WEEK 6---RADIOGRAPHIC TECHNIQUE Flashcards
Basic X-ray Appearance
5 Radiographic densities Air = BLACK Fat = DARK GRAY Water = LIGHT GRAY Bone= DARK WHITE Metal= REALLY WHITE
SEE SLIDE 8
Basic X-ray Appearance
•The more ________something is, the more x-rays are needed to penetrate it.
•The more of something there is, the more x-rays are needed to penetrate it
.
dense
Basic X-ray Appearance
•The Optical Density of an image is how ______ the overall image is.
•The more exposure, the_________ the image.
•The less exposure, the__________ the image.
•This is primarily controlled by the mAs
–But is also affected by the kVp
.
dark
DARKER
LIGHTER
Basic X- ray Appearance
- The _________ of an image is how many shades of grey there are.
- High contrast has _______ shades of grey. TOO WHITE
- Low contrast has _______ shades of grey. TOO GRAY
- This is primarily controlled by the kVp
contrast
few
many
Exposure Factors X 4
Exposure factors are a list of factors that are able to be changed by the operator (US) for any given exposure and which influence the_________ and quality (energy) of the x-ray beam.
- mA
- Exposure Time
- kVp
- Distance
quantity
A change in either the mA or time will result in
a direct change in the _________. Neither will affect the contrast of the image.
exposure
Exposure Factors
•The mAs is_______ proportional to the x- ray quantity,
and will only affect the Optical Density.
directly
Exposure Factors
•kVp is another factor that will affect the optical density of an image.
•We said that raising the kVp by 15% is the equivalent of
____________ the # of x-rays.
–This is known as the __________
SEE SLIDE 25…HIGHER kVP = DARKER THE XRAY
doubling
15% RULE
Exposure Factors
• In addition to altering the optical density, the kVp
will also affect the ____________
.• The kVp is __________ related to the contrast.
–Contrast = 1/kVp
–The __________ the kVp the lower the contrast, which results in MORE shades of gray.
–The________ the kVp the higher the contrast, which
results in FEWER shades of gray.
CONTRAST
inversely
higher
lower
So why does the kVp affect the contrast?
- At low energies, the x-ray beam will penetrate soft
tissues, but still be stopped by ______.
a –This results in a high absorption differential - As the energy of the beam increases, more x-rays will penetrate the bone.
a. This results in a ________ absorption differential.
bone
lower
Exposure Factors
The Source to Image-Receptor Distance (SID) refers to the _______ from the anode (x-ray source) to the image receptor
distance
Exposure Factors
How does the distance (SID) affect the exposure?
- It is _______ proportional to the square of the distance.
- The distance (SID) does NOT affect the image contrast
inversely
Imaging System Characteristics
There are 3 main factors that change from system to system, but generally have limited ability to be altered for individual exposures.
1–Focal-Spot ______
2–___________
3–High-Voltage Generation
Size
Filtration
Filtration
- The technologist has NO control over the amount of inherent filtration and only limited control of the added filtration.
- The two main purposes of using filtration are to
________________________________
and to INCREASE the beam penetrability
DECREASE PATIENT RADIATION DOSE
Effect of ADDED Filtration
- ___________ filtration absorbs low energy x-rays and allows high energy x-rays to pass through.
- Because we are INCREASING the average energy of the beam, this is referred to as ________ ___________
.
Aluminum
beam hardening
High-Voltage Generators
- The technologist __________change the wave form generated from the high-voltage output.
- Remember that as the voltage ripple decreases, the ability to produce higher energy and higher quantity
x-rays ____________.
cannot
increases.
Patient Factors •The patient’s size, shape and physical condition greatly influence the required radiographic technique. •The general size and shape of a patient is called \_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_\_ . Radiographic technique charts are based on the \_\_\_\_\_\_\_\_\_\_\_ patient.
body habitus
sthenic
Patient Factors
- The thicker the patient, the more radiation is
required to penetrate the patient. - The technologist must use calipers to_______the ___________ of the anatomy that is being
irradiated. - Patient thickness should not be guessed!
measure
thickness
Image Quality Factors
Sharpness of image detail is measured
by:
_______________________.
spatial resolution
Focal Spot Size
- Most x-ray tubes are equipped with two focal-spot sizes. (Each relating to a specific filament)
- Changing the focal spot size for a given kVp/mAs
setting does not change the x-ray quantity or energy - The_______ focal spot is for fine-detail radiography in which the quantity of x-rays needed is low. (extremities)
- The________ focal spot is for most other radiographic views, when the quantity of x- rays needed is high.
(spine, abdomen)
small
large
Image Quality Factors
The smaller the focal spot size, the ___________ the
image.
The greater the SID the _____________ the image
sharper
sharper
SID (Source to Image Receptor Distance)
- Having a short SID increases the x-ray beam _______ which is directly linked to optical density.
- But the closer you get to the image receptor, the more focal spot ______ and magnification you get.
intensity,
blur
Image Quality Factors
The Object to Image-Receptor Distance (OID) refers to the distance from the ________being x-rayed to Image Receptor.
object (patient)
Image Quality Factors
- The SMALLER the FOCAL SPOT SIZE , the sharper theimage.
- The GREATER the SID the sharper the image.
- The SMALLER the OID the sharper the image.
KNOW THESE
OID (Object to Image Receptor Distance)
- The OID does NOT affect the optical density.
- It primarily affects the sharpness of the image.
- As a general rule, the object should always be as close to the image receptor as possible to reduce focal spot ______ and magnification
blur
Image Quality Factors
_________________–is the misrepresentation of object size and shape on the radiographic image.
- Poor alignment of the image receptor and the x-ray tube can result in _____________ of the image.
- Poor alignment of the anatomical part can result
in ______________________ of the image
.
DISTORTION
elongation
foreshortening
Image Quality Factors
_______ objects have an inherently greater OID and are distorted more than thin objects
Thick
