Operating an MR System and an MR System

Abstract

A method is used to operate an MR system having at least one MR body coil and a control device connected to the at least one MR body coil. At least one radiometer is used to measure a body temperature of a body region, which body region can be illuminated by the respective radiometer, of a patient to be examined by the MR system. The measured body temperature is compared with a limit temperature, and an MR transmit power directed at the patient is brought closer to the limit temperature on the basis of a result of the comparison. The radiometer operates, in particular, in a frequency band that differs from the MR band. An MR body coil for performing the method has at least one radiometer antenna and an amplifier connected downstream of the radiometer antenna. The MR body coil can also have an input blocking filter connected downstream of the radiometer antenna and designed to block the MR band.

Claims

1. A method for operating an MR system comprising at least one MR body coil and a control device connected to the at least one MR body coil, the method comprising: measuring, by at least one radiometer, at least one body temperature of a body region, which body region can be illuminated by the respective radiometer, of a patient to be examined by the MR system, comparing the measured body temperature with a limit temperature, and bringing an MR transmit power directed at the patient closer to the limit temperature on the basis of a result of the comparison.

2. The method as claimed in claim 1, wherein the radiometer is a Dicke radiometer comprising a radiometer antenna, a noise source and a Dicke switch, and the Dicke switch is switched over alternately between the radiometer antenna and the noise source.

3. The method as claimed in claim 2, wherein the Dicke switch is connected to the noise source during transmit phases of the MR system and is connected to the radiometer antenna during non-transmit phases of the MR system.

4. The method as claimed in claim 2, wherein the Dicke switch is switched over during transmit phases of the MR system, such that the Dicke switch is connected alternately to the radiometer antenna and the noise source during non-transmit phases of the MR system.

5. The method as claimed in claim 1, wherein a useful band of the radiometer lies outside an MR band.

6. The method as claimed in claim 1, wherein the radiometer has a low-noise amplifier and at least one measured signal measured by the radiometer antenna and then amplified by the amplifier is supplied to and is evaluated by the control device.

7. The method as claimed in claim 6, wherein the noise signal supplied to the control device has its original frequency.

8. The method as claimed in claim 6, wherein the noise signal supplied to the control device has a down-converted frequency.

9. The method as claimed in claim 1, wherein the measured body temperature is displayed at a user interface of the MR system.

10. The method as claimed in claim 1, wherein measuring by the radiometer comprises measuring by a plurality of radiometers for respectively different body regions that can be illuminated a plurality of body temperatures at different depths of the patient to be examined.

11. The method of claim 5, wherein the useful band is above the MR band with a frequency interval of at least 5 MHz.

12. The method of claim 2, wherein the radiometer has a low-noise amplifier and at least one measured signal measured by the radiometer antenna and then amplified by the amplifier is supplied to and is evaluated by the control device.

13. The method as claimed in claim 6, wherein measuring by the radiometer comprises measuring by a plurality of radiometers for respectively different body regions that can be illuminated a plurality of body temperatures at different depths of the patient to be examined.

14. An MR body coil comprising: an MR antenna; at least one radiometer antenna, and an amplifier connected downstream of the radiometer antenna.

15. The MR body coil as claimed in claim 14, further comprising an input blocking filter connected downstream of the radiometer antenna and is designed to block the MR band.

16. The MR body coil as claimed in claim 14, wherein a housing wall of the MR body coil and/or a cushion for supporting the patient, situated between the radiometer antenna and the patient is impedance-matched.

17. The MR body coil as claimed in claim 14, wherein the MR body coil is a head coil, a head/neck coil, a spine coil and/or an abdomen coil.

18. An MR system comprising: at least one MR body coil comprising at least one radiometer antenna, and an amplifier connected downstream of the radiometer antenna; a control device (connected to the at least one MR body coil, the control device configured to compare a measured body temperature from the amplifier with a limit temperature, and bring an MR transmit power closer to the limit temperature on the basis of a result of the comparison.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The properties, features and advantages of this invention as described above and the manner in which these are achieved become clearer and easier to understand in the context of the following schematic description of exemplary embodiments which are explained in greater detail with reference to the drawings. For the sake of clarity, identical or functionally identical elements may be denoted by the same reference signs in this case.

