Non-invasive measurement of renal blood flow with 99mTc DTP A: comparison with radiolabeled microspheres

Abstract

This technique for non-invasive measurement of renal blood flow is based on the principle of fractionation of cardiac output, and applicable with any recirculating gamma activity tracer. It effectively determines the count rate that would be recorded over the kidney if the tracer behaved like radiolabelled microspheres and was completely trapped in the kidney on first pass. After correction for kidney depth, the estimated first pass activity plateau, expressed as a fraction of the injected dose, is equal to the kidney's fraction of cardiac output. The principle of the technique was validated by comparison with renal blood flow based on radiolabelled microspheres. Nine separate comparisons were made in two anaesthetised dogs. A known dose of 99mTc radiolabelled microspheres (particle size 23-45 microns) was injected into the left ventricle and the count rate over each kidney recorded. A known dose of 99mTc diethylenetriaminepenta acetic acid (DTPA) was then given as an intravenous bolus and the data recorded dynamically with a gamma camera online to a computer. After subtraction of the stable signal arising from the preceding radiolabelled microspheres, the theoretical first pass activity plateau from the DTPA that would have been recorded if the DTPA, after reaching the systemic circulation, had behaved like radiolabelled microspheres and become completely trapped in the renal vascular bed, was estimated. Using doses based on syringe counts before and after injection the ratio of renal blood flow values given by the two techniques (DTPA:RLMS) was 1.14 (SD 0.22) for the left kidney and 1.1(0.17) for the right. Using doses based on whole body counts, corresponding ratios were 1.05(0.11) and 1.02(0.13).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of flow measurement from the first pass bolusT1weighted images using inversion recovery sequence

“…Peters et al [22,23] have described a method for calculating blood flow from first-pass radionuclide studies based on the microsphere technique [8]. It is the gold standard for blood flow measurements in animal studies [7].…”

“…This technique is mathematically simple, requires no complex numerical analysis such as deconvolution and can be added to routine isotope renography. They used the technique to measure blood flow in the spleen and brain [21][22][23].…”

Filtration Fraction · Noninvasive Measurement with Tc-99m DTPA and Changes Induced by Angiotensin-Converting Enzyme Inhibition in Hypertension

“…A known dose of Tc-99 m DTPA was given by bolus intravenous injection as previously described [1,2] with the patient supine above a large field of view gamma camera (1G E 400A or 400T) fitted with a low energy collimator and interfaced to a computer(MDS A2). Data were acquired on computer dynamically with a frame rate of l/s for 40s (first pass or flow phase) and then l/20s for 5 min (filtration phase).…”

“…Data Analysis RBF/CO was calculated from the first pass Tc-99 m DTPA time activity curves as previously described [1,2]. In this technique, the arterial blood curve is corrected for recirculation, by a standard gamma variate fitting procedure, and then used to predict the count rate (H) that would have been achieved in a region of interest over the kidney if all theTc-99m DTPA arriving in the kidney on first pass was trapped there.…”

“…We recently described a noninvasive method using Tc-99m DTPA for measuring the fraction of the cardiac output (CO) serving the kidney (RBF/CO) [l] and vali dated it in a canine model [2], By extending the theory, we derived a technique for 'directly' measuring FF, not only in each kidney, but also potentially on a regional basis within each kidney, without the need for blood sampling [l].…”