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Biomedical subjects

M Leinung

Publications and source records attributed to M Leinung.

7 recordsLinked to original sources
PubMed2003

[Navigation-supported surgery in the head and neck region].

Few of the pioneering manufacturers who attempted to develop navigation systems have been able to establish themselves within the market long-term. The same applies to the technological basis of these systems which aid intraoperative anatomical orientation. The first few systems registered the mechanical displacement of the navigational instrument's axes. Optoelectronic and electromagnetic methods are now prevalent. In contrast to electromagnetic systems, the "line of sight" between the camera system, the reference markers placed on the patient's head and the navigation instruments must remain unobstructed during the navigation process when using electrooptical navigation systems. Whereas, in the past, only preoperative CT scans were used for navigation, the integration of MRI and sonography--whose images can now be fused with each other and with those provided by other intraoperative imaging techniques such as fluoroscopy and endosonography--has become increasingly popular. Navigation systems require input of information about spatial conditions. This is carried out via procedures of registration and referencing, by means of which the relative position of reference markers at the head of the patient is correlated with the image data. The equipment is calibrated in the same way. Headsets, headbands and bone-anchored adapters are available for the fixation of the markers in the patient's head. Whereas the use of a headband or headset requires considerably less time, bone-anchored referencing increases the precision of the navigation system. The surgeon must be able to manage the different methods. In order to reduce the time required for preoperative preparation and to enhance the handling of the navigation processor for the surgeon, it is essential to have a clear menu. The surgeon is able to plan the steps involved in the surgery using the processor, define the access to the surgical site and control the surgery intraoperatively. Preoperative segmentation of functionally and clinically relevant structures enables minimally invasive surgery to be carried out, such as procedures with the aim of acquiring biopsy tissue and the search for foreign bodies. Following the technical development of the systems, the manufacturers are endeavouring to simplify their handling in close coordination with the users. The next step has to be the clinical evaluation of the navigation systems in accordance with the EBM standard, in order to establish this assistive method as routine clinical practice while applying meaningful medical criteria.

Endosonography↗
PubMed1995

Clinical and analytical evaluation of an immunoradiometric assay for corticotropin.

We evaluated a new IRMA developed commercially for the measurement of corticotropin (ACTH) in human plasma. The assay involves purified polyclonal goat capture antibodies specific for ACTH 26-39 and an 125I-labeled monoclonal signal antibody specific for ACTH 1-17. CVs for intraassay and total precision at ACTH concentrations between 9 and 801 ng/L ranged from 2.5% to 4.7% and from 3.3% to 9.3%, respectively, with an assay detection limit of 1.7 ng/L. The reference interval determined for adults with the new method (16-52 ng/L) differed significantly (P < 0.05) from that for an established ACTH IRMA (9-54 ng/L). Method comparison with clinical samples (n = 179) revealed a correlation coefficient of 0.970 and a best-fit equation of y (new IRMA) = (1.011 +/- 0.019)x + (4.17 +/- 3.31) with Sylx = 40.2. Both methods showed equivalent clinical sensitivity in evaluating Cushing disease, adrenal tumors, ectopic ACTH-producing tumors, hypopituitarism, steroid suppression, surgical adrenalectomy, Nelson syndrome, Addison disease, and corticotropin-releasing hormone stimulation. We conclude that the new IRMA is technically simple to perform and provides a specific and sensitive method for evaluating of adrenocortical function.

Adrenal Cortex Diseases↗
PubMed1994

The clinical evaluation of patients with subclinical hyperthyroidism and free triiodothyronine (free T3) toxicosis.

PURPOSE: To develop a strategy to identify cases of endogenous subclinical hyperthyroidism and free triiodothyronine (free T3) thyrotoxicosis in otherwise healthy ambulatory patients. PATIENTS AND METHODS: In a retrospective study we reviewed the records of ambulatory patients who had thyroid stimulating hormone (TSH) levels determined between October 1, 1991 and August 31, 1992. Each patient also had a simultaneous free thyroxine (free T4) measurement. Patients were excluded from consideration if they had active, concurrent non-thyroidal illness, psychiatric disease, known hypothalamic/pituitary lesions, were under treatment for hyper- or hypothyroidism, were on drugs known to affect TSH levels, or were pregnant. Patients without exclusions were diagnosed with free T3 toxicosis if they had: (1) a markedly subnormal TSH level (less than or equal to 0.1 mU/L), (2) a normal free T4, (3) a normal total T3, (4) evidence of a primary thyroid abnormality (e.g., autonomous function on a thyroid scan), and (5) an elevated free T3 level by tracer equilibrium dialysis. Patients meeting conditions 1-4, but with normal free T3 levels, were considered to have subclinical hyperthyroidism. RESULTS: One thousand twenty-five patients had TSH and simultaneous free T4 determinations, and 148 of these had markedly subnormal TSH but normal free T4 levels. Three patients met the criteria for free T3 toxicosis and three had subclinical hyperthyroidism. All six patients had either multinodular glands or a single nodule on thyroid exam. Four patients were treated with radioactive iodine or surgery, resulting in reversal of the TSH suppression in three cases. CONCLUSION: Apparently healthy ambulatory patients with subnormal TSH levels should be worked up with measurements of free T4 and total T3. If these are normal, a T3 level (by tracer equilibrium dialysis) be obtained to distinguish subclinical hyperthyroidism from overt free T3 toxicosis. A thyroid scan and radioiodine uptake measurement can be obtained to substantiate the diagnosis. Some patients with these conditions will benefit from treatment.

Adult↗
PubMedDate not supplied

Glucocorticoidlike activity of megestrol. A summary of Food and Drug Administration experience and a review of the literature.

Sporadic single case reports linking glucocorticoidlike activity to megestrol acetate have been reported in the literature. These findings have important implications for patient care. Adverse drug experience reports to the US Food and Drug Administration from 1984 through 1996 and a MEDLINE search of the literature from 1984 through 1996 provided the case reports. Five cases of Cushing syndrome, 12 cases of new-onset diabetes, and 16 cases of adrenal insufficiency were identified in association with megestrol therapy. Twelve cases in which preexisting diabetes was exacerbated and 17 cases of possible adrenal insufficiency were identified. Therapy with megestrol can result in clinical manifestations of glucocorticoidlike activity, including Cushing syndrome, diabetes, and adrenal insufficiency. Clinicians need to be aware of this association as these complications can be life-threatening if not recognized.

Adrenal Insufficiency↗