# US 10,369,385 B2 · Quantitative MRI measurements near metal objects

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- Number: US 10,369,385 B2
- Document ID: US10369385B2
- Status: Granted
- Kind: B2
- Application number: 14/686,455
- Filed: 2015-04-14
- Published: 2016-10-20
- Granted: 2019-08-06
- Earliest claimed: 2015-04-14
- Assignees: The Board of Trustees of the Leland Stanford Junior University
- Applicants: The Board of Trustees of the Leland Stanford Junior University
- Inventors: Hans Weber; Daehyun Yoon; Valentina Taviani; Brian A. Hargreaves
- Web page: https://patentgrep.com/patent/US10369385B2

## CPC

- A61N 7/02: Localised ultrasound hyperthermia
- A61B 5/055: involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
- A61B 18/12: by passing a current through the tissue to be heated, e.g. high-frequency current
- A61N 1/403: {for thermotherapy, e.g. hyperthermia}
- G01R 33/4804: {Spatially selective measurement of temperature or pH}
- G01R 33/50: based on the determination of relaxation times {, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences}
- G01R 33/56527: {due to chemical shift effects}
- A61B 5/062: {using magnetic field}
- A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A method for providing at least one measurement by a magnetic resonance imaging (MRI) system of a tissue property or underlying tissue property in a region sufficiently close to a metal object, so that the metal object induces artifacts is provided. At least one magnetic resonance imaging signal from the region is acquired through the MRI system. The acquired at least one MRI signal is processed to correct for artifacts induced by the metal object. At least one tissue property or underlying tissue property measurement is extracted from the processed at least one MRI signal.

## Claims

### Claim 1

A method for providing at least one measurement by an MRI system of a tissue property or underlying tissue property in a region sufficiently close to a metal object, so that the metal object induces artifacts, comprising:
acquiring through the magnetic resonance imaging (MRI) system at least one magnetic resonance imaging signal from the region, wherein the acquiring at least one MRI signal compensates for the artifacts induced by the metal object, wherein the acquiring at least one MRI signal comprises acquiring a plurality of MRI signals from the region, and wherein the acquiring uses a multispectral imaging and wherein the acquiring uses a spatially selective inversion pulse matched to excitation;
processing the acquired at least one MRI signal to correct for artifacts induced by the metal object;
extracting at least one tissue property and underlying tissue property measurement by comparing the plurality of MRI signals;
measuring a variation in the at least one tissue property; and
using the variation in the at least one tissue property to determine the underlying tissue property measurement, which is temperature.

### Claim 2 (depends on 1)

The method, as recited in claim 1, further comprising using the measured tissue property to determine the at least one underlying tissue property.

### Claim 3 (depends on 1)

The method, as recited in claim 1, wherein the acquiring of MRI signals is a 2D acquisition.

### Claim 4 (depends on 3)

The method, as recited in claim 3, wherein the tissue property is at least one of T1, T2, or proton density.

### Claim 5 (depends on 1)

The method, as recited in claim 1, further comprising
providing thermal therapy to the region; and
using the measured temperature to control the thermal therapy device.

### Claim 6 (depends on 1)

The method, as recited in claim 1, wherein the temperature measurement is an absolute temperature measurement.

### Claim 7 (depends on 1)

The method, as recited in claim 1, wherein the temperature measurement is a relative temperature measurement.

### Claim 8 (depends on 1)

The method, as recited in claim 1, wherein the acquiring at least one MRI signal is used to determine a relative distribution of the underlying tissue property.

### Claim 9 (depends on 1)

The method, as recited in claim 1, wherein the acquiring at least one MRI signal comprises acquiring a plurality of MRI signals from the region, and wherein the method further comprises comparing the plurality of MRI signals to measure a relative change of the underlying tissue property.

### Claim 10

A method for providing a thermal therapy treatment using an MRI system and a thermal therapy device in a region sufficiently close to a metal object, so that the metal object induces artifacts, comprising:
heating the region using the thermal therapy device;
acquiring through the MRI system at least one MRI signal from the region, wherein the acquiring uses a multispectral imaging and wherein the acquiring uses a spatially selective inversion pulse matched to excitation;
processing the acquired at least one MRI signal to correct for artifacts induced by the metal object;
extracting temperature from the processed at least one MRI signal; and
changing the heating of the region based on the extracted temperature.

### Claim 11

A system for providing thermal therapy treatment to a region sufficiently close to a metal object, so that the metal object induces artifacts, comprising:
a thermal therapy device for providing heat to the region;
a MRI system; and
a controller comprising:
a central processing unit; and
tangible computer readable media, comprising:
computer readable code for heating the region using the thermal therapy device;
computer readable code for acquiring through the MRI system at least one MRI signal from the region, wherein the acquiring uses a multispectral imaging and wherein the acquiring uses a spatially selective inversion pulse matched to excitation;
computer readable code for processing the acquired at least one MRI signal to correct for artifacts induced by the metal object;
computer readable code for extracting temperature from the processed at least one MRI signal; and
computer readable code changing the heating of the region based on the extracted temperature.

### Claim 12 (depends on 11)

The system, as recited in claim 11, wherein the computer readable code for acquiring through the MRI system at least one MRI signal from the region magnetic resonance imaging system uses a two dimensional multispectral imaging acquisition.

### Claim 13 (depends on 12)

The system, as recited in claim 12, wherein the computer readable code for processing at least one MRI signal to correct for artifacts induced by the metal objects corrects for signal loss artifacts and pile-up artifacts induced by the metal objects.

### Claim 14 (depends on 10)

The method, as recited in claim 10, wherein the acquiring through the MRI system uses a two dimensional multispectral imaging acquisition.

### Claim 15 (depends on 14)

The method, as recited in claim 14, wherein the processing the acquired at least one MRI signal to correct for artifacts induced by the metal objects corrects for signal loss artifacts and pile-up artifacts induced by the metal objects.

### Claim 16 (depends on 1)

The method, as recited in claim 1, wherein the acquiring through the magnetic resonance imaging system uses a two dimensional multispectral imaging acquisition.

### Claim 17 (depends on 16)

The method, as recited in claim 16, wherein the processing the acquired at least one MRI signal to correct for artifacts induced by the metal objects corrects for signal loss artifacts and pile-up artifacts induced by the metal objects.

### Claim 18 (depends on 16)

The method, as recited in claim 16, wherein the two dimensional multispectral imaging acquisition comprises reversing a selection gradient between excitation and refocusing pulses resulting in an excitation of finite spectral and spatial regions to provide reduced distortion near the metal object.