SCANNING PARAMETERSMay factors affe

SCANNING PARAMETERS
May factors affect the quality of the image produced. Some of the these variables can be regulated by the operator, whereas others, such as patient size, cannot.
Amoung the factors that the operator can control are miliampere (mA) level, scan time, slice thickness, field of view, and scan algorithm. On some system, the operator may adjust the kilovolt-peak (kVp) setting, although on may systems, it is fixed at 120 kV. As a group, thesefactors are usually referred to as scanning parameters.
As in standard radiography, the total x-ray beam exposure in CT is dependent on a compbination of miliampere setting, scan time, and kilovolt-peak setting. Miliampere level and scan time together define the quantity of x-ray energy, whereas kilovolt-peak setting defines the quality, or average energy, of the beam. These factors are analogous to water flowing through a hose. The intensity, or force, with which the water flows through the hose resembles kilovolt-peak leve. The quantity of water that flows is similar to scan time. The product of miliampere setting and scan time is known as milliampere-seconds (mAs) and is the quantitative measure of the x-ray beam.