This document provides an evaluation of a portable knee x-ray image. It identifies several issues with the image including a lack of beam restriction, improper centering and angulation of the cassette resulting in overlapping anatomy. The evaluator recommends repeating the image with a marker identifying the technologist, at least three sides of collimation, and angling the cassette 5 degrees cephalically to ensure the tibial plateau is perpendicular. Repeating the image would properly position and separate the visualized anatomy.
2. HIPAA Compliance
• This image is HIPAA compliant
• There is no information provided
on this image that could identify a
patient or an imaging facility
• It does not violate patient
confidentiality
4. Marker and Patient ID
• The correct right anatomical marker
should be placed on the lateral side of
the patient’s body, indicating it is a right
knee, so it is displayed on the viewer’s
left side
• Marker should include the technologist’s
identification
• It should not superimpose any pertinent
anatomy
• A portable marker should have been
used along with the time in some
hospital protocols
• The image is now displayed correctly
based on my marker placement
JW
Portable
time
5. Radiation Hygiene
• An image must have a minimum of three
sides of beam restriction and (1) of these
sides should be closest to the patient’s
gonads
• This is especially true while doing
portables (Technologist’s should also
wear a minimum of 0.25 mm/Pb eq)
• Gonadal shielding is required if the gonads
are within 5 cm of the primary beam
• This image does not display appropriate
beam restriction and is only clearly visible on
two sides of the border
• There is no evidence of primary or additional
shielding
JW
Portable
time
6. Completeness of
Position/Projection
• Routine imaging of the knee includes:
• AP projection, posterior position
• 45° AP (medial/internal) oblique
• 45° AP (lateral/external) oblique
• Mediolateral projection
• Additional images depending on hospital/facility
protocol:
• PA/AP axial intercondylar fossa projection
• Tangential patella projection
• This image is a routine projection and all
anatomical parts are visualized on the
image, but not correctly positioned
time
7. Artifact
Identification
• There appears to be no preventable physical
artifacts present on the image
• There appears to be no body parts
superimposed over the image
• There appears to be no hospital
paraphernalia present
• There appears to be no patient clothing
visible
• There appears to be no indwelling
artifacts/foreign bodies visible on this image
time
8. Artifact Identification
• There appears to be no
excessive fog affecting
the quality of the image
• There appears to be no
CR/DR artifact on the
image
time
9. Image Sharpness
• There appears to be no
gross voluntary motion
visible on the image
• There appears to be no
excessive quantum mottle
present in the image
time
10. Image Sharpness
• There appears to be no
evidence of a double or
previous exposure
• Grid lines, grid artifact, &/or
grid cut-off are not visible on
the image because a grid
might not have been used
&/or a high frequency could
have been used since it was
done portably
time
11. Image Sharpness
• Size distortion does not appear to be greater than
expected for this image because OID is minimal in this
position
• The CR is not properly centered to femorotibial joint
space, but less than 1 cm
• There is evidence of slight shape distortion due to the
CR/part misalignment
• Due to the insufficient 5 degree cephalic angle that
should have been used because the patient’s thigh
thickness appears to be >25 cm the tibial plateau
does not appear to be perpendicular to IR
• The patellar apex sits closer to the upper joint space
also indicating the CR was not proper angled
time
12. Accurate Part Position
• The part does appear to be
aligned parallel to the image
media
• The part is slightly off-centered
to the image media
time
13. Accurate Part Position
• The CR is off centered slightly laterally to the
femorotibial joint space, but within 1 cm of the
anatomical part
• The CR is adequately aligned to the image
media
• The CR’s alignment does not appear to
conform to an acceptable IR exposure
recognition field due to the lack of only two
sides of collimation
time
14. Accurate Part Position
According to Kathy McQuillen Martensen’s Radiographic Image Analysis and Merrill’s Atlas:
• 40” SID and 10 x 12” IR
• Position the patient supine, with the knee joint centered to the IR
• Internally rotate the leg until the femoral epicondyles are at a 45 degree angle with the IR
• Angle the CR to align it parallel with the tibial plateau
• To do so measure the patient from the ASIS to the table after the patient has been
