L. Pourcelot

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.

Non-invasive quantification of diaphragm kinetics using m-mode sonography.

PurposeThe standard conditions of spirometry (i.e., wearing a noseclip and breathing through a mouthpiece and a pneumotachograph) are likely to alter the ventilatory pattern. We used “time-motion” mode (M-mode) sonography to assess the changes in diaphragm kinetics induced by spirometry dunng quiet breathing.MethodsAn M-mode sonographic study of the nght diaphragm was performed before and dunng standard spirometry in eight patients without respiratory disease (age 34 to 68 yr).ResultsDuring spirometry, the diaphragm inspiratory amplitude (DIA) increased from 1.34 ± 0.18 cm to 1.80 ± 0.18 cm (P = 0.007), whereas the diaphragmatic mspiratory time (T1 diaph) increased from 1.27 ± 0.15 to 1.53 ± 0.23 sec, (P = 0.015), without change in diaphragmatic total time interval (Ttot diaph). Therefore, the diaphragm duty cycle (T1 diaph /Ttot diaph) increased from 38% ± 1% to 44% ± 4% (P = 0.023). The diaphragm inspiratory (DIV) and expiratory (DEV) motion velocity increased (P = 0.007).ConclusionM-mode sonography enabled us to demonstrate that the weanng of a nose clip and breathing through a mouthpiece and a pneumotachograph induce measurable changes in diaphragm kinetics.RésuméObjectifLes conditions de la spirométne standard (c.-à-d. le port du pince-nez et la respiration à travers un embout buccal et un pneumotacographe) sont susceptibles d’altérer la morphologie de la ventilation. Nous avons utilisé le mode «temps-amplitude» (mode M) de la sonographie pour évaluer les changements de la cinétique diaphragmatique provoqués par la spirométne pendant la respiration de repos.RésultatsPendant la spirométne, l’amplitude mspiratoire diaphragmatique augmentait de 1, 34 ± 0, 18 à 1, 80 ± 0, 18 cm (P = 0, 007), alors que le temps diaphragmatique mspiratoire (T1 diaph) augmentait de 1, 27 ± 0, 15 à 1, 53 ± 0, 23 sec (P = 0, 015), sans changement du temps diaphragmatique total (Ttot diaph). Par conséquent, le temps de l’activité diaphragmatique (T1 diaph/Ttot diaph) augmentait de 38 ± 1 % à 44 ± 4% (P = 0, 023). La vélocité de l’amplitude mspiratoire et expiratoire augmentait (P = 0, 007).ConclusionLa sonographie en mode M nous a permis de démontrer que le port du pince-nez et la respiration à travers un embout buccal et un pneumotacographe provoquent des changements tangibles de la cinétique diaphragmatique.

High-resolution real-time ultrasonic scanner

High spatial resolution is required for echographic exploration of the skin, microvessels or small laboratory animals. With the scanner described here, high resolution is obtained by means of a strongly focused, wide-band 17 MHz center frequency transducer (-6 dB bandwidth: 22 MHz). The movement of this transducer above the skin provides a 6 mm wide and 5 mm deep echographic cross-section with an image rate of 15 images/s. The resolution is about 0.08 mm in axial and 0.2 to 0.3 mm in lateral directions. The device was tested on phantoms in water and in vivo on normal and pathological skin in the Department of Dermatology. With the easy-to-handle probe, explorations were made on psoriasis, basocellular carcinoma, malignant melanoma and sarcoidosis.

MR assessment of the brain maturation during the perinatal period: quantitative T2 MR study in premature newborns

The purpose of our study is to trace in vivo and during the perinatal period, the brain maturation process with exhaustive measures of the T2 relaxation time values. We also compared regional myelination progress with variations of the relaxation time values and of brain signal. T2 relaxation times were measured in 7 healthy premature newborns at the post-conceptional age of 37 weeks, using a Carr-Purcell-Meiboom-Gill sequence (echo time 60 to 150 ms), on a 2.35 Tesla Spectro-Imaging MR system. A total of 62 measures were defined for each subject within the brain stem, the basal ganglia and the hemispheric gray and white matter. The mean and standard deviation of the T2 values were calculated for each location. Regional T2 values changes and brain signal variations were studied. In comparison to the adult ones, the T2 relaxation time values of both gray and white matter were highly prolonged and a reversed ratio between gray and white matter was found. The maturational phenomena might be regionally correlated with a T2 value shortening. Significant T2 variations in the brainstem (p < 0.02), the mesencephalon (p < 0.05), the thalami (p < 0.01), the lentiform nuclei (p < 0.01) and the caudate nuclei (p < 0.02) were observed at an earlier time than they were visible on T2-weighted images. In the cerebral hemispheres, T2 values increased from the occipital white matter to parietal, temporal and frontal white matter (p < 0.05) and in the frontal and occipital areas from periventricular to subcortical white matter (p < 0.01). Maturational progress was earlier and better displayed with T2 measurements and T2 mapping. During the perinatal period, the measurements and analysis of T2 values revealed brain regional differences not discernible with T2-weighted images. It might be a more sensitive indicator for assessment of brain maturation.

