Search PubMed⌕ Search

Biomedical subjects

C Scheiber

Publications and source records attributed to C Scheiber.

13 recordsLinked to original sources
PubMed2000

Automatic object identification: an fMRI study.

Boucart and Humphreys reported an automatic access to object identity when observers attend to a physical property of the form of an object (e.g. the orientation) but not to its colour. We sought evidence for automatic identification in a brain imaging study using fMRI. In an orientation decision task participants decided whether a picture was vertical or horizontal. In the colour decision task participants decided if a picture was blue or green. Activation of areas 18-19 was found for both color and orientation. Activation of the temporal area 37 occurred more frequently in the orientation than in the colour decision task. This result suggests that automatic identification activates the same brain area as overt processing of semantic information.

Adult↗
PubMed2000

Nuclear medicine image registration by spatially noncoherent interferometry.

UNLABELLED: This article introduces a technique for obtaining high-resolution body contour data in the same coordinate frame as that of a rotating gamma camera, using a miniature range finder, the conoscope, mounted on the camera gantry. One potential application of the technique is accurate coregistration in longitudinal brain SPECT studies, using the face of the patient (or "mask"), instead of SPECT slices, to coregister subsequent acquisitions involving the brain. METHODS: Conoscopic holography is an interferometry technique that relies on spatially incoherent light interference in birefringent crystals. In this study, the conoscope was used to measure the absolute distance (Z) between a light source reflected from the skin and its observation plane. This light was emitted by a 0.2-mW laser diode. A scanning system was used to image the face during SPECT acquisition. The system consisted of a motor-driven mirror (Y axis) and the gamma-camera gantry (1 profile was obtained for each rotation step, X axis). The system was calibrated to place the conoscopic measurements and SPECT slices in the same coordinate frame. RESULTS: Through a simple and robust calibration of the system, the SE for measurements performed on geometric shapes was less than 2 mm, i.e., less than the actual pixel size of the SPECT data. Biometric measurements of an anthropomorphic brain phantom were within 3%-5% of actual values. The mask data were used to register images of a brain phantom and of a volunteer's brain, respectively. The rigid transformation that allowed the merging of masks by visual inspection was applied to the 2 sets of SPECT slices to perform the fusion of the data. CONCLUSION: At the cost of an additional low-cost setup integrated into the gamma-camera gantry, real-time data about the surface of the head were obtained. As in all other surface-based techniques (as opposed to volume-based techniques), this method allows the match of data independently from the dataset of interest and facilitates further registration of data from any other source. The main advantage of this technique compared with other optically based methods is the robustness of the calibration procedure and the compactness of the sensor as a result of the colinearity of the projected beam and the reflected (diffused) beams of the conoscope. Taking into account the experimental nature of this preliminary work, significant improvements in the accuracy and speed of measurements (up to 1000 points/s) are expected.

Brain↗
PubMed1999

The pitfalls of planar three-phase bone scintigraphy in nontraumatic hip avascular osteonecrosis.

PURPOSE: This study documented the previously reported lower sensitivity of routine planar three-phase bone scintigraphy (BS) performed using a high-resolution parallel-hole collimator compared with MRI to diagnose nontraumatic avascular necrosis of the hip (AVN). METHODS: Six observers reviewed 143 bone scintigrams obtained in patients with nontraumatic hip pain (n = 120) or a control group (n = 23). All patients had a standard radiograph and MRI within 2 months of the BS. Of 280 hips, 148 (53%) were painful on the day of the examination. The osteonecrosis group (AVN) consisted of 93 instances of AVN in 58 patients. Although it departs from the clinical situation, this method evaluated the intrinsic performance of the imaging method. The data were analyzed using a receiver operating characteristic method. RESULTS: For the six observers, the A(z) values were 0.65, 0.67, 0.66, 0.67, 0.73, and 0.79, respectively, and 0.66, 0.71, 0.75, 0.81, 0.81, 0.82, and 0.84 after removing hip diseases other than AVN through data manipulation. Bone marrow edema, as seen on MRI, was the most frequently reported misleading sign in false-positive diagnoses, especially in the early or late phases of the disease. False-negative diagnoses misclassified the scans as "asymptomatic hips" in 28 of 30 cases. Twenty-two of 30 scans appeared normal, but these AVN lesions were small (<25%) and were discovered by chance on MRIs that displayed bilateral involvement associated with radiographic evidence (stage 0 or 1). Thirteen of 20 patients were followed for 3 or more years, and only one worsened. CONCLUSIONS: BS is not indicated to diagnose possible contralateral AVN if the hip is asymptomatic. This study emphasizes the results from the literature; if indicated, a radionuclide hip investigation requires the use of a pin-hole collimator, a SPECT study with scatter correction and iterative reconstruction algorithms, or both.

