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Biomedical subjects

T Sommer

Publications and source records attributed to T Sommer.

At least 55 records · Page 3Linked to original sources
PubMed2000

[CT angiography hemodynamically relevant to renal artery stenosis. Evaluation of AXIAL, MPR, MIP and SSD reconstruction procedures under standard investigation conditions].

PURPOSE: To evaluate the various reconstruction methods of helical-CT angiography for the assessment of hemodynamically relevant renal artery stenoses in comparison to i.a. DSA. METHODS: In 76 renal arteries the reconstruction modalities AXIAL, MRP, MIP and SSD of helical-CT angiography were compared with the results of i.a. DSA for the determination of the grade and location of the stenosis. RESULTS: The highest accuracy of stenosis grading was 76% with AXIAL reconstruction. In 8% of the cases grading of the stenosis was not evaluable by the AXIAL reconstruction. In these cases, a higher sensitivity in the detection of hemodynamically relevant stenoses (> grade II, > 50%) was achieved with the reconstruction mode MPR (96%) than with MIP (92%). In 51% of the cases the reconstruction mode SSD was not suitable for any diagnosis of renal artery stenosis because of overlying calcified plaques. CONCLUSIONS: The evidence of hemodynamically relevant stenosis in helical-CT angiography in comparison to i.a. DSA succeeds most reliable by using the reconstruction modality AXIAL in combination with MPR. The MIP reconstruction provides information about the anatomy of the renal arteries within one image.

Angiography↗
PubMed2000

[Penetrating atherosclerotic ulcer of the thoracic aorta descendens]

Penetrating atherosclerotic ulcer of the thoracic aorta descendens. HISTORY AND CLINICAL FINDINGS: A 75-year-old man with a history of generalised atherosclerosis was admitted to hospital for invasive assessment of progredient typical angina pectoris. Apart from diminished peripheral pulses, physical examination was normal. INVESTIGATIONS: Coronary angiography revealed a three vessel coronary artery disease. The chest X-ray showed elongation and dilatation of the distal aortic arch and the proximal descending aorta thoracalis. Computed tomography and magnetic resonance imaging of the thorax as well as magnetic resonance angiography of the thoracic aorta, demonstrated a penetrating atherosclerotic ulcer of the descending aorta thoracalis, with extensive intramural hematoma. TREATMENT AND COURSE: After percutaneous ballon-dilatation of the right coronary artery and the circumflex artery, the patient was asymptomatic. Considering all aspects of the patients condition, medical treatment of the penetrating atherosclerotic ulcer was decided for the patient. The findings of the thoracic computed tomography after 6 months were unchanged. CONCLUSION: The penetrating atherosclerotic ulcer of the thoracic aorta is a less known clinical entity. Our case report demonstrates that even extensive forms can be clinical asymptomatic and discovered by routine radiologic examinations.

Journal Article↗
PubMed2000

MR imaging and cardiac pacemakers: in-vitro evaluation and in-vivo studies in 51 patients at 0.5 T.

PURPOSE: To evaluate the safety and feasibility of magnetic resonance (MR) imaging at 0.5 T in patients with implanted cardiac pacemakers. MATERIALS AND METHODS: Twenty-one models of pacemakers and 44 pacemaker electrodes were exposed to in vitro MR imaging with continuous registration of pacemaker output and temperature at the lead tip. Prior to MR imaging examination, pacemakers were programmed to an asynchronous mode (A00, V00, or D00). Pacemakers were examined before and after MR imaging. Forty-four patients with implanted pacemakers underwent 51 MR imaging examinations under cardiologic surveillance, continuous electrocardiography, pulse oximetry, and capnographic monitoring. RESULTS: MR imaging was safely performed in all patients. None of the pacemakers displayed a pacing dysfunction at MR imaging. No changes occurred in the programmed parameters in any device tested in vivo or in vitro. Maximum increases in the temperature at the lead tips were 8.90 degrees C at a specific absorption rate (SAR) of 0.6 W/kg and 23.50 degrees C under a worst-case radio-frequency (RF) heating condition with an SAR of 1.3 W/kg. CONCLUSION: MR imaging at 0.5 T can be safely performed in patients with implanted pacemakers in carefully selected clinical circumstances when appropriate strategies (programming to an asynchronous mode, adequate monitoring techniques, limited RF exposure) are used.

