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

An MRI (Magnetic Resonance Imaging) apparatus comprising:

• an imaging unit configured to acquire image data by performing an ASL (Arterial Spin Labeling) scan on a region to be imaged;
• a storing unit configured to store information indicative of a relationship between a concentration of water tracer and a perfusion flow indicative of blood flow in tissue, the relationship being obtained based on a model that uses two compartments placed respectively inside and outside a flow of blood that diffuses into tissue of the region to be imaged and that takes into account temporal changes in diffusion of blood flow into the tissue;
• and
• a flow quantifying unit configured to quantify perfusion flow in the region to be imaged by using the image data and the relationship information between the tracer concentration and the perfusion flow;
• wherein the flow quantifying unit comprises:
• means configured to obtain a plurality of tracer amounts existing within a unit voxel which respectively correspond to each of a plurality of known flows by applying to the model representative parameters of tissue in the region to be imaged;
• means configured to approximate a relationship between the plurality of known flows and the plurality of tracer amounts using a polynomial expression which directly converts the tracer amounts into known flows using only coefficients of the polynomial expression as parameters;
• and
• wherein the storing unit comprises means configured to store, as correspondence information, a correspondence relationship based on the polynomial expression in the form of either a table or a conversion expression.

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

• a magnetic resonance imaging (MRI) means for performing magnetic resonance imaging of a subject region;
• a storing unit configured to store correspondence information between a concentration of water tracer and a perfusion flow indicative of blood flow in tissue of the region to be imaged, the relationship being obtained based on a model that uses two compartments placed respectively inside and outside the flow of blood that diffuses into tissue of the region to be imaged and that takes into account temporal changes in diffusion of blood flow into the tissue;
• and
• a flow quantifying unit configured to quantify the perfusion flow in the region to be imaged by using image data obtained by imaging means and the correspondence information between the tracer concentration and the perfusion flow;
• wherein the flow quantifying unit comprises:
• means configured to obtain a plurality of amounts of the tracer existing within a unit voxel which each respectively correspond to one of a plurality of known flows by applying to a model representative parameters of tissue in the region to be imaged;
• means configured to approximate a relationship between the plurality of known flows and the plurality of amounts of the tracer using a polynomial expression which directly converts the tracer amounts into known flows using only coefficients of the polynomial expression as parameters;
• and
• wherein the storm unit comprises means configured to store, as the correspondence information, a correspondence relationship based on the polynomial expression in the form of either a table or a conversion expression, the correspondence relationship being applied to quantifying the perfusion flow in the region to be imaged.

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 perfusion flow in the region to be imaged, said method comprising:

• use of a magnetic resonance imaging (MRI) means to acquire MRI data from patient tissue of a region to be imaged, including:
• storing correspondence information between a concentration of water tracer and perfusion flow indicative of blood flow in tissue of the region to be imaged, the relationship being obtained based on a model that uses two compartments placed respectively inside and outside the flow of blood that diffuses into tissue of the region to be imaged and that takes into account temporal changes in diffusion of blood flow into the tissue;
• and
• quantifying perfusion flow in the region to be imaged by using image data of the subject and the correspondence information between the tracer concentration and the perfusion flow;
• wherein the quantifying step comprises:
• obtaining a plurality of amounts of the tracer existing within a unit voxel which each respectively correspond to one of plural known flows by applying, to the model, representative parameters of 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 using a polynomial expression which directly converts the tracer amounts into known flows using only coefficients of the polynomial expression as parameters;
• and
• wherein the storing step comprises storing as the correspondence information, a correspondence relationship based on the polynomial expression in the form of either a table or a conversion expression.