Preparation and evaluation of a 99mTc-SnF2 colloid kit for leukocyte labeling.

Stannous fluoride colloid (SFC) kits for instant radiolabeling with 99mTc were prepared and evaluated for suitability as a leukocyte radiolabeling agent. Technetium-99m labeling for kits stored at -15 degrees C for up to 3 mo was greater than 95% as determined by instant thin layer chromatography while colloid particles of 1-3 microns were measured by electron microscope for these preparations. Canine leukocyte preparations labeled with [99mTc]SFC and characterized by triple density gradients of metrizamide in plasma demonstrated an 83% leukocyte association. Analysis of labeled cell preparation for up to 3 hr demonstrated label stability. Labeled leukocytes, when readministered in normal dogs, demonstrated bi-exponential blood clearance with uptake and subsequent clearance from lung. There was increasing uptake of labeled leukocytes by the liver until steady state was achieved. Furthermore, when whole blood samples were analyzed by the triple density gradient method, an increasing monocyte-to-granulocyte ratio was observed to occur with time. By 3 hr 95% of the whole blood activity was associated with the leukocyte fraction. Dogs in which a 24-hr sterile abscess was created demonstrated elevated blood-pool activity as compared to control with localization of the labeled cells at inflammatory sites within 3 hr following cell readministration.

Effect of variation in heart size on quantitative thallium SPECT.

Quantitative single-photon emission tomographic (SPECT) thallium 201 (201Tl) cardiac studies are frequently used to improve test accuracy. One common technique uses polar mapping of relative tracer distribution to compare patient data to emplates from "normal" patient data. Commercial software does not correct for cardiac size variations. This study's purpose was to determine the effect of uncorrected variations in heart size on the variance of the normal population, which is the basis of template significance levels. Twenty-one male volunteers with low probability (less than 5%) for coronary disease underwent SPECT-Tl stress test. Data analysis with and without size correction was performed. Data were corrected for size by use of a three-dimensional compression/expansion algorithm. Quantitative data were generated by radial search to maximum activity in short-axis reconstructions. The mean activity and its variance was calculated from 288 points encompassing the myocardium. Mean and variance differences were analyzed by paired t test. There was no difference in activity means (pT greater than .9), indicating that size correction does not distort the data. The corrected data had, however, significantly lower variance (pT less than .0001). This shows that ventricular size variation contributes significantly to "normal" template variance and may adversely affect diagnostic accuracy in the absence of volume correction.

Radionuclide detection of abnormal ventricular filling patterns in rejecting human allografts.

Parameters of systolic and diastolic function obtained from radionuclide ventriculography (RNV) were evaluated in nine cardiac allograft recipients. In 25 examinations, left end-diastolic volume (LEDV), cardiac output (CO), left ejection fraction (LEF), right ejection fraction (REF), heart rate (HR), peak filling rate (PFR), time to peak filling rate (TPFR), peak ejection rate (PER), and average filling rate for the first half of diastole (DFRH) were determined. Endomyocardial biopsy was obtained within 48 hours. Biopsies were divided into three treatment classes (0 = normal; 1 = rejection but not requiring supplemental therapy; and 2 = rejection requiring supplemental immunotherapy). Two independent variables of diastolic function proved to be significant (DFRH P less than 0.00001, and PFR P less than 0.002) predictors of the dependent variable class when regression analysis was applied to the data. Alterations in diastolic function associated with acute rejection are detectable on RNV and simulate changes anticipated in a primary restrictive cardiomyopathy.