System and method providing preamplifier feedback for magnetic resonance imaging
A system and method for generating preamplifier feedback in magnetic resonance imaging (MRI) systems are provided. A preamplifier arrangement for the MRI system includes a plurality of preamplifiers with each of the preamplifiers connected to a different channel of a multi-channel coil array of the MRI system. The preamplifier arrangement further includes a feedback network connected to each of the plurality of preamplifiers with each of the feedback networks configured to generate negative feedback at one or more oscillation frequencies.
1. A preamplifier arrangement for a magnetic resonance imaging (MRI) system, the preamplifier arrangement comprising:
a plurality of preamplifiers, each of the preamplifiers connected to a different coil of a multi-channel coil array of the MRI system, wherein the preamplifiers are configured as on-coil preamplifiers coupled to the multi-channel coil array, and wherein each preamplifier and corresponding coil couple to form a set of oscillators, the oscillators having resonant frequencies at matched split peaks; and
a plurality of feedback networks, each feedback network comprising a parallel resonator, the parallel resonator being connected between an input and an output of a corresponding preamplifier, each of the feedback networks configured to generate negative feedback at the matched split peaks to suppress gain at frequencies of the matched split peaks, the negative feedback outside a clinically relevant frequency range of the MRI system.
2. A preamplifier arrangement in accordance with claim 1 further comprising a series connected resistor at an output of the parallel resonator.
3. A preamplifier arrangement in accordance with claim 1 wherein the feedback network is configured to generate feedback at ten megahertz above and below a resonance frequency of the multi-channel coil array.
4. A preamplifier arrangement in accordance with claim 1 wherein the feedback network is configured to generate feedback at three decibels from a resonance frequency of the multi-channel coil array.
5. A preamplifier arrangement in accordance with claim 1 wherein the preamplifier has an impedance of between about 0.8 Ohms and about 1.2 Ohms.
6. A receive section for a magnetic resonance imaging (MRI) system, the receive section comprising:
a plurality of channels connected to a receive coil array;
a plurality of preamplifiers, each preamplifier connected to a corresponding one of the channels, the preamplifiers configured as on-coil preamplifiers coupled to the receive coil array, the coupling of each preamplifier to a corresponding coil of the receive coil array forming a set of coupled oscillators having resonant frequencies at matched split peaks; and
a plurality of feedback networks, each feedback network connected between an input and an output of a corresponding preamplifier, the feedback networks each including a parallel resonator configured to provide selective negative feedback to the corresponding preamplifier, the feedback networks generating the selective negative feedback at the matched split peaks to suppress gain at frequencies of the matched split peaks, the negative feedback outside a clinically relevant frequency range of the MRI system.
7. A receive section in accordance with claim 6 wherein the parallel resonator is configured to generate feedback at split matched frequency peaks above and below a resonance frequency of the receive coil array.
8. A receive section in accordance with claim 6 wherein the preamplifiers have an impedance of between approximately 0.8 Ohms and approximately 1.2 Ohms.
9. A receive section in accordance with claim 6 wherein the preamplifiers comprise preamplifiers for a 3 Tesla MRI system.
10. A receive section in accordance with claim 6 wherein at least one of the feedback networks comprises a serially connected resistor at an output.
11. A receive section in accordance with claim 6 wherein the feedback networks are configured to generate the feedback without baluns.
12. A receive section in accordance with claim 6 wherein the feedback networks are configured to generate the feedback without additional oscillation suppression devices, the oscillations not resulting from crosstalk between a plurality of coils of the receive coil array.
13. A receive section in accordance with claim 6 wherein the preamplifiers are configured having a total phase shift of 180 degrees.
14. A receive section in accordance with claim 6 wherein the feedback networks are tuned at a resonance frequency of the receive coil array, the receive coil array comprising a plurality Of coil elements, wherein at least two adjacent coil elements are overlapped.
15. A method for suppressing oscillation in a multi-channel coil array of a magnetic resonance imaging (MRI) system, the method comprising:
receiving, at a plurality of preamplifiers of the MRI system, magnetic resonance signals from a corresponding plurality of coils of a multi-channel coil array of the MRI system, each of the preamplifiers configured as on-coil preamplifiers coupled to the multi-channel coil array and connected to a corresponding one of the coils, wherein each preamplifier and corresponding coil couple to form a set of oscillators, the oscillators having resonant frequencies at matched split peaks; and
generating frequency selective negative feedback with a plurality of feedback networks, each feedback network comprising a parallel resonator, the parallel resonator being connected between an input and an output of a corresponding preamplifier, each of the feedback networks configured to generate negative feedback at the matched split peaks to suppress gain at frequencies of the matched split peaks, the negative feedback outside a clinically relevant frequency range.
16. A method in accordance with claim 15 further comprising suppressing preamplifier oscillation without using additional oscillation suppression devices.