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Biomedical subjects

W Kenn

Publications and source records attributed to W Kenn.

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

[Cardiac energy metabolism in heart valve diseases with 31P MR spectroscopy].

PURPOSE: Heart valve disease combined with left ventricular hypertrophy leads to derangements in cardiac energy metabolism, which can be detected non-invasively by 31P-MR-spectroscopy. The purpose of the present study was to examine whether the derangements in cardiac metabolism are reversible after surgical valve replacement. PATIENTS AND METHODS: 10 healthy volunteers and 10 patients with aortic stenosis (pressure gradients > 60 mmHg) were included. For assessment of energy metabolism, 31P-MR spectra were obtained with a double oblique 3D-CSI technique (voxel size 25 cm3). In 5 of 10 patients, follow-up examination was performed 3 months after surgical valve replacement (SVR). Left ventricular (LV) function was analyzed by cine MRI. RESULTS: Before SVR the myocardial phosphocreatine to adenosinetriphosphate (PCr-ATP) ratio was significantly (p = 0.0002) reduced to 0.80 +/- 0.25 in patients compared to 1.65 +/- 0.21 in volunteers. 3 months after SVR, LV mass had significantly (p = 0.04) decreased from 238 +/- 33 g to 206 +/- 47 g. At the same time a significant (p = 0.04) increase of the PCr-ATP ratio from 0.80 +/- 0.25 to 1.28 +/- 0.22 was observed. A slight, but not significant, reduction of the phosphodiester ATP ratio was observed before SVR, with a trend towards normalization after SVR. CONCLUSIONS: After SVR, the deranged energy metabolism shows a trend towards normalization. Further follow-up is necessary to determine whether complete normalization of the energetic derangement can be observed over longer periods of time following SVR.

Adult↗
PubMed2000

Altered energy metabolism after myocardial infarction assessed by 31P-MR-spectroscopy in humans.

The value of 31P-magnetic resonance spectroscopy (MRS) as a possible tool to distinguish viable from non-viable tissue after myocardial infarction was analysed in humans. Fifteen patients 3 weeks after anterior myocardial infarction were studied with breath-hold cine MRI and 3D-CSI MRS (1.5 T system). 31P-spectra were obtained from infarcted as well as non-infarcted myocardium (voxel size 25 cm3 each). Gold standard for viability was recovery of regional function, as determined by a control MRI 6 months after revascularization. Ten age-matched healthy volunteers served as control group. No significant difference was found between the phosphocreatine to adenosinetriphosphate (PCr/ ATP) ratio of volunteers (SD 1.72+/-0.31) and non-infarcted septal myocardium of patients. Cine MRI demonstrated recovery of regional function in 10 patients, i. e. 10 patients showed viable and 5 non-viable myocardium. In viable myocardium, the PCr/ATP ratio was 1.47+/-0.38 (non-significant vs volunteers; p>0.05). In the 5 patients with akinetic myocardium, PCr peaks could not be detected. Therefore, calculation of PCr/ATP ratios was not possible. However, a significant reduction of the ATP signal-to-noise ratio (SNR) was observed (2.92+/-0.73 vs 6.68+/-0.80; patients vs volunteers; p<0.05). The SNR of ATP of akinetic regions may predict recovery of function after revascularization in patients with myocardial infarction.

Adenosine Triphosphate↗
PubMed2000

Technical advances in ultrasound and MR imaging of carpal tunnel syndrome.

