Which of the following is true about the CT number for body tissues?

The statement that CT numbers vary significantly across different tissues is accurate because CT numbers (also known as Hounsfield Units) reflect the density and composition of various tissues. Each type of tissue has a specific atomic composition and density, which influences how X-rays are attenuated as they pass through. For instance, air has a CT number of approximately -1000 Hounsfield Units, fat around -100, water at 0, and various types of tissues such as muscle and bone correspond to positive CT numbers, with bone being significantly higher due to its high density.

This variability in CT numbers is critical for distinguishing between different types of tissues in diagnostic imaging, allowing radiologists to identify pathological conditions or anatomical structures based on their density differences. The range of CT numbers helps to create clear images that differentiate between structures, aiding in diagnosis and treatment planning.

Other statements in the context do not reflect the variability that exists in CT imaging; for example, the notion that CT numbers are consistent across all body tissues is inaccurate given that different tissues inherently possess distinct physical properties. Similarly, while CT numbers can be both positive and negative, they are not limited to just fat and water. Thus, the correct understanding is that CT numbers vary significantly between different tissues, allowing