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Biomedical subjects

P Held

Publications and source records attributed to P Held.

At least 73 records · Page 4Linked to original sources
PubMed1996

Skeletal muscle metabolism during exercise in patients with chronic heart failure.

OBJECTIVE: To investigate the metabolic response of skeletal muscle to exercise in patients with chronic heart failure and determine its relation to central haemodynamic variables. SETTING: University hospital in Sweden. PARTICIPANTS: 16 patients in New York Heart Association class II-III and 10 healthy controls. MAIN OUTCOME MEASURES: Skeletal muscle biopsies were obtained from the quadriceps muscle at rest and at submaximal and maximal exercise. Right sided heart catheterisation was performed in eight patients. RESULTS: The patients had lower maximal oxygen consumption than the control group (13.2 (2.9) v 26.8 (4.4) ml/kg/min, P < 0.001). They had reduced activities of citrate synthetase (P < 0.05) and 3-hydroxyacyl-CoA dehydrogenase (P < 0.05) compared with the controls. At maximal exercise adenosine triphosphate (P < 0.05), creatine phosphate (P < 0.01), and glycogen (P < 0.01) were higher whereas glucose (P < 0.001) and lactate (P < 0.06) were lower in the patients than in the controls. Citrate synthetase correlated inversely with skeletal muscle lactate at submaximal exercise (r = -0.90, P < 0.003). No correlations between haemodynamic variables and skeletal muscle glycogen, glycolytic intermediates, and adenosine nucleotides during exercise were found. CONCLUSION: Neither skeletal muscle energy compounds nor lactate accumulation were limiting factors for exercise capacity in patients with chronic heart failure. The decreased activity of oxidative enzymes may have contributed to the earlier onset of anaerobic metabolism, but haemodynamic variables seemed to be of lesser importance for skeletal muscle metabolism during exercise.

Adenosine Triphosphate↗
PubMed1996

MR-imaging of the TMJ: artefacts caused by dental alloys.

The aim of the study was to investigate the influence of dental alloys and their components on magnetic resonance imaging of the temporomandibular joint. A plaster and a water- filled acrylic resin phantom - representing the disc and the condyle of the TMJ - were used. Cylindrical crow-type samples of 13 alloys and 14 pure substances were investigated. All alloys were examined with regard to their magnetic susceptibility, using a vibrating sample magnetometer. Metallic artefacts appeared on spin-echo technique as distortions, and on gradient-echo technique signal loss could be observed. Precious alloys were shown to be diamagnetic. The non precious alloys we investigated were paramagnetic. Paramagnetic alloys with a magnetic molar-susceptibility Cmol > 2000 x10(-6) cm3/mol can produce clinically relevant artefacts.

Artifacts↗
PubMed1995

Focal white-matter lesions in brain of patients with inflammatory bowel disease.

Inflammatory bowel diseases are often associated with extra-intestinal manifestations, such as arthritis and iritis/uveitis. Using magnetic-resonance imaging we found hyperintense focal white-matter lesions in the brain in 20 of 48 (42%) patients with Crohn's disease, in 11 of 24 (46%) patients with ulcerative colitis, but in only 8 of 50 (16%) healthy age-matched controls (relative risk [95% CI] vs controls 2.6 [1.3-5.3] and 2.9 [1.3-6.2], respectively). These findings may represent another extra-intestinal manifestation of inflammatory bowel disease.

Adult↗
PubMed1995

Skeletal muscle fiber composition and capillarization in patients with chronic heart failure: relation to exercise capacity and central hemodynamics.

