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Biomedical subjects

H Hundeshagen

Publications and source records attributed to H Hundeshagen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Combined spatial and temporal imaging of brain activity during visual selective attention in humans.

Visual-spatial attention is an essential brain function that enables us to select and preferentially process high priority information in the visual fields. Several brain areas have been shown to participate in the control of spatial attention in humans, but little is known about the underlying selection mechanisms. Non-invasive scalp recordings of event-related potentials (e.r.ps) in humans have shown that attended visual stimuli are preferentially selected as early as 80-90 ms after stimulus onset, but current e.r.p. methods do not permit a precise localization of the participating cortical areas. In this study we combined neuroimaging (positron emission tomography) with e.r.p. recording in order to describe both the cortical anatomy and time course of attentional selection processes. Together these methods showed that visual inputs from attended locations receive enhanced processing in the extrastriate cortex (fusiform gyrus) at 80-130 ms after stimulus onset. These findings reinforce early selection models of attention.

Attention↗
PubMed1994

Bone scintigraphy in the evaluation of bone grafts used for mandibular reconstruction.

Bone scintigraphy was applied in the follow-up of 24 patients who received bone grafts for reconstruction of the mandible after partial resection. Semiquantitative assessment of the grafts was done with a six-grade scoring system, based on comparison of tracer uptake in the graft and in the calvarium (as an internal control). Sixty-nine bone scans were evaluated. Late planar imaging was carried out in all cases, and single-photon emission tomography (SPET) was performed additionally in 34 of these cases. Complications were observed in four grafts. They occurred less frequently in revascularized grafts than in non-revascularized grafts. Planar scintigrams performed within 14 days after reconstruction showed a significantly higher tracer uptake in grafts with an uncomplicated further course than in those which developed complications. Follow-up scintigrams after 1 and 3 months revealed a significant increase in tracer uptake in grafts with an uncomplicated course. This was not apparent in grafts which developed complications. The tracer uptake was estimated to be higher on the basis of the SPET scans as compared with the planar scintigrams. It is concluded that bone scintigraphy is of prognostic value in the evaluation of bone grafts used for mandibular reconstruction. SPET seems to be more sensitive than planar imaging for the assessment of graft viability.

Bone Transplantation↗
PubMed1994

[Value of magnetic resonance tomography in diagnosis of tethered cord syndrome in children].

The tethered cord syndrome is considered a trouble complex that is caused by fixation of the spinal cord by intra- or extradural components. Clinically it is characterized by motor and sensory dysfunction of the lower extremities, muscle atrophy, decreased or hyperactive reflexes, urinary and bowel incontinence, spastic gait, or orthopedic deformities. Traditionally, positive-contrast myelography has been the diagnostic procedure of choice, often supported by CT (post myelo-CT). With the improvement of surface-coil technology, MR imaging has become a useful diagnostic tool for the assessment of the spinal cord and canal without ionizing radiation. MR examinations of 80 patients with the clinical diagnosis of tethered spinal cord were reviewed retrospectively in order to define normal anatomy and pathological findings as well as to establish MR strategies in the diagnosis of tethered cord syndrome in children. In order to evaluate intraspinal lipomas, the width of the spinal canal and dysraphic lesions, T1-weighed sagittal and transverse images are useful. In case of deformities of the spinal column the corona slice orientation should be used. The filum terminale and its thickness is best seen in T2-weighed transverse and sagittal images. The extension of fat within the spinal canal over more then 6 vertebral bodies and more then 1.2 cm width could be an indication of a lipomatous malformation in the sacral spinal canal.

Adolescent↗
PubMed1994

[Quality control of fractionated port scintigraphy in patients with head and neck neoplasms].

