Magnetic resonance imaging method and apparatus
A magnetic resonance (MR) tomography apparatus has an array composed of a number n of single coils E i to acquire reception signals I i . The tomography apparatus is operated by a method that includes the following steps. For each single coil E i , a processor determines, or is provided with, an individual reception sensitivity profile in positional space r B1 i − (r). An examination subject introduced into the MR tomography apparatus is scanned to acquire reception signals I i (k) in the frequency domain with the n reception coils E i . Fourier-transformed signals IF i (r) are determined from the reception signals I i (k). Complexly corrected signals ĨF i (r) are determined on the basis of the signals IF i (r) and the individual reception sensitivity profiles B1 i − (r). A sum signal MR(r) is determined by complex addition of the corrected signals ĨF i (r). Image data of the examination subject are reconstructed on the basis of the sum signal MR(r).
1. A method for generating a magnetic resonance (MR) image using an MR tomography apparatus, having an array comprising a number n of single coils E i , in order to acquire reception signals I i , with i=1, . . . , n, respectively with said n single coils said method comprising:
for each single coil E i , determining in a processor or providing a processor with, an individual reception sensitivity profile in the spatial domain r B1 i − (r):
B 1 i − ( r )=| a i ( r )|* e i●φ i (r)
with amplitude a i (r) and phase φ i (r);
using the processor to operate the MR tomography apparatus in order to scan an examination subject introduced into the MR tomography apparatus so as to acquire reception signals Ii(k) in the frequency domain with wave number k via the n reception coils E i ;
in said processor, determining Fourier-transformed signals IFi(r) from the reception signals Ii(k), wherein:
IF i ( r )=ρ( r )· e iϕ(r) ·B 1 i − ( r )+ N
with N:=noise term, ρ(r)·e iϕ(r) :=proton density;
in said processor, determining complexly corrected signals ĨF i (r) on the basis of the signals IFi(r) and the individual reception sensitivity profiles B1 i − (r);
in said processor, determining a sum signal MR(r) via complex addition of the corrected signals ĨF i (r);
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F
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;
in said processor, reconstructing image data of the examination subject on the basis of the sum signal MR(r), and making the image data available at an output of the processor as an electronic data file; and
at a display monitor in communication with said processor, displaying an image, corresponding to said image data, of the examination subject.
2. A method according to claim 1 , comprising:
determining or providing the individual reception sensitivity profiles B1 i − (r) as relative reception sensitivities S i rel , and determining the complexly corrected signals ĨF i (r) are determined on the basis of the relative signals IF i (r).
3. A method according to claim 1 comprising:
determining the individual reception sensitivity profiles B1 i − (r) is said processor from SENSE imaging data or B1 mapping data acquired with the MR tomography apparatus.
4. A method according to claim 1 comprising:
correcting the amplitudes and phases of the signals I i (r) when determining the complexly corrected signals ĨF i (r).
5. A method according to claim 1 comprising:
correcting only the amplitudes of the signals I i (r) when determining the complexly corrected signals ĨF i (r).
6. A method according to claim 1 comprising:
correcting only the phases of the signals I i (r) when determining the complexly corrected signals ĨF i (r).
7. A method according to claim 1 comprising:
determination of the complexly corrected signals ĨF i (r) according to:
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8. A magnetic resonance (MR) tomography apparatus comprising:
an MR data acquisition unit comprising a radio frequency (RF) transmission system comprising a number n of single RF coils E i with which reception signals I i are respectively acquired, with i=1, . . . , n;
a processor provided with or configured to determine, for each single coil E i , an individual reception sensitivity profile in the spatial domain r B1 i − (r):
B 1 i − ( r )=| a i ( r )|* e i●φ i (r)
with amplitude a i (r) and phase φ i (r);
said processor being configured to operate the MR tomography apparatus to scan an examination subject introduced into the MR tomography apparatus to acquire reception signals I i (k) in the frequency domain with wave number k via the n reception coils E i ;
said processor being configured to determine Fourier-transformed signals IF i (r) from the reception signals I i (k), wherein:
IF i ( r )=ρ( r )· e iϕ(r) ·B 1 i − ( r )+ N
with N:=noise term, ρ(r)·e iϕ(r) :=proton density;
said processor being configured to determine complexly corrected signals ĨF i (r) on the basis of the signals IF i (r) and the individual reception sensitivity profiles B1 i − (r);
said processor being configured to determine a sum signal MR(r) via complex addition of the corrected signals ĨF i (r):
MR
(
r
)
=
∑
i
I
~
F
i
(
r
)
;
said processor being configured to reconstruct image data of the examination subject on the basis of the sum signal MR(r), and to make the image data available at an output of the processor as an electronic data file;
a display monitor in communication with said processor; and
said processor being configured to display, at said display monitor, an image, corresponding to said image data, of the examination subject.
9. A non-transitory, computer-readable data storage medium encoded with programming instructions, said data storage medium being loaded into a computerized control and processing system of a magnetic resonance (MR) tomography apparatus having an array comprising a number n of single coils E i operable to respectively acquire reception signals with i=1, . . . , n, said programming instructions causing said control and processing system to:
for each single coil E i , determine or receive an individual reception sensitivity profile in the spatial domain r B1 i − (r):
B 1 i − ( r )=| a i ( r )|* e i●φ i (r)
with amplitude a i (r) and phase φ i (r);
operate the MR tomography apparatus to scan an examination subject introduced into the MR tomography apparatus to acquire reception signals I i (k) in the frequency domain with wave number k via the n reception coils E i ;
determine Fourier-transformed signals IF i (r) from the reception signals I i (k), wherein:
IF i ( r )=ρ( r )· e iϕ(r) ·B 1 i − ( r )+ N
with N:=noise term, ρ(r)·e iϕ(r) :=proton density;
determine complexly corrected signals ĨF i (r) on the basis of the signals IF i (r) and the individual reception sensitivity profiles B1 i − (r);
determine a sum signal MR(r) via complex addition of the corrected signals ĨF i (r)
MR
(
r
)
=
∑
i
I
~
F
i
(
r
)
;
reconstruct image data of the examination subject on the basis of the sum signal MR(r), and make the image data available at an output of the processor as an electronic data file; and
at a display monitor in communication with said processor, display an image, corresponding to said image data, of the examination subject.