Biomedical subjects

I Idy-Peretti

Publications and source records attributed to I Idy-Peretti.

At least 19 recordsLinked to original sources

PubMed2003

MRI texture analysis on texture test objects, normal brain and intracranial tumors.

Texture analysis was performed in three different MRI units on T1 and T2-weighted MR images from 10 healthy volunteers and 63 patients with histologically confirmed intracranial tumors. The goal of this study was a multicenter evaluation of the usefulness of this quantitative approach for the characterization of healthy and pathologic human brain tissues (white matter, gray matter, cerebrospinal fluid, tumors and edema). Each selected brain region of interest was characterized with both its mean gray level values and several texture parameters. Multivariate statistical analyses were then applied in order to discriminate each brain tissue type represented by its own set of texture parameters. Texture analysis was previously performed on test objects to evaluate the method dependence on acquisition parameters and consequently the interest of a multicenter evaluation. Even obtained on different sites with their own acquisition routine protocol, MR brain images contain textural features that can reveal discriminant factors for tissue classification and image segmentation. It can also offer additional information in case of undetermined diagnosis or to develop a more accurate tumor grading.

Adult↗

PubMed2001

Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus.

UNLABELLED: Henry-Feugeas MC, Idy-Peretti I, Baledent O, et al. Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus. Invest Radiol 2001;36:146-154. RATIONALE AND OBJECTIVES: To analyze changes in cerebrospinal fluid (CSF) hydrodynamics in chronic adult hydrocephalus. METHODS: Phase-contrast cine-MR acquisitions were used to explore the ventricular system and the upper ventral cervical spaces of 16 patients. The aqueductal jet was explored in 32 control subjects. RESULTS: The duration of pulsatile caudal CSF flow (ie, CSF systole) was abnormally short in patients with active idiopathic and obstructive hydrocephalus. The duration of CSF cervical systole was normal in patients with stable hydrocephalus. The aqueductal stroke volume could be increased in stable communicating hydrocephalus. Patients who responded to shunting had shortened CSF systoles and hyperpulsatile ventricular patterns. Successful CSF diversion resulted in longer CSF systoles and CSF ventricular patterns that were no longer hyperpulsatile. CONCLUSIONS: Magnetic resonance analysis of CSF flow can show craniospinal dissociation and limitation of CSF outflow from the ventricles in both obstructive and communicating hydrocephalus; it should help determine the response to shunting in communicating hydrocephalus.

Adult↗

PubMed2001

Cerebrospinal fluid dynamics and relation with blood flow: a magnetic resonance study with semiautomated cerebrospinal fluid segmentation.

RATIONALE AND OBJECTIVES: To investigate and measure temporal and amplitude aspects of blood and cerebrospinal fluid (CSF) flow waveform relations. METHODS: A cine phase-contrast magnetic resonance imaging pulse sequence was used to measure blood and CSF flow in 16 healthy subjects aged 27 +/- 4 years. A semiautomated segmentation algorithm was developed to study CSF flow. RESULTS: Standard deviations of the aqueductal and cervical flow measurements carried out by five observers were 1% and 4%, respectively. The peak systolic arterial flow was 1087 +/- 169 mL/min, and the peak cervical CSF flush (173 +/- 59 mL/min) occurred at 5% +/- 3% of the cardiac cycle after the internal carotid systolic peak flow. Peak aqueductal flush flow (13 +/- 5 mL/min) occurred at 21% +/- 7% of the cardiac cycle after the internal carotid systolic peak flow. CONCLUSIONS: The CSF segmentation algorithm is reproducible. Brain expansion was quickly regulated by a major extracerebral CSF flush flow, whereas ventricular CSF made only a very small contribution.

Adolescent↗

PubMed2000

Origin of subarachnoid cerebrospinal fluid pulsations: a phase-contrast MR analysis.

