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Biomedical subjects

F Tranquart

Publications and source records attributed to F Tranquart.

At least 55 records · Page 3Linked to original sources
PubMed2000

[Non-linear ultrasound imaging].

The recent introduction of non-linear imaging in ultrasound diagnosis could improve image quality by resolving some problems in technically difficult patients allowing a better conspicuity in identification of subtle lesions. Tissue harmonics are generated while the transmitted pulse propagates through tissue. The formation of image by utilising the harmonic signals implies the suppression of fundamental frequency in the received signal. This is achieved by two major processes filtering and pulse inversion imaging. The non-linear properties of contrast agents reinforce the intensity of harmonic signals which could be detected in precise conditions of acoustic power for a non-destructive or destructive imaging. The introduction of this new imaging modality opens new way in ultrasound imaging with precise protocols of acquisition or sequences and possibly in therapy in the near future.

Contrast Media↗
PubMed1999

Right-to-left interatrial shunt in ARDS: dramatic improvement in prone position.

The mechanisms leading to shunting through a patent foramen ovale include high right-sided cardiac pressures and respiratory factors due to mechanical ventilation and also anatomical changes in the right atrium as described in the platypnea-orthodeoxia syndrome. We report a patient with the adult respiratory distress syndrome (ARDS) who had a right-to-left atrial shunt which decreased in the prone position, after which oxygenation improved. The patient was admitted to the intensive care unit because of ARDS due to an invasive fungal infection. He had a history of chronic lymphocytic leukemia and paradoxical embolisms through a patent foramen ovale. Despite mechanical ventilation and antifungal treatment he developed severe ARDS. He was therefore turned to the prone position. Blood gas values improved dramatically (arterial oxygen tension/fractional inspired oxygen ratio increasing from 59 to 278 torr). Transcranial Doppler sonography was performed with bubble study, which confirmed a massive right-to-left shunt in the supine position and which instantaneously decreased in the prone position. This case suggests that a decrease in right-to-left shunt in patients who have a patent foramen ovale could partly explain the improvement in hypoxemia in the prone position.

Aged↗
PubMed1999

Transplant renal artery stenosis: potential role of ischemia/reperfusion injury and long-term outcome following angioplasty.

PURPOSE: We assess long-term arterial pressure, renal function, and patient and graft survival in recipients of cadaveric kidney transplant with or without transplant renal artery stenosis. We also evaluate the risk factors for transplant renal artery stenosis. MATERIALS AND METHODS: We reviewed and analyzed baseline clinical, immunological and outcome data for 26 patients with transplant renal artery stenosis before and after angioplasty, and 72 without stenosis on angiography. We also analyzed graft and patient survival in 304 cases in which angiography was not performed. RESULTS: The incidence of transplant renal artery stenosis was 6.6% (26 of 402 patients). Acute rejection episodes (42 versus 22%, p <0.05) and delayed graft function (50 versus 32%, p <0.10) were more frequent, and mean cold ischemia time plus or minus standard error (29.2+/-1.7 versus 24.8+/-1.3 hours, p <0.01) was longer in patients with than without transplant renal artery stenosis. The technical success of angioplasty was 92.3%. Restenosis was documented in 6 of 26 patients (23.1%). Revascularization resulted in a decrease in arterial pressure and better renal function. The 8-year patient (100, 98.6 and 95.7%, respectively) and graft (88.1, 88.9 and 89.3%, respectively) actuarial survival rates were similar among patients with or without transplant renal artery stenosis, and those who did not undergo angiography. CONCLUSIONS: Transplant renal artery stenosis had no detectable influence on long-term arterial pressure control, renal function, and patient and graft survival rates, which were similar to those in patients without stenosis. Long cold ischemia time may have a role in the development of transplant renal artery stenosis through ischemia/reperfusion injury.

Adult↗
PubMed1999

Clinical use of ultrasound tissue harmonic imaging.

