Which of the following statements regarding prepatient collimation is true?1. An increase in prepatient collimation increases Pt dose.2. Prepatient collimation is used to focus radiation through the section of interest.3. Prepatient collimation directly controls slice thickness. A. 2 only B. 3 only C. 1 and 2 only D. 2 and 3 only
3 only Prepatient collimation controls the slice thickness by reducing the size of the primary beam. This is accomplished with the use of the lead shutters, which absorb the outer margins of the primary beam. Increases in prepatient collimation reduce patient dose by reducing the number of x-ray photons reaching the patient.