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V John

Publications and source records attributed to V John.

At least 37 records · Page 2Linked to original sources
PubMed1996

Frequency-filtered image post-processing of digital luminescence radiographs in pulmonary nodule imaging.

AIM: The aim of the study was to optimize unsharp masking image post-processing of digital luminescence radiographs (DLR) for the representation of pulmonary nodules, and to compare DLR to screen-film radiography at two dose levels. PATIENTS AND METHODS: A total of 284 CT-validated pulmonary nodules were evaluated. One hundred and forty-nine nodules were exposed with a 200-speed screen-film combination (SFC) and 135 nodules with a 400-speed SFC, with correspondingly exposed storage phosphor images. The kernal size in digital post-processing using 'unsharp masking' was varied between S 10 (2.83 mm) and S 70 (19.80 mm). A total of 11928 individual assessments were obtained from six independent observers and evaluated in multifactorial variance analyses. RESULTS: The large filter kernels of S 40 and S 70 were on a par with the 200-speed SFC (P > 0.05). As the exposure dose was reduced, the quality of the digital image vis-à-vis the 400-speed SFC improved significantly (P < 0.05). Smaller filter kernels (S 10; S 20) producing edge-enhancement processing were significantly inferior to the analog image technique in both dose ranges (P < 0.05). CONCLUSIONS: At speed class 200, low-frequency emphasizing digital image post-processing with large filter kernels are significantly superior to high-frequency emphasizing filtrations for the recognition of pulmonary nodules. In the lower dose range DLR with large filter kernel unsharp masking processing showed significantly improved image quality compared to 400 speed SFC for the detection of pulmonary nodules.

Adolescent↗
PubMed1996

Effects of varying filter kernel sizes on the image quality of interstitial lung diseases.

PURPOSE: The aim of the study was to optimize the postprocessing of digital luminescence radiographs of interstitial infiltrates of the lung. MATERIAL AND METHODS: Ninety-seven patients with established diseases of the lung parenchyma were examined: 514 pathological details were investigated, using a 200-speed screen-film system and a storage phosphor plate. In digital postprocessing, the size of the filter kernel (S) varied between S 5 and S 70. Based upon 32896 individual evaluations, the image quality was evaluated in multifactorial variance analyses. RESULTS: The digital standards were significantly inferior to the tested screen-film system. The large filter kernel S 70 and the small filter kernels S 5 and S 10, as well as an algorithm for edge enhancement, showed selective advantages in the depiction of nodular or small linear structures. For micronodular and linear structures, kernel sizes of S 20 and S 40 produced equally good results (p > 0.05). CONCLUSION: Whenever optimized postprocessing is involved, storage phosphor radiography is equal to a modern screen-film system and can be substituted for the latter without any loss of image quality; this is especially valid for the imaging of interstitial infiltrates of the lung.

Female↗
PubMed1996

ROC-analysis of detection performance by analogue and digital plain film systems in chest radiography.

PURPOSE: To compare the performances of 4 imaging systems in the diagnostic radiology of the chest: an asymmetric screen-film combination (a-SFC); a conventional screen-film combination of speed class 200 (SFC); a screen-film combination of speed class 200 with an aluminium lung filter; and digital luminescence radiographs (DLR). MATERIAL AND METHODS: Object detectability studies were carried out using an anthropomorphic chest phantom. The images were obtained under standard exposure conditions at 125 kVp. The detection performance of the various systems was evaluated by receiver operating characteristic (ROC) analysis on the basis of a total of 12,240 observations. RESULTS: In the overall evaluation the a-SFC and the SFC plus lung filter received equally high ratings of 0.878+/-0.018 and 0.860+/-0.21, respectively (p>0.05). There was no significant difference between the 200-speed SFC and the storage phosphor radiographs. In the mediastinum all the tested systems were clearly superior to the 200-speed SFC (p<0.05) while in the lung fields the 200-speed SFC received a high rating of 0.866+/-0.026. The a-SFC had slight advantages over the SFC plus lung filter and the 2 digital imaging modes (p>0.05). CONCLUSION: The a-SFC and the digital luminescence radiographs provide a significant gain in diagnostic information in the mediastinum without diminishing detail detectability in the lung fields and without additional radiation exposure.

Filtration↗
PubMed1996

A role for CD8+ T lymphocytes in osteoclast differentiation in vitro.