Adult↗
PubMed1998

Video loop MRI of ocular motility: a new technique: turbo rare sequence at 2 T for the study of horizontal gaze.

PURPOSE: To improve existing MRI (Magnetic Resonance Imaging) methods of assessing ocular motility in horizontal gaze by using a multi-static fast imaging T2W MRI sequence, preventing patient head motion and convergence of the eyes during the study for the diagnosis and management of complex paralytic strabismus. SUBJECTS AND METHODS: A turbo-RARE image of the orbits was acquired in a set plane each time the patient fixed on a virtual image of one of 15 LEDs (Light Emitting Diodes). Positioning and securing the head was by a security cushion with an 8 degree tilt of the 25 cm quadrature head coil. After completion of the study (5 minutes) the MRI images were transferred to a work station and on to a magnetic-video tape to be replayed in cine mode on a PC using standard software. The qualitative analysis was completed by the study of quantitative parameters: visual axis, minor axis of the lens, the lines and angles of the horizontal rectus muscles with the optic nerve and the visual axis. We used digital image analysis to measure the cross-sectional areas of these muscles and also to determine muscle volumes. Twenty normal volunteers and 3 cases of oculomotor palsies were so studied. RESULTS: The experimental setup allowed us to obtain: 1) rapid (14 s) and high resolution images (256 x 196 x 3 mm); 2) which were free artifacts; 3) with no detectable eye convergence; 4) in which the lateral and medial rectus muscles and anatomical details of the orbit were clearly depicted; 5) from which additional functional information was obtained from the cine loop analysis; 6) wherein the visual axes did not converge during horizontal versions; 7) which permitted horizontal rectus muscle angles to be followed during contraction and relaxation; and 8) allowed the cross-sectional area of the four rectus muscles to be compared during contraction and relaxation (difference of 0.2 cm2). CONCLUSIONS: This method will provide useful functional quantitative information in the evaluation of ocular motility disorders. The procedure is readily clinically applicable

Convergence, Ocular↗
PubMed1991

[Localized cancer of the prostate. Correlation between MRI and anatomo-pathological results after radical prostatectomy].

Magnetic Resonance Imaging of 20 patients with local prostatic carcinoma was correlated with pathological findings after radical prostatectomy. The tumor was always seen with an hyposignal, associated in 6 cases with benign prostatic hyperplasia. Extracapsular extension was correctly evaluated (17 cases/20). There were 6 false positive diagnosis of seminal vesicles extension among 40 cases because of an hyposignal in intact vesicles and one false negative diagnosis. Magnetic Resonance Imaging is a good exam to appreciate loco-regional extension of prostatic carcinoma.

Humans↗
PubMed1990

Influence of hormono- and/or chemotherapy on the MXT mouse mammary tumor as monitored by 31P MRS.

