Surgery – Truss – Pad
Patent
1990-12-21
1993-11-23
Smith, Ruth S.
Surgery
Truss
Pad
1286534, 128736, 324315, A61B 5055
Patent
active
052634825
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to improvements in and relating to magnetic resonance imaging (MRI) apparatus and methods, and in particular to a method and apparatus for the thermographic imaging of a subject, generally although not essentially a human or animal body, and to contrast agents and media for use in such methods.
In certain cancer treatments, malignant tissue within the body is destroyed by irradiation with radiation, for example microwave radiation, which has sufficient heating effect to kill the malignant tissue, e.g. by raising the local temperature to about 43.degree. C. As will readily be appreciated, the heating radiation can also kill healthy tissue and it is therefore of great importance for such treatments for the physician to be able to determine the temperature at and near the irradiated site.
This is particularly important since the radiation reflection and absorption characteristics are not uniform throughout the body and, especially where two or more directed radiation sources are used to achieve the heating effect, there is a danger that radiation reflection or shadowing by body tissue may cause areas of significant temperature increase ("hot-spots") to occur in healthy tissue or may prevent the temperature increase in part or all of the malignant tissue site from being sufficient to kill off all the malignant cells.
Several methods of temperature monitoring have been proposed, but to date all such methods have been either invasive, insufficiently accurate or time consuming or have enabled temperatures to be measured for superficial tissue layers only. Thus typical techniques which have been used include invasive monitoring by insertion of thermal sensing probes, infrared thermography, CAT scanning and NMR relaxation rate assessments.
There remains a need for a non-invasive thermographic imaging method capable of determining local temperatures throughout the body with reasonable accuracy.
We have now found that using a modification of our recently developed Electron Spin Resonance Enhanced Magnetic Resonance Imaging (ESREMRI) method thermographic imaging, or temperature monitoring, can be effected.
MRI is a diagnostic technique that has become particularly attractive to physicians as it does not involve exposing the patient to the harmful X-or gamma-radiations of conventional radiographic imaging techniques.
In our co-pending European Patent Application EP-A-296833 and British Patent Applications Nos. 8817137 and 8819753.8 we have described how the intensity of the magnetic resonance (MR) signal from which MR images are built up may be enhanced, e.g. by factors of 100 or more, by exciting an esr transition of a paramagnetic substance present within the subject being imaged where that esr transition is coupled to the nmr transition of the nuclei (generally protons and usually protons in water molecules) which emit the MR signals from which the MR images are built up.
The degeneracy of the spin states of nuclei with non-zero spin, e.g. .sup.1 H, .sup.13 C, .sup.19 F, etc., is lost when such nuclei are within a magnetic field and transitions between the ground and excited spin states can be excited by the application of radiation of the frequency (.omega..sub.o) corresponding to energy difference E of the transition (i.e. .omega..sub.o = E). This frequency is termed the Larmor frequency and is proportional to the strength of the applied field. As there is an energy difference between the spin states, when the spin system is at equilibrium the population distribution between ground and excited spin states is a Boltzmann distribution and there is a relative overpopulation of the ground state resulting in the spin system as a whole possessing a net magnetic moment in the field direction. This is referred to as a longitudinal magnetization. At equilibrium the components of the magnetic moments of the individual non-zero spin nuclei in the plane perpendicular to the field direction are randomized and the spin system as a whole has no net magnetic moment in thi
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Nycomed Innovation AB
Smith Ruth S.
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