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Biomedical subjects

M Osteaux

Publications and source records attributed to M Osteaux.

At least 109 records · Page 6Linked to original sources
PubMed1992

Dual-energy X-ray absorptiometry of lumbar vertebrae: relative contribution of body and posterior elements and accuracy in relation with neutron activation analysis.

The bone mineral content of 34 lumbar vertebrae obtained from ten cadavers (three men, seven women; age 61-88 years) was measured using a pulsed source dual-energy X-ray absorptiometry (DEXA) apparatus. Scanning was performed in the frontal projection and was repeated on the vertebral bodies obtained after removal of the posterior elements of the vertebrae. Subsequently a nondestructive neutron activation analysis (NAA) was performed. The mineral content of the vertebral bodies was found to represent (mean, SEM) 53.0% (1.9%) of the content of the whole vertebrae. The mineral content of the vertebral bodies assessed with NAA (BMC NAA) and with DEXA (BMC DEXA) showed a high correlation: BMC NAAA = (1.016 x BMC DEXA) + 0.990 r = 0.949 (p less than 0.001). We conclude that the mineral content of lumbar vertebral bodies can be accurately measured in vitro in a water environment by DEXA, and that the mean contribution of the posterior elements of the vertebra to the calcium hydroxyapatite content of whole vertebrae measured in the frontal projection is as high as 47.0%.

Absorptiometry, Photon↗
PubMed1992

Excitation characteristics of adiabatic half-passage RF pulses used in surface coil MR spectroscopy. Application to 13C detection of glycogen in the rat liver.

Properties of sech/tanh and sin/cos half-passage RF pulses are discussed in view of their use in surface coil MR spectroscopy. We focus on the use of these pulses in a regime which is partially adiabatic, i.e. not strictly adiabatic off-resonance, while on-resonance the adiabaticity condition is fulfilled. It is shown that the frequencies of the singular points of the excitation profiles, as well as their number, depend on the B1 field. This leads to a signal intensity reduction from off-resonance spectral regions over much broader ranges than generally believed. We show in particular that with surface coil, sin/cos RF pulses may perform particularly well, providing optimal excitation on resonance and a desired attenuation over a broad spectral range off-resonance. This feature is applied for the in vivo detection of rat liver glycogen by means of 13C MR spectroscopy. Under suitable RF power conditions, a remarkable attenuation of the signals from the saturated carbons of the subcutaneous fat can be achieved.

Animals↗
PubMed1992

[MRI of the wrist joint].

Due to the development of new surface coils and the use of thin slices, MRI has become an essential diagnostic tool in wrist pathology. After several technical considerations, the authors describe the normal MRI appearance of the various anatomical structures of the wrist, particularly the triangular fibrocartilaginous complex of the wrist and the elements of the carpal tunnel. They review the principal indications for MRI: chronic diseases such as carpal tunnel syndrome and traumatic ligamentous and cartilaginous lesions. The bone marrow lesions detected in the presence of occult fractures and osteonecrosis of the lunate or scaphoid are then briefly considered. The diagnostic criteria of median nerve compression (carpal tunnel syndrome) include morphological and signal changes in the nerve, abnormal palmar convexity of the flexor retinaculum and signs of tenosynovitis of the intracarpal flexor tendons. However, in practice, MRI is only useful when there is disagreement between the clinical and EMG findings and in postoperative recurrences, in which case it may reveal insufficient section of the retinaculum or the presence of exuberant postoperative fibrosis responsible for persistent nerve compression. Traumatic tears of the triangular fibrocartilage are characterised by a linear high signal intensity image (on T1 and T2 weighted sequences), usually situated in the periphery of the articular disk. Degenerative lesions tend to be central, within the disk and are frequently observed after the age of 40 years.

Carpal Bones↗
PubMed1992

Imaging and differential diagnosis of synovial sarcoma.

