DE102012023124B4 - Method and device for visualizing interventional instruments in magnetic resonance imaging via sequence-triggered energization with evaluation of the magnitude and phase images - Google Patents

Method and device for visualizing interventional instruments in magnetic resonance imaging via sequence-triggered energization with evaluation of the magnitude and phase images Download PDF

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DE102012023124B4
DE102012023124B4 DE102012023124.5A DE102012023124A DE102012023124B4 DE 102012023124 B4 DE102012023124 B4 DE 102012023124B4 DE 102012023124 A DE102012023124 A DE 102012023124A DE 102012023124 B4 DE102012023124 B4 DE 102012023124B4
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magnetic resonance
instrument
instruments
visualization
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Hanne Wojtczyk
Hansjörg Graf
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/285—Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR
    • G01R33/287—Invasive instruments, e.g. catheters or biopsy needles, specially adapted for tracking, guiding or visualization by NMR involving active visualization of interventional instruments, e.g. using active tracking RF coils or coils for intentionally creating magnetic field inhomogeneities
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14—Probes or electrodes therefor
    • A61B2018/1405—Electrodes having a specific shape
    • A61B2018/1425—Needle
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/36—Image-producing devices or illumination devices not otherwise provided for
    • A61B90/37—Surgical systems with images on a monitor during operation
    • A61B2090/374—NMR or MRI
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/39—Markers, e.g. radio-opaque or breast lesions markers
    • A61B2090/3954—Markers, e.g. radio-opaque or breast lesions markers magnetic, e.g. NMR or MRI

Abstract

Verfahren zur Visualisierung eines oder mehrerer interventioneller Instrumente in der Magnetresonanzbildgebung über bildgebungssequenz-getriggerte zeitweise Instrumenten-Bestromung durch Visualisierungsstrom zur Erzeugung eines gewünschten Störmagnetfeldes zur Störung des magnetischen Grundfeldes des Magnetresonanztomographen, der auf vordefinierten Leiterstrukturen mittels Regelung eines anpassbaren Gleichstroms oder Gleichstromanteils des oder der mehreren Instrumente fließt, mit Auswertung der Magnituden- und Phasenbilder, dadurch gekennzeichnet, dass der Visualisierungsstrom für ein oder mehrere dieser Instrumente unabhängig von der gewählten Bildgebungstechnik der Magnetresonanz nur zu Zeiten geschaltet wird, in welchen keine bezüglich der Ortskodierung zur Ermittlung der Darstellung der Anatomie störungsanfälligen Bildgebungsgradienten geschaltet sind, und dass durch eine Überlagerung des so erhaltenen Instrumentenbildes als Phasenbild mit dem gleichzeitig aufgenommenen Magnitudenbild mit Darstellung der Anatomie eine präzise Instrumentenlokalisation ermöglicht ist.A method of visualizing one or more interventional instruments in magnetic resonance imaging via imaging sequence triggered temporal instrument energization by visualization current to produce a desired perturbing magnetic field perturbing the magnetic field of the magnetic resonance tomograph based on predefined conductor structures by controlling an adjustable DC or DC component of the one or more instruments flows, with evaluation of the magnitude and phase images, characterized in that the visualization current is switched for one or more of these instruments, regardless of the selected imaging technique of magnetic resonance only at times in which switched with respect to the spatial encoding for determining the representation of the anatomy failure prone Bildgebungsgradienten are, and that recorded by a superimposition of the thus obtained instrument image as a phase image with the same time Magnitude image showing the anatomy enables precise instrument localization.

Description

Verfahren und Vorrichtung zur Visualisierung interventioneller Instrumente in der Magnetresonanzbildgebung über sequenz-getriggerte Bestromung mit Auswertung der Magnituden- und Phasenbilder.Method and device for visualizing interventional instruments in magnetic resonance imaging via sequence-triggered energization with evaluation of the magnitude and phase images.

Die Visualisierung von Instrumenten bei MRT-geführten Intervention wird üblicherweise über den Paramagnetismus des Instrumentenmaterials realisiert. Das magnetische Grundfeld des Tomographen wird in der Nähe des Instruments verzerrt, das Instrument lässt sich über Artefakte visualisieren (zum Beispiel „IEEE TRANSACTIONS ON MEDICAL IMAGING”, Bd. 19, Nr. 12, Dez. 2000, S. 1248–1252).The visualization of instruments in MRI-guided intervention is usually realized via the paramagnetism of the instrument material. The basic magnetic field of the tomograph is distorted in the vicinity of the instrument, the instrument can be visualized via artifacts (for example "IEEE TRANSACTIONS ON MEDICAL IMAGING", Vol. 19, No. 12, Dec. 2000, pp. 1248-1252).

