Limits...
Estimation of coronary artery hyperemic blood flow based on arterial lumen volume using angiographic images.

Molloi S, Chalyan D, Le H, Wong JT - Int J Cardiovasc Imaging (2011)

Bottom Line: Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V(3/4) (r = 0.98, SEE = 10.59 ml/min).The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min).This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiological Sciences, University of California, Medical Sciences B, B-140, Irvine, CA 92697, USA. symolloi@uci.edu

ABSTRACT
The purpose of this study is to develop a method to estimate the hyperemic blood flow in a coronary artery using the sum of the distal lumen volumes in a swine animal model. The limitations of visually assessing coronary artery disease are well known. These limitations are particularly important in intermediate coronary lesions where it is difficult to determine whether a particular lesion is the cause of ischemia. Therefore, a functional measure of stenosis severity is needed using angiographic image data. Coronary arteriography was performed in 10 swine (Yorkshire, 25-35 kg) after power injection of contrast material into the left main coronary artery. A densitometry technique was used to quantify regional flow and lumen volume in vivo after inducing hyperemia. Additionally, 3 swine hearts were casted and imaged post-mortem using cone-beam CT to obtain the lumen volume and the arterial length of corresponding coronary arteries. Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V(3/4) (r = 0.98, SEE = 10.59 ml/min). The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min). These results indicate that measured arterial branch lengths or lumen volumes can potentially be used to predict the expected hyperemic flow in an arterial tree. This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data.

Show MeSH

Related in: MedlinePlus

Image of the calibration phantom is shown (a) along with an example of a calibration curve showing the relationship between iodine mass (mg) and measured integrated gray levels (b)
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3094746&req=5

Fig2: Image of the calibration phantom is shown (a) along with an example of a calibration curve showing the relationship between iodine mass (mg) and measured integrated gray levels (b)

Mentions: Coronary artery lumen volume can be measured using densitometry [17]. System calibration is required to quantify the iodine mass from the densitometry signal [15, 35]. An iodine calibration phantom, containing known amounts of iodine, was imaged over the heart region of each swine. The calibration phantom consisted of a series of rods each containing contrast material with diameters ranging from 0.76 to 3.35 mm and iodine masses ranging from 7.66 to 112.04 mg (see Fig. 2a). The iodine concentration in the calibration phantom was approximately the same as the undiluted contrast material (350 mg/ml). Correction for the magnification difference between the coronary arteries and the calibration phantom was performed by accounting for their distances from the X-ray source. After logarithmic transformation followed by phase-matched subtraction, the integrated gray level (G) inside the region of interest (ROI) was directly converted to arterial volume using the following equation:5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{V}} = {\text{G}}{\frac{{{\text{F}}_{\text{M}} }}{\text{C}}} $$\end{document}where FM is the integrated gray level to iodine mass conversion factor, and C is the iodine concentration of the bolus entering the arteries of interest. The iodine concentration inside the opacified arteries was assumed to be the same as that of the injected contrast material. This assumption stems from the protocol where contrast material was injected at a rate in which it completely replaces blood entering the coronary arteries [15, 16]. Using the acquired image of the calibration phantom, FM was determined from the slope (ΔM/ΔG) of the regression line that correlates the known iodine masses (M) with the measured integrated gray levels (G) (see Fig. 2b). A correction for the magnification differences between the heart and the calibration phantom placed on the pig’s thorax was also required. The expression for FM is6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{F}}_{\text{M}} = {\frac{{\Updelta {\text{M}}}}{{\Updelta {\text{G}}}}}{\frac{{{\text{D}}_{\text{H}}^{2} }}{{{\text{D}}_{\text{C}}^{2} }}}, $$\end{document}where DH is the X-ray source-to-heart distance and DC is the source-to-calibration distance. DC was determined from an image of the 4 markers on the calibration phantom. DH was assumed to be less than DC by 5 cm, which was the approximate distance from the heart to the sternum and the left side of the chest wall.Fig. 2


Estimation of coronary artery hyperemic blood flow based on arterial lumen volume using angiographic images.

