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Biomedical subjects

L Hollender

Publications and source records attributed to L Hollender.

At least 19 recordsLinked to original sources
PubMed2005

[The drug industry: a national issue].

Following up on a letter received from the Mrs. Nicole Fontaine, the Delegate Minister of Industry, requesting recommendations concerning the "serious threats" to the French drug industry, the Academy of Medicine auditioned the five leading French pharmaceutical firms and two foreign firms. Their complains led to proposals for six recommendations: recognize the strategic importance of the drug industry, conclude several years of contracts between the Economic committee on health products and the drug industry, facilitate clinical trails of drugs in France, favor relations between the national drug industry and university research centers, Inserm, Cnrs and the administration, encourage the development of biotechnology firms which represent one of the most promising areas of therapeutic research, propose the creation of an interministerial drug counsel presided by the Prime Minister to establish and implement a common national strategy.

Academic Medical Centers↗
PubMed2001

["Cultural" barriers in the development of ambulatory surgery].

Several obstacles of different types seem to be a barrier to the promotion of "same day surgery": seizures of misinformed patients, local mentalities, reticence coming from different administrations, from control organizations also from general practitioners, as even a kind of reserve revealed by hospitals doctors. All these arguments are discussed and disproved.

Ambulatory Surgical Procedures↗
PubMed1997

Detection of small differences in mass using a direct digital dental X-ray system.

OBJECTIVES: To evaluate experimentally how in direct digital radiography heterogenous detector response may influence the depiction of small mass differences. METHODS: A step wedge of a bone-simulating resin was imaged at 70 kVp using RadioVisioGraphy ZHR 32000. Exposure time and step wedge position on the detector varied. The pixel values of the stored images of the step wedge were converted to luminance values of the displayed images. RESULTS: The relationship between pixel and luminance values was non-linear. The difference in luminance between adjacent steps varied with position of step wedge. Regardless of position, there was an increase in difference of luminance between steps with increasing exposure. A greater relative change in luminance was consequently seen in the thinner parts of the step wedge. The failure to perceive individual steps of the wedge in its thicker parts was related to insufficient relative change in luminance between steps. CONCLUSIONS: The heterogeneous response of the detector resulted in a varying ability to depict small mass changes over the detector area.

Evaluation Studies as Topic↗
PubMed1996

Assessing the quality of radiographs accompanying biopsy specimens.

According to a long-established protocol, biopsy specimens of bony lesions sent to the University of Washington Histopathology Service are accompanied by relevant radiographs. In this study, the authors evaluated the quality of 114 radiographs, both intraoral and panoramic, from 89 consecutive cases. The radiographs were judged on their clinical usefulness, rather than on criteria for technically ideal images, and on the severity, rather than the number, of errors. Only 33 percent of the panoramic radiographs were of acceptable quality, while the quality of the intraoral radiographs was markedly better. The most striking feature was the lack of three-dimensional radiographic coverage of the site of surgical exploration.

Artifacts↗
PubMed1995

Digitizing of radiographs with a flatbed scanner.

OBJECTIVES: Flatbed scanners with the transparency scanning option can be used to digitize radiographs. The physical performance of this type of scanner was studied with regard to the digitizing of radiographs, including the dynamic range, the reproducibility and the homogeneity. METHODS: An Artix ArtiScan (Artix Technologies Inc., Milpitas, CA, USA) flatbed scanner with imaging editing software Aldus PhotoStyler (Aldus Corporation, Seattle, WA, USA) was used to digitize a stepped exposure image on Kodak T-MAT G films (Kodak, Rochester, NY, USA). The stepped exposure image was scanned at various locations and with different scanning settings. The pixel values of the resulting digital images were analysed. The stepped exposure image was also scanned by a laser densitometer to measure the optical densities of the steps on the film for comparison. RESULTS: Using the default scanning settings, the digitized images had pixel values distributed in a narrower range than that of the optical density values of the films. The range of the pixel values was widened by increasing the scanning time. Even then, the resulting pixel value profile was not identical to the optical density profile measured on film. The characteristic curve of this digitizing system was steeper than that of the film. Different pixel value distributions were obtained when the stepped exposure image was scanned at different positions on the scanning field, and when scans were obtained at different times. Reproducible results could be acquired when the images were scanned in the same area of the scanning field without changing the scanning settings and after the power had been on for a few minutes. CONCLUSIONS: In order to obtain digitized radiographs of any reliability from flatbed scanners, these should be carefully calibrated at the operating conditions.

