Search PubMed⌕ Search

Biomedical subjects

P Schnyder

Publications and source records attributed to P Schnyder.

At least 19 recordsLinked to original sources
PubMed1999

Three-dimensional cholangio-spiral CT demonstration of a post-traumatic bile leak in a child.

Bilioma is a rare complication of traumatic liver injury, and the precise site of bile leak is often difficult to demonstrate with a non-invasive technique. We report a case of post-traumatic bile leak in a 15-year-old girl in whom spiral CT after intravenous cholangiography allowed excellent preoperative demonstration of the extent of the liver rupture and an exact location of the bile leak. We think that spiral-CT cholangiography could be an accurate, non-invasive technique to investigate the biliary system in cases of paediatric liver trauma.

Adolescent↗
PubMed1999

Turf battles in radiology: how to avoid/how to fight/how to win.

Turf battles have always existed in radiology although recently, we have observed an increase in their numbers and sometimes in their virulence. The main reasons for this increase include the relative plethora of physicians especially in industrialized areas, and the rapid progress and development of medical technology and minimally invasive techniques. These turf battles risk interfering with the over-all medical costs of local health care systems as they will inevitably lead to an increase in the concentration of complex medical devices controlled by different specialties which, in turn, will lead to an increase in number of invasive and noninvasive, diagnostic and therapeutic examinations. The only way that radiologists can hope to maintain control of today's techniques will be if they are willing to offer qualitative expertise in their procedures with full clinical, academic and technological backing similar, or superior to that presented by our respective clinical and surgical colleagues. Furthermore, they should be fully involved in the decisional process and actual purchase of the technological equipment of their entire institution.

Economic Competition↗
PubMed1999

High-resolution ultrasound evaluation of internal jugular venous valves.

Although the presence of valves in the distal portion of the internal jugular veins has been widely described by anatomists and pathologists, their existence remains underscored in the medical literature. We set out to demonstrate their sonographic aspect and to evaluate their morphology, location and prevalence. Seventy-five cadavers were evaluated for the presence and aspect of such valves through neck dissections. Concurrent evaluation of the sonographic character of these structures was performed in another cohort of 75 adults. Valves of the distal portion of the internal jugular veins were found in 93 % of the cadaveric studies. Ultrasonography easily demonstrated the valve leaflets in 87 % of patients; all were observed in the distal portion of the internal jugular (IJ) veins. Sixty percent were bilateral with the majority of unilateral veins found on the right side. High-resolution ultrasonography easily demonstrates valves in the distal portion of the IJ veins which are present in the great majority of persons. Their evaluation may be of use in percutaneous procedures using this venous access.

Aged↗
PubMed1999

Estimation of the noisy component of anatomical backgrounds.

The knowledge of the relationship that links radiation dose and image quality is a prerequisite to any optimization of medical diagnostic radiology. Image quality depends, on the one hand, on the physical parameters such as contrast, resolution, and noise, and on the other hand, on characteristics of the observer that assesses the image. While the role of contrast and resolution is precisely defined and recognized, the influence of image noise is not yet fully understood. Its measurement is often based on imaging uniform test objects, even though real images contain anatomical backgrounds whose statistical nature is much different from test objects used to assess system noise. The goal of this study was to demonstrate the importance of variations in background anatomy by quantifying its effect on a series of detection tasks. Several types of mammographic backgrounds and signals were examined by psychophysical experiments in a two-alternative forced-choice detection task. According to hypotheses concerning the strategy used by the human observers, their signal to noise ratio was determined. This variable was also computed for a mathematical model based on the statistical decision theory. By comparing theoretical model and experimental results, the way that anatomical structure is perceived has been analyzed. Experiments showed that the observer's behavior was highly dependent upon both system noise and the anatomical background. The anatomy partly acts as a signal recognizable as such and partly as a pure noise that disturbs the detection process. This dual nature of the anatomy is quantified. It is shown that its effect varies according to its amplitude and the profile of the object being detected. The importance of the noisy part of the anatomy is, in some situations, much greater than the system noise. Hence, reducing the system noise by increasing the dose will not improve task performance. This observation indicates that the tradeoff between dose and image quality might be optimized by accepting a higher system noise. This could lead to a better resolution, more contrast, or less dose.

Biophysics↗
PubMed1999

[Detection of malignant focal hepatic lesions. Comparison of ultrasonography, computerized tomography during arterial portography, delayed computerized tomography and magnetic resonance imaging].

AIMS: This study was performed to compare the sensitivity of ultrasonography, computerized tomography during arterial portography, delayed computerized tomography, and magnetic resonance imaging to detect focal liver lesions. Forty three patients with primary or secondary malignant liver lesions were studied prior to surgical intervention. METHODS: The results of the imaging studies were compared with intraoperative examination of the liver, intraoperative ultrasonography and pathology results (29 patients). In the non-operated (14 patients) group, we compared the number of lesions detected by each technique. RESULTS: One hundred and forty six lesions were detected. There was 84% sensitivity with computerized tomography during arterial portography, 61.3% with delayed scan, 63.3% with magnetic resonance imaging and 51% with ultrasonography in operated patients. In patients who did not undergo surgery, magnetic resonance imaging was more sensitive in detecting lesions. CONCLUSIONS: In operated and non-operated patients series, CT during arterial portography had the highest sensitivity, but magnetic resonance imaging had the most consistent overall results.

