Systems and Methods for Reducing RF Power or Adjusting Flip Angles During an MRI for Patients with Implantable Medical Devices
First Claim
1. A method for use in controlling magnetic resonance imaging (MRI) systems for imaging the tissues of patients with implantable medical devices, the method comprising:
- determining a scaling factor for scaling the power levels (PRF) of radio-frequency (RF) fields of MRI systems for use with patients with implantable devices, wherein the scaling factor is based on specific absorption rate (SAR) values for patients with implantable devices and SAR values for patients without implantable devices;
for patients with implantable devices, reducing the power level (PRF) of the RF fields to be used based on the scaling factor; and
imaging the tissues of the patient using the MRI system at the reduced power level (PRF).
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Abstract
Techniques are provided for controlling magnetic resonance imaging (MRI) systems for imaging patients having implantable medical devices. In one example, a scaling factor is determined based on maximum local specific absorption rate (SAR) values for patients with implants and for patients without implants. The MRI determines the radio-frequency (RF) power and flip angle sequences to be used for a given patient, without regard to the presence of an implanted device. However, for patients with implanted devices, the MRI reduces its RF power or adjusts its flip angle sequences based on the scaling factor so as to ensure that the local SAR within the patient does not exceed acceptable levels. In other examples, rather than reducing the RF power of the MRI or adjusting the flip angles, blankets or pads formed of RF power attenuating materials, such as dielectrics, are positioned around the patient near the implantable device, to reduce the RF power incident tissues adjacent the device.
31 Citations
20 Claims
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1. A method for use in controlling magnetic resonance imaging (MRI) systems for imaging the tissues of patients with implantable medical devices, the method comprising:
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determining a scaling factor for scaling the power levels (PRF) of radio-frequency (RF) fields of MRI systems for use with patients with implantable devices, wherein the scaling factor is based on specific absorption rate (SAR) values for patients with implantable devices and SAR values for patients without implantable devices; for patients with implantable devices, reducing the power level (PRF) of the RF fields to be used based on the scaling factor; and imaging the tissues of the patient using the MRI system at the reduced power level (PRF). - View Dependent Claims (2, 3, 4)
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5. A method for use in controlling magnetic resonance imaging (MRI) systems for imaging the tissues of patients with implantable medical devices, the method comprising:
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determining a scaling factor for adjusting flip angles of magnetic fields of MRI systems for use with patients with implantable devices, wherein the scaling factor is based on specific absorption rate (SAR) values for patients with implantable devices and SAR values for patients without implantable devices; for patients with an implantable device, adjusting flip angles to be used based on the scaling factor; and imaging the tissues of the patient using the MRI system at the adjusted flip angles.
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6. A method for use by a magnetic resonance imaging (MRI) system for imaging the tissues of a patient with an implantable medical device, the method comprising:
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determining a power level for the radio-frequency (RF) fields of the MRI system for use in imaging the patient, without regard to the presence of the implantable medical device within the patient; inputting a value representative of a ratio of a local specific absorption rate (SAR) value for patients without implantable devices to a local SAR value for patients with implantable devices; scaling the power level of the RF fields of the MRI system based on the ratio; and imaging the tissues of the patient using the MRI system at the scaled power level. - View Dependent Claims (7, 8)
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9. A method for use by a magnetic resonance imaging (MRI) system for imaging the tissues of a patient with an implantable medical device, the method comprising:
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determining a flip angle for the magnetic fields of the MRI system for use in imaging the patient, without regard to the presence of the implantable medical device within the patient; inputting a value representative of a ratio of a local specific absorption rate (SAR) value for patients without implantable devices to a local SAR value for patients with implantable devices; adjusting the flip angle of the magnetic fields of the MRI system based on the ratio; and imaging the tissues of the patient using the MRI system using the adjusted flip angle.
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10. A method for use by an implantable medical device implanted within a patient, the method comprising:
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storing values in the device relevant to the maximum specific absorption rate (SAR) of the patient; and transmitting the values to an external system prior to a magnetic resonance imaging (MRI) procedure such that an MRI system performing the procedure can adjust its operation based, at least in part, on the transmitted values. - View Dependent Claims (11, 12, 13)
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14. A method for use with a magnetic resonance imaging (MRI) system for imaging the tissues of a patient having an implantable medical device, the method comprising:
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selecting an radio-frequency (RF) power attenuating material for placing adjacent the patient during an MRI procedure to reduce the strength of RF fields generated within tissues of the patient by the MRI system; and imaging the tissues of the patient using the MRI system while the material is positioned adjacent the patient. - View Dependent Claims (15, 16, 17)
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18. An article for use with a magnetic resonance imaging (MRI) system for imaging the tissues of a patient with an implantable medical device, the article comprising:
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a radio-frequency (RF) power attenuation material fitted to be placed adjacent the patient during an MRI procedure to reduce the strength of fields applied to the tissues of the patient by the MRI system; wherein the material is formed from one or more of a conductive material, a resistive material and a dielectric material. - View Dependent Claims (19, 20)
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Specification