DE3934919A1 - Frame for testing or examining object esp. for cerebral surgery - has some sections arranged later as reference surfaces for detection by NMR - Google Patents

Abstract

The reference surfaces of the frame contain a substance with NMR active nuclei, and these active nuclei are subjected to an interaction with a substance, a relaxant, which effects the amplification of the NMR signal by dynamic nuclear polarisation (DNP), if the electro-spin-system of these substances is saturated by external energy, namely saturated energy. The NMR signal, which the reference surface emits, is amplified by dynamic core polarisation (DNP). The frame (F) for dealing with the patient (P) is supplied with a current source (MC) which with the magnets (M) produces a magnetic field (Bo). Gradient coils (GC) are provided for the prodn. of a gradient field. Also included is a NMR spectrometer (NMRS) and a radio frequency transmitter (ESRE). USE/ADVANTAGE - Testing and examination of object e.g. patient usiong NMR method. Gives higher positioning accuracy and reduces necessary reprodn. time, improved signal strength.

Description

The invention relates to a framework for testing or examination of an object, for example for the Monitoring of operations within a counter a human body and by means of external coordination points and the magnetic resonance imaging.

The test frame quantity stell according to the invention is used to a higher posi to achieve tional accuracy and the necessary shorten the display time.

A so-called stereotactic framework is used for the Monitoring of cerebral surgical operations winds on the basis of X-rays, the Computerto mography and horizontal x-rays and magneti image representation. The idea is that To map a patient's skull to a frame that Has reference points that in the above-mentioned image lungs are visible. These reference points can be used for the localization of volumes in an object by using the representations.  

Magnetic resonance imaging (MRI) is a technique that uses the nuclear magnetic resonance phenomenon to determine the core density of an object, and the NMR characteristics are related to a core or the local distribution of physical and chemical characteristics that these cause. These NMR characteristics include, for example: longitudinal relaxation (characterized by the longitudinal relaxation time T 1 ), transverse relaxation (characterized by the transverse relaxation time T 2 ), relaxation in the rotating reference frame (characterized by the relaxation time T 1 rho), chemical displacement and Coupling factors between the cores. The NMR characteristics are caused by the physico-chemical environment of a core: polarizing magnetic field B _o , the flow rate, the diffusion, through paramagnetic materials, ferromagnetic materials, the viscosity and the temperature.

The methods and applications of magnetic resonance and magnetic resonance imaging are shown in a number of studies have been treated:  

Poole CP and Farach HA: Theory of magnetic resonance, John Wiley, New York 1987, Stark DD and Bradley WG: Magnetic resonance imaging, C.V. Mosby Comp., St. Louis 1988, Gadian DG: Nuclear magnetic right sonance and its applications to living systems, Oxford Univ. Press, London 1982, Shaw D: Fourier transform NMR spectroscopy, Elsevier, Amsterdam 1984, Batocletti JH: NMR proton imaging, CRC Crit. Rev. Biomed. Closely. vol. 11, pp. 313-356, 1984, Mansfield P and Morris PG: NMR imaging in biomedicine, adv. In magnetic resonance, Academic Press, New York 1982, Abragam A: The principles of nuclear magnetism, Clarendon Press, Oxford 1961, Fukushima E and Roeder SBW: Experimental Pulse NMR, Addison-Wesley, Readin, Massachusetts 1981, Lasker SE and Milvy P (eds.): Electron spin resonance and nuclear magnetic resonance in biology and medicine and magnetic resonance in biological systems, Annals of New York Academy of Sciences vol. 222, New York Academy of Sciences 1973, Sepponen SE: Discrimination and charac terization of biological tissues with magnetic resonance imaging; A study of methods for T1, T2, T1rho and chemi cal shift imaging, Acta polytechnica scandinavica EL-56, Helsinki 1986, Fukushima E and Roeder SB: Experimental pulse NMR, Addison-Wesley, London 1981, Anderson WA et al: US Pat. 34 75 680, Ernst RR: 35 01 691, Tomlinson BL et al: US Pat. 40 34 191, Ernst RR: US Pat. 38 73 909, Ernst RR: US Pat. 40 70 611, Bertrand RD et al: U.S. Pat. 43 45 207, Young IR: U.S. Pat. 45 63 647, Hofer DC et al: US Pat. 41 10 681, Savelainen MK: Magnetic reso nance imaging at 0.02 T: Design and evaluation of radio frequency coils with wave winding, Acta Polytechnica Scandinavia Ph 158, Helsinki 1988, Sepponen RE: US Pat. 47 43 650, Sepponen RE: US Pat. 46 54 595, Savelainen MK: US Pat. 47 12 068, Sepponen RE: US Pat. 45 87 493, Savelainen MK: US Pat. 46 44 281 and Kupiainen J: US Pat. 46 68 904.  

