Retrospective gating
Retrospective gating fundamentally differs from prospective
triggering. No actual triggering is taking place. The physiological
signal and data acquisition times are recorded simultaneously. The
measurement is performed completely independently of the patient’s
heartbeat or pulse. A temporal assignment of images to the
corresponding phase (e.g. heart stimulation) is performed after the
measurement (retrospectively).
In particular, retrospective gating is used to acquire images of the
beating heart. As compared to measurements using prospective
triggering, this technique is especially useful for displaying the late
diastole. Temporal resolution is freely selectable and may be higher
or lower than selected for the measurement.
Retrospective gating can be used for ECG, pulse, or external trigger
signal curves.
Physiological Measurement Unit (PMU)
Description
The Physiological Measurement Unit (PMU) lets you control MR
measurement sequences using a patient's physiological signals (ECG,
respiration and pulse).
There are two versions of the PMU. In case of differences, they are
each identified - but operation is nearly the same for both. Usually
the graphics include PMU version 2 and the MAGNETOM Avanto, but
they also apply to the PMU version 1 and the other MR systems.
The PMU consists of the following components:
◾ PERU (Physiologic ECG and Respiratory Unit): ECG and respiratory
sensor
◾ PPU (Peripheral Pulse Unit): Pulse sensor
◾ External trigger input/output
4.1.2
4.2
4.2.1
4 Physiological imaging
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MR System | Operator Manual
Print No. MR-01501G.621.02.02.02
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