Cerebrospinal fluid (CSF) pulsations result from change of blood volume in the closed craniospinal cavity. We used cine phase contrast MR analysis to determine whether spinal CSF pulsations result from spinal vascular pulsations or intracranial subarachnoid pulsations, whether intracranial CSF pulsations result from intracranial large arteries pulsations or cerebrovascular bed changes. We performed a quantified physiological mapping of CSF velocity waveforms along the craniospinal axis. Thirty-six volunteers participated in the study. MR acquisitions were obtained at the intracranial level, the upper, midcervical, cervicothoracic, mid thoracic, and/or the thoracolumbar levels. The temporal velocity information were plotted as wave form and key temporal parameters were determined and analyzed; intervals from the R wave to the onset of CSF systole, to CSF systolic peak, to the end of systole, as well as duration of systole. Three kinds of dynamic channels could be differentiated along the spinal axis, the lateral, medioventral and mediodorsal channels. Lateral spinal CSF pulse waves show significant craniocaudal propagation. No such significant progression was detected through the medial channels along the spine. Through the medial channels, a cephalic progression was observed from the upper cervical level to the intracranial level. At the craniocervical junction, mediodorsal CSF systole appeared the earliest one whereas in the anterior intracranial basal cistern, CSF systole appeared delayed. In conclusion, spinal CSF pulsations seem to result mainly from intracranial pulsations in the lateral channels, whereas local vascular pulsations could modify CSF pulse wave mainly in the medial channels. At the craniocervical junction, our results suggest that blood volume change in the richly vascularised cerebellar tonsils is the main initiating factor of CSF systole; and that spinal vascular pulsations could be considered as an additional early and variable CSF pump.

Adolescent↗

PubMed2000

[MR diffusion and perfusion imaging in clinical practice].

MR functional imaging, due to the improvement in ultra-speed imaging technology such as echo-planar imaging, has become a very powerful technique since the beginning of the nineties. This imaging technique is divided into diffusion imaging, perfusion imaging and cerebral activation. Diffusion imaging probes the mobility of water molecules characterized by a diffusion coefficient called the apparent diffusion coefficient (ADC) for biological tissues. Perfusion imaging gives hemodynamic information due to the regional cerebral blood volume by the use of contrast agents such as chelates of gadolinium carrying strong magnetic susceptibility. Both imaging techniques can provide information in a wide nosological range : cerebral ischemia, in the acute phase and in case of intracranial tumors, contributing to tumoral grading, localizing the site of biopsy, and assessing response to therapy (after radiotherapy for example). Nevertheless, a wide range of domains remains incompletely studied, for example cerebral white matter diseases and neurodegenerative diseases. For clinical applications, a precise knowledge of the potentials of both techniques and their limitations is needed. Limitations result from the large number of often patient-related parameters, imaging technique (perfusion) and data analysis. Powerful software has been developed in the workstation environment. Thus this imaging technique requires up-to-date equipment and close collaboration between clinical and research teams for optimal efficiency.

Brain Ischemia↗

PubMed1999

[Dynamic MRI in the evaluation of syringomyelic cysts].

We report the results of a MR velocity study of the cerebrospinal fluid including 36 patients with syringomyelic cysts (25 with a foraminal syringomyelia, 7 with a post-traumatic cyst, 2 with a tumoral spinal cord cyst, 2 with a spinal arachnoiditis). Velocity measurements were performed in the cysts and in the pericystic subarachnoid spaces and compared with clinical data, evolutive pattern of the disease, cyst volume, degree of stenosis of the cranio-cervical junction (in patients with Chiari I) or of the spinal canal (in post-traumatic cases), and with the extension of the cyst (post-traumatic cases). Cyst velocities correlated in the pre operative course with the clinical status of the patients and with the volume of the cyst. Correlation with the degree of foraminal stenosis was uncertain and no correlation was found with the duration of the disease course. In the post-operative course cyst velocity decreased and velocity of the subarachnoid spaces increased. Onset of the systolic peak occurred sooner in the cyst than in the subarachnoid spaces. We believe that this point may be important in the pathogenesis of the disease. We consider that systolic and diastolic cyst velocities respectively greater than 2.3 cm/s and 1.5 cm/s in the post-operative course may characterize aggressive cysts. In the future comparison of velocity measurements in patients with Chiari I without syrinx and patients with Chiari I related syringomyelia may be helpful for a better understanding of the natural history of the syringomyelia.

Adult↗

PubMed1998

Lymphedematous skin and subcutis: in vivo high resolution magnetic resonance imaging evaluation.