We describe the early in vivo modifications that occurred in the MXT mouse hormone sensitive mammary tumor following various treatments which were monitored by 31P NMR spectroscopy. The MXT mouse mammary tumor was subjected to clinically relevant low-dose chemotherapy, i.e. seven cycles of 20 mg/kg cyclophosphamide (CPA) with or without an attempt at estrogenic cell recruitment prior to the CPA treatment. NMR measurements were begun at the end of the CPA treatment in order to evaluate the remaining 'long-term' chemotherapy-induced modifications within the MXT tumors. Statistical analyses performed on the 31P NMR parameters revealed that treatment had induced significant effects on bATP/PCr, Pi/PCr and PME/PDE only, with PCr being the most discriminating index. Its presence within MXT tumors was verified by means of an analysis of perchloric extracts. The results indicate a relative decrease of PME/PDE and a better conservation of PCr within the CPA-treated group as compared to the control one. This feature appeared even prior to any macroscopic modifications, as was the case within the group which contained tumors smaller than 120 mm2, and where no significant differences appeared between the mean sizes of the MXT cancers. In contrast, within the G2 group, which contained tumors equal to or larger than 120 mm2, CPA significantly slowed down tumor growth, while the administration of estradiol (E2) prior to CPA treatment antagonized the positive CPA-induced therapeutic effect. In conclusion, the non-invasive follow-up of the chemotherapeutic treatment of a clinically relevant mammary tumor model by 31P NMR spectroscopy backed up by statistical analyses revealed metabolic changes that appeared well before any modifications in histopathology or growth.

Animals↗
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↗
PubMed1985

[Contribution to proton nuclear magnetic resonance imaging in multiple sclerosis. Contribution of a multiple spin echo sequence].

Single or multiple parenchymatous anomalies were detected in 48 of 49 patients with multiple sclerosis by proton magnetic resonance imaging (MRI) combined with a spin-echo sequence in the 4 planes of the section passing through the ventricular bodies. Lesions were identified in the frontal, orbital and particularly juxta-ventricular white substance, and were of variable appearance, the most common being spots in the parenchyma and juxta-ventricular bands. A limited number of sections is sufficient for the MRI study of anomalies in clinically defined multiple sclerosis, the diagnostic value of this examination suggested by these findings requiring confirmation by prospective studies.

Adolescent↗
PubMed1984

[Evaluation of left ventricular function and regional kinetics following myocardial infarction. Comparative study of angiocardiography, echography and radionuclide angiography].

Left ventricular function and regional wall motion were studied three weeks after a myocardial infarction in 25 patients who had undergone L.V. monoplane cineangiography. The patients were studied by echocardiography (TM and 2D) and radionuclide angiography. Evaluation of global ejection fraction provides evidence of a close correlation between left ventricular angiography and radionuclide examination (r= 0.79). Measurement of ejection fraction by echocardiography (TM) remains clearly correlated with the same evaluation by angiography (r = 0.68). The correlations are markedly increased in the patients without significant wall motion defects (r = 0.87 for radionuclide angiography and r = 0.82 for echographic measurement). Sensitivity in the detection of L.V. aneurysms is excellent with our method of radionuclide examination (12/13) and can be compared with angiography (12/13). Two-dimensional echocardiography performed on a routine basis is less sensitive than radionuclide angiography in this diagnosis (4/13).

Angiocardiography↗
PubMedDate not supplied

Technique for MRI of ocular motility.

Our goal was to improve existing MR methods used in the assessment of ocular motility in the horizontal gaze direction, by using high resolution 20 s images and an experimental setup that prevents physiologically induced head motion in patients and eye convergence to the fixation point, thus improving the analysis of the relationships between the eyeball and the right muscle bellies in horizontal gaze exploration. The method has potential clinical applications for the diagnosis and/or follow-up of complex strabismus.

Eye Movements↗
PubMedDate not supplied

MXT mammary tumor treated by low dose chemotherapy. A 31P-NMR and 1H-MRI study.

The effects induced by a low dose cyclophosphamide treatment (CPA) along with an attempt of estradiol-17-beta (E2) cell recruitment, on the bioenergetics and the phosphomonoesters/phosphodiesters (PME/PDE) ratio in the transplantable MXT mouse mammary tumor have been studied by 31P-NMR spectroscopy in vivo. Our results show that neither ovariectomy (OO) nor the additional low dose E2 + CPA treatment significantly decreased tumor growth, whilst E2 + CPA treatment induced significant modifications compared to values recorded in tumors grafted on intact or ovariectomized animals, of all peak height ratios but PME/PDE, which further remained at a constant value during tumor growth.

Animals↗