Patients with chronic heart failure have structural and metabolic changes in skeletal muscle, which may be of importance for symptomatology. The origin of these changes are still unknown. The relationship between fiber composition and capillarization in skeletal muscle with exercise capacity and central hemodynamic variables was examined. Biopsies from the lateral vastus muscle were taken in 12 patients with chronic heart failure. Samples from eight normal subjects served as control samples. All patients underwent maximal exercise tests. Central hemodynamic variables were measured during exercise in five patients. The patients had a higher percentage of type II B fibers (P = .03) and fewer capillaries per fiber (P = .02) than the controls subjects. VO2 max correlated with the percentage of type I fibers, whereas the correlation with the type II A fibers was inverse. Cardiac index and pulmonary capillary wedge pressure at submaximal and maximal exercise were related to fiber type composition and relative fiber areas. Skeletal muscle fiber type composition and capillarization was changed in patients with chronic heart failure. These changes might influence exercise capacity. There were relationships between central hemodynamic variables and skeletal muscle changes. What the cause and effects were need further investigation.

Aged↗
PubMed1995

[Accuracy of artificial neural networks in radiological differential diagnosis of solitary bone lesions].

PURPOSE: To evaluate the usefulness of artificial neural networks (ANN) for differential diagnosis of bone tumours and tumour-like lesions. MATERIAL AND TECHNIQUE: Different ANN were designed to distinguish between 23 types of bone lesions and to classify these lesions as benign or malignant on the basis of 28 items of clinical and radiographic information. Training of the feed-forward networks with a back-propagation algorithm was performed using either 46 hypothetical examples or 115 real cases. The data base for testing the different ANN included 115 clinical cases (5 cases for each possible diagnosis), which were different from the examples used for training. The decision performance of the ANN was evaluated by means of ROC analysis. Results were compared to the performance of an experienced radiologist. RESULTS: The radiologist was significantly superior in finding the correct diagnosis (69/115 vs. 41/115; p < 0.001) and the area under his ROC curve (referring to the discrimination between benign and malignant lesions) was slightly larger than that of two different ANN (0.973 vs. 0.945 and 0.973 vs. 0.962 resp.; differences not significant). CONCLUSION: ANN may be potentially useful to distinguish between malignant and benign lesions, but their performance in differentiating between 23 diagnoses must be improved significantly.

Algorithms↗
PubMed1995

The plasma concentrations of isosorbide 5-mononitrate (5-ISMN) administered in an extended-release form to patients with acute myocardial infarction.

Eighteen patients with acute myocardial infarction (AMI) followed the same extended-release isosorbide 5-mononitrate dosage regimen as was used in the Fourth International Study of Infarct Survival (ISIS-4). Plasma drug concentrations, blood pressure and heart rate were measured over 5 to 7 days following acute and repeated administrations. After the initial 30 mg dose on the first day of infarction, mean +/- standard deviation Cmax was 1237 +/- 284 nmol l-1 with a median tmax of 4 h (range 1 to 10 h). Following the last 60 mg dose, Cmax was 2685 +/- 497 nmol l-1 with a median tmax of 4 h (2 to 7 h). The plasma concentrations of this extended-release 5-ISMN in patients with acute myocardial infarction were similar to those seen in studies with healthy volunteers. However, drug absorption following the acute dose was protracted in some patients, possibly due to the concomitant administration of morphine. The kinetics of 5-ISMN at steady state were similar for all patients, and none showed protracted 5-ISMN absorption.

Adult↗
PubMed1995

Renal arteries: evaluation with optimized 2D and 3D time-of-flight MR angiography.

PURPOSE: To compare two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) techniques in magnetic resonance (MR) angiography of renal arteries. MATERIALS AND METHODS: In 46 patients, MR angiography was performed with 3D tilted optimized non-saturating excitation (TONE), 3D fast imaging with steady precession (FISP), and 2D fast low-angle shot (FLASH) during breath holding. Intraarterial angiography was used as a reference. MR angiograms were evaluated for stenoses, length of renal arteries, accessory arteries, venous overlap, and image quality. RESULTS: The 3D TONE sequence was best for detection of severe stenoses (sensitivity, 100%; specificity, 89%), delineation of accessory arteries, and image quality. Overlap of renal veins was the most important disadvantage of 2D FLASH. Decreased saturation effects, however, can be advantageous in 2D TOF imaging. CONCLUSION: Use of the 3D TONE sequence provided improved image quality and diagnostic value compared with 3D FISP technique. The 2D TOF sequence can be useful in combination with the 3D TONE sequence.

