Cine sequences used in cardiovascular
MRI are collection of images (usually at the same spatial location) covering of one full period of
cardiac cycle or over several periods in order
to obtain complete coverage.
The
pulse sequence used, is either a standard
gradient echo pulse sequence, a segmented data acquisition, a
gradient echo EPI sequence or a
gradient echo with
balanced gradient waveform.
In
cardiac gating studies it is possible
to assign consecutive lines either
to different images, yielding a multiphase sequence with as many images as lines, or the lines are grouped
together in
to segments and assigned
to the same image. The overall time
to acquire such a segment has
to be small compared
to the RR-interval of the
cardiac cycle, i. e. 50 ms, and hence contains typically 8
to 16 image lines.
This strategy is called segmented data acquisition, and has the advantage of reducing overall imaging time for
cardiac images so that they can be acquired within a breath hold, but obviously decreasing the
temporal resolution of each individual image.
This method s
hows dynamic processes, such as the ejection of blood out of the heart in
to the aorta, by means of fast imaging and displaying the resulting images in a sequential-loop, the impression of a real-time movie is generated. Ejection fractions and stroke volumes
calculated from these
cine MRI images in different
cardiac axes have been s
hown
to be more accurate than any other imaging modality.
See also
Cardiac Gating.