Flow and diffusion in the myocardium: modelling of the convection- diffusion interrelationships governing the use of solute washout for estimating blood flow

Conference · Mon Jan 01 00:00:00 EST 1973

OSTI ID:4383312

Bassingthwaighte, J B; Knopp, T J; Yipintsoi, T; McClain, W J; Maskewitz, B F

From 3rd symposium on sharing of computer programs and technology in nuclear medicine; Miami, Florida, USA (16 Jun 1973). In proceedings of third symposium on sharing of computer programs and technology in nuclear medicine. A broad conceptual approach to the investigation of passive transcapillary exchanges is described, and illustrated by experiments on isolated blood-perfused dog hearts. Tracers were injected into the coronary inflow; responses recorded were either concentration-time curves in the coronary effluent or, for gammaemitting tracers, residue function curves using detectors over the heart. Firstly, a region of flow-limited exchange is demonstrated when the curves recorded for a specific tracer are similar in shape at different flows, F; i.e., the fractional escape rate or clearance at a particular level on the residue function curve is directly proportional to F. Similarity occurred for albumin- bound indocyanine green dye, remaining intravascular, and for /sup 125/I- antipyrine, distributed throughout tissue water, over a 3-fold range of flows. In a region where the ratio of convective velocity (flow) to diffusive velocity (permeability = D/sub R/ = diffusivity radially from the flow stream) is higher, then the extraction of intravascular sodium or other partially permeability- limited solutes diminishes at higher flows, so that curves at different flows are dissimilar. At still higher ratios, radial diffusivity is the sole limitation. At lower flows, or with rapidly diffusible tracers longitudinal diffusion, D/sub L/, from inflow to outflow, or counter-current exchange, is significant relative to flow. After intraarterial injection, particularly at low flows, highly diffusible heat, /sup 133/Xe, and THO have abnormally high early escape rates indicating diffusional shunting, and correspondingly low rates late on the washed out curve. In the lowest flow regime, where diffusion is relatively so rapid that tracer concentration throughout the organ is uniform, washout would be monoexponential; this region apparently does not exist at flows compatible with viability. For the estimation of flow, indicator washout curves should show similarity. (auth)

• Research Organization: Mayo Graduate School of Medicine, Rochester, MN; comps.; Oak Ridge National Lab., Tenn. (USA)
• NSA Number: NSA-29-008106
• OSTI ID: 4383312
• Report Number(s): CONF-730627-
• Resource Relation: Conference: 3. symposium on sharing of computer programs and technology in nuclear medicine, Miami, Florida, USA, 16 Jun 1973; Other Information: Orig. Receipt Date: 30-JUN-74; Related Information: Proceedings of third symposium on sharing of computer programs and technology in nuclear medicine
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

N48830* -Life Sciences-New Tracer Techniques-Other
*BLOOD FLOW- TRACER TECHNIQUES
*HEART- RADIOISOTOPE SCANNING
BLOOD CIRCULATION
CAPILLARIES
DIAGNOSTIC TECHNIQUES
DOGS
INJECTION
IODINE 125
LABELLED COMPOUNDS
MUSCLES
NUCLEAR MEDICINE
RADIONUCLIDE ADMINISTRATION
TISSUE DISTRIBUTION
TRITIUM
XENON 133 TISSUE DISTRIBUTION