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P Held

Publications and source records attributed to P Held.

At least 55 records · Page 3Linked to original sources
PubMed1998

3D MRI of the membranous labyrinth. An age related comparison of MR findings in patients with labyrinthine fibrosis and in persons without inner ear symptoms.

PURPOSE: We compared MRI of the membranous labyrinth in patients with chronic non-neoplastic inner ear disease and MR signs of labyrinthine fibrosis and controls depending on their age, in order to establish whether there were any MR differences regarding patient age groups, control age groups and between the patients and controls themselves. MATERIALS AND METHODS: Clinical ENT examinations as well as a T2* weighted 3D CISS (Constructive Interference in Steady State) sequence with a slice thickness of 0.7 mm were performed. Our collective was subdivided as follows: 0-19 years (10 controls, 3 patients with chronic non-neoplastic inner ear disease), 20-49 years (55 controls, 8 patients), 50 years and older (40 controls, 22 patients). Detectability of labyrinthine structures (e.g. cochlea, vestibule, semicircular canals) and filling defects were evaluated. RESULTS: In the 3 age-groups of the control collective no significant differences were observed in the membranous labyrinth. However differences concerning labyrinthine detectability emerged between controls and patients in both the 20-49 years and 50 years and older age groups. In the patient collective the 3 age groups showed no significant discrepancy in the mean number of lesions. CONCLUSION: Filling defects of the membranous labyrinth on 3D CISS MR images are pathological even in older persons. We would therefore recommend high resolution T2* weighted MRI in the case of suspected labyrinthine fibrosis.

Adolescent↗
PubMed1997

[Anesthesia for magnetic resonance tomography in neonates, infants and young children].

INTRODUCTION: Since patient cooperation in neonates and infants up to 5 years is always reduced, deep sedation is usually recommended to obtain constant high-quality images during MRI. According to the widely accepted AAP Guidelines, deep sedation is not always distinguishable from general anesthesia, substantiating the demand for state-of-the-art anaesthesia. This is particularly true in this age group, where pharmacokinetics and pharmacodynamics show wide interindividual variation. In this review we outline the techniques required to provide safe and effective patient care in the unique MRI environment. CHOICE OF DRUGS AND PROCEDURE: From the viewpoint of induction time, half-life of action and success rate, we have found that inhalation anesthetics and propofol present clear advantages. Both offer rapid induction and emergence, allowing outpatient examinations in a tight schedule with a reliable sedation state. Tracheal intubation or a laryngeal mask airway is required to supply volatile anesthetics and to secure the airway, since propofol in appropriate doses causes respiratory depression and loss of the protective reflexes. Positive-pressure ventilation is recommended since the reduction of tidal volumes by sedative drugs (including high-dose chloral hydrate, barbiturates) may cause atelectasis and decreased oxygen saturation. ANESTHESIA MACHINES: Several respirators work well outside a critical magnetic field strength of 10 mT (e.g. Draeger: Titus, Siemens: Servo 900). The use of long low-compliance tubing (4-5 m) allows the respirator to be placed at the distal end of the patient table. Sidestream capnometry and spirometry at the proximal tube connector facilitate compensation for losses in tidal volume due to gas compression. Syringe pumps work properly when kept outside the 10 mT line. Some defibrillators (e.g., Lifepac, Physiocontrol) are approved for use in strong magnetic fields. MONITORING: State-of-the-art monitoring is also attainable for high-risk patients, including invasive pressure measurement. Since wiring without special filters may not cross the HF shield of the examination room, hydraulic and pneumatic systems are used (blood pressure by oscillometry, airway monitoring by side-stream spirometry). Optical fibers are used for pulse oximetry. A telemetric EKG is usually provided by the MRT manufacturer. Because oscilloscopes are distorted by the magnetic field, the monitors are placed outside the examination room. In addition, this eliminates the possibility of erasing the EPROMs contained in most monitors. PERSONNEL: With the setup described, the presence of a second anesthetist within the examination room is superfluous. A second anesthesia team can shorten the time lag between examinations by overlapping induction if a separate anesthesia induction and emergence room is provided. CONCLUSION: The level of sedation required for MRI in newborn and infants can only be achieved safely and efficiently by general anesthesia performed by trained staff. Complete state-of-the-art anesthesia care can be delivered if appropriate instrumentation is used.

