ABSTRACT

This chapter defines tube current and discusses its effect on patient exposure. The radiation exposure rate at the input phosphor is independent of x-ray beam size. Therefore, the image will not be brighter with a larger beam size. However, the total volume of the patient that is exposed to radiation will increase, as well as the amount of scattered radiation to the operator. The chapter describes how kilovoltage peak (kVp) affects patient exposure. High kVp technique used for fluoroscopic examinations tends to reduce patient exposure because the improved x-ray beam quality allows the use of a much lower tube current. Differential absorption in the patient increases as the kVp is lowered, since there is less penetration of the body part. The chapter identifies the type of low-absorption table-top material. Carbon fiber table tops will significantly reduce patient exposures.