Biomedical subjects

M Thelen

Publications and source records attributed to M Thelen.

At least 181 records · Page 10Linked to original sources

PubMed1997

Subcutaneous implantation metastasis of a cholangiocarcinoma of the bile duct after percutaneous transhepatic biliary drainage (PTBD).

Percutaneous transhepatic biliary drainage (PTBD) is the basis for most biliary interventional procedures. We recently observed the occurrence of a subcutaneous implantation metastasis after PTBD in a patient with incurable cholangiocarcinoma. Although tumor cell seeding along the catheter tract is a very rare complication, we think that PTBD should be avoided when curative resection is planned.

Aged↗

PubMed1997

Pneumomediastinum and pneumopericardium due to malignant subcarinal lymphadenopathy: CT demonstration.

A 52-year-old man had been treated for oral cancer T3 N0 M0 by radical surgery, neck dissection on the right and cervical irradiation (60 Gy). Two months after therapy he presented with dysphagia and hemoptysis. Admission chest X-ray revealed a pneumopericardium. It was caused by a bronchomediastinal fistula due to necrotic metastatic lymph nodes as shown by CT, which also revealed a concomitant pneumomediastinum. The patient died 10 days later from pneumonia. The CT findings were confirmed at autopsy. We conclude that malignant mediastinal lymphadenopathy is a potential cause of pneumopericardium and pneumomediastinum.

Bronchial Fistula↗

PubMed1997

Automatic detection of ground glass opacities on lung HRCT using multiple neural networks.

The purpose of this study was to implement neural networks and expert rules for the automatic detection of ground glass opacities (GG) on high-resolution computed tomography (HRCT). Different approaches using self-organizing neural nets as well as classifications of lung HRCT with and without the use of explicit textural parameters have been applied in preliminary studies. In the present study a hybrid network of three single nets and an expert rule was applied for the detection of GG on 120 HRCT scans from 20 patients suffering from different lung diseases. Single nets alone were not capable to reliably detect or exclude GG since the false-positive rate was greater than 100 % with regard to the area truly involved, more than 50 pixels throughout, and the true-positive rate was greater than 95 %. The hybrid network correctly classified 91 of 120 scans. Mild GG was false positive in 15 cases with less than 50 pixels, which was judged not clinically relevant. The pitfalls were: partial volume effects of bronchovascular bundles and the chest wall. Motion artefacts and diaphragm were responsible for 11 misclassifications. Hybrid networks represent a promising tool for an automatic pathology-detecting system. They are ready to use as a diagnostic assistant for detection, quantification and follow-up of ground glass opacities, and further applications are underway.

Expert Systems↗

PubMed1997

[The helium-3 MRT of pulmonary ventilation: the initial clinical applications].

PURPOSE: of the study is the visualisation of normal pulmonary ventilation in healthy volunteers and the evaluation of abnormalities in patients with different lung diseases using 3He magnetic resonance imaging (3He-MRI). MATERIAL AND METHODS: Hyperpolarized 3He gas (V = 300 ml, p = 3 x 10(5) Pa, polarised to 35-45% by optical pumping, provided in special glass cells) was inhaled by eight healthy volunteers and ten patients with different lung diseases. A 3D FLASH sequence (TR = 11.8 ms; TE = 5 ms; matrix 144 x 256, FOV 350 mm, section thickness 7-10 mm, coronal orientation) was performed in a single breath-hold (22-42 s). Clinical and radiological examinations were available for correlation. RESULTS: The studies were successfully carried out in 8/8 volunteers and in 8/10 patients. The central airways were constantly visualised with intermediate to high signal intensity. The lung parenchyma of volunteers with normal ventilatory function showed rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease and/or pneumonia presented severe signal inhomogeneities. Space-occupying lesions and pleural effusion caused large areas with little or no signal. The represented the lesion and adjacent ventilatory disturbances whose extent had not been presumed from chest x-ray or CT. The spatial resolution was higher than in ventilation scintigraphy. CONCLUSION: 3He MRI is a promising new modality for the assessment of pulmonary ventilation and its anomalies.