Densitometry↗
PubMed1995

Linear unsharp mask filtering of linear cross-sectional tomograms of the posterior mandible.

Linear unsharp mask filtering is a digital image processing technique which can enhance diagnostic information by subtracting from the original image the linear blur which was formed in the direction of the linear tomographic movement. It was applied to linear cross-sectional tomograms of the posterior mandible aiming at retrieving cross-sectional outline information. This study demonstrated that the current Orthophos Program 16 with a 6.72 degrees tomographic angle does not provide accurate cross-sectional outline information of the posterior mandible. Linear unsharp mask filtering of these images also failed to provide more information. A larger tomographic angle of 10 degrees was employed with the Polytome to simulate the modified Program 16 with a wider beam. The resulting tomographic images showed better defined cross-sectional outlines, and after the linear unsharp mask filtering, the outlines were more readily retrieved. In order to get cross-sectional outline information of the posterior mandible, the tomographic angle of the Orthophos program 16 should be increased to more than 10 degrees which can be achieved by increasing the width of the x-ray beam.

Aged↗
PubMed1994

Frequency domain analysis of cross-sectional images of the posterior mandible.

The Siemens Orthophos (Siemens, München, Germany) is a panoramic machine that uses a microchip to control the movements of the radiation source and film. Several programs are available for different views of the facial skeleton and associated structures. Program 16 is dedicated to cross-sectional imaging of the posterior mandible. Three millimeter cross-sections were cut from 12 cadaver specimens of the mandible. These sections were imaged separately by contact radiography, 48 degrees hypocycloidal tomography of Philips Polytome (Philips-Massiot, Paris, France), and program 16 of the Orthophos panoramic machine. Program 16 of the Orthophos was also used to image the cross-sections after they were glued back together with the surrounding parts of the specimens. Four different images of the cross-sections were thus obtained. The contact radiographs were used as gold standards. Frequency domain analysis, which was used to compare the images resulting from each imaging modality, demonstrated that useful diagnostic information was in the range of 0.12 to 0.60 cycles/mm for the contact radiographs. In spite of differing tomographic angles for the Orthophos program 16 and the hypocycloidal tomography, the images of the 3 mm cross-sections showed similar frequency distribution. However, the Orthophos Program 16 did not produce diagnostically useful images when the cross-sections were imaged with the surrounding parts of the specimens probably because of the narrow tomographic angle used for this program. These images had strong low to medium frequency components compared with the gold standard images. These results suggest that diagnostically more useful images with the Orthophos might be obtained by increasing the tomographic angle.

Aged↗
PubMed1994

Modulation transfer function of a digital dental x-ray system.

An impulse train method to control aliasing was used to measure the modulation transfer function of a digital dental x-ray system (RVG 32000 ZHR, Trophy Radiologie, Vincennes, France). The detector of this system is composed of an intensifying screen, a fiber optics taper, and a charged couple device chip. The modulation transfer function could not be measured by impulse method such as the line spread function or edge response function because of aliasing from undersampling of the digital system. The system modulation transfer function was difficult to recover at the spatial frequencies smaller than the Nyquist frequency. The modulation transfer function beyond the Nyquist frequencies was impossible to recover in this study.

Fourier Analysis↗
PubMed1993

Detector response and exposure control of the RadioVisioGraphy system (RVG 32000 ZHR).

The RadioVisioGraphy system (RVG 32000 ZHR) was studied with respect to some physical properties including the precision and linearity of the exposure control and the detector response to x-rays. The x-ray unit was found to yield repetitive exposures that are precisely controlled by the CCX timer. A "preheat" and an "after exposure" period were noticed, and their resulting x-ray exposures were measured. Two RVG detectors were compared for their responses with x-rays. The differences between the detectors were insignificant. However, inhomogeneous detector responses were found in both of the detectors; with the same exposure, the central parts of the detectors yielded lower pixel values than the peripheral parts. A calibration equation was developed to correct for the inhomogeneity.

Radiation Dosage↗
PubMed1993

Comparison of panoramic and intraoral radiography for the diagnosis of caries and periapical pathology.