Anesthesia, General↗
PubMed1997

MR angiography of the supra-aortic arteries using a dedicated head and neck coil: image quality and assessment of stenoses.

Our purpose was to evaluate a dedicated head and neck coil for demonstration of supra-aortic arteries with optimised magnetic resonance angiography techniques. We performed 47 examinations with a 1.5-T system. We used coronal 3D fast imaging with steady precession (FISP), axial 3D tilted optimised nonsaturating excitation (TONE) and 2D fast low-angle shot (FLASH) for the carotid bifurcation, axial 3D TONE with or without magnetisation transfer (MT) for intracranial arteries, and axial 3D FISP or TONE for the aortic arch. Evaluation included visual assessment of image quality and grading of stenoses near the carotid bifurcation; digital subtraction angiography was used as the reference method. Axial 3D TONE gave superior image quality at the carotid bifurcation, MT-TONE intracranially, and 3D FISP for the aortic arch vessels. Nevertheless, sensitivity and specificity for detection of significant stenoses were similar with coronal 3D FISP (96.3%, 94.0%), axial 3D TONE (92.6%, 92.5%) and axial 2D FLASH (96.3%, 86.6%). Image quality at the aortic arch needs further improvement.

Aged↗
PubMed1997

Fast spin-echo (FSE) and gradient- and spin-echo (GRASE) in fast MRI of the pelvis.

In this prospective study two different T2-weighted fast spin-echo (FSE) sequences and a gradient- and spin-echo (GRASE) sequence were compared in 20 consecutive patients undergoing clinical pelvic MR examinations. A GRASE and two FSE sequences were applied, whereby the FSE sequences differed from each other by altered echo spacings (15.0 and 22.5 ms) and T2 contrast. Quantitative image analysis included ROI evaluation of different S/N and C/N values. Visual image analysis was performed by two independent readers using a standardized score sheet for anatomic and pathologic findings. Overall image quality was significantly better in both FSE sequences. GRASE and FSE22.5 were superior in delineation of most of anatomic and pathologic structures due to intermediate to hypointense contrast behavior of pelvic fat compared to FSE15.0 in which fat was bright. Therefore, FSE15.0 was optimal for low intensity lesions. Short acquisition times of FSE and GRASE sequences allow application of two different techniques-fat hypointense respectively bright-for excellent lesion visualisation. This study demonstrates the usefulness of contrast manipulation in fast T2-weighted MRI techniques without special techniques, such as fat saturation.

Adipose Tissue↗
PubMed1997

Pigmented peripheral nerve sheath tumor of the oral cavity with expression of AP-2 beta and c-RET: a case report.

Pigmented peripheral nerve sheath tumor of the oral cavity is a rare lesion and may be difficult to distinguish clinically from true melanocytic tumors. We report a case of pigmented peripheral nerve sheath tumor with a high degree of melanocytic differentiation and describe its histologic and ultrastructural features. Immunohistochemistry and polymerase chain reaction findings support the neural crest origin of the tumor. The clinical course of our case indicates that local recurrence may be a significant problem in pigmented peripheral nerve sheath tumor.

Adult↗
PubMed1997

Cerebral abnormalities in patients with cirrhosis detected by proton magnetic resonance spectroscopy and magnetic resonance imaging.