Administration, Inhalation↗

PubMed1997

[Dynamic 31phosphorus magnetic resonance spectroscopy of the quadriceps muscle: metabolic changes under 2 different forms of loading].

PURPOSE: The aim of the present investigation was to examine the metabolism of the quadriceps muscles of normal young individuals using dynamic 31phosphorus magnetic resonance spectroscopy. METHODS: 22 normal individuals were examined in a 1.5T-MRT using a 6 cm surface coil. The metabolic changes in the quadriceps muscle as shown by the phosphorus spectrum were evaluated during rest, exercise (isometric and isotonic exercise) and during a 36-second period of recovery. RESULTS: The Pi/PCr quotient rose from its resting value of 0.11 +/- 0.02 following exercise to a maximum of 0.83 +/- 0.47 (isometric) or 1.40 +/- 0.59 (isotonic) (difference p = 0.0001). Half-time recovery of Pi/PCr was 35 +/- 11 s or 31 +/- 10 s, respectively (p = 0.13). During the recovery phase Pi/PCr fell briefly but significantly below its rest value. Following an initial rise in pH, there was a continual fall. Minimum pH (6.68 +/- 0.21 and 6.53 +/- 0.27 respectively; p = 0.01) occurred in the early recovery phase. The recovery process of pH values lasted longer following isotonic than after isometric exercise (half-value recovery time 229 +/- 72 s and 146 +/- 55 s, respectively; p = 0.001). CONCLUSION: Compared with isometric exercise, isotonic stress is more expensive in terms of metabolism. Dynamic 31phosphorus MRT spectroscopy can differentiate changes in muscle metabolism during different forms of exercise.

Adult↗

PubMed1997

[Whole body spiral CT in primary diagnosis of patients with multiple trauma in emergency situations].

PURPOSE: The aim of this study was to evaluate the role of a fast whole body helical CT scanner for primary diagnosis in trauma patients. METHODS: 27 severely injured patients (9 women, 18 men; mean age 43 years) were first examined with a helical CT scanner allowing for digital radiograms up to a length of 1024 mm and continuous helical scans of up to 70 seconds (slice thickness 3 to 10 mm, pitch factor up to 2). The primary CT diagnosis was verified either by x-ray after the CT examination or during the subsequent days, by abdominal ultrasound, by additional CT scans in the following days, and by clinical follow-up. RESULTS: CT showed all clinically relevant injuries of the head, spine, chest, abdomen and pelvis. The diagnosis and classification of vertebral fractures was performed immediately. 4% of the fractures of the extremities and the ribs were not seen primarily. 6% of the injuries were outside the CT scan field. CONCLUSION: Helical CT is a reliable and fast method to obtain vital information and to improve management planning in severely injured patients. It reduces the number of conventional x-ray examinations. In certain cases, additional x-rays of extremity fractures may be required.

Abdominal Injuries↗

PubMed1997

[Follow-up of Crohn's disease: can hydro-MRI replace fractionated gastrointestinal passage examination?].

PURPOSE: To compare the value of hydro-MRI with follow-through examinations in the follow-up of Crohn's disease. METHOD: 22 patients known to be suffering from Crohn's disease were examined via 1.5 T-MR system; an oral contrast examination using 1000 ml of a 2.5% mannitol solution was performed in all patients. T2-weighted TSE sequences and T1-weighted SE sequences were performed before and after the intravenous injection of Gd-DTPA. To reduce movement artifacts caused by peristalsis of the gut, intravenous injection of 40 mg Buscopan was given. The findings of hydro-MRI were compared with the follow-through examinations. RESULTS: In the upper gastrointestinal tract, the follow-through examination showed clear advantages compared with hydro-MRI for the demonstration of inflammatory changes in the gut; Hydro-MRI was, however, somewhat more reliable in the ileum and colon. It was also more sensitive than the follow-through for the demonstration of enteric fistulae (four as compared with two cases), and in demonstration extraluminal changes (free fluid in six against zero, and inflammatory adherent loops (four against zero)). Amongst the 22 patients, hydro-MRI was equal (in 10) or better (in 8) than the follow-through examination for demonstrating the intestinal manifestations of Crohn's disease, and follow-through was better in only four. CONCLUSION: For follow-up of Crohn's disease, hydro-MRI is at least as good as follow-through examination, and is even preferable, because of the absence of radiation exposure of the usually young patients.

