XR202 Exposure

Darkness

Range of gray shades

Definition and resolution

Size and shape

• Photographic Properties :
• Density and Contrast
• Geometric Properties :
• Distortion and Magnification

• Overall blackness of total image
• Controlled by mAs (quantity of radiation)
• Directly proportional to amount of mA used and length of time (more rads = more blackness/density)
• mA x S = mAs

• mA
• mAs
• S
• SID

Quantity of rads doubled

Quantity of rads doubled

• mA
• Time
• kVp
• SID (source to image distance)

• Heel Effect
• Tube Alignment
• Film and Body Part
• OFD (object to film distance)
• Tissue Thickness
• Screen Selection
• Collimation and Beam Filters
• Fog
• Film Processing

• Any combo of mA x T factors that are equivalent
• mAs will produce same density

Primary control of Density

• Size of focal spot
• Amount of time needed

• Primary factor
• Controlling recorder detail (geometric property)

• Sharper detail
• 300mA or less

• Less Detail
• Use if object greater than 12cm thick
• 400mA or greater

• Amount of heat tollerance
• How much a tube can handle
• mA x T x kVp

• kVp
• SID
• Heel Effect
• Processing
• Fog

• Increase penetration
• Density increases (increase scatter)
• Controlled by addition of Grid

Must have 25-30% difference

• Controls Density
• By absorbing scatter rads
• Greater exposure needed above 12cm thick object
• No Grid to Grid = needs 4x more mAs exposure

• Hight of lead strips to distance between lead strips
• Width stays constant
• Hight will change to give different ratios
• 6:1 is less efficient than 12:1
• Higher the number the better

• Intensity of radiation is inversely proportional to square of distance
• I₂ = I₁ x D₁² Divided by D₂²

• Radiation intensity diminishes along a line parallel with long axis of tube
• Intensity is stronger on Cathode side
• Align thicker body part to Cathode side

• Generalized
• Unwanted increase in density
• Makes structures dificult to see

• Foreign marks
• Unwanted marks
• (physical or chemical or light)

• Effects image detail according to size of Phosphor Crystals
• Small crystals = less blurring of image because less diffusion of light created by small crystals

Ability of crystals within film emultion to efficiently record information (Silver Halide)

• Filter beam
• Remove lower-energy rads
• Aluminum = called added filtration
• .5mm in tube as glass and oil (inherent filtration)
• Total = 2.5mm minimum filtration (inherent + added)

• Safelight = proper color filter, distance, size
• Film Age = not used past expiration date
• Chemicals = time-temp process; increase temp = increase density

Object to film distance

• Refer to Tube
• Source to Image Distance
• Target to Film Distance
• Focal Spot to Film Distance

• Increase SID = mAs times 4
• Decrease SID = mAs times .25

• Scatter effect = fog =
• Overall grayness / darkness
• Density goes up

• SID decreases = Density increases
• SID increases = Density decreases

• Every 15% increase in kVp
• Must reduce mAs by 50% (cut mAs in half)
• Every 15% decrease in kVp
• Must increase mAs by 50% (double mAs)

Reduce kVp by 7%

Reduce kVp by 15%

Increase kVp by 7%

Increase kVp by 15%

Used as light sensitive component of x-ray film

• Light
• X-rays

• Because of intensifying screens:
• Lower mA needed
• Faster exposure times

• Fluoresce (give off light)
• When hit by x-rays

• Slow (detail)
• Medium (par)
• High (fast)

Use High Speed film screen

• Upright to avoid static from weight
• Closest due dates up front

• Minimum distance 3 feet
• From work bench

• Film more sensitive after exposure
• During developement

Caused by dry air

Fixer before developer

Bends in film (finger nails)

• Web like markings
• Extreme difference in solutions

• Light leak
• Scatter x-rays
• Chemical Vapor

• Dust
• Poor storage

Recorded Detail

The intensity of radiation is inversely proportional to the square of the distance

• Without changing mAs
• Changes resolution / detail

• Calcium Tungstate
• Rare-Earth (more sensitive to light) Desireable

• In both developer and fixer
• Used to prevent oxidation

• Time kept by roller system
• Maintains proper time in each stage of process