Bone loss associated with chronic inflammatory diseases has been attributed to the release of cytokines from T lymphocytes. However, the role of T lymphocyte subsets in the mediation of osteoclast activity has not been extensively studied. Cocultures of murine bone marrow and BALC cells (murine calvarial-derived cell line) were used to study osteoclast differentiation. Murine marrow was left intact or depleted of cells expressing the CD8 or CD4 antigen by immunomagnetic separation and then cocultured with BALC cells in the presence or absence of 1,25-(OH)2D3. Depleting bone marrow of CD4-positive (CD4+) cells did not affect osteoclast differentiation (formation of tartrate-resistant acid phosphatase positive cells with three or more nuclei). However, depletion of CD8-positive (CD8+) cells resulted in a 40% increase in the number of osteoclasts formed. Addition of CD8+ cells to CD8+ cell depleted cocultures via Transwells abolished the stimulatory effects on osteoclast differentiation resulting from CD8+ cell depletion. Neutralizing antibodies to interleukin-4 and transforming growth factor-beta did not affect osteoclast differentiation in these cultures. These findings suggest that CD8+ cells may be involved in the regulation of osteoclast differentiation and that this effect is not mediated by interleukin-4 or transforming growth factor-beta.

Animals↗
PubMed1995

Intra- and inter-subject variabilities of CGP 33101 after replicate single oral doses of two 200-mg tablets and 400-mg suspension.

PURPOSE: The purpose of this study was to use a replicate designed trial to assess the overall, intra- and inter-subject variabilities in pharmacokinetic parameters of CGP 33101 after oral administration of tablets relative to that of powder suspended in water, and to determine the relative proportion of the intra-subject variance to the overall variability. METHODS: Sixteen healthy subjects were randomly assigned to four groups to receive tablets and suspension twice in four different treatment sequences. The plasma concentration-time profile of CGP 33101 was characterized in terms of Cmax, Tmax, and AUC. Bioavailability of tablets relative to suspension and intra- and inter-subject variability were assessed by statistical analysis. RESULTS AND CONCLUSIONS: The overall variabilities in absorption kinetics of CGP 33101 in healthy subjects were small with CV's of the population mean values for AUC and Cmax less than 26% for both tablets and suspension. Contribution of intra-subject variability to the overall variability was also small (approximately 20%). Both the overall and intra-subject variabilities of AUC and Cmax after suspension were larger than after the tablets. However, the differences in variability between tablets and suspension were not statistically significant (p > 0.05). The tablet formulation was bioequivalent to suspension in terms of rate and extent of absorption based on 90% conventional confidence intervals (for AUC and Cmax) and Wilcoxon rank-sum test (for Tmax).

Administration, Oral↗
PubMed1995

[ROC analysis in post-processing of image data in digital thoracic radiography].

PURPOSE: To examine the extent to which digital luminescence radiography (DLR) can be used for the imaging of pulmonary nodules and interstitial lung disease in chest radiography without any loss of image quality. Additionally: to examine whether post-processing of image data can optimise the recognizability of varied image details. MATERIALS AND METHODS: Detail perceptibility studies were performed on an anthropomorphic thorax phantom with simulated nodules and small linear and reticular details. Under standard conditions, digital luminescence radiographs were obtained in 7 different image modes, and these were compared with a 200-speed screen-film system. The detection of these systems was evaluated in an ROC analysis on the basis of 19,200 individual observations. RESULTS: Edge enhancement or application of high-frequency-enhancing small filter kernels (S 5) slightly improves the detection of linear structures; however, the illustration of nodular details is markedly reduced. Larger filter kernels (S 20, S 40) make a definitive detection possible--not only of circular, but also of linear details. CONCLUSIONS: Storage phosphor radiographs are equal to the tested analog screen-film-system. The optimization of post-processing can be helpful in the prevention of routine multiple documentations.

Adult↗
PubMed1995

[The use of an asymmetric film-screen combination for the imaging of round pulmonary foci].

PURPOSE: To examine the diagnostic advantages of an asymmetric film-screen system (a-FSS) compared to a conventional 200-speed FSS with and without anatomical lung filter. METHODS: Standard radiographs were obtained from an anthropomorphic chest phantom with simulated pulmonary nodules. The existence or non-existence of nodules was assessed in 7344 individual observations. The results were evaluated using ROC analysis. RESULTS: In an overall evaluation the a-FSS with an ROC area of 0.873 +/- 0.018 was not significantly superior (p > 0.05) to the lung filter but significantly superior (p < 0.05) to the 200-speed FSS. In the mediastinum the a-FSS and the lung filter were significantly superior (p < 0.05) to the 200-speed FSS. In the lung areas the 200-speed FSS and the a-FSS attained equivalent results (p > 0.05), whereas the lung filter was rated significantly lower (p < 0.05). CONCLUSIONS: Asymmetric FSS improves chest diagnostics, because it yields significantly more diagnostic information in the mediastinum using equivalent x-ray exposure without reducing the image quality in the lung areas in respect of simulated pulmonary nodules.

