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Bow Tie Filters
•
Decrease patient dose
•
Two types used in different modes: Full fan or half fan mode
•
Full fan mode: image is acquired at the central axis on the
detector panel and images acquired from 200
0
rotation
•
Half fan mode: the detector is offset laterally acquiring only
half of the projection of the patient
Detector panel is offset laterally, rotates a full 360
o
captures only half
a projection and reconstructs the image from that
Recommended for larger FOV (pelvis)
Half fan filters result in the greatest HU discrepancy b/w CT and
CBCT (Ding
et al.,
Yoo and Fang-Fang, Seet
et al.
)