Selenomethionine (SeMet) is an important organic nutritional source of Se, but the uptake and metabolism of SeMet are poorly characterised in humans. Dynamic gamma camera images of the abdominal region were acquired from eight healthy young men after the ingestion of radioactive 75 Se-L-SeMet ( 75 Se-SeMet). Scanning started simultaneously to the ingestion of 75 Se-SeMet and lasted 120 min. We generated timeactivity curves from two-dimensional regions of interest in the stomach, small intestine and liver. During scanning, blood samples were collected at 10-min intervals to generate plasma time-activity curves. A four-compartment model, augmented with a delay between the liver and plasma, was fitted to individual participants' data. The mean rate constant for 75 Se-SeMet transport was 2·63 h -1 from the stomach to the small intestine, 13·2 h -1 from the small intestine to the liver, 0·261 h -1 from the liver to the plasma and 0·267 h -1 from the stomach to the plasma. The delay in the liver was 0·714 h. Gamma camera imaging provides data for use in compartmental modelling of 75 Se-SeMet absorption and metabolism in humans. In clinical settings, the obtained rate constants and the delay in the liver may be useful variables for quantifying reduced intestinal absorption capacity or liver function.Key words: Selenomethionine: 75 Se-L-selenomethionine: Absorption capacity: Metabolism: Gamma camera imaging: Compartmental modelling Selenomethionine (SeMet) is an important organic nutritional source of Se (1,2) . Absorption of various Se compounds occurs via different routes and mechanisms. Membrane transport of selenoamino acids, including SeMet, involves a specific suite of amino acid transporters (3) . The subsequent incorporation of dietary Se into selenoproteins occurs through a series of interconversions, of which many details remain unknown. Se metabolites are excreted in the urine and faeces and in exhaled air, mainly as selenosugars and methylated compounds (4) .The initial metabolism of Se in humans is poorly characterised. Estimates of Se absorption, whole-body retention and excretion have been made predominantly on whole-body counting (5) or the recovery of ingested tracers in the blood, urine and faeces (6) . Compartmental analyses of kinetic data from tracer studies have also been used to create a more integrated picture of whole-body Se utilisation in humans (7,8) . These studies characterised the long-term kinetics by the investigation of urine and faecal data collected over 12 d and blood samples drawn over 4 months. Through detailed mathematical modelling including several plasma pools, they were able to provide new insights into the long-run Se metabolism. However, because the study data only comprised hourly observations after dose administration, the initial Se kinetics could not be investigated and therefore still remained unclear. Our study tries to fill this gap and to provide deeper insight into the initial Se kinetics by focusing on frequent data collection within the first 2 h after a...

Se metabolism in humans is not well characterised. Currently, the estimates of Se absorption, whole-body retention and excretion are being obtained from balance and tracer studies. In the present study, we used gamma camera imaging to evaluate the whole-body retention and distribution of radiolabelled selenomethionine (SeMet), the predominant form of Se present in foods. A total of eight healthy young men participated in the study. Se]SeMet was retained within the body after 7 d. In contrast, the measured excretion in urine and faeces for the 7 d period was 8·2 (SD 1·1) % of the activity. Time -activity curves were generated for the whole body, stomach, liver, abdomen (other than the stomach and the liver), brain and femoral muscles. Gamma camera imaging allows for the assessment of the postprandial absorption of SeMet. This technique may also permit concurrent studies of organ turnover of SeMet.

DoseMapper is an easy to use implementation of the AAPM 108 Taskforce principles that allows for a rapid iterative design process of shielding in PET facilities, and the resulting maps of dose rate and annual accumulated dose serve as clear documentation for the design.