# US 2013/0154642 A1 · Magnetic resonance imaging apparatus and magnetic resonance imaging method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154642 A1 - Document ID: US20130154642A1 - Status: Published application - Kind: A1 - Application number: 13/719,699 - Filed: 2012-12-19 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Toshiba Medical Systems Corporation; Kabushiki Kaisha Toshiba - Inventors: Kazuhiro SUEOKA - Web page: https://patentgrep.com/patent/US20130154642A1 ## CPC - G01R 33/34015: {Temperature-controlled RF coils} - G01R 33/56563: {caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract In one embodiment, an MRI apparatus (20) includes “a temperature measuring unit (70A to 70D) performing temperature measurement of a gradient magnetic field coil unit (26)”, a data storing unit (100), a pulse setting unit (102), and an imaging unit. The data storing unit stores the first and second data indicating a shift of a center frequency of magnetic resonance of hydrogen atoms. The first data corresponds to a case of temperature rise of the gradient magnetic field coil unit, and the second data corresponds to a case of temperature fall of that. The pulse setting unit corrects a center frequency of an RF pulse by calculating an estimated shift of the center frequency based on data corresponding to result of the temperature measurement out of the first and second data. The imaging unit performs magnetic resonance imaging based on the corrected RF pulse. ## Claims ### Claim 1 A magnetic resonance imaging apparatus, comprising: a gradient magnetic field coil unit configured to generate a gradient magnetic field in an imaging region according to a current supplied thereto; a temperature measuring unit configured to perform temperature measurement of the gradient magnetic field coil unit; a data storing unit configured to store “first data corresponding to a case of temperature rise of the gradient magnetic field coil unit” and “second data corresponding to a case of temperature fall of the gradient magnetic field coil unit”, the first and second data indicating a shift of a center frequency of magnetic resonance of a hydrogen atom in the imaging region as shift data; a pulse setting unit configured to perform judgment as to whether temperature of the gradient magnetic field coil unit has risen or fallen based on result of the temperature measurement, calculate an estimated shift of the center frequency of magnetic resonance based on data corresponding to result of the judgment out of the first data and the second data, and correct a center frequency of an RF pulse based on the estimated shift; and an imaging unit configured to transmit the RF pulse corrected by the pulse setting unit, acquire nuclear magnetic resonance signals from an object in the imaging region, and generate image data of the object based on the nuclear magnetic resonance signals. ### Claim 2 (depends on 1) The magnetic resonance imaging apparatus according to claim 1, wherein the data storing unit is configured to store “a plurality of shift data which correspond to a plurality of temperature regions respectively and indicate shift of the center frequency of magnetic resonance in response to temperature variation of the gradient magnetic field coil unit”. ### Claim 3 (depends on 2) The magnetic resonance imaging apparatus according to claim 2, wherein the plurality of shift data include ratios for each of the temperature regions of each of the first and second data, each of the ratios defining a proportion of “a temperature variation amount based on temperature measured by the temperature measurement unit” to “a shift amount of the center frequency of magnetic resonance of a hydrogen atom”. ### Claim 4 (depends on 3) The magnetic resonance imaging apparatus according to claim 3, wherein the gradient magnetic field coil unit includes an iron shim which corrects non-uniformity of a static magnetic field; and the ratios as the first and second data are defined so as to vary nonlinearly according to hysteresis behavior of temperature variation of magnetic permeability of the iron shims between each of the temperature regions. ### Claim 5 (depends on 3) The magnetic resonance imaging apparatus according to claim 3, wherein the pulse setting unit is configured to calculate the estimated shift by using “a temperature variation amount of the gradient magnetic field coil unit based on result of the temperature measurement” and “data corresponding to result of the judgment out of the first data and the second data”. ### Claim 6 (depends on 5) The magnetic resonance imaging apparatus according to claim 5, wherein the imaging unit is configured to perform “a plurality of data acquisition sequences to acquire the nuclear magnetic resonance signals used to generate a plurality of images” in chronological order; the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit before performance of each of the data acquisition sequences; and the pulse setting unit is configured to correct the center frequency of the RF pulse before performance of each of the data acquisition sequences. ### Claim 7 (depends on 6) The magnetic resonance imaging apparatus according to claim 6, wherein the imaging unit is configured to apply “a fat suppression prepulse as the RF pulse” to at least a part of the imaging region before acquiring the nuclear magnetic signals from the object. ### Claim 8 (depends on 5) The magnetic resonance imaging apparatus according to claim 5, wherein the imaging unit is configured to perform “dynamic imaging whose time phases respectively include acquisition of the nuclear magnetic resonance signals used to generate a plurality of images” by inserting a vacant time between each time phase; the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit during the vacant time; and the pulse setting unit is configured to correct the center frequency of the RF pulse during the vacant time. ### Claim 9 (depends on 8) The magnetic resonance imaging apparatus according to claim 8, wherein the imaging unit is configured to apply “a fat suppression prepulse as the RF pulse” to at least a part of the imaging region before acquiring the nuclear magnetic signals from the object. ### Claim 10 (depends on 5) The magnetic resonance imaging apparatus according to claim 5, wherein the imaging unit is configured to perform a first data acquisition sequence to acquire the nuclear magnetic resonance signals from “an object before administration of a contrast medium”, and then perform a second data acquisition sequence to acquire the nuclear magnetic resonance signals from “a same object having undergone administration of a contrast medium” after “elapse of a vacant time from completion of the first data acquisition sequence”; the temperature measurement