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Biomedical subjects

L Geworski

Publications and source records attributed to L Geworski.

9 recordsLinked to original sources
PubMed2006

The use of radiolabelled human serum albumin and SPECT/MRI co-registration to study inflammation in the cavernous sinus of cluster headache patients.

A sterile inflammation in the cavernous sinus was hypothesized to underlie cluster headache (CH). Neurogenic inflammation is accompanied by the extravasation of plasma proteins in the surrounding tissue. We tested the hypothesis of an inflammatory process in the cavernous sinus in CH patients using 99mTc-human serum albumin (HSA) and single photon emission computed tomography (SPECT). Six patients with episodic CH were enrolled. After baseline imaging, CH attacks were induced by IV injection of nitroglycerin. The patients remained untreated for 20 min. A second SPECT was performed after successful treatment. Region of interest (ROI) analysis was performed on the basis of coregistered MRI/SPECT data. There was no statistical difference between the 99mTc-HSA uptake in the ipsilateral cavernous sinus before and after induction of an acute CH attack. There was no evidence for 99mTc-HSA extravasation in the cavernous sinus during the active episode as compared with the remission phase. Our results do not support the hypothesis of an inflammation in the cavernous sinus.

Adult↗
PubMed2006

[Radiation exposure in (90)Y-Zevalin therapy: results of a prospective multicentre trial].

UNLABELLED: AIM of this study was the assessment of the radiation exposure from preparation and application of (90)Y-Zevalin, the measurement of the dose rate at the patient, the exposure of family members as well as the determination of the activity concentration in urine of patients. METHODS: Overall data from 31 therapeutic administrations carried out in four institutions were evaluated. During preparation and application of (90)Y-Zevalin the finger exposures of radiochemists, technicians, and physicians were measured. The dose rate of the patient was measured immediately after radioimmunotherapy. In patients treated in a nuclear medicine therapy unit, urine was collected over a two day period and the corresponding activity was determined. Family members of outpatients were asked to wear a dosimeter over a seven day period. RESULTS: During the preparation we found a maximum skin dose of 6 mSv at the average, and during application of 3 mSv, respectively. After administration of (90)Y the dose rate was 0.4 +/- 0.1 microSv/h at 2 m distance. Urine measurements yielded a cumulated 24 h excretion of 3.9 +/- 1.4% and 4.4 +/- 1.4% within 48 h, respectively, that is equivalent to 43 +/- 18 and 50 +/- 20 MBq of (90)Y, respectively. Family members received a radiation exposure of 40 +/- 14 microSv over seven days. CONCLUSION: During preparation and application of (90)Y-Zevalin appropriate radiation shielding is necessary. For family members as well as nursing staff no additional special radiation protection measures beyond those being common for other nuclear medicine procedures are necessary.

Antibodies, Monoclonal↗
PubMed2002

Temporary shielding of hot spots in the drainage areas of cutaneous melanoma improves accuracy of lymphoscintigraphic sentinel lymph node diagnostics.

Detection of the "true" sentinel lymph nodes, permitting correct staging of regional lymph nodes, is essential for management and prognostic assessment in malignant melanoma. In this study, it was prospectively evaluated whether simple temporary shielding of hot spots in lymphatic drainage areas could improve the accuracy of sentinel lymph node diagnostics. In 100 consecutive malignant melanoma patients (45 women, 55 men; age 11-91 years), dynamic and static lymphoscintigraphy in various views was performed after strict intracutaneous application of technetium-99m nanocolloid (40-150 MBq; 0.05 ml/deposit) around the tumour (31 patients) or the biopsy scar (69 patients, safety distance 1 cm). The images were acquired with and without temporary lead shielding of the most prominent hot spots in the drainage area. In 33/100 patients, one or two additional sentinel lymph nodes that showed less tracer accumulation or were smaller (<1.5 cm) were detected after shielding. Four of these patients had metastases in the sentinel lymph nodes; the non-sentinel lymph nodes were tumour negative. In 3/100 patients, hot spots in the drainage area proved to be lymph vessels, lymph vessel intersections or lymph vessel ectasias after temporary shielding; hence, a node interpreted as a non-sentinel lymph node at first glance proved to be the real sentinel lymph node. In two of these patients, lymph node metastasis was histologically confirmed; the non-sentinel lymph nodes were tumour free. In 7/100 patients the exact course of lymph vessels could be mapped after shielding. In one of these patients, two additional sentinel lymph nodes (with metastasis) were detected. Overall, in 43/100 patients the temporary shielding yielded additional information, with sentinel lymph node metastases in 7%. In conclusion, when used in combination with dynamic acquisition in various views, temporary shielding of prominent hot spots in the drainage area of a malignant melanoma of the skin leads to an improvement in the accuracy of identification and localisation of sentinel lymph nodes by lymphoscintigraphy.