Evaluation Studies as Topic↗
PubMed1995

[ROC analysis of image quality in digital luminescence radiography in comparison with current film-screen systems in mammography].

AIM: To compare in mammography the image quality of digital luminescence radiography (DLR) to that of usual film screen mammography and xeromammography. MATERIALS AND METHODS: Three single emulsion film-screen combinations, one double coated high resolution film and xeroradiography, were tested for this purpose. In our phantom study the detectability of microcalcifications, fibrils and low contrast details were first of all studied separately. Image processing techniques were, for example, contrast variation by grey scale level windowing, "unsharp mask" filtering and regulatable edge enhancement. Phantom images were made and then the image quality was evaluated by observer performance study using a receiver operating characteristic (ROC analysis). RESULTS: Best results in respect of detection of microcalcifications and fibrils were found in xeroradiography, luminescent image plate and double-coated film-screen combination. These systems showed more favourable ROC curves than the single emulsion film-screen combinations. CONCLUSIONS: Our results indicate that image quality of digital images in the field of image processing is equal to that of conventional mammographic techniques and partially superior to detection of low contrast details.

Breast Neoplasms↗
PubMed1994

The absence of a pharmacokinetic interaction between aspirin and the angiotensin-converting enzyme inhibitor benazepril in healthy volunteers.

Potential effects of the coadministration of single doses of aspirin (325 mg) and of benazepril hydrochloride (20 mg) on the pharmacokinetics and the metabolism of these two drugs were evaluated in 12 healthy subjects. Plasma concentration profiles of benazepril, its active metabolite benazeprilat, and total salicylic acid were determined together with urinary excretion of benazeprilat, salicylic acid, salicyluric acid, and salicylate glucuronides. Almost superimposable plasma profiles of benazepril, benazeprilat, and total salicylic acid were achieved with the drugs given alone and concomitantly. The coadministration of benazepril hydrochloride and aspirin did not modify the pharmacokinetics or the metabolism of the two drugs.

Adult↗
PubMed1994

The production of saliva of patients with juvenile chronic arthritis (JCA).

About 12-16 p.c. of the patients with JCA had a reduced saliva production. These were older than twelve years or belonged to the systemic form of JCA. The reduced saliva production is clinically not discernible. Enteral deviation or disturbances are observed with rheumatic arthritis. Various examinators have found a Sicca syndrome at about 6-12 p.c. of patients suffering from rheumatic arthritis (1, 2, 3). The mostly retrospective examinations do not allow a direct comparison. Up to now the Sicca syndrome has rarely been observed with the Juvenile Chronic Arthritis. This investigation is to present the quantitative production of saliva of JCA patients.

Adolescent↗
PubMed1993

Development of lipophilic anticancer agents for the treatment of brain tumors by the esterification of water-soluble chlorambucil.

The lipophilic derivatives of the anticancer alkylating agent chlorambucil, chlorambucil-methyl, -isopropyl and -tertiary butyl esters, were synthesized and administered i.v. to anesthetized rats. Plasma and brain concentrations of these agents and of their active metabolites, chlorambucil and phenylacetic mustard, then were determined by high-performance liquid chromatography between 5 and 60 min. Whereas large amounts of chlorambucil-tertiary butyl ester entered and were maintained in brain, lower amounts of chlorambucil-isopropyl ester and no chlorambucil-methyl ester were found in brain. The comparative brain/plasma concentration-time integral ratios of the total active agents generated from chlorambucil-tertiary butyl, -isopropyl and -methyl esters were 0.85, 0.12 and 0.06, respectively, compared to a ratio of 0.02 for chlorambucil. In vitro alkylating activity of each ester was compared to that of equimolar chlorambucil, by reaction with 4-(p-nitrobenzyl)pyridine. Each ester possessed high intrinsic alkylating activity, equal to 38.4, 57.0 and 69.9% of chlorambucil activity, for the -tertiary butyl, -isopropyl and -methyl esters, respectively. Therefore each is an active antineoplastic agent irrespective of whether or not chlorambucil is regenerated. The rates of ester hydrolysis of these derivatives to chlorambucil were measured in fresh rat blood and in liver and brain homogenates at 37 degrees C. Chlorambucil-methyl and -isopropyl esters were hydrolysed quickly within 30 s in blood and liver, whereas chlorambucil-tertiary butyl ester was more stable with half-lives of approximately 7 h and 2 h, respectively. All proved to be relatively stable in brain homogenate. Steric hindrance around the ester linkage of chlorambucil-tertiary butyl ester reduces its affinity to and rate of hydrolysis by plasma and liver esterases, and allows it to accumulate within the brain. Chlorambucil-tertiary butyl ester maintains high levels in brain despite rapidly declining plasma concentrations and, due to these favorable pharmacokinetics and to its intrinsic anticancer activity, it possess promising characteristics for the treatment of malignant brain tumors.