accurately positioned to determine the correct CR angulation (use a caliper and do not
include abdominal tissue in measurement)
• 5 degree caudal if ASIS to tabletop measurement is 18 cm below
• Perpendicular if ASIS to tabletop is between 19-24 cm
• 5 degrees cephalic angle if ASIS to tabletop is 25 cm or greater
** It is not uncommon to require a cephalic angle for the AP medial oblique when a
perpendicular or caudal angle was used for an AP projection because the patients hips
are elevated
• Center the CR to the midline of the knee 1 inch distal to the medial epicondyle (Martensen)
• Center the CR to the knee joint at ½ inch distal to the patellar apex (Merrill’s)
• Longitudinally collimate to include ¼ of the distal femus and proximal lower leg
• Transversely collimate to 0.5 inch of the knee skin line
• Table bucky and a grid should be used if the knee is greater than 10 cm part thickness,
however when done portable a stationary grid would be used
15. Accurate Part Position
According to Kathy McQuillen Martensen’s Radiographic Image
Analysis and Merrill’s Atlas:
Evaluation Criteria:
• Fibular head is seen free of tibial superimposition (Martensen)
• Lateral femoral condyle is in profile without superimposing the medial
condyle
• Knee joint space is open: when correct obliquity is used (Bontrager)
• The anterior and posterior condylar margins of the tibia are aligned
• Fibular head is approximately 0.5 in distal to the tibial plateau
• Knee joint is at the center of the exposure field
• Tibia and fibula should be separated at their proximal articulations
• Posterior tibia should be visible
• ¼ of the distal femur and proximal lower leg included
• Margin of the patella projecting slightly beyond the medial side of the
femoral condylar leg and the surrounding knee soft tissue are
included with the exposure field
16. Accurate Part Position
Evaluation• A minimum of three sides of beam restriction should be
demonstrated
• The CR is centered slightly laterally to the femorotibial joint
• The CR appears to have been directed perpendicular
causing the tibial plateau to not appear perpendicular to the
IR, therefore a 5 degree cephalic angle should have been
used due to the patient’s thigh thickness >25cm
• The anterior and posterior condyles of the tibia are not
superimposed due to incorrect CR angulation
• The patellar apex sits closer to the upper joint space also
indicating the CR was not proper angled
• The knee does not appear to be sufficiently rotated to 45
degrees because the tibia is superimposed over the fibula
head and also demonstrating a partially closed tibiofibular
articulation
time
17. Accurate Part Position
Evaluation
• All pertinent anatomy is included on
the image
• The anatomical part is not positioned
correctly based on my assessment of
the evaluation criteria
time
18. Accurate Part Position
Evaluation
• The most radiolucent structure is
the surrounding soft tissue and
knee joint (which should be open)
and it is visible on the image
• The most radiopaque structure is
the bony cortex and it is visible
on the image time
19. Judicious Exposure Technique
• Assessment of Image Contrast
(Window Width)
• Contrast is determined by the
number of grays produced on an
image
• Extremities should be displayed
with short scale contrast,
showing many shades of gray
• The image appears to have
adequate contrast
time
20. Judicious Exposure Technique
• Assessment of Image’s
Brightness (Window Level)
• The image’s brightness is the
balance between light and dark
areas on the image and it
appears to be acceptable
because you are able to visualize
the soft tissue, bony trabeculi and
cortex
• I would expect the overall EI
value to be within normal range
time
21. Accept/Reject?
This image should be repeated because it does not meet
minimal established standards
Required corrections:
• Use a correctly placed right marker with technologist
identification and a portable marker along with the time
the exposure was taken
• Include a minimum of three sides of collimation
• Center the CR to the femoroibial joint space
• Rotate the knee internally to 45 degrees so the tibia
does not superimpose over the fibula head articulation
• Angle to CR approximately 5 degrees cephalically to
ensure the tibial plateau is perpendicular to the IR
• Aligning the anterior and posterior condyles of the tibia to
superimpose one another
• Angulation will also rotate the patellar apex superiorly and
medially away from the joint space
time
22. Sources
Frank, E, Long, B, & Smith, B. Merrill’s atlas of radiographic
positioning and procedures. 12th ed. St. Louis, MO:
Mosby, 2012.
McQuillen-Martensen, K. (2015). Radiographic image analysis.
Vol 4. St. Louis, MO: Elsevier
Saint Mary’s Medical Center
