CAMRT Radiography Practice Exam

What is the significance of Hounsfield Units in CT imaging?

1. They measure the thickness of the body part.

2. They quantify the energy levels used in imaging.

3. They indicate the density of the tissue imaged.

4. They provide information about the patient's heart rate.

The correct answer is: They indicate the density of the tissue imaged.

Hounsfield Units (HU) serve a critical role in CT imaging by indicating the density of the tissue being imaged. The scale was developed to provide a standardized measurement whereby various tissues can be characterized based on their radiographic attenuation properties. Water is assigned a value of zero Hounsfield Units, while air is given a value of -1000 HU, and densely calcified structures, such as bone, can reach values of +1000 HU or even higher. This standardized measurement allows radiologists and healthcare professionals to assess and differentiate between various types of tissues on a CT scan effectively. For example, differences in Hounsfield Units can help identify cysts, tumors, and fluid collections, contributing to accurate diagnosis and treatment planning. Other options relating to measurements of thickness, energy levels, or heart rate are not relevant in the context of Hounsfield Units. The focus of Hounsfield Units is specifically on density, which is pivotal in evaluating and understanding the composition of tissues within the body through CT imaging.