Head & Neck Infections

Question 1

What is the difference in contrast detection between CT and conventional radiography?

Answer 1

CT detects differences in contrast of less than .5%

Conventional radiography detects differences in contrast of approximately 5%.

Question 2

What unit is the CT number expressed in?

Answer 2

Hounsfield units (HU).

Calibrated from -1000 HU for gas to +1000 for high attenuation metal

Question 3

Appearance of abscess on CT.

Answer 3

Peripheral enhancement and central coalescent areas of lower density. Higher attenuation in the periphery.

Question 4

Radiopharmaceutical in PET

Answer 4

18F-FDG

Glucose analog. Exploit difference in glycolytic rate. Can also show inflammatory cells during infection due to hypergloycolytic state.

Question 5

Malignant otitis externa bug

Answer 5

Pseudomonas auruginosa

Gram negative bacillus

Question 6

T1 images are good for?

Answer 6

Sensitive for an atomic details. Measures rate at which tissue becomes magnetized.

Question 7

T2 images good for?

Answer 7

Detecting disease processes rather than fine an atomic detail.

Shows fluid accumulations and effusions better

Measures rate at which spin becomes disorganized due to inhomogeneities in field.

Question 8

Who studied fasciae spaces of the head and neck in the 1930’s?

Answer 8

Grodinsky and Holyoke