Method and apparatus for calculating blood flow parameters

• US 6,898,453 B2
• Filed: 10/25/2001
• Issued: 05/24/2005
• Est. Priority Date: 10/25/2000
• Status: Expired due to Term

• Current Assignee: The John P. Robarts Research Institue
• Original Assignee: The John P. Robarts Research Institue
• Inventors: Lee, Ting Y.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US10/007,341
• Publication Number:
  US 20020177957A1
• Time in Patent Office: 1,307 Days
• Field of Search: 600/407, 600/410, 600/419, 600/420, 600/425, 600/431, 128/920, 128/922, 702/19, 700/90
• US Class Current: 600/407
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/704 Tables
• CPC Class Codes: A61B 6/481 involving the use of contrast agents
• CPC Class Codes: A61B 6/504 for diagnosis of blood vessels, e.g. by angiography
• CPC Class Codes: A61B 6/507 for determination of haemodynamic parameters, e.g. perfusion CT
• CPC Class Codes: G06T 2207/30016 Brain
• CPC Class Codes: G06T 2207/30024 Cell structures in vitro; Tissue sections in vitro
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/66 of image moments or centre of gravity
• CPC Class Codes: G16H 10/20 for electronic clinical trials or questionnaires
• CPC Class Codes: Y10S 128/92 Computer assisted medical diagnostics

Abstract

A method for determining tissue type includes quantitatively determining a tissue blood flow (TBF) by deconvoluting Q(t) and C_a(t), where Q(t) represents a curve of specific mass of contrast, and C_a(t) represents an arterial curve of contrast concentration, and quantitatively determining a tissue blood volume (TBV) by deconvoluting Q(t) and C_a(t). The method also includes quantitatively determining a tissue mean transit time (TMTT) by deconvoluting Q(t) and C_a(t), and quantitatively determining a tissue capillary permeability surface area product (TPS) by deconvoluting Q(t) and C_a(t). The method also includes determining a tissue type based on the TBF, the TBV, the TMTT, and the TPS.

Claims

1. A method for determining tissue type, said method comprising:

quantitatively determining a tissue blood flow (TBF) by deconvoluting Q(t) and C_a(t), where Q(t) is a tissue residue function and represents a curve of specific mass of contrast in tissue, and C_a(t) represents an arterial curve of contrast concentration for a tissue having a blood stream containing a contrast without leaking the contrast into an interstitial space of the tissue by solving a matrix equation of Q=Ah for a vector h, and determining a least squares solution for the vector h under an equality constraint, wherein vector h includes a plurality of elements comprising an impulse residue function at different times Q comprises a vector including elements comprising values of a tissue residue function at different times, A comprises a matrix formed by values of the arterial curve of contrast concentration at different times;

quantitatively determining a tissue blood volume (TBV) by deconvoluting Q(t) and C_a(t), quantitatively determining a TBV comprises quantitatively determining a TBV for the tissue by solving the matrix equation of Q=Ah for the vector h, and determining a least squares solution for the vector h under an equality constraint;

quantitatively determining a tissue mean transit time (TMTT) by deconvoluting Q(t) and C_a(t), quantitatively determining a TMTT comprises quantitatively determining a TMTT for the tissue by solving the matrix equation of Q=Ah for the vector h, and determining a least squares solution for the vector h under an equality constraint; and

determining a tissue type based on the TBF, the TBV, and the TMTT.

2. A method in accordance with claim 1 wherein determining a least squares solution comprises determining a least squares solution for the vector h under a time causality constraint and a minimum transit time constraint.

3. A method in accordance with claim 2 wherein determining a least squares solution further comprises determining a least squares solution for the vector h under a smoothness constraint, a nonnegativity constraint, and a monotonicity constraint, wherein the smoothness constraint forces h to be smoothly varying, and the monotonicity and nonnegativity constraints force h to start at a maximum and then monotonically decreases towards a zero baseline.

4. A method in accordance with claim 1 further comprising quantitatively determining a partial volume averaging scaling factor for the arterial curve of contrast concentration by:

deconvoluting the measured arterial curve of contrast concentration with a venous curve of contrast concentration to determine a transit time spectrum through a tissue of interest;

extrapolating the arterial curve; and

convolving the extrapolated arterial curve with the transit time spectrum to generate an extrapolated venous curve, wherein the partial volume averaging scaling factor is the ratio of an area underneath the extrapolated arterial curve to an area underneath the extrapolated venous curve.

5. A method in accordance with claim 1 wherein the TBF is a cerebral blood flow (CBF), the TBV is a cerebral blood volume (CBV), and the TMTT is a cerebral mean transit time (CMTT), said determining a tissue type based on the TBF, the TBV, and the TMTT comprises determining one of a viable tissue and a non-viable tissue based on the CBF, the CBV, and the CMTT.

