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J Remy

Publications and source records attributed to J Remy.

At least 19 recordsLinked to original sources
PubMed2006

Low-dose ECG-gated 64-slices helical CT angiography of the chest: evaluation of image quality in 105 patients.

The purpose of this study was to evaluate image quality of low-dose electrocardiogram (ECG)-gated multislice helical computed tomography (CT) angiograms of the chest. One hundred and five consecutive patients with a regular sinus rhythm (72 men; 33 women) underwent ECG-gated CT angiographic examination of the chest without administration of beta blockers using the following parameters: (a) collimation 32 x 0.6 mm with z-flying focal spot for the acquisition of 64 overlapping 0.6-mm slices, rotation time 0.33 s, pitch 0.3; (b) 120 kV, 200 mAs; (c) use of two dose modulation systems, including adjustment of the mAs setting to the patient's size and anatomical shape and an ECG-controlled tube current. Subjective and objective image quality was evaluated by two radiologists in consensus on 3-mm-thick scans reconstructed at 55% of the response rate (RR) interval. The population and protocol characteristics included: (a) a mean [+/-standard deviation (SD)] body mass index (BMI) of 24.47 (+/-4.64); (b) a mean (+/-SD) heart rate of 72.04 (+/-15.76) bpm; (c) a mean (+/-SD) scanning time of 18.3 (+/-2.73) s; (d) a mean (+/-SD) dose-length product (DLP) value of 260.57 (+/-83.67) mGy/cm; (e) an estimated average effective dose of 4.95 (+/-1.59) mSv. Subjective noise was depicted in a total of nine examinations (8.5%), always rated as mild. Objective noise was assessed by measuring the standard deviation of pixel values in a homogeneous region of interest within the trachea and descending aorta; SD was 15.91 HU in the trachea and 22.16 HU in the descending aorta, with no significant difference in the mean value of the standard deviations between the four categories of BMI except for obese patients, who had a higher mean SD within the aorta. Interpolation artefacts were depicted in 22 patients, with a mean heart rate significantly lower than that of patients without interpolation artifacts, rated as mild in 11 patients and severe in 11 patients. The severity of interpolation artefacts was significantly linked to a low heart rate in affected patients. The overall image quality of CT scans was rated as diagnostic in 94 patients (89.5%) while 11 examinations (10.5%) were found to be partially nondiagnostic owing to the cyclic presence of severe interpolation artefacts, which can be compensated for by additional reconstructions at a different temporal window. In these cases, interpolation artefacts could have been avoided by reducing the pitch from 0.3 to 0.2 at the expense of increased patient dose. Low-dose ECG-gated CT angiograms of the chest can be obtained in routine clinical practice with 64-slice CT technology without altering the diagnostic value of CT scans.

Adolescent↗
PubMed2005

Numerical investigation of the discharge characteristics of the pulsed discharge nozzle.

The characteristics of the plasma generated by a pulsed discharge slit nozzle (PDN) are investigated. The PDN source is designed to produce and cool molecular ions creating an astrophysically relevant environment in the laboratory. A discharge model is applied to this system to provide a qualitative as well as a quantitative picture of the plasma. We find that the plasma's properties and behavior are characteristic of those of a glow discharge. We model the electron density and energy, as well as the argon ion and metastable atom number density. The results reveal a high abundance of metastable argon atoms in the expansion region, which is more than one order of magnitude higher than the abundance of electrons and ions. These findings confirm experimental observations, which concluded that large molecular ions are dominantly formed through Penning ionization of the neutral molecular precursors seeded in the supersonic expansion of argon gas. The simulations presented here will help optimize the yield of formation of molecular ions and radicals in the PDN source; they will also provide key physical insight into the characteristics of interstellar molecules and ions analogs in laboratory experiments.

Journal Article↗
PubMed2004

[Imaging pulmonary embolism].