The recent introduction of tissue harmonic imaging could resolve the problems related to ultrasound in technically difficult patients by providing a marked improvement in image quality. Tissue harmonics are generated during the transmit phase of the pulse-echo cycle, that is, while the transmitted pulse propagates through tissue. Tissue harmonic images are formed by utilizing the harmonic signals that are generated by tissue and by filtering out the fundamental echo signals that are generated by the transmitted acoustic energy. To achieve this, two processes could be used; one by using filters for fundamental and harmonic imaging and the second using two simultaneous pulses with a 180 degrees difference in phase. The introduction of harmonics allows increased penetration without a loss of detail, by obtaining a clearer image at depth with significantly less compromise to the image quality caused by the use of lower frequencies. This imaging mode could be used in different organs with a heightening of low-contrast lesions through artefact reduction, as well as by the induced greater intrinsic contrast sensitivity of the harmonic imaging mode.

Acoustics↗
PubMed1999

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.

Adult↗
PubMed1999

High frequency (20 MHz) ultrasonic devices: advantages and applications.

OBJECTIVE: This paper investigates the problems, advantages and potential applications of 20 MHz ultrasonic devices. METHOD: Aqueous gel and a thin appropriate membrane to enclose the front tip were used with 20 MHz probes without obvious decrease in resolution and sensitivity compared to the results obtained without a membrane and this considerably facilitates their routine use. RESULTS: Many applications with linear scanning were evaluated in dermatology, ophthalmology (investigations of the anterior chamber of the eye, checking of corneal grafts), stomatology (detection and evaluation of periodontal disease) and in the field of measurement of very low velocities in small vessels by means of a duplex probe comprising two 20 MHz transducers: an imaging transducer and an inclined blood flow measurement transducer. Velocity profiles (velocities less than 0.50 mm/s) were measured in 100-300 microm diameter vessels using a cross-correlation method. CONCLUSION: The use of 20 MHz frequency limits resolution but we have shown that this frequency allows the development of easy to handle probes.

Blood Flow Velocity↗
PubMed1999

Effects of the method of drawing regions of interest on the differential diagnosis of extrapyramidal syndromes using 123I-iodolisuride SPET.

Various parameters are currently used for the semi-quantitative assessment of dopamine D2 receptors and differ according to the delineation of the striatal region of interest (ROI) and the choice of the reference ROI. The aim of this study was to assess the value of different ROI approaches in differentiating patients with normal or increased numbers of D2 dopamine receptors (group 1 = Parkinson's disease, n = 8) from patients with decreased dopamine D2 receptors (group 2 = other extrapyramidal syndromes, n = 9) using 123I-iodolisuride SPET (ILIS-SPET). 123I-iodolisuride (190 +/- 31 MBq) and 99Tcm-ethyl cysteinate dimer (99Tcm-ECD) perfusion SPET were performed in the same position, with a dual-headed gamera camera equipped with fan beam collimators. Both a geometric approach (ellipse, circle or rectangle) and an anatomical approach using the CT scan and perfusion SPET as anatomical guides were used to draw striatal and reference ROIs. A total of 33 different parameters were calculated for each patient, indicating the ratio of counts between the striatal and reference ROIs (frontal, occipital cortex or cerebellum) and the asymmetry between the right and left striatum. More significant differences between group 1 and group 2 were found by using geometric ROIs than by using anatomical ROIs. The most discriminant ratios were the caudate/occipital, caudate/frontal and striatum/occipital ratios (P = 0.001, P = 0.002, P = 0.003 respectively). A close correlation was found between the striatum/caudate and striatum/occipital ratios, but not between the striatum/frontal and striatum/occipital ratios or between the striatum/frontal and striatum/caudate ratios. We conclude that the occipital cortex is the best reference for the semi-quantitative evaluation of dopamine D2 receptors as the frontal cortex could include some dopamine D2 receptor-bound radioligand, and that the caudate/occipital ratio is an appropriate parameter for differentiating Parkinson's disease from non-Parkinson extrapyramidal syndrome by 123I-iodolisuride SPET.

