Biomedical subjects

A Kästner

Publications and source records attributed to A Kästner.

11 recordsLinked to original sources

PubMed2002

[First clinical experience with a full-size, flat-panel detector for imaging the peripheral skeleton - Part II: Post-processing with a newly developed adaptive autowindow algorithm].

PURPOSE: of the second part of the investigation was the evaluation of a newly developed adaptive autowindow algorithm in comparison to the system processing radiographs of the wrist and ankle to further optimize the image quality with softcopy reading. MATERIAL AND METHODS: All 120 radiographs of the wrist and all 100 radiographs of the ankle used in the 1st part of this paper were processed with the adaptive autowindow algorithm. The evaluation was again performed by 5 radiologists with softcopy reading. For the data analysis a variation of the Visual Grading Analysis (VGA) was used. RESULTS: Up to 19 % of the wrist radiographs and 2 % of the ankle radiographs processed with the system software had to be processed manually afterwards to get acceptable results. By the application of the adaptive autowindow algorithm a manual post-processing was no longer necessary. Highly significant (p less-than-or-equal 0.001) differences for all criteria to be evaluated were found for the wrist radiographs and in the case of the ankle radiographs for the bone contrast, the contrast in soft-tissue regions, the fine details in the bone and the artifacts, the adaptive autowindow algorithm performed always better than the system software. CONCLUSION: Using half of the exposition dose on a flat-panel detector, an optimized post-processing leads to comparable or better results compared to the conventional film-screen-system concerning the image quality.

Algorithms↗

PubMed2002

[Optimized image processing with modified preprocessing of image data sets of a transparent imaging plate by way of the lateral view of the cervical spine].

PURPOSE: To improve the diagnostic quality of lateral radiographs of the cervical spine by pre-processing the image data sets produced by a transparent imaging plate with both-side reading and to evaluate any possible impact on minimizing the number of additional radiographs and supplementary investigations. MATERIAL AND METHODS: One hundred lateral digital radiographs of the cervical spine were processed with two different methods: processing of each data set using the system-imminent parameters and using the manual mode. The difference between the two types of processing is the level of the latitude value. Hard copies of the processed images were judged by five radiologists and three neurosurgeons. The evaluation applied the image criteria score (ICS) without conventional reference images. RESULTS: In 99 % of the lateral radiographs of the cervical spine, all vertebral bodies could be completed delineated using the manual mode, but only 76 % oft the images processed by the system-imminent parameters showed all vertebral bodies. Thus, the manual mode enabled the evaluation of up to two additional more caudal vertebral bodies. The manual mode processing was significantly better concerning object size and processing artifacts. This optimized image processing and the resultant minimization of supplementary investigations was calculated to correspond to a theoretical dose reduction of about 50 %. CONCLUSION: The introduction of optimized organ programs for the upper and lower cervical spine based on the 12-bit data of the images should improve the evaluation of the lateral radiograph of the cervical spine without reducing the latitude value.

Cervical Vertebrae↗

PubMed2001

[First clinical experience with a full-size, flat-panel detector for imaging the peripheral skeletal system].

PURPOSE: This investigation was intended to show that exposures of the peripheral skeleton system can be done with half of the dose used for conventional screen-film systems with a full-size CsI/a-Si flat panel detector. MATERIAL AN METHODS: 120 exposures of the wrist and 100 exposures of the ankle have been made on a full-size flat panel detector system (43 x 43 cm). The patient dose has been reduced by a factor of two compared to conventional images. Five radiologists evaluated every image as a softcopy and a hardcopy image. For the evaluation, a variation of the Visual Grading Analysis (VGA) without reference images was used. For the determination of the patient entrance dose, measurement of a phantom were performed. RESULTS: A dose reduction of about 50 % is possible with the same or even better image quality in routine diagnostics. Only 3 % of the ankle and approx. 21 % of the wrist exposures required a postprocessing. Exposures with implants did not show any artifacts and some of the those achieved better evaluation results compared with exposures without implants. CONCLUSION: A halving of the patient dose is possible with acceptable results for the image quality. The effect of an improved image processing remains to be evaluated. The patient entrance dose is suitable for an evaluation of a radiographic detector and especially for a dose-referred comparison of digital X-ray units.

