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МРТ RF Coils

The correct choice of the RF coil configuration for a given in-vivo investigation has an important impact on the quality of the results. In general, a RF coil configuration can contain one or several individual RF coils that from all together the RF coil configuration, i.e. the usage of different RF coils for signal excitation and signal detection. In this section, the most appropriate coil configurations with more than one RF-coil are presented, so-called “Cross-coil” configuration.

Signal excitation is done with a different RF coil than signal detection. In most cases, the excitation coil is a dedicated volume coil whereas the signal detecting coil is a small coil located as close as possible to the region of interest. The excitation coil in these coil configurations is optimized to avoid any residual RF coupling between the coils of the configuration. Highest sensitivity is achieved with cross coil setups and various dedicated receive-only coils or coil arrays are available.

Receive-only coils

Planar receive-only surface coils with various diameters

The planar receive-only surface coil is a general purpose RF coil that can be used for many different in vivo applications with small and well defined regions of interest. The RF coil preamplifier is mounted on the rat or mouse animal bed; the flexible RF coil end can be placed and fixed on any part of the body. The selection of the diameter of the RF coil depends on the size and depth of the region of interest, 10, 20 or 30 mm are available.

Technically, the coil is designed as a no tune/no match circular planar surface coil with various diameters. The RF coil elements are tuned and matched to full tissue coverage of an animal. The rapidly decaying B1 profile is typical for planar surface coils and provides excellent SNR close to the surface. The coil is equipped with a low noise preamplifier next to the RF coil element. These coils are to be used in combination with one of the transmit-only resonators.

Anatomically shaped receive-only rat brain or mouse brain surface coils

Applications on rat brain and mouse brain respectively include anatomical studies, fMRI, perfusion, and ASL. In all cases, the region of interest is focused on the entire brain of the rat or mouse. Highest sensitivity is achieved with this cross coil setups including a transmit-only signal excitation coil and these anatomically shaped receive-only coils.

This coil is designed for rat brain or mouse examination on single receiver instruments. These coils are mounted directly on the rat or mouse animal bed and are placed over the brain of the animal outside of the magnet once the animal preparation is finished. Both, animal and coil are then moved into the center of the magnet simultaneously. This approach allows the user easily to observe, control the correct position of the coil on the brain of the rat or mouse and the shape of the coil is optimized for brain.

Technically, the coil is designed as a no tune/no match circular polarized surface coil for rat body animal weights of up to 450 g or mouse body animal weights of up to 45°g. Its receive B1 profile gives an adequate image sensitivity over the entire brain of the animal. The coil provides an internal low noise preamplifier for best possible signal-to-noise performance. This coil is to be used in combination with one of the transmit-only resonators.

An accessory animal bed for rat and mouse brain applications is available.

Transmit/Receive coils

Arterial Spin Labeling-Coil for rat applications

For angiography and perfusion studies Arterial-Spin Labeling (ASL) is a powerful method without using contrast agents and provides a noninvasive approach for the direct measurement of the cerebral blood flow. These applications are require dedicated demands on the coil setup and the spectrometer. This coil is to be used in combination with one of the transmit-only resonators and highest sensitivity is achieved with a cross-coil setup including one of the anatomically shaped receive-only coils. The ASL-Coil is an integral part of the anatomically shaped animal bed-tip to be mounted on the rat base of the AutoPac™ system. The position of the Spin-labeling coil could be fine-adjusted manually when the animal is in place.

Transmit/receive surface coils

These linear transmit/receive coils are available with 10, 20 and 30 mm inner diameter that allow locally restricted excitation and detection of MR signals. These double tunable coils optimized for applications requiring 1H decoupling

In order to increase SNR of X nuclei signals as well as to simplifying NMR data some X nucleus applications require 1H decoupling capability of the coil. Our coils which cope this requirement are equipped with dedicated 1H block filters. This guarantees excellent 1H decoupling properties paired with a maximum SNR of X nucleus signals. The coils are tunable for 1H and X nucleus frequency and are pre-matched.

1H decoupling experiments are supported by the following coils1H/13C1H/31PDouble tunable coils for applications without 1H decoupling

1H decoupling is not required for all X nuclei in vivo applications. Therefore we provide also coils which combine excellent 1H performance and high SNR for the X nuclei tasks. The coils are tunable for 1H and X nucleus frequency and are pre-matched. The following combinations are supported:1H/23NaSingle tunable coil for 19F applications without 1H decoupling

This coil provides only one circuit with an extended tuning range covering 19F and 1H frequencies. The coil can be tuned to either 19F or 1H frequency. No 1H decoupling is therefore supported.

Surface coils are optimized for X nuclei applications for other nucleus will be built on request.