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Abstract #5289 Published in IGR 1-2
Mechanical fundus-perfusion model: blood-flow velocity determined with Heidelberg Retina Flowmetry (HRF) and digital ICG angiography (HRA)
Hendrickson P; DeMel T; Peterson JCKlinische Monatsblätter für Augenheilkunde 1999; 214: 275-276
BACKGROUND: Heidelberg Retina Flowmetry (HRF) is now popularly, perhaps even indiscriminately, applied in eye research, without apparent concern for the fact that the results are given numerically, but without physical units. METHODS: 1) HRF: To challenge the HRF device with known values of blood-flow velocity, a perfusion chamber with input and output connection was constructed of acrylic plastic. Three serial segments were milled to provide cross-sectional areas (1.93 mm?, 3.33 mm?, and 5.08 mm?) and accordingly decreasing, true, clinically representative flow-velocity values. Under a constant perfusion setting of a calibrated clinical infusion pump (Perfusor Secura FT, B. Braun Medical AG, Sempach, CH), heparinized human blood (P.H.) was pumped through the chamber, and the HRF parameter, 'VELOCITY' was measured within one image encompassing the three chamber segments, using a 20 x 5? field and a 20 x 20 pixel measuring 'window'. 2) HRA: Immediately thereafter, our perfusion model was placed in front of the Heidelberg Retina Angiography device, the infusion pump started at the same constant level, and a 1 ml bolus of ICG dye added to the blood. Digital ICG angiography was then conducted, and the images analyzed on-screen. RESULTS: In the three segments of the perfusion chamber, flow velocities determined ICG-angiographically were 11.5 mm/sec, 6.7 mm/sec, and 4.4 mm/sec, respectively. The corresponding values for HRF 'VELOCITY' were 5.3, 4.2 and 3.4, respectively (no units). CONCLUSIONS: Under identical perfusion conditions, the phenomenologically (ICG-angiographically) determined values of flow velocity in the 3 perfusion chamber segments ran similar to (but not numerically coincidental with) those determined for HRF parameter 'VELOCITY'. Extrapolation of HRF values to true physical units is, thus, feasible. (German)
P. Hendrickson, Medizinische Fakultat Basel, Sommergasse 29, CH-4056, Basel; Switzerland
Classification:
6.11 Bloodflow measurements (Part of: 6 Clinical examination methods)