Method for characterisation of perivascular tissue
Methods for volumetric characterisation of perivascular adipose tissue use data collected by computed tomography (CT) scanning. The volumetric characterisation of perivascular adipose tissue allows the inflammatory status of underlying blood vessels to be established by CT scanning. This is of use in the diagnosis, prognosis and treatment of coronary and vascular disease.
1. A method for detecting inflammation of a blood vessel by volumetric characterisation of perivascular adipose tissue surrounding the blood vessel from a length of computed tomography (CT) scanned blood vessel in a patient; the method comprising:
gathering data from a computed tomography scan of the perivascular adipose tissue surrounding the scanned blood vessel along the length of the scanned blood vessel;
volumetrically characterizing with a processor only the perivascular adipose tissue using the data gathered by the computed tomography scan, wherein the characterized perivascular adipose tissue consists of one or more concentric layers of adipose tissue surrounding the length of the scanned blood vessel;
quantifying radiodensity values as attenuation in each of the one or more concentric layers of perivascular adipose tissue surrounding the length of the scanned blood vessel;
determining whether one or more of the quantified radiodensity values are above or below a baseline radiodensity value; and
administering a therapy to the patient to treat or prevent vascular disease based on whether the quantified radiodensity values of the characterized perivascular tissue are above or below the baseline radiodensity value.
2. The method according to claim 1 , wherein the quantified radiodensity is quantified for water in the each of one or more concentric layers of perivascular adipose tissue.
3. The method according to claim 1 , wherein the quantified radiodensity is an average radiodensity.
4. The method according to claim 3 , wherein the data is gathered from the computed tomography scan along a 4 cm length, starting 1 cm distally to the origin of the right coronary artery.
5. The method according to claim 1 , wherein the data is gathered from the computed 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 1 , wherein the data is gathered from the computed tomography scan along a length of the aorta.
7. The method according to claim 1 , wherein the each of one or more concentric layers of perivascular adipose tissue are 1 mm thick.
8. The method according to claim 1 , wherein the each of one or more concentric layers of perivascular adipose tissue extend to an end distance from the outer wall of the blood vessel, the end distance being the point where radiodensity of adipose tissue reaches a minimum value within a scanned anatomical area in a healthy vessel or drops by >10% vs the baseline radiodensity value, in a vessel of the same type free of disease.
9. The method according to claim 8 , wherein the each of one or more concentric layers of perivascular adipose tissue extend to an end distance of 10 mm from the outer wall of the blood vessel.
10. The method according to claim 8 , wherein the each of one or more concentric layers of perivascular adipose tissue extend to an end distance of 20 mm from the outer wall of the blood vessel.
11. The method according to claim 1 , wherein the baseline radiodensity value is average radiodensity quantified in a layer of perivascular adipose tissue lying within the first 1 mm-thick concentric layer surrounding the outer vessel wall.
12. The method according to claim 11 , wherein the baseline radiodensity is radiodensity quantified for adipose tissue in a layer of perivascular adipose tissue lying proximal to the outer wall of the blood vessel; and wherein the adipose tissue in the layer lying proximal corresponds to voxels having an attenuation of −190 to −30 Hounsfield Units (HU).
13. The method according to claim 11 , wherein the baseline radiodensity is radiodensity quantified for water in a layer of perivascular adipose tissue lying proximal to the outer wall of the blood vessel; and wherein the water corresponds to voxels having an attenuation of −15 to +15 Hounsfield Units (HU).
14. The method according to claim 1 , further comprising:
determining a plot of a fold change in the quantified radiodensity relative to baseline radiodensity in the each of one or more concentric layers of perivascular adipose tissue with respect to distance from the outer wall of the blood vessel up to an end distance;
determining an area of a region bound by the plot of fold change in the quantified radiodensity and a plot of baseline radiodensity with respect to the distance from the outer wall of the blood vessel up to the end distance; and
dividing said area by the quantified radiodensity measured at the distance from the outer wall of the blood vessel, wherein the distance is less than the radius of the vessel or is a distance from the outer surface of the vessel above which the quantified radiodensity of adipose tissue drops by more than 5% compared to baseline radiodensity of adipose tissue in a vessel of the same type free of disease.
15. The method according to claim 14 , wherein the quantified radiodensity is quantified radiodensity of adipose tissue in the each of one or more concentric layers of perivascular adipose tissue.
16. The method according to claim 14 , wherein the quantified radiodensity is quantified radiodensity of water in the each of one or more concentric layers of perivascular adipose tissue.