The diagnostic performance of computed tomography images of pulmonary embolism is directly related to the acquisition parameters. Any physician evaluating these scans must have proper knowledge of the acquisition, injection, reconstruction, and radiation parameters. Cardiac gating and morphological and functional image processing should be understood since they are now routine techniques particularly important for preoperative assessment of chronic thromboembolism. Elementary knowledge of the imaging techniques reduces the risk of diagnostic limitations. Understanding these techniques does not require any particularly advanced knowledge of physics, data processing or technology, but is necessary to chose the appropriate technical facilities and equipment adapted for diagnostic purposes. While specific training is not a prerequisite, interpretation of an angioscan of the pulmonary vessels does require precise knowledge of the pulmonary anatomy in addition to the technical knowledge mentioned above. Proper analysis may reach the 4th and 5th generation vessels. Different analysis methods have been developed which take into account the technical parameters and avoid the need for serial images. Each slice can then be analyzed within an acquisition Volume. Differential diagnosis is also very technique-dependent, minimally operator-dependent but highly machine-dependent. Differential diagnosis becomes less and less a problem with advancing equipment. Sufficient knowledge of the physiological and pathogenic basis is relatively easy to retain.

Angiography↗
PubMed2004

[Contribution of thoracic imaging reconstruction techniques].

Image reconstruction is a technique based on reprocessing raw data or native images to enhance their diagnostic impact, simplify their analysis, or establish a more comprehensive picture. Applied to computed tomography, the only technique examined here, image reconstruction is at the crossroads between two apparently contradictory affirmations, i.e. all information is contained in the cross-sectional images, and image processing makes multiple-plane segmentation of an anatomic volume obsolete. In 2004, reality associates these two affirmations in a combination weighted according to the clinical situation. Clinicians prescribing imaging explorations must be well aware of recent advances in technology and must keep up to date on the different ways imaging data can be exploited, particularly for upcoming applications for functional, metabolic, and molecular imaging.

Humans↗
PubMed2004

[Endocrine and pulmonary histiocytosis: a case diagnosed through stereotoxic biopsy].

INTRODUCTION: Despite intensive investigation, the pulmonary lesions of Langerhans cell histiocytosis can sometimes prove difficult to yield a diagnosis of this potentially multi-focal disease. CASE REPORT: We report the case of a sixteen year old woman, who presented with a hypothalamo-hypophyseal mass associated with endocrine clinical signs, dyspnoea, and micro-nodular pulmonary lesions on computerised tomography. A Langerhans cell histiocytosis was initially suspected, but then thought unlikely in the light of negative pulmonary investigations and spontaneous regression of the pulmonary lesions. However, an increase in the size of the cerebral mass prompted a brain biopsy finally confirming the diagnosis of Langerhans cell histiocytosis. CONCLUSIONS: This case report identifies a possible dissociation between the clinical courses of cerebral and pulmonary Langerhans cell histiocytosis, and confirms the usefulness of extra-thoracic biopsies in making a diagnosis on the disseminated form of the disease.

Adolescent↗
PubMed2001

Dose reduction in spiral CT angiography of thoracic outlet syndrome by anatomically adapted tube current modulation.

The aim of this study was to evaluate dose reduction in spiral CT angiography of the thoracic outlet by on-line tube-current control. Prospectively, 114 patients undergoing spiral CT angiography of the subclavian artery for thoracic outlet arterial syndromes were evaluated with and without tube-current modulation at the same session (scanning parameters for the two successive angiograms, one in the neutral position and one after the postural maneuver): 140 kV; 206 mA; scan time 0.75 s; collimation 3 mm; pitch = 1). The dose reduction system was applied in the neutral position in the first 92 consecutive patients and after postural maneuver in the remaining 22 consecutive patients. Dose reduction and image quality were analyzed in the overall study group (group 1; n = 114). The influence of the arm position was assessed in 44 of the 114 patients (group 2), matched by the transverse diameter of the upper thorax. The mean dose reduction was 33% in group 1 (range 22-40%) and 34% in group 2 (range 26-40%). In group 2 the only difference in image quality was a significantly higher frequency of graininess on low-dose scans compared with reference scans whatever the patient's arm position, graded as minimal in 38 of the 44 patients (86%). When the low-dose technique was applied after postural maneuver in group 2: (a) the mean dose reduction was significantly higher (35 vs 32% in the neutral position; p = 0.006); (b) graininess was less frequent (82 vs 91% in the neutral position); and (c) the percentage of graininess graded as minimal was significantly higher (83 vs 70% in the neutral position; p = 0.2027). On-line tube-current modulation enables dose reduction on high-quality, diagnostic spiral CT angiograms of the thoracic outlet and should be applied during data acquisition in the neutral position and after postural maneuver for optimal use.