Molloi S, Chalyan D, Le H, Wong JT - Int J Cardiovasc Imaging (2011)

Image of the calibration phantom is shown (a) along with an example of a calibration curve showing the relationship between iodine mass (mg) and measured integrated gray levels (b)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3094746&req=5

Fig2: Image of the calibration phantom is shown (a) along with an example of a calibration curve showing the relationship between iodine mass (mg) and measured integrated gray levels (b)
Mentions: Coronary artery lumen volume can be measured using densitometry [17]. System calibration is required to quantify the iodine mass from the densitometry signal [15, 35]. An iodine calibration phantom, containing known amounts of iodine, was imaged over the heart region of each swine. The calibration phantom consisted of a series of rods each containing contrast material with diameters ranging from 0.76 to 3.35 mm and iodine masses ranging from 7.66 to 112.04 mg (see Fig. 2a). The iodine concentration in the calibration phantom was approximately the same as the undiluted contrast material (350 mg/ml). Correction for the magnification difference between the coronary arteries and the calibration phantom was performed by accounting for their distances from the X-ray source. After logarithmic transformation followed by phase-matched subtraction, the integrated gray level (G) inside the region of interest (ROI) was directly converted to arterial volume using the following equation:5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{V}} = {\text{G}}{\frac{{{\text{F}}_{\text{M}} }}{\text{C}}} $$\end{document}where FM is the integrated gray level to iodine mass conversion factor, and C is the iodine concentration of the bolus entering the arteries of interest. The iodine concentration inside the opacified arteries was assumed to be the same as that of the injected contrast material. This assumption stems from the protocol where contrast material was injected at a rate in which it completely replaces blood entering the coronary arteries [15, 16]. Using the acquired image of the calibration phantom, FM was determined from the slope (ΔM/ΔG) of the regression line that correlates the known iodine masses (M) with the measured integrated gray levels (G) (see Fig. 2b). A correction for the magnification differences between the heart and the calibration phantom placed on the pig’s thorax was also required. The expression for FM is6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{F}}_{\text{M}} = {\frac{{\Updelta {\text{M}}}}{{\Updelta {\text{G}}}}}{\frac{{{\text{D}}_{\text{H}}^{2} }}{{{\text{D}}_{\text{C}}^{2} }}}, $$\end{document}where DH is the X-ray source-to-heart distance and DC is the source-to-calibration distance. DC was determined from an image of the 4 markers on the calibration phantom. DH was assumed to be less than DC by 5 cm, which was the approximate distance from the heart to the sternum and the left side of the chest wall.Fig. 2

Bottom Line: Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V(3/4) (r = 0.98, SEE = 10.59 ml/min).The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min).This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiological Sciences, University of California, Medical Sciences B, B-140, Irvine, CA 92697, USA. symolloi@uci.edu

ABSTRACT
The purpose of this study is to develop a method to estimate the hyperemic blood flow in a coronary artery using the sum of the distal lumen volumes in a swine animal model. The limitations of visually assessing coronary artery disease are well known. These limitations are particularly important in intermediate coronary lesions where it is difficult to determine whether a particular lesion is the cause of ischemia. Therefore, a functional measure of stenosis severity is needed using angiographic image data. Coronary arteriography was performed in 10 swine (Yorkshire, 25-35 kg) after power injection of contrast material into the left main coronary artery. A densitometry technique was used to quantify regional flow and lumen volume in vivo after inducing hyperemia. Additionally, 3 swine hearts were casted and imaged post-mortem using cone-beam CT to obtain the lumen volume and the arterial length of corresponding coronary arteries. Using densitometry, the results showed that the stem hyperemic flow (Q) and the associated crown lumen volume (V) were related by Q = 159.08 V(3/4) (r = 0.98, SEE = 10.59 ml/min). The stem hyperemic flow and the associated crown length (L) using cone-beam CT were related by Q = 2.89 L (r = 0.99, SEE = 8.72 ml/min). These results indicate that measured arterial branch lengths or lumen volumes can potentially be used to predict the expected hyperemic flow in an arterial tree. This, in conjunction with measured hyperemic flow in the presence of a stenosis, could be used to predict fractional flow reserve based entirely on angiographic data.

Show MeSH
Related in: MedlinePlus