MRI apparatus, flow quantification apparatus, and flow quantification method for ASL imaging

• US 20040030240A1
• Filed: 05/12/2003
• Published: 02/12/2004
• Est. Priority Date: 05/13/2002
• Status: Active Grant

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kimura, Tokunori
• Granted Patent: US 7,627,360 B2
• Time in Patent Office: Days
• US Class Current: 600/420
• CPC Class Codes: A61B 5/0263 using NMR
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography

Abstract

An MRI apparatus is provided to quantify perfusion (microcirculatory blood flow in the tissue) in a region to be imaged in a subject based an ASL (arterial spin labeling) technique. The apparatus comprises imaging, storing, and flow quantifying units. The imaging unit performs a scan according to the ASL technique on the region so that image data is acquired from the region. The storing unit stores relationship information between a concentration of tracer (water) and a flow of the perfusion. The relationship is obtained on a two-compartment model that uses two compartments placed inside and outside of a flow of blood that diffuses into the tissue of the region and that considers temporal changes in the diffusion of the microcirculatory blood flow into the tissue. The flow quantifying unit quantifies the flow of the perfusion by applying an amount derived from the image data to the relationship information.

Claims

1. An MRI (Magnetic Resonance Imaging) apparatus comprising:

imaging means for performing a scan in accordance with an ASL (Arterial Spin Labeling) technique on a region to be imaged of a subject to be examined so that image data is acquired from the region to be imaged;

storing means for storing therein pieces of information indicative of a relationship between a concentration of tracer served by water and a flow of perfusion indicative of blood flow in the tissue, the relationship being obtained based on a model that uses at least two compartments placed inside and outside of a flow of blood that diffuses into the tissue of the region to be imaged and that considers temporal changes in the diffusion of the blood flow into the tissue; and

quantifying means for quantifying the perfusion in the region to be imaged by giving an amount derived from the image data to the relationship information between the tracer concentration and the flow of the perfusion.

2. An MRI (Magnetic Resonance Imaging) apparatus comprising:

an imaging unit configured to perform a scan in accordance with an ASL (Arterial Spin Labeling) technique on a region to be imaged of a subject to be examined so that image data is acquired from the region to be imaged;

a storing unit configured to store therein pieces of information indicative of a relationship between a concentration of tracer served by water and a flow of perfusion indicative of blood flow in the tissue, the relationship being obtained based on a model that uses at least two compartments placed inside and outside of a flow of blood that diffuses into the tissue of the region to be imaged and that considers temporal changes in the diffusion of the blood flow into the tissue; and

a flow quantifying unit configured to quantify the flow of the perfusion in the region to be imaged by applying an amount derived from the image data to the relationship information between the tracer concentration and the flow of the perfusion.

3. The MRI apparatus according to claim 2, wherein the model that uses two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged.

4. The MRI apparatus according to claim 3, wherein the storing unit comprises

means configured to obtain a plurality of amounts of the tracer existing within a unit voxel that corresponds to each of a plurality of known flows by applying to the model representative parameters of the tissue in the region to be imaged;

means configured to approximating a relationship between the plurality of known flows and the plurality of amounts of the tracer to either a linier expression or a non-linear expression; and

means configured to memorize, as the correspondence information, a correspondence relationship based on either the linier expression or the non-linear expression in the form of either a table or a conversion expression.

5. The MRI apparatus according to claim 4, wherein the flow quantifying unit comprises

means configured to obtain an amount of the tracer within a unit voxel from signal intensities of the image data based on the ASL technique;

and

means configured to convert the amount of the tracer into the flow of the perfusion using either the table or the conversion expression.

6. The MRI apparatus according to claim 5, wherein the obtaining means is configured to obtain an ASRL (ASL signal to control signal ratio image) from the image data based on the ASL technique and to calculate the amount of the tracer using the ASLR image.

7. The MRI apparatus according to claim 2, wherein the storing unit comprises means configured to use reference data to correct the correspondence relationship between the tracer concentration and the flow of the perfusion.

8. The MRI apparatus according to claim 2, wherein the imaging unit is configured to perform the scan based on an ASTAR (modified STAR using Asymmetric Inversion slabs) technique.

9. The MRI apparatus according to claim 2, wherein the imaging unit is configured to perform the scan based on a VS-ASL (Velocity Selective Arterial Spin Labeling) technique.