Synovial sarcoma is an uncommon malignant tumor, most frequent in the lower extremity, predominantly in young males. The authors review the clinical history, the different radiographic manifestations and MR appearance of the entity. The MR findings cannot be considered specific for synovial sarcoma. A heterogeneous septated mass located close to a joint, a tendon or a bursa is most indicative of the tumor. The radiographic features of a soft tissue mass with associated calcifications and bony erosions in the lower extremity should suggest a synovial sarcoma. The most likely differential diagnoses are discussed.

Adult↗
PubMed1992

Detecting clustered microcalcifications in the female breast: secondary digitized images versus mammograms.

We compared the detection of clustered microcalcifications by means of conventional mammograms and by means of secondary digitized images with a spatial resolution of 2048 x 1684 pixels and a contrast resolution of 12 bit. A Receiver Operating Characteristic (ROC) study was carried out using a cadaver breast showing phantom microcalcifications. A set of 100 mammograms was evaluated by two experienced senior radiologists. The ROC scores obtained with the digital images were 10% lower than those obtained with the conventional images. This difference however does not reach statistical significance. The use of a digital zoom function based on pixel duplication is also investigated. This zoom function does not produce a change in the diagnostic accuracy of the digital method. Attention is also paid to the advantages and disadvantages encountered by the radiologists when working on the digital viewing system. The most important drawback seems to be that it is considerably more time consuming than the conventional procedure, and this is especially due to the long loading time of the images and to the absence of window and level preselections.

Breast Diseases↗
PubMed1992

Magnetic resonance imaging (MRI) of the ankle and hindfoot.

While Magnetic Resonance Imaging (MRI) has become a routine diagnostic method to deal with pathology of the knee, little has been published about foot and ankle lesions. This is probably due to the anatomic complexity of bone and ligamentous structures of these small joints, necessitating the use of very thin slices from various orientation planes (orthogonal and oblique planes). A special technique is needed allowing a 3-dimensional (3D) analysis, using inframillimetric slices and more sophisticated equipment than for 2-dimensional (2D) MRI (high fields with good homogeneity, specialized image processors...). An initial potential indication of the method is the precise diagnosis of lateral ligamentous components in severe sprains. MRI may determine if surgical therapy is needed. The ligamentous components are reconstructed along their specific planes thanks to the 3D method. Furthermore, assessment of the ligamentous damage is also possible in chronic ankle instability (elongation, fibrotic appearance...). Thanks to the multiplanar approach, associated lesions of articular cartilage can be revealed in ankle sprains. The high sensitivity of MRI in slight modifications of medullary bone allows the early diagnosis of "occult" fractures (not seen on conventional radiographs), osteonecrosis, osteochondrosis and reflex sympathetic dystrophy syndrome. Finally, MRI easily displays all ankle and foot tendons and fascia and is particularly helpful in depicting partial tears and postoperative complications.

Adult↗
PubMed1992

[Superselective cerebral embolization of an arteriovenous malformation in the temporal lobe following partial neurosurgical resection].

We report a case of cerebral embolization of an arteriovenous malformation in the temporal lobe after partial neurosurgical resection. The lesion consisted of two compartments of which only the lateral part with combined large hematoma was resected. The medial compartment was treated by superselective embolization using a microcatheter and polyvinyl alcohol particles. Because of his psychiatric condition, general anaesthesia was used in this young male.

Adult↗
PubMed1992

CT and MR findings in ruptured dermoid cyst in the right parasellar cistern: report of a case.

A case of ruptured dermoid cyst in the right parasellar cistern imaged by MRI and CT is reported. The disseminated lipid droplets were found scattered throughout the subarachnoid spaces including the prepontine cisterns, in front of the right petrous apex as well as bilaterally in the frontal horns. The density of the lipid droplets was comprised between -80 and -100 HU. The lesions were hyperintense on T1-weighted images and hypointense on T2-weighted images.

Adult↗
PubMed1991

Absolute quantification of 31P muscle metabolites using NMRS with an internal standard and a high-Q, double-tuned coil.

