T1rho dispersion characterization by magnetic resonance fingerprinting
Magnetic resonance fingerprinting (MRF) is used to quantify T 1ρ dispersion across spin-lock frequencies and enables simultaneous mapping of T 1 , T 2 , and T 1ρ dispersion. T 1ρ at a specific FSL may be determined by retrospectively computation based on the results of the T 1ρ dispersion MRF dictionary and pattern matching results. The T 1ρ dispersion characteristic may be used to identify and track tissue parameters (such as osteoarthritis and muscle degeneration) before being expressed in other measurable manners.
1 . A magnetic resonance fingerprinting (MRF) method, comprising:
applying an MRF pulse sequence to tissue of a subject;
acquiring magnetic resonance (MR) signal data as a result of the application of the MRF pulse sequence;
comparing the MR signal data to a predefined MRF dictionary, the MRF dictionary comprising a model of T 1ρ dispersion; and
determining a property of the tissue from the T 1ρ dispersion model based on a result of the comparison,
wherein the MRF pulse sequence includes a single fixed spin-lock frequency.
2 . The method according to claim 1 , wherein T 1ρ dispersion is modeled according to:
T
1
ρ
(
ω
)
=
(
q
2
D
)
2
+
ω
2
γ
2
g
2
D
=
m
2
(
q
2
D
)
2
+
m
2
ω
2
where
T
1
ρ
(
0
)
=
m
2
(
q
2
D
)
2
=
T
2
and
T
1
ρ
(
ω
)
=
T
2
+
(
m
ω
)
2
where γ is a hydrogen gyromagnetic ratio, D is a self-diffusion coefficient, q is a spatial frequency of a local magnetic field variation, g is a mean local magnetic gradient strength, ω is frequency, and m is a mediation coefficient that mediates a strength of a T 1ρ dispersion effect and represents a combination of γ, D, and g.
3 . The method according to claim 1 , wherein T 1ρ dispersion is modeled according to:
T
1
ρ
(
ω
)
=
T
2
+
m
ω
where ω is frequency, and m is a mediation coefficient that mediates a strength of a T 1ρ dispersion effect and represents a combination of a hydrogen gyromagnetic ratio, a self-diffusion coefficient, and a mean local magnetic gradient strength.
4 . The method according to claim 1 , wherein the determined tissue property relates to tissue degeneration.
5 . The method according to claim 1 , further comprising:
identifying an osteoarthritis or muscle degeneration condition in the subject based on the identified property.
6 . The method of claim 1 , further comprising:
applying a plurality MRF pulse sequencies; and
tracking a change in T 1ρ dispersion of the tissue of the subject over the plurality of applied MRF sequences.
7 . The method of claim 1 , further comprising:
applying a plurality MRF pulse sequencies; and
tracking a change in the determined tissue property over the plurality of applied MRF sequences.
8 . The method according to claim 1 , further comprising:
determining a T 1ρ dispersion by retrospectively determining T 1ρ at a plurality of spin-lock frequencies based on the model of the MRF dictionary.
9 . The method according to claim 1 , wherein the MRF dictionary comprises fingerprints of at least T 1 , T 2 , and a mediation coefficient that mediates a strength of a T 1ρ dispersion effect.
10 . The method according to claim 1 , wherein the MR signal data is compared to the predefined MRF dictionary with a machine learning system trained to identify MR properties of the MRF dictionary based on input MR signal data.
11 . A magnetic resonance fingerprinting (MRF) method, comprising:
applying an MRF pulse sequence to tissue of a subject;
acquiring magnetic resonance (MR) signal data as a result of the application of the MRF pulse sequence;
comparing the MR signal data to a predefined MRF dictionary, the MRF dictionary comprising a model of T 1ρ dispersion; and
determining a property of the tissue from the T 1ρ dispersion model based on a result of the comparison,
wherein T 1ρ dispersion is modeled according to:
T
1
ρ
(
ω
)
=
(
q
2
D
)
2
+
ω
2
γ
2
g
2
D
=
m
2
(
q
2
D
)
2
+
m
2
ω
2
where
T
1
ρ
(
0
)
=
m
2
(
q
2
D
)
2
=
T
2
and
T
1
ρ
(
ω
)
=
T
2
+
(
m
ω
)
2
where γ is a hydrogen gyromagnetic ratio, D is a self-diffusion coefficient, q is a spatial frequency of a local magnetic field variation, g is a mean local magnetic gradient strength, ω is frequency, and m is a mediation coefficient that mediates a strength of a T 1ρ dispersion effect and represents a combination of γ, D, and g.
12 . The method according to claim 11 , wherein the determined tissue property relates to tissue degeneration.
13 . The method according to claim 11 , further comprising:
identifying an osteoarthritis or muscle degeneration condition in the subject based on the identified property.
14 . The method of claim 11 , further comprising:
applying a plurality MRF pulse sequencies; and
tracking a change in T 1ρ dispersion of the tissue of the subject, or in the determined tissue property, over the plurality of applied MRF sequences.
15 . The method according to claim 11 , wherein the MRF dictionary comprises fingerprints of at least T 1 , T 2 , and m.
16 . A magnetic resonance fingerprinting (MRF) method, comprising:
applying an MRF pulse sequence to tissue of a subject;
acquiring magnetic resonance (MR) signal data as a result of the application of the MRF pulse sequence;
comparing the MR signal data to a predefined MRF dictionary, the MRF dictionary comprising a model of T 1ρ dispersion; and
determining a property of the tissue from the T 1ρ dispersion model based on a result of the comparison,
wherein T 1ρ dispersion is modeled according to:
T
1
ρ
(
ω
)
=
T
2
+
m
ω
where ω is frequency, and m is a mediation coefficient that mediates a strength of a T 1ρ dispersion effect and represents a combination of a hydrogen gyromagnetic ratio, a self-diffusion coefficient, and a mean local magnetic gradient strength.
17 . The method according to claim 16 , wherein the determined tissue property relates to tissue degeneration.
18 . The method according to claim 16 , further comprising:
identifying an osteoarthritis or muscle degeneration condition in the subject based on the identified property.
19 . The method of claim 16 , further comprising:
applying a plurality MRF pulse sequencies; and
tracking a change in T 1ρ dispersion of the tissue of the subject, or in the determined tissue property, over the plurality of applied MRF sequences.
20 . The method according to claim 16 , wherein the MRF dictionary comprises fingerprints of at least T 1 , T 2 , and m.