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Biomedical subjects

F Patat

Publications and source records attributed to F Patat.

52 records · Page 3Linked to original sources
PubMed1989

Very high frequency pulsed Doppler apparatus.

A study of a method for exploration of microvessels is presented. Theoretical considerations taking into account the backscattering of ultrasound wave from a red cell and the attenuation versus frequency (up to 180 MHz) show that a frequency in the range of 80 to 120 MHz is most favorable for small depths of exploration (300 microns). The characteristics of the 113 MHz Doppler system which was built are described. The minimum detectable signal is 3 microV, the lateral resolution around 20 microns and the minimum length of the Doppler sample volume about 80 microns. The Doppler data are displayed in the form of a frequency spectrum. The first encouraging tests carried out using 20 microns rectangular glass capillary tubes and 50 to 150 microns microvessels of the mesentery of rat have demonstrated the resolution and the sensitivity of the system. A discussion illustrates the difficult problem of motion artefacts and the improvements which have to be made. From a technical point of view the authors think that it is possible to work with such a high frequency but there are two main difficulties: the processing of a very low frequency Doppler spectrum and the optimization of the probe (dimensions and shape).

Animals↗
PubMed1987

A linear array system for deep vessel explorations.

A system for the exploration of deep vessels is proposed. This device is based on a single 300 element linear array in which a "Doppler area" is selected to electronically steer a Doppler beam. Characteristics of the equipment are excellent and it is as easy to handle as a simple linear array scanner. A real-time spectrum analyser is used to process the Doppler signals. The probe and the associated electronics are described and some results are given to illustrate the capabilities of the device such as blood flow estimation and deep vessel studies.

Aorta↗
PubMed1987

Exploration of the fetal cerebral blood flow by duplex Doppler--linear array system in normal and pathological pregnancies.

The umbilical circulation can be investigated by Doppler ultrasound techniques very easily. The Doppler frequency spectrum from the umbilical arteries provides information on the placental circulation. The diastolic flow amplitude is directly related to the vascular resistances of the placenta (Rp). In cases of pathological pregnancies with hypertension the decrease of the diastolic flow and the increase of the resistance index Rp have been correlated with intrauterine fetal growth retardation. Fetal cerebral arteries have also been explored during normal pregnancies (n = 40). The index of cerebral resistance (Rc) as defined by Pourcelot is Rc = S-D/S (with S systolic amplitude and D diastolic amplitude) and shows variations similar to the placental index. During normal pregnancy, the cerebral index is higher than the placental index and the cerebro-placental ratio (Rc/Rp) is greater than 1. This preliminary study of both umbilical and cerebral circulation seems to demonstrate that during pathological pregnancies with hypertension (n = 21), with fetal growth retardation one of the indices, Rc or Rp may be out of the normal range but the cerebro-placental ratio (CPR) is always less than 1. However a larger number of patients should be explored in order to evaluate the clinical usefulness of such an observation.

Cerebral Arteries↗
PubMed1987

[Doppler examination of the umbilical and cerebral arterial circulation of the fetus].

Umbilical circulation can be explored by Doppler ultrasound methods very easily. The umbilical arteries spectrum provides information on the placental circulation. The diastolic flow is directly related to the vascular resistances of the placenta (Rp). In cases of pathological pregnancies with hypertension the decrease in the diastolic flow and the increase in the resistance index Rp have been correlated with intra-uterine fetal growth retardation. The specificity of this index Rp is of 95% but the sensitivity much more lower (approximately 70%). For that reason Doppler assessment of the fetal circulation in other areas has been recently carried out. Fetal cerebral arteries have been explored during normal pregnancies. The index of cerebral resistances as defined by Pourcelot Rc = S-D divided by S (with S systolic amplitude and D diastolic amplitude) show similar variations to the placental index but later in the pregnancy. During the pregnancy the cerebral index is higher than the placental one and the cerebro placental ratio (CPR) superior to 1. During pathological pregnancy (hypertension) with fetal growth retardation one of the index Rc or Rp may be out of the normal range but the cerebro placental ratio CPR is always lower than 1. The follow up of both the umbilical and cerebral circulation increases notably the accuracy of the Doppler method for the detection of intra-uterine fetal growth retardation.

Cerebrovascular Circulation↗
PubMed1986

Cardiovascular system and microgravity simulation and inflight results.

Main results of cardiovascular investigation, performed with ultrasound methods during the common French/Soviet flight aboard Salyut VII in June 1982, are compared to variations of the same parameters studied during ground-based simulations on the same subject or observed by other investigators during various ground-based experiences. The antiorthostatic bed rest simulation partly reproduces microgravity conditions and seems to be better adaptated to cardiac hemodynamics, despite some differences, and to the cerebral circulation, than to the inferior limb circulation.

Aerospace Medicine↗
PubMed1984

[Evaluation of the degree of carotid stenosis by spectral analysis of the Doppler signal. Comparison of the results of spectral analysis, angiography and anatomo-pathology].

With the single Doppler spectrum analysis, one can appreciate the degree of the carotid stenosis according to the importance of the haemodynamic disturbances induced by the stenosis. The purpose of our study is to show the possibilities and the limitations of this method. Spectrum disturbances were classified in 5 grades, each of them being related to the importance of the stenosis. The degree of stenosis has been evaluated by the C.W. Doppler spectrum analysis, the angiographies and the anatomical study of the endarteriectomies. We considered that we had a perfect concordance between the results of the different methods when the degree of stenosis measured on the angiographies or on the endarteriectomies was compatible with the spectrum analysis classification: grade I: stenosis inferior to 40% (in area), 23% (in diameter); grade II: stenosis ranging between 40 and 60% in area (23 and 40 in diameter); grade III: stenosis of 60 to 75% in area (40 to 50% in diameter) and of particular shape (extended plaque); grade IV: stenosis ranging between 60 and 90% in area (40 to 70% in diameter); grade V: stenosis higher than 90% in area (70% in diameter). The confrontation of spectrum analysis and angiographic date concerns 58 bifurcations. We got a perfect correlation in 93% of the cases. The confrontation of the spectrum analysis method and the anatomical study of the endarteriectomies concerns 38 bifurcations. We got a perfect correlation in 92% of the cases. The appreciation of the carotid stenosis degree is now performed in routine at the Hospital. For some patients, the endarteriectomy has been decided from the clinical and the spectrum analysis data, and an electro-encephalogram with compression. However these date are generally completed with an angiography with venous punction.

Carotid Arteries↗