ULTRASOUND IMAGING OF PSORIATIC SKIN: A NONINVASIVE TECHNIQUE TO EVALUATE TREATMENT OF PSORIASIS

Background. The aim of our study was to image psoriasis plaques by ultrasound to assess the changes in psoriasis and to measure and quantify them objectively.

Blood Flow Response to Auditory Stimulations in Normal, Mentally Retarded, and Autistic Children: A Preliminary Transcranial Doppler Ultrasonographic Study of the Middle Cerebral Arteries

Using the noninvasive transcranial ultrasonic Doppler method, flow dynamics of the middle cerebral arteries were investigated in relation to auditory stimulations in 12 children with autistic behavior compared with 12 normal controls and 10 mentally retarded children. In normal children, auditory stimulation evoked lateralized modifications: blood flow increased and resistance index decreased on the left side; such modifications were not recorded on the right side. This pattern should indicate vasodilatation mechanisms induced by changes in the metabolism of the brain areas supplied by the left middle cerebral arteries (MCA). Although less asymmetrical, this pattern was also found in the mentally retarded children. Autistic children significantly differed from these two groups. They displayed a symmetric pattern of responses with a blood flow decrease and resistance-index increase on both sides; this could suggest abnormal metabolic mechanisms induced by auditory stimulation in autistic children and could be related to the previous hypothesis of impairment in the development of cerebral lateralization in autism. These preliminary results show that transcranial Doppler ultrasonography may be a valuable and practicable tool for the noninvasive study of evoked blood flow responses in psychopathology.

Effect of caffeine on cerebral blood flow velocity in preterm infants.

A continuous-wave form Doppler monitor was used to examine the effect of caffeine on cerebral blood flow velocity (CBFV) in 7 clinically stable preterm neonates suffering from apnea. Caffeine, in the form of caffeine citrate, or saline were given intravenously at loading doses of 20 mg/kg. Every subject was his own control. Placebo (saline) was systematically injected prior to caffeine citrate. Simultaneous recording of heart rate, arterial blood pressure, respiratory rate, TcPO2, TcPCO2 were made before, then at the end of the injection, and 30, 60 and 120 min after the end of each administration of either placebo or caffeine. Compared with placebo, caffeine injection was not associated with significant changes in CBFV. An increase was found in both heart-rate and respiratory rate (p less than 0.05). Mean arterial blood pressure, TcPCO2 and TcPO2 did not change significantly. Our data suggest that a caffeine citrate loading dose of 20 mg/kg as currently used at the beginning of treatment of apnea in preterm neonates has no effect on CBFV.

Comparison of MIBG and monoamines uptake mechanisms: Pharmacological animal and blood platelets studies

The uptake of MIBG, a scintigraphic agent widely used in the detection of APUD tumors, was studied with a pharmacological approach on an in vitro and an in vivo models. MIBG as well as norepinephrine (NE) was taken up by human blood platelets, a model for presynaptic nerve endings amine uptake, with a thermodependant mechanism. MIBG and NE uptake was inhibited by desimipramine and reserpine. However, MIBG but not NE uptake was inhibited by fluvoxamine, a serotonin (5HT) uptake inhibitor. This suggests that MIBG is a NE and also a 5HT uptake tracer which involves uptake one and vesicular storage mechanisms. In rats treated with 6-hydroxydopamine to induced a chemical sympathectomy, we observed an inhibition of uptake similar for MIBG and NE in the heart, the salivary glands and the spleen, but no effect was observed in the liver. Some clinical inferences to best investigate specific monoamine uptake are drawn from these results.

High-frequency estimation of the ultrasonic attenuation coefficient slope obtained in human skin: simulation and in vivo results.

In vivo ultrasonic characterization of the skin was performed at 40 MHz by estimating the slope of the attenuation coefficient in the human dermis. The centroid algorithm was first tested on simulated backscattered RF lines with a second-order autoregressive model to carry out the spectral analysis. A relative error of less than 8.5% and a relative precision of less than 6% were predicted for a 2-mm tissue thickness and for temporal window sizes ranging from 0.25 to 0.45 micros. In vivo measurements performed on 138 healthy volunteers yielded values of the attenuation coefficient slope ranging from 0.8 to 3.6 dB/cm MHz. A decrease was observed with advancing age, but no significant difference appeared between men and women. The results from this study suggest that this acoustic parameter shows the effect of the ageing process on normal skin tissue in vivo.

Effects of fetal and maternal breathing on the ultrasonic Doppler signal due to fetal heart movement.

Fetal heart rate (FHR) monitoring is widely used to evaluate fetal health and is based on the detection of movements of the fetal heart by Doppler ultrasound. Fetal health can also be evaluated by prolonged observation of body- and pseudo-respiratory movements using two-dimensional ultrasound. Fetal breathing movements are in particular considered to be an important indicator of fetal well being. Ultrasonic Doppler signals caused by movements of the fetal heart were analyzed in detail. The signals were acquired from five healthy fetuses. Minor changes in the insonification geometry gave rise to great variations in the aspects of successive heartbeats. The signals are shown to contain information on both maternal and fetal respiratory movements. This may facilitate the development of a simple method for fetal respiration monitoring coupled to standard FHR monitoring.