The purpose of this study was to evaluate the precision of a technique for shunt measurement and to quantify its relevant influencing factors. Therefore, 10 patients underwent firstly an intraarterial injection of 100 MBq 99mTc-MAA and secondly a fractionated intravenous injection of 4 x 10 MBq 99mTc-MAA. Calculations of the shunt volumina were done with Wheeler's algorithm. In addition the relative shunt volumina for all applications were computed and corrected for (a) tracer retention, (b) biological degradation, (c) physical decay, (d) remaining activities and (e) the combination of (a)-(d). The coefficient of variation was 9.4%. The influence of (a), (b) and (d) was significant and that of (c) not significant. If all influencing factors were ignored (e), no significant differences could be seen, compared to the fully corrected results. Therefore, fractionated shunt scintigraphy is a simple and rapid technique for precisely determining relative shunt volumina in patients under local chemotherapy.

Adult↗
PubMed1994

123I-IBZM SPECT: reconstruction methodology and results in parkinsonism and dystonia.

In 58 patients with Parkinsonism or dystonia striatal dopamine D2 receptors were investigated using 123I-iodobenzamide (123I-IBZM) single-photon emission computed tomography (SPECT). The influence of SPECT reconstruction methodology on semiquantification and the clinical value of 123I-IBZM SPECT were evaluated. Delineation of the striatal uptake and striatum/frontal cortex (ST/FC) ratios were improved by the use of compensation procedures for scatter and attenuation as well as the choice of an adequate filter. Satisfactory results were achieved using a Metz prefilter with a comparatively high order number (i.e. high cut-off and low suppression of higher frequencies via roll-off). Regarding clinical diagnoses it was not possible to differentiate between advanced idiopathic Parkinson's disease (IP) and Parkinsonism of other aetiology (OP) on the basis of 123I-IBZM SPECT. But patients with IP and favourable response to L-Dopa showed significantly higher ST/FC ratios than those with fluctuating response. In patients with dystonia ST/FC ratios were significantly higher compared to patients with IP or OP.

Adult↗
PubMed1994

[Scintigraphy using 131I in oxyphilic carcinomas of the thyroid gland].

The aim of the study was to ascertain the role of 131I scintigraphy (RIS) in the follow-up of oxyphilic thyroid carcinomas (OTC). It is discussed that metastases (M) and local recurrencies (LR) are incapable of accumulating 131I sufficiently; therefore, the usual strategy of RIS cannot be used for follow-up. The re-examination of 91 patients suffering from OTC showed that 10/20 patients with M/LR did have a positive uptake of 131I, which could be used for therapy in 8 patients. An ablation of M using high-dose 131I therapy could be demonstrated in three younger patients who had cervical lymph node M 3 months after thyroidectomy as an early manifestation of their disease. In three patients RIS first led to the metastatic site. The clinical course of patients with distant M that developed at a later stage was unfavourable, even though they did accumulate 131I. Patients with positive uptake of 131I in M/LR were significantly younger (55a) than patients who had no uptake (67a) and belonged more often to stage I and II of UICC, namely 7/10 vs 2/10. RIS should be used especially in an early interval after thyroidectomy and individually for follow-up: as a diagnostic method and therapeutic instrument.

Adult↗
PubMed1993

Insulin resistance in liver cirrhosis. Positron-emission tomography scan analysis of skeletal muscle glucose metabolism.

BACKGROUND: Insulin resistance and glucose intolerance are a major feature of patients with liver cirrhosis. However, site and mechanism of insulin resistance in cirrhosis are unknown. We investigated insulin-induced glucose metabolism of skeletal muscle by positron-emission tomography to identify possible defects of muscle glucose metabolism in these patients. METHODS: Whole body glucose disposal and oxidation were determined by the combined use of the euglycemic-hyperinsulinemic clamp technique (insulin infusion rate: 1 mU/kg body wt per min) and indirect calorimetry in seven patients with biopsy-proven liver cirrhosis (Child: 1A, 5B, and 1C) and five healthy volunteers. Muscle glucose uptake of the thighs was measured simultaneously by dynamic [18F]fluorodeoxyglucose positron-emission tomography scan. RESULTS: Both whole body and nonoxidative glucose disposal were significantly reduced in patients with liver cirrhosis (by 48%, P < 0.001, and 79%, P < 0.0001, respectively), whereas glucose oxidation and the increase in plasma lactate were normal. Concomitantly, skeletal muscle glucose uptake was reduced by 69% in liver cirrhosis (P < 0.003) and explained 55 or 92% of whole body glucose disposal in cirrhotics and controls, respectively. Analysis of kinetic constants using a three-compartment model further indicated reduced glucose transport (P < 0.05) but unchanged phosphorylation of glucose in patients with liver cirrhosis. CONCLUSIONS: Patients with liver cirrhosis show significant insulin resistance that is characterized by both decreased glucose transport and decreased nonoxidative glucose metabolism in skeletal muscle.

