Slice of tissue X-rays is:
A i.e. Tomography Hounsfield units (CT number) represent average linear attenuation coefficientQ. The Hounsfield scale is an arbitray one with air at-1000 and water at 0 units as fixed pointsQ. Fat which is less dense than water also has a negative value (- 20 to - 100 range). CT has been designated a high dose procedure as it exposes 50-500 times higher radiation doses than a conventional radiograph. Lead shielding or coating (1/16 inch) is most common way of protectionQ. Other protective agents include concrete (4-6 inch standard density i.e. 147 pounds/cubic foot), brick blocks and barium plaster. Narrow beam collimation, high spatial reconstruction algorhythm like bone algorhythm and small field of view improve spatial resolution of HRCTQ.
Tomography
Mammography
Contrast studies
All of the above