3.0T General Purpose Flex Coil

The 3.0T General Purpose (GP) Flex Coil consists of one major assembly shown below. The unit is 22 in (55.6 cm) long (not including straps) by 9 in (22 cm) wide. It has two mesh windows that indicate the open center of the two coils and aid in positioning. Two 31 in (78.5 cm) straps are attached to one end of the coil fabric. The undersides of these straps are covered with Velcro that attach to a Velcro hook strip at the other end of the coil, and to four Velcro hooks located above and below the mesh windows. A 72 in (183.3 cm) RF cable exits the material on one of the long sides and has a BNC connection that attaches to the surface coil quick disconnect box.

Storage and transportation conditions:

• Ambient temperature range of –40 °F to +158 °F (–40°C to +70 °C)

• Relative humidity range of 40% to 95%, non-condensing

• Atmospheric pressure range of 525 hPa to 1013 hPa

Dimensions: 21.9 in x 8.7 in x 1.6 in (55.6 cm x 22 cm x 4 cm) (excluding cable assembly)

Strap length: 31 in (78.5 cm)

Weight: 1.3 lb (575 g) maximum

The 3.0T GP Flex Coil design is a linear, receive-only flexible coil. It consists of two loops that are serially connected to create a co-rotating, saddle coil pair. If the loops are positioned in a more open fashion (that is, they move farther away from each other toward a planar or flat configuration), the image uniformity decreases. For close positioning, do not overlap the coil ends. Doing so will not damage the coil, but performance will suffer.

When aligned properly, this saddle design provides exceptional uniformity across the sensitive volume of the coil and a minimum of bright spots or high-intensity areas. For optimal positioning, the circular shape should be maintained with the two mesh windows 4 in (10 cm) apart and the coil ends 2 in (5 cm) apart. Some deviation from the optimal position does not significantly degrade the uniformity. Therefore, this coil can be used in anatomical areas such as the hip, brachial plexus, larger knees, or ankle.

• The coil consists of one major assembly shown in Figure 1. The two loops are in a flexible material covered with fabric. This allows the coil to bend in one direction, making it easy to wrap around the anatomy of interest.

• The block diagram of the antenna electronics is shown in Figure 2. The two flex PCB wings on either side of the rigid PCB form the loops. The rigid PCB has a matching network that matches the loaded antenna to 50 ohms and an active blocking network. The blocking network consists of a single PIN diode and a tuned LC network. The diode is forward biased whenever the body coil transmits. The external cable is connected to the antenna at a right angle SMA jack. The flex PCB has passive blocking networks that consist of a Schottky diode and a tuned LC network.

On a periodic basis, such as during planned maintenance, perform these quality assurance checks to ensure the coil is operating properly.

1. Check external cable for cracks or cuts.

2. Perform coil imaging verification (system level SNR check). See Coil Imaging Performance Verification and record the data values in the data sheet.

Perform a system level SNR check. See Coil Imaging Performance Verification.

1. Select the diode test function on the digital multimeter (DMM).

2. Connect the positive lead of the DMM to the center pin of the BNC on the external cable, and connect the negative lead to the main housing/ground of the BNC.

   

3. Flex the external cable, especially near the connectors and the strain relief, and verify that a reading of 0.400 to 0.600 remains on the DMM with no instability or fluctuations.

4. Connect the positive lead of the DMM to the main housing/ground of the BNC on the external cable, and connect the negative lead to the center pin of the BNC.

5. Flex the external cable, especially near the connectors and the strain relief, and verify that a reading of Infinity remains on the DMM with no instability or fluctuations.

6. If the cable fails any of the above tests, replace it. Refer to External Cable Replacement External Cable Replacement.

There is only one PIN diode in this antenna. The following procedure determines if the PIN diode is defective.

1. Select the Diode Test function on the DMM.

2. Connect the positive lead of the DMM to the center pin of the BNC on the external cable, and connect the negative lead to the main housing/ground of the BNC. See Figure 5.

   Verify a reading of 0.400 to 0.600 on the DMM.

   • If a reading below 0.400 is observed in either direction, either the output cable is shorted or the PIN diode is defective.

   • If a reading above 0.600 is observed, the PIN diode is defective.

3. Connect the positive lead of the DMM to the main housing/ground of the BNC on the external cable, and connect the negative lead to the center pin of the BNC.

   Verify a reading of Infinity on the DMM. If a reading of Infinity is observed in both directions, either the output cable is open or the PIN diode is open.

If necessary, a 10% bleach solution can be used for more rigorous cleaning; however, some discoloration of the strap, cover, or pad may occur.

Contact GE-authorized service personnel for disposal of the coil at the end of product life.

Refer to the illustrations that follow to disassemble the coil.

To reassemble the coil:

1. Place the cover back on the posts and press it until it snaps into place.

2. Push the foam flap under the jacket.

3. Carefully put the fabric flap into place, making sure the Velcro on the edges lines up with the Velcro on the jacket. Tuck the end of the flap under the jacket.

4. Press the Velcro while making sure no edges are left open.

1. Disassemble the coil as instructed in Assembly/Disassembly of Coil. Unscrew the two nylon screws and remove the strain relief upper cover.

2. Unscrew (use two 8 mm wrenches, one on the circuit board female connector and one on the male cable connector), and remove the male SMA cable connector from the circuit board. Be careful not to twist the female SMA connector from the circuit board.

   

3. Remove the external cable from the coil.

4. Install the new cable. Stabilize the circuit board and the connector on the circuit board.

   Note:

   Too much torque (>2 kgf-cm) can cause damage.

5. Reattach the strain relief, and reassemble the coil per Assembly/Disassembly of Coil.

1. Refer to Renewal Parts for the hardware kit part number.

2. To replace the cover assembly, refer to Assembly/Disassembly of Coil.

3. To replace the upper strain relief block and the two screws, refer to External Cable Replacement.

4. If a plastic standoff breaks, it can be pulled out using needle-nose pliers. Insert a new standoff in its place, making sure that the flat end goes in first.