unit is configured to measure respective temperatures of the gradient magnetic field coil unit before and after the vacant time; and the pulse setting unit is configured to perform the judgment and correct the center frequency of the RF pulse based on result of the judgment, during “a time span just before performance of the second data acquisition sequence”. ### Claim 11 (depends on 1) The magnetic resonance imaging apparatus according to claim 1, wherein the imaging unit is configured to perform “a plurality of data acquisition sequences to acquire the nuclear magnetic resonance signals used to generate a plurality of images” in chronological order; the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit before performance of each of the data acquisition sequences; and the pulse setting unit is configured to correct the center frequency of the RF pulse before performance of each of the data acquisition sequences. ### Claim 12 (depends on 1) The magnetic resonance imaging apparatus according to claim 1, wherein the imaging unit is configured to perform “dynamic imaging whose time phases respectively include acquisition of the nuclear magnetic resonance signals used to generate a plurality of images” by inserting a vacant time between each time phase; the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit during the vacant time; and the pulse setting unit is configured to correct the center frequency of the RF pulse during the vacant time. ### Claim 13 (depends on 1) The magnetic resonance imaging apparatus according to claim 1, wherein the imaging unit is configured to perform a first data acquisition sequence to acquire the nuclear magnetic resonance signals from “an object before administration of a contrast medium”, and then perform a second data acquisition sequence to acquire the nuclear magnetic resonance signals from “a same object having undergone administration of a contrast medium” after “elapse of a vacant time from completion of the first data acquisition sequence”; the temperature measurement unit is configured to measure respective temperatures of the gradient magnetic field coil unit before and after the vacant time; and the pulse setting unit is configured to perform the judgment and correct the center frequency of the RF pulse based on result of the judgment, during “a time span just before performance of the second data acquisition sequence”. ### Claim 14 (depends on 3) The magnetic resonance imaging apparatus according to claim 3, wherein the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit once, before performance of a main scan by the imaging unit; and the pulse setting unit is configured to store a predetermined temperature as a temperature of the gradient magnetic field coil unit before operation, and perform the judgment by comparing “the temperature of the gradient magnetic field coil unit measured by the temperature measurement unit” with the predetermined temperature. ### Claim 15 A magnetic resonance imaging apparatus, comprising: a gradient magnetic field coil unit configured to generate a gradient magnetic field in an imaging region according to a current supplied thereto; a temperature measuring unit configured to perform temperature measurement of the gradient magnetic field coil unit; a data storing unit configured to store “a plurality of shift data which correspond to a plurality of temperature regions respectively and indicate shift of a center frequency of magnetic resonance of a hydrogen atom in the imaging region in response to temperature variation of the gradient magnetic field coil unit”; a pulse setting unit configured to calculate an estimated shift of the center frequency of magnetic resonance of a hydrogen atom based on “temperature shift of the gradient magnetic field coil unit indicated by the temperature measurement” and “the shift data corresponding to a temperature region including temperature of the gradient magnetic field coil unit indicated by the temperature measurement”, and correct a center frequency of an RF pulse based on the estimated shift; and an imaging unit configured to transmit the RF pulse corrected by the pulse setting unit, acquire nuclear magnetic resonance signals from an object in the imaging region, and generate image data of the object based on the nuclear magnetic resonance signals. ### Claim 16 (depends on 15) The magnetic resonance imaging apparatus according to claim 15, wherein the plurality of shift data include ratios for each of the temperature regions, each of the ratios defining a proportion of “a temperature variation amount of the gradient magnetic field coil based on temperature measured by the temperature measurement unit” to “a shift amount of the center frequency of magnetic resonance of a hydrogen atom”. ### Claim 17 (depends on 16) The magnetic resonance imaging apparatus according to claim 16, wherein the imaging unit is configured to perform “dynamic imaging whose time phases respectively include acquisition of the nuclear magnetic resonance signals used to generate a plurality of images” by inserting a vacant time between each time phase; the temperature measurement unit is configured to measure temperature of the gradient magnetic field coil unit during the vacant time; and the pulse setting unit is configured to correct the center frequency of the RF pulse during the vacant time. ### Claim 18 (depends on 16) The magnetic resonance imaging apparatus according to claim 16, wherein the imaging unit is configured to apply “a fat suppression prepulse as the RF pulse” to at least a part of the imaging region before acquiring the nuclear magnetic signals from the object. ### Claim 19 A magnetic resonance imaging method comprising the steps of: performing temperature measurement of a gradient magnetic field coil unit of a magnetic resonance apparatus; performing judgment as to whether temperature of the gradient magnetic field coil unit has risen or fallen, based on result of the temperature measurement; calculating an estimated shift of a center frequency of magnetic resonance of a hydrogen atom in an imaging region based on data corresponding to result of the judgment out of “first data corresponding to a case of temperature rise of the gradient magnetic field coil unit” and “second data corresponding to a case of temperature fall of the gradient magnetic field coil unit”, the first and second data indicating a shift of the center frequency of magnetic resonance; correcting a center frequency of an RF pulse based on the estimated shift; acquiring nuclear magnetic resonance signals from an object in the imaging region by transmitting “the RF pulse whose center frequency is corrected based on the estimated shift” generating image data of the object based on the nuclear magnetic resonance signals.