Adolescent↗
PubMed2000

Recovery correction for quantitation in emission tomography: a feasibility study.

In emission tomography, the spread of regional tracer uptake to surrounding areas caused by limited spatial resolution of the tomograph must be taken into account when quantitating activity concentrations in vivo. Assuming linearity and stationarity, the relationship between imaged activity concentration and true activity concentration is only dependent on the geometric relationship between the limited spatial resolution of the tomograph in all three dimensions and the three-dimensional size and shape of the object. In particular it is independent of the type of object studied. This concept is characterized by the term "recovery coefficient". Recovery effects can be corrected for by recovery coefficients determined in a calibration measurement for lesions of simple geometrical shape. This method works on anatomical structures that can be approximated to simple geometrical objects. The aim of this study was to investigate whether recovery correction of appropriate structures is feasible in a clinical setting. Measurements were done on a positron emission tomography (PET) scanner in the 2D and 3D acquisition mode and on an analogue and digital single-photon emission tomography (SPET) system using commercially available software for image reconstruction and correction of absorption and scatter effects. The results of hot spot and cold spot phantom measurements were compared to validate the assumed conditions of linearity and stationarity. It can be concluded that a recovery correction is feasible for PET scanners down to lesions measuring about 1.5xFWHM in size, whereas with simple correction schemes, which are widely available, an object-independent recovery correction for SPET cannot be performed. This result can be attributed to imperfections in the commercially available methods for attenuation and scatter correction in SPET, which are only approximate.

Feasibility Studies↗
PubMed2000

Classification of the lymphatic drainage status of a primary tumour: a proposal.

AIM: Creation of a classification of the lymphatic drainage status of a primary tumour. It shall enable comparison of different approaches, standardization and quality control. METHODS: Identification and topographic localization of the sentinel node(s) using lymphatic radionuclide gamma camera imaging and/or gamma probe detection and/or vital dye mapping. RESULTS: A classification comprising four classes (D-Class I-IV) and distinct subclasses (A-E) proved to be simply to be learned and applicable as well as reliably reproducible. It is based on the number of sentinel lymph nodes and their locations and can be combined with the pathological and molecular biological lymph node status. D-classes/subclasses obtained in 420 patients with malignant melanoma of the skin are presented. CONCLUSIONS: The classification is applicable to different approaches. Its diagnostic, therapeutic and prognostic value should be studied prospectively in those primary tumours which preferably metastasis via their draining lymphatic vessels.

Documentation↗
PubMed1991

Spatial resolution in SPECT: influence of measurement set-up and reconstruction parameters.

The ability of a tomographic system to detect small lesions and to assess them quantitatively is affected by several performance parameters, among them spatial resolution in the transverse slice and in the axial direction. This study was done to determine reconstructed resolution under clinical conditions for various parameters, i.e. radius of rotation, radial position within the transverse field of view, and amount of smoothing in the reconstruction process (various reconstruction filters and a Metz prefilter). The axial resolution is independent of the reconstruction filter but depends on the prefilter, the radius of rotation (ROR), and the source position. The transaxial resolution is dependent on the reconstruction filter, the prefilter, the ROR, and the source position. The reconstructed resolution and the system resolution were compared and differences between both are discussed.

Humans↗
PubMed1985

Polyethylene-based water-equivalent phantom material for x-ray dosimetry at tube voltages from 10 to 100 kV.

A water-equivalent plastic material RW-1, in the form of thin foils as well as of thicker sheets, has been produced by melting powdered polyethylene together with CaCO3 and MgO. The mixture has been developed in a three-step procedure, starting with provisional mixtures and using data from their measured attenuation curves to determine the final composition. The attenuation curves of RW-1 and of water, as well as their backscatter factors, are in excellent agreement for x-ray tube voltages from 10 to 100 kV.

Humans↗