Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Reexamination Certificate
1997-11-10
2001-11-20
Arana, Louis (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
C600S421000
Reexamination Certificate
active
06320379
ABSTRACT:
BACKGROUND
This invention relates to nuclear magnetic resonance (NMR) apparatus.
Inserted (or implanted) NMR coils can be sited in many cases close to a lesion which it is proposed to treat by the application of an external therapy remotely targeted at the lesion. Many therapies of interventional magnetic resonance imaging (MRI) are thermal in nature, and involve energies which are intentionally destructive of tissue locally. Such therapies include r.f. hyperthermia, laser ablation and focussed ultrasound. These therapies depend on assumptions about tissue properties in assessing their exact energy profiles, and the location of the focus, or principal region of heat deposition. Because of uncertainties in in vivo temperature measurement, pilot energy depositions are not a satisfactory method of determining energy patterns in human subjects. It is possible to estimate spot location from external data but, short of heating up a region to see where it is, it is difficult to be sure it is where it was intended to be. Reflection, refraction and scattering can affect its location significantly. Heating hot enough to be seen reliably with MRI means that tissue is damaged, so that if there were an error in location, normal tissue might be unintentionally destroyed.
It has been proposed (EP-A-0 558 029) to provide a probe containing an MR coil with temperature and intensity sensors on the outside of a bulb which can be blown up around the probe to rest against the tissue outside. Then the maximum values of the temperature and intensity measured during ultrasonic wave treatment are compared with values calculated for the treatment, with a view to minimising the differences. However, the temperature and intensity sensors will measure the temperature and intensity adjacent them, but this is only indicative of the temperature and intensity at the intended focus of heat deposition, because temperature and intensity gradients are large and variable.
SUMMARY
The present invention provides suitable transducers are located in the body of the inserted or implanted NMR receiver coil which is being used to monitor the therapy, thus alleviating the aforementioned problem.
The invention also provides a probe for use with magnetic resonance imaging apparatus, which is designed to be inserted into and removed from a patient and which comprises a former upon which an r.f. coil is mounted is wherein the former also carries at least one transducer or sensor by which the targeting of energy relating to an interventional procedure to an area in the vicinity of the transducer may be controlled both as to position and strength.
The method suggested here is particularly relevant to r.f. hyperthermia and focussed ultrasound. In both of these the exact distribution of energy inside the relevant tissue is important but hard to determine.
The invention also provides a method of calibrating an externally generated beam of energy to be used in an interventional procedure on a patient, comprising the steps of inserting into the patient a probe comprising a former and an r.f. coil mounted on the former for use with magnetic resonance imaging apparatus, steering the beam at low power to at least one transducer or sensor in the probe, and comparing the actual location of the transducer derived from the magnetic resonance imaging apparatus with the indicated location derived from control apparatus for the externally generated beam of energy.
The targeting of energy in the treatment itself will then be improved.
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Arana Louis
Fay Sharpe Fagan Minnich & McKee
Picker International Inc.
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