Hepatic encephalopathy is a common problem in cirrhosis. The pathogenesis of this complication of advanced liver disease still remains unclear. Magnetic resonance spectroscopy was used to assess prospectively cerebral metabolism in 51 patients with histologically proven cirrhosis (Child-Pugh classes A, B, and C, 18, 18, and 15, respectively) and 36 healthy volunteers. According to the results of psychometric tests, overt hepatic encephalopathy, subclinical encephalopathy, and no encephalopathy were found in 14, 21, and 16 patients, respectively. Myoinositol/creatine ratios in gray (.36 +/- .17) and white (.35 +/- .22) matter voxel were reduced significantly (P < .0001) in cirrhotic patients compared with healthy volunteers (gray matter, .51 +/- .11; white matter, .64 +/- .16). In addition, patients showed a significant reduction (P = .024) in white matter choline/creatine ratio (.77 +/- .27) compared with controls (.92 +/- .25), and glutamine/glutamate level was elevated in cirrhotic patients compared with controls (gray matter, P < .0001; white matter, P = .036). Changes in cerebral myoinositol and glutamine/glutamate levels correlated significantly with the severity of hepatic encephalopathy (P < .0001). However, these metabolic alterations were also detected in patients without hepatic encephalopathy (normal psychometric test results). N-acetyl aspartate/creatine ratios did not differ between patients and controls. Magnetic resonance imaging detected bright basal ganglia in 37 patients, which correlated significantly with portal-systemic shunting and elevation of glutamine/glutamate, but not with the degree of hepatic encephalopathy. In conclusion, magnetic resonance imaging and spectroscopy showed that alterations of cerebral metabolism are common in patients with cirrhosis, even without evidence of clinical or subclinical hepatic encephalopathy.

Adult↗
PubMed1997

[Artifacts in MR imaging of the temporomandibular joint caused by dental alloys: a phantom model study at T1.5].

PURPOSE: The influence of dental alloys on MRI of the temporomandibular joint was studied using a phantom model for this joint. METHODS: At 1,5 T, 15 dental alloys and 14 of their most important components were investigated acquiring sagittal (FOV: 150 mm) and transverse (FOV: 250 mm) T1-weighted SE images. In 11 cases, T1- and T2*-weighted FLASH images were measured additionally. The artifacts were assessed qualitatively as well as quantitatively, and the samples were subdivided into four artifact categories. RESULTS: Ag, Cu, Ga, In, Tl, Sn, Zn, amalgam, the precious alloys, the Au-Pd and Ag-Pd alloys showed no artifacts (category I). Minimal artifacts below 10 mm on transverse images (category II) were found for Cr, Pd, Pt and for the Ni-Cr alloy. Mn and the remaining non-precious alloys induced artifacts up to 30 mm (category III). Significant artifacts-more than 30 mm-(category IV) were caused by Ni-Cr and 18/8 wires and by Co, Fe, and Ni. T2*-weighted FLASH proved to be more susceptible for artifacts than T1-weighted SE and FLASH techniques. CONCLUSIONS: In contrast to dental alloys for fixed prosthodontics, Ni-Cr- or 18/8 wires used for orthodontic bands can influence not only the image quality, but also the diagnostic reliability of MRI of the temporomandibular joint.

Artifacts↗
PubMed1997

Skeletal muscle alterations in patients with chronic heart failure.

AIMS: To investigate skeletal muscle in patients with chronic heart failure and controls, and relate skeletal muscle variables to functional class, exercise capacity, central haemodynamics, muscle strength and medical treatment. METHODS: Biopsy from the lateral vastus muscle was obtained in 43 patients and 20 controls. Right sided heart catheterization was performed in 19 patients and maximal exercise testing in 26 patients. In nine patients muscle strength was measured. Patients had higher lactate levels, higher lactate dehydrogenase activity, and lower oxidative enzymes activity than controls. In patients, the percentage of type I fibres and capillarization were decreased while the percentage of type II B fibres were increased. Lactate dehydrogenase activity correlated with exercise capacity, muscle strength and right atrial pressure. Digoxin-treated patients had significantly lower oxidative enzyme activity than patients without digoxin treatment. CONCLUSION: Patients with chronic heart failure have several skeletal muscle abnormalities. Central haemodynamics and medical treatment may, in addition to inactivity, be important in skeletal muscle changes.

Adenosine Triphosphate↗
PubMed1997

MRI of inner ear anatomy using 3D MP-RAGE and 3D CISS sequences.

