Bhc Rad Fall - Imaging Unit 1

(mAs1/mAs2)=(SID1/SID2)^2

mAs2=mAs1 * (SID2/SID1)^2

mAs2=mAs1 * (kVp1/kVp2) * (RS1/RS2) * (SID2/SID2)^2

(SID1/SOD1)= (SID2/SOD2)

(I1/I2)=(SID2/SID1)^2

Measure of quantity of electrical current flowing through a circuit.

A rate representing number of electrons passing through a point in the circuit per second.

- Higer mA=more electrons=more x-rays

Light is equal to the product of the intensity of the light and the duration of the exposure.

mAs is directly proportional to radiographic density.

Either mA (quantity), s (time), or both may be changed.

The degree of blackness in an area of the image

The intensity of the beam of radiation which penetrated the patient and struck the image receptor.

Density will be doubled.

30%

50%

Quantum Mottle

The measurement of electrical force of pressure behind a current of electricity.

kV is controlled by the autotransformer in the high-voltage circuit

The quality or energy level of the electrons flowing through the circuit.

False - The average beam energy will be about 1/3 of the kVp

Both because high energy electrons may result in multiple interactions and produce multiple photons.

- Higher kV will affect both, but mAs is the primary factor affecting quantity.

A change in penetration will directly affect the gray scale (contrast) of the image.

Note: kVp will directly affect contrast primarily, and as kVp is increasingly raised, it will also affect the blackness (density) of the image.

The size, shape, and x-ray attenuating characteristics of the subject being examined and the energy of the beam.

Contrast that inherent to the film and influenced by the processing.

Inversely.

- High contrast = Short scale

- Low contrast = Long scale

False - Higher energy x-rays result in a loss of photoelectric interaciotns, leaving high proportions of Compton interactions, resulting in scattered x-rays.

Provide penetration through the patient's tissue.

Fog or noise

Doubling mAs = 15% increase to kVp

Double mAs and cut kVp by 15%

Base, adhesive, emulsion, and supercoat

Supercoat, emulsion, adhesive, base, adhesive, emulsion, and supercoat.

Invisible change to silver halide crystals in the film emulsion resulting from interaction with light or x-ray photons.

During processing

Sensitivity specks

- X-ray or light photons interact with atoms in the crystals.

- Electrons are freed

- The free electrons are attracted to and caught by the sensitivity specks which then have a negative charge, joining positive silver ions to form atomic silver.

The intensifying screen gives off light photons when struck by x-ray photons

Speed

Contrast

Latitude

Recorded Detail

How fast blackening occurs during exposure.

Larger crystals = Faster speed

- Produce larger black area on radiograph

Higher speed = Lower quality (more quantum mottle)

Radiographic Contrast = Subject Contrast + Film Contrast

High - Relatively even grain size

Low - Range of grain sizes.

The range of exposure that can be used with film to produce diagnostically useful densities.

Wide - Exposed over a variety of mAs values and display more shades of gray.

Narrow - Smaller range of mAs may be used. Differentiate between differences in tissue densities better. Higher contrast and fewer shades of gray.

The extent to which small anatomical differences can be recorded on film.

Better sharpness, or higher resolution

Smaller crystals = smaller image grain = more detail can be seen

False. They are inversely related.

Higher speed = Lower recorded detail

Calcium Tungstate - Blue and blue-violet

Rare Earth - UV, blue, green and red

Blue and violet.

Note: Dyes are added to sensitize it to other colors of light.

Improper storage or handling of film and/or film cassettes

<1%

X-ray photons are converted to light photons which expose the film.

Lower patient dose.

Higher speed = Lower quality

Any material that emits light in response to outside stimulation.

Emitted visible light.

Screen Speed

Image Noise

Spatial Resolution

Relative number that describes how efficient x-rays are converted to usable light.

Par speed calcium tungstate.

100

The ratio of the exposure required to produce the same OD with a screen in comparison to that required to produce the same OD w/o a screen.

Wetting

Developing

Stop Bath

Fixing

Washing

Drying

Developers

Hardener

Stops development and permanently fixes the image to the film.

Activator

- Neutralizes the developer and stops the action.

Fixer

Transport

Temperature-Control

Circulation

Replenishment

Dryer

Electrical

The study of the relationship between intensity of exposure of the film and the blackness after processing.

- Exposure of the film

- Percentage of the light transmitted through the processed film

The relationship between Optical Density and radiation exposure.

As a characteristic curve.

AKA:

- D log E curve

- Sensitometric Curve

- H&D Curve (Hurter and Driffield)

Toe - Low levels

Straight-Line Portion - Intermediate levels

Shoulder - High levels

False

Inherent OD in the film

Density resulting in inadvertent exposure of the film during storage, improper processing or chemical contamination

0.25 - 2.5

IR contrast and Subject contrast

Straight-line portion

The ability of an IR to respond to a low-x-ray exposure

As the range of exposures over which the IR responds OD's in the diagnostically useful range

Wide Latitude = Long Scale = Low Contrast

Narrow Latitude = Short Scale = High Contrast

The range or number of different densities present in the image.

Any unwanted, useless info recorded which obscures the visibility of the desired image

The ration of differences between two adjacent densities on the image

A form of noise.

- A veil of useless density covering portions of the desired image

The abruptness with which the edges of an image stop.

- The lack of penumbra in an image

Lack of sharpness, or the presence of penumbra in an image

A partial shadow at the edges of an image, causing the transition into the adjacent density to be gradual rather than abrupt

The difference in size of a real object and the size of its umbral quality on the radiograph

Difference between the shape of a real object and the shape of its image on the radiography.

- Can be elongation or foreshortening

Ability to distinguish adjacent details as being separate from each other.

True

Line pair per millimeter (lp/mm)

Smaller Focal Spot = Sharper Recorded Detail

- Inversely proportional

Smaller Focal Spot = Less blur or penumbra

- Directly proportional

Intensity of beam is greater towards cathode end of tube.

Anatomical position of greater tissue density should be placed at cathode end of tube.

From focal spot to the film or IR

Sharpness of recorded detail increases as SID increases.

- Directly proportional

Increased OID = Increased magnification

Increased SID = Decreased magnification

To decrease magnification of the heart resulting from heart-to-IR OID.

False. SID will only affect magnification.

Note: Other factors may cause distortion

Increased SID = Reduced image density.

Inverse Square Law

(I1/I2)=(SID2/SID1)^2

By a directly proportionate change in mAs.

- Changes in SID alter intensity, not penetrability of the x-ray beam

Density Maintenance Formula or Direct Square Law

(mAs1/mAs2) = (SID1/SID2)^2

mAs2 = mAs1 * (New Distance/Old Distance)^2 * (New Grid/Old Grid) *(Old kVp Factor/New kVp Factor) * (Old F/S Speed/New F/S Speed

- Increased penumbra

- Increased magnification

- Increased distortion if the part is misaligned.

- Decreased density (scatter radiation produced w/i PT diverges more and loses intensity before reaching film.)

- Increased contrast (Scatter radiation reaching film is reduced. Primary rays remain at same intensity. Air Gap Technique)

SID:OID Ratio

- Magnification and sharpness are both dependent on this ratio.

- As long as ratio stays the same, there is no change in part magnification.

MF = (Image Size/Object Size) * (SOD/SID)

Object Size = Image Size * (SOD/SID)

- Decreased sharpness due to expanding penumbra at image edges. Most destructive effect.

- Decreased contrast by superimposition of various densities

- No direct relation to overall image density, shape distortion or magnification.