Image Analysis Chapter 1 Flashcards
How do you display torso, vertebral, cranial, shoulder, and hip images?
As if the patient were standing in an upright position
How do you display AP, PA, AP-PA oblique images of the torso, vertebrae, and cranium?
Displayed as if the viewer and patient are facing one another. the right side of the patient image is the viewers left, the left side of the patient’s image is the viewers right
How to display AP/PA (Lateral Decubitus) chest and abdomen projections
Displayed as if the viewer and the patient are facing each other. Then turned to be displayed so that the side of the patient that was positioned upward when the projection as taken is upward on the displayed image.
Which exams/projections of the upper extremity will be displayed from the finger tips?
finger, wrist, and forearm
Which exams/projections of the upper extremity will be displayed from the shoulder
elbow and humerus
Which exams of the lower extremity will be displayed from the toes?
toes, AP and AP oblique foot projections
Which exams of the lower extremity will be displayed from the hip?
lateral foot, ankle, lower leg, knee, femur
What demographic requirements must be permanently photo flashed or displayed on digital display monitor of each image?
correct patient name, age or DOB, facility name, date and time
What must be included on each image to be considered a legal document in a court of law
correct lead marker from exposure. Not post processing
Why are markers placed on the IR and not on the imaging table or patient?
This placement avoids marker distortion and magnification, preventing scatter radiation from undercutting the marker and ensures that the marker will not be projected of the IR. Prevents cross contamination
Where do you place markers for an AP/PA projection of the torso, vertebrae, or cranium?
Place R or L marker laterally on the side being marked using that patients vertebral column as a dividing plane for right and left sides
For lateral projections why are markers commonly placed anteriorly on patient and not posterior?
because markers placed posteriorly are often over exposed
For decubitus projections of the torso why is the marker placed on the “up side” or side away from the cart of table
the marker will be better visualized and less likely to obscure the VOI
When placing more than one image on same IR on a series what is the marker requirement?
Mark only one of the projections placed on the IR as long as they are all projections of the same anatomic structure
When doing bilateral exam on the same IR what is the marker requirement?
mark both projections with the correct R or L marker
How do you decide what size IR to use for a specific exam?
should be just large enough to include the required VOI and to provide a projection with the best spatial resolution
What factors dictate the orientation of the IR for specific exams?
body habitus and part length to IR system
What is the General Rule associated with the size selection and placement of IR?
long axis of the part aligned with long axis of IR
Distinguish between the different body habitus?
Hyperstenic-biggest-wide, short thorax, and broad abdomen with high diaphragm
Asthenic-smallest-long narrow thorax and abdomen with low diaphragm
Hyposthenic- bigger than asthenic but smaller than sthenic (smaller-average patient)
Sthenic- bigger than hyposthenic but smaller than hypersthenic (larger average -muscular)
When is proper collimation achieved?
When the beam of radiation is narrow enough to include only the VOI and approximately .5 inches of the required surrounding anatomy
Good collimation results in what 3 factors
- clearly delineates the VOI
- decreases the radiation dosage by limiting the amount of patient tissue exposed
- Improves the visibility of recorded details by reducing the amount of scatter radiation that reaches the IR
- Reduces histogram analysis errors
What is the general rule associated with collimation?
Each projection should demonstrate a small collimated border around the entire VOI
When does this general rule not apply?
When the ENTIRE IR must be used to prevent clipping of needed anatomy as with chest and abdomen projections
How does collimator light appear on thick patients?
the smaller the collimator’s light field that appears on the patient’s skins surface
Why is collimation so important on thicker patients?
tight collimation demonstrates the largest improvement in the visibility of the recorded details because it will cause the greatest reduction in the production of scatter radiation
For extremities, chest, and abdomen projections how do you adjust your collimator (collimate within)
collimate to within 0.5 inch of the skin line of the chest VOI
magnification is also known as
size distortion
When is magnification present?
on a projection when all axes of a structure demonstrate an equal percentage of increase in size over the real object
How will your collimator borders be determined on structures within the torso?
as close as possible. bring the collimated borders to within 1 inch of the VOI. Use palpable anatomic structures around VOI to determine how close the borders are.
What are the 3 factors that cause some type of size distortion on all images?
- no projection is taken with the part situated directly on the IR
- NO anatomic structure image is flat
- Not all structures are imaged with a perpendicular beam
- all projections demonstrate some degree of magnification
What does the amount of magnification depend on?
on how far each structure is from the IR at a set SID
What 2 situation commonly cause magnification?
- the farther away the part is situated from the IR the more magnified the structure will be
- When the same structure situated at the same object image receptor distance is imaged at a different SID, with the longer SID resulting in the least magnification
How to keep size distortion to a minimum?
use the shortest possible OID and the longest feasible SID
What is the most common shape distortion?
elongation
When does this shape distortion occur?
when one of the structures axes appears disproportionately longer on the projection than the opposite axis
When the least amount of elongation occurs?
when the CR, part, and IR set up is aligned
3 times elongation commonly occurs
- CR is perpendicular to the part and the IR is parallel with the part, but the part is not centered to the CR(off-centered)
- The CR is angled and is not aligned perpendicular to the part, but the IR and the part are parallel with each other
- The CR and part aligned perpendicular to each other, but the IR is not aligned parallel with the part
When is foreshortening demonstrated?
When one of the structures axes appears disproportionately shorter on the projections then the opposite axis
When does foreshortening occur?
When the CR and IR are perpendicular to each other, but the part is inclined/angled. The greater the angle, the greater the foreshortening
What does recorded detail refer to?
to the sharpness of the lines of the image
What constitutes good recorded detail
lines of the image are sharp
What constitutes poor recorded detail?
blurry edges around image lines
What factors influence recorded detail?
focal spot size, SID, OID, speed of image receptor when applicable, contact between the film and intensifying screen when applicable, motion, double exposure
When will images not be visible on regards to focal spot size?
A detail that is smaller than focal spot used to produce the image will not be visible
What does the use of a small focal spot increase?
the visibility of bony trabeculae
When is using a small focal spot not feasible?
when imaging structures that require a high mAs setting
When should you use a large focal spot size?
when a patients thickness measurement is large or a patients ability to hold still is not achievable, a large focal spot is a the better choice
Why is keeping size distortion to a minimum so important?
size distortion produces poor recorded detail
How do you compensate for an increased OID?
by increasing the SID above the standard recommendation
How do you compensate mAs when SID must be increased to offset magnification?
increase the mAs using the exposure maintenance formula
How is poor screen-film contact demonstrated on an image?
by blurred image only in the area where screen and film are not making direct contact
Define motion unsharpness
the lack of detail sharpness on an image that is most often caused by patient movement during the exposure
Describe voluntary motion
can be controlled by the patient; breathing
how to best control voluntary motion
by explaining to the patient the importance of holding still, making the patient as comfortable as possible on the table, using the shortest exposure time, and using positioning devices
how voluntary motion is identified on a n image?
blurred details/// blurred cortical outlines
describe involuntary motion
movement the patient cannot control
how involuntary motion appears on an image?
appears radiographically the same as voluntary motion, with the exception of in the abdomen
How involuntary motion will appear within the abdomen?
peristaltic activity of the stomach and small or large intestine can be identified on a projection by sharp bony cortices and blurry gastric and intestinal gases
How to decrease blur caused by involuntary motion
use the shortest possible exposure time