The aim of this study was to compare contrast enhanced 3D MP-RAGE (magnetization prepared rapid gradient echo), unenhanced 3D MP-RAGE and 3D CISS (constructive interference in steady state) in the evaluation of anatomical detail of the inner ear and facial nerve. 60 persons with no abnormalities and no or non-specific symptoms were examined with MRI. All examinations were performed using a 1.5 T MR unit. The detectability of anatomical details was evaluated by agreement of three radiologists. Statistical evaluation of the results was achieved by the two-tailed Wilcoxon's test. In 86-95% of the cases, 3D CISS resulted in excellent visibility of the basal and second turn and apex of the cochlea, the vestibule and semicircular canals, as well as the nerves within the internal auditory canal. There was a significantly better visualization with CISS than with MP-RAGE. Detectability of the extrameatal facial nerve was best using contrast enhanced 3D MP-RAGE in 91-96% of the cases (labyrinthine segment 96.7%; geniculate ganglion 95%; tympanic segment 91.7%; vertical segment 95%). The detection of the meatal seventh nerve was best using CISS, whilst unenhanced MP-RAGE gave significantly better results than contrast enhanced MP-RAGE. These results suggest that unenhanced and contrast enhanced 3D MP-RAGE and 3D CISS sequences are complementary and not alternative MRI techniques. Both T1 and T2 weighted 3D MR imaging of the temporal bone is of advantage when compared with 2D MR sequences due to improved contrast, geometrical resolution and the possibility of adequate reconstruction of anatomical structures.

Adolescent↗
PubMed1997

MRI of inner ear and facial nerve pathology using 3D MP-RAGE and 3D CISS sequences.

The aim of this study was to evaluate 3D CISS, unenhanced 3D MP-RAGE and contrast enhanced 3D MP-RAGE for the diagnosis of neoplastic, vascular and inflammatory lesions of the cerebellopontine angle, the inner auditory canal, the labyrinth and the facial nerve 42 MR examinations were performed on a total of 38 patients (25 males, 13 females; aged 1-77 years, mean age 43 +/- 20 years) using a 1.5 T MR unit. A T2* weighted 3D CISS sequence (TR 14.65 ms, TE 21 ms, flip angle 65 degrees, voxel size 0.7 x 0.7 x 0.7 mm3) and a T1 weighted 3D MP-RAGE sequence (TR 12.5 ms, TE 5 ms, T1 300 ms, flip angle 15 degrees, voxel size 1.0 x 0.9 x 0.9 mm3) with and without contrast medium (gadolinium-DTPA, 0.1 mmol kg-1 body weight) were used. Results of contrast enhanced 3D MP-RAGE-pathological enhancement was found in the following lesions: schwannomas of the cerebellopontine angle (CPA) and the internal auditory canal (IAC), 4; schwannomas of the IAC, 7 and labyrinthine tumours, 3; posterior fossa lymphoma, 1; meatal meningioma, 1; acute labyrinthitis, 15 and neuritis of the seventh cranial nerve, 10. Results of 3D CISS-filling defects were found with the following lesions: schwannomas of the CPA, the IAC or labyrinth, 14; lymphoma, 1; meningioma, 1; labyrinthine fibrosis, 13 and scar in the IAC, 4. These results suggest that unenhanced and contrast enhanced 3D MP-RAGE and 3D CISS are complementary MR imaging modalities. T1 weighted 3D MP-RAGE is preferred to T1 weighted 2D (turbo) spin echo sequences because of the multiplanar reconstruction possibilities of 3D sequences, which are very useful in the case of the inner ear and facial nerve.

Acute Disease↗
PubMed1997

Comparison of spin-echo MR pulse sequences for imaging of the brain.

PURPOSE: To determine the value of the gradient- and spin-echo (GRASE) technique as compared with the fast spin-echo and conventional spin-echo techniques in MR imaging of the brain. METHODS: Sixty-six patients with ischemic and neoplastic brain lesions were examined with T2-weighted spin-echo, fast spin-echo, and GRASE sequences. Three independent observers evaluated the contrast characteristics of anatomic and pathologic structures and of artifacts. Quantitative image analysis included region-of-interest measurements of anatomic structures and lesions. RESULTS: The contrast of anatomic structures was superior in images obtained with conventional and fast spin-echo techniques as compared with those obtained with the GRASE technique. Extended lesions, such as tumors and territorial infarcts, were identified equally with all techniques. For delineation of small ischemic lesions, GRASE was slightly inferior to fast and conventional spin-echo sequences. Flow artifacts were considerably reduced with fast spin-echo and GRASE sequences. Chemical-shift artifacts were significantly reduced, but ringing artifacts were more pronounced with GRASE. CONCLUSION: Fast spin-echo remains the standard technique in MR imaging of the brain. However, GRASE might be useful in special cases, such as with uncooperative patients whose conventional or fast spin-echo images show severe motion artifacts.

