Magnetic resonance imaging apparatus and method utilizing RF pulse flip angels
AssigneeGE Medical Systems Global Technology Company, LLC
InventorMitsuharu Miyoshi
Life of this patent
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Abstract
A magnetic resonance imaging (MRI) apparatus sequentially transmits a plurality of radio frequency (RF) pulses having flip angles of α1°, α2°, −α1°, and −α2° for refocusing transverse magnetization of spins, and brings the transverse magnetization of the spins to longitudinal magnetization after the refocusing of the transverse magnetization of the spins.
Claims14
A magnetic resonance imaging (MRI) apparatus for magnetic resonance angiography (MRA) comprising a coil assembly configured to sequentially transmit a plurality of consecutive radio frequency (RF) pulses α1°θ1°, α2°θ2°, −α1°θ1°, and −α2°θ2° one after another, wherein α1°, α2°, −α1°, and −α2° are the flip angles of the RF pulses, and wherein θ1° and θ2° are the phases of the RF pulses, wherein the four consecutive RF pulses are transmitted for refocusing transverse magnetization of spins and to cause the transverse magnetization of the spins to change to longitudinal magnetization after the refocusing of the transverse magnetization of the spins, wherein a combination of the flip angles α1°, α2°, −α1°, and −α2° of the RF pulses α1°θ1°, α2°θ2°, −α1°θ1°, and −α2°θ2° corresponds to any of the following combinations:
- (α1°, α2°, −α1°, −α2°)=(180°−Δd1°, 180°+Δd2°, −(180°−Δd1°), −(180°+Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°+Δd1°, −(180°−Δd2°), −(180°+Δd1°), 180°−Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°−Δd1°), −(180°+Δd2°), 180°−Δd1°, 180°+Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°+Δd1°), 180°−Δd2°, 180°+Δd1°, −(180°−Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°+Δd1°, 180°−Δd2°, −(180°+Δd1°), −(180°−Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°−Δd1°, −(180°+Δd2°), −(180°−Δd1°), 180°+Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°+Δd1°), −(180°−Δd2°), 180°+Δd1°, 180°−Δd2°);
- and
- (α1°, α2°, −α1°, −α2°)=(−(180°−Δd1°), 180°+Δd2°, 180°−Δd1°, −(180°+Δd2°)),
- where Δd1° is an angle greater than 0° and less than 180° and Δd2° is an angle greater than 0° and less than 180°, and wherein said coil assembly is further configured to:
- transmit an RF pulse β°δ°, wherein β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse β°δ° is transmitted prior to the RF pulse α1°θ1°, and
- transmit an RF pulse −β°δ°, wherein −β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse −β°δ° is transmitted after the RF pulse −α2°θ2°.
A magnetic resonance imaging (MRI) apparatus for magnetic resonance angiography (MRA) comprising a coil assembly configured to sequentially transmit a plurality of consecutive radio frequency (RF) pulses α1°θ1°, α2°θ2°, α1°θ1°, and α2°θ2° one after another, wherein α1° and α2° are the flip angles of the RF pulses, and wherein θ1° and θ2° are the phases of the RF pulses, wherein the four RF pulses are transmitted for refocusing transverse magnetization of spins, and to cause the transverse magnetization of the spins to change to longitudinal magnetization after the refocusing of the transverse magnetization of the spins,
- wherein a combination of the flip angles α1° and α2° corresponds to any of the following combinations:
- (α1°, α2°)=(180°−Δd1°, 180°+Δd2°);
- (α1°, α2°)=(180°+Δd1°, −(180°−Δd2°));
- (α1°, α2°)=(−(180°−Δd1°), −(180°+Δd2°));
- (α1°, α2°)=(−(180°+Δd1°), 180°−Δd2°);
- (α1°, α2°)=(180°+Δd1°, 180°−Δd2°);
- (α1°, α2°)=(180°−Δd1°, −(180°+Δd2°));
- (α1°, α2°), =(−(180°+Δd1°), −(180°−Δd2°));
- and
- (α1, α2°)=(−(180°−Δd1°), 180°+Δd2°), where
- Δd1° is an angle greater than 0° and less than 180° and Δd2° is an angle greater than 0° and less than 180°, and wherein said coil assembly is further configured to:
- transmit an RF pulse δ°δ°, wherein β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse δ°δ° is transmitted prior to the first α1°θ1° RF pulse, and
- transmit an RF pulse −β°δ°, wherein −β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse −β°δ° is transmitted after the second-α2°θ2° RF pulse.
A method of magnetic resonance imaging for magnetic resonance angiography comprising:
- sequentially transmitting, using a coil assembly, a plurality of consecutive radio frequency (RF) pulses α1°θ1°, α2°θ2°, −α1°θ1°, and −α2°θ2° one after another, wherein α1°, α2°, −α1°, and −α2° are the flip angles of the RF pulses, and wherein θ1° and θ2° are the phases of the RF pulses, wherein the four RF pulses are transmitted for refocusing transverse magnetization of spins and to cause the transverse magnetization of the spins to change to longitudinal magnetization after the refocusing of the transverse magnetization of the spins;
- transmitting an RF pulse β°δ°, wherein β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse β°δ° is transmitted prior to the RF pulse α1°θ1°;
- and
- transmitting an −β°δ°, wherein −β° is the flip angle, and δ° is the phase of RF pulse, wherein the RF pulse −β°δ° is transmitted after the RF pulse −α2°θ2°,
- wherein a combination of the flip angles α1°, α2°, −α1°, and −α2° of the RF pulses α1°θ1°, α2°θ2°, −α1°θ1°, and −α2°θ2° corresponds to any of the following combinations:
- (α1°, α2°, −α1°, −α2°)=(180°−Δd1°, 180°+Δd2°, −(180°−Δd1°), −(180°+Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°+Δd1°, −(180°−Δd2°), −(180°+Δd1°), 180°−Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°−Δd1°), −(180°+Δd2°), 180°−Δd1°, 180°+Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°+Δd1°), 180°−Δd2°, 180°+Δd1°, −(180°−Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°+Δd1°, 180°−Δd2°, −(180°+Δd1°), −(180°−Δd2°));
- (α1°, α2°, −α1°, −α2°)=(180°−Δd1°, −(180°+Δd2°), −(180°−Δd1°), 180°+Δd2°);
- (α1°, α2°, −α1°, −α2°)=(−(180°+Δd1°), −(180°−Δd2°), 180°+Δd1°, 180°−Δd2°);
- and
- (α1°, α2°, −α1°, −α2°)=(−(180°−Δd1°), 180°+Δd2°, 180°−Δd1°, −(180°+Δd2°)),
- where Δd1° is an angle greater than 0° and less than 180° and Δd2° is an angle greater than 0° and less than 180°.
Dependencies are inferred from the claim text.