Clinical Radiology Made Ridiculously Simple, Edition 2

Radiology 101 "Key Concepts"

The five radiographic densities are in order of increasing brightness as shown by a simple test:

1. Air

2. Fat

3. Fluid

4. Bone

5. Metal

Chest Radiology

Snow ball sign. The Snow ball sign is used to determine whether a peripheral mass arises from the lung or from a surrounding structure.

It is analogous to a snow ball thrown on a wall (Fig. 2-6AD above). If the nodule or mass looks like a snow ball just before impact, it is localized in the lung (Fig. 2-6AB). However, if it looks like a flattened snow ball just after impact, it arises from a surrounding structure (chest wall, pleura or mediastinum; Fig. 2-6CD).

Cervical Spine

Hangman's fracture. This fracture is secondary to an extension injury, which commonly occurs in motor vehicle accidents (MVA) or in hangings (hence the name).

It is a bilateral C2 pedicle fracture, with anterior displacement of the anterior part of C2.