Biomedical subjects

K Schunk

Publications and source records attributed to K Schunk.

At least 37 records · Page 2Linked to original sources

PubMed1998

[Measurement of migration of acetabular components in cementless hip replacement].

PURPOSE: Migration measurements of acetabular components using a special computer aided method (EBRA = abbreviation for the German term "Ein-Bild-Röntgenanalyse") were performed to evaluate early results of the implants and predict aseptic loosening. METHODS: Standard ap-radiographs of the pelvis were marked, specific points were digitised. Simulating the spatial situation the programme computes longitudinal and vertical migration of the cup. 74 acetabular components in 71 patients could be studied by migration measurements. RESULTS: 14 patients showed migration of more than 1 mm, which is the confidence limit of this method. Each of these patients showed diverse reasons for the migration, i.e. osteoporosis of the acetabular bone stock or problems concerning the surgical technique which means malposition of the cup or insufficient reaming of the bone. There were some patients with severe congenital dysplasia of the hip and in some cases the inclination angle of the cup was too great. CONCLUSION: The technique applied for measuring migration of acetabular components can be useful for evaluating early instability of the implant and can be helpful in detecting problems concerning the surgical technique.

Acetabulum↗

PubMed1998

Dynamic phosphorus-31 magnetic resonance spectroscopy in arterial occlusive disease: effects of vascular therapy on spectroscopic results.

RATIONALE AND OBJECTIVES: The aim of the authors' prospective study was to explore therapy-induced changes of muscular metabolism in arterial occlusive disease (AOD). MATERIALS: Before and after vascular therapy, respectively, 31 patients with AOD were examined by dynamic phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) at 1.5 T; in the magnet, the quadriceps muscle was stressed by an isometric and an isotonic form of exercise until exhaustion, respectively. Twenty-three patients were treated by standardized percutaneous transluminal angioplasty; eight patients underwent a vascular operation. RESULTS: Vascular therapy induced a marked improvement of clinical and angiographic results. At the same work load, exercise-induced metabolic changes of the quadriceps muscle were significantly less pronounced after the vascular therapy: maxima of the ratio inorganic phosphate (Pi)/phosphocreatine (PCr) (isometric exercise: 0.34 [after therapy] versus 0.44 [before therapy]; isotonic exercise: 0.36 [after therapy] versus 0.51 [before therapy]) as well as minima of pH (isometric exercise: 7.00 [after therapy] versus 6.93 [before therapy]; isotonic exercise: 7.00 [after therapy] versus 6.93 [before therapy]). In relation to maximal values of Pi/PCr, the extent of acidosis was smaller after vascular therapy, resulting in a flatter slope of the regression line between these parameters (b = -0.24 +/- 0.10 versus b = -0.31 +/- 0.09). After both of the exercises, time of half recovery of Pi/PCr was significantly shorter after vascular therapy (isometric exercise: 43 seconds [after therapy] versus 83 seconds [before therapy]; isotonic exercise: 42 seconds [after therapy] versus 57 seconds [before therapy]). CONCLUSIONS: After effective vascular therapy, minor exercise-induced metabolic changes (increased "work/energy cost-index"), a decreased contribution of anaerobic glycolysis to total adenosine triphosphate production as well as a markedly increased recovery rate of Pi/PCr are unequivocal spectroscopic proofs of an improved oxidative metabolism of muscle cells because of increased tissue perfusion.

Adenosine Triphosphate↗

PubMed1998

[Diagnostic imaging of benign and malignant liver tumors: computerized tomography or magnetic resonance tomography?].

A reliable preoperative detection and characterization of all liver lesions is necessary for the clarification of the operability of a patient. In patients, who are considered as good candidates for a partial liver resection, a double spiral-CT with an oral bowel opacification and an intravenous contrast medium administration is recommended. In those patients, who continue to be candidates for partial liver resection after CT, a CT arterioportography with arterial and portalvenous liver enhancement should be performed as the present gold standard of preoperative liver diagnostics. The aim of CT arterioportography is the further selection of patients for liver surgery. Because of its high specificity, MRI is useful for the characterization of liver lesions of unknown histology. For the differentiation between malignant (metastases) and benign (hemangioma) liver lesions, MRI is the method of choice. Because of the expected technical developments of MRI, a short-term comparison of CT and MRI in prospective studies is necessary.

Hepatectomy↗

PubMed1998

[MRI in typical and atypical aortic dissection].

