Cardiac Gating/Triggering

Cardiac Gating/Triggering is used for:

• imaging the heart’s structure and function
• imaging in the thorax
• Cine-PC arteriography to examine flow

There are two types of gating/triggering:

• ECG: uses the heart’s electrical activity as reported by the ECG. Electrode placement is critical to a successful ECG scan. Adjust the electrodes until a strong signal is received. If the signal is lost during the acquisition, it will abort the scan.
  • For details, see ECG gated exam procedure.
• Peripheral: uses a photopulse sensor that picks up the mechanical action of blood pulsing through the body.
  • For details, see Peripheral gated exam procedure.

Cardiac Triggering is best suited for acquiring T2-weighted images. Cardiac Gating is best suited for uniform, short TR scans.

Peripheral Gating is used for head, cervical, and thoracic spines to minimize pulsatile motion of CSF on T2*- or T2-weighted scans. It is safe for patients due to the fiber-optic technology.

Gating

Cardiac Gating acquires data continuously at the operator-selected TR. Data acquired between user-defined Trigger Windows and after a user-defined delay may be used for image creation.

Table 1. Image legend

Number
1	Trigger Window
2	Uniform TR

Triggering

Cardiac Triggering is a process by which data acquisition is initiated when a trigger of some type is detected.

Table 2. Image legend

Number
1	Trigger Window
2	Trigger Delay
3	RR Interval
4	Slices