Methods for determination of parameters for a procedure, for estimation of cardiopulmonary function and for fluid delivery

• US 8,428,694 B2
• Filed: 06/24/2008
• Issued: 04/23/2013
• Est. Priority Date: 07/17/2007
• Status: Active Grant

• Current Assignee: Bayer Healthcare LLC (Bayer AG)
• Original Assignee: Medrad Incorporated (Bayer AG)
• Inventors: Kalafut, John F., Kemper, Corey
• Primary Examiner(s): Smith, Ruth S
• Application Number:
  US12/669,292
• Publication Number:
  US 20100204572A1
• Time in Patent Office: 1,764 Days
• Field of Search: 600/420, 600/431, 600/481, 604/19, 604/28, 604/67, 604/131, 382/128, 382/131
• US Class Current: 600/431
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• 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: G16H 30/20 for handling medical images, e.g. DICOM, HL7 or PACS
• CPC Class Codes: G16H 40/63 for local operation

Abstract

Methods of determining at least one parameter for an injection procedure to be performed in combination with an imaging procedure may include injecting a test bolus of a contrast enhancement fluid having a contrast enhancing agent, scanning regions of interest with an imaging system as the test bolus flows therethrough to obtain therefrom a contrast time enhancement curve for each region of interest, extracting at least one discrete data point from each of the contrast time enhancement curves such that each of the discrete data points constitutes a pair of measurements on the contrast time enhancement curve corresponding thereto, substituting into a model the discrete data points extracted from the contrast time enhancement curves to obtain an estimate of values of physiological variables, and using the estimate to determine via the model the at least one parameter for the injection procedure to be performed in combination with the imaging procedure.

Claims

1. A method of determining at least one parameter for an injection procedure to be performed in combination with an imaging procedure, the method comprising the steps of:

(a) injecting a test bolus of a contrast enhancement fluid having a contrast enhancing agent therein;

(b) scanning at least two regions of interest with an imaging system as the test bolus of the contrast enhancement fluid flows therethrough to obtain therefrom a contrast time enhancement curve for each of the at least two regions of interest;

(c) extracting at least one discrete data point from each of the contrast time enhancement curves such that each of the discrete data points constitutes a pair of measurements on the contrast time enhancement curve corresponding thereto;

(d) substituting into a model the discrete data points extracted from the contrast time enhancement curves to obtain therefrom at least an estimate of values of physiological variables; and

(e) using the at least an estimate of the values of the physiological variables to determine via the model the at least one parameter for the injection procedure to be performed in combination with the imaging procedure.

2. The method of claim 1 wherein the physiological variables are related to cardiopulmonary function.

3. The method of claim 2 wherein the at least one parameter is a parameter of at least one phase of the injection procedure for the injection of the contrast enhancement fluid or a parameter of the imaging system.

4. The method of claim 2 wherein the discrete data point(s) from the contrast time enhancement curve of a first of the regions of interest corresponds to a first pass of the contrast enhancement fluid through the first region of interest, and the discrete data point(s) from the contrast time enhancement curve of a second of the regions of interest corresponds to a first pass of the contrast enhancement fluid through the second region of interest.

5. The method of claim 4 wherein an analyzed portion of the contrast time enhancement curve of the first region of interest overlaps an analyzed portion of the contrast time enhancement curve of the second region of interest in time.

6. The method of claim 4 wherein a contrast enhancing agent concentration on one of the contrast time enhancement curves at a certain time is related to a contrast enhancing agent concentration on the other of the contrast time enhancement curves at the certain time or a time in proximity to the certain time using a conservation of mass balance.

7. The method of claim 6 wherein it is assumed that the loss of the contrast enhancement fluid between the first region of interest and the second region of interest is negligible.

8. The method of claim 7 wherein it is assumed that the blood volume for the first region of interest is equal to the blood volume for the second region of interest.

9. The method of claim 2 wherein the model is a physiological model in which cardiac output and blood volume are the physiological variables, the cardiac output and the blood volume between the injection site and a measurement point of each of the regions of interest are calculated for a patient, and the at least one parameter is determined using the physiological model.

10. The method of claim 8 wherein the model is a physiological model in which cardiac output and blood volume are physiological variables, the cardiac output and the blood volume between the injection site and a measurement point of each of the regions of interest are calculated for a patient, and the at least one parameter is determined using the physiological model.

11. The method of claim 10 wherein a time to peak enhancement for first region of interest enhancement T₁ and a time to peak enhancement for the second region of interest enhancement T₂ are input into the physiological model.

12. The method of claim 11 wherein concentration at peak enhancement for the first region of interest enhancement C₁(T₁) and concentration at peak enhancement for the second region of interest enhancement C₂(T₂) are input into the physiological model.