The aim of this study was to compare the latest ultrasound-array technology to a conventional "high-resolution" transducer, modified MRI technique, and nerve conduction studies (NCS), in the diagnosis of carpal tunnel syndrome (CTS). In 19 normal wrists and 15 wrists with CTS, US with two different transducers was performed: a conventional linear-array transducer (LA) and a newly developed Multi-D linear-array transducer (MDA) were used. The US images were evaluated determining the swelling and the flattening ratios of the median nerve and correlated to respective findings in MRI (1.5 T) and to NCS. The NCS confirmed CTS in all 15 wrists. Measures of median nerve compression (swelling and flattening ratios) were significantly different in patients with CTS and controls (p < 0.01) with both types of US transducers and MRI. The MDA yielded higher correlation to MRI than the LA. Using critical values of 1.3 for the swelling and 3.4 for the flattening ratio, MRI, and US with the MDA yielded a sensitivity of 100% each. Modern imaging modalities allow for an exact diagnosis of CTS even in cases with only slight median nerve pathology.

Adult↗
PubMed2000

Age- and gender-specific differences in left and right ventricular cardiac function and mass determined by cine magnetic resonance imaging.

We examined possible age- and gender-specific differences in the function and mass of left (LV) and right (RV) ventricles in 36 healthy volunteers using cine gradient-recalled echo magnetic resonance imaging. Subjects were divided into four groups (nine men and nine women in each): men aged under 45 years (32 +/- 7), women aged under 45 (27 +/- 6), men aged over 45 (59 +/- 8), and women aged over 45 (57 +/- 9). Functional analysis of cardiac volume and mass and of LV wall motion was performed by manual segmentation of the endocardial and epicardial borders of the end-diastolic and end-systolic frame; both absolute and normalized (per square meter body surface area) values were evaluated. With age there was a significant decrease in both absolute and normalized LV and RV chamber volumes (EDV, ESV), while LV and RV masses remained unchanged. Gender-specific differences were found in cardiac mass and volume (for men and women, respectively: LV mass, 155 +/- 18 and 110 +/- 16 g; LV EDV, 118 +/- 27 and 96 +/- 21 ml; LV ESV, 40 +/- 13 and 29 +/- 9 ml; RV mass, 52 +/- 10 and 39 +/- 5 g; RV EDV, 131 +/- 28 and 100 +/- 23 ml; RV ESV, 53 +/- 17 and 33 +/- 15 ml). Normalization to body surface area eliminated differences in LV volumes but not those in LV mass, RV mass, or RV function. Functional parameters such as cardiac output and LV ejection fraction showed nonsignificant or only slight differences and were thus largely independent of age and gender. Intra- and interobserver variability ranged between 1.4% and 5.9% for all parameters. Cine magnetic resonance imaging thus shows age- and gender-specific differences in cardiac function, and therefore the evaluation of cardiac function in patients should consider age- and gender-matched normative values.

Adult↗
PubMed2000

Erdheim-Chester disease: evidence for a disease entity different from Langerhans cell histiocytosis? Three cases with detailed radiological and immunohistochemical analysis.

Erdheim-Chester (EC) disease is a rare pathological entity with a highly specific and characteristic pattern of radiographic bone changes. Histologically it resembles Langerhans cell histiocytosis (LCH), and it is still a matter of discussion whether EC disease is a distinct entity or a type of LCH. In this study, 3 cases of Erdheim-Chester disease were followed up over years and examined in detail both radiologically and immunohistochemically. All 3 cases showed the pathognomonic skeletal features for EC disease as well as an identical immunohistochemical phenotype quite different from LCH. Macrophages and Touton cells reacted strongly positive with the histiocytic marker CD 68, whereas staining with S100 and CD1a, markers for Langerhans cells, were negative. Both the immunohistochemical phenotype and the bone changes were clearly distinct from LCH.

Antigens, CD↗
PubMed2000

[Arthrography, ultrasound and MRI in rotator cuff lesions: a comparison of methods in partial lesions and small complete ruptures].