Administration, Oral↗

PubMed1997

[The algorithm of imaging diagnostics of pulmonary embolism: is it time for a new definition?].

Acute pulmonary embolism (PE) is an increasing and underdiagnosed cause of mortality and morbidity in hospitalised patients: pulmonary hypertension based on chronic pulmonary embolism is an uncommon, but severe and surgically curable complication. Since clinical signs might be silent or unspecific, both acute and chronic PE require imaging methods for diagnosis and treatment planning. Chest radiographic findings are usually non-specific. Scintigraphy provides a high sensitivity for PE, but lacks anatomic resolution and sufficient specificity. Pulmonary angiography, albeit accurate, is an invasive procedure associated with low but still not negligible morbidity and mortality. Hence, non-invasive methods offer advantages. Spiral CT, for example, is most reliable in the diagnosis of acute and chronic PE: Such fast CT techniques provide a non-invasive means to detect and differentiate acute emboli and organised thrombi, as well as perfusion abnormalities and other concomitant findings. MRI offers both morphological and functional information on lung perfusion and right heart function, but its image quality still needs improvement to be comparable with CT. Thus, while MRI must still be tested in clinical studies. CT is recommended as a screening method in acute and chronic pulmonary embolism.

Algorithms↗

PubMed1997

[Clinical relevance of CT of paranasal sinuses prior to bone marrow transplantation].

PURPOSE: To investigate the clinical necessity of CT of the paranasal sinuses before bone marrow or peripheral blood stem cell transplantation. PATIENTS AND METHODS: 80 patients with malignant disease underwent coronal CT of the paranasal sinuses prior to transplantation to exclude sinusitis. RESULTS: CT revealed sinusitis requesting therapy in 17/80 patients (21%). Patients with leukaemia and non-Hodgkin lymphoma were significantly more affected. Chronic sinusitis was found in two patients, mucosal swelling not requesting therapy in 22, and normal findings in 39. CONCLUSION: CT of the paranasal sinuses is advised in patients suffering haemoblastoses with an increased risk of infectious complications during the transplantation phase, because pathological findings can be expected in 21% of the patients. Diagnosis and therapy of an infectious focus within the paranasal sinuses is especially important prior to allogenous bone marrow transplantation.

Adolescent↗

PubMed1997

[Spiral CT for the detection of coronary artery calcifications and the prognosis of coronary heart disease--a comparison with fluoroscopy and coronary angiography].

PURPOSE: Evaluation of clinical relevance of coronary calcifications detected by helical CT. Evaluation of congruence with fluoroscopy (FS) and coronary angiography. Comparison with studies reporting on application of ultrafast computed tomography. MATERIALS AND METHODS: 40 patients underwent helical CT (2 mm slice thickness, table-feed 3 mm/s). Coronary angiography and FS were performed in usual technique. Stenosis and calcifications were evaluated semiquantitatively. RESULTS: 28 of 28 stenoses > or = 75% were detected via helical CT by evaluation of calcification (FS: 19). One non-detected solitary stenosis was calculated as 40%. FS did not detect 4 cases with 2-vessel and 3-vessel disease each one case with 1-vessel disease, and one case with a main stem stenosis. Sensitivity of helical CT was 97% (FS: 66%). For the evaluation of stenosis III degree (> or = 75%), sensitivity was 100% (FS: 58%), specificity was 77% (FS: 48%). CONCLUSION: Helical CT is more sensitive for haemodynamically relevant stenoses than FS. Helical CT is suitable as a substantial non-invasive diagnostic procedure in coronary heart disease. In certain cases, e.g. if the patient suffers from additional risks, helical CT should be done prior to coronary angiography. Coronary calcifications found incidentally in symptomatic patients at chest CT warrant further cardiological investigation.

Adult↗

PubMed1997

[Dynamic 31-phosphorus magnetic resonance spectroscopy of the m. quadriceps: therapy-induced changes in arterial occlusive disease].

