Selective imaging among three or more chemical species

Claim 1

A method for producing an image of a first chemical species in the presence of a second and third chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species and the third chemical species having a chemical shift frequency difference of Δω 1 ,3 with respect to the first chemical species, both in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) identifying frequencies ω a and ω b approximating frequency difference Δω 1 ,2 and Δω 1 ,3 and so that the ratio ω a :ω b equals a ratio of two odd integers i a and i b ; b) determining an evolution time τ being equal to ##EQU10## c) acquiring a first complex NMR image with an evolution time of kτ, where k is an even integer including zero, in which a relative phase of the three species is equal; d) acquiring a second complex NMR image with an evolution time of 1τ, where 1 is an odd integer, so that the second and third species have a phase difference magnitude of π; and e) combining the first and second images to produce a chemical species image with reduced contribution from the second and third species.

Claim 2

A method for producing an image of a first chemical species in the presence of a second and third chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species and the third chemical species having a chemical shift frequency difference of Δω 1 ,3 with respect to the first chemical species, both in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) identifying frequencies ω a and ω b approximating frequency difference Δω 1 ,2 and Δω 1 ,3 and so that the ratio ω a :ω b equals a ratio of two odd integers i a and i b ; b) determining an evolution time τ being equal to ##EQU10## c) acquiring a first complex NMR image with an evolution time of kτ, where k is an even integer including zero, in which a relative phase of the three species is equal; d) acquiring a second complex NMR image with an evolution time of 1τ, where 1 is an odd integer, so that the second and third species have a phase difference magnitude of π; and e) combining the first and second images to produce a chemical species image with reduced contribution from the second and third species.

Claim 9

A method for producing an image having reduced contribution from a first chemical species in the presence of a second and third chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species and the third chemical species having a chemical shift frequency difference of Δω 1 ,3 with respect to the first chemical species, both in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) identifying frequencies ω a and ω b approximating frequency differences Δω 1 ,2 and Δω 1 ,3 and so that the ratio ω a :ω b equals a ratio of two odd integers i a and i b ; b) determining an evolution time τ being equal to ##EQU15## c) acquiring a first complex NMR image with an evolution time of kτ, where k is an even integer including zero, in which a relative phase of the three species is equal; d) acquiring a second complex NMR image with an evolution time of lτ, where l is an odd integer, so that the second and third species have a phase difference magnitude of π; and e) combining the first and second images to produce a chemical species image with reduced contribution from the first chemical species.

Claim 10

A method for producing an image having reduced contribution from a first chemical species in the presence of a second and third chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species and the third chemical species having a chemical shift frequency difference of Δω 1 ,3 with respect to the first chemical species, both in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) identifying frequencies ω a and ω b approximating frequency differences Δω 1 ,2 and Δω 1 ,3 and so that the ratio ω a :ω b equals a ratio of two odd integers i a and i b ; b) determining an evolution time τ being equal to ##EQU15## c) acquiring a first complex NMR image with an evolution time of kτ, where k is an even integer including zero, in which a relative phase of the three species is equal; d) acquiring a second complex NMR image with an evolution time of lτ, where l is an odd integer, so that the second and third species have a phase difference magnitude of π; and e) combining the first and second images to produce a chemical species image with reduced contribution from the first chemical species.

Claim 17

A method for examining silicone prostheses for failure, in vivo, employing magnetic resonance imaging equipment using a polarizing field of B 0 , comprising the steps of: a) acquiring a first complex NMR image of the prostheses and surrounding tissue with a pulse having an evolution time of zero in which the relative phase of protons of water, fat, and silicone are equal; b) acquiring a second complex NMR image of the prostheses and surrounding tissue with an evolution time τ of substantially ##EQU20## and c) combining the first and second images to produce an image of the silicone (ρ 3 ) of the prostheses with reduced contribution from fat and water (ρ 1 +ρ 2 ).

Claim 18

A method for examining silicone prostheses for failure, in vivo, employing magnetic resonance imaging equipment using a polarizing field of B 0 , comprising the steps of: a) acquiring a first complex NMR image of the prostheses and surrounding tissue with a pulse having an evolution time of zero in which the relative phase of protons of water, fat, and silicone are equal; b) acquiring a second complex NMR image of the prostheses and surrounding tissue with an evolution time τ of substantially ##EQU20## and c) combining the first and second images to produce an image of the silicone (ρ 3 ) of the prostheses with reduced contribution from fat and water (ρ 1 +ρ 2 ).

Claim 20

A method for producing an image having reduced contribution from a first chemical species in the presence of at least a second chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) acquiring a first complex NMR image with an evolution time in which a relative phase of the two species is equal; b) acquiring a second complex NMR image with an evolution time of τ so that the second species has a phase difference magnitude of π with respect to the first species; and c) acquiring a third complex NMR image with an evolution time of 2τ in which a relative phase of the two species is equal; and d) combining the third image with the second image to produce the chemical species image ρ 3 with reduced contribution from the second species according to the following equation: ρ.sub.3 =(S".sub.2π +sS".sub.π)/2 where S".sub.π, S∝ 2 π are the second and third complex NMR images, and s is a switch function resolving ambiguity in the sign of the second complex NMR image; wherein chemical species with short relaxation times may be imaged.

Claim 21

A method for producing an image having reduced contribution from a first chemical species in the presence of at least a second chemical species, the second species having a chemical shift frequency difference of Δω 1 ,2 with respect to the first chemical species in the presence of a polarizing magnetic field B 0 , the method comprising the steps of: a) acquiring a first complex NMR image with an evolution time in which a relative phase of the two species is equal; b) acquiring a second complex NMR image with an evolution time of τ so that the second species has a phase difference magnitude of π with respect to the first species; and c) acquiring a third complex NMR image with an evolution time of 2τ in which a relative phase of the two species is equal; and d) combining the third image with the second image to produce the chemical species image ρ 3 with reduced contribution from the second species according to the following equation: ρ.sub.3 =(S".sub.2π +sS".sub.π)/2 where S".sub.π, S∝ 2 π are the second and third complex NMR images, and s is a switch function resolving ambiguity in the sign of the second complex NMR image; wherein chemical species with short relaxation times may be imaged.