Nasium/horizontal

Question 1

Why is the projection name “horizontal”?

Answer 1

b/c the central ray is directly parallel to the horizontal plane of the axis

Question 2

What is the primary analytical purpose for the Nasium?

Answer 2

Atlas laterality (R/L - 3rd letter of listing)

Question 3

What is the secondary purpose of the Nasium film?

Answer 3

To determine if there is any condyle malformation

Question 4

How is the bucky position in the Nasium film?

Answer 4

Tilted to touch back of head and shoulders

Question 5

The ray will pass through the _______ at a distance of ____?

Answer 5

Inferior tip of the mastoid

40”

Question 6

The film is taken A-P. How is it analyzed?

Answer 6

P-A

Question 7

What are the line of the Nasium film?

Answer 7

1. OOL - ocular orbit line
2. SBL - superior basic line
3. IBL - inferior basic line
4. VML - vertical median line

Question 8

Which two lines of the Nasium film are always parallel?

Answer 8

OOL and SBL

Question 9

How do you draw the OOL?

Answer 9

Find as many like points in the orbit. Find two parallel and draw a line through one of those sets.

Question 10

Where do you place the dots for the SBL? How do you draw this line?

Answer 10

Medial inferior tips of the occipital condyle

Place parallel on OOL and scroll down to 1st condyle tip to draw line

Question 11

What does it mean if the SBL doesn’t go through both condyle tips?

Answer 11

Condyle malformation/assymetry

Question 12

The IBL is constructed by drawing a line through two dots placed where?

Answer 12

Lateral-inferior tips of atlas lateral masses

Question 13

Between what two dots do we draw the “+” sign?

Answer 13

Condyle tips

Question 14

What does the plus sign represent in this film?

Answer 14

center of the neural canal.

Question 15

How do you draw the VML?

Answer 15

Place parallel perpendicular to the OOL and draw line through center of the + sign to the IBL.

Question 16

How is atlas laterality determined on this film?

Answer 16

Measure the distance form the later inferior tips of the lateral masses to the VML.

Question 17

Which side is the side that shows laterality?

Answer 17

The side with the greatest distance.

Question 18

What is the 70% rule for the Nasium?

Answer 18

The SBL and IBL converge on the side of laterality 70% of the time.

Question 19

Why does the 70% rule occur?

Answer 19

Due to the fact that when the atlas misaligns laterally, it will move up the occipital condyle (unless there is anomalies)

Question 20

What is something to consider if the OOL is not parallel to the top of the film?

Answer 20

Could indicate lateral head tilt.

Question 21

How can you check if there is rotation of the head?

Answer 21

Check mastoid on both sides to see if symmetrical.

Also, look at the rami of the mandible If symmetrical

Question 22

How can you find the TVPs?

Answer 22

Find mastoid and go directly medially

Question 23

If tips of lateral masses are obstructed and you can’t approximate them, what else can you do?

Answer 23

Use where the lateral masses and the TVP meet on either side.

Question 24

What can you mistake for the occipital condyle?

Answer 24

Nasal aperature

Question 25

How do you visually check for laterality?

Answer 25

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.