Search PubMed⌕ Search

Biomedical subjects

J Chambron

Publications and source records attributed to J Chambron.

At least 55 records · Page 3Linked to original sources
PubMed1989

Myocardial gated tomoscintigraphy with 99Tcm-methoxy-isobutyl-isonitrile (MIBI): regional and temporal activity curve analysis.

Myocardial gated tomoscintigraphy with hexakis-(2 methoxy-isobutyl-isonitrile) labelled with 99Tcm, is more suitable to resolve precisely the size of myocardial infarct than nongated 201Tl tomoscintigraphy. Gated tomography gives short axis slices at eight points in the cardiac cycle. A quantitative method to analyse heart wall activity and its motion is proposed. In two groups of patients, one with inferior infarct and the other with anterior infarct, the time-activity curves show a maximum in systole for healthy regions and a flattened curve in akinetic regions. Gated tomoscintigraphy assesses more accurately the size of the injured regions because there is no averaging between systolic and diastolic activity as in 201Tl tomoscintigraphy. This method should permit a better follow-up of patients with myocardial infarct.

Humans↗
PubMed1989

[Value of cine magnetic resonance imaging in the diagnosis and quantification of valvular regurgitation. Comparison with angiography and Doppler echocardiography].

Thirty-three patients presenting with regurgitation of the mitral valve (19 cases), tricuspid valve (14 cases) or aortic valve (11 cases) documented by angiography (n = 20) and/or doppler-echocardiography (n = 28) were examined by cine-MRI in order to test this method in valvular regurgitation. Sixteen ECG-synchronized cine-MRI images were acquired by the GRASS technique every 40 ms on appropriate projections, with a resistive 0.28 Tesla Bruker magnet. The semiology of normal and pathological blood flow images at cine-MRI is described. Valvular regurgitations present as "signal void" jets the chronology and spatial extension of which depend on the severity of the lesion. The differential diagnosis with physiological flows is discussed. The diagnostic sensitivity of the method was 29/29 when compared with angiography and 29/33 when compared with doppler-echocardiography (2 cases of 1/4 mitral regurgitation and 2 cases 1/4 tricuspid regurgitation were not visible at cine-MRI). The specificity of this method, as can be judged from 104 patients explored, also seems to be satisfactory. The severity of regurgitation was graded from 1 to 4 with the three methods, on the basis of strict criteria. The differences in grade evaluation exceeded +/- 1 point in only one case of mitral regurgitation which was greatly underestimated by the doppler method as compared with angiography and cine-MRI. Thus, cine-MRI is a reliable method to evaluate valvular regurgitations and their severity. It solves the practical problem raised by non-echogenic patients when catheterization is to be postponed or avoided.

Adult↗
PubMed1989

[Familial hyperthyroxinemia with dysalbuminemia: screening of 21,000 patients at the occasion of thyroid evaluation].

Serum samples from 21,342 patients undergoing evaluation of thyroid status were screened for familial dysalbuminemic hyperthyroxinemia (FDH) using a specific test based on the measure of charcoal uptake of 125I thyroxine (T4) from serum diluted 1:100 with addition of unlabelled 10(-6) M T4. We found 17 cases of FDH: a higher incidence (8:10,000) than previously reported in the general population (1:10,000). The results of thyroid function tests of patients with FDH are presented: total T4 concentration is increased in only 14 subjects; thyrotropin and free T4 measured by an immunoextraction method are the most useful assays to evaluate the clinical status of these patients.

Humans↗
PubMed1989

[Comparison of the left ventricular stroke volume and fraction measured with MRI and contrast ventriculography].

27 patients who underwent a contrast ventriculography in right anterior oblique at 30 degrees (for various cardiopathies) were studied by MRI with a mean delay of 5.7 +/- 6.2 days. After location of the medio-ventricular area, a diastolic horizontal section (apex of the R wave) and a systolic section (descending portion of the T wave) are carried out using the spin ultrasound technique. The same calculations are used for MRI au X-Ray contours (modified area-length method) by two strictly independent operators. With MRI, the LVSF is under estimated (40.4 +/- 19%) as compared angiography (46.1 +/- 18%). The linear correlation is 0.79 and in half of the patients (13 in 27) the deviation of the LVSF exceeds 10 p. cent. The volumes also tend to be underestimated with MRI (97 +/- 50 and 64 +/- 51 ml for the diastole and systole respectively) compared with angiography (123 +/- 66 and 73 +/- 62 ml), but the difference is only significant for the diastole and the linear correlation coefficients are improved at 0.82 and 0.90. Underestimation of the parameters measured with MRI is the consequence of multiple factors including the imprecise determination of the true telesystole, the marked effect of the partial volume related to the thickness of the section, and especially the obliquity of the plane studied on MRI, compared with the long axis of the heart. The error made by using a calculation algorithm, conceived for projective methods showing the long axis of the modeled ellipsoid, also explains the underestimation of volumes obtained with MRI, tomographic method. The simple technique used here seems especially interesting in the analysis of segmental contraction. Finally, the development of cine-MRI will undoubtedly be extremely beneficial in the study of ventricular contraction and relaxation.