In der Literatur sind neben der passiven Visualisierung auch aktive Techniken beschrieben, bei welchen über am Instrument angebrachte elektrische Leiter gezielt magnetische Störfelder in dessen Nähe erzeugt werden ( DE 696 34 035 T2 ). Diverse Möglichkeiten sind für die bestromungs-basierte MRT-Instrumentenlokalisierung bekannt ( US 5,951,472 A ), meist über Differenzbildberechnung, vgl. die Druckschrift DE 199 58 408 A1 , und damit verbundener doppelter Messzeit. Eine weitere hier relevante Arbeit beschreibt eine spezielle Spin-Echo-Technik zur MRT-Messung von Strömen, jedoch nicht zum Zwecke der Instrumentenvisualisierung sondern zur Bestimmung von Stromverteilungen innerhalb eines mittels MRT darstellbaren leitfähigen Körpers („Magnetic Resonance Imaging”, 1989, Bd. 7, S. 89–94).In addition to passive visualization, active techniques are also described in the literature in which magnetic interference fields are generated in the vicinity of the instrument via electrical conductors ( DE 696 34 035 T2 ). Various possibilities are known for the current-based MRI instrument localization ( US 5,951,472 A ), mostly via differential image calculation, cf. the publication DE 199 58 408 A1 , and associated double measurement time. Another work relevant here describes a special spin-echo technique for the MRI measurement of currents, but not for the purpose of instrument visualization but for the determination of current distributions within an MRI-capable conductive body ("Magnetic Resonance Imaging", 1989, Bd , Pp. 89-94).

Der in den Patentansprüchen präzisierten Erfindung liegt das Problem zugrunde, dass bei Instrumentenvisualisierung über die magnetischen Eigenschaften des Materials (magnetische Suszeptibilität) die Grundfeldstörung kontinuierlich und in immer derselben Ausprägung vorhanden ist, d. h. die Größe der Artefakte nicht sequenzunabhängig steuerbar ist und die Störung auch zu Zeiten in der Sequenz vorhanden ist, zu denen die Ortskodierung erfolgt. Ferner sind insbesondere bei der sogenannten Spinecho-Bildgebungsmethode suszeptibilitätsbedingte Artefakte zu gering, um in dieser Technik eine sichere Visualisierung der Instrumente zuzulassen. Die Artefaktgröße hängt bei allen Bildgebungstechniken von der Grundfeldstärke ab.The specified in the claims invention is based on the problem that in instrument visualization on the magnetic properties of the material (magnetic susceptibility), the basic field disturbance is present continuously and in always the same expression, d. H. the size of the artifacts can not be controlled independently of the sequence and the disturbance is also present at times in the sequence to which the spatial coding takes place. Furthermore, especially in the so-called spin echo imaging method, susceptibility-related artifacts are too small to allow safe visualization of the instruments in this technique. Artifact size depends on the basic field strength for all imaging techniques.

Diese Probleme werden durch das Verfahren gemäß dem Patentanspruch 1 sowie durch die Vorrichtung gemäß dem Patentanspruch 3 gelöst.These problems are solved by the method according to the patent claim 1 as well as by the device according to the patent claim 3.

Die Verzerrung des Grundfeldes bei magnetisch neutralem Instrumentenmaterial über elektrischen Strom ermöglicht die Steuerung der Artefaktgröße über die Stromstärke. Messungen bei verschiedenen Stromstärken verbessern die Bestimmung der realen Instrumentenposition im Artefakt; eine Bestromung nur in Zeiten, in welchen kein Schichtselektions- und kein Lesegradient oder korrelierte Gradienten eingeschaltet sind, verhindert eine fehlerhafte Ortskodierung in der Nähe des Instruments. Die Artefaktgröße ist unabhängig von der Grundfeldstärke des Tomographen.Distortion of the fundamental field of magnetically neutral instrument material via electrical current allows the artifact size to be controlled by current intensity. Measurements at different current intensities improve the determination of the real instrument position in the artifact; current supply only in times in which no slice selection and no read gradient or correlated gradients are switched on prevents incorrect spatial coding in the vicinity of the instrument. The artifact size is independent of the basic field strength of the scanner.