Ankle Joint↗

PubMed2000

Digital selenium radiography: detection of subtle pulmonary lesions on images acquired with and without an additional antiscatter grid.

OBJECTIVE: the objective of this ROC-study was to evaluate the diagnostic efficacy of images acquired with a grid in digital selenium radiography compared to that on images obtained with the integrated air gap only. MATERIALS AND METHODS: seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Selenium radiography images were obtained either with or without an additional antiscatter grid. For images acquired with a grid either a similar or increased exposure level was used. Both normal and obese patients were simulated. RESULTS: When a grid was used with an equivalent detector dose and a higher exposure, diagnostic performance was significantly improved as compared to images obtained with only the air gap. ROC curve areas for mediastinal nodules and catheters were substantially higher for images acquired with a grid and the same exposure level compared to images obtained without a grid. However, detection of linear, net-shaped and reticulonodular structures in peripheral lung regions was significantly worse when a grid was used with an equivalent exposure level. Concerning the interpretation of images obtained from the normal and obese phantom models, no substantial differences were observed. CONCLUSION: a marked improvement in diagnostic performance could be achieved by means of the use of an additional antiscatter grid and an equivalent detector dose. However, when the same exposure was used, images acquired with the grid allowed a better detection of mediastinal structures although a worse performance was evident in radiolucent lung regions. Therefore, the routine use of a grid without increased exposure is not recommended.

Humans↗

PubMed1998

Pituitary adenylate cyclase activating peptides relax human pulmonary arteries by opening of KATP and KCa channels.

BACKGROUND: Pituitary adenylate cyclase activating peptides (PACAPs) are potent endothelium independent dilators of human coronary arteries; however, their effects on human pulmonary arteries are unknown. METHODS: The vasorelaxant effects of PACAP27 on human pulmonary segmental arteries were studied and the specific potassium (K+) channel regulatory mechanisms in the vasorelaxant effects were tested by means of isometric contraction experiments. RESULTS: PACAP27 produced dose dependent relaxations of 10 microM rings preconstricted with prostaglandin F2 alpha (PGF2 alpha) with half maximal relaxation (IC50) at 17 nM. Pretreatment of the vessels with the ATP sensitive K+ (KATP) channel blocker glibenclamide (1 microM) or with the Ca2+ activated K+ (KCa) channel blocker iberiotoxin (100 nM) inhibited the PACAP27 induced relaxation. CONCLUSIONS: These results provide evidence that PACAPs are potent vasodilators of human pulmonary arteries and that this relaxation might be mediated by opening of KATP and KCa channels.

Analysis of Variance↗

PubMed1998

Subtle pulmonary abnormalities: detection on monitors with varying spatial resolutions and maximum luminance levels compared with detection on storage phosphor radiographic hard copies.

PURPOSE: The purpose of this receiver operating characteristic study was to compare diagnostic efficacy with images displayed on monitors of varying spatial resolutions and maximum luminance levels to that with storage phosphor radiographic hard copies. MATERIALS AND METHODS: Seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Images were viewed by five radiologists on a 2,560 x 2,048 pixel monitor (maximum luminance, 75 foot-lamberts), on two 1,024 x 1,024 monitors with maximum luminance levels of 25 foot-lamberts and 75 foot-lamberts, respectively, as well as on hard copies. Monitor images were viewed both without and with systematic magnification. RESULTS: Overall visualization of the lesions was best on hard copies, but visualization on the 2,560 x 2,048 monitor was not found to be substantially different. Lines, reticular opacifications, and catheters were found to be particularly poorly visualized with the 1,024 x 1,024 monitor. These results could be statistically significantly improved only with a systematic magnification; however, this involved a considerable increase in viewing time. Observer performance was markedly inferior with the 1,024 x 1,024 monitor with the lower luminance. CONCLUSION: Diagnostic performance with a 1,024 x 1,024 monitor is statistically significantly inferior to that with hard copies. A statistically significant improvement can be achieved with a high-resolution 2,560 x 2,048 monitor with a maximum luminance of 75 foot-lamberts.