PURPOSE: To evaluate the accuracy of arthrography, ultrasound and MR imaging in rotator cuff disease. METHODS: 40 patients suffering from subacromial impingement syndrome for at least three months and who were selected for surgery, underwent ultrasound, double-contrast arthrography and MR imaging. Patient preselection focused on partial and small complete tears. RESULTS: 13/26 surgically confirmed tears were partial tears (articular surface: 10, bursal surface: 2, intra-substance tearing: 1). Arthrography, ultrasound and MR imaging yield a sensitivity for complete tears of 91%, 69% and 92% with a specificity of 100%, 93% and 93%. For partial tears sensitivity was 50%, 69% and 69% with a specificity of 100%, 79% and 86%. Concerning evaluation of localisation, extent and correct classification ultrasound was correct in 17/26 cases, MR in 21/26 cases. CONCLUSION: Arthrography is not helpful in detecting partial tears. Ultrasound and MR imaging yield comparable accuracy. MR imaging has advantages concerning better evaluation of extent, location and classification as well as for the detection of associated pathologies.

Arthrography↗
PubMed2000

[(23)sodium MRI for infarct imaging of the human heart].

PURPOSE: Sodium is elevated in acute/subacute myocardial infarction due to three distinct mechanisms: Breakdown of ion homeostasis with accumulation of intracellular sodium, extracellular edema formation and, during scar formation, increase of extracellular vs. intracellular space as cardiomyocytes are replaced by connective tissue. 23Na MRI has previously been shown to have the potential to demonstrate myocardial infarction in an animal model. Aim of this study was, therefore, to demonstrate myocardial infarction with the use of 23Na-MRI in patients. MATERIAL AND METHODS: 10 patients were examined 14 +/- 7 days after first myocardial infarction using a 23Na surface coil at 1.5 T. Double angulated short axis images of the entire heart were imaged using an ECG-triggered 3d-FLASH-sequence (FOV, 450 mm; matrix, 64 x 128; spatial resolution, 3.5 x 7 mm2; slice thickness, 16 mm; 32 acquisitions). Areas of elevated sodium signal intensity were correlated with infarct-related wall motion abnormalities imaged by Cine MRI in breathhold-technique. RESULTS: All patients showed an area of elevated sodium signal intensity that correlated well with the clinically determined localization of myocardial infarction as well as with regional wall motion abnormalities detected by Cine MRI. CONCLUSIONS: Elevated 23Na MR image signal intensity demonstrates subacute myocardial infarction in patients.

Aged↗
PubMed2000

Analysis of first-pass and delayed contrast-enhancement patterns of dysfunctional myocardium on MR imaging: use in the prediction of myocardial viability.

OBJECTIVE: The purpose of the study was to analyze first-pass and delayed contrast-enhancement patterns of dysfunctional myocardial regions on MR imaging after injection of gadopentetate dimeglumine to predict myocardial viability in patients with coronary artery disease. SUBJECTS AND METHODS: Twelve patients with wall motion abnormalities and related coronary artery disease revealed by conventional coronary angiography underwent MR imaging at 1.5-T before and 3 months after revascularization therapy. Short-axis images were acquired using a cine gradient-echo sequence. Each slice was divided into eight segments. Overall, 73 segments with impaired contractility were imaged during the first-pass and 14 +/- 2 min after injection of 0.05-mmol/kg gadopentetate dimeglumine at a flow of 3 ml/sec using a T1-weighted turbo fast low-angle shot sequence. Improved systolic wall thickening 3 months after revascularization served as the criterion of viability. RESULTS: At study entry, 26 dysfunctional segments showed delayed hyperenhancement compared with the adjacent functional segments within the same slice, and 47 did not reveal hyperenhancement. After revascularization, 25 (96%) of the 26 hyperenhanced segments did not recover function, whereas 39 (83%) of the 47 segments without hyperenhancement showed mechanical improvement. Segment-related sensitivity and specificity for the correlation of lack of delayed hyperenhancement with myocardial viability were 39 (98%) of 40 and 25 (76%) of 33, respectively. Hypoenhancement during first-pass did not serve as a reliable criterion of viability. CONCLUSION: Evidence of delayed hyperenhancement of dysfunctional myocardium may be used to predict lack of mechanical improvement or nonviability, whereas the lack of hyperenhancement can be correlated with improvement of regional contractility or viability after revascularization.

