Temperature monitoring method, temperature monitoring apparatus and magnetic resonance apparatus

• US 6,194,899 B1
• Filed: 02/17/1999
• Issued: 02/27/2001
• Est. Priority Date: 02/19/1998
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Okamoto, Kazuya, Umeda, Masaaki, Ishihara, Yasutoshi, Watanabe, Hidehiro
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US09/251,488
• Time in Patent Office: 741 Days
• Field of Search: 324/315, 324/306, 324/307, 324/309, 324/300, 600/410, 600/412
• US Class Current: 324/315
• CPC Class Codes: G01R 33/4804 Spatially selective measurement of temperature or pH

Abstract

An absolute temperature measuring pulse sequence is executed and, subsequently, a relative temperature measuring pulse sequence is repeatedly executed. Since while a relative temperature can be measured from phase information, an absolute temperature requires frequency information, a time required in the relative temperature measuring pulse can be made shorter than that required in the absolute temperature measuring pulse sequence. Since the relative temperature reveals a temperature variation, if an absolute temperature at a given time is known, an absolute temperature at a subsequent time can be calculated from the relative temperature. Thus, a local internal temperature of the subject can be measured, with a shorter temporal resolution, with the use of the absolute temperature and relative temperature.

Claims

1. A temperature monitoring apparatus comprising:

a radio frequency magnetic field generator configured to generate a radio frequency magnetic field;

a gradient magnetic field generator configured to generate a gradient magnetic field;

a detector configured to detect a magnetic resonance signal from a subject;

a sequence controller configured to control the radio frequency magnetic field generator, the gradient magnetic field generator, and the detector, and configured to execute an absolute temperature measuring pulse sequence and repeatedly execute a relative temperature measuring pulse sequence following the absolute temperature measuring pulse sequence; and

a first processing mechanism configured

to calculate the absolute temperature of a region of interest in the subject based on frequency information of the magnetic resonance signal detected from the subject in response to the absolute temperature measuring pulse sequence,

to calculate the relative temperature of the region of interest in the subject based on phase information of the magnetic resonance signal detected from the subject in response to the relative temperature measuring pulse sequence, and

to convert the measured relative temperature to a corresponding absolute temperature based on the calculated absolute temperature.

2. The temperature monitoring apparatus of claim 1, wherein:

the first processing mechanism calculates the absolute temperature based on a chemical shift difference between a specific nucleus in a first molecule and the specific nucleus in a second molecule, and

a first magnetic resonance frequency of the first molecule is temperature dependent, and a second magnetic resonance frequency of the second molecule is not temperature dependent.

3. The temperature monitoring apparatus of claim 1, wherein:

the first processing mechanism calculates the relative temperature based on a phase variation of the magnetic resonance signal detected from a specific nucleus in a first molecule, and

a magnetic resonance frequency of the first molecule is temperature dependent.

4. The temperature monitoring apparatus of claim 1, wherein the sequence controller executes as the absolute temperature measuring pulse sequence the following sequence:

a radio frequency magnetic field pulse applied concurrently with a slice select gradient magnetic field pulse, followed by

a first encoding gradient magnetic field pulse applied concurrently with a second encoding gradient magnetic field pulse,

the first encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a first axial direction,

the second encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a second axial direction, and

the first encoding gradient magnetic field pulse and the second encoding gradient magnetic field pulse adding position information to the magnetic resonance signal detected from the subject.

5. The temperature monitoring apparatus of claim 1, wherein the sequence controller executes as the relative temperature measuring pulse sequence the following sequence:

a radio frequency magnetic field pulse applied concurrently with a slice select gradient magnetic field pulse, followed by

a phase encoding gradient magnetic field pulse applied concurrently with a frequency encoding gradient magnetic field pulse,

the phase encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a first axial direction and adding position information to the magnetic resonance signal detected from the subject, and

the frequency encoding gradient magnetic field pulse being executed with respect to a second axial direction.

6. The temperature monitoring apparatus of claim 1, further comprising:

a second processing mechanism configured

to calculate a magnetic resonance frequency based on the magnetic resonance signal detected from a specific nucleus in a specific molecule, and

to detect a motion error of the subject based on a temporal variation of the calculated magnetic resonance frequency;

wherein a magnetic resonance frequency of the specific molecule is not temperature dependent.

8. The magnetic resonance apparatus of claim 1, wherein the sequence controller executes as the absolute temperature measuring pulse sequence the following sequence:

a radio frequency magnetic field pulse applied concurrently with a slice select gradient magnetic field pulse, followed by

a first encoding gradient magnetic field pulse applied concurrently with a second encoding gradient magnetic field pulse,

the first encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a first axial direction,

the second encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a second axial direction, and

the first encoding gradient magnetic field pulse and the second encoding gradient magnetic field pulse adding position information to the magnetic resonance signal detected from the subject.

9. The magnetic resonance apparatus of claim 1, wherein the sequence controller executes as the relative temperature measuring pulse sequence the following sequence:

a radio frequency magnetic field pulse applied concurrently with a slice select gradient magnetic field pulse, followed by

a phase encoding gradient magnetic field pulse applied concurrently with a frequency encoding gradient magnetic field pulse,

the phase encoding magnetic field pulse providing phase encoding and being executed with respect to a first axial direction, and adding position information to the magnetic resonance signal detected from the subject, and

the frequency encoding gradient magnetic field pulse being executed with respect to a second axial direction.

