Correlation of Laser Doppler Flowmetry with Microsphere Estimates for Bone Blood Flow

Abstract

Due to the mineralization of bone and the multiplicity and complexity of the arterial and venous system, experimental analysis of factors influencing the development of numerous orthopedic problems has been seriously affected by the lack of a direct method for assessing bone blood flow [6]. The laser Doppler flowmetry (LDF) method has been refined by Bonner et al. [1], Holloway and Watkins [2], and Nilsson et al. [3]. Holloway and Watkins developed an instrument with optical fibers and a photodiode in the detection unit, the single-channel system (Medpacific, LD 5000, Seattle, Washington) [2]. They reported technical problems with “mode competition producing a beat frequency which sweeps through the sampling band width” which limited the measurement time. Nilsson et al. solved this problem with a double-channel detection system (Periflux Pf2, Perimed, Stockholm, Sweden) using larger optical fibers, which resulted in an improved signal-to-noise ratio [3]. The photodetectors and signal processor were designed to give a linear response for low and moderate cell velocities, and more recently have been improved to include higher velocities. The authors have previously reported the utility of LDF in experimental and clinical bone blood flow measurements [4, 5]. In these earlier studies, the strength of correlation of the preliminary LDF/microsphere experiments was limited by the number of microspheres which could be injected into the rabbit ventricle before producing systemic hypotension [5].

This work was supported by BRSG grant RR-05424.