6. A method for determining tissue type, said method comprising:

quantitatively determining a tissue blood flow (TBF) by deconvoluting Q(t) and C_a(t), and their combinations thereof, where Q(t) is a tissue residue function and represents a curve of specific mass of contrast in tissue, and C_a(t) represents an arterial curve of contrast concentration for a tissue having a blood stream containing a contrast with leaking the contrast into an interstitial space of the tissue by solving a matrix equation of Q=Ax from the linearization of the tissue residue function for a vector x, wherein vector x includes a plurality of elements comprising TBF, tissue blood volume TBV, tissue mean transit time TMTT, tissue permeability surface area TPS and combinations thereof, Q comprises a vector including elements comprising values of a tissue residue function at different times, A comprises a matrix formed by values of the arterial curve of contrast concentration and tissue residue function at different times and their combinations thereof, quantitatively determining a TBF comprises quantitatively determining a TBF for the tissue by solving the matrix equation of Q=Ax for the vector x,

quantitatively determining a TBV comprises quantitatively determining a TBV for the tissue by solving the matrix equation of Q=Ax for the vector x,

quantitatively determining a TMTT comprises quantitatively determining a TMTT for the tissue by solving the matrix equation of Q=Ax for the vector x,

quantitatively determining a TPS comprises quantitatively determining a TPS for the tissue by solving the matrix equation of Q=Ax for the vector x; and

determining a tissue type based on the TBF, TBV, TMTT, and the TPS.

7. A method in accordance with claim 6 further comprising determining a least squares solution for the TBF, the TBV, the TMTT, and the TPS under a nonnegativity constraint that determines a TBV, a TBF, a TMTT and a TPS for the tissue where there is leakage of the contrast from the blood stream into the interstitial space.

8. A method in accordance with claim 6 further comprising quantitatively determining a partial volume averaging scaling factor for the arterial curve of contrast concentration by:

deconvoluting the measured arterial curve of contrast concentration with a venous curve of contrast concentration to determine a transit time spectrum through a tissue of interest;

extrapolating the arterial curve; and

convolving the extrapolated arterial curve with the transit time spectrum to generate an extrapolated venous curve, wherein the partial volume averaging scaling factor is the ratio of an area underneath the extrapolated arterial curve to an area underneath the extrapolated venous curve.

9. An imaging system comprising at least one of a computed tomography system and a nuclear magnetic resonance system, said imaging system configured to:

measure Q(t) and C_a(t), where Q(t) is a tissue residue function and represents a curve of specific mass of contrast in tissue, and C_a(t) represents an arterial curve of contrast concentration;

quantitatively determine a tissue blood flow (TBF) for a tissue having a blood stream containing a contrast without leaking the contrast into an interstitial space of the tissue by solving a matrix equation of Q=Ah for a vector h, and determining a least squares solution for the vector h under an equality constraint, wherein vector h includes a plurality of elements comprising an impulse residue function at different times, Q comprises a vector including elements comprising values of a tissue residue function at different times, A comprises a matrix formed by values of the arterial curve of contrast concentration at different times;

quantitatively determine a tissue blood volume (TBV) for the tissue by solving the matrix equation of Q=Ah for the vector h, and determining a least squares solution for the vector h under an equality constraint;

quantitatively determine a TMTT for the tissue by solving the matrix equation of Q=Ah for the vector h, and determining a least squares solution for the vector h under an equality constraint; and

determine a tissue type based on the TBF, the TBV, and the TMTT.

10. A system according to claim 9 further configured to determine a least squares solution for the vector h under a time causality constraint and a minimum transit time constraint.

11. A system according to claim 9 further configured to determine a least squares solution for the vector h under a smoothness constraint, a nonnegativity constraint, and a monotonicity constraint, wherein the smoothness constraint forces h to be smoothly varying, and the monotonicity and nonnegativity constraints force h to start at a maximum and then monotonically decreases towards a zero baseline.

12. An imaging system comprising at least one of a computed tomography system and a nuclear magnetic resonance system, said imaging system configured to:

measure Q(t) and C_a(t), where Q(t) is a tissue residue function and represents a curve of specific mass of contrast in tissue, and C_a(t) represents an arterial curve of contrast concentration;

quantitatively determine a tissue blood flow (TBF) for a tissue having a blood stream containing a contrast with leaking the contrast into an interstitial space of the tissue by solving a matrix equation of Q=Ax from the linearization of the tissue residue function for a vector x, wherein vector x includes a plurality of elements comprising TBF, tissue blood volume (TBV), tissue mean transit time (TMTT), tissue permeability surface area product (TPS) and combinations thereof, Q comprises a vector including elements comprising values of a tissue residue function at different times, A comprises a matrix formed by values of the arterial curve of contrast concentration and tissue residue function at different times and combinations thereof;

quantitatively determine a TBV for the tissue by solving the matrix equation of Q=Ax for the vector x;

quantitatively determine a TMTT for the tissue by solving the matrix equation of Q=Ax for the vector x;

quantitatively determine a TPS for the tissue by solving the matrix equation of Q=Ax for the vector x; and

determine a tissue type based on the TBF, the TBV, the TMTT, and the TPS.

13. A system according to claim 12 further configured to determine a least squares solution for the TBF, the TBV, the TMTT, and the TPS under a nonnegativity constraint that determines a TBV, a TBF, a TMTT and a TPS for the tissue where there is leakage of the contrast from the blood stream into the interstitial space.

14. A system according to claim 12 wherein the TBF is a cerebral blood flow (CBF), the TBV is a cerebral blood volume (CBV), the TMTT is a cerebral mean transit time (CMTT), the TPS is a cerebral TPS, said system further configured to determine one of a viable tissue and a non-viable tissue based on the CBF, the CBV, the CMTT, and the cerebral TPS.