An Apparatus for multi-channel small sample Transmit/Receive RF Signal calibration in Magnetic Resonance Imaging
Publication Date: 2005-Oct-07
The IP.com Prior Art Database
In an embodiment, an apparatus is designed for fast calibration of MRI Scanner. The MRI scanner is fitted with multiple small sample Transmit / Receive coils and supplying/receiving RF signal to/from them simultaneously, while minimizing interaction between channels. This architecture of calibration significantly reduces the time to collect data thus reducing system calibration time.
FIELD OF THE INVENTION
 This invention relates generally, to Magnetic Resonance as used in Medical Imaging field and specifically in the area of Calibration of MRI System.
BACKGROUND OF THE INVENTION
 In order to calibrate and characterize the operation of an MR scanner, acquisition of magnetic field data as a function of both time and space is required . One example of the use of this type of data is compensating for the effects of eddy currents on the magnetic field. Methods have been proposed to collect this data using phantoms with imaging methods [4,6,7] or to collect data using point samples [1-3].
 There are two eddy current calibration methods used at this time [1-3]. Both collect magnetic field data as a function of time using small samples placed in six different locations in the bore and decompose the resultant data into B0 and linear components. These methods are designed to transmit and receive signals from a pair of samples using a single transmit and receive channel by alternating the signal paths using a MUX. At 1.5T, two samples are used. To collect all six bore locations, the operator must move the samples during the procedure. At 3T, an apparatus is being used that has six samples located in the correct relative positions. The data is still acquired in pairs using a single receive channel and a more complicated MUX than used at 1.5T.
 Using these calibration methods is a time consuming process. Calibrating a single mode of a gradient coil currently takes approximately 2-3 hours
BRIEF DESCRIPTION OF THE DRAWINGS
 Figure 1 shows a prototype of the proposed apparatus in an MRI scanner. Transmit, receive and DC signals are routed to the T/R board affixed to the rear of a plexiglass 'T'. The RF coils and associated tuning circuits are mounted to the plexiglass in the correct positions and RF cables connect the coils to the T/R board.
 Figure 2 shows a representation of the assembly level and subsystem interconnects within the proposed invention.
 Figure 3 shows a representation of the T/R board designed to split the transmit signal, route the signals to and from the RF coils, and amplify the signals received from the RF coils.
DETAILED DESCRIPTION OF THE INVENTION
 Various embodiments of this invention provide an apparatus for multi-channel small sample Transmit/Receive RF Signal calibration in Magnetic Resonance Imaging . However, the embodiments are not limited and may be implemented in connection with other systems such as NMR or Nuclear Imaging.
 The proposed invention is an apparatus designed to transmit/receive RF signals to/from multiple small sample RF coils simultaneously. The design pays special attention to minimizing the interaction between the channels. Collecting data in this fashion significantly reduces the amount of time needed t...