Angiography, Digital Subtraction↗

PubMed1995

Effects of prostaglandin E1, prostaglandin E0 and SPM 206 on isolated human coronary arteries.

The effects of PGE1, PGE0 and the stable PGE1-analogue SPM 206 on human epicardial coronary arteries were studied in vitro. The tension of the isolated arterial rings was measured isometrically. After precontraction, concentration-response curves with the compounds were performed. PGE1 and SPM 206 elicited concentration-dependent relaxations which are counteracted by a contractile action in higher concentrations. In PGE0, the contractile action occurred even in lower concentrations. This contraction was antagonized by the selective thromboxane A2 antagonist SQ 29,548, resulting in an equipotent relaxation for all three compounds.

Alprostadil↗

PubMed1995

Pituitary adenylate cyclase activating peptides are endothelium-independent dilators of human and porcine coronary arteries.

The PACAPs have been shown to be potent vasodilators in different animal species. Data in humans are still lacking. Therefore we investigated the effects of PACAP 38, PACAP 27 and VIP on isolated human and porcine coronary arteries (HCA and PCA). Our data show, that the PACAPs are endothelium-independent vasorelaxants, which in HCA are slightly more potent than VIP. The N-terminal shortened peptides PACAP 6-38 and PACAP 6-27 also show relatively potent vasorelaxant effects, acting as partial agonists. Glibenclamide, a selective inhibitor of ATP-sensitive potassium channels, partially reverses the effects of the PACAPs, indicating an involvement of these channels in the mechanism of action.

Animals↗

PubMed1995

Reproducibility of basal and induced DNA single-strand breaks detected by the single-cell gel electrophoresis assay in human peripheral mononuclear leukocytes.

The aim of the reported study was to investigate the reproducibility of the single-cell gel electrophoresis (SCGE) assay in the determination of DNA single-strand breaks (SSBs) and to estimate the statistical requirements when the SCGE assay is used for the detection of genotoxicity in humans. In human peripheral mononuclear leukocytes (PMLs), we repeatedly measured the rate of SSBs after in vitro incubation of cells for 1 h at 4 degrees C in phosphate buffered saline (PBS, basal) or 10 microM or 50 microM H2O2 (induced). Intra-assay variation was determined from cryopreserved PMLs of a single donor. To assess intrasubject and intersubject variation, PMLs of ten healthy, nonsmoking subjects (aged 19-37 years) were tested 5-9 times. Cryopreserved cells revealed a mean coefficient of variation of 18% (PBS) and 7%-9% (H2O2). There were statistically significant differences between individuals in the rate of SSBs after incubation in PBS (P < 0.01), 10 microM H2O2 (P < 0.001), and 50 microM H2O2 (P < 0.001). The range of interindividual variability was 26% for basal and 12%-13% for induced SSBs, and the coefficient of intraindividual variation was 18%-72% (PBS) and 7%-23% (H2O2). Neither basal nor induced rates of DNA damage were related to gender or age. Estimates of the minimum detectable effects were based on these observed sources of variability (power 90%, level of significance 5%, assumed sample size 50). With two different groups, a difference of 31% in basal SSBs or 12% in induced SSBs would be detectable. Repeated measurement within one group could detect a difference of 26% in basal and 9% in induced SSBs. In summary, the SCGE assay appears to be suitable for the detection of single-strand breaks, e.g., in biomonitoring or environmental medicine, and the statistical requirements could be derived from our analysis of the sources of variability.

