GE FC091194, Руководство по обслуживанию

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GE M
EDICAL
S
YSTEMS
D
IRECTION
FC091194, R
EVISION
02 V
IVID
7 / V
IVID
7 PRO S
ERVICE
M
ANUAL
5 - 6 Section 5-3 - Front End Processor
5-3-5-2 RF and Tissue Processor (RFT)
The RF & Tissue Processor board receives its data from the Beamformer board in the Front End. Both
type of data and what data samples (RF_MODE) to use are communicated to the RFT board from the
Front End Controller board (over the Front End Bus).
RF Processing
Different types of RF processing can be performed depending on later usage of the data; e.g.:
• RF Demodulation
• Digital Time Gain Compensation
• Filtering
• Decimation.
Data Buffer
After RF filtering, the data is written into different sliding ring buffers, dedicated the different types of
data. While data is written into the buffers sample by sample in vectors, multiple samples from the same
range (depth) can be read out.
Both input addressing (start and length) and output addressing (through output events) is controlled by
the Front End Controller board.
Tissue Processing
A number of different tissue processes are performed on this board:
1.) First the signal amplitude is obtained by detection.
2.) Then the data is compressed to attenuate the strong signals and amplify the low level echoes.
3.) After compression, Zone Stitching is performed. This is used to combine the (transmit) focal zones
from different vectors into one vector by weighting the zone transitions, and does only apply to
phased/linear array probes where multiple vectors can be collected in the same direction. For M-
Mode, peak detection and edge enhancement is implemented.
4.) Finally an offset can be added to the signal and clipping is performed.
5.) The tissue data is then tagged, and sent on to the Image Port board.
Color Flow Processing
No Color Flow processing is performed here, except for the RF demodulation previously mentioned.
The data used for Color Flow is tagged with the appropriate headers and tails and routed through an
output multiplexer to the Backend Processor (BEP).
Doppler Processing
In addition to RF demodulation, a variable digital high pass filter is implemented on the RFT board.The
purpose of this filter is to remove strong low frequency signals returning from wall motion, valves and
leaflets. The filtering is performed by the local DSP. Data is then tagged and sent to the Spectrum
Doppler Processor board.