Hounsfieldskálán

Hounsfieldskálán, or the Hounsfield Scale, is a quantitative relative scale of radiodensity used primarily in CT scans. It assigns a numerical value to different tissues based on their X-ray attenuation, which is their ability to absorb X-rays. The scale is named after Sir Godfrey Hounsfield, a British electrical engineer who shared the Nobel Prize in Physiology or Medicine in 1979 for his invention of the CT scanner.

Water is defined as having a Hounsfield Unit (HU) value of 0. Bone, being much denser and absorbing more X-rays, has positive HU values, typically ranging from 1000 to 3000 HU for cortical bone. Air, being the least dense, has a value of -1000 HU. Soft tissues like muscle, fat, and organs fall within a range of HU values between air and bone. For example, fat typically has a value around -100 HU, while muscle is around 50 HU, and blood is around 60 HU.

The Hounsfield Scale allows radiologists to differentiate between various tissues and pathologies. For instance, a tumor might appear different from healthy tissue on a CT scan due to variations in density and therefore HU values. This quantitative measurement is crucial for diagnosis, treatment planning, and monitoring disease progression. The scale provides a standardized way to compare imaging findings across different CT scanners and patients.