In Sequenzen vom Spinechotyp können Auslöschungsartefakte erzeugt werden, wenn die Störung sequenz-getriggert beispielsweise nur vor bzw. nach dem Refokussierungspuls geschaltet wird. Das Spinecho-Phasenbild zeigt dann nur Phasenlinien um das Instrument herum, alle statischen Feldinhomogenitäten haben im Spinecho-Bild keinen Einfluss. Zusammen mit dem gleichzeitig aufgenommenen Magnitudenbild mit Darstellung der Anatomie ist so durch Überlagerung eine präzise Instrumentenlokalisation möglich.In spine-type sequences extinction artefacts can be generated if the disturbance is triggered in a sequence-triggered manner, for example, only before or after the refocussing pulse. The spin echo phase image then only shows phase lines around the instrument, all static field inhomogeneities have no effect in the spin echo image. Together with the simultaneously recorded magnitude image with representation of the anatomy, a precise instrument localization is thus possible by superposition.

Ein Ausführungsbeispiel für die temporäre Bestromung gemäß den Patentansprüchen 1 und 2 ist in 1 am Beispiel der Spinechosequenz gezeigt. Der Strom ist nur außerhalb der Zeiten eingeschaltet, in denen Bildgebungsgradienten eingeschaltet sind. Dadurch, dass der Visualisierungsstrom nur vor dem 180° Refokussierungspuls eingeschaltet wird, ergibt sich auch mit der Spinechosequenz ein Dephasierungsartefakt im Magnitudenbild sowie Phasenlinien um das Instrument im Phasenbild, wie diese von statischen Inhomogenitäten bei der Gradientenecho-Bildgebung bekannt sind.An embodiment of the temporary energization according to claims 1 and 2 is in 1 shown by the example of the spin echo sequence. The power is turned on only outside of times when imaging gradients are turned on. Because the visualization current is switched on only before the 180 ° refocussing pulse, the spin echo sequence also results in a dephasing artifact in the magnitude image as well as phase lines around the instrument in the phase image, as are known from static inhomogeneities in gradient echo imaging.

2 zeigt ein Ausführungsbeispiel für ein einfaches interventionelles Instrument, das einer Nadel wie sie z. B. für die Biopsienahme oder die lokale Gabe von Medikamenten verwendet wird. Die Nadel hat einen koaxialen Aufbau. Der Strom fließt z. B. auf dem Innenleiter zur Spitze. Durch eine elektrische Verbindung an dieser Stelle kann der Strom über das äußere Rohr zurückfließen. Durch diese asymmetrische Anordnung des Hin- und Rückleiters ergibt sich an der Oberfläche das gewünschte Störmagnetfeld zur Visualisierung der Nadel bei ihrem Einsatz am Magnetresonanztomographen. Ein geeignetes Material mit gewebeähnlicher magnetischer Suszeptibilität, welches auch geeignete mechanische Eigenschaften besitzt, ist beispielsweise Messing. 2 shows an embodiment of a simple interventional instrument that a needle such as z. B. is used for biopsy or the local administration of drugs. The needle has a coaxial construction. The current flows z. B. on the inner conductor to the top. By an electrical connection at this point, the flow can flow back through the outer tube. As a result of this asymmetrical arrangement of the forward and return conductors, the desired interference magnetic field for visualizing the needle when used on the magnetic resonance tomograph is obtained on the surface. A suitable material with tissue-like magnetic susceptibility, which also has suitable mechanical properties, is brass, for example.

3 zeigt als Ausführungsbeispiel die notwendige Anordnung für die sogenannte Radiofrequenzablation (RFA) von Tumoren. Hier ist denkbar, die bereits für die Applikation der Radiofrequenz vorhanden Anschlüsse an der Ablationsnadel zu nutzen, um mit der beschriebenen Technik die Nadel zu positionieren bzw. die Nadelposition nach Ablationsabschnitten zu kontrollieren. Es ist zu erwarten, dass die kleinen Visualisierungsströme auch über Gewebe geschickt werden können. Bei der RFA ist die beschriebene Bestromungstechnik von besonderem Vorteil. Ohne Strom kann die Anatomie trotz Gegenwart des Applikators ungestört abgebildet werden, bei MR-technischen Temperaturmessungen mittels der Protonenresonanzfrequenz(PRF)-Methode treten keine Störungen auf. Andererseits kann in Spincho-Bildern, die bezüglich der Darstellung der Anatomie oft von Vorteil sind, bei getriggert angelegtem Strom eine sehr gute ortstreue Nadelvisualisierung erfolgen. Ein Zusatzmodul, das beispielsweise im RF-Generator mit eingebaut werden kann, ermöglicht die Regelung des Visualisierungsstromes und leistet die Verarbeitung der vom MR-Tomographen gelieferten Triggersignale, wie sie in die Bildgebungssequenz mit einprogrammiert sind. Moderne Tomographen bieten solche sequenzgesteuerten Triggerausgänge bereits für andere Zwecke. 3 shows as an exemplary embodiment the necessary arrangement for the so-called radiofrequency ablation (RFA) of tumors. Here it is conceivable to use the connections on the ablation needle already present for the application of the radiofrequency, in order to position the needle with the described technique or to control the needle position after ablation sections. It is to be expected that the small visualization streams can also be sent via tissue. In the case of the RFA, the described current-carrying technique is of particular advantage. Without electricity, the anatomy can be imaged undisturbed despite the presence of the applicator, with MR technical temperature measurements by means of the Proton Resonance Frequency (PRF) method, no disturbances occur. On the other hand, in spincho images, which are often of advantage in terms of the representation of the anatomy, a very good localized needle visualization can take place in the case of triggered current. An additional module, which can be incorporated, for example, in the RF generator, allows the regulation of the visualization current and makes the processing of the MR-supplied trigger signals, as they are programmed into the imaging sequence. Modern tomographs already offer such sequence-controlled trigger outputs for other purposes.

