Method of assessing the level of vascular inflammation
The present invention describes a new functional biomarker of vascular inflammation and its use in predicting all-cause or cardiac mortality. The invention also provides a method for stratifying patients according to their risk of all-cause or cardiac mortality using data gathered from a computer tomography scans of a blood vessel to determine a specific combination of structural and functional biomarkers of vascular inflammation and disease.
1. A method of assessing the level of vascular inflammation in a patient in need thereof, the method comprising:
determining a perivascular water index (PVWi) of a blood vessel by:
(i) using data gathered from a computer tomography scan along a length of the vessel to determine a total volume of voxels of water within an attenuation window around the attenuation of water within a perivascular space a pre-determined distance from an outer wall of the vessel, and
(ii) correcting the total volume of the voxels of water for the volume of the vessel by dividing the total volume of voxels of water determined in step (i) by the total perivascular volume; and
determining the level of vascular inflammation in the patient using the perivascular water index.
2. The method according to claim 1 , wherein the attenuation window around the attenuation of water is from −30 to +30 Hounsfield units (HU) or from −15 to +15 HU.
3. The method according to claim 1 , wherein the pre-determined distance from the outer wall of the vessel is a standard distance that is not equal to or related to the diameter or radius of the underlying vessel.
4. The method according to claim 1 , wherein the pre-determined distance from the outer wall of the vessel is either a distance equal to the radius or diameter of the underlying vessel or a distance that is representative of a dimension of the underlying vessel.
5. The method according to claim 1 , wherein the data is gathered from a computer tomography scan along a length of the right coronary artery, left anterior descending artery, left circumflex artery, aorta, carotid arteries or femoral arteries.
6. The method according to claim 5 , wherein the data is gathered from a computer tomography scan along a 4 cm length, starting 1 cm distally to the origin of the right coronary artery.
7. The method according to claim 1 , wherein the PVWi is used to predict all-cause or cardiac mortality risk in the patient.
8. The method according to claim 7 , wherein PVWi is used in combination with additional functional and/or structural biomarkers of vascular inflammation, and wherein the structural biomarkers of vascular inflammation include one or more of calcium index and fibrous plaque index, and/or wherein the additional functional biomarkers of vascular inflammation include one or more of the fat attenuation index of the perivascular adipose tissue (FAI PVAT ), fat attenuation index of the epicardial adipose tissue (FAI EpAT ) and volumetric perivascular characterization index (VPCI).