ABSTRACT
A new medical instrument is presented that produces a doppler blood flow image from a laser beam in a raster pattern and the results of a pilot study which shows this technique to be highly accurate in assessing burn depth is described.
Subject(s)
Burns/diagnosis , Laser-Doppler Flowmetry , Adolescent , Adult , Aged , Burns/pathology , Evaluation Studies as Topic , Female , Humans , Male , Middle Aged , Pilot ProjectsABSTRACT
A scanning laser-Doppler velocimeter, able to measure blood flux over a large area without contact with the skin surface, was used for the objective measurement of the vascular changes in psoriasis. Individual plaques were scanned, and tracings of the visible plaque edge taken on to a cellulose-acetate sheet from which area measurements were made using a digitizing tablet. Mean blood flux within plaques was increased fourfold compared with mean background flux. There was a highly significant linear correlation between plaque area measured by tracing and scanning, but area measured by scanning was greater. Detailed study of blood flux outside the visible plaque edge with the scanner, and with a conventional laser-Doppler instrument, showed this was due to a 2-4 mm rim of increased blood flux around plaques. The scanning laser-Doppler velocimeter allows rapid measurement of psoriasis in terms of mean blood flux and area of increased blood flux, and should be useful in the assessment of psoriasis severity and the response to treatment.
Subject(s)
Laser-Doppler Flowmetry/instrumentation , Psoriasis/diagnostic imaging , Skin/diagnostic imaging , Adolescent , Adult , Female , Humans , Male , Middle Aged , Psoriasis/physiopathology , Regional Blood Flow/physiology , Severity of Illness Index , Skin/blood supply , UltrasonographyABSTRACT
This paper describes a novel medical instrument that produces an image of blood flow in the capillaries under the skin surface. A laser beam is used to detect blood cell motion from the Doppler broadening of the laser light scattered from the skin. The image is generated by scanning the laser beam in a raster. The design of a practical clinical instrument is outlined and some preliminary results are presented.
Subject(s)
Diagnosis, Computer-Assisted , Lasers , Skin/blood supply , Blood Flow Velocity , Capillaries/diagnostic imaging , Equipment Design , Humans , Regional Blood Flow , Signal Processing, Computer-Assisted , UltrasonographyABSTRACT
Laser Doppler spectroscopy has been evaluated for the measurement of cerebral blood flow (CBF) by correlation with simultaneous measurements by radionuclide labelled microspheres. The experimental procedures were carried out on five anaesthetised rabbits. The cortical tissue was exposed by means of a small burr hole and illuminated by a helium neon laser (632.8 nm). Reflected light was detected using a silicon photodiode, and CBF was calculated continuously from the power of the frequency weighted Doppler spectrum in the reflected light. Three successive measurements of CBF were made using the microsphere technique. Following an initial baseline measurement, CBF was increased by an infusion of metaraminol and then reduced by controlled haemorrhage. Laser Doppler spectroscopy provided continuous monitoring of blood flow fluctuations and during the haemorrhage it was possible to demonstrate CBF autoregulation until the mean blood pressure fell below 6.7 kPa (50 mmHg). A regression analysis was performed between the simultaneous CBF measurements from the two techniques using a least squares best fit straight line analysis (r = 0.92, P less than 0.001). It was concluded that the flow computed from laser Doppler spectroscopy varied linearly with CBF and offers the unique advantage of continuous and instantaneous measurements even during nonsteady state flow.
