# US 8,571,631 B2 · Method for contrast-agent-free angiographic imaging in magnetic resonance tomography

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- Number: US 8,571,631 B2
- Document ID: US8571631B2
- Status: Granted
- Kind: B2
- Application number: 12/645,858
- Filed: 2009-12-23
- Published: 2010-06-24
- Granted: 2013-10-29
- Earliest claimed: 2008-12-23
- Assignees: Siemens Aktiengesellschaft
- Applicants: Michael Deimling
- Inventors: Michael Deimling
- Web page: https://patentgrep.com/patent/US8571631B2

## CPC

- G01R 33/5635: {Angiography, e.g. contrast-enhanced angiography [CE-MRA] or time-of-flight angiography [TOF-MRA]}
- G01R 33/5613: {Generating steady state signals, e.g. low flip angle sequences [FLASH]}
- G01R 33/5614: {using a fully balanced steady-state free precession [bSSFP] pulse sequence, e.g. trueFISP}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A method for contrast-agent-free non-triggered angiographic imaging in magnetic resonance tomography that includes the steps of (S1) 2D or 3D measurement of a bodily region having a flow of blood, using a flow-insensitive SSFP sequence, (S2) measurement of the same bodily region using a flow-sensitive SSFP sequence, (S3) registration of the measurement results obtained in steps S1 and S2 to one another, (S4) unweighted or self-weighted subtraction of the registered measurement result obtained in step S2from the registered measurement result obtained in step S1, (S5) execution of a 2D or 3D image correction of the image obtained in step S4by removing image distortions caused by gradient field inhomogeneities and/or magnetic basic field inhomogeneities, and (S6) representation of the angiogram obtained in step S5 in the form of an MIP or segmented 2D or 3D vessel tree representation.

## Claims

### Claim 1

A method for contrast agent-free, non-triggered angiographic imaging in magnetic resonance tomography, comprising the steps of:
(S1) operating a magnetic resonance tomography apparatus to acquire a dataset, selected from the group consisting of a two-dimensional (2D) dataset and a three-dimensional (3D) dataset, of magnetic resonance data from a body region of an examination subject having blood flowing therein, using a flow-insensitive steady state free precession (SSFP) magnetic resonance data acquisition sequence selected from the group consisting of trueFISP (wherein FISP is a fast imaging with steady state precession sequence), and phase-cycled SSFP sequences;
(S2) acquiring a dataset, selected from the group consisting of a 2D dataset and a 3D dataset, of magnetic resonance data from said body region using a FISP sequence as a flow-sensitive SSFP sequence;
(S3) bringing said dataset acquired in (S1) into registration with the dataset acquired in (S2), thereby obtaining a registered dataset from (S1) and a registered dataset from (S2);
(S4) subtracting said registered dataset from (S2) from the registered dataset from (S1) by unweighted or self-weighted subtraction;
(S5) subjecting a dataset resulting from the subtraction in (S4) to image correction by removing image distortions caused by gradient field inhomogeneities or basic magnetic field inhomogeneities, to obtain a corrected dataset; and
(S6) generating an angiographic image from the corrected dataset from (S5) in a representation selected from the group consisting of a maximum intensity projection (MIP) and a segmented vessel tree.

### Claim 2 (depends on 1)

A method as claimed in claim 1 comprising employing a constructive interference steady state (CISS) sequence as said flow-insensitive SSFP magnetic resonance data acquisition sequence.

### Claim 3 (depends on 1)

A method as claimed in claim 1 comprising, in each of said flow-insensitive SSFP sequence and said flow-sensitive SSFP sequence, radiating radio frequency pulses with a flip angle that maximizes a resulting SSFP signal.

### Claim 4 (depends on 1)

A method as claimed in claim 1 comprising using identical geometric magnetic resonance tomography parameters in each of said flow-sensitive SSFP sequence and said flow-insensitive SSFP sequence.

### Claim 5 (depends on 1)

A method as claimed in claim 1 comprising varying said flow-sensitive SSFP sequence in a direction selected from the group consisting of the readout direction and the slice-selection direction, by generating a matched spoiler gradient in said direction upon each repetition of said flow-sensitive SSFP sequence.