Siemens EMOTION 16-Jun - Manual (Page 484)

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Respiratory Gating
When imaging of the chest or abdomen is performed
by CT, there may be artifacts produced causing prob-
lems with reproducibility and resolution of images due
to patient respiration. Organs will move with every res-
piratory motion.
Especially in the radiation therapy planning using a lin-
ear accelerator for tumor treatment, normal tissues
around a focus might be unnecessarily exposed to radi-
ation if the target is located in a movable organ,
because the field of irradiation has to be set wider than
the actual size of the tumour due to the organ's motion
during respiration.
As far as the respiratory motion is periodical and repet-
itive, the organs in the chest or abdomen move period-
ically and repetitively according to respiratory motion.
Therefore the diagnostic artifacts and image degrada-
tion, and the treatment dangers can be avoided if pre-
cise detection of respiratory motion and its conse-
quent, synchronized imaging or irradiation is available.