Adult↗
PubMed1993

Accurate local blood flow measurements with dynamic PET: fast determination of input function delay and dispersion by multilinear minimization.

Accurate determination of local blood flow in tissue using the Kety-Schmidt one-compartment model for freely diffusible tracers requires knowledge of the true arterial input function in tissue. Because measured input functions are usually delayed and dispersed with respect to true influx, a correction of the experimental input function is necessary. We describe a technique that uses a fast multilinear least-squares minimization procedure to determine simultaneously the dispersion, the blood flow and the partition coefficient as a function of delay. In this approach, a few multilinear fits are sufficient to determine the complete set of parameters necessary to describe the data. Because of the high speed of the procedure, dispersion effects may be taken into account on a pixel-by-pixel basis in calculating parametric images of blood flow and partition coefficient. The described procedure has been used at our institute for about 1 yr in more than 160 investigations and has proven well suited for routine use in a clinical environment.

Blood Flow Velocity↗
PubMed1992

Limitations of clearance determination using the single sample distribution volume method. An error analysis on the basis of compartment models.

To investigate the error possibly contained in the single sample distribution volume method for the determination of renal clearance, a mathematical model was applied to describe the effect of changes in distribution volume, clearance, intravascular space, intracompartmental exchange and the time point of blood sampling. The method was found to be valid only under well-defined circumstances (Topt = 45 +/- 5 min, Cl = 390 +/- 50 ml/min, Vd = 16.7 +/- 4 l, alpha = 0.05.V1 ml/min, V1/Vd = 0.5 +/- 0.05) as shown in sample calculations. Two-compartment model-based error calculations demonstrate that this technique implies at best an uncertainty of +/- 10% or more. Whilst it can be used preferably in healthy, normal-weight adults, it is not applicable, without error, under all other circumstances.

Humans↗
PubMed1992

[Trans-sternal cervico-mediastinal primary tumor resection and lymphadenectomy in thyroid gland cancer].

Thyroid carcinoma may invade the mediastinum by direct extension of the primary tumor or metastases to the paratracheal or retroclavicular-parajugular lymph nodes. From 1975 to 1991 in 47 out of 622 thyroid cancer patients (7.6%) [14 papillary (PTC), 5 follicular (FTC), 16 medullary (MTC) and 12 undifferentiated carcinoma (UTC)] transsternal tumor resection has been performed. Four patients (UTC three, MTC one) deceased 7, 8, 35, and 41 days after resection of the primary tumor due to cardiac or tumor disease, and in one patient because of acute arteriotracheal haemorrhage after external irradiation; no patient deceased after transsternal resection as a result of cervicomediastinal lymphadenectomy. At the time of primary operation 80% of patients showed an advanced tumor stage (greater than pT3). In 34% of patients (PTC 64%, FTC 40%, MTC 13%, UTC 25%) no tumor recurrence was observed neither by imaging nor by biochemical methods. In 18 patients a transsternal microdissection of all four cervicomediastinal lymph node compartments has been performed. Histological analyses of excised and tumor involved lymph nodes revealed in 9 patients unilateral cervical and mediastinal and in 9 patients bilateral cervical and mediastinal lymph node metastases. In the case of unilateral cervicomediastinal lymph node metastases 2 out of 2 patients with papillary and 2 out of 6 patients with medullary thyroid carcinoma could be cured surgically. In the case of bilateral cervicomediastinal lymph node metastases 3 out of 4 patients with papillary thyroid carcinoma, but no other thyroid cancer patient were free of disease. In conclusion, main indications for transsternal cervicomediastinal resection in thyroid carcinoma are (1) primary tumors extending to the upper mediastinum, but without lymph node metastases, and (2) thyroid carcinomas with unilateral cervicomediastinal lymph node metastases. In the case of bilateral cervicomediastinal lymph node metastases probable only papillary thyroid carcinomas are supposed to be curable by transsternal multicompartmentectomy.

