Determination of T1 relaxation times used in automated nuclear magnetic resonance image synthesis

Claim 1

A method for determining the spin-lattice relaxation time T1 of an image during a Nuclear Magnetic Resonance (NMR) measurement technique on a human body comprising the steps of: subjecting said body to magnetic fields in accordance with a NMR technique using a multiple spin-echo pulse sequence at two different predetermined stored pulse repetition times TR1 and TR2; measuring a first signal S(TR1) at a first one of (TR1) of said two repetition times including the steps of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a first period of time equal to a first pulse repetition time TR1, and then flipping the longitudinal magnetization Mz by 90° into the x-y plane wherein the value of x-y plane magnetization immediately after the step of flipping is said first signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said first signal S(TR1) is expressed by a first equation S(TR1)=M 0 [1-exp (-TR1/T1)] where M 0 is a constant; measuring a second signal at a second one TR2 of said two repetition times including the step of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a second period of time equal to said second pulse repetition time TR2, and then flipping the longitudinal magnetization by 90° into the x-y plane, wherein the value of the x-y plane magnetization immediately after the step of flipping is said second signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said measured second signal S(TR2) is expressed by a second equation S(TR2)=M 0 [1-exp (TR1/T1)]; storing the value of said measured first and second signals; allowing said first and second measured signals to decay away at a characteristic time T2 and measuring said decaying signal at a plurality of echo times TE(i) i=1, . . . , N wherein said echo times are associated with 180° flips each associated with one of a multiple of spin-echos in said multiple spin-echo pulse sequence; storing said measured decaying signal values at each of said echo times TE(i) for each of said first and second pulse repetition times TR1, TR2; forming a first ratio R of said first to said second measured values; solving a third equation R=[1-exp (TR1/T1)]/[1-exp (-TR2/T1)] for an initial T1 value by using the stored values of said first ratio R and said pulse repetition times TR1 and TR2; forming a plurality of secondary ratios R 1 . . . , R N of said measured decaying signal values at each of said echo times TE(i) i=1 . . . , N for said first repetition time to said measured decaying signal values at each of said echo times TE(i) i=1 . . . , N for said second repetition time, respectively; solving said third equation for a plurality of T1(i) i=1 . . . , N values using said plurality of secondary ratios R 1 . . . R N ; and finding the average value of at least said plurality of T1(i) i=1 . . . , N values.

Claim 2

A method for determining the spin-lattice relaxation time T1 of an image during a Nuclear Magnetic Resonance (NMR) measurement technique on a human body comprising the steps of: subjecting said body to magnetic fields in accordance with a NMR technique using a multiple spin-echo pulse sequence at two different predetermined stored pulse repetition times TR1 and TR2; measuring a first signal S(TR1) at a first one of (TR1) of said two repetition times including the steps of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a first period of time equal to a first pulse repetition time TR1, and then flipping the longitudinal magnetization Mz by 90° into the x-y plane wherein the value of x-y plane magnetization immediately after the step of flipping is said first signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said first signal S(TR1) is expressed by a first equation S(TR1)=M 0 [1-exp (-TR1/T1)] where M 0 is a constant; measuring a second signal at a second one TR2 of said two repetition times including the step of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a second period of time equal to said second pulse repetition time TR2, and then flipping the longitudinal magnetization by 90° into the x-y plane, wherein the value of the x-y plane magnetization immediately after the step of flipping is said second signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said measured second signal S(TR2) is expressed by a second equation S(TR2)=M 0 [1-exp (TR1/T1)]; storing the value of said measured first and second signals; allowing said first and second measured signals to decay away at a characteristic time T2 and measuring said decaying signal at a plurality of echo times TE(i) i=1, . . . , N wherein said echo times are associated with 180° flips each associated with one of a multiple of spin-echos in said multiple spin-echo pulse sequence; storing said measured decaying signal values at each of said echo times TE(i) for each of said first and second pulse repetition times TR1, TR2; forming a first ratio R of said first to said second measured values; solving a third equation R=[1-exp (TR1/T1)]/[1-exp (-TR2/T1)] for an initial T1 value by using the stored values of said first ratio R and said pulse repetition times TR1 and TR2; forming a plurality of secondary ratios R 1 . . . , R N of said measured decaying signal values at each of said echo times TE(i) i=1 . . . , N for said first repetition time to said measured decaying signal values at each of said echo times TE(i) i=1 . . . , N for said second repetition time, respectively; solving said third equation for a plurality of T1(i) i=1 . . . , N values using said plurality of secondary ratios R 1 . . . R N ; and finding the average value of at least said plurality of T1(i) i=1 . . . , N values.