Capnography↗
PubMed1999

[Lumbar intercostal hernia--a rare condition].

Lumbar hernia is a rare condition, and as such often overlooked. We present a case of strangulated lumbar hernia in a 73 year-old man, with symptoms of left flank pain and a lumbar protrusion during three weeks. Diagnosis was achieved by CT scan, and a primary repair was done using a transperitoneal approach. The patient recovered well and was discharged in good condition.

Aged↗
PubMed1999

[Pregnant women themselves can take specimens for identification of group B streptococci carriers].

Prenatal screening for group B streptococcus colonisation in pregnant women is controversial, though recommended in some countries. We aimed to compare the detection rate when pregnant women performed their own vaginal/anorectal swabs with the standard practice of physician obtained swabs. During six months, 89 pregnant women with high risk for premature labor collected their own vaginal/anorectal swab after instruction from a midwife. Afterwards a physician took a similar sample among 80 of the women. All together, 30 (34%) out of 89 women were carriers of group B streptococcus. Comparing the efficacy of the sampling procedures among 80 women who had taken both tests, we found that 25 of 26 positive cultures were identified by self-collected samples, while 17 out of 26 were identified by samples collected by the physicians. The difference in sensitivity (96% vs 65%) was statistically significant (p < 0.001) with a kappa value of 0.68. Self-collected vaginal/anorectal swabs for the identification of group B streptococcus carriers are at least as sensitive as the practice of physician performed swabs.

Bacteriological Techniques↗
PubMed1999

[MRI diagnosis in longitudinal stress fractures: differential diagnosis of Ewing sarcoma].

PURPOSE: To compare MR imaging features of stress fractures, simulating malignancies, and Ewing sarcomas. MATERIALS AND METHODS: MR imaging studies of 4 patients with longitudinal stress fractures of the tibia (n = 2) and the femur (n = 2) simulating malignancy were retrospectively compared with the MRI scans of 10 patients with histologically proven Ewing sarcoma (femur n = 5; tibia n = 3, fibula n = 1, humerus n = 1). The diagnosis of stress fractures was confirmed by follow-up examinations. An additional biopsy was performed in two patients. RESULTS: Despite negative x-ray examinations, MRI showed the fracture line in all patients with stress fractures. In these cases marrow edema was irregular and there was no well defined margin towards normal fatty marrow. In contrast Ewing sarcomas were sharply demarcated in 9/10 cases. Extraosseous enhancing soft tissue was found in Ewing sarcomas as well as in stress fractures. In stress fractures the enhancing mass was repair tissue. Areas of necrosis within the enhancing mass was seen in (8/10) Ewing sarcomas, only. In follow-up studies we observed a decrease of the marrow edema in patients with stress fractures. Occurrence of low signal areas in T1- and T2-weighted sequences within the initial enhanced extraosseous tissue corresponded to bony callus on x-rays films. CONCLUSIONS: Repair tissue in stress fractures can imitate malignancy. The irregularity of the marrow edema without well defined margins, the lack of necrosis in the small enhancing tissue and the proof of the fracture line in the MRI are criteria to differentiate stress fractures from Ewing sarcomas. Short-term follow up studies are helpful to underline the diagnosis.

Adolescent↗
PubMed1999

[MRI diagnosis of cardiac myxomas: sequence evaluation and differential diagnosis].