Physico-chemical and morphologic parameters of skin layers and subcutaneous tissue in lymphedematous limb were studied in vivo using magnetic resonance imaging. High resolution images were obtained with a depth resolution of about 70 microm, using a specific surface gradient coil specially designed for skin imaging and connected to a standard whole-body imager at 1.5 T. Twenty-one patients with unilateral lower extremity lymphedema (11 primary and 10 secondary) were examined. Skin thickness, relaxation times, and relative proton density were calculated in lymphedematous limbs and in contralateral extremities. In diseased limbs, the average skin thickness (2.17 mm) was significantly larger (p = 1.5 x 10(-4)) than that of contralateral limb (1.14 mm). Major cutaneous alterations due to lymphedema took place in dermis. In lymphedematous dermis, the significant increase of relaxation time values could be due to a shift in the equilibrium of water inside this tissue in relation to the interactions between macromolecules and water molecules. In lymphedematous epidermis our results showed an increase in the number of free water protons. Information about water and fat distribution in lymphedema was also obtained using chemical shift weighted images. Our results demonstrated a water retention diffusely spread over the entire dermis, and an important fluid retention located in the interlobular spacing and beside the superficial fascia. Inside the subcutis, the mean thickness of the superficial fat lobules was increased more than that of the deep fat lobules. From all the various measurements we could not distinguish primary from secondary lymphedema.

Adolescent↗

PubMed1996

Standard and high resolution magnetic resonance imaging of glomus tumors of toes and fingertips.

BACKGROUND: High-resolution magnetic resonance imaging (MRI) of subungual glomus tumors has been recently reported. OBJECTIVE: Our purpose was to compare high-resolution MRI and standard MRI for the diagnosis of 44 glomus tumors of the toes and fingertips. METHODS: Glomus tumors (11 cases) were first examined by MRI with a commercial surface coil (set 1). Thirty-three other glomus tumors and one tumor from set 1 were then examined with a high-resolution module designed for skin imaging (set 2). RESULTS: All 44 glomus tumors were identified with MRI. The limits of the tumors were detected in 54% of set 1 and 100% of set 2. A capsule was present in most cases, but was incomplete or absent in eight cases. Subtypes of glomus tumors were more easily differentiated in set 2. CONCLUSION: Standard MRI was adequate to detect glomus tumors, but high-resolution MRI assessed tumor characteristics more accurately.

Adolescent↗

PubMed1996

The lunula: a magnetic resonance imagining approach to the subnail matrix area.

High-resolution sagittal magnetic resonance images depict an oval area in the dermis beneath the nail matrix that gives a particular signal. This study defines the magnetic resonance imaging characteristics of this area and examines its correlation with the lunula. A high-resolution surface gradient coil specially designed for skin imagining was used on a 1.5 T magnetic resonance unit. The subnail matrix (SNM) areas of 12 subjects had a significantly longer T2 relaxation time and a higher enhancement ratio after injection of gadolinium than did the nail bed dermis. The length of the SNM area distal to the free edge of the proximal nail fold was highly correlated with the length of the lunula (R = 0.98) in 30 fingers and 10 toes. The total length of the SNM area was somewhat correlated with the nail thickness (R = 0.86) in 30 fingers. The histology and microvascularization of the subungual tissue in 21 fingers showed that this SNM area had specific features: The area was composed of loose connective tissue without bundles, and the reticular and subdermal vascular networks had large regular meshes in this oval area. The lunula is shown to be linked to a well-defined area in the underlying dermis with a specific histology and microvascularization.

Adult↗

PubMed1996

MR imaging of digital mucoid cysts.

PURPOSE: To assess the usefulness of magnetic resonance (MR) imaging in the diagnosis and clarification of the physiopathology of digital mucoid cysts. MATERIALS AND METHODS: Twenty-three patients (14 women, nine men; aged 52-75 years) with mucoid cysts underwent MR imaging at 1.5 T with a local surface gradient coil. The pixel size was 117 microns in one direction. T2 relaxation times were measured. Contrast material was intravenously administered in 15 patients. RESULTS: All mucoid cysts had high signal intensity and sharp borders on T2-weighted images. Intracystic septa were present in nine patients (39%). Most cysts were solitary (n = 13) and/or in the proximal nail fold (n = 16). Satellite cysts were present in five patients. Nineteen patients (83%) had cysts with pedicles that extended to the joint. Osteoarthritis of the distal interphalangeal joint was present in 16 patients (70%). Five patients (22%) had multiple flattened cysts that were usually independent of the joint. In seven patients (30%), MR images showed cysts beneath the nail plate. CONCLUSION: Digital mucoid cysts may be polymorphic. MR imaging is helpful when cysts are in the nail bed.