Adult↗
PubMed1998

Pulmonary oedema associated with mitral regurgitation: prevalence of predominant right upper lobe involvement in children.

OBJECTIVE: To evaluate the hypothesis that pulmonary venous congestion and oedema manifested predominantly in the right upper lobe in children with mitral regurgitation occur more frequently than previously thought. MATERIALS AND METHODS: Three radiologists retrospectively and independently reviewed the plain chest radiographs of 54 children (26 girls, 28 boys, age range 2 days-18 years, median 9.5 years) with mitral regurgitation admitted to our institution during a 5-year period. Radiographs showing pulmonary venous congestion and oedema manifested predominantly in the right upper lobe were identified. Clinical records of these patients were studied to exclude other causes of pulmonary disease. RESULTS: Radiographic signs of pulmonary venous congestion and oedema were present in all patients, with redistribution of flow and interstitial oedema in 39 patients (72 %) and alveolar oedema in 15 children (28 %). In 12 (22 %) of 54 children, these findings were localised or predominant in the upper lobe of the right lung; none of the children had predominantly left-sided involvement. CONCLUSIONS: Pulmonary venous congestion and oedema involving predominantly the upper lobe of the right lung in children with mitral regurgitation occur more frequently than previously thought. This finding is useful in the differential diagnosis of right upper lobe abnormalities, such as pneumonia.

Adolescent↗
PubMed1998

Spiral CT aortography: an efficient technique for the diagnosis of traumatic aortic injury.

The objective of this study was to assess the efficiency of spiral CT (SCT) aortography for diagnosing acute aortic lesions in blunt thoracic trauma patients. Between October 1992 and June 1997, 487 SCT scans of the chest were performed on blunt thoracic trauma patients. To assess aortic injury, the following SCT criteria were considered: hemomediastinum, peri-aortic hematoma, irregular aspect of the aortic wall, aortic pseudodiverticulum, intimal flap and traumatic dissection. Aortic injury was diagnosed on 14 SCT examinations (2.9 %), five of the patients having had an additional digital aortography that confirmed the aortic trauma. Twelve subjects underwent surgical repair of the thoracic aorta, which in all but one case confirmed the aortic injury. Two patients died before surgery from severe brain lesions. The aortic blunt lesions were confirmed at autopsy. According to the follow-up of the other 473 patients, we are aware of no false-negative SCT examination. Our limited series shows a sensitivity of 100 % and specificity of 99.8 % of SCT aortography in the diagnosis of aortic injury. It is concluded that SCT aortagraphy is an accurate diagnostic method for the assessment of aortic injury in blunt thoracic trauma patients.

Accidental Falls↗
PubMed1998

Bronchiolitis obliterans organising pneumonia simulating bronchial carcinoma.

Idiopathic bronchiolitis obliterans organising pneumonia (BOOP) is an uncommon but well-recognised condition that usually presents radiologically as bilateral multifocal patchy areas of consolidation on the chest radiograph and on computed tomography (CT). Five cases are described in which the presenting feature was that of a solitary pulmonary nodule. Four of these nodules showed evidence of cavitation and three patients presented with haemoptysis. In all cases the appearances closely resembled bronchial carcinoma.

Adult↗
PubMed1998

Limited CD4+ T-cell renewal in early HIV-1 infection: effect of highly active antiretroviral therapy.

We show that the fraction of proliferating CD4+ lymphocytes is similar in HIV-infected subjects in the early stage of disease and in HIV-negative subjects, whereas the fraction of proliferating CD8+ lymphocytes is increased 6.8-fold in HIV-infected subjects. After initiation of antiviral therapy, there is a late increase in proliferating CD4+ T cells associated with the restoration of CD4+ T-cell counts. These results provide strong support for the idea of limited CD4+ T-cell renewal in the early stage of HIV infection and indicate that after effective suppression of virus replication, the mechanisms of CD4+ T-cell production are still functional in early HIV infection.

Adult↗
PubMed1998

Diagnosis of cerebral venous thrombosis with routine magnetic resonance: an update.

Magnetic resonance imaging and angiography is the technique of choice in the diagnosis and follow-up of cerebral venous thrombosis: Thrombosis appears as an absence of flow void on spin echo images and lack of signal in angiographic techniques. The thrombus signal intensity is different on T1 and T2 spin echo weighted images and evolves according to hemoglobin degradation. Recognition of pitfalls and artefacts related to the different magnetic resonance imaging techniques employed is essential to interpret dural venous sinus thrombosis. In this paper the imaging of 27 patients with cerebral venous thromboses is reviewed. We describe the type of signal abnormalities, the different types of clot- and flow-related artefacts, and the indirect signs of cerebral venous thrombosis.

Adult↗
PubMed1998

[Endovascular treatment of abdominal aortic aneurysm. Preliminary experiences with the Talent endoprosthesis].

