# US 11,906,607 B2 · Efficient self-refocusing zero echo time MR imaging > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,607 B2 - Document ID: US11906607B2 - Status: Granted - Kind: B2 - Application number: 17/609,527 - Filed: 2020-05-06 - Published: 2022-09-29 - Granted: 2024-02-20 - Earliest claimed: 2019-05-09 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Holger Eggers; Kay Nehrke; Peter Boernert - Web page: https://patentgrep.com/patent/US11906607B2 ## CPC - G01R 33/4826: {in three dimensions} - G01R 33/4816: {NMR imaging of samples with ultrashort relaxation times such as solid samples, e.g. MRI using ultrashort TE [UTE], single point imaging, constant time imaging} - G01R 33/543: {Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence)} - G01R 33/56518: {due to eddy currents, e.g. caused by switching of the gradient magnetic field} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract The invention relates to a method of MR imaging of an object positioned in an examination volume of a MR device (1). It is an object of the invention to enable efficient silent ZTE imaging with self-refocusing. The method of the invention comprises the steps of:—specification of a set of radial k-space spokes to cover a spherical k-space volume;—selection of subsets of a predetermined number of spokes from the specified set so that the concatenation of the spokes contained in each of the subsets forms a closed trajectory in k-space, wherein the selection of the subsets involves optimizing a cost function;—subjecting the object (10) to a zero echo time imaging sequence, wherein each of the subsets of spokes is acquired as a sequence of gradient echo signals; and—reconstructing an MR image from the acquired spokes. Moreover, the invention relates to a MR device and to a computer program for a MR device. ## Claims ### Claim 1 A computer-implemented method of magnetic resonance (MR) imaging of an object positioned in an examination volume of a MR device, the method comprising: specifying a set of radial k-space spokes to cover a spherical k-space volume, such that spokes of the set of radial k-space spokes extend from a k-space origin in the spherical k-space volume to end points distributed on a surface of the spherical k-space volume; automatically selecting subsets of spokes from the specified set of radial k-space spokes, with each subset comprising a predetermined number of spokes from the specified set of radial k-space spokes so that concatenation of the spokes in each of the subsets forms a closed trajectory in k-space, wherein selecting the subsets is based on optimizing a cost function favouring (i) minimizing a maximum angle between subsequently acquired spokes within the same subset, (ii) maximizing a uniformity of the distribution of the end points of the spokes on the surface of the spherical k-space volume, and penalizing a level of acoustic noise generated during acquisition of the subsets, while ensuring that the concatenation of the spokes of each of the subsets forms the closed trajectory in k-space; performing a zero echo time imaging sequence of the object, wherein each of the subsets is acquired as a sequence of gradient echo signals; reconstructing an MR image from the acquired spokes; and providing a human-readalbe display of reconstructed MR image. ### Claim 2 A computer-implemented method of magnetic resonance (MR) imaging of an object positioned in an examination volume of a MR device, the method comprising: specifying a set of radial k-space spokes to cover a spherical k-space volume, such that spokes of the set of radial k-space spokes extend from a k-space origin in the spherical k-space volume to end points distributed on a surface of the spherical k-space volume; automatically selecting subsets of spokes from the specified set of radial k-space spokes, with each subset comprising a predetermined number of spokes from the specified set of radial k-space spokes so that concatenation of the spokes in each of the subsets forms a closed trajectory in k-space, wherein selecting the subsets involves determining a sequence in which the spokes in each of the subsets are acquired, and wherein selecting the subsets is based on optimizing a cost function favouring (i) minimizing a maximum angle between subsequently acquired spokes within the same subset, and (ii) maximizing a uniformity of the distribution of the end points of the spokes on the surface of the spherical k-space volume, while ensuring that the concatenation of the spokes of each of the subsets forms the closed trajectory in k-space; performing a zero echo time imaging sequence of the object, wherein each of the subsets is acquired as a sequence of gradient echo signals; reconstructing an MR image from the acquired spokes; and providing a human-readable display of reconstructed MR image. ### Claim 3 A computer-implemented method of magnetic resonance (MR) imaging of an object positioned in an examination volume of a MR device, the method comprising: specifying a set of radial k-space spokes to cover a spherical k-space volume, wherein the set of radial k-space spokes consists of pairs of spokes having anti-parallel orientations; automatically selecting subsets of spokes from the specified set of radial k-space spokes, with each subset comprising a predetermined number of spokes from the specified set of radial k-space spokes so that concatenation of the spokes in each of the subsets forms a closed trajectory in k-space, wherein selecting the subsets is based on optimizing a cost function favouring (i) minimizing a maximum angle between subsequently acquired spokes within the same subset, and (ii) maximizing a uniformity of distribution of end points of the spokes on a surface of the spherical k-space volume, while ensuring that the concatenation of the spokes of each of the subsets forms the closed trajectory in k-space; performing a zero echo time imaging