Aged↗
PubMed1999

Erdheim-Chester disease: a case report and literature overview.

Erdheim-Chester (EC) disease belongs to the group of lipoid granulomatosis. Symmetric sclerosis of the meta- and diaphysis of long tubular bones are pathognomonic radiologic changes. Additionally, other skeletal segments can be affected. Extraskeletal manifestations can occur in almost all organs; lungs, pericardium, retroperitoneum, skin, and orbita play particularly important roles. The last case of 38 cases of Erdheim-Chester disease with an extraordinary mediastinal and perirenal involvement is described. For the second time following the initial description by Chester, an axial skeletal pattern of eburnated vertebra is shown.

Aged↗
PubMed1999

Spiral CT angiography of renal arteries: comparison with angiography.

A prospective study was carried out to determine the accuracy of spiral CT angiography (CTA) in the detection of renal artery stenosis (RAS). Eighty-two patients with arterial hypertension underwent CTA and digital subtraction angiography (DSA) to exclude RAS. For CTA a contrast medium bolus of 100-150 ml (flow rate 3 ml/s) was injected. A 24 or 40 s CTA was started at the origin of the superior mesenteric artery after a delay time determined by test bolus injection (collimation = 2 mm, pitch = 1/1.5). For stenosis detection transverse images supported by maximum intensity projections (MIP) or multiplanar reconstruction projections were used. Of 197 renal arteries examined (including 33 accessory arteries), 34 RAS were visualized using DSA. With CTA, one hemodynamic RAS was missed and one additional hemodynamic RAS was found. Sensitivity/specificity was calculated to be 94 %/98 %. For hemodynamically relevant RAS (> 50 %) the sensitivity/specificity was 96 %/99 %. CTA additionally depicted five adrenal masses. The high accuracy rate of RAS detection thus allows the use of CTA as a screening method in patients with arterial hypertension to exclude a renovascular cause.

Adult↗
PubMed1999

Current value of double-contrast pharyngography and of computed tomography for the detection and for staging of hypopharyngeal, oropharyngeal and supraglottic tumors.

In light of recent endoscopic techniques the current value of double-contrast pharyngography (DCP) and of CT for detection and staging of hypo-, oropharyngeal, and supraglottic tumors is evaluated. The DCP of 151 patients and CT obtained from 99 of these patients were retrospectively analyzed in a double-blinded manner. We used a standard protocol which comprised all relevant anatomical subregions. Results were compared with direct microlaryngoscopy (DL), indirect laryngoscopy (IL), and post-operative histopathological findings. Sensitivity and specificity of DCP was 75.0 % and 86.7 %, respectively. The DCP and IL techniques together yielded a higher sensitivity (96.7 %) than each method separately. Sensitivity and specificity of CT was 87.5 and 100 %, respectively. In 74.7 % CT provided correct staging. Subregional analysis revealed that the results of DCP and CT depend highly on the localization of the tumor. Our results indicate that DCP represents an important screening method for diagnosing hypo-, oropharyngeal, and supraglottic tumors to complete IL and DL. We show that CT is a reliable method for preoperative staging, although small superficial tumors may occasionally be missed by this method.

Administration, Oral↗
PubMed1999

Detection of myocardial viability by low-dose dobutamine Cine MR imaging.

