Method of producing personalized RF coil array for MR imaging guided interventions

Abstract

A method of manufacturing a personalized radio frequency (RF) coil array for magnetic resonance (MR) imaging guided interventions includes: acquiring diagnostic image data reflecting the anatomy of a portion of a patient's body; planning an intervention on the basis of the diagnostic image data, wherein a field of the intervention within the patient's body portion is determined; and arranging one or more RF coils on a substrate which is adapted to the patient's anatomy, in such a manner that the signal-to-noise ratio of MR signal acquisition via the one or more RF coils from the field of the intervention is optimized.

Claims

1. A method of producing a personalized array of one or more radio frequency (RF) coils for a magnetic resonance (MR) imaging guided surgical procedure on a portion of a patient's body, the method comprising: creating a model of anatomy of the portion of a patient's body using acquired image data from at least one of X-ray, computed tomography (CT), and MR diagnostic images of the portion of a patient's body; determining, based on the acquired image data, an interventional area within the portion of the patient's body and an access path to the interventional area, the access path limiting access strategies during the surgical procedure; and providing an arrangement of a substrate by disposing the array of one or more RF coils on the substrate wherein; sizes, shapes and positions of the one or more RF coils are computed based on the acquired image data for optimal signal-to-noise ratio of an MR signal acquired from the determined access path and the interventional area, and; a shape of the substrate is adapted to a shape of the portion of the patient's body based on the acquired image data so as to position the array of RF coils firmly in close proximity on the portion of the patient's body during the surgical procedure.

2. The method of claim 1, further comprising providing the substrate with one or more apertures to keep the access path clear when the substrate is attached to the patient's body during the surgical procedure.

3. The method of claim 1, wherein the RF coils are arranged on the substrate at a pre-determined minimum distance from the interventional area.

4. The method of claim 1, wherein at least one of the sizes, shapes, and positions on the substrate of the one or more RF coils on the substrate are computed based on a simulation of the RF electromagnetic field distribution during MR signal acquisition.

5. The method of claim 1 further comprising using rapid prototyping for forming the array of one or more RF coils.

6. The method of claim 1, further comprising arranging on the substrate electronic components for at least one of RF signal transmission and RF signal reception via the RF coils.

7. The method of claim 1, wherein the array of RF coils include one or more standardized RF coil modules.

8. The method of claim 1, wherein providing the arrangement of the substrate and the array of one or more RF coils disposed on the substrate includes providing a mask with the array of one or more RF coils disposed on the mask.

9. The method of claim 8, wherein providing the mask includes providing apertures therein for the patient's eyes, nose and mouth.

10. The method of claim 8, further comprising providing the mask with at least one aperture for providing surgical access to the patient's skull and brain.

11. The method of claim 1, wherein the RF coils are arranged on the substrate at a pre-determined minimum distance from the access path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The enclosed drawings disclose preferred embodiments of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention. In the drawings:

(2) FIG. 1 schematically shows a MR device including a personalized RF coil array according to the invention;

(3) FIG. 2 shows the RF coil array of FIG. 1 in more detail;

(4) FIG. 3 shows another embodiment of the personalized RF coil array according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) With reference to FIG. 1, a MR device 1 is shown. The device comprises superconducting or resistive main magnet coils 2 such that a substantially uniform, temporally constant main magnetic field B.sub.0 is created along a z-axis through an examination volume. The device further comprises a set of (1.sup.st, 2.sup.nd, andwhere applicable3.sup.rd order) shimming coils 2, wherein the current flow through the individual shimming coils of the set 2 is controllable for the purpose of minimizing B.sub.0 deviations within the examination volume.

(6) A magnetic resonance generation and manipulation system applies a series of RF pulses and switched magnetic field gradients to invert or excite nuclear magnetic spins, induce magnetic resonance, refocus magnetic resonance, manipulate magnetic resonance, spatially and otherwise encode the magnetic resonance, saturate spins, and the like to perform MR imaging.

