In order to halve density on an image, what factor must be ...

[kodithompson]

In order to halve density on an image, what factor must be adjusted?
 
 kVp by 5
  kVp by 15
  kVp by any factor
  kVp by 30

Question 2

Where is the sustentaculum tali located?
 
 lateral aspect of the calcaneus
  posterior calcaneus
  anterior calcaneus
  medial aspect of the calcaneus

[brittiany.barnes]

Answer to Question 1

kVp by 15

Rationale: In order to double density on an image, the kVp must be increased 15; to halve the density, decrease kVp by 15. This is the 15 rule.

Answer to Question 2

medial aspect of the calcaneus

Rationale: The sustentaculum of the calcaneus is located on the medial aspect of the calcaneus on the toe end of the calcaneus. The sustentaculum tali will be easily visible on the plantodorsal axial projection of the calcaneus.