In addition, there are studies regarding a "dynamic nuclear polarization "(DNP) with the following publications before:

Lepley AR and Closs GL: Chemically induced magnetic po larization, Wiley, New York 1973, Potenza J: Measure ment and applications of dynamic nuclear polarization, Adv. Mol. Relaxation Processes vol. 4, Elsevier, Am sterdam 1972, pp. 229-354.

The "DNP" is a magnetic dop pel resonance method, which is accordingly two separate spin pay or spins required. Such spins include for example the spin of electrons and protons. At a Double resonance method is the distribution of a spin number changed at different energy levels and the other spin number is kept under observation. When certain conditions are met, the Re grows sonar signal of the observed spin number (so-called Overhaus phenomenon). The amplified signal can be Am plitude that is several times greater than the un strengthened signal. The gain factor can be positive or be negative. The amplified signal is in its Characteristics highly sensitive to the physico  chemical properties and reactions on a spin environment so that its application for the Testing the chemical properties of a material is obvious.

The release of Maciel-GE, Davis MP:

The reference Maciel GE, Davis MP: imaging of para magnetic centers in solids via dynamic nuclear polari zation, J. Magn. Reson., vol. 64, pp. 356-360, 1985 discloses a method that paramag for mapping netic components through the combination the DNP and MRI procedure is suitable. The published of Ettinger KV: US Pat. 47 19 425 explained the use case of displaying the content of pa ramagnetic components and the activity of zere bral nerve cells.

The publications of Lurie DJ, Bussel DM, Bell LH, Mallard JR:

Proton Electron Double Resonance Imaging: A new method for imaging free radials, Proc. S. M. R. M. Fith Annual Meeting, 1987, New York, p. 24 and Lurie DJ, Bussel DM, Bell LH, Mallard JR: Proton-Electron Doule Magnetic Imaging of free radial solutions, J. Magn. Reson., Vol.  76, 1988, pp. 366-370 describe the representation of free radical groups, Nitric oxide radicals and the degree of oxidation as possible Applications.

According to the prior art, the electron spin system is saturated by irradiating the object at a frequency that corresponds to the electron spin resonance or ESR frequency in the field B _o and by detecting the NMR signal at a frequency that corresponds to the field strength B _o . For example, the corresponding frequencies for B _o strength of 0.04 T are an ESP frequency of 1.12 GHz and an NMR frequency of 1.7 MHz. Methods are known which are suitable for the so-called high-speed magnet display and are explained, for example, in the following publications:

Rzedzian RR et al: Lancet, December 3, p. 1281, 1983, Haase A et al: J. Magn. Reson. vol. 67, p. 258, 1986, Pykett IL et al: Magn. Reson. in Med., vol. 5, p. 563. 1987.

It is known to use frames that are relative to Ana tomie of a patient are pinned to a coordina to generate the position axis. Parts of this frame are provided with a material to represent in the picture  position to provide reference points. Known products of this type are contained in the Leksell Stereotactic In strument, manufactured by Elekta Instrument AB, floor holm, Sweden and Orfit Rycast thermoplastic used For example, in actinotherapy for positioning egg patient who manufactured the latter device is operated by Luxilon Industries & Co. Antwerp, Belgium.

The use of such so-called stereotactic ver driving is described in:

Leksell et al: Stereotaxis and nuclear magnetic reso nance, J Neurology, Neurosurgery and Psychiatry, vol. 48, pp. 14-18, 1985, Lehmann and Hill: Computed-tomo graphy-directid stereotaxis for movement disorder with postoperative magnetic resonance imaging confirmation, Appl. Neurophysiol., Vol. 51: pp. 21-28, 1988, Kelly et al: Evolution of contemporary instrumentation for com computer assisted stereotactic surgery Surg. Neurol., Vol. 27, Fasc 3, 269-274, 1988.

One problem with the prior art is weak Signal to noise ratio in MRI: the sections of a Frames, visible with MRI, must have a sufficient Vo lumen of a material detectable by MRI  sen (the volume of different image voxels), and the Presentation time must be long.

The objects of the invention are explained in detail by the Features solved according to claim 1 and how they further in Subclaim are included.

The invention is described in more detail below with reference to graphic representation explained in more detail. It shows

FIG. 1 shows the frame according to the invention;

Fig. 2 shows in detail the way of realizing reference surfaces of a frame to be detected with the magnetic resonance image display and

Fig. 3 shows the pulse sequences of a suitable presen- tation method for the representation of the reference surfaces and the object.