Adult↗
PubMed2001

Diagnosing thoracic outlet syndrome: contribution of provocative tests, ultrasonography, electrophysiology, and helical computed tomography in 48 patients.

OBJECTIVE: To evaluate the diagnostic usefulness of provocative tests, Doppler ultrasonography, electrophysiological investigations, and helical computed tomography (CT) angiography in thoracic outlet syndrome (TOS). PATIENTS AND METHODS: We prospectively evaluated 48 patients with a clinical suspicion of thoracic outlet syndrome. Standardized provocative tests, an electromyogram and somatosensory evoked responses, a Doppler ultrasonogram, and a helical CT arterial and/or venous angiogram with dynamic maneuvers were done on each patient. The final diagnosis was established by excluding all other causes based on all available data. The agreement between the results of each investigation and the final diagnosis was evaluated. RESULTS: Provocative tests had mean sensitivity and specificity values of 72% and 53%, respectively, with better values for the Adson test (positive predictive value [PPV], 85%), the hyperabduction test (PPV, 92%), and the Wright test. Using several tests in combination improved specificity. Doppler ultrasonography visualized vascular parietal abnormalities and confirmed the diagnosis in patients with at least five positive provocative tests. Electrophysiological studies were useful mainly for the differential diagnosis or for detecting concomitant abnormalities. Although helical CT angiography provided accurate information on the location and mechanism of vascular compression, the usefulness of this investigation for establishing the diagnosis of TOS and for obtaining pretherapeutic information remains unclear.

Adult↗
PubMed2001

Multidimensional imaging of the thorax: practical applications.

Over the past decade, faster CT scan times, thinner collimation, and the development of multirow detectors, coupled with the increasing capability of computers to process large amounts of data in short periods of time, have lead to an expansion in the ability to create diagnostically useful two-dimensional (2D) and three-dimensional (3D) images within the thorax. Applications within the thorax include, but are not limited to, evaluation of pulmonary and systemic vasculature, evaluation of the tracheobronchial tree, and delineation of diffuse lung disease. Pulmonary nodule volume and growth can be more accurately predicted, and represents an improvement in the evaluation of the solitary pulmonary nodule. Multiplanar images increase our understanding of thoracic anatomy and can help to guide bronchoscopic procedures. Because there are strengths and weaknesses to all the reconstruction algorithms, the utility of any given technique is dependent on the clinical question to be answered. For instance, although maximum intensity projection imaging (MIP) is helpful in the evaluation of micronodular lung disease, it is of little value in the diagnosis of aortic dissection. As the ability to generate faster and more precise multidimensional images grow, the demand for such imaging is likely to increase. In this review, the authors discuss the various reconstruction techniques available, followed by a discussion of the clinical applications.

Humans↗
PubMed2001

Thin-section CT finding in 250 volunteers: assessment of the relationship of CT findings with smoking history and pulmonary function test results.

PURPOSE: To evaluate the frequency and morphologic characteristics of air trapping in volunteers with various smoking habits. MATERIALS AND METHODS: Two hundred fifty volunteers (133 women, 117 men; mean age, 39 years), including 144 smokers, 47 ex-smokers, and 59 nonsmokers, prospectively underwent inspiratory and expiratory high-spatial-resolution computed tomography (CT) and pulmonary function tests (PFTs). The frequency and characteristics of air trapping were evaluated according to the population's smoking habits and PFT results. RESULTS: The overall frequency of air trapping was 62% (155 of 250 subjects). Lobular air trapping was depicted in 117 (47%) of 250 subjects, without significant differences among smokers (n = 91), ex-smokers (n = 33), and nonsmokers (n = 31) (P =.118). Segmental and lobar air trapping (38 [15%] of 250) were more frequent among smokers (24 [26%] of 91) and ex-smokers (nine [27%] of 33) (P <.001). No relationship was found between air trapping and functional indexes of small-airway disease when the CT pattern of air trapping was considered. The strongest relationship between CT abnormalities and functional alterations at the small-airways level was between inspiratory CT features of bronchiolitis: ground-glass opacity, ill-defined micronodules, bronchiolectasis, and air flow at low lung volumes. CONCLUSION: Whereas a significant relationship was observed between segmental and lobar air trapping and cigarette consumption, lobular air trapping was not found to reflect functional impairment at the small-airways level.