Adult↗
PubMed1999

[Management of cleft lip and/or palate diagnosed in utero].

OBJECTIVE OF THE STUDY: To assess the usefulness of fetal karyotyping in the management of facial cleft lip with or without cleft palate diagnosed during pregnancy and to determine which etiologic and prognosis criteria are helpful to consider for prenatal counselling. MATERIAL AND METHODS: Retrospective study on 35 cases of facial cleft lip and/or palate prenatally diagnosed by ultrasound examination and managed in our fetal medicine unit from 1 January 1989 to 31 December 1996. Complete follow-up was obtained for all fetuses. RESULTS: In our series, the mean gestational age at diagnosis was 25 weeks. In 43% of the cases, additional sonographic anomalies were also recognized. These associated anomalies were more frequent when amniotic fluid quantity was abnormal. Fetal chromosomal determination was conducted in 2/3 of fetuses and numeric or structural abnormalities were found in 20% not related to the cleft size or type (lip and/or palate). All fetuses with isolated facial cleft were chromosomally normal. We report 4 midline clefts, all of them were associated with additional sonographic findings and 3 were part of an holoprosencephaly. CONCLUSION: Prenatal diagnosis of cleft lip and/or palate must draw attention to associated sonographic anomalies especially when amniotic fluid quantity is abnormal. Chromosomal karyotyping is not necessary when facial clefting is isolated except in cases diagnosed early in pregnancy. Midline clefts must draw attention on cerebral midline integrity.

Abnormalities, Multiple↗
PubMed1999

[Comparative study of post-infarction myocardial viability after fibrinolysis by stress tomoscintigraphy and echography: can viability be detected without ischemia?].

The objectives of this prospective study was to define the comparative ability of stress myocardial scintigraphy and dobutamine stress echocardiography to demonstrate post-MI myocardial viability, assessed on the functional recovery in terms of improvement of global and segmental kinetics by cardiac gamma-angiography after revascularization. 18 patients (11 anterior MI, 7 lateral or inferior MI) and 162 segments were analysed semiquantitatively. All patients with persistent significant stenosis underwent secondary revascularization of the artery responsible for myocardial infarction. The prevalence of viability was high, as only 34% of segments initially presented a segmental kinetic abnormality and contraction was improved at 6 months in 54% of cases. Stress scintigraphy and dobutamine echocardiography detected viability with a sensitivity of 96% and 70%, a specificity of 88% and 82%, a positive predictive value of 89% and 77% and a negative predictive value of 95% and 76%, respectively. Only the wall score index with low-dose dobutamine was correlated with the ejection fraction at 6 months. Stress echocardiography is a more reliable predictor of the degree of functional recovery after revascularization. Scintigraphy visualizes much more extensive abnormalities than echocardiography. This often corresponds to ischaemic territories with normal contraction under baseline conditions and low doses of dobutamine. It therefore seems preferable both examinations for optimal assessment of thrombolized patients following myocardial infarction.

Adult↗
PubMed1998

[Transplant renal artery stenosis: long term effect of angioplasty on arterial pressure control and renal function].

We assessed the long-term (M +/- SE: 68 +/- 3 months) arterial pressure and renal function of cadaveric kidney transplant recipients with and without significant (> 70% diameter reduction) transplant renal artery stenosis (TRAS) at angiography. Baseline clinical, immunological and outcome data for 26 patients with TRAS (incidence of TRAS: 6.6%) before and following angioplasty and 72 patients without stenosis at angiography were reviewed and analyzed. The 2 groups were similar with respect to recipient sex ratio and age (45 vs 46), duration of transplantation (7 months), cause of renal failure, donor sex and age, HLA-antigen mismatches and titers of anti-HLA antibodies, CMV infection and anti-CMV antibodies in donors and recipients. The technical success of angioplasty was 92.3%. Restenosis was documented in 6/26 patients (23.1%). Revascularization resulted in a decrease of arterial pressure and number of antihypertensive medications and a lower serum creatinine compared to baseline values. The long-term arterial pressure and serum creatinine levels were similar in patients with and without stenosis. In conclusion, TRAS after revascularization had no detectable influence on the long-term arterial pressure control and renal function within a follow-up period of 68 +/- 3 months.