31P-nuclear magnetic resonance spectroscopy (NMRS) is used to determine absolute concentrations of 31P metabolites in rat muscle. A technique exploiting tissue water 1H as internal concentration reference and a highly sensitive, double-tuned coil is described and evaluated experimentally. On KH2PO4 solutions of known concentration and varying coil loading it is shown to allow neutralization of systematic errors due to conductive losses, which normally range up to 20% or more. In vivo application in the determination of the absolute concentrations of ATP, PCr and Pi in eight rat thighs yields results that are in good agreement with literature values.

Adenosine Triphosphate↗
PubMed1991

Low vertebral bone density values in young non-elite female runners.

Thirty-five female runners (26.6 +/- 0.9 years, range 17-35) were scheduled for bone mineral density evaluation, using quantitative computed tomography of the lumbar spine. In 17 women with oligo-amenorrhea, vertebral bone mineral density was under the normal range (defined from a control group of 46 sedentary healthy females in the same age range), while it was within the normal range in all runners with regular menses (n = 18). When age classes were considered, all runners aged 17-21 (11/11) were found to have oligo-amenorrhea and low bone mineral density values, the difference in mineral density with the controls of the same age quartile being highly significant (p less than 0.001). Runners from the two youngest age classes (17-21 and 22-26) had started training early after menarche (0.9 +/- 0.6 and 2.5 +/- 1.6 years, respectively). These results show that very young female runners with oligo-amenorrhea may have impressively low bone mineral density values. The possibility that early onset of training, close to menarcheal age, might be a risk factor for low mineral density, deserves further investigation.

Adolescent↗
PubMed1991

Ossifying fibroma of the long bones. Radiological diagnosis, differential diagnosis and management implications.

We report a case of ossifying fibroma of the long bones (OFLB). This lesion, occurring mainly during the first decade of life, typically affects the tibial diaphysis and clinically presents as a painless bony enlargement. Radiographic features include an osteolytic cortical expansion, containing diffuse calcifications, and separated from the medullary by a thick cortical rim. CT appears to be the examination of choice to define these signs and permits differentiation from monostotic fibrous dysplasia and from adamantinoma (by demonstrating the presence or absence of diffuse high attenuation values). The importance of making the differential diagnosis is stressed, as prognosis and management of OFLB, fibrous dysplasia and adamantinoma may vary considerably.

Bone Neoplasms↗
PubMed1990

Pituitary microadenomas: diagnosis with two-and three-dimensional MR imaging at 1.5 T before and after injection of gadolinium.

The usefulness of different magnetic resonance (MR) imaging sequences (coronal and sagittal spin-echo [SE] and three-dimensional fast low-angle shot [3D FLASH]) in the detection of pituitary microadenomas before and after gadolinium injection was prospectively evaluated in 28 patients with surgical confirmation. When evaluated separately, the most useful sequences in the detection of these microadenomas were coronal pregadolinium T1-weighted SE, coronal pregadolinium 3D FLASH, coronal postgadolinium T1-weighted SE, and coronal postgadolinium 3D FLASH. The combination of pre- and postgadolinium T1-weighted sequences with pre-and postgadolinium 3D FLASH sequences produced the highest number of true-positive findings (90%) and the lowest number of false-positive findings (5%). When a 1.5-T imaging unit with a high signal-to-noise ratio allowing useful three-dimensional acquisition is used, the authors advocate a coronal T1-weighted SE sequence, followed (if necessary) by a coronal 3D FLASH sequence, both without injection of gadolinium, in the diagnosis of pituitary microadenomas. When no confident diagnosis is reached, the same sequences should be performed after the injection of gadolinium. The sagittal pre- and postgadolinium T1-weighted SE and long-TR SE sequences are useful only in specific cases.

Adenoma↗
PubMed1990

31P-NMR spectroscopy and the metabolic properties of different muscle fibers.