PURPOSE: To evaluate native and contrast enhanced T1-weighted spin (T1-SE), cine gradient echo (Cine-GE), and T2-weighted turbo spin (T2-TSE) sequences in the diagnosis and differential diagnosis of cardiac myxomas. METHODS: 15 patients with echocardiographically suspected cardiac atrial myxomas underwent 0.5 T-MR imaging of the heart with native T1-SE, contrast-enhanced T1-SE, Cine-GE, and T2-TSE sequences. MR images were evaluated for signal intensity (SI) and lesion's conspicuity. Results were confirmed histologically (14 x) or by follow-up (1 x). RESULTS: MRI revealed myxomas in 9 patients, sarcomas in three patients, and thrombi in three patients. Lesion conspicuity was better in Cine-GE and T2-TSE compared with native and contrast-enhanced T1-SE sequences. Myxomas were characterized by an intermediate SI similar to myocardium in T1-SE, high SI similar to water in T2-TSE, and low to moderately high enhancement (range 19-75%, mean 48%). CONCLUSION: Distinct SI characteristics together with anatomical-topographical features (attachment to the interatrial septum, no infiltration of myocardium and vessels) are diagnostic for cardiac myxomas. Cine-GE and T2-TSE sequences are the sequences of choice for detection of myxomas and other atrial masses. T2-TSE and contrast-enhanced T1-weighted sequences are most useful for mass characterisation and differentiation between myxomas, malignant tumors, and thrombi.

Diagnosis, Differential↗
PubMed1998

NIP domain prevents N-type inactivation in voltage-gated potassium channels.

Shaker-related voltage-gated K+ (Kv) channels are assembled from ion-conducting K(v)alpha subunits, which are integral membrane proteins, and auxiliary K(v)beta subunits. This leads to the formation of highly diverse heteromultimeric Kv channels that mediate outward currents with a wide range of time courses for inactivation. Two principal inactivation mechanisms have been recognized: C-type inactivation correlated with carboxy-terminal K(v)alpha-subunit structures, and N-type inactivation conferred by 'ball' domains in the amino termini of certain K(v)alpha and K(v)beta subunits. Assembly of heteromultimers with one or more K(v)alpha- and/or K(v)beta ball domains appears to be an essential principle of the generation of A-type Kv channel diversity. Here we show that, unexpectedly, the presence of K(v)alpha- or K(v)beta-ball domains does not dominate the gating phenotype in heteromultimers containing Kv1.6alpha subunits. These heteromultimers mediate non-inactivating currents because of the dominant-negative activity of a new type of N-type inactivation-prevention (NIP) domain present in the Kv1.6 amino terminus. Mutations in the NIP domain lead to loss of function, and its transfer to another K(v)alpha subunit leads to gain of function. Our discovery of the NIP domain, which neutralizes the activity of K(v)alpha- and K(v)beta-inactivation gates, establishes a new determinant for the gating behaviour of heteromultimeric Kv channels.

Amino Acid Sequence↗
PubMed1998

[Clinical and nuclear magnetic resonance tomography diagnosis of glenoid labrum injuries].

PURPOSE: Clinical and radiological evaluation of labral tears remains challenging. It has been shown that intravenous administration of contrast agents produces an MR arthrographic effect without the need for intraarticular injection. This is the first study evaluating this new technique of indirect MR arthrography in diagnosis of glenoid labrum tears. METHODS: 28 patients with clinically suspected labral injuries were prospectively investigated (1.5 Tesla, flexible surface coil). A native MR exam of the shoulder (transverse and oblique-coronar orientation, T1-weighted spin-, proton density- and T2*-weighted gradient echo sequences) and indirect MR arthrography (transverse and oblique-coronar orientation, fat-suppressed T1-weighted spin-echo sequences, intravenous injection of gadopentetate dimeglumine [0.1 mmol/kg], followed by 10-15 min of joint movement) were performed. Results were confirmed by arthroscopy and/or open surgery. Additionally sensitivity evaluation of clinical tests for investigation of labral tears were performed. RESULTS: Indirect MR-Arthrography improved delineation of the glenoid labrum and hyaline cartilage significantly (p < 0.05). Sensitivity and specificity of indirect MR arthrography in diagnosis of labral injuries were 90% and 89% respectively, compared to 79% and 67% of the native MR exam. The reliability of the checked clinical tests is not sufficient enough to determine labral lesions (predictive value between 50 and 70%). CONCLUSION: Indirect MR-arthrography is a promising non-invasive technique in the evaluation of the glenoid labrum.

