The clinical measurement of skeletal blood flow

1. A new method for measurement of skeletal blood flow is described which depends on the complete extraction of 18F in a single passage through bone. 2. Plasma concentration and urinary excretion are measured over a 2 h period. The technique of impulse analysis is used to determine the initial transfer rate of 18F to bone and extravascular extracellular fluid (ECF). The ECF component is evaluated by using a second tracer (51 Cr-EDTA or 82Br) and the bone transfer rate obtained by difference. The 51Cr-EDTA data also provide an estimate of glomerular filtration rate and enable a correction to be applied for urinary bladder retention when necessary. 3. Duplicate measurements of skeletal blood flow in eight normal male volunteers gave mean flows between 4-4 and 5-9% of blood volume/min, or about 4 ml min-1 100 g-1 of bone. The variation between normal subjects was least when the results were expressed as % of blood volume/min rather than ml/min, ml min-1 kg-1 or ml min-1 1-73 m-2 body surface area. The precision of the technique was estimated to be 16-4%. 4. Addition of 1-5% random noise to the input data resulted in an uncertainty of 8-5% in the measurement of skeletal blood flow, suggesting that improved precision depends on closer control of physiological variables. 5. In six patients with severe untreated Paget's disease of bone, skeletal blood flow was 8-4-15-3% of blood volume/min. The increase was significant in all cases. 6. The absorbed radiation dose is low, so that the measurement can be repeated.