Claims (3)

Verfahren zur Visualisierung eines oder mehrerer interventioneller Instrumente in der Magnetresonanzbildgebung über bildgebungssequenz-getriggerte zeitweise Instrumenten-Bestromung durch Visualisierungsstrom zur Erzeugung eines gewünschten Störmagnetfeldes zur Störung des magnetischen Grundfeldes des Magnetresonanztomographen, der auf vordefinierten Leiterstrukturen mittels Regelung eines anpassbaren Gleichstroms oder Gleichstromanteils des oder der mehreren Instrumente fließt, mit Auswertung der Magnituden- und Phasenbilder, dadurch gekennzeichnet, dass der Visualisierungsstrom für ein oder mehrere dieser Instrumente unabhängig von der gewählten Bildgebungstechnik der Magnetresonanz nur zu Zeiten geschaltet wird, in welchen keine bezüglich der Ortskodierung zur Ermittlung der Darstellung der Anatomie störungsanfälligen Bildgebungsgradienten geschaltet sind, und dass durch eine Überlagerung des so erhaltenen Instrumentenbildes als Phasenbild mit dem gleichzeitig aufgenommenen Magnitudenbild mit Darstellung der Anatomie eine präzise Instrumentenlokalisation ermöglicht ist.A method of visualizing one or more interventional instruments in magnetic resonance imaging via imaging sequence triggered temporal instrument energization by visualization current to produce a desired perturbing magnetic field perturbing the magnetic field of the magnetic resonance tomograph based on predefined conductor structures by controlling an adjustable DC or DC component of the one or more instruments flows, with evaluation of the magnitude and phase images, characterized in that the visualization current is switched for one or more of these instruments, regardless of the selected imaging technique of magnetic resonance only at times in which switched with respect to the spatial encoding for determining the representation of the anatomy failure prone Bildgebungsgradienten are, and that by a superposition of the thus obtained instrument image as a phase image with the same time recorded Magnitude image showing the anatomy enables precise instrument localization. Verfahren gemäß dem Anspruch 1, dadurch gekennzeichnet, dass speziell in Sequenzen vom Spinechotyp der Visualisierungsstrom zeitlich asymmetrisch bezüglich der Hochfrequenzpulse zur Spin-Refokussierung geschaltet wird, um in dieser Technik Signalauslöschungen und Phasenmuster aufgrund von Spindephasierung zu erzeugen.Method according to claim 1, characterized in that, especially in sequences of the spin echo type, the visualization current is temporally asymmetrically switched with respect to the radio-frequency pulses for spin refocusing in order to generate signal cancellations and phase patterns due to spindle phasing in this technique. Vorrichtung zur Durchführung des Verfahrens nach Anspruch 1 oder 2 mit einem Zusatzmodul zur sequenzgetriggerten und regelbaren Bestromung durch anpassbaren Gleichstrom oder Gleichstromanteil eines interventionellen Instruments.Apparatus for carrying out the method according to claim 1 or 2 with an additional module for the sequence-triggered and controllable energization by adjustable DC or DC component of an interventional instrument.
DE102012023124.5A 2012-11-27 2012-11-27 Method and device for visualizing interventional instruments in magnetic resonance imaging via sequence-triggered energization with evaluation of the magnitude and phase images Withdrawn - After Issue DE102012023124B4 (en)

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