Adult↗
PubMed1998

Indirect MR arthrography: techniques and applications.

Indirect MR arthrography is a relatively new MR technique improving articular and periarticular contrast. It is achieved by injection of paramagnetic MR contrast media intravenously instead of intra-articular injection as in direct MR arthrography. After the injection exercising the joint results in considerable signal intensity increase within the joint cavity. Fat saturated MR sequences then yield arthrographic images. The method is less invasive than direct MR arthrography and first results showed comparable sensitivities and specificities for rotator cuff and glenoid labrum pathology. In this article the technique, established and potential future indications, drawbacks and limitations of the method are reviewed.

Contrast Media↗
PubMed1998

[Löffler fibroblastic endocarditis in the thrombotic stages in isolated right ventricular tissue eosinophilia].

We report on a male, 31 year old, Turkish patient with an intracardiac mass in the right ventricle, reduction of performance and weight, as well as intermittent fever. No eosinophilia was documented in the peripheral blood; cardiac function was primarily normal. Besides the differential diagnosis of Löffer's endocarditis (endomyocardial fibrosis) an inflammatory disease and a malignant cardiac tumor were suggested. The diagnosis of Löffler's endocarditis could not be confirmed morphologically by echocardiography nor histologically by right ventricular biopsy. Operative removal of the mass lesion was necessary because of fast tumor progression, fulminant pulmonary embolism, and infiltration of the tricuspid valve. Only then, histologically Löffler's eosinophilic endocarditis of thrombotic stage was diagnosed. Antiphlogistic therapy with cortisone was initially performed. With a dose reduction after 6 months, a relapse of the thrombotic mass occurred. Therefore, continuous treatment with cortisone and azathioprine was induced followed by further tumor regression and further clinical stabilization since 8 months of treatment.

Adult↗
PubMed1998

Spinal epidural haematoma in haemophilia A.

We report on a 27-year-old male Caucasian with severe haemophilia A who presented with acute onset of neck pain with cervical nerve root irritation, due to a spinal epidural haematoma. His past medical history revealed carrying of a moderate weight as a possible traumatic mechanism. Under immediate factor VIII replacement therapy complete remission of the symptoms was achieved within several days. The diagnosis of spinal epidural haematoma and complete resorption was revealed by initial and follow-up magnetic resonance imaging studies of the cervical spine. Having reviewed the literature on spinal epidural haematoma, we present an overview of the treatment and outcome as regards haemophilia.

Adult↗
PubMed1998

[A rational study of the great abdominal veins using 2D-TOF- and turbo-spin-echo sequences].

PURPOSE: Development of a fast and reliable protocol for the detection and exclusion of abdominal venous thrombosis with an optimised T2-TSE- and 2D-TOF sequence. MATERIAL AND METHOD: Evaluation of the flow-void phenomenon with a flow phantom on a 1.5 and 0.5 Tesla system using different echo times. Examination of 22 patients with suspected abdominal shunt- or abdominal vein-thrombosis with a optimum T2-TSE- and 2D-TOF sequence with a 1.5 or 0.5 Tesla system. Confirmation of thrombosis with contrast-enhanced computed tomography or digital subtraction angiography. RESULTS: The most effective combination of strong flow-void phenomena, signal/noise ratio and scan time was found with the following parameters: TE 120 ms, TR 2000 ms, 5 mm slice gap. In the patient group two complete and two partial thromboses were diagnosed with both sequences. One wrong positive thrombosis occurred in a stenotic anastomosis with the 2D-inflow sequence. CONCLUSION: With optimum parameters the T2-TSE sequence produces a strong "flow-void" phenomenon suitable for "black-blood"-MRA. The use of this sequence alone or in combination with 2D-inflow MRA, if "bright-blood" MRA is recommended, allows a reliable evaluation of thrombosis in abdominal veins without high-tech MRA equipment and contrast media.

Abdomen↗