PURPOSE: The present investigation aimed at examining changes in muscle metabolism caused by treatment of arterial occlusive disease, using dynamic 31-phosphorus methods. METHOD: 32 patients with arterial occlusive disease were examined in a 1.5 T apparatus with a 6 cm surface coil before and after treatment. The metabolic changes in the quadriceps muscles were visualised during a 36 s phosphorus spectrum during rest, exercise (isometric and isotonic) and during a period of recovery. RESULTS: Vascular therapy resulted in a significant increase in the duration of both types of exercise during dynamic phosphorus spectroscopy (isometric exercise: 282 s against 199 s: p = 0.002, isotonic exercise: 575 s against 222 s; p = 5 x 10(-6). After treatment, exercise-induced changes in pH (7.00 against 6.94; p = 0.004 and 7.00 against 6.93; p = 0.02) and the ratio Pi/PCr (0.34 against 0.44; p = 0.002 and 0.36 against 0.50; p = 0.009) were significantly smaller than before therapy, using a similar amount of exercise. Recovery time of Pi/PCr (45 s against 82 s; P = 10(-5) and 42 s against 57 s; p = 0.01) and pH value (154 s against 181 s; p = 0.14 and 173 s against 214 s; p = 0.22) showed significant reduction after treatment. CONCLUSIONS: Dynamic 31-phosphorus magnetic resonance spectroscopy indicates increased mitochondrial oxidative capacity in the quadriceps muscles as evidence for increased oxygen supply to muscle tissue following vascular therapy.

Arterial Occlusive Diseases↗

PubMed1997

[CT angiography in arterial occlusive disease: comparison of 3 rendering techniques].

PURPOSE: To evaluate different rendering techniques of CT data for the assessment of long vessel segments in peripheral vascular occlusive disease. MATERIAL AND METHODS: 40 CT angiograms (aortoiliac: n = 20, leg arteries: n = 20) were viewed using three different rendering techniques: 1, maximum intensity projection (MIP); 2, volume rendering (VR); 3, shaded surface display (SSD). CT angiograms were obtained in 6 or 8 projections. Axial cross-section images were analysed using an interactive cine mode. Intraarterial DSA was the standard in all cases. RESULTS: The sensitivities for the diagnosis of occlusive disease were 100% (cross-section images), 94% (MIP), 91% (VR) and 93% (SSD). The specificities were 100%, 99%, 99% and 99%, respectively. For the accurate grading of high-grade (> 75%) stenoses, the sensitivities were 85% (cross-section images), 62% (MIP), 44% (VR) and 35% (SSD). Specificity was 99% for all techniques. CONCLUSIONS: CTA is accurate in occlusive disease. Interactive viewing of cross-section images is the most accurate technique. MIP is superior to VR in the imaging of high-grade stenoses because contrast-to-noise ratio is high and thresholding is not necessary.

Angiography, Digital Subtraction↗

PubMed1997

Dynamic phosphorus-31 magnetic resonance spectroscopy in arterial occlusive disease. Correlation with clinical and angiographic findings and comparison with healthy volunteers.