BACKGROUND: The treatment of infra-renal abdominal aortic aneurysms (AAA) with endovascular stent-graft prostheses is receiving increasing attention as an alternative to major abdominal surgery. Numerous systems are under clinical investigations. We report our preliminary clinical results with the new Talent straight and bifurcated endografts. METHOD: We treated 5 patients with 3 straight and 2 bifurcated stent-grafts implanted by surgical femoral arteriotomies and placed under fluoroscopic guidance. Control CT and angiographic examinations were performed during an average follow-up of 5.3 months. RESULTS: In the first patient the procedure had to be converted to an open surgical operation to repo sition the distal end of the prosthesis. We had no mortality, or major systemic complication. Three patients had a postimplantation syndrome. All aneurysms showed a decreased size at 3 months, in spite of 3 small persisting leaks. CONCLUSION: The Talent endograft is safe, and efficacious in the endovascular treatment of AAA. This method requires a good cooperation between the vascular surgeon and the interventional radiologist. Learning curves influence preliminary results.

Aged↗
PubMed1997

Magnetic resonance detection of myelodysplasia in children with Currarino triad.

PURPOSE: To evaluate the role of MRI in the detection of myelodysplasia in children with Currarino triad. MATERIALS AND METHODS: Six patients (two girls, four boys, aged 7 months-14 years, mean age 6 years) were studied with MRI, voiding cystourethrogram and barium enema or fistulography. CT and ultrasonography were also performed in two patients. RESULTS: All patients presented with partial agenesis of the sacrum. Three patients suffered from an intermediate form of anorectal malformation (ARM) and three had a high form of ARM. The presacral masses consistent with Currarino triad included anterior meningocoele in three patients, lipoma in two patients and anterior lipomeningocoele in one patient. MRI diagnosed tethering of the spinal cord in four of six patients. The tethering of the spinal cord was due to a lipomeningocoele in one patient, an intradural lipoma in one patient and a lipoma of the filum in two patients. CONCLUSION: The association of Currarino triad with tethered spinal cord seems more common than generally reported in the literature. Preoperative MRI of the lumbosacral spine is essential to detect significant myelodysplasia in all patients with Currarino triad.

Adolescent↗
PubMed1997

Lemierre's syndrome in children: high-resolution CT and color Doppler sonography patterns.

Lemierre's syndrome is an anaerobic sepsis occurring after oropharyngeal infection in healthy teenagers and young adults. We report two cases of adolescent girls suffering from Lemierre's syndrome studied with cervical color Doppler ultrasonography (CDUS), cervicothoracic helical CT, and high-resolution CT (HRCT) scanning. In both patients, HRCT allowed a good depiction of multiple cavitated pulmonary nodules of various sizes suggestive of this entity and was able to detect small or peripheral nodules. CDUS helped to pinpoint the extent of thromboses of the internal jugular vein demonstrated by CT. CDUS and HRCT should be performed as early as possible to confirm and treat this life-threatening condition.

Adolescent↗
PubMed1996

[Radiologically guided percutaneous drainage: state of the art].

Percutaneous drainage of abscesses and other abnormal fluid collections is a recent development of interventional radiology. The indications and results of these treatments are presently well established, as is their place relative to the standard of care, surgical drainage. This paper reviews in particular the technical aspects of percutaneous fluid collection drainage and highlights the practical experience of the authors. The following points are discussed: patient selection and preparation, advantages and shortcomings of the different imaging techniques available for drainage guidance, an outline of the different puncture methods according to difficulty of collection access, choice of drain type, clinical and imaging follow-up of the drained collection, and finally specific precautions in some common clinical situations. The pitfalls and complications of these methods are also discussed.

Abscess↗
PubMed1996

Image quality and dose in spiral computed tomography.

Image quality and dose produced by a spiral CT with various pitch values were investigated on the basis of test-object images and measurements of CT dose indexes. No major difference in image quality or dose was observed when comparing sequential and spiral mode acquisition with a pitch of one. Increase in pitch value produces a loss of contrast which leads to a loss of detectability. Nevertheless, in realistic protocols the image quality in the transverse plane remains acceptable up to pitch values of 1.3-1.6.

Artifacts↗
PubMed1996

Abdominal actinomycosis associated with intrauterine device: CT features.

Abdominal actinomycosis is a severe and progressive peritoneal infection, due to an anerobic gram-positive bacterium, Actinomyces israelii. The presence of a long-standing intrauterine device (IUD) is a well-known risk factor in young women. We report two cases of pelviperitoneal actinomycosis appearing in two young women with acute low abdominal pain. Abdominal CT demonstrated multiple solid or encapsulated peritoneal masses with marked contrast enhancement and infiltration of the adjacent mesenteric fat. Laparoscopy confirmed the presence of intraperitoneal abscesses which contained Actinomyces israelii. High doses of amoxicillin and clavulanic acid (Augmentine) were given and following CT scan after 2 and 6 weeks showed a slow, but complete, resolution of the lesions. Although the radiologic presentation of actinomycosis is nonspecific, the diagnosis should be raised in the presence of pseudotumoral mesenteric infiltration, particularly in young women with an IUD. Abdominal CT is a useful method for diagnosis and for follow-up.

Actinomyces↗