Adult↗
PubMed1989

[MRI study of parathyroid adenoma. Value of T2-weighted sequences].

The authors report a series of 22 patients operated for primary hyperparathyroidism. The parathyroid adenoma was located preoperatively by MRI and ultrasonography. Measurement of the relaxation time was performed in vitro at 37 degrees C in a 0.47 Tesla field during the 30 minutes following resection. The relaxation times obtained at a precession frequency of 20 mHz were 0.844 +/- 0.16 sec for T1 and 0.082 +/- 0.025 sec for T2. MRI had a sensitivity of 73% and a specificity of 88% for the localization of the parathyroid adenoma, while ultrasonography had a sensitivity of 73% and a specificity of 98%.

Adenoma↗
PubMed1988

[Magnetic resonance imaging in the diagnosis of myxedematous pericardial effusions].

Two cases of myxedematous pericardial effusions studied by magnetic resonance imaging (MRI) are reported. After a reminder of the place of pericardial involvement in this disease, the advantage of MRI which provides original semiologic factors on the analysis of topographic extension and on the approach of the cellular characteristics of the effusion, is presented. Concerning the latter, difficulties of interpretation and current imprecisions are discussed but we will especially remember the advantage of this recent technique in the diagnosis of an effusion, even moderate, in hypothyroidism, mainly in patients with poor sonographic response.

Adult↗
PubMed1988

[Magnetic resonance imaging and herpetic encephalitis].

Cerebral lesions in two cases of herpetic encephalitis were detected by MRI using a spin-echo sequence and delayed echo signal recordings, whereas CT scans were normal. In one case pathology showed lesions to be more extensive than MRI anomalies. This suggests that even in the absence of EEG and CT anomalies, an encephalitis can be suggested by MRI.

Electroencephalography↗
PubMed1987

Multiple sclerosis diagnosis: magnetic resonance imaging compared with other paraclinical examinations.

Examination by magnetic resonance imaging (MRI), evoked potentials (EP) and cerebrospinal fluid (CSF) analyses was carried out on 97 definite, 20 probable and 40 possible multiple sclerosis (MS) patients (McAlpine's clinical criteria). MRI of only 4 transverse brain sections at the level of the ventricles and the analysis of the first 4 echoes showed periventricular or parenchymal lesions, or both, in 114 of the 117 definite and probable MS patients and in 25 of the possible MS patients. MRI was more sensitive than the CSF analyses or EP. The MRI abnormalities were not, however, MS-specific.

Adolescent↗
PubMed1987

[Value of nuclear magnetic resonance in dilated cardiomyopathy. Approach to intraventricular hemodynamics].

The value of magnetic resonance imaging (MRI) with multiechoes spin-echo sequences was investigated in 22 patients with dilated cardiomyopathy (group I) and 25 normal subjects serving as controls (group II). The results of MRI in group I were compared with those of echocardiography and radionuclide ventriculography. Measurements of left ventricular dimensions at echography and MRI showed a tendency, with MRI, to overestimate wall thickness and underestimate ventricular diameter. Thus, for diastolic LV we had 63.8 +/- 10.5 mm with MRI vs 70.6 +/- 7.6 mm with echography, the corresponding figures for posterior wall thickness being 112 +/- 1.4 mm vs 9.9 +/- 1.1 mm respectively. These differences seem to be due to MRI introducing a partial volume effect dependent on the thickness of slices and of their orientation in relation to the cardiac axis. MRI evaluation of left ventricular function by calculation of myocardial fibre shortening fractions correlated poorly with the echocardiographic value of the same parameter and with the radionuclide ejection fraction (r = 0.58 and 0.575 respectively; p less than 0.05). For better quantification of the cardiac pump function, planimetry of the endocardial contour during diastole and systole is required. It would seem that the value of MRI resides in the possibility it offers to explore left intraventricular haemodynamics by studying the "flow signal" obtainable from multiechoes sequences at different moments of the cardiac cycle. During systole, we found a left intraventricular signal that was reinforced on even echoes and much more intense in cardiomyopathy patients (scores = 1.61 +/- 1.06) than in controls (score = 0.77 +/- 0.7; p less than 0.01). The intensity score for this signal correlated with the ejection fraction in group I subjects (r = 0.82).

Adult↗
PubMed1987

Multiple sclerosis diagnosis: magnetic resonance imaging compared with other instrumental examinations.

Examination by magnetic resonance imaging (MRI), evoked potentials (EP) and cerebrospinal fluid (CSF) analyses was carried out on 97 definite, 20 probable and 40 possible multiple sclerosis (MS) patients (McAlpine's clinical criteria). MRI of only 4 transverse brain sections at the level of the ventricles and the analysis of the first 4 echoes showed periventricular or parenchymal lesions, or both, in 114 of the 117 definite and probable MS, and in 25 of the possible MS. MRI was more sensitive than the CSF analyses or EP; abnormalities more frequently appeared in known MS, and clinically asymptomatic lesions were seen. The MRI abnormalities were not, however, MS-specific; they were present in other neurological patients; none posed a question of differential diagnosis from MS. Complementary examinations, and especially MRI, should be a valuable adjunct for MS diagnosis, as long as the findings are viewed in the clinical context.

