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A Sparenberg

Publications and source records attributed to A Sparenberg.

9 recordsLinked to original sources
PubMed2000

Photonic hall effect of inactive mie scatterers in a faraday active matrix

We describe an experimental study of the photonic Hall effect in media consisting of a magneto-optically active matrix and magneto-optically inert Mie scatterers. We call such media reversed with respect to the normal media having magneto-optically active Mie scatterers in inert matrices in which the photonic Hall effect has been studied so far. We show the photonic Hall effect in reversed media to be proportional to VBl*, where V is the Verdet constant of the matrix, l(*) the transport mean free path of the liquid, and B the applied magnetic field. We further propose an empirical expression that unifies the results obtained in normal and reversed media and present a simple analytic model to illustrate the photonic Hall effect.

Journal Article↗
PubMed2000

Photonic hall effect in absorbing media

We describe an experimental and theoretical study of the effect of optical absorption on the photonic Hall effect in a passive matrix containing magnetoactive scatterers. We find that for the case of absorbing scatterers, the magnetotransverse light current changes sign and increases with increasing absorption. Good agreement is obtained with numerical calculations. For the case of an absorbing matrix, no effect was observed.

Journal Article↗
PubMed1992

Digital rectal examination, imaging, and systematic-sextant biopsy in identifying operable lymph node-negative prostatic carcinoma.

The value of digital rectal examination, computerized tomography, magnetic resonance imaging, prostate-specific antigen, transrectal ultrasonography, and systematic-sextant biopsy in the identification of lymph node-positive patients before radical prostatectomy was analyzed in 103 men who had pelvic lymph node dissection, CT had a sensitivity of only 7% and a specificity of 96% in detecting lymph nodes, whereas magnetic resonance imaging had a sensitivity of 50% and a specificity of 100%. To evaluate the use of tumor volume in predicting lymph node metastasis, we counted the number of positive core biopsies and compared the results with the incidence of positive lymph nodes. If fewer than 5 positive core biopsies were considered negative for predicting lymph node metastasis, the sensitivity would be 67% (12 of 18), and the specificity 94% (50 of 53). To investigate tumor volume more precisely, we measured the extent of tumor volume in every biopsy as a percentage of the total biopsy core and added the percentage for the 6 biopsies. The lowest score was 10% (10% prostatic cancer in 1 of 6 cores), the highest score 580% (4 cores with 100% each and 2 with 90% each). The score was analyzed for sensitivity and specificity in predicting lymph node metastasis. If a score of 280% was used as a cutoff point, the sensitivity was 71% (10 of 14) and the specificity 91% (52 of 57). When we include the grading system by multiplying the percentage of tumor volume with tumor grade, the difference between the lymph node-positive state and lymph node-negative state becomes even more readily apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

[The diagnosis of bladder carcinomas by NMR tomography: an improvement with Gd-DTPA?].

85 patients suffering from urinary bladder carcinoma were examined by magnetic resonance imaging in a prospective study. Following precontrast diagnosis, 15 patients were given an intravesicular application of gadolinium-DTPA (Gd-DTPA). Another 35 patients received an intravenous bolus of GD-DTPA. A diagnostic advantage was achieved in only 2 of 15 tumours by using intravesicular contrast application. Compared to the precontrast diagnosis, a 14% improvement from 69% (precontrast) to 83% (contrast medium) was seen with Gd-DTPA applied intravenously in the diagnosis of the tumour stage. The diagnostic gain lies in the improved tumour recognition, the improved demarcation of papillary, non-muscle-infiltrating tumours and in the more definite diagnosis of infiltration into neighbouring organs and the pelvic wall. Demarcation of perivesicular fatty infiltration is rendered more difficult by Gd-DTPA.

Administration, Intravesical↗
PubMed1990

Morphological changes in cultures of hippocampus following prenatal irradiation in the rat.

The effect of prenatal irradiation was studied in organotypic cultures of hippocampus, prepared from newborn rats that had been exposed to whole-body irradiation of 1 Gy from a 60Co-source at day 13 of pregnancy. Light and electron microscopic observations showed remarkable damage to neuronal mitochondria accompanied by extensive swelling, vacuolation of the Golgi complex, and formation of multilamellar bodies and vesicles of the lysosomal type. In contrast to neuronal alterations, no delay in synaptogenesis or onset of myelination was observed based upon the absence of significant morphological changes in synapses and myelin sheaths. Using this tissue culture model it could be confirmed that prenatal exposure to irradiation, even at low doses, induces specific morphological changes in the brain.

Animals↗
PubMed1990

[The value of fractionated afterloading therapy in the treatment of inoperable malignant brain tumor].

Since 1985, inoperable brain tumors, astrocytoma III or glioblastoma multiforme, have been treated by means of fractionated afterloading therapy combines with subsequent percutaneous irradiation. A screw that was specifically designed, allowed us to fix a precious metal tube to the skull cap for about eight days making possible the application of a marginal tumor dose of 30 Gy at a daily fractionation of 2 X 2 Gy using the iridium-afterloading-technique. Percutaneous saturation with another 30-40 Gy followed. Supported by radiobiological considerations, fractionation also appears to have a favorable influence on the perifocal edema formation in the brachytherapy of malignant brain tumors. After an observation period of four years probabilities of survival amounting to six months and twelve months can be calculated (according to Kaplan-Meier) for 68% and 27% of the total collective, respectively (n = 38). The survival rate for patients without pretreatment (n = 16) was 81% and 41% after six and twelve months respectively.

Brachytherapy↗
PubMed1987

[Clinical experiences with ultrasound-reflection computerized tomography of the breast].

Ultrasound-reflection computed tomography (URCT) of the breast can produce astonishingly detailed high resolution images of the breast, particularly in the coronal plane. In some cases it improves the demonstration of the structure of scirrhous carcinomas in this plane. On the other hand, some valuable diagnostic features known from conventional breast sonography, such as acoustic shadows and hyper-reflective area (cysts) are suppressed on URCT images and are not readily recognized. Despite individual outstanding images, a comparison carried out on 100 patients showed no advantages of URCT compared with high-resolution real-time sonography.

Adenocarcinoma, Scirrhous↗