PULSED DOPPLER ULTRASONIC FLOWMETRY 
D. Y. Loisance, J. P. Lenriot and P. A. Peronneau* 
A pulsed ultrasonic velocimeter which permits pro- 
file analysis of the instantaneous and mean blood veloc- 
ity, has been used for the study of the portal and he- 
patic arterial blood flow in normal dogs and on a model 
of the human portal hypertension. Changes following 
the completion of a Side to Side Portacaval Shunt 
(SS-PCS) have been monitored. The directly measured 
volume flow value Ql and the value Q2 computed from 
the mean velocity profile have been compared. In normal 
dogs, after completion of the SS-PCS, the hepatic 
arterial flow Q2 was doubled but the flow pattern was 
unchanged. The portal vein flow rate Q2 was reduced 
and the velocity profile showed a bidirectional flow pat- 
tern. On the experimental model of portal hypertension, 
the hepatic arterial flow, already increased by the liga- 
tion of the supra-hepatic veins, was still increased to 
higher values after SS-PCS. The portal vein, down- 
stream from the shunt, was acting as an outflow tract 
for the liver. Comparative studies of the flow rate values 
i Ql and Q2 showed that the monitoring of the Ql value 
only can be misleading in complex flow patterns such 
as in the portal vein downstream from the SS-PCS. 
This experiment points out the necessity of a study of 
the blood flow pattern for an accurate assessment of the 
volume flow rate. 
INTRODUCTION** 
The qualitative study of the blood flow pat- 
tern in a vessel for an accurate measurement 
of the blood flow rate must be emphasized. Both 
techniques of instantaneous blood flow measure- 
ment, the electromagnetic and the ultrasonic 
flowmetry, require such an analysis.^ As a mat- 
ter of fact, the relation between the electro- 
i magnetic signal and the average blood velocity 
is linear only in the case of axially symmetri- 
cal flow pattern. The significance of the ultra- 
sonic signal, on the other hand, is difficult to 
assess because of the great number of different 
reflected echoes and the unknown direction of 
the velocity vector of every red cell.^ 
* Centre d'Etude des Techniques Chirurgicales (Head : Professeui- 
I J. P. Cachera), Hopital Bioussais, Paris. 
I ♦« Work done with support from la Delegation Generale a la 
I Recherche Scientifique et Technique (Paris). 
The pulsed Doppler ultrasonic velocimeter de- 
signed by P. Peronneau- permits blood flow 
studies of a qualitative (blood flow velocity 
profile) and quantitative (blood flow velocity 
and blood flow rate) nature. The description 
of the velocity profile in the portal vein and the 
hepatic artery of dogs in various experimental 
conditions is discussed here. 
EXPERIMENTATION 
Briefly, the basic principle of the device is as 
follows. A single crystal operates alternatively 
as transmitter and receiver. The ultrasonic 
emission is pulsed (frequency 8 MHz). In the 
interval between two pulses the crystal receives 
the echoes reflected from the vascular walls and 
the red cells. Consequently, the internal diam- 
eter of the vessel is measured and an electronic 
gate can select the reflection due to only the 
red cells at a given distance from the transducer 
and in a given volume of flow. 
The practical technique of the blood flow 
study is as follows. After setting the ultrasonic 
probe on the vessel, the internal diameter is 
measured. The instantaneous (V) and mean 
(V) velocities are measured according to two 
different techniques: 1. with the observation 
gate extended to encompass the entire internal 
diameter the average velocity Vd of the flow 
taken as a whole results. 2. by diminishing the 
width of the electronic gate to as little as .765 
millimeters, it is possible to scan from the near 
to the far wall of the vessel. This narrow gate 
selects the velocity signal Vi from a restricted 
area of the flow. The resultant figures establish 
the velocity profile. The volume flow rate is 
calculated in two different ways: 1. the flow 
value Ql as the product of the average velocity 
Vd and the section of the vessel defined by the 
measured internal diameter; 2. the flow value 
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