17. The method according to claim 14 , wherein the quantified radiodensity is an average radiodensity.
18. The method according to claim 14 , wherein the end distance is the point where radiodensity of adipose tissue reaches a minimum value within a scanned anatomical area in a healthy vessel or drops by >10% below the baseline radiodensity value, in a vessel of the same type free of disease.
19. The method according to claim 18 , wherein the end distance is 10 mm.
20. The method according to claim 18 , wherein the end distance is 20 mm.
21. The method according to claim 1 , further comprising:
subtracting quantified radiodensity in a layer of non-perivascular adipose tissue from the quantified radiodensity in a layer of perivascular adipose tissue located at a distance equal to the radius of the vessel around the outer wall of the blood vessel.
22. The method according to claim 21 , wherein the quantified radiodensity in a layer of perivascular adipose tissue is quantified radiodensity of adipose tissue in the layer of perivascular adipose tissue located at the distance equal to the radius.
23. The method according to claim 21 , wherein the quantified radiodensity in a layer of non-perivascular tissue is quantified radiodensity of adipose tissue in the layer of non-perivascular tissue located at the distance equal to the radius.
24. The method according to claim 21 , wherein the quantified radiodensity in a layer of perivascular adipose tissue is quantified radiodensity of water in the layer of perivascular adipose tissue.
25. The method according to claim 21 , wherein the quantified radiodensity in a layer of non-perivascular tissue is quantified radiodensity of water in the layer of non-perivascular tissue.
26. The method according to claim 21 , wherein the quantified radiodensity in a layer of perivascular adipose tissue is an average radiodensity.
27. The method according to claim 21 , wherein the quantified radiodensity in a layer of non-perivascular adipose tissue is an average radiodensity.
28. The method according to claim 21 , wherein the quantified radiodensity in a layer of non-perivascular tissue is radiodensity measured in a layer of non-perivascular tissue located at a distance greater than an average radius of the vessel around the outer wall of the blood vessel.
29. The method according to claim 21 , wherein the quantified radiodensity in a layer of non-perivascular tissue is radiodensity measured in a layer of non-perivascular tissue located at a distance equal to three times an average radius of the vessel around the outer wall of the blood vessel.
30. The method according to claim 21 , further comprising assigning a determined value of a difference between the quantified radiodensity in a layer of perivascular adipose tissue and the quantified radiodensity in a layer of non-perivascular tissue to a scale having a lower threshold and a higher threshold.
31. The method according to claim 30 , wherein the lower threshold is a value between the lowest and mid tertile.
32. The method according to claim 31 , wherein the lower threshold is 2.
33. The method according to claim 30 , wherein the upper threshold is a value between the mid and highest tertile.
34. The method according to claim 33 , wherein the upper threshold is 8.
35. The method according to claim 1 , wherein the step of gathering data from the computed tomography scan along the length of the scanned blood vessel comprises gathering images from the computed tomography scan.
36. The method according to claim 1 , further comprising determining whether the scanned blood vessel is an inflamed blood vessel and has released mediators exerting a paracrine effect on the perivascular adipose tissue surrounding the inflamed scanned blood vessel.
37. A method for detecting inflammation of a blood vessel by volumetric characterization of perivascular adipose tissue surrounding the blood vessel to guide treatment for prevention or management of vascular tissue; the method comprising:
conducting a computed tomography scan of the perivascular adipose tissue surrounding a wall of the blood vessel of a length of blood vessel in a patient;
gathering data from the computed tomography scan along and surrounding the length of the scanned blood vessel;
volumetrically characterizing with a processor only the perivascular adipose tissue using the data gathered by the computed tomography scan, wherein the characterized perivascular adipose tissue consists of one or more concentric layers of adipose tissue surrounding the length of the scanned blood vessel;
quantifying radiodensity values comprising attenuation in each of the one or more concentric layers of perivascular adipose tissue surrounding the length of the scanned blood vessel;
determining whether one or more of the quantified radiodensity values are above or below a baseline radiodensity value; and
administering a therapy to the patient to treat or prevent vascular disease based on whether the quantified radiodensity values of the characterized perivascular tissue are above or below the baseline radiodensity value.
38. The method according to claim 37 , further comprising determining whether the scanned blood vessel is an inflamed blood vessel and has released mediators exerting a paracrine effect on the perivascular adipose tissue surrounding the inflamed scanned blood vessel.