13. The method of claim 12 wherein a distribution of contrast enhancement fluid in each region of interest which is injected from a peripheral injection site is described by the following physiological model analytical solution:

14. The method of claim 13 wherein concentration is related to enhancement level by the formula:

C_O(t)=s(t)/K

wherein s(t) [Hounsfield units or HU] is enhancement level at time t and K [mgI/ml] is a conversion factor.

15. The method of claim 14 wherein T_inj is the injection duration and is amount of time between arrival of the contrast enhancement agent and the time to peak enhancement.

16. The method of claim 15 wherein:

17. The method of claim 14 wherein concentration in the first region of interest C₁ at time T₂ is estimated by the following formula:

C₁(T₂)≈

C₁(T₁)C₂(T₂)

wherein C₁(T₁) is the concentration in the first region of interest C₁ at time T₁ and C₂(T₂) is the concentration in the second region of interest C₂ at time T₂.

18. The method of claim 17 wherein blood volume V_B is determined using one of the following formulas:

19. The method of claim 18 wherein cardiac output Q_CO is determined using the following formula:

20. The method of claim 19 wherein the determined value of Q_CO is used in the physiological model to determine the at least one parameter.

21. The of claim 20 wherein concentration of contrast agent at peak enhancement C(T_Peak) at the time of peak enhancement T_Peak in the second region of interest of an imaging injection is related to the injection flow rate Q_inj of the imaging injection and the injection duration T_inj of the imaging injection using the formula:

22. The method of claim 21 wherein a concentration of contrast agent in the second region of interest at time of a scan start, C(T_start), is provided by:

23. The method of claim 22 wherein C(T_Peak) and C(T_start) enhancements are determined for admissible input values for T_inj and Q_inj wherein a maximum Q_inj and a minimum Q_inj and a maximum T_inj and a minimum T_inj are established.

24. The method of claim 23 wherein maximum T_inj is established as a function of scan duration plus a constant, minimum T_inj is established as the scan duration.

25. The method of claim 24 wherein values for a diagnostic protocol flow rate Q*_imj and an injection duration T*_inj are determined which are the arguments that minimize the cost function:

26. The method of claim 20 wherein the first region of interest is the pulmonary artery and the second region of interest is the ascending aorta and values for a diagnostic protocol flow rate are determined which are the arguments that minimize the cost function:

27. The method of claim 26 wherein C_LH-Peak is the greater of the value calculated as follows:

28. The method of claim 27 wherein concentration C_T in the right heart or the left heart as applicable at a time T, which is either T_start or T_end, when T<

(T_arr+Δ

T_inj1), wherein T_arr is either the time of arrival of contrast at the right heart or at the left heart as applicable, is calculated by the following formula;

29. The method of claim 27 wherein concentration C_T in the right heart or the left heart as applicable at a time T, when (T_arr+Δ

T_inj1)<

T<

(T_arr+Δ

T_inj1+Δ

T_inj2), is calculated by the following formula;

30. The method of claim 27 wherein concentration C_T in the right heart or the left heart as applicable at a time T, when, T>

(T_arr+Δ

T_injA+Δ

T_injAB) is calculated by the following formula;

31. The method of claim 2 wherein the first region of interest is the pulmonary artery and the second region of interest is the ascending aorta.

32. The method of claim 2 wherein the physiological variables are used in connection with the model or at least one other model to determine the at least one parameter.

33. The method of claim 32 wherein the at least one other model is a parametric model.

34. The method of claim 1 wherein the steps (d) and (e) include:

(I) one of two equations for blood volume, V_B;

35. The method of claim 1 wherein the steps (d) and (e) include:

(I) one of two equations for blood volume, V_B;

36. A method of determining at least one parameter for a procedure, the method comprising the steps of:

(a) injecting a test bolus of a pharmaceutical;

(b) measuring at least two regions of interest with a sensor as the test bolus of the pharmaceutical flows therethrough to obtain therefrom a time concentration curve for each of the at least two regions of interest;

(c) extracting at least one discrete data point from each of the time concentration curves such that each of the discrete data points constitutes a pair of measurements on the time concentration curve corresponding thereto; and

(d) determining the at least one parameter for the procedure to be performed by substituting into a model the discrete data points extracted from the time concentration curves.

37. The method of claim 36 wherein a sufficient number of the discrete data points are substituted into the model to determine values for physiological variables in the model, the variables being related to cardiopulmonary function and for use in determining the at least one parameter for the procedure to be performed.

38. The method of claim 36 wherein the step of substituting the discrete data points into the model for use in determining the at least one parameter for the procedure includes:

(a) one of two equations for blood volume, V_B;

39. The method of claim 36 wherein the step of substituting the discrete data points into the model for use in determining the at least one parameter for the procedure includes:

(a) one of two equations for blood volume, V_B;