PURPOSE: To determine the value of MRI in typical and atypical aortic dissections. METHODS: MRI investigations on 16 patients with aortic dissections were analysed retrospectively; for 8 patients CT investigations carried out at almost the same time were available for comparison. RESULTS: In all cases the diagnosis of aortic dissection was possible from MRI and CT. If a dissection membrane and a double lumen were present these were detected in all patients by both methods. In three patients with atypical dissections, only an asymmetrical abnormal wall thickening as sole sign for the presence of an aortic dissection was seen. A differentiation between true and false lumen was possible in 16 of 17 MRI investigations and in 5 of 8 CT investigations on the basis of differing blood flow velocities or, respectively, the detection of a thrombus in the false lumen. The relationship of the dissection membrane to the large aortic branches as well as the determination of the branch vessel origin with regard to true or false lumen could be evaluated better with MRI than with CT. CONCLUSIONS: Thus MRI has a significant role in the diagnosis and follow-up of aortic dissections. The advantage in comparison to the alternative spiral CT technique is, in addition to the absence of radiation exposure, the better analysis of the extent of the dissection as a result of the multi-planar slice orientation (especially in the region of the aortic arch and the arch vessel origins) without the necessity to administer iodine-containing contrast media.

Adult↗

PubMed1997

Diagnosis of pulmonary metastases with turbo-SE MR imaging.

The sensitivity of MR imaging for detection of pulmonary metastases was evaluated in 23 patients. The MR imaging was performed with T2-weighted turbo-spin-echo (TSE) sequences at 1.5 T. The MR images were compared with spiral volumetric CT which served as the radiological standard. All MR images were interpreted by two radiologists without knowledge of CT findings. The MR imaging technique initially enabled correct identification of altogether 286 of 340 metastases (84 %) resulting in sensitivities of 36 % (size of nodules < 5 mm), 83 % (size of nodules 5-10 mm), 92 % (size of nodules 10-15 mm), and 100 % (size of nodules > 15 mm). Retrospectively with knowledge of CT findings an additional 39 metastases were visible; 15 remained undetected even retrospectively. The results of this paper suggest that MRI still does not have a role for screening for pulmonary metastases. It proves, however, that the incidental diagnosis of a pulmonary lesion on T2-weighted TSE images is highly reliable in representing a pulmonary nodule also visible on CT. However, thus far the malignant nature especially of small nodules detected by MRI (as by CT) remains uncertain even in patients with known malignant neoplasm.

Artifacts↗

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

[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

[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

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↗

PubMed1995

[The measurement of vascular diameter to determine stent and balloon size in percutaneous procedures in the pelvic circulation].

AIM: Should the sizes of balloons and stents used in the pelvic circulation be determined by the size of the ipsilateral or contralateral vessel? STUDY DESIGN: The angiographic findings in 31 patients were analysed; in 10 an occlusion and in 21 a high grade stenosis (greater than 75%) of the common iliac artery had been treated by stenting (26) or simple PTA (5). RESULTS: In 26 of the 31 patients there was marked reduction in the lumen distal to the lesion up to 40%. In 17 patients this was reversed immediately after the procedure and in five others the lumen increased but a difference between the two sides remained. The changes on the two sides following treatment were statistically significant (external iliac artery: p = 0.00013). CONCLUSION: The results indicate that the "normal" contralateral measurements should be used rather than the distal ipsilateral vessel diameter.

Adult↗

PubMed1995

[A mannitol solution as an oral contrast medium in pelvic MRT].

PURPOSE: Improvement of pelvic MRI using peroral administration of an aqueous mannitol solution. METHODS: We retrospectively evaluated magnetic resonance examinations of 72 patients with suspected or proven pelvic abnormalities: In 36 patients, no bowel marking was carried out. In further 36 patients, we performed a contrast enhancement of the bowel by oral application of 1000 ml of an aqueous mannitol solution. RESULTS: 8/36 (22%) patients suffered from diarrhoea, nausea or meteorism as a result of mannitol application. In group 2, an excellent bowel marking of the small intestine could be obtained in 36/36 (100%) patients. Contrast enhancement of the bowel significantly improved delineation between intestinal structures and pelvic organs or pathologic lesions, respectively. In summary, bowel marking was desirable in 25/36 (69%) of group 1 and helpful in 26/36 (72%) of group 2. CONCLUSION: Aqueous mannitol solution is a safe bowel contrast agent and improves the diagnostic value of pelvic MRI, but in some cases delineation between marked bowel and cystic pelvic lesions may be uncertain.

Administration, Oral↗

PubMed1995

[MRI studies on the distensibility of cruciate ligaments of healthy knee joint].

AIM: Examination of the distensibility of the cruciate ligaments to evaluate the tense plasty of the cruciate ligaments. MATERIAL AND METHOD: A functional MR study was performed using a Magnetom Open (0.2 Tesla, Fa. Siemens). We measured the length and width of the anterior and posterior cruciate ligament in volunteers (n = 12), age 20-40. We examined in 4 knee positions between maximal extension and maximal flexion. RESULTS: Using the Wilcoxon test, the statistics do not show any significant difference between the length and width of the cruciate ligaments in the monoxial movement. CONCLUSION: Our results may support the operative tense plasty of the cruciate ligaments although the entire complex mechanical system has not been examined.

Adult↗

PubMed1995

[Bronchiectasis and infection incidence in alpha 1-antitrypsin deficiency. The value of high-resolution computed tomography].