Claim 8

A method for determining the spin-lattice relaxation time T1 of an image during a Nuclear Magnetic Resonance (NMR) measurement technique on a human body comprising the steps of: subjecting said body to magnetic fields in accordance with a NMR technique using a multiple spin-echo pulse sequence at two different predetermined stored pulse repetition times TR1 and TR2; measuring a first signal S(TR1) at a first one of (TR1) of said two repetition times including the steps of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a first period of time equal to a first pulse repetition time TR1, and then flipping the longitudinal magnetization Mz by 90° into the x-y plane wherein the value of x-y plane magnetization immediately after the step of flipping is said first signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said first signal S(TR1) is expressed by a first equation S(TR1)=M 0 [1-exp (-TR1/T1)] where M 0 is a constant; measuring a second signal at a second one TR2 of said two repetition times including the step of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a second period of time equal to said second pulse repetition time TR2, and then flipping the longitudinal magnetization by 90° into the x-y plane, wherein the value of the x-y plane magnetization immediately after the step of flipping is said second signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said measured second signal S(TR2) is expressed by a second equation S(TR2)=M 0 [1-exp (TR1/T1)]; storing the value of said measured first and second signals; allowing said first and second measured signals to decay away at a characteristic time T2 and measuring said decaying signal at a plurality of echo times TE(i) i=1, . . . , N wherein said echo times are associated with 180° flips each associated with one of a multiple of spin-echos in said multiple spin-echo pulse sequence; storing said measured decaying signal values at each of said echo times TE(i) for each of said first and second pulse repetition times TR1, TR2; subjecting at each of said two different predetermined stored pulse repetition times TR1 and TR2 said measured decaying signal values at each of said echo-time to a regression which provides estimates of pseudo-density (P) and the spin-spin relaxation time (T2); calculating a synthetic spin-echo P exp (-TE/T2) where TE is an arbitrary operator specified value for each of TR1 and TR2; forming a ratio of said synthetic spin-echo of said first repetition time to said synthetic spin-echo of said second repetition time; solving a third equation R=[1-exp (TR1/T1)]/[1-exp(-TR2/T1)] for a T1 value by using the values of said first ratio R and said pulse repetition times TR1 and TR2.

Claim 9

A method for determining the spin-lattice relaxation time T1 of an image during a Nuclear Magnetic Resonance (NMR) measurement technique on a human body comprising the steps of: subjecting said body to magnetic fields in accordance with a NMR technique using a multiple spin-echo pulse sequence at two different predetermined stored pulse repetition times TR1 and TR2; measuring a first signal S(TR1) at a first one of (TR1) of said two repetition times including the steps of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a first period of time equal to a first pulse repetition time TR1, and then flipping the longitudinal magnetization Mz by 90° into the x-y plane wherein the value of x-y plane magnetization immediately after the step of flipping is said first signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said first signal S(TR1) is expressed by a first equation S(TR1)=M 0 [1-exp (-TR1/T1)] where M 0 is a constant; measuring a second signal at a second one TR2 of said two repetition times including the step of setting a longitudinal magnetization to an initial predetermined value M 0 , waiting a second period of time equal to said second pulse repetition time TR2, and then flipping the longitudinal magnetization by 90° into the x-y plane, wherein the value of the x-y plane magnetization immediately after the step of flipping is said second signal, called the transverse magnetization, which is equal to the value of the longitudinal magnetization immediately prior to the step of flipping and wherein said measured second signal S(TR2) is expressed by a second equation S(TR2)=M 0 [1-exp (TR1/T1)]; storing the value of said measured first and second signals; allowing said first and second measured signals to decay away at a characteristic time T2 and measuring said decaying signal at a plurality of echo times TE(i) i=1, . . . , N wherein said echo times are associated with 180° flips each associated with one of a multiple of spin-echos in said multiple spin-echo pulse sequence; storing said measured decaying signal values at each of said echo times TE(i) for each of said first and second pulse repetition times TR1, TR2; subjecting at each of said two different predetermined stored pulse repetition times TR1 and TR2 said measured decaying signal values at each of said echo-time to a regression which provides estimates of pseudo-density (P) and the spin-spin relaxation time (T2); calculating a synthetic spin-echo P exp (-TE/T2) where TE is an arbitrary operator specified value for each of TR1 and TR2; forming a ratio of said synthetic spin-echo of said first repetition time to said synthetic spin-echo of said second repetition time; solving a third equation R=[1-exp (TR1/T1)]/[1-exp(-TR2/T1)] for a T1 value by using the values of said first ratio R and said pulse repetition times TR1 and TR2.