Adult↗
PubMed1997

Combination neurohormonal blockade with ACE inhibitors, angiotensin II antagonists and beta-blockers in patients with congestive heart failure: design of the Randomized Evaluation of Strategies for Left Ventricular Dysfunction (RESOLVD) Pilot Study.

BACKGROUND: The Randomized Evaluation of Strategies for Left Ventricular Dysfunction (RESOLVD) Pilot Study is a trial of combination neurohormonal blockade using an angiotensin II antagonist (candesartan), an angiotensin-converting enzyme inhibitor (enalapril) and a beta-blocker (metoprolol) in patients with congestive heart failure (CHF). OBJECTIVES: Primary objectives of stage I are to determine the efficacy (via the 6 min walk test) and safety of candesartan alone, and in combination with enalapril, versus enalapril alone. Secondary objectives are to determine the effect of the above combinations on neurohormones, ventricular function, quality of life and symptoms. Stage II objectives are similar, evaluating the effect of the addition of metoprolol or placebo to the above medication(s). DESIGN: Randomized, two-stage trial consisting of a three-way comparison (stage I), followed by a 3 x 2 partial factorial design (stage II). SETTING: Sixty out-patient clinics in five countries. PATIENTS: Patients with symptoms of CHF (New York Heart Association functional classes II to IV), ejection fraction less than 40% and 6 min walk distance of 500 m or less. INTERVENTIONS: In stage I, 770 patients are randomized to receive candesartan alone, enalapril alone, or candesartan plus enalapril. After five months (end of stage I), patients are assessed for eligibility to be randomized in stage II. Those who are not candidates for randomization to beta-blocker or placebo are followed on their stage I medications until the end of the study. In stage II, patients are randomized to receive metoprolol or placebo for a further six months in addition to their stage I medications. Endpoints are measured at baseline, end of stage I (week 20) and end of stage II (week 46). STUDY STATUS: The study has recently completed follow-up in both stages. The findings from this study will be used to design a large scale mortality study that will help further define the role of neurohormonal blockade in patients with CHF.

Adrenergic beta-Antagonists↗
PubMed1996

A T1-weighted rapid three-dimensional gradient-echo technique (MP-RAGE) in preoperative MRI of intracranial tumours.

Our purpose was to determine the value of a T1-weighted rapid three-dimensional gradient-echo technique in preoperative MRI of brain tumours. We examined 30 patients with intracranial tumours who underwent neurosurgery, using T1-weighted magnetisation-prepared rapid gradient-echo (MP-RAGE) and axial T1-weighted spin-echo (SE) sequences, both before and after contrast medium (Gd-DTPA). Signal and contrast behaviour of anatomical and pathological structures were assessed with regions-of-interest (ROI) and visual inspection. Imaging results were compared with operative results. In 5 cases tumours and anatomical structures were segmented in MP-RAGE data sets. The MP-RAGE sequence considerably improved delineation of grey and white matter and small anatomical structures (vessels, cranial nerves), and significantly reduced flow artefacts. Contrast behaviour of tumours was similar with both techniques. Correlation of imaging with the operative results confirmed the reliability of the MP-RAGE sequence. Segmentation of MP-RAGE data sets allows three-dimensional display, which enables one to document the relevant information on a few images in selected cases.

Adolescent↗
PubMed1996

Diagnostic potential of pseudo-dynamic MRI (CINE mode) for evaluation of internal derangement of the TMJ.