Adolescent↗
PubMed1986

Chemical and molecular exchange effects on T2 relaxation of living tissues: a pulse spacing dependence study.

Contrast in magnetic resonance imaging depends principally on the longitudinal relaxation (R1) and the transverse relaxation rate (R2) of the observed nuclei, most often the protons. The spin-spin relaxation rate (R2) is the result of several mechanisms. The dependence of the interpulse delay of the Carr-Purcell-Meiboom-Gill sequence on the transverse relaxation rate of the water was studied in rat organs in vitro. It gives an insight into the exchange mechanisms involved. The increase of the interpulse delay from 0.2 ms to 5 ms gives an R2 increase of 23, 15, 3, and 2 s-1 for the heart, the liver, the spleen and the brain, respectively. These increases are compared to the R2 increases obtained in 17O-enriched water, amino acid and albumin solutions atomic exchange takes place. The concentration of these materials in organs cannot explain the R2 increase of the organs with the interpulse delay. Water exchange between intra and extracellular compartments is proposed to explain the R2 increase with interpulse delays in organs like the heart and the liver.

Albumins↗
PubMed1986

[Spatial ventricular gradient studied by computerized vectorcardiography. Normal and pathological values. Interpretation and clinical evaluation].

The ventricular gradient is a reflection of uneven ventricular repolarisation. Until recently is was only appreciated in the frontal plane of the classical electrocardiogramme and expressed as the sum of the vectors representing the surfaces under the QRS complex and T wave. We used computerised vectorcardiography to obtain a more exact evaluation of the size and spatial orientation of the vector gradient. The spatial vector gradient was calculated in a control group and in a number of pathological conditions. The reference values were established in 70 normal subjects with a mean age of 36 +/- 21 years: 0.092 +/- 0.016 m V.s for amplitude: 38.4 degrees +/- 6.1 for thesite and 21.6 degrees +/- 8.7 for the azimuth. The size and spatial orientation of the ventricular gradient can be used to define normal limits and to distinguish subgroups by using the values of the site and azimuth. The spatial ventricular gradient is a new approach to defining the limits of normality in poorly understood abnormalities of ventricular repolarisation. It may also be useful in the comprehension of certain forms of cardiac arrhythmia related to desynchronisation of ventricular repolarisation.

Adolescent↗
PubMed1986

[Nuclear magnetic resonance in the diagnosis of aortic diseases].

The diagnostic value of nuclear magnetic resonance imaging was assessed in a number of aortic pathologies: aneurysms of the thoracic and abdominal aorta, sinus of Valsalva aneurysms and dissection of the aorta. The imager was equipped with a resistor magnet providing a field of 0.15 Tesla. An electrocardiographic gating system was perfected. The images obtained were very satisfactory as they provided three dimensional morphological information and a qualitative assessment of blood flow. Further studies are now required with comparison with other invasive and non-invasive diagnostic methods to determine the clinical role of NMR imaging and to evaluate the diagnostic sensitivity and specificity of this new technique.

Aortic Dissection↗
PubMed1986

[Importance of magnetic resonance imaging in myocardial infarct].

Imagery by magnetic resonance (IMR) represents a new modality of medical imagery based on the interaction between the magnetic fields produced by radio-frequency waves and living substance. IMR finds an interesting application in the study of different stages of myocardial infarction. In 30 cases of myocardial infarction IMR was compared with thallium tomoscintigraphy and echocardiography. In the acute stage, myomalacia appears in IMR as a superbrilliant zone, and in the chronic stage parietal thinning and dyskinesias are apparent. Intraventricular thromboses, but also hemostasis in aneurysmatic or akinetic sites are visualised as a high-intensity signal within these areas. IMR represents therefore a new means of evaluation of size and evolution of the necrosis. This procedure provides also functional informations about the contraction and flow anomalies.

Adult↗
PubMed1986

[The ultrasensitive determination of TSH permits the prediction of the response to TSH in the TRH test].

A new ultrasensitive TSH immunoradiometric assay (IRMA) using two monoclonal antibodies is now able to distinguish between euthyroid and hyperthyroid patients. The aim of this study was to compare data given by ultrasensitive basal TSH (IRMA) and by the response of TSH to TRH test considered until now as the more reliable test in case of mild or atypical hyperthyroidism. Basal plasma TSH levels were determined in euthyroid (n = 80), hyperthyroid (n = 30), hypothyroid (n = 14) and pituitary deficient patients (n = 8) before and 30 minutes after a TRH test (250 micrograms i.v.). A close linear correlation was found between basal and post-stimulative TSH levels. Normal TSH response ranged from 2 to 22 uU/ml. The sensibility and the specificity of these two parameters appeared comparable in the case of primary dysthyroidism; on the contrary basal TSH levels were not sufficient for the diagnosis of central hypothyroidism. In conclusion, excepted for pituitary deficiency, basal plasma TSH (IRMA) levels are accurate and sufficient in the evaluation of the thyroid function and make the TRH-test useless.

Humans↗