Angioplasty↗
PubMed1998

[Esophageal morphology with ultrasound imaging after laryngectomy: effect on quality of esophageal speech].

PURPOSE: In patients with aerodigestive cancer, laryngectomy places the esophagus in a superficial position, allowing easy ultrasound examination of this organ. The purpose of the present study was to assess oesophagus morphology after laryngectomy using echotomography and to compare this morphology with voice quality. MATERIAL AND METHODS: In the present study, ultrasonography was performed in 28 patients (delay from surgery: 3 +/- 3 years): 15 were operated using laryngectomy technique (LT) and 13 with pharyngolaryngectomy technique (PLT). On transversal echography, antero-posterior and latero-lateral diameters, esophagus area and dilatation during phonation were systematically measured. These data were compared to the voice quality assessed by two independent observers. RESULTS: A smaller latero-lateral diameter and area were found in the PLT group than in the LT group (p < 0.05) with a flat aspect in group LT. This was associated with faster and better voice acquisition in the PLT group. CONCLUSION: Morphologic study of the esophagus after laryngectomy using ultrasound is in favor of pharyngolaryngectomy technique which allows better conditions for acquiring esophageal voice in better conditions. This could be due to the small area, circle shape and tonicity of the esophagus after this type of surgery.

Esophagus↗
PubMed1998

[Significance of single photon emission computed tomography and akinetic mutism].

Akinetic mutism is a reactive status with permanent opening of the eyes. The accountable lesions are always bilateral. The injured cerebral structures include the frontal gyri, the thalami or the mesencephalic areas. In one case of a 44-year-old patient, magnetic resonance imaging and computed tomography were not contributive. Tc99m brain SPECT imaging was performed and displayed bilateral frontal hypoactivity. This case suggests that this technique could be helpful for diagnosis when clinical features and radiological pattern are opposite.

Adult↗
PubMed1997

[Cerebral HITS: diagnosis, clinical relevance, outlook].

After 6 years of experience, Spencer and colleagues described the detection of embolus signals as height intensity transient signals (HITS) within Doppler flow spectrum from intracranial vessels. These signals (gaseous or materials) are recorded in many situations such as cardiac prosthetic valves, atrial fibrillation, carotid stenosis, carotid surgery or angioplasty. The clinical value is not well known: neurological impairment associated with brain lesions is described in case of cardiac prosthetic valves. The observation of HITS in carotid stenosis is associated with an increased risk of stroke. The detection of HITS offers a new orientation in studying stroke but some technical and/or clinical difficulties have to be solved.

Carotid Stenosis↗
PubMed1997

[Circulation and cerebral metabolism in neonatal hypoxia-ischemia].

The basic physiological variable in hypoxic-ischaemic brain injury is cerebral oxygen delivery. When oxygen delivery becomes insufficient to meet the cellular demands for oxygen, a sequence of biochemical events will be triggered leading to cell death. High levels of CBF following severe birth asphyxia is now well documented by Doppler ultrasound which has been shown to be a useful prognostic indicator following birth asphyxia. Near infrared spectroscopy (NIRS) is of great potential value since it may be used at the bed-sid and allows to measure the cerebral blood volume and the concentrations of cytochrome aa3. Magnetic resonance spectroscopy (MRS) allows noninvasive assessment of cerebral metabolism in asphyxiated neonates. 31P MRS has demonstrated that birth asphyxia leads to delayed impairment of cerebral energy metabolism and is predictive of later neurodevelopmental outcome. 1H MRS has shown lactate accumulation and a later decline in N-acetyl aspartate concentration.

Asphyxia Neonatorum↗