6–2–1 Visual Channel Alive
Description. Visual Channel Alive provides a visual indication of beamformer channel or probe element integrity.
This tool tests all parts of the beamforming chain in a general way using the Gray 2D image path. The probe, if one is used, is also tested. The system fires one vector for each loopback channel or probe element.
The test configures TD memory for all 128 channels such that for the first 128 firings of a scan, all channels except one are receive (or transmit) apodized (i.e. only one channel contributes to the beam sum). For firing 0, only channel 0 is active, for firing 1 only channel 1 is active, etc. The beamforming coefficients for the center beam are copied to all of the other beams, and then the apodizations are applied. This scheme should produce a uniform image which will make beams corresponding to defective channels easier to identify.
Signal sources can be noise (high system gain), external signal injected into loopback, or TD pulsers. The two Visual Channel Alive Transmit tests use TD pulsers for the signal source.
The test first runs a check on the TD channels. Then if a transmit test was selected, all channels are set to receive, and for each beam a different channel is set to transmit.
There is no PASS/FAIL status produced by this test; you must visually deduce channel operation. If a channel is bad, the image along the vector (direction) for which that channel is supposed to be active will be “different” from those corresponding to “good” channels. When the test is exited, the system reboots automatically.
Minimum System. Entire Front End, all cables, MC, SS, BMP, ALM, XY, VP, monitor, PIA, OPI/CPU, LOOPBACK or probe, if probe: water tank or phantom
Tools. Loopback is sufficient for testing Receive W/Transmit. Otherwise, a probe must be used.
Front End Back End
Probeor OPI/CPUop panel
RECEIVE W/O XMIT
RECEIVE WITH XMIT TRANSMIT
QUIT ALIVE CHANNEL CHANNEL QIQ
ALIVE MENU VISUAL
TEST PATH FOR VISUAL CHANNEL ALIVE ILLUSTRATION 6–1
6–2–1 Visual Channel Alive (Continued)
Depending on the test, one channel/element is forced to be active on transmit or receive. Vector 1 may be transmitted or received by channel 1, vector 2 is transmitted or received by channel 2. The other channels are turned off. For 192 element probes, the active channel wraps if there are more vectors than elements available. For 128 element probes, 128 vectors are used.
TABLE 6–1
TESTS IN VISUAL CHANNEL ALIVE
Test What it does
TRANSMIT Transmit
One/Receive All
Transmits on one channel (element) per vector and receives on all channels.
RECEIVE W/O XMIT Receive w/o Transmit
Receives on one channel (element) per vector (no XMIT).
RECEIVE WITH XMIT
Transmit All/Receive One
Transmits on all channels and Receives on one channel (element) per vector.
Procedure. Perform the Visual Channel Alive Tests as follows:
1 . Attach probe (or loopback if desired for Receive with Transmit test only) to XDIF slot to be tested.
2 . Adjust controls for consistency and maximum brightness: Select the linear Gray Map [Code M] which is ‘E.’
Adjust Acoustic Output and Gain to maximum value. Push the TGC knobs all the way to the right. Adjust depth to 10 cm.
3 . With software in Application mode, not Service, hold [Option ∆] and type [1]. The Option key is on the right side of the space bar.
4 . Toggle the softkey switch that selects “Visual Channel Alive.” Click on the desired test. Patient ID will change to reflect the name and status of the diagnostic being run. Wait while the system sets up this test
5 . The 128 element loopback or sector probe will image 128 vectors rather than the normal amount. If you see a black line in the image, run the Transmit 1 and Analog Receive diagnostics. The 192 element linear probe will image 192 vectors which may show bad commutation. Run the Probe Control diagnostic to test the system control. If the system works, the problem must be with the probe.
6 . To exit, click Quit Channel Alive. Press [Exit
]
to return to application mode. The system will reboot to clear diagnostic values.Transmit: Receive with Transmit:
Pre–R7 R7 and
Later
SECTOR IMAGES FOR 128 ELEMENTS ILLUSTRATION 6–2
6–2–2 Quantitative Image Quality (QIQ) Tests
Description. QIQ Tests offer an objective way to determine if image quality is changing. Included in this category of service software tools are the Beam Profile Test and the ROI Intensity Tool.
Note
The B Mode ROI Tool can be used to monitor Image Quality. Beam Profile works but requires special test equipment and is done at the factory.
Beam Profile is a measure of a system’s skill at forming an acoustic lens. This software test measures Detail Resolution and Acoustic Peak Signal to Noise ratio. A special Wire in Water phantom is required for the test. The system controls the beamforming settings and repeats measurements every Gain setting from 0 to 100 in multiples of ten. This test is done at the factory as a Final Test.
D Detail Resolution: system’s ability to distinguish closely spaced reflectors.
Expected Result: 1.6 degrees or less
D Peak to Noise: system’s ability to detect/create an echo that is louder/greater than the noise the system detects/creates.
Expected Result: 72 dB or more
The Region of Interest (ROI) software tool enables measurement of Image Uniformity (grayscale) and Contrast Resolution on any or all probes. Up to eight ROI’s can be recorded on the image.
D Image Uniformity: place the ROI templates inside then above the four “cysts.” Refer to illustration 6–3 also.
Expected value: A Standard deviation less than 20 indicates a good ROI.
D Contrast Resolution: place the central ROI template on the largest “vessel” and repeat on both sides of the hole. Measure at 8 cm and 14 cm depths.
Expected value: Contrast should be greater than 30 dB.
Note
Establish and keep a baseline against which to compare future performance. Create a new baseline when the imaging software changes greatly as it does between R5.6 and R6. This baseline should be taken when the machine is known to be operating well. Normally, the best time would be shortly after Installation or Planned Maintenance. It is also crucial to use the same tools and settings every time the test is performed. Record the serial number of the probe and phantom used for the test. The software will control the important settings.
6–2–2 Quantitative Image Quality (QIQ) Tests (Continued) Tools. RMI 403GS phantom, probe, ring stand to hold probe
“CYSTS” 1 cm for image uniformity (ROI) and grayscale 4
6
8
10
12
16 14
1 2 3 4
RMI 403GS
depth in cm Zoom in and
measure
distance between a pair of vertical pins which are 20 mm apart: VERTICAL
“Vessels”
for contrast resolution
wire for beam profile
(ROI)
Axial resolution 0.1 mm nylon pins
are 30 mm apart at 2 cm and 12 cm depths: HORIZON-TAL
Dead Zone
2
RMI 403GS PHANTOM ILLUSTRATION 6–3
Suggested Parameters. Consistency is very important; you may use other settings, just make sure you record and use the same ones next time you repeat a test.
D Linear Gray Map [Code+M] (Select ‘E’ if R6) D Acoustic Output at 83%
D TGC pots all the way to the right
Probe Gain
Depth Focus
6–2–2 Quantitative Image Quality (QIQ) Tests (Continued) Procedure. Perform the QIQ Tests as follows:
1 . With software in Application mode, hold [Option ∆] and type [1]. The Option key is on the right side of the space bar. This key combination will display Image Quality Tools on the VFD (softkey display).
VISUAL QIQ CHANNEL
ALIVE MENU
2 . Toggle the softkey under QIQ MENU to change the softkey display to the QIQ test options.
QUIT CF
MODE