METHODS OF MEASURING BLOOD FLOW 



1321 



at about 1000 frames per sec is used, the exposure of 

 each frame being 200 /usee. For evaluation, the 

 distance-time relation is plotted from the projected 

 film, and the time course of the velocity is obtained 

 by graphic differentiation. McDonald's work is of 

 particular significance regarding hemodynamics be- 

 cause his simultaneous recordings of the pressure 

 gradient make possible hydrodynamic flow calcula- 

 tions and comparison of the calculated flow pattern 

 with that determined by cinematography. 



MISCELLANEOUS METHODS 



Rockemann (114) tried to measure the blood 

 velocity by means of electrolytic polarization taking 

 place at electrode surfaces which are in contact with 

 the streaming blood. A stable calibration, however, is 

 not obtainable for this method. 



The application of nuclear magnetic resonance to 

 blood flow measurements was described almost simul- 

 taneously by Buchman and by Singer in 1959. Buch- 

 man's device (17) passes protons, the spin axes of 

 which have been aligned, through a varying magnetic 

 field. Energy is required to bring them into resonance. 

 Thus the absorbed energy is a measure of the number 

 of protons passing per time unit, and hence, is propor- 

 tional to the flow rate. Singer (124) uses several 

 methods based on nuclear magnetic resonance. In 

 one of the procedures, the nuclear relaxation time of 

 the protons in the water of streaming blood is meas- 

 ured and compared with the relaxation time of 

 those in stopped blood; only single determinations of 

 relative values are obtained. By another procedure 

 described by Singer, absolute flow velocities can be 

 recorded at short time intervals. The nuclei are per- 

 turbed by the 60 mc per sec field of a transmitter coil, 

 and the time required by the nuclei to reach a second 



detecting coil is measured. Singer also considers 

 nuclear or electron magnetic resonance as a tracer 

 detection system. It seems worthwhile to carry on the 

 development of these methods since they are appli- 

 cable to unopened vessels, even from outside through 

 the intact skin. 



ADDENDUM 



Since completion of the manuscript, several papers have 

 been published which should be referred to: 



Elliott, S. E., J. I. E. Hoffman, and A. Guz. An electro- 

 magnetic flowmeter for simultaneous measurement of ventric- 

 ular ejection in the conscious animal. Digest of 4th Intern. Conf. 

 Med. Electronics, New York, 1961, p. 150. Coreless electro- 

 magnetic flowmeter units were implanted around the ascending 

 aorta and pulmonary artery of the dog. A-c sine-wave type, 

 400 cps. Some magnetic interference between both units was 

 observed. 



Yanof, H. M. A New Trapezoidal-wave Electromagnetic 

 Blood Flowmeter and Its Application to the Study of Blood 

 Flow in the Dog (Ph.D. thesis). Berkeley: Univ. of California, 

 iq6o. Description of circuitry. 1000 cps. Adjustment of mini- 

 mum transformer emf by an additional ferrite slug. 



Wyatt, D. G. Problems in the measurement of blood flow 

 by magnetic induction. Phys. in Med. Biol. 5: 289, 1961. Thor- 

 ough examination of performance, and possible error sources 

 in the application, of electromagnetic flowmeters. 



Zarnstorff, W. C, and C. A. Castillo. An ultrasonic flow- 

 meter. Digest 0/ 4th Intern. Conf. on Med. Electronics, New York, 

 1 96 1, p. 86. Stable phase-difference device appropriate for 

 recording of blood How in unopened arteries. 



Franklin, D. L., D. W. Baker, and R. F. Rushmer. Pulsed 

 ultrasonic transit time flowmeter. IRE Trans, on Bio-Med. 

 Electronics BME-g, 44, 1962. Diagrams of electronic circuitry. 



Higasi, K. (ed.). Platinum blood flowmeter. Research Inst. 

 Appl. Elec, Hokkaido Univ., Monograph Ser. No. 10, 1962. Con- 

 tains several papers by M. Mochizuki and co-workers on the 

 relation between polarographic current for oxygen and the flow 

 velocity. Application to flow measurement in arteries. Catheter- 

 tip method. Calibration curve concave to flow abscissa at low 

 velocities and linear at higher velocities. 



REFERENCES 



1 . Abel, F. L. Chopper -operated electromagnetic flowmeter. 

 IRE Trans, on Med. Electronics ME-6: 216, 1 959. 



2. Anschutz, F., and F. Heuck. Uber die durch Aorten- 

 sklerose verursachten Veranderungen der arteriellen 

 Blutstrbmung. Z. Kreislauforsch. 49 : 1 20, 1 960. 



3. Barnes, C. W. A new method for obtaining How signals 

 from the electromagnetic flowmeter. Naturwissenschaften 

 47: 56, i960. 



4. Baxter, I. G, and J. W. Pearce. Simultaneous measure- 

 ment of pulmonary artery flow and pressure using 

 condenser manometers. J. Physiol., London 115: 410, 1 951 - 



5. Bergmann, G. Die "Stromborste", ein elektrischer Ge- 

 schwindigkeitsmesser fur Fliissigkeiten. (2. Mitteil.) Z. 

 Biol. 98: 536, 1938. 



6. Betticher, A., J. Maillard, and A. Muller. Un mano- 

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 alimente sur le reseau alternatif, pour mesurer la vitesse 

 d'ecoulement dans des tuyeaux et des vaisseaux sanguins. 

 Helv. Physiol, et Pharmacol. Acta 12: 112, 1954. 



7. Bohme, W. Uber den aktiven Anteil des Herzens an der 

 Forderung des Venenblutes. Ergeb. Physiol. 38: 251, 1936. 

 Eortschr. Rontg. Sir. 57: 59, 1938. 



