Flow adaptive guided determination of imaging parameters for 3D magnetic resonance angiography

A method of magnetic resonance angiography comprising:

• exciting magnetic resonance in a volume of a subject;
• receiving magnetic resonance signals from selected dipoles in subvolumes in the volume;
• determining an intensity of the received resonance signals from each subregion;
• fitting variations in the determined signal intensities to a polynomial;
• selecting RF pulse profiles which vary across the volume in accordance with the polynomial;
• and,
• conducting an imaging scan of the volume with a radio frequency pulse sequence which incorporates the selected RE pulse profiles.

A method of magnetic resonance angiography comprising:

• exciting magnetic resonance in a volume of a subject;
• receiving magnetic resonance signals from selected dipoles within the volume including:
• partitioning the volume into a plurality of one of slices and slabs;
• collecting a line of k-space data from each of the plurality of slices or slabs;
• from the lines of k-space data, determining differences in a signal intensity from slice to slice or slab to slab;
• designing a radio frequency pulse sequence based on the received magnetic resonance signals including:
• analyzing a tip angle saturation factor;
• constructing an RF pulse sequence from the intensity differences that does not saturate tip angles;
• and
• conducting an imaging scan using the designed radio frequency pulse sequence.

A method of magnetic resonance angiography comprising:

• partitioning a volume into a plurality of one of slices and slabs;
• exciting resonance in the volume and collecting k-space data spanning the volume;
• from the k-space data, determining differences in a signal intensity across the volume;
• selecting an RF tip angle for each slice or slab in accordance with the determined intensity differences;
• and
• implementing an imaging scan with a radio frequency pulse sequence having the selected tip angles.

A magnetic resonance apparatus comprising:

• a main magnet assembly for generating a main magnetic field through an imaging region wherein is located a subject;
• a gradient coil assembly which spatially encodes the main magnetic field;
• a radio frequency coil assembly which excites and manipulates magnetic resonance in selected dipoles of the subject with radio frequency pulses;
• a receiver which receives magnetic resonance signals from the resonating dipoles and generates corresponding data lines;
• an intensity analyzer which receives at least one data line from each of a plurality of subregions of the imaging region and determines a signal intensity for each subregion;
• a radio frequency pulse sequence synthesizer which adjusts a tip angle of radio frequency pulses for each subregion in accordance with the signal intensity determined for each subregion.

A magnetic resonance apparatus comprising:

• a means for determining a flow rate of a fluid at selected points along a vessel of interest;
• a means for determining a geometry of the vessel;
• a means for adjusting a radio frequency pulse profile based on the flow rates and geometry;
• a means for applying the profile adjusted radio frequency pulses and spatially encoding pulses to the vessel of interest to generate spatially encoded magnetic resonance signals in the fluid;
• a means for demodulating the resonance signal to generate data lines;
• a means for reconstructing the data lines into an image representation.

A magnetic imaging apparatus comprising:

• a means for generating magnetic resonance signals in selected dipoles in each of a plurality of subregions of a region of interest, at least some of the selected dipoles being in flowing material, by applying at least one of radio frequency excitation and resonance manipulation pulses with a spatially adjustable tip angle;
• a means for measuring an intensity of the magnetic resonance signals from each of the subregions;
• a means for adjusting the tip angle of the radio frequency pulses corresponding to each subregion in accordance with differences in the measured intensities;
• and,
• a means for generating a volumetric image representation of the region of interest using the dynamically adjusted RF profiles based on subject-dependent calibration data.

A magnetic resonance method comprising:

• generating a main magnetic field through an imaging region in which a subject is located;
• spatially encoding the main magnetic field;
• exciting and manipulating magnetic resonance in a volume of interest of the subject with a calibration pulse sequence to encode at least one data line in each of a plurality of subregions of the region of interest;
• receiving the magnetic resonance signals and determining a signal intensity for each subregion from the data lines;
• selecting tip angles for radio frequency pulses to be applied across the region of interest in an imaging sequence in accordance with the intensity determined for each subregion;
• conducting a magnetic resonance imaging sequence utilizing the selected tip angles to generate a volumetric image data set;
• reconstructing the volumetric image data set into a volumetric image representation of the region of interest.

A magnetic resonance imaging method comprising:

• determining flow rates of a fluid at selected points along a vessel in a region of interest;
• determining a geometry of the vessel;
• adjusting a radio frequency pulse profile based on the determined flow rates and the determined geometry;
• applying the profile adjusted radio frequency pulses and spatial encoding pulses to the region of interest to generate spatially encoded magnetic resonance signals from the vessel and fluid flowing in the vessel;
• demodulating the resonance signal;
• and
• reconstructing the demodulated magnetic resonance signals into an image representation of the vessel and the fluid.