7. A magnetic resonance apparatus, comprising:

a radio frequency magnetic field generator configured to generate a radio frequency magnetic field;

a gradient magnetic field generator configured to generate a gradient magnetic field;

a detector configured to detect a magnetic resonance signal from a subject;

a sequence controller configured to control the radio frequency magnetic field generator, the gradient magnetic field generator, and the detector, and configured to execute an absolute temperature measuring pulse sequence and subsequently, to execute repeatedly a relative temperature measuring pulse sequence;

a first processing mechanism configured to calculate the absolute temperature of a region of interest in the subject based on frequency information of the magnetic resonance signal detected from the subject in response to the absolute temperature measuring pulse sequence; and

a second processing mechanism configured to calculate the relative temperature of the region of interest based on phase information of a magnetic resonance signal detected from the subject in response to the relative temperature measuring pulse sequence.

10. The magnetic resonance apparatus of claim 7, further comprising:

a third processing mechanism configured

to calculate a magnetic resonance frequency based on the magnetic resonance signal detected from a specific nucleus in a specific molecule, and

to detect a motion error of the subject based on a temporal variation of the calculated magnetic resonance frequency,

a magnetic resonance frequency of the specific molecule is not temperature dependent.

11. A method for monitoring a temperature, comprising:

executing an absolute temperature measuring pulse sequence;

measuring the absolute temperature of a region of interest in a subject based on frequency information of a magnetic resonance signal detected from the subject in response to the absolute temperature measuring pulse sequence; and

determining repeatedly a corresponding absolute temperature from a relative temperature, including

executing a relative temperature measuring pulse sequence, including,

measuring the relative temperature of the region of interest in the subject based on phase information of the magnetic resonance signal detected from the subject in response to the relative temperature measuring pulse sequence, and

converting the relative temperature into the corresponding absolute temperature based on the absolute temperature.

12. The method of claim 11, wherein measuring of the absolute temperature comprises calculating the absolute temperature based on a chemical shift difference between a specific nucleus in a first molecule and the specific nucleus in a second molecule, and

a first magnetic resonance frequency of the first molecule is temperature dependent, and a second magnetic resonance of the second molecule is not temperature dependent.

13. The method of claim 11, wherein measuring the relative temperature comprises measuring a phase variation of the magnetic resonance signal detected from a specific nucleus in a first molecule, and

a magnetic resonance frequency of the first molecule is temperature dependent.

14. The method of claim 11, wherein executing the absolute temperature measuring pulse sequence comprises,

applying a radio frequency magnetic field pulse concurrently with a slice select gradient magnetic field pulse, followed by

applying a first encoding gradient magnetic field pulse concurrently with a second encoding gradient magnetic field pulse,

the first encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a first axial direction,

the second encoding gradient magnetic field pulse providing phase encoding and being executed with respect to a second axial direction, and

the first encoding gradient magnetic field pulse and the second encoding gradient magnetic field pulse adding position information to the magnetic resonance signal detected from the subject.

15. The method of claim 11, wherein executing repeatedly the relative temperature measuring pulse sequence comprises:

applying a radio frequency magnetic field pulse concurrently with a slice select gradient magnetic field pulse, followed by

applying a phase encoding gradient magnetic field pulse concurrently with a frequency encoding gradient magnetic field pulse,

the phase encoding magnetic field pulse providing phase encoding and being executed with respect to a first axial direction, and adding position information to the magnetic resonance signal detected from the subject, and

the frequency encoding gradient magnetic field pulse being executed with respect to a second axial direction.

16. The method of claim 11, further comprising:

receiving an instruction to interrupt the determining repeatedly step;

performing the executing the absolute temperature measuring pulse sequence step;

performing the measuring the absolute temperature step; and

performing the determining repeatedly step.

17. The method of claim 16, wherein performing the measuring the absolute temperature step comprises determining a new value of the absolute temperature.

18. The method of claim 16, further comprising after the measuring the absolute temperature step:

calculating a magnetic resonance frequency based on the magnetic resonance signal detected from a specific nucleus in a specific molecule; and

detecting a motion error of the subject based on a temporal variation of the calculated magnetic resonance frequency,

a magnetic resonance frequency of the specific molecule not being temperature dependent.

19. A method for monitoring a temperature comprising:

executing an absolute temperature measuring pulse sequence;

measuring the absolute temperature of a region of interest in a subject based on frequency information of a magnetic resonance signal detected from the subject in response to the absolute temperature measuring pulse sequence;

determining repeatedly a corresponding absolute temperature from a relative temperature, including

executing a relative temperature measuring pulse sequence

measuring the relative temperature of the region of interest in the subject based on phase information of the magnetic resonance signal detected from the subject in response to the relative temperature measuring pulse sequence, and

converting the relative temperature into the corresponding absolute temperature based on the absolute temperature; and

performing repeatedly

the executing the absolute temperature measuring pulse sequence step,

the measuring the absolute temperature step, and

the determining repeatedly step.

20. The method of claim 19, further comprising after the measuring the absolute temperature step:

calculating a magnetic resonance frequency based on the magnetic resonance signal detected from a specific nucleus in a specific molecule; and

detecting a motion error of the subject based on a temporal variation of the calculated magnetic resonance frequency,

a magnetic resonance frequency of the specific molecule not being temperature dependent.