FIG. 1 is a patient or another to check the object P, and further a associated therewith frame F in a polarized magnetic field B _o PLA sheet that is generated by a magnet M which is supplied from a power source MC with energy. The magnetic field causes a nuclear magnetization in the object and a magnetization that is generated by electron spin. The object P and the frame F are also surrounded by gradient coils GC for generating a gradient field, the strength of which is controlled by an NMR spectrometer NMRS through the gradient current source G , NMRS also controlling a radio frequency transmitter ESRE which generates the energy (saturation energy ), which saturates the material that is in the reference surfaces of frame F and which emits the NMR signal and also saturates the relaxant electro-spin system. The NMRS is equipped with the necessary radio frequency components, namely for procedures that are necessary for the generation and reception of the NMR signals via an antenna A and also for the storage and processing of the signal, the resultant image on a display D will be shown.

The NMR test arrangement comprises a magnet (a resistive, permanent or superconducting magnet, so even an earth magnetic field is sometimes possible), an NMR spectrometer and also an antenna which is necessary for the generation of a polarizing magnetic field B _o .

In addition to the above, the magnetic display includes Development arrangement further gradient coils (in so-called Rotational frame test matography are some of the Gra served in an NMR frequency excitation field) and also controllable power sources and elements for the Re construction and the representation of the image.

Fig. 2 illustrates in detail how the reference surfaces are provided. Fig. 2a illustrates a "spot-like" cylindrical space VP , formed from a reference surface and saturation supply by a coaxial cable. Fig. 2b illustrates a narrow and long reference surface, which comprises two conductors for the passage of the electron spin system saturation energy.

Fig. 3 shows a display method, based on a three-dimensional FOURIER display technology, for recording a position or location with elements of the magnetic display in such a way that the first step consists in the saturation of the electron spin system of a reference surface, with Help of the ESR frequency electromagnetic energy, guided by a surgical instrument BN (not shown). The second step consists in exciting the nuclear spin system of a reference surface with the NMR frequency electromagnetic radiation. The third step consists in the phase encoding of the nuclear spin system with pulses directed in the X and Y directions, the time of which is marked on the axes G _z and G _y . The fourth step comprises the collection of the NMR signal SE , while the gradient directed in the X direction is switched on and the switching time of this gradient is marked on the G _x axis. The sequence is repeated as many times as necessary by phase encoding operations, and the necessary averages and the final magnetic image are built up from the resulting bundle of signals.

The advantages that can be achieved according to the invention in the localization of reference areas of a frame become recognizable if one compares a signal obtained, for example, from a water sample with a signal obtained by MRI, which was activated using conventional MRI and DNP methods. The amplified signal can be several hundred times stronger than an obtainable signal without amplification. In other words, if the gain is two hundred times, a sample of 1 mm ³ emits a signal vigorously in the same way as a sample of 200 mm ³ . The reduction in display time that can be achieved is even more dramatic: an amplified pattern can be localized forty thousand times faster with the same signal-to-noise ratio than an unamplified pattern.

As an activating agent or relaxation agent it is possible, for example. nitrogen radicals or paramagneti to use ions. In addition to the above The most recent publications have examined this in:

The applicable technology for generation and transfer is the ESR frequency electromagnetic energy described by:

Bates RD: Polarization of solvent nuclei by nitroxide Spin Labels al Low Magnetic Fields, J. Magn. Reson., vol. 48, pp. 111-124, 1982.

The applicable technology for generation and over wearing the "ESR frequency electromagnetic energy; ist described in:

Field et al: Physics and technology of hyperthermia, Martinus Nÿhof Publishers, Dordrecht, The Netherlands, 1987.  

The described frame according to the invention and its Lo Calibration technology can, for example, in connection with egg a surgical instrument according to the Finnish patent message 8 85 210 can be used.

The invention is not limited to the above leadership forms, but also other embodiments are conceivable. Of course everyone can target for NMR tests can be suitable core, such as the core of NMR active isotopes of hydrogen, phosphorus, fluorocarbon lenstoff and nitrogen. In addition to medical The invention can also be used in applications for the inspection of animals, food and Solids.

Claims (2)

1. Framework for the examination or examination of a Ge object, in particular examination framework for cerebral surgery and tumor treatment, characterized in that some sections of the frame, subsequent reference surfaces for detection by NMR methods, such as magnetic resonance imaging are set up in such a way that the reference surface contains a substance with NMR-active nuclei and that these active nuclei are subjected to an interaction with a substance, a relaxant, which causes the amplification of the NMR signal by dynamic nuclear polarization (DNP), if that Electro-spin system of these substances is saturated by external energy, ie saturation energy. 2. Procedure for the localization of the reference surface of the examination frame by magnetic resonance nanz image display, characterized, that the NMR signal that emits the reference surface through dynamic nuclear polarization (DNP) is reinforced.