Quantitative blood flow measurements in the small animal cardiopulmonary system using digital subtraction angiography
(a) Schematic drawing showing the catheter locations for contrast delivery (injection catheter), temperature measurement, and Fick’s blood. (b) DSA image shows verification of the mixed venous blood sampling catheter position.
Thermodilution and x-ray DSA catheters. The injection catheter (a) delivered warmed contrast agent, and the distal temperature sensor catheter (b) measured the change in temperature downstream from the injection site.
A plot of the time density curve (right, axis) and the thermal dilution (left, axis) measure shows the coincidence of the two. The letters (a, g, h, and i) refer to the DSA x-ray series seen in Fig. 4 at specific time points during the run.
Selected DSA images show (a) initial arrival of contrast in the right ventricle, (b) filling of the pulmonary arterial system, (c) early to (d) midfilling of the parenchyma, (e) complete parenchymal filling, (f) pulmonary veins and early left heart filling, (g) left ventricle filling and early aorta enhancement, (h) complete aorta filling, and (i) contrast has passed through cardiopulmonary system. Note that the bolus is sufficiently compact that the different stages of flow can be temporally isolated. The ROIs (circles) in (b) show the AIF and in (h) show the aorta, which are used for the blood metric calculations.
A flow phantom was used to verify the SVD-based flow calculations between three vessels of differing diameters (, , and ). Tube A was the AIF.
Time density curves of the same rat in Fig. 4 showing signal changes at specific regions over time. The same types of time density curves are measured on a pixel-by-pixel basis and are used to calculate the SVD-based flow metrics. AIF: Arterial input function; R.PA: Right pulmonary artery; L.PA: Left pulmonary artery; R.Lung: Right lung parenchyma; and L.Lung: Left lung parenchyma.
Peak DSA signal intensity in the right pulmonary artery, left ventricle, parenchyma, and aorta plotted versus injection volume. Linear fits yielded for all plots (, 0.97, 0.99, and 0.99 for aorta, parenchyma, left ventricle, and right pulmonary artery, respectively).
Peak DSA signal versus thickness of the pulmonary vessels and the heart (assumed as a large vessel) for 50, 100, and injections of contrast agent. Note the linearity of the fits, (, 0.94, and 0.94 for 50, 100, and injection volume, respectively).
Representative time density curves of the flow phantom at the AIF (tube A in Fig. 5) and the distal vessels (tubes B, C, and D). An external pump was used to deliver the same flow rate through the three tubing sizes.
(a) SVD-derived PBF, (b) pulmonary blood volume, and (c) MTT of the same rat on a pixel-by-pixel basis. There was rapid transit in the major vessels (arrow shows pulmonary artery) and longer transit time in the more distal locations (circles indicate lung parenchyma).
Flow metric results for the phantom experiment before and after vessel thickness correction. There was statistically significant precorrection difference between tubes B and C ( value ) and tubes D and C ( value ). The prethickness corrected pulmonary blood flow values increased with an increase in tube diameter even though the same pump rate was used. No statistically significant difference was noted after the thickness correction between tubes B and C ( value ) and tubes D and C ( value ), an indication that matches the reality of the pump being operated at the same rate for all three tubes. In addition, there was no statistically significant difference ( value ) before and after the thickness correction for tube C because the scaling was to itself. Four DSA runs were made for each tube size.
Measured and calculated values of CO using Fick’s method, thermodilution, and x-ray DSA arranged in two groups—the distal temperature sensor in the DA and AA. Ten thermodilution samples and ten x-ray DSA sequences were acquired for each rat.
Average mean transit times at specific regions of interest for all rats in this study.
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