Adult↗

PubMed1995

Differences in basal and induced DNA single-strand breaks between human peripheral monocytes and lymphocytes.

The aim of this study was to compare the susceptibility of peripheral monocytes and lymphocytes to oxidant-induced DNA single-strand breaks (SSB). DNA damage was assessed by the alkaline single-cell gel electrophoresis (SCGE) assay. Total peripheral mononuclear leukocytes (PML), PML enriched in lymphocytes and PML enriched in monocytes were used. The basal rate of SSB was measured after in vitro incubation of cells for 1 h in phosphate-buffered saline, and the induced rate after incubation in 10 microM or 50 microM H2O2. Incubation was performed at 4 degrees C to limit the possible influence of DNA repair. Lymphocyte-enriched PML were obtained after adhesion of the monocytes to tissue-culture treated plastic, and monocyte-enriched PML by removal of monocytes from the plastic through trypsin. In all samples, cell differentiation was performed using an immunofluorescence technique with antibodies against T- and B-lymphocytes and cytospin preparations. The rate of SSB was determined by visual scoring according to 6 predefined categories of DNA damage and was expressed as mean score (range 0-500) per 100 cells. There was a linear relationship between the percentage of lymphocytes in the samples and the basal rate of SSB (p < 0.001, slope 0.67 score units per %). The same was true for induced DNA damage after incubation in 10 microM H2O2 (p < 0.001, slope 3.80 score units per %) or 50 microM H2O2 (p < 0.001, slope 3.22 score units per %). These regression analyses revealed a 2.9-fold greater rate of basal DNA damage in lymphocytes compared to monocytes and an 11.3-fold greater rate for the damage induced by 10 microM H2O2. We conclude that there are marked differences in the rate of basal and induced SSB between lymphocytes and monocytes, suggesting differences in antioxidant capacity between the two cell populations. These findings indicate that the assessment of SSB for biomonitoring and genotoxicity testing using PML has to take into account possible changes in cellular composition.

Adult↗

PubMedDate not supplied

Pituitary adenylate-cyclase-activating peptides relax human coronary arteries by activating K(ATP) and K(Ca) channels in smooth muscle cells.

Pituitary adenylate-cyclase-activating peptides (PACAPs) are potent dilators of arteries, including human coronary arteries. We tested the importance of specific K+ channel regulatory mechanisms in human arterial smooth muscle relaxation induced by PACAPs, using contraction and patch clamp measurements on human coronary artery vascular smooth muscle cells. PACAP27 and PACAP38 produced dose-dependent relaxations of 5 microM PGF2alpha-preconstricted rings, with half-maximal relaxations at 1.0 nM and 2.0 nM, respectively. Both peptides induced complete relaxation at 100 nM. Pretreatment of the vessels with the ATP-dependent K+ (K(ATP)) channel blocker glibenclamide (1 microM) or with the Ca2+-activated K+ (K(Ca)) channel blocker iberiotoxin (100 nM) inhibited PACAP27-induced relaxation in an additive manner. Moreover, in the patch clamp experiments on freshly isolated cells from human coronary arteries, PACAP27 (100 nM) induced a large, nonrectifying, outward (I(K)(ATP)) K+ current in a proportion of cells and a voltage-dependent outward (I(K)(Ca)) K+ current in other cells. The PACAP27-induced I(K)(ATP) was blocked by glibenclamide (3 microM), while the PACAP27-stimulated I(K)(Ca) was blocked by iberiotoxin (100 nM). These findings provide the first evidence that relaxation of arterial smooth muscle cells by PACAPs is mediated by opening of K(ATP) and K(Ca) channels. The data indicate that both K(ATP) and K(Ca) channels in vascular smooth muscle cells may serve as final common pathway to induce vasorelaxation by endogenous vasoactive signals in man.

Coronary Vessels↗