A non-invasive isotope dilution technique for quantifying hepatic blood flow using radiolabelled red blood cells

Abstract

Clinically significant changes in hepatic haemodynamics accompany the development of portal hypertension, hepatocellular carcinoma, liver metastases and liver cirrhoses, and after major liver resection. Hepatic blood flow parameters, such as hepatic arterial flow (HAF), hepatic portal flow (HPF), total hepatic blood flow (THBF) and hepatic perfusion index (HPI), are useful adjuncts to the diagnosis of liver pathology, the evaluation of disease progress and prognostication. Here, we describe a non-invasive method that combines the measurement of these parameters in a single study in real time. Red blood cells from eight pigs were labelled with 99Tc(m) using an in-vitro method and re-injected into the pigs. Data acquisition over the heart, lungs, liver and kidneys was started immediately and a blood sample was obtained 15 min post-injection. Hepatic arterial flow was determined from the ratio of the maximum gradients between the integrated time-activity curve of the left ventricle and the first-pass time-activity curve of the liver before the peak of the kidneys time-activity curve. The hepatic perfusion index was determined by comparing the slope of the liver time-activity curve before and after the kidney peak. Hepatic portal flow was determined from the hepatic arterial flow and the hepatic perfusion index, and total hepatic blood flow was determined as the sum of arterial and portal flow. The results were compared against those obtained from a clearance method using 99Tc(m)-DISIDA. The average hepatic perfusion index was 0.38, and the average hepatic arterial flow and hepatic portal flow were 168.3 +/- 52.9 and 274.6 +/- 60.1 ml x min(-1) respectively. The average total hepatic blood flow was 442.8 +/- 53.5 ml x min(-1), while the total hepatic flow determined by 99Tc(m)-DISIDA clearance was 419.7 +/- 62.6 ml x min(-1). No significant difference in total hepatic blood flow was found between the two methods. The results of this study show that it is possible to obtain all hepatic haemodynamics data in a single study using a non-invasive method.

Changes in prostaglandin and nitric oxide levels in the hyperdynamic circulation following liver resection

“…Hepatic blood flow in the experimental animals was measured by a gamma camera (GE Starcam, General Electric Medical Systems, Milwaukee, WI, USA) technique previously validated at the Department of Experimental Surgery, Singapore General Hospital. 13 This was carried out with the animals under anaesthesia just prior to laparotomy on three separate occasions; before laparotomy for hepatic resection (pre‐op. ), on the first postoperative day (24 h post‐op.)…”

“…The technique of measuring blood flow utilized technetium‐labelled red blood cells ([ 99m Tc]RBC) as a non‐diffusible intravascular tracer. 13 Red blood cells obtained from the pigs were labelled with [ 99m Tc] by using an in vitro method and then re‐injected into the pigs. Data acquisition over the heart, lungs, liver and kidneys was started immediately using a GE Starcam (General Electric Systems, Milwaukee, WI, USA) small field‐of‐view gamma camera and a blood sample was obtained at 15 min post‐injection.…”

Different methods for hepatic flow measurements: a narrative review

“…Radionuclides can also be bound to colloids and delivered intravenously, with blood flow calculated using the Fick principle. 99mTc is the most commonly used radionuclide for this method [63][64][65][66][67][68] .…”