Adult↗
PubMed2001

Peripheral pulmonary arteries: how far in the lung does multi-detector row spiral CT allow analysis?

PURPOSE: To analyze the influence of multi-detector row spiral computed tomography (CT) on identification of peripheral pulmonary arteries. MATERIALS AND METHODS: Peripheral pulmonary arteries were analyzed on optimally opacified contrast material-enhanced spiral CT angiograms in 30 patients devoid of pleuroparenchymal disease who underwent scanning with multi-detector row CT (collimation, 4 x 1 mm; pitch, 1.7-2.0; scanning time, 0.5 second). Two series of scans were systematically generated from each data set, 1.25-mm-thick (group 1) and 3-mm-thick (group 2) sections, leading to the analysis of 600 segmental (20 arteries per patient), 1,200 subsegmental (40 arteries per patient), 2,400 fifth-order (80 arteries per patient), and 4,800 sixth-order (160 arteries per patient) pulmonary arteries in each group. RESULTS: Multi-detector row CT with reconstructed scans of 1.25-mm-thick sections (group 1) allowed (a) analysis of a significantly higher percentage of subsegmental arteries (94% in group 1 vs 82% in group 2; P <.001) and (b) a significantly higher percentage of fifth- and sixth-order arteries, respectively, identified in 74% and 35% of cases in group 1 and 47% and 16% in group 2 (P <.001). The causes for inadequate depiction of subsegmental branches in group 1 were partial volume effect (43%), anatomic variants (39%), and cardiac (17%) and respiratory (1%) motion artifacts. CONCLUSION: Multi-detector row CT with reconstructed scans of 1.25-mm-thick sections enables accurate analysis of peripheral pulmonary arteries down to the fifth order on spiral CT angiograms.

Angiography↗
PubMed2000

Helical CT angiography of thoracic outlet syndrome: functional anatomy.

OBJECTIVE: The objective of this study is to determine the anatomic characteristics of the thoracic outlet in symptomatic patients before and after postural maneuver. SUBJECTS AND METHODS: Seventy-nine symptomatic patients (61 female patients [group 1]; 18 male patients [group 2]; mean age, 38 years) underwent helical CT angiography of the thoracic apices in the neutral position and after a postural maneuver, enabling the evaluation of the functional anatomy of the musculoskeletal and arterial structures of the ipsilateral thoracic outlet. RESULTS: A statistically significant difference was found between the distribution of the distances (maximum and costosubclavian) measured in the neutral position and after postural maneuver in groups 1 and 2. The median value of these distances was smaller after postural maneuver in groups 1 and 2. A statistically significant difference was found between the distribution of the distances (maximum and costosubclavian) measured in patients of group 1 with arterial stenosis and in patients of group 1 without arterial stenosis. A slight indentation of the anterior wall of the subclavian artery when it arches around the anterior scalene muscle was observed in 39 patients (64%) in group 1 and in 11 patients (61%) in group 2 in the neutral position, in 19 patients (31%) in group 1 and in six patients (33%) in group 2 after the postural maneuver. The predominant positional changes of the vascular structures were the posteroanterior displacement of the subclavian vessels observed in groups 1 and 2, the arch made by the subclavian artery above the first rib in 40 patients (66%) in group 1 and nine patients (50%) in group 2, and the posterior displacement of the axillary artery observed in 36 patients (59%) in group 1 and in 12 patients (67%) in group 2. CONCLUSION: Helical CT shows significant narrowing of the costoclavicular space after postural maneuver in symptomatic patients.

Adolescent↗
PubMed2000

Clinical value of thin collimation in the diagnostic workup of pulmonary embolism.

OBJECTIVE: We report our experience with thin-collimation helical CT in a population of patients suspected of having pulmonary embolism. CONCLUSION: Thin-collimation helical CT provided technically acceptable examinations for pulmonary embolism in 360 patients (97%). In this population, CT revealed pulmonary embolism in 104 patients (29%), negative findings in 217 patients (59%), indeterminate findings in 39 patients (10%), and alternative diagnoses in 65% of patients with negative or inconclusive findings. Ventilation-perfusion scanning and Doppler sonography of the lower extremities were performed in 158 (44%) and 133 patients (37%), respectively, whereas pulmonary angiography was performed in 27 patients (7.5%). The estimated false-negative rate of helical CT was 5%.

