Filter Component of CT System

The x ray photons emitted from the x ray tube exhibit wide spectrum;many soft (low energy) x rays are present. The low energy x rays mostly absorbed by the patient and contribute little to the detected signal. There fore, it sis necessary to remove these soft x ray to reduce the dose to the patient. To achieve this objective, most CT manufacture employ additional x ray filtration to improve the quality of the beam. The most commonly used filters are the flat filter and the bowtie filter. The flat filter is typically made of copper or aluminum, and is placed between the x ray source and the patient. The flat filter modifies the x ray spectrum uniformly across the entire field of view. Observing the fact the the cross-section of a patient is mostly oval shaped, some manufactures employ a bowie filter to modify the intensity of the x ray beam inside the field of view to further reduce dose to patient. 

To achieve this objective, most CT manufacturers employ additional x ray filtration to improve the quality of the beam. The most commonly used filter is the flat filter and the bowtie filter. The flat filter is typically made of copper or aluminum and is placed between the x ray source and the patient. The flat filter modifies the x ray spectrum uniformly across he entire field of view. Observing the fact that cross section of the patient is mostly oval shaped, some manufactures employ filter to modify the intensity of the x ray beam inside the field of view to further reduce dose the patient.