In addition to the patient's history and a thorough clinical investigation, magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) has been introduced to complete the findings for the diagnosis of internal derangement of the TMJ. However, 'dynamic information' is desirable to help us to understand the mechanism of internal derangement. This information is given for example by electronic axiography recording systems. The lack of any ability to assess joint function dynamically in MRI is a point of criticism. Using a computer-driven pseudodynamic MRI system (CINE mode) 'dynamic information' should be now available. In this investigation 21 patients with TMJ disorders were examined using both conventional static MRI and CINE mode. For the diagnosis of an anterior displaced disc with or without reduction in 18 cases (86%) it was only necessary to consider two static MRIs: a closed mouth position and a maximal open mouth position. Comparison showed there was no advantage in using CINE mode. Contrast and resolution of the static MRIs were shown to be better and so additional findings such as joint effusion and disc deformation could be diagnosed on static MRIs with greater certainty. Only in three (14%) cases was the dynamic information from CINE mode useful for the diagnosis of the displacement of the disc.

Adult↗
PubMed1996

Skeletal muscle changes in patients with chronic heart failure before and after treatment with enalapril.

To evaluate if enalapril treatment can influence skeletal muscle metabolism and histology we investigated 26 patients with congestive heart failure and 20 normal subjects. The patients were treated with enalapril for 3 months in addition to diuretics and digitalis. Biopsies from the lateral vastus muscle were taken before and after treatment. Citrate synthetase, 3-hydroxyacyl-CoA dehydrogenase and phosphorylase activities were significantly decreased in the patients compared with controls. The number of capillaries per fibre and the number of capillaries surrounding each fibre were significantly decreased among patients. After 3 months of enalapril treatment functional class improved significantly. The lactate dehydrogenase activity increased whereas the oxidative enzymes did not change significantly. The type I, II and II A fibre areas increased significantly after enalapril treatment. We conclude that patients with chronic heart failure have decreased activity of oxidative enzymes and of phosphorylase in skeletal muscle. They also have decreased capillarization in skeletal muscle. These changes were not influenced by enalapril treatment. The increase in muscle fibre area seen after enalapril treatment could be due to increased physical activity. The cause of increased muscle lactate dehydrogenase activity after enalapril treatment needs further investigation.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1996

Protein-DNA interactions at the major and minor promoters of the divergently transcribed dhfr and rep3 genes during the Chinese hamster ovary cell cycle.

In mammals, two TATA-less bidirectional promoters regulate expression of the divergently transcribed dihydrofolate reductase (dhfr) and rep3 genes. In CHOC 400 cells, dhfr mRNA levels increase about fourfold during the G1-to-S phase transition of the cell cycle, whereas the levels of rep3 transcripts vary less than twofold during this time. To assess the role of DNA-binding proteins in transcriptional regulation of the dhfr and rep3 genes, the major and minor dhfr-rep3 promoter regions were analyzed by high-resolution genomic footprinting during the cell cycle. At the major dhfr promoter, prominent DNase I footprints over four upstream Sp1 binding sites did not vary throughout G1 and entry into the S phase. Genomic footprinting revealed that a protein is constitutively bound to the overlapping E2F sites throughout the G1-to-S phase transition, an interaction that is most evident on the transcribed template strand. On the nontranscribed strand, multiple changes in the DNase I cleavage pattern are observed during transit through G1 and entry into the S phase. By using gel mobility shift assays and a series of sequence-specific probes, two different species of E2F were shown to interact with the dhfr promoter during the cell cycle. The DNA binding activity of one E2F species, which preferentially recognizes the sequence TTTGGCGC, did not vary significantly during the cell cycle. The DNA binding activity of the second E2F species, which preferentially recognizes the sequence TTTCGCGC, increased during the G1-to-S phase transition. Together, these results indicate that Sp1 and the species of E2F that binds TTTGGCGC participate in the formation of a basal transcription complex, while the species of E2F that binds TTTCGCGC regulates dhfr gene expression during the G1-to-S phase transition. At the minor promoter, DNase I footprints at a consensus c-Myc binding site and three Sp1 binding sites showed little variation during the G1-to-S phase transition. In addition to protein binding at sequences known to be involved in the regulation of transcription, genomic footprinting of the entire promoter region also showed that a protein factor is constitutively bound to the first intron of the rep3 gene.

Animals↗