EP0318212A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Magnetic resonance imaging methods and apparatus
Assignee: Philips Nuclear Medicine Inc
•
Filing: 1988-11-18
•
Granted: —
•
Expires: 2008-11-18
Abstract
Abstract A magnetic resonance imaging method and apparatus wherein a spin echo (52) and a gradient echo (60) are generated in each magnetic resonance sequence repetition. The spin echo is phase encoded by a phase encode gradient (44) in regular steps spanning about a quarter of k-space. More particularly, steps from -n to G max /2, where n is a small integer and G max is the maximum phase encode gradient. An off-set phase encode gradient (58) shifts the phase encoding of the gradient echo by G max /2 relative to the first phase encoding gradient. Data to fill the empty portions of k-space (142, 267) between -n and-G max are generated from the complex conjugate (140, 160), of the first echo data (74) and the second echo data (76). The first and second echo data and the complex conjugate data are transformed (122, 132, 146, 166) to generate parted image representations (124, 134, 148 168). The first echo image representation and the corresponding conjugately symmetric image representation are phase correction (126, 150) in accordance with a phase map (112) derived from the central most first echo data (78). The partial image representations are summed (170) to produce a resultant image representation (172).
Inventors
- 👤 G.Neil Holland
- 👤 Terrence J. Provost
- 👤 Gordon D. Demeester
- 👤 Kenneth S. Denison
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 14:44
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/48; G01R33/54; G01R33/56; G01R33/561; G01R33/5602
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
285 words
A magnetic resonance imaging method comprising: (a) exciting magnetic resonance; (b) phase encoding the magnetic resonance; (c) inducing a first echo (52); (d) applying a read gradient pulse (54) of a first polarity during the first echo (52) and acquiring a first echo view; (e) changing the phase encoding; (f) applying a read gradient pulse (56) of a second polarity to induce at least a second echo (60); (g) acquiring a second echo view during the second echo (60); (h) repeating steps (a) to (g) with different phase encodings until first and second echo views (74 or F s (k x , k y ), 76 or F g (k x , k y )) comprising a set of views neighboring a centrally phase encoded view and half of the remaining phase encodable views are acquired; (i) generating a phase map (φ(x,y)) from the views (78) neighboring the centrally phase encoded view: (j) generating complex conjugately symmetric views (F s *(k x , k y ), F g * (k x , k y )) from the acquired views (74 or F s (k x , k y ), (76 or F g (k x , k y )); (k) Fourier transforming the first echo (74 or F s (k x , k y )), second echo (76 or F g (k x , k y )), and conjugately symmetric views (F s *(k x , k y ), F g *(k x , k y )); (1) phase correcting at least some of the Fourier transformed views (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y)) in accordance with the phase map and φ(x,y); (m) combining the Fourier transformed views (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y)) produce an image representation (f(x,y)).
Claim 2
Dependent Claim
285 words
A magnetic resonance imaging method comprising: (a) exciting magnetic resonance; (b) phase encoding the magnetic resonance; (c) inducing a first echo (52); (d) applying a read gradient pulse (54) of a first polarity during the first echo (52) and acquiring a first echo view; (e) changing the phase encoding; (f) applying a read gradient pulse (56) of a second polarity to induce at least a second echo (60); (g) acquiring a second echo view during the second echo (60); (h) repeating steps (a) to (g) with different phase encodings until first and second echo views (74 or F s (k x , k y ), 76 or F g (k x , k y )) comprising a set of views neighboring a centrally phase encoded view and half of the remaining phase encodable views are acquired; (i) generating a phase map (φ(x,y)) from the views (78) neighboring the centrally phase encoded view: (j) generating complex conjugately symmetric views (F s *(k x , k y ), F g * (k x , k y )) from the acquired views (74 or F s (k x , k y ), (76 or F g (k x , k y )); (k) Fourier transforming the first echo (74 or F s (k x , k y )), second echo (76 or F g (k x , k y )), and conjugately symmetric views (F s *(k x , k y ), F g *(k x , k y )); (1) phase correcting at least some of the Fourier transformed views (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y)) in accordance with the phase map and φ(x,y); (m) combining the Fourier transformed views (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y)) produce an image representation (f(x,y)).
Claim 3
Dependent Claim
15 words
A method according to Claim 1 wherein the first echo (52) is a spin echo.
Claim 4
Dependent Claim
18 words
A method according to Claim 1 or Claim 2 wherein the second echo (60) is a gradient echo.
Claim 5
Dependent Claim
82 words
A method according to Claim 1 or Claim 2 or Claim 3 wherein the first echo views (74 or F s (k x , k y ) are phase encoded with phase encoding gradients from neighboring zero phase encode (-n) to substantially one half of maximum phase encode (G max ) and wherein in step (e) the phase encoding (G max ), whereby redundant first and second echo views (n) are acquired adjacent one half of the maximum gradient (G max )
Claim 6
Independent Claim
41 words
A method according to any one of the preceding claims further including aligning and normalizing the first (74 or F s (k x , k y ) and second (76 or F g (k x , k y )) echo views.
