4ch Open Breast Coil

SCOPE

This is a service manual for the Open Breast Coils for 1.5T

Theory of operation

The Phased Array Open Breast Coils consist of one coil with 4 elements. Two of the elements are saddle coils and two of the elements are Helmholtz coils. Each element contains items 1, 2, and 3. Item 1 is a tuning and decoupling circuit, which uses passive decoupling via back to back fast acting diodes which are enabled by the RF pulses. When the diodes short, the network creates a high impedance block to eliminate decoupling artifact and interaction with the excitation field. Item 2 is a tuning, matching, and decoupling circuit which not only tunes and matches the coil to the system resonant frequency and matches the coil to 50 ohms when loaded, it also provides decoupling when the DC bias on the center conductor of the input cable is positive. Item 3 provides the proper phase shift between the system preamplifier and item 2 to create the phased array decoupling required during receive.

Scanner and coil verification testing procedures:

Be sure that you choose the correct coil, and activate the desired coils from the menu selection on the surface coil screen. The coil chosen must be R_BREAST, L_BREAST, or 2_BREAST.

Position the Breast Coil in the center of the patient cradle. Place two phantom holders and two 4.38" diameter sphere phantoms (provided with your Signa System Part No. 46-317586G1) in the left and right coil. Activate one of the above coil settings from your operator's console.

Use the following spin echo sequence, TE=20mS, TR=300mS, 32cm FOV axial, 5mm thick, 5mm spacing, 256x128, and 1 NEX or equivalent sequence. Scan using Auto Pre-scan. If Auto Pre-scan does not complete successfully, do not use the coil clinically. Upon completion of prescan, execute the scan. Window the scan as you normally would (window levels vary from system to system depending upon your hardware revision level).

If the image has signal voids, distortions, or black streaks, discontinue use of the coil. If the image is excessively noisy, repeat the scan using the GE 5 inch general purpose coil for 1.5T supplied with your system. If the 5 inch coil image or alternate coil image exhibits similar artifacts, the problem likely lies with the MRI system.

Parts List: