Tp. Fuerst et Ms. Vanlysel, MEASUREMENT OF ABSOLUTE BLOOD IODINE CONCENTRATION DURING DIGITAL SUBTRACTION VENTRICULOGRAPHY, Medical physics, 20(3), 1993, pp. 795-803
A system to measure the absolute iodine concentration (mg iodine/milli
liter blood) in the left ventricle (LV) during digital subtraction ven
triculography has been developed. The technique uses a catheter to dra
w blood from the LV through a detection cell. This occurs as the iodin
e bolus passes through the heart. The cell determines iodine concentra
tion by measuring x-ray attenuation as the iodinated blood passes betw
een a low-power x-ray tube and a diode detector. In vitro and in vivo
testing of the system was conducted. The system response was linear (r
= 0.99) with respect to iodine concentration. This response was indep
endent of hematocrit. Dispersion of contrast medium in the catheter ca
used distortion of the shape of the time-concentration curve. The impu
lse response of the system was measured and found to be independent of
hematocrit. A correction algorithm based on Wiener filter deconvoluti
on was developed. In vitro testing using simulated time-concentration
curves demonstrated that the rms error in the iodine measurement after
dispersion correction did not exceed 4% over the region of the time-c
oncentration curve extending from the peak to the point on the tail wh
ere the signal fell to 50% of its peak value. Cardiac output was measu
red from the time-concentration curve via the indicator-dilution metho
d in an animal model. This cardiac output measurement (CO(I)) agreed c
losely with cardiac output measured simultaneously with an aortic flow
probe (CO(P)), namely, CO(I) = 1.02 CO(P)-0.03 L/min, r = 0.95, SEE =
10%, p < 0.001. The application of the blood iodine concentration mea
surement to the densitometric measurement of absolute LV volume from d
igital subtraction angiography (DSA) images is discussed.