CAMRT Radiography Practice Exam

What is the typical CT number for cerebrospinal fluid (CSF)?

1. 10

2. 15

3. 30

4. 50

The correct answer is: 15

The typical CT number for cerebrospinal fluid (CSF) is approximately 15 Hounsfield units. This value indicates the radiodensity of CSF as it appears on a computed tomography scan. The Hounsfield scale is used in CT imaging to express radiographic attenuation values, with air defined as -1000 HU, water as 0 HU, and normal brain tissue typically within the range of 30 to 50 HU. CSF is less dense than the surrounding brain tissue, which is why its CT number is lower on the scale. Understanding this value helps radiographers and radiologists interpret scans accurately, enabling the identification of abnormalities or conditions affecting the brain and surrounding structures. In clinical practice, recognizing the characteristic CT number of CSF assists in distinguishing it from other fluids or tissues within the cranial cavity, thereby ensuring proper diagnosis.