Alkylating Agents↗
PubMed1993

Human transbuccal absorption of diclofenac sodium from a prototype hydrogel delivery device.

The buccal delivery of the nonsteroidal antiinflammatory drug, diclofenac sodium (Voltaren), from a prototype hydrogel was studied in man in a randomized crossover design of buccal delivery and i.v. infusion. After a 30-min delay, plasma levels of diclofenac increased to near steady-state levels of 100 ng/ml by 3 hr. With each subject serving as his own control, the i.v. infusion data facilitated the calculation of a mean steady-state flux of diclofenac sodium of 2.1 +/- 0.6 mg/cm2-hr across human buccal mucosa and a time lag of 1.0 +/- 0.5 hr. The large flux of this ionized species indicates that the traditional lipoidal model of buccal permeation based on the partition coefficient is inadequate.

Absorption↗
PubMed1993

[Are high-intensifying film-screen combinations suitable for the detection of fine interstitial lung changes? The results of a ROC study with an anthropomorphic thorax phantom].

Exposures of an anthropomorphic thorax phantom in posteroanterior projection were made using a focus-film distance of 200 cm and 125 kV with film-screen combinations in class 200 (Curix RP 1L/MR 200) and class 400 (Curix ST-L/Regular). Pathomorphological structures of the lung parenchyma of fine nodular, linear and reticular types were simulated by suitable materials. A ROC analysis including a t-test showed no significant difference in the evaluation of these structural details (p > 0.05). In order to describe image quality for the two film-screen systems, density curves, sigma D-curves and modulation transfer function (MTF) were determined. The only demonstrable difference was reduced MTF of 10-15% for the higher intensification film-screen combination with a resulting poorer resolution of 3.7 l/mm (for the 400 system) compared with 4.3 l/mm for the 200 system.

Evaluation Studies as Topic↗
PubMed1992

[Irradiation field controls by digital luminescence radiography].

Since portal images taken with conventional X-ray films suffer from poor contrast and unsharpness due to the high energy of the radiation beam, scattered radiation, patient motion, and the large dimensions of the radiation source, comparison of portal images with simulation images is often difficult and time consuming. Therefore many efforts have been made to improve such images. The use of storage phosphors and electronic image post-processing provides a remarkable improvement of image quality with better delineation of anatomical landmarks in high contrast areas such as head, neck, and mediastinum, as well as in low contrast regions, i.e. abdomen and pelvis.

Adolescent↗
PubMed1991

Nitroglycerin absorption from transdermal systems: formulation effects and metabolite concentrations.

We recently compared plasma concentrations of nitroglycerin and its two dinitrate metabolites in 16 healthy male subjects after application of two controlled-release transdermal formulations of the drug. Analysis of the resulting plasma concentration-time curves indicated that the two formulations did not produce equivalent concentrations of parent drug or either of the dinitrate metabolites during the initial period of dosing. In addition, both formulations produced concentrations of the two dinitrate metabolites that exceeded the concentration of the parent drug by severalfold. Even if the pharmacologic effect of the dinitrate metabolites is low compared to that of nitroglycerin, these higher concentrations may contribute to the effect of nitroglycerin. Scrutiny of the ratio of 1,2-glyceryl dinitrate to 1,3-glyceryl dinitrate in the 16 subjects confirmed previous observations that preferential formation of the 1,2-glycerol dinitrate metabolite may occur depending on the route of administration. This ratio may thus be indicative of the bioavailability of nitroglycerin following transdermal application. Additional data suggesting racial differences in nitroglycerin absorption after transdermal application are presented.

Administration, Cutaneous↗