Adult↗
PubMed1995

Three-dimensional MP-RAGE--an alternative to conventional three-dimensional FLASH sequences for the diagnosis of viscerocranial tumours?

Imaging with three-dimensional (3D) sequences is a frequently used magnetic resonance (MR) technique in the assessment of ear, nose and throat (ENT) tumours near the skull base. Few reports on the contrast behaviour of 3D magnetization prepared rapid gradient echo (MP-RAGE) sequences and their application in ENT tumours exist in the published literature. This paper discusses whether 3D MP-RAGE is an alternative to conventional 3D gradient echo (3D GE) sequences for the diagnostic evaluation of the visceral cranum. Measurements were performed with a Magnetom SP 63 MR system (Siemens) at 1.5 T. 10 healthy volunteers were examined using 3D FLASH sequences with varied flip angles (90 degrees, 70 degrees, 40 degrees, 20 degrees, 10 degrees) and using 3D MP-RAGE to optimize the signal-to-noise ratio (SNR) of muscle, fat and gland tissue. After this optimization 25 patients with ENT tumours near the skull base were examined with 3D FLASH 40 degrees, 3D MP-RAGE 10 degrees (both before and after application of contrast medium) and with 3D FISP 70 degrees (without contrast medium). SNR and contrast-to-noise ratio (CNR) of tumour, inflammatory disease, brain (white and grey matter), compact bone, fat and muscle were calculated. The advantages of 3D MP-RAGE over 3D FLASH 40 degrees include decreased imaging time with decreased motion artifacts and a relatively high contrast between tumour and surrounding tissues. The tissue contrast yielded by the T1/T2* weighted 3D gradient echo sequence FISP with a flip angle of 70 degrees was not as good as that yielded by 3D MP-RAGE with and without contrast together. In conclusion a combination of contrast enhanced and unenhanced 3D MP-RAGE sequences is the technique of choice for the examination of ENT tumours near the base of the skull.

Adult↗
PubMed1995

Comparative study of results of electronic axiography with results of magnetic resonance imaging including MRI-assisted splint therapy.

The most common temporomandibular joint disturbance is the internal derangement. Its prevalence has been shown to be as high as 28%. The purpose of this study was on one hand to compare the diagnostic efficiency of an electronic axiographic system with magnetic resonance imaging, and, on the other hand to evaluate the results of MRI-assisted treatment monitoring of occlusal splint therapy. The results of this survey clearly show that in evaluation of temporomandibular joint disorders, electronic axiography and magnetic resonance imaging should be used in conjunction with one another to increase the accuracy of positive and differentiated diagnoses. The medical concept of disc recapture involving the use of occlusal splints seems to be merely a clinical term which is not necessarily hinged on anatomical intraarticular changes.

Adult↗
PubMed1995

The rationale for nitrates in angina pectoris.

Organic nitrates are among the oldest drugs used in the management of patients with ischemic heart disease. The most frequently used nitrates are nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate. Their duration of action can be influenced by choice of substance, frequency of administration, formulation (eg, extended release) and route of administration. As well as providing effective treatment of acute angina, nitrates produce a long term prophylactic effect. Stable plasma nitroglycerin levels lasting longer than 10 to 12 h are not desirable due to the rapid development of tolerance. Simple, well-designed dosing schedules can avoid tolerance and rebound phenomena and can improve patient compliance.

Angina Pectoris↗
PubMed1995

High-resolution SPECT of the temporomandibular joint in chronic craniofacial pain disorders: a pilot study.