UNLABELLED: PURPOSE of this study was to determine the prevalence of bronchiectasis in patients suffering from alpha-1-antitrypsin deficiency and to compare its extent with the frequency of infections. MATERIAL AND METHODS: High-resolution CT examinations (HRCT) of 23 patients with alpha-1-antitrypsin deficiency were retrospectively assessed for extent, severity and localisation of bronchiectasis, bronchial wall thickening and extent of emphysema. Chest radiographs and clinical records were available for correlation. RESULTS: HRCT scans showed bronchiectasis in 14 of 23 patients, bronchial wall thickening in 3/14, and panlobular emphysema in 23/23. Chest radiographs showed bronchiectasis in 4/23 patients. Only two of 9 patients without bronchiectasis had a history of infections; all 8 patients with multiple bronchiectasis had a history of recurrent infections. CONCLUSION: Bronchiectasis is a common finding in alpha-1-antitrypsin deficiency, and is associated with recurrent infections. HRCT is superior to chest radiography as an indicator for the risk of infection in these patients.

Adult↗

PubMed1995

[Conventional roentgen examination of the lung in fibrosing alveolitis--correlation with histological, clinical and biochemical findings].

QUESTION: Is it possible to draw conclusions on aetiology, histology or clinical course, looking at the different radiomorphologic appearance and its changes in chest x-rays of patients with "fibrosing alveolitis"? MATERIAL AND METHOD: Retrospective correlation of chest x-rays with all relevant clinical and histological data of 33 patients. RESULTS: In all patients typical clinical signs with changes of lung function and typical histological changes were found. There was no strict correlation between single parameters and radiological findings. In the estimation of the clinical course, no correspondence between radiological findings and clinical data was found in only 18% of the parameters. CONCLUSION: The chest x-ray is an objective investigation which clearly shows the course of fibrosing alveolitis beside its undisputed function in diagnosing acute complications like infiltration, effusion or development of pneumothorax.

Follow-Up Studies↗

PubMed1995

[Optimizing pelvic MR diagnosis with a new gastrointestinal contrast medium].

AIM: Optimization of pelvic MRI by a new concept of water-equivalent bowel contrast agent. METHODS: We performed contrast enhancement of the bowel by oral application of 1000 ml of an aqueous mannitol solution one hour before pelvic MRI. In addition we performed an enema by 250 ml of water in one patient. RESULTS: Oral and rectal contrast enhancement of the bowel was tolerated without complications by our patients. Pelvic MRI was improved by a better delineation of the bowel. CONCLUSION: The concept of water-equivalent bowel enhancement is promising. It must be assessed by further studies; in particular, it must be compared with the available concepts of positive and negative bowel contrast enhancement.

Adult↗

PubMed1994

[1H-MR spectroscopic imaging: an approach to evaluating alcohol breakdown in the brain].

The local alcohol concentration in the human brain was determined in 10 cases using MR spectroscopic imaging. Therefore 7 subjects with an average blood alcohol concentration of 0.8/000 were examined after oral intake of alcoholic beverages. Varying alcohol concentration was found intracranially which was recorded spectroscopically w.r.t. time. Relatively high ethanol concentrations were determined in the cerebellum as well as in the ventricular system. Contrary to this, lower concentrations were found in the regions of grey and white matter.

Adult↗

PubMed1994

[Computerized tomography of kidney tumors].

Among 220 renal tumors which we detected by computed tomography, there were 168 renal cell carcinomas, 24 tumor of the renal pelvis, 16 angiomyolipomas, 6 Wilms tumors, 3 oncocytomas, one liposarcoma, one mesenchymal tumor, and one rhabdomyosarcoma. Computed tomography had the highest accuracy of the diagnostic procedures with a sensitivity of 99.5% and a specificity of 98%. 83% of the renal cell carcinomas showed signs of malignancy in computed tomography; the staging of the renal tumors by computed tomography was correct in 67% of the cases. The diagnostic value of other diagnostic tools (sonography, urography, angiography, cavography) of renal tumors is discussed in terms of our own results.

Adolescent↗

PubMed1993

[Results of angiographic follow-up of percutaneous stent implantation in the pelvic arteries with a comparison between Wall and Palmaz stents].

51 occlusions of iliac arteries and 67 stenoses have been treated, including 22 patients with bilateral lesions. Indications for stent implantations were: vascular occlusions (51), restenosis following previous PTA (22) and immediate unsatisfactory results or extensive dissection after PTA (45). Successful placement of a stent was achieved in 116 out of 118 attempts. Period of observation averaged 16 months (3-36 months). Stent occlusion was observed in 8 cases. There was mild intima hyperplasia in 25 patients and in a further 14 intima hyperplasia exceeded 75%. Patency rate after 36 months was 67%; 74 wall stents and 39 Palmaz stents were patent, a patency rate of 73 and 65% respectively after 24 months.

Adult↗