To study the in vivo recruitment of different fiber types and their metabolic properties, 31P-nuclear magnetic resonance spectroscopy (31P-NMRS) of the human calf muscle was performed in seven normal sedentary subjects. In the exhaustive exercise protocol used, the work load was increased every minute during 5 min. This resulted in a prominent split of the Pi resonance in all subjects, indicating pH compartmentation in the muscles studied. From the chemical shift of the Pi peaks relative to phosphocreatine (PCr) at the end of the exercise, intracellular pH (pHi) averaged 6.92 +/- 0.05 (SD) in compartment 1 and 6.23 +/- 0.15 in compartment 2. The recovery of both Pi resonances after exercise could be followed easily in five of these subjects. The recovery rate of the Pi peak is a good estimate of the oxidative metabolism at the end of the exercise. A monoexponential regression analysis showed that the mean initial recovery rate S0 was 2.49 +/- 0.17%/s in compartment 1 and only 0.87 +/- 0.12%/s in compartment 2, indicating aerobic function three times higher in compartment 1 at the end of exercise. The mean relative ATP fraction dropped significantly (P less than 0.001), from 20.0 +/- 1.0% of the total 31P signal integral before exercise to 14.0 +/- 1.6% at the end of exercise. The simultaneous visualization of two compartments, in good order, one with high pHi and fast recovery and another with low pHi and slow recovery, is rationalized by the different metabolic behavior of type I and II fibers in human calf muscle in response to exhaustive exercise. This study demonstrates that 31P-NMRS is an excellent noninvasive procedure to quantify aerobic metabolism in both fiber types simultaneously.

Adenosine Triphosphate↗
PubMed1990

Tissue characterization of atheromatous plaques: correlation between ultrasound image and histological findings.

Fifty-four atheromatous plaques of carotid arteries, obtained at autopsy, were scanned with a high-resolution real-time instrument, then histologically examined. Comparison between atherogenesis assessed first by histology then by ultrasonography allowed us to differentiate young from old plaques. An old plaque is characterized by a dense heterogeneous echo pattern and irregular borders or ulceration. Previous studies have shown a correlation between the presence of hemorrhage and ulceration of atheromatous plaques in the carotid, and the frequency of cerebral complications. Since these characteristics were mainly found in older plaques, we consider them to be the most important ones clinically.

Arteriosclerosis↗
PubMed1990

[Left adrenal gland hemorrhage as isolated lesions following blunt trauma].

Posttraumatic hemorrhage of the adrenals usually occurs in the right or in both glands. This report describes one case of isolated, posttraumatic hemorrhage of the left adrenal in a 56-year-old woman. US examination shows a mass, almost isoreflective with the spleen, with central bright echoes, which are characteristic of fresh hematoma. CT examination displays a dense, relatively well-defined mass lesion causing a spread of the adrenal limbs. Density measurements are typical for hematoma. Follow-up examination one week later demonstrates partial regression of the lesion in volume and density.

Abdominal Injuries↗
PubMed1990

[Magnetic resonance imaging in knee injuries].

Of all the diagnostic imaging techniques for the injured knee, Magnetic Resonance Imaging (MRI) has been shown the most worthwhile. Indications for standard X rays, arthrography and ultrasonography are briefly reviewed. Advantages of MRI, the technical aspects and the sequences used are explained. After a short description of the signals of all the common anatomic components of the knee, we describe MR findings in meniscal pathology, tenoligamentous lesions and cartilage and bone injuries.

Humans↗
PubMed1989

Bone loss in young hypoestrogenic women due to primary ovarian failure: spinal quantitative computed tomography.

Vertebral bone mineral density was investigated in 22 young (29.3 +/- 1 years) women with primary ovarian failure, attending for infertility. The lumbar spine was studied, using a preprocessing dual-energy quantitative computed tomography technique and assessing vertebral bone mineral density from the reconstructed 125-kV image. Previously untreated women had significantly (P less than 0.001) lower values than a group of age-matched healthy controls, while the difference between those women having received estrogen therapy and the same controls was not significant. Sixteen patients were restudied after 6 to 21 months of estrogen therapy, part of a regimen intended to prepare the endometrium for oocyte donation, and vertebral bone mineral density increased in 12 of them. The authors conclude that primary ovarian failure is a cause for bone loss in these young women and that estrogen therapy is effective.

Adult↗