sequence of the object, wherein each of the subsets is acquired as a sequence of gradient echo signals; reconstructing an MR image from the acquired spokes; and providing a human-readable display of reconstructed MR image. ### Claim 4 A magnetic resonance (MR) device comprising: at least one main magnet coil for generating a uniform, static magnetic field within an examination volume; a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume; at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from an object positioned in the examination volume; a control unit for controlling a temporal succession of RF pulses and switched magnetic field gradients, wherein the control unit is configured to: specify a set of radial k-space spokes to cover a spherical k-space volume, such that spokes of the set of radial k-space spokes are between a k-space origin and end points distributed on a surface of the spherical k-space volume; select subsets of a predetermined number of spokes from the specified set radial k-space spokes so that concatenation of the spokes in each of the subsets forms a closed trajectory in k-space, wherein selecting the subsets is based on a cost function is based on optimizing a cost function favouring (i) minimizing a maximum angle between subsequently acquired spokes within the same subset, (ii) maximizing the uniformity of the distribution of the end points of the spokes on the surface of the spherical k-space volume, while ensuring that the concatenation of the spokes of the subsets forms the closed trajectory in k-space; and perform a zero echo time imaging sequence of the object, wherein each of the subsets is acquired as a sequence of gradient echo signals; a reconstruction unit configured to reconstruct an MR image from the acquired spokes; and a video monitor configured to provide a human-readable display of the reconstructed MR image. ### Claim 5 A non-transitory computer readable medium storing instructions that, when executed by at least one computer, cause the at least one computer to: specify a set of radial k-space spokes to cover a spherical k-space volume, such that spokes of the set of radial k-space spokes are between a k-space origin and end points distributed on a surface of the spherical k-space volume; select subsets of a predetermined number of spokes from the specified set of radial k-space spokes so that concatenation of the spokes contained in each of the subsets forms a closed trajectory in k-space, wherein selecting the subsets is based on a cost function favouring (i) minimizing a maximum angle between subsequently acquired spokes within the same_subset, (ii) maximizing a uniformity of the distribution of the end points of the spokes on the surface of the spherical k-space volume, while ensuring that the concatenation of the spokes of each of the subsets forms the closed trajectory in k-space; generate a zero echo time imaging sequence, wherein each of the subsets is acquired as a sequence of gradient echo signals; reconstruct an MR image from the acquired spokes; and cause the reconstructed MR image to be displayed on a video monitor. ### Claim 6 (depends on 2) The method of claim 2, wherein the cost function depends on relative orientations of the subsequently acquired spokes within the same subset. ### Claim 7 (depends on 3) The method of claim 3, wherein each of the subsets is selected to consist of at least one pair of spokes having anti-parallel orientations. ### Claim 8 (depends on 1) The method of claim 1, wherein a greedy selection strategy is used in a sequential selection of the subsets. ### Claim 9 (depends on 1) The method of claim 1, wherein a greedy selection strategy is used in a sequential selection of individual spokes or pairs of spokes for each of the subsets. ### Claim 10 (depends on 4) The MR device of claim 4, wherein the control unit is configured to select the subsets further based on determining a sequence in which the spokes contained in each of the subsets are acquired. ### Claim 11 (depends on 4) The MR device of claim 4, wherein the cost function penalizes a level of acoustic noise generated during acquisition of the subsets of spokes. ### Claim 12 (depends on 4) The MR device of claim 4, wherein the set of radial k-space spokes consists of pairs of spokes having anti-parallel orientations. ### Claim 13 (depends on 4) The MR device of claim 4, wherein a greedy selection strategy is used in a sequential selection of individual subsets of spokes or a sequential selection of individual or pairs of spokes for each of the subsets. ### Claim 14 (depends on 5) The computer readable medium of claim 5, wherein selecting the subsets involves determining a sequence in which the spokes in each of the subsets are acquired. ### Claim 15 (depends on 14) The computer readable medium of claim 14, wherein the cost function depends on the relative orientations of subsequently acquired spokes from the same subset. ### Claim 16 (depends on 5) The computer readable medium of claim 5, wherein the cost function penalizes a level of acoustic noise generated during acquisition of the subsets of spokes. ### Claim 17 (depends on 5) The computer readable medium of claim 5, wherein the set of radial k-space spokes consists of pairs of spokes having anti-parallel orientations. ### Claim 18 (depends on 17) The computer readable medium of claim 17, wherein each of the subsets is selected to consist of at least one pair of spokes having anti-parallel orientations. ### Claim 19 (depends on 5) The computer readable medium of claim 5, wherein the instructions cause the at least one computer to use a greedy selection strategy in a sequential selection of the subsets of spokes. ### Claim 20 (depends on 5) The computer readable medium of claim 5, wherein the instructions cause the at least one computer to use a greedy selection strategy in a sequential selection of individual or pairs of spokes for each of the subsets.