Esaote MyLab, Руководство оператора

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M y L a b – S A F E T Y A N D S T A N D A R D
2-9
Note
The TI index display depends on the application and on the mode.
The MI may increase whenever the PRF is decreased, i.e. when the field of view is
increased.
MyLab
allows the user to set the transmit focal point which will affect both indices
by varying the beam profile. Generally, higher MI's and TI's will occur with closer
focal points. If more than one transmit focal point is activated, MI and TI values
will each correspond to the zone with the largest value. In addition, all system
probes can image at two frequencies; both indices are usually different, depending
on the probe bandwidth.
The same controls described for 2D affect the acoustic output. Because the tissue
response is a non-linear phenomenon, this modality usually requires higher
acoustic outputs
than conventional imaging. While using this mode, the
MI
is
your primary concern; a deeper transmit focal point helps to keep the MI value as
low as possible.
In M-Mode, the transmitted field is only affected by the transmit focal point and
the frequency. If M-Mode is displayed with 2D and the 2D is updated, the system
may show the latter mode MI (and TI if available) if higher.
The MI is primarily dependent on 2D settings, i.e. the depth (which will determine
the 2D and color PRF) and the transmit focal point. The MI may also be increased
by a decrease in the color PRF.
The TI may be increased by increasing the color CFM. Increasing the color frame
rate may increase the TI while decreasing the MI. Finally, probes can provide color
at two frequencies; the outcome in terms of transmitted field is marginal and
largely unpredictable.
This mode optimizes CFM settings in order to image the movement of tissue, thus
the same controls described for 2D-CFM affect the acoustic outputs.
In PW, the sample volume depth automatically sets the Doppler PRF and the focal
point. Deeper sample volumes will cause lower PRF; the MI may, however, not
increase since the focal point is far, while the TI is generally reduced. The TI may,
however, change if the sample volume size is varied. This factor accounts generally
for a MI modification.
TV Doppler optimizes your settings to analyse tissue motion.
Finally, most probes provide Doppler at two frequencies; the outcome in terms of
transmitted field is marginal and largely unpredictable.
2D
TEI
M-Mode
2D-CFM
TVM
Pulsed Wave
Doppler
TV