Contrast Media↗

PubMed1995

Subungual glomus tumors: evaluation with MR imaging.

PURPOSE: To determine the magnetic resonance (MR) imaging features of subungual glomus tumors. MATERIALS AND METHODS: Thirty-one patients with a clinical suspicion of glomus tumor and 10 control subjects underwent MR imaging at 1.5 T. MR images of normal glomus bodies of a cadaver finger were correlated with histologic slices. With a local surface gradient coil, the pixel size reached 117 microns in one direction. Relaxation times were measured. Gadoterate meglumine was injected in 19 patients. RESULTS: Normal glomus bodies were visualized in the reticular dermis of the nail bed. Twenty-seven of 28 pathologically confirmed glomus tumors were detected with MR imaging. A peripheral capsule was present in most tumors. The nail matrix was compressed in 13 cases. The authors were able to differentiate three subtypes of glomus tumors (vascular, solid, and myxoid) on the basis of relaxation times and enhancement characteristics. Four patients had mucoid cysts or angioma in the nail bed. CONCLUSION: MR imaging can help accurately define the location and limits of glomus tumors before excision.

Adult↗

PubMed1994

Magnetic resonance imaging: a new tool in the diagnosis of tumours of the nail apparatus.

Tumours of the nail apparatus are often the subject of diagnostic dilemma. Until now, no reliable imaging methods have been available to assess these lesions correctly. We report the results of high and very high-resolution magnetic resonance imaging (MRI), which have been correlated with the anatomical findings in 14 cases of nail apparatus pathology, and discuss the possible contribution of MRI to diagnosis. With very high-resolution MRI, accurate analysis of the anatomy of the nail apparatus is possible, and lesions as small as 1 mm can be detected. An expansive process can be excluded when results are negative. Glomus tumour, mucoid pseudocyst, fibrokeratoma, and exostosis can be differentiated because of their different MRI characteristics. This is of importance when the exact nature of a subungual tumour cannot be determined by clinical findings alone. Measurement, determination of the exact localization of the tumour, and the study of its relationship to the other structures, can provide guidance for subsequent surgical procedures. MRI is reliable and accurate in the delineation of lesions, and provides a new tool for the investigation of pathology of the nail apparatus.

Adolescent↗

PubMed1994

In vivo hydration profile in skin layers by high-resolution magnetic resonance imaging.

In recent years magnetic resonance imaging has become a very efficient tool for in vivo quantification of water content and water behavior in living tissues. We have applied this technique to the study of the in vivo hydration profile in heel skin layers by quantification of the mobile water proton density versus depth. Effects of a bath, a moisturizer and repeated soaping are present. Hydration profiles by magnetic resonance imaging delineate two different structures in stratum corneum: an outer layer where hydration can be modified by external mechanisms and an inner layer where hydration is not altered. The main interest of this method lies in the fact that the physical signal is exactly located, as spatial encoding is the basis of in vivo imaging. This method differs from other noninvasive methods which acquire an averaged signal from a nondelimited volume of interest.

Administration, Topical↗

PubMed1993

High-precision MR velocity mapping by 3D-Fourier phase encoding with a small number of encoding steps.

The final result of Fourier velocity mapping is a set of images, each representing the spatial distribution of spins at a given velocity. To acquire data in a short time, the number of encoding gradient steps must be as small as possible, but this can mean sacrificing velocity resolution. We used interpolation methods to obtain high velocity resolution with a small number of encoding steps involving linear interpolation from 16 encoding steps or more and zero-filling interpolation from two to eight encoding steps. Velocity measured by interpolated Fourier-flow encoding agreed well with values obtained using a calibrated phantom. A simulation of noise on the images of the phantom showed that, for a given acquisition time, increasing number of encoding steps in the Fourier flow encoding gave better precision for velocity measurement than did averaging identical signals in phase-mapping methods.

Algorithms↗

PubMed1993

Temporal and spatial assessment of normal cerebrospinal fluid dynamics with MR imaging.

