Method and system for obtaining improved data perfusion measurements
AssigneeApollo Medical Imaging Technology Pty Ltd
InventorQing Yang
Life of this patent
Estimating the term…
Abstract
A method of deriving blood perfusion indices for a region of interest (ROI) of a subject, comprising the steps of administering a contrast agent to the subject during a dynamic imaging scan, converting signal intensity data from raw images of the scan into contrast agent concentration data, deriving parameters from the contrast agent concentration data using at least one transport function that accounts for delay and dispersion of the contrast agent, and calculating the blood perfusion indices from the derived parameters.
Claims5
A method of estimating blood perfusion indices, for a region of interest (ROI) by operating a computer program on intensity data input to a computer comprising:
- a. providing a contrast agent to an artery, wherein said artery is upstream from a region of interest (ROI), wherein said ROI comprises tissue;
- b. measuring intensity data to provide a tissue contrast agent curve C(t) in said tissue, wherein said C(t) is a known intensity profile measured against time;
- c. measuring an arterial input function AIFa(t) in a vessel leading to said ROI, wherein said AIFa(t) is known intensity profile measured against time;
- d. estimating a tissue blood flow Ft and a tissue impulse residue function R(t) by deconvolving C(t)=(Ft/kH)AIFa(t)R(t), wherein kH=(1−Ha)/(1−Ht) is a correction constant using different values of an arterial hematocrit Ha and a tissue hematocrit Ht, wherein said Ha has a value of about 0.45, wherein said Ht has a value of about 0.25, wherein when said AIFa(t) in a major artery comprises no delay and no dispersion, said C(t) can be derived by a convolution of said AIFa(t) and said R(t);
- e. determining a blood flow rate Ft and a tissue impulse residue function Re(t) using said C(t) and a tissue input function AIFt(t) by deconvolving the relation C(t)=(Ft/kH)AIFt(t)Re(t), wherein is the convolution operator, wherein said AIFt(t) comprises AIFt(t)=AIFa(t)ha(t), wherein ha(t) is a vascular transport function, wherein for t<t1, ha(t)=0 and for
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- wherein the initial value of a delay time t1 can be determined by the maximum position of said R(t), wherein σ1=(t1)(β1)/(1−β1), wherein β1 is a known relative dispersion value having a range from 0 to 1;
- f. measuring an arterial input function AIFa(t) in said artery at a position that is upstream from said tissue;
- g. simulating a tissue contrast agent concentration curve Cs(t) using a tissue transport function hs(t), wherein
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- wherein, said
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- for t≧t2, and said hs(t)=0 for t<t2, wherein t is time, wherein the intial value of a dispersion time σ2 can be dertermined by 1/PH and the initial vaule of a minimum transit time t2 can be determined by MTT−σ2, wherein PH is a peak height and MTT is a mean transit time of a tissue transport function he(t) in said tissue, wherein he(t) is derived from said Re(t), wherein he(t)=−dRe(t)/dt;
- h. using an iterative least squares method to fit the said simulated Cs(t) to said measured tissue curve C(t) with four adjustable parameters (Ft, t1, t2 and σ2);
- i. using a model-free deconvolution method to estimate starting values of said adjustable parameters for said iterative least squares fitting process in order to derive optimized values of said adjustable parameters;
- and
- j. calculating perfusion indices from the said optimized values of the adjustable parameters.
Dependencies are inferred from the claim text.