Chronic craniofacial pain disorders commonly cause physicians diagnostic difficulties. The purpose of this study was, on one hand, to detect pathological focuses of the craniofacial skeleton using a new system of high-resolution single photon emission computertomography (SPECT), and on the other hand, to compare the results with those obtained via high-field magnetic resonance imaging (MRI) as far as temporomandibular joint affections are concerned. SPECT can be regarded as a supplementary diagnostic mean for patients displaying the symptoms of chronic craniofacial pain disorders, especially in cases where clinical and paraclinical investigations do not coïncide or which are refractory to treatment, not least to differentiate between somatic and psychogenic causes, respectively.

Adult↗
PubMed1994

MRI and CT of tumors of the pharynx: comparison of the two imaging procedures including fast and ultrafast MR sequences.

The aim of this prospective study was to compare the diagnostic value of computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of tumors of the nasopharynx, oropharynx and hypopharynx. For this reason, we performed CT and MRI in a total of 473 patients with neoplasms of the nasopharynx [116], oropharynx [282] and hypopharynx [39]. Furthermore, the MR imaging protocol had to be optimized including 2D and 3D gradient echo sequences. We compared the use of conventional and fast spin echo and 3D gradient echo sequences for the evaluation of tumors of the nasopharynx and the skull base, and we evaluated 2D fast and ultrafast MR sequences for the detection and delineation of tumors of the oropharynx and hypopharynx. MRI yielded better results than CT in the detection of pharyngeal neoplasms. The differentiation of tumor and inflammatory tissue was best achieved using MRI. Contrast-enhanced 3D GE sequences improved the diagnostic value of MRI of the nasopharynx. Fast and ultrafast 2D MR sequences increased the contrast between orofacial tumors and surrounding tissues. Functional MR images (phonation studies, Valsalva's maneuver) were attainable using ultrafast sequences thus enhancing the diagnostic value of MRI in the case of tumors of the hypopharynx. T2-weighted turbo (fast) spin echo sequences with relatively short acquisition times proved to be superior to conventional T2-weighted spin echo sequences. In conclusion, MRI is the imaging modality of choice in the evaluation of pharyngeal neoplasms. Conventional T2-weighted SE should be substituted by fast T2-weighted SE sequences. 3D GE sequences should be integrated in the MR imaging protocol of the nasopharynx. Fast and ultrafast 2D GE sequences should be applied in the evaluation of tumors of the oropharynx and hypopharynx.

Humans↗
PubMed1994

MRI of orofacial tumors and paragangliomas with 2D GE sequences: indications and optimal sequence parameters.

The aim of this paper is to determine to what extent and in which cases 2D gradient echo (2D GE) sequences can be applied alternatively or additionally to spin echo (SE) sequences for improved diagnostic evaluation. Imaging with SE sequences is the most frequently used MR technique in the assessment of ear, nose and throat (ENT) tumors. In literature there are only a few reports on the contrast behaviour of 2D GE sequences using different sequence parameters and their application in ENT tumors. This paper set out to establish the most suitable sequence type and sequence parameters. Measurements were performed with a Magnetom SP 63 MR system (Siemens) with a field strength of 1.5 T, using head and Helmholtz coils. One-hundred twenty-eight volunteers and 369 patients were examined with 2D GE sequences. In order to find the best MR technique for the examination of orofacial tumors and paragangliomas, FLASH, FISP and PSIF sequences with different sequence parameters (TR, TE, flip angle, bandwidth) were applied. The results of these examinations confirmed the superiority of 2D GE sequences over SE sequences. In conclusion, contrast enhanced or unenhanced T1 weighted SE sequences should be replaced by 2D GE FLASH 70 degrees in the examination of orofacial tumors. In the case of paragangliomas of the jugular bulb and the parapharyngeal space T1- and T2-weighted SE sequences should be replaced by 2D GE FLASH 40 degrees.

Head and Neck Neoplasms↗
PubMed1994

[CT and MRI in tumors of the hypopharynx and larynx--comparison of methods with reference to rapid and ultra-fast MR pulse sequences].