The purpose of this work was to test the diagnostic value of dobutamine stress magnetic resonance imaging (MRI) for predicting recovery of regional myocardial contractility after revascularization. Cardiac wall motion abnormalities are due to either non-viable and/or scarred, or viable, but hibernating, myocardial tissue. Dobutamine stress leads to increased systolic wall thickening only in viable myocardium. Twenty-five patients with akinetic or dyskinetic myocardial regions were examined with a Cine FLASH-2D sequence at rest and during dobutamine stress (10 microg/kg/min). Patients were re-examined at rest 3, and in case of persisting wall motion defects, 6 months after revascularization. Criterion of viability was increasing end-systolic wall thickening during stress and/or at follow-up. Akinetic regions related either to the LAD (n = 19) or to the RCA (n = 6) were judged viable if > or = 50% of the affected segments improved. MR studies were completed in all subjects without arrhythmia or need for early terminations due to symptoms. Sensitivity, specificity, and positive predictive value for the prediction of myocardial viability were 61%, 90%, and 87% for the segment-related analysis, and 76%, 100%, and 100% for the patient-related analysis based on coronary artery distribution, respectively. Dobutamine stress MRI allows to predict global functional recovery of akinetic myocardial regions after revascularization with a high positive predictive value and high specificity.

Adult↗
PubMed1999

Cine MR imaging after myocardial infarction--assessment and follow-up of regional and global left ventricular function.

Myocardial infarction often leads to regional wall motion defects and in case of large defects to remodeling of the left ventricle. With this study, changes in regional and global myocardial function of 12 patients 3 weeks after myocardial infarction and after revascularization therapy were determined using MRI. Cine MRI was performed at study entry at rest and during low-dose dobutamine stimulation. All patients were re-examined at rest 3 and 6 months after the revascularization, including analysis of wall thickening and of left ventricular end-diastolic volume index (LVEDVI), end-systolic volume index (LVESVI), ejection fraction (LVEF), and mass index. After revascularization. 6 patients with stress-induced improvement of regional wall thickening recovered, 4 patients without improvement did not, but 2 patients without stress-induced improvement of wall thickening also recovered. Concerning global cardiac function, patients with mainly improved regional wall motion also showed a lower LVESVI and a higher LVEF than patients without improvement of regional contractility 6 months after revascularization in comparison to study entry. In conclusion, improvement of global myocardial function after revascularization is higher in patients with improved contractility in the infarcted region. The extent of the response of regions with wall motion defects to dobutamine stress correlates with the actual improvement after revascularization, and, therefore, dobutamine stress MRI may be helpful in selecting patients that will have a higher benefit from a revascularization therapy.

Adult↗
PubMed1999

[CINE-MRT for the study of the effects of regional left ventricular wall motion disorders on global heart function after a myocardial infarct and revascularization].

PURPOSE: To determine changes in global cardiac function and mass caused by infarct-associated regional wall motion abnormalities and to compare the changes after revascularization in patients with and without improvement of regional contractility. MATERIALS AND METHODS: 21 patients with regional left ventricular wall motion abnormalities and associated coronary artery stenoses requiring revascularization were examined with a Cine FLASH-2D sequence 26 +/- 12 days after their first myocardial infarction and re-examined three months after revascularization. Regional contractility and volumes and masses of both ventricles were determined. RESULTS: After revascularization, regional wall motion improvement led to decreased left ventricular volumes and improved ejection fractions, whereas patients with persisting wall motion defects showed unchanged left ventricular functional parameters. Comparing both groups of patients, the patients with improvement of regional contractility revealed lower end-systolic volumes and higher ejection fractions at follow-up. Cardiac masses and right ventricular parameters were not different, patients with a depressed right ventricular ejection fraction showed improvement at follow-up. DISCUSSION: After myocardial infarction, revascularization of the infarct-related coronary artery leads to an improvement of left ventricular function only if there is also an improvement of regional contractility. An effect on right ventricular function was not observed three months after the first small- or middle-sized myocardial infarction.

Adult↗
PubMed1999

[The quantification of energy-rich phosphates in healthy and damaged heart muscle by SLOOP 31P-MR spectroscopy. Spatial localization with optimal pointspread function].

