Contrast-enhanced MRA including an effective zero-latency method of bolus detection

A method of magnetic resonance angiography comprising:

• (a) injecting a subject with a bolus of a magnetic resonance contrast agent upstream from a volume of interest;
• (b) exciting magnetic resonance in the volume of interest;
• (c) inducing magnetic resonance echoes, said echoes generating magnetic resonance signals;
• (d) repeatedly sampling a central portion of k-space, creating a plurality of central data sets;
• (e) reconstructing a portion of each central data set into a low-resolution maximum intensity projection of an image representations;
• (f) determining the arrival of a leading edge of a bolus of the contrast agent within the volume of interest from the maximum intensity projection;
• (g) after detecting the arrival of the leading edge of the bolus, sampling portions of k-space peripheral to the central portion of k-space, creating peripheral data sets;
• and,
• (h) reconstructing a magnetic resonance angiograph from (i) the last central data set collected before sampling the peripheral data sets, and (ii) the peripheral data sets.

The method of magnetic resonance angiography comprising:

• (a) injecting a subject with a bolus of a magnetic resonance contrast agent upstream from a volume of interest;
• (b) exciting magnetic resonance in the volume of interest;
• (c) inducing magnetic resonance echoes, said echoes generating magnetic resonance signals;
• (d) continuously sampling a central portion of k-space, creating a plurality of central data sets;
• (e) detecting the arrival of a leading edge of a bolus of the contrast agent within the volume of interest;
• (f) after detecting the arrival of the leading edge of the bolus, sampling portions of k-space peripheral to the central portion of k-space, creating peripheral data sets;
• and,
• (g) reconstructing a magnetic resonance angiograph from (i) the central data set from which arrival of the bolus was detected, and (ii) the peripheral data sets collected after the detection of the bolus;
• (h) after detecting the arrival of the leading edge of the bolus, continuously sampling the central portion of k-space, creating a plurality of central data sets;
• (i) interleaving the central data sets with the peripheral data sets;
• (j) reconstructing the interleaved central and peripheral data sets into a series of cine magnetic resonance angiographs.

A method of acquiring a three-dimensional magnetic resonance angiograph within a volume of interest, said method comprising:

• (a) determining a trigger point within the volume of interest for a three-dimensional magnetic resonance data acquisition;
• (b) administering an intravascular magnetic resonance contrast agent to a patient's circulatory system in such a manner as to enhance magnetic resonance imaging of blood vessels;
• (c) repeatedly acquiring spatially encoded magnetic resonance data from the volume of interest including a plurality of different magnetic resonance data views that span only a portion of k-space;
• (d) reconstructing a series of low resolution images from the magnetic resonance data views;
• (e) generating low resolution maximum intensity projections from the low resolution images;
• (f) from the maximum intensity projections detecting a rising edge of the bolus;
• (g) after detecting the rising edge of the bolus, performing a series of three-dimensional magnetic resonance acquisitions;
• and,
• (h) reconstructing data acquired during step (c) and step (g) into a three-dimensional magnetic resonance angiograph.

In a magnetic resonance angiography (MRA) system, a method of detecting the arrival of a bolus of magnetic resonance contrast-enhancing agent in a volume of interest, said method comprising:

• (a) continuously sampling a centrally encoded portion of k-space, generating a plurality of central data sets;
• (b) reconstructing the plurality of central data sets into a series of reduced resolution images;
• (c) generating a maximum intensity projection from at least a portion of each reduced resolution image;
• (d) comparing the generated maximum intensity projection to a predetermined projection threshold value;
• and
• (e) in response to the comparing step, one of (i) triggering the sampling of higher phase encode portions of k-space, and (ii) discarding the current central data set and repeating steps (a) through (d).

An MRA system for imaging a subject into which a magnetic resonance contrast-enhancing agent is infected, the system including a magnet for generating a temporally constant magnetic field through a volume of interest, a radio frequency transmitter for exciting and inverting magnetic dipoles in the volume of interest to generate a train of magnetic resonance echoes, and gradient magnetic field coils and a gradient magnetic field controller for generating at least phase and read magnetic field gradient pulses in orthogonal directions across the volume of interest, a receiver for receiving and demodulating the magnetic resonance echoes to produce a series of k-space views, the system further comprising:

• a central data memory portion for storing a plurality of centrally encoded k-space views;
• a peripheral data memory portion for storing higher phase encode views which are peripherally around the central phase encode views;
• a bolus detection processor for detecting an arrival of a leading edge of a bolus of the contrast-enhancing agent, the bolus detection processor including:
• a maximum intensity projection processor for processing at least a portion of the plurality of centrally encoded k-space views into maximum intensity projections of a portion of the volume of interest through which the bolus enters the volume of interest onto a line;
• and,
• an edge detector for detecting the arrival of the contrast-enhancing agent bolus from the maximum intensity projections;
• a reconstruction processor for reconstructing at least a portion of (i) the plurality of centrally encoded k-space views, and (ii) the higher phase encode views.