(7) Most specifically, a gradient pulse amplifier 3 applies current pulses to selected ones of whole-body gradient coils 4, 5 and 6 along x, y and z-axes of the examination volume. A digital RF frequency transmitter 7 transmits RF pulses or pulse packets, via a send-/receive switch 8, to a -body RF coil 9 to transmit RF pulses into the examination volume. A typical MR imaging sequence is composed of a packet of RF pulse segments of short duration which taken together with each other and any applied magnetic field gradients achieve a selected manipulation of nuclear magnetic resonance. The RF pulses are used to saturate, excite resonance, invert magnetization, refocus resonance, or manipulate resonance and select a portion of a body 10 positioned in the examination volume. The MR signals are also picked up by the body RF coil 9.

(8) For intra-operative generation of MR images of the head region of the body 10, for example by means of parallel imaging, a set of local array RF antennae (coils) 11, 12, 13 are placed on a mask 19, which constitutes a substrate adapted to the patient's head anatomy within the meaning of the invention. The RF coils 11, 12, 13 are positioned contiguous to the head region selected for imaging. Hence, high-quality MR images can be acquired, for example, during brain surgery. The array coils 11, 12, 13 can be used to receive MR signals induced by body-coil RF transmissions.

(9) The resultant MR signals are picked up by the body RF coil 9 and/or by the array RF coils 11, 12, 13 and demodulated by a receiver 14, preferably including a pre-amplifier (not shown). The receiver 14 is connected to the RF coils 9, 11, 12 and 13 via send-/receive switch 8.

(10) A host computer 15 controls the current flow through the shimming coils 2 as well as the gradient pulse amplifier 3 and the transmitter 7 to generate any of a plurality of MR imaging sequences, such as echo planar imaging (EPI), echo volume imaging, gradient and spin echo imaging, fast spin echo imaging, and the like. For the selected sequence, the receiver 14 receives a single or a plurality of MR data lines in rapid succession following each RF excitation pulse. A data acquisition system 16 performs analog-to-digital conversion of the received signals and converts each MR data line to a digital format suitable for further processing. In modern MR devices the data acquisition system 16 is a separate computer which is specialized in acquisition of raw image data.

(11) Ultimately, the digital raw image data is reconstructed into an image representation by a reconstruction processor 17 which applies a Fourier transform or other appropriate reconstruction algorithms, such like SENSE or GRAPPA. The MR image may represent a planar slice through the patient, an array of parallel planar slices, a three-dimensional volume, or the like. The image is then stored in an image memory where it may be accessed for converting slices, projections, or other portions of the image representation into appropriate format for visualization, for example via a video monitor 18 which provides a human-readable display of the resultant MR image.

(12) FIG. 2 shows the personalized RF coil array of the invention in more detail. As can be seen in FIG. 2, the substrate 19 is a mask (fabricated, for example, from a suitable plastic material) which is adapted to the shape of the patient's head. The mask 19 comprises apertures for the patient's eyes, mouth and nose. RF coils 11, 12, 13 are arranged on the mask 19 in such a manner that the signal-to-noise ratio of MR signals acquired via the RF coils 11, 12, 13 from an interventional field within the patient's brain is optimized. The personalized RF coil array shown in FIG. 2 further comprises an aperture at the planned site for craniotomy to allow the surgeon to access the skull and brain. The corresponding access path is indicated by arrow 20 in FIG. 2. The personalized RF coil array is designed and manufactured in an automated fashion by means of rapid prototyping. Therein, the sizes, shapes, and positions of the RF coils 11, 12, and 13 are computed by means of simulation of electromagnetic field distributions in order to optimize the signal-to-noise ratio taking into account the interventional field and access path resulting from the planning of the intervention. The necessary apertures of the mask 19 are used as constraints in the optimization procedure.

(13) FIG. 3 illustrates an embodiment of the invention, in which standardized and interconnectible RF coil modules are used. The coil modules 21 are arranged on the mask 19 in accordance with the above-described optimization criteria. The interconnected RF coil modules 21 are connected via cable connections to a RF unit 22 comprising, for example, a RF pre-amplifier.