RATIONALE AND OBJECTIVES: The aim of this prospective study was to explore muscular metabolism in arterial occlusive disease (AOD) by dynamic phosphorus-31 (31P) magnetic resonance spectroscopy (MRS). METHODS: The authors examined 56 patients with AOD. Acquisition of up to 60 consecutive phosphorus spectra of the quadriceps muscle was done by "time series" in 36 seconds each. In this way, the authors achieved uninterrupted monitoring of muscle metabolism during rest, exhaustion, and recovery. During 31P MRS, the volunteers performed an isometric and an isotonic exercise until exhaustion of the quadriceps muscle. Spectroscopic results of 56 patients with AOD were correlated with clinical and angiographic findings and were compared with spectroscopic results of 10 age-matched healthy volunteers. RESULTS: There were no significantly differing spectroscopic results between patients and volunteers at rest, except for an elevated ratio phosphomonoester (PME)/beta-adenosine triphosphate (ATP) in patients with AOD (0.66 +/- 0.19 versus 0.48 +/- 0.09). Despite a sixfold duration of both of the exercises until exhaustion in healthy volunteers, exercise-induced changes of inorganic phosphate (P1)/phosphocreatine (PCr), PME/beta-ATP, and pH were similar in healthy volunteers and patients with AOD. Compared with maximal exercise-induced values of Pi/PCr, acidosis was relatively increased in AOD, resulting in a steeper slope of linear regression line (-0.33 +/- 0.06 versus -0.14 +/- 0.06) between these parameters. Recovery rate of Pi/PCr was markedly prolonged in AOD (time of half recovery: 80 seconds versus 25 seconds [isometric exercise] and 70 seconds versus 37 seconds [isotonic exercise]), whereas recovery rate of pH was not significantly slowed down in our patients (192 seconds versus 166 seconds [isometric exercise] and 234 seconds versus 220 seconds [isotonic exercise]). CONCLUSIONS: Dynamic 31P MRS provides a direct judgment of muscular metabolism, which is not only influenced by macro-, but also by microangiopathia. Results of 31P MRS suggest a reduced mitochondrial oxidative phosphorylation in AOD.

Acidosis↗

PubMed1997

Spiral CT of pulmonary hypertension and chronic thromboembolism.

Pulmonary hypertension caused by chronic pulmonary embolism (PE) represents an uncommon, but severe and surgically curable complication of recurrent acute embolism. Because clinical signs might be silent or nonspecific, chronic PE requires imaging methods for diagnosis and treatment planning. Chest radiographic findings are usually nonspecific. Scintigraphy provides a high sensitivity for PE, but lacks anatomic resolution and sufficient specificity. Pulmonary angiography, albeit accurate, is an invasive procedure associated with low but still considerable morbidity and mortality. Thus, noninvasive methods are required. Most reliably in the diagnosis of acute and chronic PE, fast computed tomography (CT) techniques like spiral CT provide noninvasive means to detect and differentiate organized mural thrombi, as well as perfusion abnormalities and concomitant findings. Magnetic resonance imaging offers morphologic as well as functional information on lung perfusion and right heart function, but image quality needs improvement to be comparable with spiral CT. Thus, although spiral CT is recommended as the screening method for acute and chronic PE, magnetic resonance imaging might be the method of the future.

Chronic Disease↗

PubMed1997

CT angiography versus intraarterial digital subtraction angiography for assessment of aortoiliac occlusive disease.

OBJECTIVE: The purpose of this study was to evaluate the accuracy of CT angiography (CTA) with a single helical acquisition for assessment of stenoses and occlusions of the iliac arteries. SUBJECTS AND METHODS: In our prospective study, intraarterial digital subtraction angiography and IV CTA were performed from the suprarenal aorta to below the femoral bifurcation in 30 patients with vascular occlusive disease. Maximum-intensity-projection images in multiple views were also obtained. The accuracy of CTA with and without analysis of axial images was determined. RESULTS: Sensitivity and specificity of CTA were 100% for iliac artery occlusions with a confidence interval 85-100% and 97-100%, respectively. When axial scans were interpreted, 14 of 15 high-grade (> 75%) stenoses were recognized. Sensitivity and specificity of CTA were 93% (range, 68-100%) and 99% (range, 97-100%), respectively. When maximum intensity projections alone were analyzed, sensitivity for the diagnosis of 15 high-grade stenoses was only 53% (range, 27-79%) because calcified plaques obscured six stenoses. CONCLUSIONS: CTA accurately reveals iliac artery occlusions. Observers of CT angiograms may overlook short stenoses in rare instances. Calcified plaques limit the use of maximum-intensity-projection images.