A total of 86 patients with malignant tumours of the hypopharynx and larynx were examined with CT and MRI. The most frequent malignant tumours of the larynx namely, the glottic carcinomas, were better detected with CT than with MRI. The other tumours of the larynx, however, were better visualised with MRI. MRI proved superior to CT in the detection and staging of carcinomas of the hypopharynx. Functional MR images (phonation studies, Valsalva's manoeuvre) were attainable using ultrafast sequences, thus enhancing the diagnostic value of MRI. MRI proved superior to CT enabling a better differentiation of recurrent tumours, inflammatory tissue and scar. For this purpose, T1-weighted plain and contrast-enhanced spin-echo images and T2-weighted spin-echo images were necessary in most cases. T2 weighting turbo spin-echo sequences with relatively short acquisition times proved superior to conventional T2 weighting spin-echo sequences; thanks to shorter acquisition times, the motion artifacts could be reduced and the image quality improved.

Carcinoma, Squamous Cell↗
PubMed1994

[Comparison of CT and MRI methods in diagnosis of tumors of the para- and retropharyngeal space and temporal bone].

The aim of this paper was to compare the diagnostic value of computed tomography (CT) and magnetic resonance imaging (MRI) in the evaluation of malignant tumors of the temporal bone, of paragangliomas of the glomus tympanicum and jugulare as well as of malignant tumors of the para- and retropharyngeal space. 67 patients with tumors of the temporal bone--28 cases with malignant tumors and 39 cases with paragangliomas--were examined with MRI and CT. MRI had true-positive findings in nearly 93, CT in 89% of the patients with malignant tumors of the temporal bone. MRI is therefore recommended as the primary imaging investigation of malignant tumors of the temporal bone. Whereas the temporal bone is best visualized by high-resolution CT with thin slices, the tumor extension--especially cranial spread into the middle and posterior cranial fossa and caudal spread into the infratemporal fossa--is better detected on MRI. Enhanced T1-weighted spin-echo images with fat-signal suppression are most suitable for this purpose. Using 3D sequences, partial volume effects can be avoided with an attainable slice thickness of 0.8-1.0 mm. Furthermore, arbitrary slices--very helpful when studying the complex anatomy of the skull base--can be calculated from a 3D data set. MRI had true-positive findings in 97, CT in nearly 90% of the patients with paragangliomas. Furthermore, the response of paragangliomas to radiotherapy can be more accurately assessed on MR--independent of and before volumetric changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast Media↗
PubMed1994

[Indications for and pertinence of 3D tomodensitometry in panfacial fractures].

Successful treatment of panfacial fractures is dependent on precise clinical and radiological examinations. However, the complexity of fracture lines accounts for the problems and inadequacies of plain films. Three-dimensional CT-reconstruction is recommended to help the maxillofacial surgeon to conceptualize the overall injury. Subsequently, a case involving complex panfacial fractures is presented and the potential value of three-dimensional computed tomography is discussed.

Facial Bones↗
PubMed1994

[Comparison of CT and MRI in diagnosis of tumors of the nasopharynx, the inner nose and the paranasal sinuses].

A total of 292 patients with tumors of the nasopharynx, the nose and the paranasal sinuses--264 cases with malignant tumors--were examined with magnetic resonance imaging (MRI) and computed tomography (CT) for comparison. MRI yielded better results than CT in the detection and staging of neoplasms of the nasopharynx (detection: CT 84.9%, MRI 96.7%; staging: CT 75.2%, MRI 92.4%). The walls and septae of the paranasal sinuses and of the skull base were in all cases best visualized on high-resolution CT with thin slices. Tumor detection, differentiation of tumor and inflammatory tissue and staging, however, were better achieved using MRI than CT (detection: CT 84.7%, MRI 91.6%; staging: CT 78.6%, MRI 80.9%). The use of fast and ultrafast MR sequences (alternatively or additionally to 'conventional' spin echo sequences) improved the tumor diagnosis. We therefore recommend that patients with tumors of the nasopharynx, the nose and the paranasal sinuses undergo MRI with fast spin echo and gradient echo sequences as first imaging modality.

Adenocarcinoma↗