Ringing Down Time Measurement of a Receive Coil for NMR Tomography
نویسندگان
چکیده
The paper describes studies dealing with problems of the receive coil for NMR scanner connected via a preamplifier with high input impedance. Behaviour of the coil with preamplifier after pulses of RF signal was studied and an equation was derived and verified for investigation of it. The theory is demonstrated on a one-turn surface coil with rather large dimensions. Some parameters of a coil are measureable with difficulties and the derived theory can help to determine them more accurately. The technique of the high–impedance preamplifiers is seldom in experimental systems, though it can simplify their adjustment.
منابع مشابه
Employing dual frequency phase sensitive demodulation technique to improve the accuracy of voltage measurement in magnetic induction tomography and designing a labratoary prototype
Magnetic induction tomography (MIT) is a promising modality for noninvasive imaging due to its contactless technology. Being a non-contact safe imaging technique, MIT has been an appropriate method in compare to other electrical tomography. In this imaging method, a primary magnetic field is applied by excitation coils to induce eddy currents in the material to be studied and a secondary magnet...
متن کاملAssessment of the Characteristics of MRI Coils in Terms of RF Non-Homogeneity Using Routine Spin Echo Sequences
Introduction: One of the major causes of image non-uniformity in MRI is due to the existence of non-homogeneity in RF receive and transmit. This can be the most effective source of error in quantitative studies in MRI imaging. Part of this non-homogeneity demonstrates the characteristics of RF coil and part of it is due to the interaction of RF field with the material being imaged...
متن کاملReceive Coil for Low-field NMR Scanner Optimized Using Inductive Coupling
The paper describes a receive coil system for low-field NMR scanner intended for cardio measurements. The coil system is based on good qualities of surface coils accommodating them to volume measurements. The active volume of the coil is widened using two inductively coupled resonators. Signal from the coil system is amplified using a highimpedance preamplifier thus no special matching is neces...
متن کاملAn important reason for the use of low frequency NMR pulsed spectrometers in applications to Petrophysical studies is that
A NMR probe for low frequency and short recovery time is presented in this work. The probe contains the tuning circuit, diode expanders and quarter wavelength networks to protect the receiver from both the amplifier noise and the coil ringing following the transmitter power pulse. It also possesses a coil damper which is activated by of non active components. The probe performance shows a recov...
متن کاملContinuous magnetic field mapping with pulsed 1 H NMR probes
Non-ideal magnetic field profiles can severely degrade image quality, especially with fastimaging sequences, phase contrast and diffusion tensor to mention a few. Artifacts arise from imperfect gradient performance, non-homogenous B0 field and/or from eddy-currents. Previously, a method to measure magnetic fields with dedicated sensors, simultaneously during image acquisition, and apply the inf...
متن کامل