

• Removes remaining silver halide from the emulsion and hardens gelatin

• Manual: 15min

• Automatic: 22s

Washing

• Removes excess chemicals

• Manual: 20mins

• Automatic: 20s

Drying

• Manual: 30mins

• Automatic: 26s

• Removes water and prepares radiograph for viewing

Sequence of events in processing a radiograph

• Wetting

• Developing

• Rinsing in stop bath

• Fixing

• Washing

• Drying

components of the fixer and their functions

• Activator

• Fixing agent

• Hardener

• Preservative

• Buffer sequestering agent

• Solvent

Activator

• Acetic acid

• Neutralizes the developer and stops its action

Fixing agent

• Ammonium thiosulfate

• Removes underdeveloped silver bromine emulsion

Hardener

• Potassium alum

• Stiffens and shrinks emulsion

Preservative

• Sodium sulfite

• Maintains Chemical Balance

Buffer sequestering agent

• Acetate boric acids and salts

• maintains proper pH removes aluminum ions

Solvent

• Water

• Dissolves other components

Radiopaque

White

Radiolucent

Black

Transmission or Attenuation

• X-ray photons, when interacting with matter, result in

• absorbed or scattered

Scatter radiation

• These are produced during a Compton interaction

• It places exposures on the image receptor that are unrelated to patient anatomy

kVp and Volume of irradiated tissue

Two major factors affect the amount and energy of scatter radiation

exiting the patient

Beam Restriction

Minimizing the amount of scatter radiation can be accomplished by ____ ______ and by using grids.

Proper beam restriction

Tissue compression will keep the total amount of tissue irradiation to a minimum

BEAM-RESTRICTING DEVICES (3)

• Aperture diaphragm

• Cones/Cylinders

• Collimators

Collimator

The foremost method of restricting the primary beam field size is the use of a

device known as a

Aperture diaphragms and cones/cylinders

are also devices that were used to restrict the beam, but are not in common use today

APERTURE DIAPHRAGM

• It is the simplest of all beam-restricting devices

• It is basically lead or lead-lined metal diaphragm that is attached to the X-ray tube head

• Different diaphragms are needed to accomodate different receptor sizes and distances

CONES AND CYLINDERS

• Radiographic extension _____ and ________ are considered modifications of the aperture diaphragm

• One difficulty with using _____ is alignment

• _____ are routinely used in dental radiography

COLLIMATORS

• is the most commonly employed beam restrictor in radiography

• It consists of sets of lead shutters at right angles to one another that move in opposing pairs, and moves symmetrically from the center of the field

• Reduces the patient radiation dose and improves contrast resolution

positive beam-limiting device, or simply, positive beam limitation (PBL)

A type of Automatic collimators

Automatic Collimator

Limits the size and the shape of the primary beam to the size and shape of the image receptor

upper shutters

are responsible for reducing the amount of off-focus radiation

Off-focus radiation

originates within the x-ray tube but not at the focal spot of the tube

Penumbra

It is a type of geometric unsharpness around the periphery of the image (edge unsharpness)

Bottom shutters

reduce penumbra along the periphery of the beam

Increase Collimation

• Decrease filed size

• Decrease scatter radiation

• Increase contrast resolution

• Decrease exposure reaching the IR

• Decrease patient dose

TRUE

X-ray source > Patient > Latent image > Development > Fixing

Latent Image

is the unobservable image stored in the film; it is made manifest by processing

Film processing: Development

It is a stage of processing during which the latent image is converted to a visible image

Film Processing: Fixing

The use of Silver halide that was not exposed to radiation is the process of clearing it from the emulsion and hardening the emulsion to preserve the image

Xray tube

what is the name of this?

Primary beam

what is this?

Image receptor

what is this?

• Large field size

• Increased patient thickness

what is this?

• 
  

what is this?

Beam Restriction and Patient dose

As the _____ _______ or the collimation increases, the field size and patient dose decrease. As the ______ _______ or collimation decreases, the field size and patient dose increase

Appropriate Beam Restriction

In performing a radiographic examination, the radiographer should be aware of the anatomic area of interest and limit the x-ray field size to just beyond this area. Collimating to the appropriate field size is a basic method for protecting patients from unnecessary exposure

Increases

when scatter radiation _______ as the xray beam field size inceases

Diaphragm

what image is this?

Cylinder

what image is this?

Collimator

what image is this?

Relationship: Collimation and Exposure to the IR

Collimation increases, exposure to the IR decreases: as the collimation decreases, while exposure to the IR increases

Relationship: Collimation and Radiographic Contrast

As collimation increases, the quantity of scatter radiation decreases and radiographic contrast increases: as collimation decreases the quantity of scatter radiation increases and radiographic contrast decreases

Relationship: Collimation and Scatter Radiation

As the collimation increases, the field size and quantity of scatter radiation decreases, as collimation decreases the field size and quantity of scatter radiation increases