PURPOSE: A quantitative 31P-MR-spectroscopic technique was used to assess the energy metabolism in healthy and diseased myocardium. METHODS: 31P spectra were acquired on a 1.5 T scanner using a 3D-chemical shift imaging technique. Based on the anatomical information provided by 1H images, SLOOP (Spatial Localization with Optimal Pointspread Function) allows to obtain spectra from defined compartments. With SLOOP a free voxel shape with adaption to anatomic structures, e.g. the myocardium, is possible. Absolute values for phosphocreatine (PCr) and adenosine triphosphate (ATP) were determined using an external standard. RESULTS: 31P-spectra showed only minimal contamination by surrounding tissue. The standard deviation for the determined values of healthy volunteers was low. Compared to healthy volunteers, reduced PCr and ATP concentrations were seen for dilative cardiomyopathies and coronary artery disease and unchanged concentrations were observed for hypertensive heart disease. CONCLUSION: 31P-MR spectroscopy with SLOOP allows a non-invasive, quantitative analysis of cardiac energy metabolism.

Adenosine Triphosphate↗
PubMed1999

[3-dimensional MR coronary angiography in the navigator technic for the primary diagnosis of coronary heart disease: a comparison with conventional coronary angiography].

PURPOSE: Evaluation of three-dimensional MR coronary angiography with the navigator technique for the primary diagnosis of coronary artery disease (CAD) in patients with chest pain. MATERIALS AND METHODS: In this prospective study 20 patients with chest pain were examined with MR coronary angiography and conventional angiography. The three-dimensional MR coronary angiography was performed using a 1.5 T scanner with an ECG-triggered 3D-FLASH-sequence and retrospective respiratory gating in the navigator technique. The MR coronary angiography was evaluated by two radiologists blinded to the results of the conventional coronary angiography. RESULTS: One patient was excluded from further evaluation due to reduced image quality. Conventional coronary angiography excluded CAD in 8/19 patients, 11/19 patients overall showed 20 stenoses (> 50%) or occlusions. With MR coronary angiography, CAD was correctly excluded in 7 patients, one patient was false positive, one patient was false negative. 14/20 stenoses (> 50%) or occlusions were detected, 5 stenoses were diagnosed false positive. Sensitivity and specificity for primary diagnosis of CAD or detection of coronary artery stenoses were 91% and 88% or 70% and 91%, respectively. DISCUSSION: Using MR coronary angiography with the navigator technique in the primary evaluation of CAD, the diagnosis of stenoses or occlusions of the main coronary arteries is feasible.

Adult↗
PubMed1999

Three-dimensional MR coronary angiography using the navigator technique compared with conventional coronary angiography.

OBJECTIVE: We evaluated the diagnostic accuracy of three-dimensional (3D) MR coronary angiography with the navigator technique for the detection of coronary artery stenoses in comparison with that of conventional radiographic angiography. SUBJECTS AND METHODS: Thirty patients with coronary artery disease were examined with an ECG-triggered 3D fast low-angle shot sequence using retrospective respiratory gating and the navigator technique on a 1.5-T MR scanner. The data set was evaluated as a 3D view with a surface rendering technique. RESULTS: Imaging of the proximal coronary arteries was possible in all patients. The average visualized lengths of the left main, left anterior descending, left circumflex, and right coronary arteries were 1.9+/-0.5 cm (mean +/- SD), 5.2+/-2.3 cm, 4.2+/-1.9 cm, and 5.2+/-2.5 cm, respectively. Irregular breathing reduced image quality in seven of the 30 patients, making diagnosis of stenoses impossible. In the 77% of patients whose examinations resulted in high-quality images, the sensitivity and specificity for detection of significant stenoses and occlusions in all four main coronary arteries were 81% and 89%, respectively. CONCLUSION: The navigator technique allows reproducible imaging of the proximal course of coronary arteries. This technique obviates breath-hold studies, thus allowing more patients to be examined. In patients whose examinations resulted in high-quality images, significant coronary artery lesions could be seen. However, for widespread clinical use, further technical improvement is necessary to increase sensitivity and specificity.

Adult↗