What is the density order of tissues from low to high?

The correct order of tissue densities from low to high is gas, fat, water, and bone. This hierarchy is based on the properties of these materials and how they interact with radiographic imaging techniques.

Gas has the lowest density, which is why it appears dark on radiographs. It provides the least resistance to X-ray penetration. Following gas, fat has a higher density than gas but is still relatively low compared to water and bone, making it appear slightly darker than water on X-ray images.

Water, which includes soft tissues and organs, has a density that is higher than fat. On radiographs, water and soft tissues have a moderate appearance since they absorb more X-rays than fat but less than bone. Lastly, bone has the highest density of the four materials. Its high calcium content allows it to absorb a significant amount of X-rays, leading to a lighter appearance on radiographs.

Understanding the relative densities of these tissues is crucial for interpreting radiographic images accurately and is a fundamental concept in radiology.