Surgery – Diagnostic testing – Measuring fluid pressure in body
Reexamination Certificate
2001-04-26
2004-01-27
Paik, Sang Y. (Department: 3742)
Surgery
Diagnostic testing
Measuring fluid pressure in body
Reexamination Certificate
active
06682492
ABSTRACT:
The present invention relates to the examination of an object, such as a human body, for example, and possibly to the simultaneous guidance of a treatment procedure.
The nuclear magnetic resonance phenomenon (NMR) has already been applied in medicine to magnetic resonance imaging (MRI) for more than ten years. The design of various pieces of magnetic imaging equipment and the use of various techniques have been dealt with in a number of books and the latest research results are currently published in several scientific journals focusing exclusively on that particular field.
A common feature for all magnetic imaging devices is the positioning of an object to be imaged, often a patient, in a stationary magnetic field B
0↑
which is produced by a magnet. In addition to this, the magnetic field is subjected to a linear magnetic-field change, a gradient, which is effected by means of a special gradient coil. The magnetic imaging devices are provided with three gradients G
x
, G
y
, and G
z
, which represent the change of a magnetic field in the direction of an x, y, and z axis, respectively. The gradients are used for encoding positional information from the magnetically resonating material, most commonly protons, of an object to be imaged, by frequency-modulating the resonance. The signal for magnetic imaging is produced by means of radio-frequency (RF) coils, which excite the resonance and function as a signal receiver. The signal is analyzed (Fourier-transformed) for its frequency content, thereby determining a signal distribution in the direction to be examined. The literature discloses a variety of methods for applying this basic technique for producing 2- or 3-dimensional images by using special imaging sequences, which are all based on the encoding of an NMR signal effected by means of gradients in x, y, and z directions.
The open-configuration magnetic imaging equipment offers a possibility of performing procedures, for example biopsies, during patient imaging. Certain objects, for example brain tumors, osteopecilia, soft tissue transformations, or liver tumors, are best discernible in magnetic imaging and, thus, the procedure would be most precisely applicable in the guidance of magnetic imaging. However, this requires that the position of an operation instrument in a tissue during the procedure be known with high accuracy.
Prior known are operation instruments disclosed in reference Longmore: U.S. Pat. No. 4,827,931, which are completely or partially made of a material visible in a normal magnetic image. Prior known are also methods disclosed in references Werne R: WO 98/22022, Werne R: U.S. Pat. No. 5,782,764, Ratner A: U.S. Pat. No. 4,989,608, Ratner A: U.S. Pat. No. 5,154,179, wherein an operation instrument is provided either in a container or otherwise with an NMR active substance, having a relaxation time which is different from that of the tissue, for creating a contrast distinction between the operation instrument and the tissue. It is characteristic of these methods that the NMR signal emitted by these instruments is not enhanced, but the visibility is only based either on a high density (e.g. water) of the nuclei emitting the NMR signal or on a relaxation time other than that of the tissue. Thus, the visibility of these instruments in a tissue is weak and requires that the imaging process be performed by using either very thin slices or by selecting such imaging sequences that the surrounding tissue provides very little signal. The use of thick slices in imaging is desirable, e.g. when monitoring the progress of an instrument in a curved blood vessel or generally when using pliable instruments, e.g. thin needles. In terms of monitoring a procedure, it is preferable to obtain sufficient signal from a tissue in order to make the surrounding tissue visible simultaneously with the instrument. There are prior known extra-object stereotactical frames as set forth in reference Cosman E: U.S. Pat. No. 4,618,978, which enable determining the position of the object in a tissue. Prior known is the use of operation instruments disclosed in references: Mueller P et al.: MR-guided aspiration biopsy: needle design and clinical trials, Radiology 161 pp. 605-609 (1986), Lufkin R et al.: MR body stereotaxis: an aid for MR-guided biopsies, Journal of Computer Assisted Tomography 6 pp. 1088-1089 (1988), van Sonnenberg E, et al.: A wiresheath system for MR-guided biopsy and drainage, AJR 151 pp. 815-817 (1988), Lufkin R. Teresi L, Chiu L, Hanafee W: A technique for MR-guided needle placement, AJR 151 pp. 193-196 (1988), Bakker C, Hoogeveen R, Weber J, et al.: Visualization of dedicated catheters using fast scanning techniques with potential for MR-guided vascular interventions, Cordington R: U.S. Pat. No. 4,572,198, Magnetic Resonance in Medicine 36 pp. 816-820 (1996), Glowinski A, Adam G, Bucker A, et al.:Catheter visualization using locally induced, actively controlled field inhomogeneities, Magnetic Resonance in Medicine 38 pp. 253-258 (1977), which cause the weakening of an image signal from the area of an operation instrument and its immediate vicinity. Also prior known is an instrument set forth in reference Werne R: U.S. Pat. No. 5,744,958, which is fitted with a conductive foil. The instrument is not provided with its own source for an NMR-frequency signal, nor is the foil transparent to an NMR-frequency signal, but the instrument has its visibility based on the distortion of a surrounding-tissue emitted signal in the vicinity of the instrument, and the intensity of distortion is controlled by the foil thickness. The positional information produced by the above-described operation instruments is generally perceived as a loss of the signal, while positive contrast would be desirable.
According to reference Dumoulin C: U.S. Pat. No. 5,419,325, it is prior known to fit the instrument with a Faraday shield for protection against external RF excitation. Prior known is a method disclosed in reference Young I: U.S. Pat. No. 5,409,003, wherein the nuclei emitting an image signal perform limited motion in the vicinity of the surface of an instrument, and no fading of the signal as a result of diffusion shall occur. Reference Yates D: U.S. Pat. No. 5,188,111 anticipates an instrument, having a stem portion which is pliable in a tissue and whose end carries a sensor capable of tracking action.
Prior known is a method described in references Dumoulin et al.: U.S. Pat. No. 5,271,400, Dumoulin et al.: U.S. Pat. No. 5,307,808, Dumoulin et al.: U.S. Pat. No. 5,318,025, Souza et al.: U.S. Pat. No. 5,353,795, Leung D A, et al.: Intravascular. MR tracking catheter, AJR 164 pp. 1265-1270 (1995), wherein the operation instrument is fitted with one or more small-sized RF coils, whose position is detected by means of an imaging method applied in magnetic imaging. Furthermore, references Darrow et al.: U.S. Pat. No. 5,445,151, Dumoulin et al.: U.S. Pat. No. 5,447,156 describe, as an application of this technique, the imaging of blood vessels and the measurement of parameters associated with circulation. Reference Young I: U.S. Pat. No. 5,303,707 discloses a method, wherein a small-sized gradient coil is attached to the instrument. Prior known is also a method according to reference Ocali O. et al: Intravascular magnetic resonance imaging using a loopless catheter antenna, Magnetic Resonance in Medicine 37 pp. 112-118 (1997), wherein the catheter functions as NMR-frequency antenna and gathers a tissue signal from the immediate vicinity of the antenna. Prior known are methods set forth in references: Silverman S et al.: Interactive MR-guided biopsy in an open-configuration MR-imaging system, Radiology 197 pp. 175-181 (1995), as well as Roemer P. et al: U.S. Pat. No. 5,365,927, wherein fixing the position of an operation instrument is based on detecting the position of small transmitters mounted on the stem portion. One prior known method is described in reference Kaufman L: U.S. Pat. No. 5,155,435, wherein the position of an operation instrument is projected on top of a previously acquired anat
Blank Rome LLP
Paik Sang Y.
Robinson Daniel
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