radiographic quality Flashcards
- A window into the human body
- Formed by the imaging modalities that use various forms of radiation & energy
to open the body to visualization
medical image
- Refers to the fidelity with which the anatomical structure that is under
examination is imaged
on the
radiograph.
Radiographic Quality (Image Quality)
degree of exactness
fidelity
ability to image two separate objects and visually distinguish one from the other.
resolution
refers to the ability to image small objects that have high subject contrast such as a bone-soft tissue interface, a breast microcalcification, or a calcified lung nodule.
spatial resolution
ability to distinguish anatomical structures of similar subject contrast such as liver-spleen and gray matter-white matter. The actual size of objects that can be imaged is always smaller under conditions of high subject contrast than under conditions of low subject contrast.
contrast resolution
random fluctuation in the Optical Density of the image.
noise
FOUR COMPONENTS OF RADIOGRAPHIC NOISE:
film graininess
structure mottle
quantum mottle
scatter radiation
- refers to the distribution in size and space of silver halide grains in the emulsion.
- Always present in radiographic film (exposed)
- Silver halide crystals
Film Graininess
- is similar to film graininess, however, it refers to the phosphor of the radiographic intensifying screen.
- Phosphor crystals
Structure Mottle
- is a principal contributor to radiographic noise in man radiographic imaging procedures.
- refers to the random nature by which
x-rays interact with the image receptor - Principal contributor to radiographic
noise
Quantum Mottle
pocket of energy
quanta
- this is x-ray radiation that interacts with atoms in the patient’s body and is deflected from its original path.
- Secondary radiation
Scatter Radiation
- refers to the sensitivity of an intensifying screen to X-rays. It essentially reflects how much X-ray radiation is needed to create a bright enough image on the X-ray film.
- It influences the radiographic resolution
SPEED
- These screens have a higher sensitivity to X-rays.
high-speed screens
- They require a lower X-ray dose to create a bright enough image on the film. This is crucial to minimize radiation exposure to patients, especially for sensitive individuals or frequent X-ray examinations.
high-speed screens
- These screens have a lower sensitivity to X-rays.
low-speed screens
- They require a higher X-ray dose to achieve the same image brightness as high-speed screens.
low-speed screens
They often produce sharper images with finer details due to less light scattering within the phosphor layer.
low-speed screens
They may have slightly reduced image sharpness compared to slower screens
high-speed screens
PRINCIPAL FACTORS THAT MAY AFFECT RADIOGRAPHIC QUALITY
film factors, geographic factors, subject factors
Film Factors
(characteristic curve)
- Density
- Contrast
- Speed
- Latitude
Film factors (Processing)
- Time
- Temperature
Geometric Factors
- Distortion
- Magnification
- Blur
Subject Factors
(contrast)
- Thickness
- Density
- Atomic number.
- Motion
characteristic curve
toe region
straight-line region
shoulder region
initial slowly increasing portion of the curve, the film has a low sensitivity to X-ray exposures, resulting in initial changes in density.
toe region
middle portion of the curve with the steepest slope. This is the ideal exposure range where the film demonstrates a linear relationship between exposure and density, allowing for good contrast in the final film.
straight-line region
final portion of the curve where the density increases rapidly with minimal further increase in exposure. This portion represents the overexposure of the film, resulting in a loss of detail in the brighter areas of the image.
shoulder region
Photographic Quality
- Density
- Contrast
Geometric Quality
- Detail
- Distortion
- Regarded as the general blackening of the radiograph
- It is also the accumulation of black metallic silver after subsequent processing.
- It represents how attenuated by the radiation was the anatomical part.
radiographic density
Five major groups of tissue density
aerated tissue
fatty tissue
bone
metal
water
● Aerated tissue (filled with air)
dark/black
● Fatty tissue
- Slightly gray
● Water
- Gray
bone
white
metal
white
measurement of the quantity of radiation absorbed by the intensifying screen, converted to light and transmitted to the film.
radiographic density
- difference in density between two structures
- The presence of _ means that different density levels are visible on the radiograph.
radiographic contrast
Is the result of attenuation and the differential absorption of tissue.
radiographic contrast
types of contrast
subject contrast/film contrast
SUBJECT / TISSUE CONTRAST
(influenced by the ff.)
- Patient size
- Tissue type
- Health Status
- Attenuation properties of tissue.
- When tissue type is very dense
- X-rays have a difficult time penetrating.
- High attenuation rate
High differential absorption
- Soft tissue
- Low attenuation properties.
Low differential absorption
refers to the number of different densities present on the radiograph
scale
- High kVp
- “Lower-contrast”
- Preferred in lung
examinations
Long Scale Contrast
- “High-contrast”
- Low kVp
- Fewer density
Short Scale contrast
- Mixture of black, gray, and white.
Moderate Contrast
- refers to the range of material thickness that can be imaged. This means that more areas of different thicknesses will be visible in the image
- range of exposure techniques that will produce an acceptable image
- Inversely proportional to contrast
latitude
determined by the inherent contrast of the film.
film latitude
film response to variations in exposure.
film contrast
Refers to the range of exposure factors (mAs/kV) that will produce an acceptable film.
exposure latitude
wide latitude or low contrast film.
high kv
narrow latitude or high contrast film.
low kv
- It is the actual or visible detail of the part of interest recorded in the film.
- Refers to how well one can see small structures on the radiograph
recorded detail
sharpness of detail
definition
play a significant role in determining the quality of a radiographic image.
They influence factors like magnification, distortion, and sharpness, all of which can impact the diagnostic value of the image.
geometric factors
geometric factors
• Source-to-Image Receptor Distance (SID)
• Object-to-Image Receptor Distance (OID)
• Angulation
• Collimation
• Focal spot size
misinterpretation of size and/or shape of the object
distortion
two types of distortion
- Size Distortion (Magnification)
- Shape Distortion (Magnification)
- To reduce magnification, place the object as near the film as possible.
- Direct magnification
- Directly proportional to magnification
Object-to-Image Receptor (OID)
Inversely proportional to magnification
Source-to-Image Receptor Distance (SID
indicates the amount of magnification of the object.
magnification factor
• Occurs whenever the OID is greater than zero
• All objects on the radiograph are larger than the actual size.
• It is caused by the divergence (spreading out) of the x-ray beam as it moves away from the target (x-ray tube ) where the x-ray are produced
• _ of an object positioned off the central rays is the same as that of an object on the central ray if th objects are in the same plane.
magnification
Size of the area on the anode where x-rays are producing
focal spot size
SHAPE DISTORTION
Factors:
• Tube Angulation
• Image Receptor Angulation
• Part Angulation
- When a structure appears shorter and thicker than its actual shape on the X-ray image.
FORESHORTENING
When a structure appears longer and thinner than its actual shape on the X-ray image.
ELONGATION