[0042] FIG. 1 shows an MR system with a radiometer antenna according to one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] FIG. 1 shows, in a sectional view from the head side, an outline of an MR system including an MR body coil 1, an MR scanner 2 and a control device 3 connected to the MR scanner 2 and the MR body coil 1. The MR scanner 2 is in particular a high-field scanner whose Bo field strength is at least 1.5 T, e.g. 1.5 T, 3 T, 7 T, 10 T, etc. The MR frequency band of the MR scanner 2 lies in the region of 42.4 MHz/T. As usual, the MR scanner 2 is equipped with MR transmit antennas (not shown) in order to transmit MR pulses at frequencies in the MR band during an MR scan, e.g., in the context of echo trains. The MR response signals of a patient P are picked up by MR receive antennas (not shown) of the MR body coil 1. The activation of the MR scanner 2, the evaluation of the signals picked up by the MR receive antennas, and imaging are performed by the control device 3 in a manner which is generally known.

[0044] The MR body coil 1 is designed here by way of example as a head coil for examining a head region of the patient P. The head of the patient P rests on top of a cushion 4 on a housing wall 5 of the MR body coil 1.

[0045] The MR body coil 1 contains at least some components of a Dicke radiometer 6, namely here a radiometer antenna 7, a noise source 8 in the form of a grounded 50-Ohm resistance, a Dicke switch 9 that can be switched over between the radiometer antenna 7 and the noise source 8 with a specified switchover frequency, an input blocking filter (e.g. low-pass filter) 10 that is connected downstream of the Dicke switch 9 for the purpose of blocking frequencies of the MR band, and connected downstream of the input blocking filter 10 is a low-noise amplifier 11 and possibly further electronic components 12 such as a frequency converter for down-conversion of the incoming signals, with e.g. local oscillator, mixer, IF filter, A/D converter, microprocessor, etc.

[0046] The radiometer antenna 7 and the low-noise amplifier 11 both work in a useful band which lies above the MR band with a frequency interval. In the case of a 7-T MR scanner, the start of the useful band is e.g. at least 303 MHz, advantageously approximately 400 MHz, and can extend as far as e.g. 10 GHz or even higher, e.g. up to 60 GHz. The input blocking filter 10 can block frequencies below the useful band accordingly.

[0047] The generated noise signals can be down-converted by a frequency converter 12 before transfer to the control device 3 in order to keep cable attenuation low, for example, and to be able to share the use of any existing components of the MR body coil 1 that are already used for, e.g., signal transfer of MR signals.

[0048] The control device 3 is configured to determine from the noise signals of the Dicke radiometer 6 a body temperature of the patient P in the field of view or illumination region of the radiometer antenna 7. The body temperature advantageously is or includes an internal body temperature of the patient P that cannot be obtained using, e.g., IR cameras.

[0049] The control device 3 is also configured, e.g., programmed, to compare the measured body temperature with a specified temperature limit value and to adapt the MR transmit power of the MR scanner 2 accordingly.

[0050] In order to reduce any impedance mismatch between the patient P and the radiometer antenna 7, the cushion 4 and the housing wall 5 are impedance-matched.

[0051] The MR body coil 1 can include one or a plurality of Dicke radiometers 6.

[0052] Although the invention is illustrated and described in detail by the exemplary embodiments shown herein, the invention in not limited to these, and other variations can be derived therefrom by a person skilled in the art without thereby departing from the scope of the invention.

[0053] For example, one or a plurality of the components of the Dicke radiometer 6 shown in FIG. 1 as belonging to the MR body coil 1 can alternatively be present in the control device 3, e.g., the noise source 8 (which can also take the form of a noise diode), the Dicke switch 9, the input blocking filter 10, and/or further electronic components 12.

[0054] In general, “one”, “a”, etc. can be understood to signify single or multiple instances, particularly in the sense of “at least one” or “one or more”, etc., unless explicitly stated otherwise, e.g. by the expression “precisely one”, etc.

[0055] Likewise, a numerical specification can encompass both the number specified and a normal tolerance range unless explicitly stated otherwise.