Adenocarcinoma↗
PubMed1992

[The clinical course of oxyphilic carcinoma of the thyroid].

In a total of 1665 patients with malignant thyroid neoplasms 90 oxyphilic thyroid carcinomas (OTC) were found of whom 55 could be re-examined and newly classified. Morphological and clinical parameters influencing the clinical course were determined. During a mean follow-up period of 6.5 y metastases or local recurrent disease occurred in 12 patients (24%). Apart from 3 early manifestations of metastases, 9 patients developed recurrent disease within, on average, 4.7 y after thyroidectomy: local lymph node metastases and local recurrences occurred within an average of 5.4 y, distant metastases after only 2.7 y. Thyroglobulin proved to be reliable for follow-up with a sensitivity of 88% on levothyroxine and 75% on endogenous TSH-stimulation (specificity: 98%). The frequency of metastases and local recurrences correlated with age at the time of tumor diagnosis, the degree of invasiveness and the local tumor extension (pT4 vs. pT1-3), whereas other factors such as the absolute diameter of the tumor or patient's sex had no influence on the clinical course. The survival probability for 5 and 10 years was 95 and 75%, respectively. All OTC patients should be examined regularly at least once a year by cervical sonography and thyroglobulin measurement. Because 18% recurrences occurred within 4.7 y such examinations should be repeated beyond year 5 after thyroidectomy.

Aged↗
PubMed1992

[Mucociliary clearance in childhood].

AIM OF THE STUDY: A new, nearly monodisperse human serum albumin particle produced by air-pressure-nebulization was inhaled by children and lung-transplant patients. METHOD: After inhalation of the particles obtained with an air-pressure nebulizer, the initial deposition pattern showed a marked tracheobronchial deposition which could be reproducibly obtained without a special breathing technique, the alveolar deposition being not higher than 10%. With the use of 99mTc, the radiation exposure is limited to a level which is low enough for children, but images can be taken up to 24 hrs later. Further parameters for in vivo characterization of the mucociliary function are the 24 h retention pattern and the velocity of particle motion in the trachea. RESULTS: Within the first 45 minutes, the global clearance rate was 51% in healthy children, which is rather high in comparison with the literature, most likely due to size of particles and the selection of patients with a mean age of 10.7 years. In ciliary dysfunction, the initial clearance rate was 16% and 46% within 24 h. CONCLUSIONS: With simplification of the preparation, application, and examination technique, this method is to be used in children, so that a wider use can be anticipated. The normally fast initial elimination of particles allows quick differentiation of normal and impaired ciliary function.

Adolescent↗
PubMed1991

[The effect of magnetic resonance treatment on chicken embryos].

Nuclear Magnetic Resonance (NMR) is of increasing diagnostic importance especially in human medicine. To evaluate possible side effects of this technology, embryonated chicken eggs were used as a model. Different fields (static magnetic field [1 oder 4 T], variable magnetic field [gradient] or high frequency field) were applied before the beginning and at the fifth day of incubation for different times (18.8, 37.6, 56 or 75.1 min, resp.). According to the criteria embryo-mortality, hatching-rate or vitality of the chickens, influences of the NMR-treatment were not observed.

Animals↗