The purpose of this study was to measure normal cerebrospinal fluid (CSF) pulsations within the intracranial and upper cervical subarachnoid spaces and the ventricular system. Phase contrast cine MR sequences were performed in sagittal and axial planes on 13 volunteers with flow encoding in the craniocaudal direction. CSF pulsations displayed considerable variations in healthy subjects, depending both on measurements localization and subjects, with CSF peak velocities ranging from 0 to 7 cm/s. In the subarachnoid spaces, the highest velocities occurred in the anterior location and increased from the cerebellar pontine angle cisterns towards the lower cervical spaces. In the ventricular system, the highest velocities occurred through the aqueduct of Sylvius. CSF flow within the third ventricle seemed to reflect a circular motion. There was a caudal net CSF flow in the aqueduct whereas in the upper cervical spaces net CSF flow was caudal anteriorly and cranial laterally. Velocity profiles of CSF pulsations demonstrated arterial morphology. After the R wave, caudal systolic motion was first observed in the posterior subarachnoid spaces, soon after in the anterior subarachnoid spaces and later in the ventricular system. Considering the morphology of CSF pathways, three successively initiated phenomena may explain the temporal course of CSF motion: the systolic expansion of the main arteries at the base of the brain, the systolic expansion of the cerebrospinal axis and, finally, the systolic expansion of the choroid plexuses.

Adult↗

PubMed1993

Implementation and optimization by the simplex method of a 3D double echo sequence in steady-state free precession.

Under steady-state conditions, the resulting echoes have very complex T1 and T2 relationships. Many authors exploited these echoes in different sequences to produce either T1- or T2-weighted images. The simultaneous acquisition of two echoes in a single sequence provides two images of clearly different contrasts. We implemented such a sequence, in a 3D-acquisition mode, combining the advantages of thin and contiguous slices with those of a multi-echo sequence. The contrast of the images was correlated with theoretical results, derived from Bloch equations. In order to estimate the acquisition parameters (alpha, TE, TR) to obtain an optimal T1- or T2-contrast between two tissues, a computer simulation of these equations was used in conjunction with the simplex method. The results show that this sequence improves the clinical efficiency of MRI, particularly in neurological and articular disease.

Brain↗

PubMed1993

Characterization of the skin in vivo by high resolution magnetic resonance imaging: water behavior and age-related effects.

The age-related modifications of magnetic resonance imaging parameters in the skin have been studied in vivo. Modification of these parameters should provide important information about alterations in water structure and content in aged skin. Relaxation times, T1 and T2, and relative proton density, which corresponds to the mobile water proton fraction of tissues, have been measured on people under age 40 and over 70 on a sun-protected area. Results have confirmed in vivo skin layer differentiation through relaxation times performed in a previous study. Moreover, relative proton density quantification has shown that epidermal mobile water is at least twice as abundant as dermal mobile water. No significant age-related T1 and T2 modification could be established, basically because of a large dispersion of values. The main result concerns the upper part of dermis (about 200 microns in thickness) which contains significantly more mobile water protons in chronologic aged skin than in young adult skin. This increase has been related both to an increase of total water content in dermis with age and to an apparent decrease of collagen and proteoglycan content. Associated with alterations of their structure, this decrease reduces macromolecular-water interaction sites. This finding has to be compared with ultrasound evaluation of aged skin, which is characterized by modifications of the echogenicity, related to collagen bundles size and density, in the outer part of dermis, too. Both of the imaging techniques tend to consider the outer part of dermis as one of the privileged sites of skin aging.

Adult↗

PubMed1993

[MRI in the pre-operative evaluation of lesions of the rotator cuff].

The authors report a series of 38 patients who had been examined by MRI and then operated for a rotator cuff syndrome. The correlation between the description of the cuff lesions after MRI and the surgical observations were excellent for 37 patients. In one case MRI showed a false image of tear of the supra spinatus m. on its anterior edge. This was due to a bad knowledge of the anatomy of the muscle and tendon and to a poor orientation of the frontal cut plane. This study was complete with MRI and anatomic study of 12 non embalmed cadaveric shoulders. The results showed that MRI was very sensitive (0.93) and specific (0.94) for the diagnosis of rotator cuff tears. MRI allowed also to show partial tears of the tendons of the rotator cuff. The authors propose a MRI classification of cuff lesions which permits to establish a good surgical planning.

Adult↗