Nasium/horizontal Flashcards
Why is the projection name “horizontal”?
b/c the central ray is directly parallel to the horizontal plane of the axis
What is the primary analytical purpose for the Nasium?
Atlas laterality (R/L - 3rd letter of listing)
What is the secondary purpose of the Nasium film?
To determine if there is any condyle malformation
How is the bucky position in the Nasium film?
Tilted to touch back of head and shoulders
The ray will pass through the _______ at a distance of ____?
Inferior tip of the mastoid
40”
The film is taken A-P. How is it analyzed?
P-A
What are the line of the Nasium film?
- OOL - ocular orbit line
- SBL - superior basic line
- IBL - inferior basic line
- VML - vertical median line
Which two lines of the Nasium film are always parallel?
OOL and SBL
How do you draw the OOL?
Find as many like points in the orbit. Find two parallel and draw a line through one of those sets.
Where do you place the dots for the SBL? How do you draw this line?
Medial inferior tips of the occipital condyle
Place parallel on OOL and scroll down to 1st condyle tip to draw line
What does it mean if the SBL doesn’t go through both condyle tips?
Condyle malformation/assymetry
The IBL is constructed by drawing a line through two dots placed where?
Lateral-inferior tips of atlas lateral masses
Between what two dots do we draw the “+” sign?
Condyle tips
What does the plus sign represent in this film?
center of the neural canal.
How do you draw the VML?
Place parallel perpendicular to the OOL and draw line through center of the + sign to the IBL.
How is atlas laterality determined on this film?
Measure the distance form the later inferior tips of the lateral masses to the VML.
Which side is the side that shows laterality?
The side with the greatest distance.
What is the 70% rule for the Nasium?
The SBL and IBL converge on the side of laterality 70% of the time.
Why does the 70% rule occur?
Due to the fact that when the atlas misaligns laterally, it will move up the occipital condyle (unless there is anomalies)
What is something to consider if the OOL is not parallel to the top of the film?
Could indicate lateral head tilt.
How can you check if there is rotation of the head?
Check mastoid on both sides to see if symmetrical.
Also, look at the rami of the mandible If symmetrical
How can you find the TVPs?
Find mastoid and go directly medially
If tips of lateral masses are obstructed and you can’t approximate them, what else can you do?
Use where the lateral masses and the TVP meet on either side.
What can you mistake for the occipital condyle?
Nasal aperature
How do you visually check for laterality?
Check if displacement btw superior lateral portions of lateral mass with lateral occipital condyle is same on both sides. If condyle extends on a given side that is side of laterality.