Claim 7
Independent Claim
31 words
A method according to any one of the preceding claims wherein the phase correcting step is performed on the Fourier transformed first echo and first echo conjugately symmetric views (f₁(x,y), f₃(x,y)).
Claim 8
Dependent Claim
210 words
A magnetic resonance imaging method comprising; (a) exciting magnetic resonance; (b) inducing a first echo (52) with a first phase encoding; (c) inducing at least one subsequent echo (60) each with one other phase encoding; (d) sampling the first echo (52) to acquire a first view and each subsequent echo (60) to acquire subsequent views; (e) repeating steps (a) to (d) with a plurality of phase encodings until first and subsequent echo views (74 or F s (k x , k y ), 76 or F g (k x , k y )) which span about a half of k-space are acquired; (f) generating complex conjugate views (F s *(k x , k y ), F g *(k x , k y )) which span about half of k-space from the acquired first and subsequent echo views and (74 or F s (k x , k y ), 76 or F g (k x , k y )); (g) creating an image representation f(x,y) from the first echo (74 or F s (k x , k y )), subsequent echo (76 or F g (k x , k y )), and complex conjugate views (F s *(k x , k y ), F g (k x , k y )).
Claim 9
Dependent Claim
210 words
A magnetic resonance imaging method comprising; (a) exciting magnetic resonance; (b) inducing a first echo (52) with a first phase encoding; (c) inducing at least one subsequent echo (60) each with one other phase encoding; (d) sampling the first echo (52) to acquire a first view and each subsequent echo (60) to acquire subsequent views; (e) repeating steps (a) to (d) with a plurality of phase encodings until first and subsequent echo views (74 or F s (k x , k y ), 76 or F g (k x , k y )) which span about a half of k-space are acquired; (f) generating complex conjugate views (F s *(k x , k y ), F g *(k x , k y )) which span about half of k-space from the acquired first and subsequent echo views and (74 or F s (k x , k y ), 76 or F g (k x , k y )); (g) creating an image representation f(x,y) from the first echo (74 or F s (k x , k y )), subsequent echo (76 or F g (k x , k y )), and complex conjugate views (F s *(k x , k y ), F g (k x , k y )).
Claim 10
Dependent Claim
33 words
A method according to Claim 7 further including after inducing the first echo (52), changing the phase encoding by a phase encoding that corresponds to substantially one quarter of k-space (G max /2).
Claim 11
Dependent Claim
30 words
A method according to Claim 7 or Claim 8 further including phase correcting at least portions (f₁(x,y), f₃(x,y)) of the image representation (f(x,y)) corresponding to a central portion of k-space.
Claim 12
Dependent Claim
35 words
A method according to Claim 9 wherein the phase correction is done in accordance with a phase map (φ(x,y)) generated from first echo views (78) phase encoded with phase encoding neighboring a center of k-space.
Claim 13
Independent Claim
29 words
A method according to any one of Claims 7 to 10 wherein each first echo (52) is a spin echo and each subsequent echo (60) is a gradient echo.
Claim 14
Independent Claim
57 words
A method according to any one of Claims 7 to 11 wherein a first polarity read gradient (54) is applied concurrently with each first echo (52) and wherein each subsequent echo (60) is induced by reversing the polarity of the read gradient (54) to cause an opposite polarity read gradient (56) concurrently with the subsequent echo (60).
Claim 15
Independent Claim
94 words
A method according to any one of Claims 7 to 12 wherein the first echoes (52) are phase encoded with phase encoding gradients in steps from n steps on one side of the zero phase encode gradient to half way to a maximum phase encode gradient (G max ) on the other side of the zero phase encode gradient and wherein the subsequent echoes (60) are phase encoded in steps from half the maximum phase encode gradient (G max minus n to the maximum encode gradient (G max ), where n is an integer.
Claim 16
Independent Claim
66 words
A method according to any one of Claims 7 to 13 further including filtering the first (74 or F s (k x , k y )) and 76 or F g (k x , k y )) echo views corresponding to the steps between half the subsequent maximum phase encode gradient and half the maximum phase encode gradient minus n with complementary roll-off filters (120, 130).
Claim 17
Dependent Claim
234 words
A magnetic resonance imaging method comprising: collecting first echo views (74 or F s (k x , k y )) representing a fraction of substantially a quarter of k-space adjacent a zero phase encoding; collecting second echo views (76 or F g (k x , k y )) each of whose phase encode is shifted from the phase encode of the corresponding one of the first echo views (74 or F s (k x , k y )) by said fraction of k-space; generating complex conjugate views (F s *(k x , k y )) to the first echo views (74 or F s (k x )); generating complex conmjugate views (F g *(k x . k y )) to the second echo views (76 or F g (k x , k y )); Fourier transforming the first echo views (74 or F s (k x , k y )), the second echo views (76 or F g (k y , k y )), the complex conjugate first echo views (F s *(k x , k y )), and the complex conjugate second echo views (F g *(k x , k y )) to generate an image representation (f(x,y)); and adjusting a phase of at least the transformed first echo (74 or F s (k x , k y )) and complex conjugate first echo (F s *(k x , k y )) views.