Angiography↗

PubMed1997

Early detection of pneumonia in febrile neutropenic patients: use of thin-section CT.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of thin-section CT for early detection of pneumonia in neutropenic patients with an unknown site of infection and normal or nonspecific findings on chest radiographs. SUBJECTS AND METHODS: Eighty-seven patients with febrile neutropenia that persisted for more than 2 days despite empiric antibiotic treatment underwent 146 prospective examinations. If findings on chest radiographs were normal (n = 126) or nonspecific (n = 20), thin-section CT (1-mm collimation, 10-mm increment) was done. If thin-section CT scans showed opacities, bronchoalveolar lavage was recommended. RESULTS: Findings on chest radiographs were nonspecific for pneumonia in 20 (14%) of 146 cases, and CT findings in those cases were suggestive of pneumonia. Microorganisms were detected in 11 of those 20 cases. Seven of the 11 cases were not optimally treated before CT diagnosis, the other four were sufficiently treated. Findings on chest radiographs and thin-section CT scans were normal in 56 (38%) of 146 cases. In 70 (48%) of 146 cases, findings on chest radiographs were normal, whereas findings on thin-section CT scans were suggestive of pneumonia. Microorganisms were detected in 30 of the 70 cases. Nineteen of 30 cases were not optimally treated before CT, whereas the other 11 cases were sufficiently treated before CT. In 22 (31%) of these 70 cases, an opacity was observed on the chest radiograph during the 7 days after the CT study. Only three (5%) of 56 pneumonias occurred during the first 7 days after thin-section CT studies with normal findings (p < .005). Additional risk factors for pneumonia occurring later that were detectable on chest radiographs were poorly defined nodules (p < .05), consolidation (p < .05), and younger age (p < .05). CONCLUSION: Thin-section CT scans show findings suggestive of pneumonia about 5 days earlier than chest radiographs show suggestive findings. When thin-section CT scans show findings suggestive of pneumonia, the probability of pneumonia being detected on chest radiographs during the 7-day follow-up is 31%, whereas the probability is only 5% when the findings on the prior thin-section CT scan were normal (p < .005). All neutropenic patients with fever of unknown origin and normal findings on chest radiographs should be examined with thin-section CT.

Antineoplastic Agents↗

PubMed1997

[Recurrence of a stage IV neuroblastoma].

In the follow-up of metastatic neuroblastoma mIBG scintigraphy represents the very diagnostic method. A case report of a child with a metastatic recurrence of neuroblastoma is given. Despite clear scintigraphic visualisation serum parameters remained negative. The role of additional bone scintigraphy is inconclusive even retrospectively.

3-Iodobenzylguanidine↗

PubMed1996

Hemodynamic effects of nonionic contrast bolus injection and oxygen inhalation during pulmonary angiography in patients with chronic major-vessel thromboembolic pulmonary hypertension.

BACKGROUND: Pulmonary angiography is the gold standard for the diagnosis of chronic thromboembolic pulmonary hypertension; however, major complications have been reported. This study evaluates the hemodynamic effects of direct pulmonary nonionic contrast bolus injection and oxygen inhalation in patients with chronic thromboembolic pulmonary hypertension. METHODS AND RESULTS: In 33 patients, hemodynamic parameters were measured after oxygen inhalation and during bolus injection of nonionic contrast medium in a control group (group 1. n = 11), in a group of patients with moderately severe pulmonary hypertension (group 2, n = 9), and in a group with severe pulmonary hypertension (group 3, n = 13). Oxygen inhalation significantly improved oxygen supply. Pulmonary artery pressure and heart rate were reduced, but pulmonary vascular resistance and total pulmonary resistance were not significantly affected. One hundred ninety-eight angiograms were performed selectively on both pulmonary arteries in the posterior-anterior, oblique, and lateral views. Before contrast bolus injection, RAP and PAP significantly increased because of initial inspiration. Contrast bolus injection caused only a minor pressure increase (delta PA systolic, 2.3 +/- 1.4, 2.5 +/- 1.8, and 5.0 +/- 5.2 mm Hg, groups 1, 2, and 3, respectively) without significance between the groups. After the angiography, pulmonary artery pressure was moderately increased, predominantly in group 3, but pulmonary vascular resistance was not significantly changed. Systemic vascular resistance was decreased. Cardiac index increased in groups 1 and 2 but was unchanged in group 3. Systemic pressure therefore decreased in group 3. CONCLUSIONS: We concluded that bolus injection of nonionic contrast medium causes no major hemodynamic effects even in patients with severe chronic thromboembolic pulmonary hypertension. Oxygen contributes to safety during the procedure.

Administration, Inhalation↗