Adolescent↗
PubMed1999

Spiral CT angiography of the pulmonary circulation.

Spiral computed tomographic (CT) angiography of the pulmonary circulation has emerged recently as a potential useful diagnostic method for the evaluation of the pulmonary circulation. As a minimally invasive examination, this technique is becoming widely available and has progressively replaced conventional and digital pulmonary angiography as the standard diagnostic imaging modality of the pulmonary circulation. The purpose of this review is to capture the current state of the art of the technical aspects of spiral CT angiography, with special emphasis on the post-processing techniques currently available. As CT is responsible for a considerable part of the medical radiation dose applied to the population, the current trends for dose saving will also be emphasized. With regard to the clinical applications of spiral CT angiography, its introduction into the diagnostic work-up of pulmonary embolism has considerably modified the diagnostic algorithms. Our 8-year review of the literature presented herein is expected to provide the readers with a basis for formulating an informed opinion on this topic. In addition, a large number of congenital and acquired disorders of the pulmonary circulation are also relevant to this technique, and these indications are discussed in the context of the corresponding therapeutic options. Owing to the multiple possibilities inherent to this technique, spiral CT has the potential for cost savings without reduction in image quality or diagnostic accuracy.

Aneurysm↗
PubMed1999

[The respective role and limitations of pulmonary angiography, thoracic computed tomography, and MRI in the diagnosis of pulmonary embolism].

Spiral or helical angioscanography for the positive or differential diagnosis of pulmonary emboli has become an emerging technique but remains poorly practised and has been little assessed scientifically. The optimal conditions to perform the test should be understood. The physician should appreciate in view of a large choice of parameters, the diagnostic value of the result and its reliability proximally and distally. Pulmonary angiography is only indicated when the angioscanography is negative according to the degree of clinical and paraclinical suspicion. Angiography magnetic resonance imaging is a diagnostic test full of promise which does not yet have its place in routine practice.

Angiography↗
PubMed1998

Gene transfer with lipospermines and polyethylenimines.

It is an obvious and basic principle that to be efficient, gene therapy requires effective gene transfer followed by adequate gene expression. However, getting DNA, a pro-drug, into the cell and into the nucleus, remains a crucially limiting factor. Even recombinant viral methods still show poor performances in clinical situations and non-viral methods are considered classically to be of yet lower efficiency. Here, we consider the mode of action, the nature of the complexes formed with DNA and the transfection potentials of two categories of inert, cationic vectors, the lipospermines and polyethylenimine. Both are among the best vectors currently available for in vitro work. Moreover, polyethylenimine is proving to be a versatile and effective carrier for different in vivo situations, especially for delivering genes into the mammalian brain.

Journal Article↗
PubMed1998

Multiplanar and three-dimensional reconstruction techniques in CT: impact on chest diseases.

The purpose of this review is to capture the current state-of-the art of the technical aspects of multiplanar and three-dimensional (3D) images and their thoracic applications. Planimetric and volumetric analysis resulting from volumetric data acquisitions obviates the limitations of segmented transverse images. Among the 3D reconstruction techniques currently available, the most recently introduced technique, i. e., volume rendering, has to be evaluated in comparison with 3D shaded surface display and maximum or minimum intensity projection. Slabs are useful in detecting and localizing micronodular or microtubular patterns and in analyzing mild forms of uneven attenuation of the lungs. Three-dimensional angiography is helpful in the pretherapeutic evaluation and posttreatment follow-up of pulmonary arteriovenous malformations, in the comprehension of the postoperative reorientation of the pulmonary vessels, in the surgical planning of pulmonary tumors, and in the diagnosis of marginated thrombi. The systemic supply to the lung and superior vena cava syndromes are also relevant to these techniques. In acquired or congenital tracheobronchial diseases including stenosis, extraluminal air and complex airway anatomy, multiplanar and 3D reformations have a complementary role to both transaxial images and endoscopy. New developments are also expected in various topics such as 3D conformal radiation therapy, planning of intraluminal bronchoscopic therapy, virtual endoscopy, and functional imaging of the bronchial tree. Miscellaneous clinical applications are promising in the analysis of diaphragmatic morphology and pathophysiology, in the volumetric quantification of the lung parenchyma, and in the vascular components of the thoracic outlet syndromes.

Angiography↗