Claim 18
Dependent Claim
234 words
A magnetic resonance imaging method comprising: collecting first echo views (74 or F s (k x , k y )) representing a fraction of substantially a quarter of k-space adjacent a zero phase encoding; collecting second echo views (76 or F g (k x , k y )) each of whose phase encode is shifted from the phase encode of the corresponding one of the first echo views (74 or F s (k x , k y )) by said fraction of k-space; generating complex conjugate views (F s *(k x , k y )) to the first echo views (74 or F s (k x )); generating complex conmjugate views (F g *(k x . k y )) to the second echo views (76 or F g (k x , k y )); Fourier transforming the first echo views (74 or F s (k x , k y )), the second echo views (76 or F g (k y , k y )), the complex conjugate first echo views (F s *(k x , k y )), and the complex conjugate second echo views (F g *(k x , k y )) to generate an image representation (f(x,y)); and adjusting a phase of at least the transformed first echo (74 or F s (k x , k y )) and complex conjugate first echo (F s *(k x , k y )) views.
Claim 19
Dependent Claim
106 words
A method according to Claim 15 wherein the first echo views (74 or F s (k x , k y )) are phase encoded in regular steps from n steps on one side of a zero phase encode gradient to substantially half way to a maximum phase encode gradient (G max ) on the other side of the zero phase encode gradient and wherein the second echo views (76 or F s (k x , k y )) are phase encoded in regular steps from n steps below half the maximum phase encode gradient (G max ) to the maximum phase encode gradient (G max ).
Claim 20
Dependent Claim
44 words
A method according to Claim 15 or Claim 16 or Claim 17 wherein the steps of collecting first and second echo views include deriving a phase map (φ(x,y)) from the views (78) encoded in 2n steps most closely adjacent the zero phase encode gradient.
Claim 21
Dependent Claim
317 words
A magnetic resonance imaging apparatus comprising: a main magnetic field means (10,12) for inducing a generally linear main magnetic field through an image region; a radio frequency transmitting means (30, 32) for transmitting radio frequency pulses into the image region for selectively inducing magnetic resonance and for selectively causing the formation of a magnetic resonance echo; a gradient field means (20, 22) for causing magnetic field gradients across the image region, the magnetic field gradients including phase encode gradients varying in regular steps , a phase encode off-set gradient, and a read gradient; and a receiving means (32, 34) for receiving magnetic resonance signals from the image region and producing corresponding views, characterised in that said apparatus includes: a first echo image memory means (80) for storing views (74 or F s (k x , k y )) received during a first echo (52) in each sequence; a second echo image memory means (82) for storing views (76 or F g (k x , k y )) received during a second echo (60) in each sequence; an aligning means (84) for aligning views in the first (80) and second (82) echo memories; a conjugate symmetry means (140, 160) for generating conjugate symmetry views (F s *(k x , k y ), F g *(k x , k y )) which are conjugately symmetric to the first echo views (74 or F s (k x , k y )) and the second echo views (76 or F g (k x or k y )) and a transform means (122, 312, 146, 166) for transforming the first echo (74 or F s (k x , k y )), the second echo (76 or F g (k x , k y )), and the conjugately symmetric (F s *(k x , k y ), F g *(k x , k y )) views into image representations (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y).
Claim 22
Dependent Claim
317 words
A magnetic resonance imaging apparatus comprising: a main magnetic field means (10,12) for inducing a generally linear main magnetic field through an image region; a radio frequency transmitting means (30, 32) for transmitting radio frequency pulses into the image region for selectively inducing magnetic resonance and for selectively causing the formation of a magnetic resonance echo; a gradient field means (20, 22) for causing magnetic field gradients across the image region, the magnetic field gradients including phase encode gradients varying in regular steps , a phase encode off-set gradient, and a read gradient; and a receiving means (32, 34) for receiving magnetic resonance signals from the image region and producing corresponding views, characterised in that said apparatus includes: a first echo image memory means (80) for storing views (74 or F s (k x , k y )) received during a first echo (52) in each sequence; a second echo image memory means (82) for storing views (76 or F g (k x , k y )) received during a second echo (60) in each sequence; an aligning means (84) for aligning views in the first (80) and second (82) echo memories; a conjugate symmetry means (140, 160) for generating conjugate symmetry views (F s *(k x , k y ), F g *(k x , k y )) which are conjugately symmetric to the first echo views (74 or F s (k x , k y )) and the second echo views (76 or F g (k x or k y )) and a transform means (122, 312, 146, 166) for transforming the first echo (74 or F s (k x , k y )), the second echo (76 or F g (k x , k y )), and the conjugately symmetric (F s *(k x , k y ), F g *(k x , k y )) views into image representations (f₁(x,y), f₂(x,y), f₃(x,y), f₄(x,y).
Claim 23
Dependent Claim
94 words
An apparatus according to Claim 20 further including: a phase correction means (100) for determining appropriate phase correction from at least the first echo views (74 or F s (k x , k y )); and a phase correction means (126, 150) for correcting the first echo views (74 or F s (k x , k y )) and the conjugately symmetric views (F s *(k x , k y )) corresponding to the first echo views (74 or F s (k x , k y )) in accordance with the determined phase correction.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.