Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-07-29
2001-11-13
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S422000, C324S307000, C324S309000, C324S318000
Reexamination Certificate
active
06317619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic resonance (MR) apparatus and methods for reconstructing images from signals received by a moveable RF coil assembly, the current three-dimensional (3D) position and 3D orientation of which guides the location of the nuclear magnetization excited during the imaging process, and also relates to a RF coil assembly for receiving and transmitting capable of being moved across a patient while guiding the location of the MR imaging.
2. Description of the Related Art
Conventional magnetic resonance (MR) is based on batch acquisition and retrospective image reconstruction and patient diagnosis. In such conventional MR imaging, during a preparation phase, the patient along with necessary RF receiving coils are arranged in an examination zone. During actual MR measurement, which typically requires a comparatively long time, usually a large volume, either multiple 2-D slices or one 3-D image, within the sensitivity range of the receiving coil is measured. Patient diagnosis can be made only after collection of a complete set of MR data and its reconstruction into a diagnostic image. If the region of interest in the patient turns out to be situated outside the planned examination zone or of the sensitivity range of the receiving coil, the patient and the receiving coil have to be repositioned, and the entire measurement repeated.
In contrast, a different and interactive way of imaging is known from ultrasound imaging. There, the position and orientation of the ultrasound probe necessarily determines the imaging plane, and ultrasound images are displayed in rapid succession, even in real time, as they are received by the probe. Accordingly, the ultrasound imaging plane can be interactively determined by manipulation of the ultrasound probe in order to obtain at once images of greatest clinical usefulness.
In recent years several developments have occurred which have begun to alleviate some problems previously associated with MR imaging. First, an almost real-time capability has been developed, because the speed with which MR images can be acquired has been significantly reduced by means of improved magnetic gradient field systems and of new imaging procedures. Second, new main-field magnet designs have been developed which allow for significantly improved patient access in comparison to prior tunnel-shaped MR systems. Finally, noteworthy developments in other fields, such as the field of image-guided surgery, include position detection systems capable of accurate guidance of instruments during critical surgical procedures, and position detection systems capable of accurate positioning of catheters in a patient.
What remains lacking, however, in the current state of the MR arts is apparatus and methods which provide for interactive MR examination having the known flexibility of ultrasound methods.
Citation of a reference herein, or throughout this specification, is not to be construed as an admission that such reference is prior art to the Applicant's invention of the invention subsequently claimed.
SUMMARY OF THE INVENTION
The objects of the present invention are to provide methods, apparatus, and devices which overcome the above identified problems in the current state of the art, namely which provide for an interactive way for an operator to work with an MR apparatus.
It is a general object of the present invention to provide MR methods and apparatus according to which a moveable RF coil defines the 3D position and 3D orientation of the region to be imaged. The provided methods are implemented on an apparatus having a position detection system, and use the 3D position and 3D orientation of the moveable RF coil to determine parameters of the MR measurement sequence so that the region imaged is situated within the sensitivity volume of the moveable RF coil. Alternatively, the region imaged is determined simply relative to the 3D position and 3D orientation of the moveable RF coil, although not necessarily within the sensitivity volume of the coil. In either case, the moveable RF coil can then be arbitrarily moved across the examination zone while the region imaged follows automatically and interactively.
It is a particular object of the present invention to provide a moveable RF coil assembly that provides for imaging regions of interest of a patient that are defined interactively. The RF coil assembly includes a combination of a surface RF coil for receiving and transmitting and means to interact with a position detection system. The RF surface coil transmits RF pulses exciting nuclear magnetization in a nearby part of a patient and receives MR imaging signals thereby generated.
The position detection system determines the 3D position and 3D orientation of the moveable RF surface coil in order that nuclear magnetization can be excited within the sensitivity range of, or at least be determined by, the RF coil. The present invention is adaptable to many alternative position detection systems, such as optically-based systems, ultrasound based systems, systems using MR-active microcoils, systems dynamically locating the sensitivity profile of the RF coil, systems based on image registration, and so forth.
In preferred embodiments, the moveable RF coil assembly also includes operator assistance features, such as an LCD display for MR images or other operator information mounted in its proximity, for example on a handle of the coil assembly, means for the operator to conveniently input control parameters to the MR apparatus, an additional user interface, and so forth.
It is a further particular object of the present invention to provide an MR apparatus advantageously useable with such a moveable RF coil assembly. Preferably, such an MR apparatus includes a more open magnet configuration, a position detection system, and a control means for determining gradient field and RF pulse sequence parameters in view of the determined 3D position and 3D orientation of the moveable RF coil assembly, so that the regions of the patient indicated by the coil assembly are imaged. Such an MR apparatus permits the operator to move the RF coil assembly arbitrarily across the patient while the position detection system automatically tracks the coil and the MR imaging is controlled accordingly. A region of interest can thus be interactively defined and imaged.
It is an additional particular object of the present invention to provide methods for using such an MR apparatus and moveable RF coil assembly. These methods include determining the 3D position and 3D orientation of the moveable RF coil from data returned by the position detection system, and the subsequent use of the determined 3D position and 3D orientation to select parameters of the applied MR sequence. These methods apply different, preferably high-speed, imaging sequences, appropriate in these circumstances, and reconstruct MR images from received signals in a conventional manner. For example, individual and multiple slices at various 3D positions and 3D orientations with respect to the current 3D position and 3D orientation of the moveable RF coil assembly can be imaged by high-speed spin-echo protocols, for example the RARE sequence, or high-speed gradient echo protocols, for example the EPI sequence. Also, linear images can be obtained by two-dimensional excitation sequences, and can then be displayed in a manner similar to the M-mode or B-mode displays known from ultrasound imaging. Reduced field of view excitation sequences can be used to provide more rapid acquisition with reduced aliasing problems.
It is yet an additional particular object of the present invention to provide a carrier medium with program instructions for causing a programmable control means of an MR apparatus to control the MR apparatus to function according to the methods described herein.
In detail, these objects are by the following specific embodiments of this invention. In a first embodiment, this invention includes a method for generating magnetic resonance (MR) images by an
Boernert Peter
Schaeffter Tobias Richard
Weiss Steffen
Smith Ruth S.
U.S. Philips Corporation
Vodopia John F.
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