• Topic ID: id_13106893
  • Version: 3.0
  • Date: Aug 29, 2019 1:51:55 AM

1.5T 8-Channel High Res Brain Array Troubleshooting

Personnel Requirements

Required Persons Procedure
1 30 min.

Overview

The following suggestions can be used to troubleshoot common problems with the 1.5T HD 8-Channel High Resolution Brain Array Coil by Invivo, Catalog Number M3335LZ.

Tools and Test Equipment

Digital Volt Meter

Procedure

Receiving No Signal

Problem:

Unable to Pre-Scan or Scanning and Unable to Receive a Signal.

Possible Solution:

  • Verify that the port which is used to plug in the coil either has a green light illuminated (Port A or Port B) or a green lock (Port P1, P2, P3 or P4) indicated. This indicates the coil is properly plugged into the system.

  • Verify that the system correctly detected the coil by checking the Currently Connected in the GUI as shown in the example in Figure 1.

Figure 1. Currently Connected Coils Window

  • 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. The Continuity Check must be performed by a GE-authorized Service Engineer. (Refer to Cable Continuity Check).

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

  1. If still unable to receive 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 scanning with the body coil. If still not receiving a signal, the problem may be with the MR system.

  2. If unable to scan with the substitute coil, there may be a system problem related to this particular coil type.

  3. If the scan completes successfully, there may be a problem with the Invivo coil. Contact GE for further assistance.

Image Quality

Problem:

Poor IQ, Shaded Images or MCQA Fails.

Possible Solution:

  • Perform a Continuity Check on the external cable. The Continuity Check must be performed by a GE-authorized Service Engineer. (Refer to Cable Continuity Check.)

  • 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 the center frequency is within the frequency adjustment range for the system.

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

  1. If not already done, perform a system Quality Assurance phantom test. If the obtained values do not fall within normal operating parameters, investigate 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 scanning with the body coil. If still experiencing the same problems, there could be an MR system issue.

  2. If the body coil scan is satisfactory, acquire a scan using another coil of the exact same type (receive-only, phased array or transmit/receive - whichever applies) and the same system coil selection. 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.

Artifacts

Problem:

Black Line or Signal Void on Image.

Possible Solution:

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

Problem:

Some or All Images Appear Shaded or Exhibit Uneven Signal or Banding

Possible Solution:

  • 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 was optimized.

Cable Continuity Check

Problem:

System Does Not Recognize Coil or Reports MC Bias Errors with Coil Attached.

Possible Solution:

Perform the cable continuity check as follows:

RF Signal Channels Check

note:

The center pins of the System Connector that receive coaxial connectors are extremely fragile. Make sure you are very careful when measuring so that you do not break the center pins.

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

  2. If one or more of the readings indicate a short, replace the cable. If all of the readings indicate an open circuit condition, proceed to the next section.

Table 1 Signal Channel Expected Readings
Signal Channel Coil Cable Connector Function
MC-1 Center A7 GND
MC-2 Center A6 GND
MC-3 Center A5 GND
MC-4 Center A4 GND
MC-5 Center A3 GND
MC-6 Center A2 GND
MC-7 Pin 2 GND
MC-8 Center A1 GND
GND Note: The points shown in Figure 2 are common to GND. All outer [A] shells to Pins 1 and 3.

Figure 2. Coil Cable Connector

PIN Diode Control Channels Check

  1. With the coil cable disconnected, use a multimeter to determine continuity between the designated pins for each control channel below. Verify that the control pins are not shorted to GND. Refer to Table 2.

  2. If one or more of the readings are >3 ohms, replace the coil cable. If all readings are <3 ohms, proceed to the next section.

Table 2 External Cable Expected Readings B
Control Channel Coil Cable Connector System Connector
MC Bias 1 Pin 17 J1
MC Bias 2 Pin 16 J2
MC Bias 3 Pin 15 J3
MC Bias 4 Pin 14 J4
MC Bias 5 Pin 4 J5
MC Bias 6 Pin 5 J6
MC Bias 7 Pin 6 J7
MC Bias 8 Pin 7 J8
GND Note: The points in Figure 3 are common to GND. All outer [A] shells to Pins 1 and 3. K1-K8, M6

Figure 3. System Connector

PIN Diodes Check

  1. With the coil cable connected to the coil, use a multimeter to measure the diode drop across the coil connector pins as detailed in Table 3. Refer to Figure 3 for pin identification while performing this procedure.

  2. If one or more of the readings indicate a short, replace the coil. If all of the readings are correct, perform Coil Imaging Performance Verification again. If the problem still exists, replace the 1.5T HD 8-Channel High Resolution Brain Array Coil.

Table 3 Pin Diode Expected Readings
System Connector Reading
Positive Lead Negative Lead
J1 GND [K1] 1.7
GND [K1] J1 Open
J2 GND [K2] 1.7
GND [K2] J2 Open
J3 GND [K3] 1.7
GND [K3] J3 Open
J4 GND [K4] 1.7
GND [K4] J4 Open
J5 GND [K5] 1.7
GND [K5] J5 Open
J6 GND [K6] 1.7
GND [K6] J6 Open
J7 GND [K7] 1.7
GND [K7] J7 Open
J8 GND [K8] 1.7
GND [K8] J8 Open

Mechanical Parts Wear

Inspect the coil for visible signs of wear. If the coil housings will not seat with each other or if the latch mechanism does not work properly, refer to the FRU list for replacement parts.