HD 8Ch Foot Ankle Coil Troubleshooting Tips

You are unable to pre-scan or are scanning and yet receiving no signal.

• Verify that you have selected the appropriate system coil selection. Refer to the Operators Manual for additional information.

• Verify the green light above Port A is illuminated. This indicates the coil is properly plugged into the system.

• Verify that the landmark is correct and that the cradle has not unlatched.

• Verify that the scan locations and any FOV offsets are correct.

• Perform a continuity check on the external cable (below). The continuity check must be performed by a GE authorized Service Engineer.

• Verify that the coil is positioned with the cable exiting towards the bore and that the system and coil polarity match.

• If you still cannot get a signal, try to scan (transmit and receive) with the body coil. For this test, be sure to remove the imaging coil from the magnet bore before you scan with the body coil. If you still receive no signal, the problem probably lies with your MR system. If the scan completes successfully, there is probably a problem with the Invivo coil. Contact GE for further assistance. If you are unable to scan with the substitute coil, there may be a system problem related to this particular coil type.

Image quality is not what you expect it to be given the parameters selected.

• Review the selected protocol. If you are performing the Periodic Quality Assurance, be sure your protocol is identical to the protocol provided in your Systems Recommended Protocols. If you are performing diagnostic images, you may need to increase NEX or FOV.

• Perform a continuity check on the external cable (below). The continuity check must be performed by a GE authorized Service Engineer.

• Verify that there are no loops in the cables.

• Verify that there are no metal or ferromagnetic objects close to the coil, patient or magnet (i.e., safety pin, hair pin).

• Verify that the coil is properly positioned.

• Verify that your center frequency is within the frequency adjustment range for your system.

• Verify that the R1, R2 and TG values from the pre-scan are within normally expected ranges.

• Cleaning the electrical contacts that connect the upper and lower halves with Isopropyl Alcohol and a cotton swab has been demonstrated to improve the coil’s SNR on occasion. If you have not done so already, perform a MCQA (Multi Coil Quality Assurance) Test. If the values you obtain do not fall within normal operating parameters, investigate this further by performing a phantom scan with the body coil. For this test, be sure to remove the imaging coil from the magnet bore before you scan with the body coil. If you still have the same problems, there is probably an MR system problem. If the body coil scan is satisfactory, acquire a scan using both another coil of the same type plugged into the same system port (port A). If the image quality is visibly improved, there may be a problem with the Invivo coil. Contact GE for further assistance. If the image quality still suffers, there may be a system problem related to imaging with this type of coil.

There is a black line or signal void on the image.

Verify that there is no metal present in the area being scanned in or on the patient.

Some or all of the images appear shaded or exhibit uneven signal or banding.

Confirm that no metallic objects are located nearby, outside the FOV. This is especially important on images utilizing Fat Saturation. If Fat Saturation is being used, verify that the CFA fine adjustment has been optimized.

The system will not recognize the coil or scan with the coil attached.

Perform the cable continuity check. As follows:

1. RF Signal Channels Check: The center pins of the System Connector receive coaxial connectors are extremely fragile. Do not attempt to make any measurements at these center pins.
   Note:

   With the coil cable disconnected, use a multimeter to assure an open circuit condition exists between the designated pin and GND for each signal channel shown in Table 1.

   Table 4. Coil Cable Connector Short Circuit and Open Circuit Check

   Signal Channel	Coil Cable Connector Pin (Illustration 1)	System Connector (Illustration 2)
   RF 1	A17	C1
   RF 2	A15	C2
   RF 3	A10	C3
   RF 4	A21	C4
   RF 5	A4	D1
   RF 6	A8	D2
   RF 7	B12	D3
   RF 8	A13	D4
   GND	NOTE: The following pins are common to GND: A2-A3, A5, A7, A9, A11-A12, A14, A16, A19-A20, A22-A23, B1, B3-B6, B8-B11, B13-B18, B20-B21, and B23-B24.	K1-K8, M6, MC Shield

   

   If one or more of the readings indicate a short, replace the cable. If all of the above readings indicate an open circuit condition, proceed to the PIN Diode Control Channels Check.

2. MC bias line (DC line) Check: With the coil cable disconnected, use a multimeter to determine continuity between the designated pins for each signal channel below. Also verify that the control pins are not shorted to GND.

   Table 5. Coil Cable Connector Continuity Check

   Signal Channel	Coil Cable Connector (Illustration 1)	System Connector (Illustration 2)
   MC bias 1	A18	J1
   MC bias 2	B22	J2
   MC bias 3	B2	J3
   MC bias 4	B19	J4
   MC bias 5	A6	J5
   MC bias 6	B7	J6
   MC bias 7	A1	J7
   MC bias 8	A24	J8
   GND	NOTE: The following pins are common to GND: A2-A3, A5, A7, A9, A11-A12, A14, A16, A19-A20, A22-A23 B1, B3-B6, B8-B11, B13-B18, B20-B21, and B23-B24.	K1-K8, M6, MC Shield

   

   If one or more of the readings are > 3 ohms, replace the coil cable. If all readings are < 3 ohms, proceed to the PIN Diodes Check.

3. PIN Diodes Check With the coil cable connected to the coil, use a multimeter to measure the diode drop across the coil connector pins as detailed below. Use the System Connector illustration above for pin identification while performing this procedure.

   Table 6. Pin Diode Expected Readings

   System Connector
   Positive Lead		Negative Lead		Reading (V)
   J1		GND	[MC Shield]	1.7 ± 0.2
   GND	G1	J1		Open
   J2		GND	[MC Shield]	1.7 ± 0.2
   GND	G2	J2		Open
   J3		GND	[MC Shield]	1.7 ± 0.2
   GND	G3	J3		Open
   J4		GND	[MC Shield]	1.7 ± 0.2
   GND	G4	J4		Open
   J5		GND	[MC Shield]	1.7 ± 0.2
   GND	G5	J5		Open
   J6		GND	[MC Shield]	1.7 ± 0.2
   GND	G6	J6		Open
   J7		GND	[MC Shield]	1.7 ± 0.2
   GND	G7	J7		Open
   J8		GND	[MC Shield]	1.7 ± 0.2
   GND	G8	J8		Open

Inspect the coil for visible signs of wear. If the coil housings will not seat with each other or if the latch mechanism will not work properly, contact Service.

No finalization steps.