Miniaturized fiber optic transmission system for magnetic resonance imaging signals

Abstract

In conventional Magnetic Resonance Imaging (MRI) instruments, after echo signals are received by an MRI coil, they are transmitted through an ultra low noise transmission system consisting of electrical cables. Although this design proved to be effective over the years, there are recent developments in the MRI technology which require a better, more sophisticated design. One of these emerging technologies is “parallel imaging”, where total size of interconnections is the primary problem, and the other is “interventional MRI”, where safety needs to be improved. The Miniature Fiber Optic Transmission System was developed to serve these needs. The system consists of a receiver MRI coil with passive detuning, a two-stage low-noise preamplifier and a low-noise laser diode connected to a photodetector with fiber optic cable in between. The overall noise figure of the system is measured to be lower than 1 dB which guarantees that total signal-to-noise ratio (SNR) reduction in the images due to optical MRI signal transmission system is less than 15%. Total power consumption is 50mW and the device is switchable by another fiber optic line, which can also control active detuning circuit if it is present. A prototype device was tested in a GE 1.5 Tesla MRI instrument and several images were acquired with a slight SNR drop, due to problems with passive detuning. We believe that this design will significantly reduce the size of parallel imaging arrays and enable placement of internal coils into body cavities without providing any safety hazard to the patient, such as electrical shock or burns.