10. A flow quantification apparatus in which a model indicating a diffusion state of a flow of blood that diffuses into tissue of a region to be imaged of a subject to be examined is used for quantifying a flow of perfusion in the region to be imaged, the apparatus comprising:

a storing unit configured to store therein correspondence information between a concentration of tracer served by water and a flow of perfusion indicative of blood flow in the tissue of the region to be imaged, the relationship being obtained based on the model that uses at least two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged and that considers temporal changes in the diffusion of the blood flow into the tissue; and

a flow quantifying unit configured to quantify the flow of the perfusion in the region to be imaged by applying an amount derived from image data obtained by imaging means to the correspondence information between the tracer concentration and the flow of the perfusion.

11. The flow quantification apparatus according to claim 10, wherein the model that uses two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged.

12. The flow quantification apparatus according to claim 11, wherein the storing unit comprises

means configured to obtain a plurality of amounts of the tracer existing within a unit voxel that corresponds to each of a plurality of known flows by applying to the model representative parameters of the tissue in the region to be imaged;

means configured to approximating a relationship between the plurality of known flows and the plurality of amounts of the tracer to either a linier expression or a non-linear expression; and

means configured to memorize, as the correspondence information, a correspondence relationship based on either the linier expression or the non-linear expression in the form of either a table or a conversion expression, the correspondence relationship being applied to quantifying the flow of perfusion in the region to be imaged.

13. The flow quantification apparatus according to claim 12, wherein the imaging means is configured to obtain the image data by performing a scan based on an ASTAR (modified STAR using Asymmetric Inversion slabs) technique.

14. The flow quantification apparatus according to claim 12, wherein the imaging means is configured to obtain the image data by performing a scan based on a VS-ASL (Velocity Selective Arterial Spin Labeling) technique.

15. A flow quantification apparatus in which a model indicating a diffusion state of a flow of blood that diffuses into tissue of a region to be imaged of a subject to be examined is used for quantifying a flow of perfusion in the region to be imaged, the apparatus comprising:

means configured to obtain a plurality of amounts of a tracer existing within a unit voxel that corresponds to each of a plurality of known flows by applying, to the model, representative parameters of the tissue of the region to be imaged;

means configured to approximating a relationship between the plurality of known flows and the plurality of amounts of the tracer to a non-linear expression; and

means configured to memorize a correspondence relationship based on the non-linear expression in the form of either a table or a conversion expression, the correspondence relationship being applied to quantifying the flow of perfusion in the region to be imaged.

16. The flow quantification apparatus according to claim 15, wherein the model is a two-compartment model that uses two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged, the model being set in consideration of temporal changes in the diffusion of the blood flow into the tissue in the region to be imaged.

17. A flow quantification method in which a model indicating a diffusion state of a flow of blood that diffuses into tissue of a region to be imaged of a subject to be examined is used for quantifying a flow of perfusion in the region to be imaged, comprising the steps of:

storing correspondence information between a concentration of tracer served by water and the flow of perfusion indicative of blood flow in the tissue of the region to be imaged, the relationship being obtained based on the model that uses at least two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged and that considers temporal changes in the diffusion of the blood flow into the tissue; and

quantifying the flow of the perfusion in the region to be imaged by applying an amount derived from image data of the subject to the correspondence information between the tracer concentration and the flow of the perfusion.

18. The flow quantification method according to claim 17, wherein the model that uses two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged.

19. The flow quantification method according to claim 18, wherein the storing step comprises

a step of obtaining a plurality of amounts of the tracer existing within a unit voxel that corresponds to each of a plurality of known flows by applying, to the model, representative parameters of the tissue in the region to be imaged;

a step of approximating a relationship between the plurality of known flows and the plurality of amounts of the tracer to either a linier expression or a non-linear expression; and

a step of memorizing, as the correspondence information, a correspondence relationship based on either the linier expression or the non-linear expression in the form of either a table or a conversion expression.

20. A flow quantification method in which a model indicating a diffusion state of a flow of blood that diffuses into tissue of a region to be imaged of a subject to be examined is used for quantifying a flow of perfusion in the region to be imaged, comprising the steps of:

obtaining a plurality of amounts of a tracer existing within a unit voxel that corresponds to each of a plurality of known flows by applying, to the model, representative parameters of the tissue of the region to be imaged, the model being a two-compartment model that uses two compartments placed inside and outside of the flow of blood that diffuses into the tissue of the region to be imaged and being set in consideration of temporal changes in the diffusion of the blood flow into the tissue in the region to be imaged;

approximating a relationship between the plurality of known flows and the plurality of amounts of the tracer to a non-linear expression; and

memorizing a correspondence relationship based on the non-linear expression in the form of either a table or a conversion expression, the correspondence relationship being applied to quantifying the flow of perfusion in the region to be imaged.