Panoramic and intraoral radiographs from 400 consecutive patients were compared for their ability to demonstrate periapical pathology and caries. Two hundred panoramic radiographs were exposed with the rotational technique and 200 with the intraoral X-ray tube technique. Periapical osteolytic and sclerotic lesions as well as approximal caries were recorded independently by two observes. Agreement with intraoral radiographs for periapical osteolytic lesions was, on average, 63% for the rotational and 55% for the intraoral X-ray tube technique and for sclerotic lesions 40% and 36%, respectively. The agreement varied with tooth type and lesion size. When teeth without periapical lesions were also included in the comparisons, the values for agreement were over 96%. Interobserver agreement for periapical osteolytic lesions was 61% for the rotational and 56% for the intraoral X-ray tube technique. The corresponding values for sclerotic lesions were 29% and 23%. Intraobserver agreement for periapical osteolytic lesions was 71% for the rotational and 67% for the intraoral X-ray tube technique. The corresponding values for sclerotic lesions were 46% and 56%. Agreement with intraoral radiographs for enamel caries was, on average, 21% for the rotational and 27% for the intraoral X-ray tube technique and for dentinal lesions 44% and 53%, respectively. When caries-free approximal surfaces were also included in the comparisons, the values for agreement were over 95%. It is concluded that panoramic and intraoral radiography perform equally well as diagnostic tools for the detection of periapical lesions, although the results are not identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Image resolution in the midsagittal plane of the Orthopantomograph-10 using Lanex regular and T-Mat G screen-film combination.

Image resolution was measured in the midsagittal plane of the Orthopantomograph-10 with the use of Lanex regular and T-Mat G screen-film combination. A thin platinum edge phantom was used to obtain images for calculation of the edge response functions. Subsequently, line spread functions and modulation transfer functions of the system were calculated. Noise equivalent passband values, which were expressed in line pairs per millimeter, were derived to describe the image resolution. The noise equivalent passband values derived in this study were generally smaller than those reported in a previous study. The width of the image layer was found to be uniform at different vertical levels.

Humans↗
PubMed1992

Decision making in radiographic imaging.

In 1987, the U.S. Department of Health and Human Services issued guidelines for prescription of dental radiographic examinations, and although these recommendations have been reprinted in several widely circulated publications, it seems that the adoption of these guidelines is far from common, even among U.S. dental schools. The recommended criteria are founded on the existing knowledge of prevalence and progression of the most common dental diseases and on the fact that occult diseases within the jaws are uncommon. There are, however, other factors that may influence the decision on the time and extent of a radiographic examination, which may lead to deviations from the suggested guidelines. These factors include: education, peer influence, patient's preference, legal considerations, the dentist's field of interest or specialty, the training of the staff, and practice routine. The diagnostic interpretation of radiographs is far from a completely objective process, even if it is a question as simple as the presence and/or extent of a carious lesion. Numerous studies have shown a large variation among observers, both with regard to the occurrence and extent of carious lesions, in bite-wing radiographs. Caries diagnosis is only one example of many situations where significant observer variation is found. The more complex the diagnostic task, the more variation can be expected. The effect of observer variation on treatment decisions regarding carious lesions is used as an example of the problems encountered daily in the dental practice.

American Dental Association↗
PubMed1991

Agreement between panoramic and intra-oral radiography in the assessment of marginal bone height.

Panoramic and intra-oral radiographs from 400 consecutive patients were evaluated for the assessment of the marginal bone height. Two hundred panoramic radiographs were exposed with the rotational technique and 200 with the intra-oral X-ray tube technique. Measurements of the approximal marginal bone level were independently performed by two observers. Complete agreement between panoramic and intra-oral radiographs was, on average, obtained in 55% and 49% of the sites, respectively. When the criterion for agreement was widened to include recordings with a difference of +/- 1 mm, the agreement was on average 87% irrespective of the techniques compared. The agreement varied with tooth type and severity of the marginal bone loss. Angular bony defects and furcation involvements were recorded separately. For angular bony defects there was a variation in agreement from 33% to 46% for the rotational technique and from 35% to 51% for the intra-oral X-ray tube technique depending on localization. Furcation involvements of the molars were equally recorded in 60% and 59%, respectively, but in only 12% and 28% for the upper premolars. Interobserver agreement was 58% for the intra-oral radiographs, 60% and 59% for the two panoramic techniques. Mean intra-observer agreement was 68%, 66% and 68%. It is concluded that panoramic radiography can often be used for the assessment of marginal bone loss alone, supplemented when necessary by intra-oral radiographs.

Adolescent↗
PubMed1989

Smoking habits and tooth loss in Swedish women.

A longitudinal population study of 1462 women, aged 38-60, was started in Gothenburg, Sweden, in 1968-69. In univariate analysis of the results from 1968-69, smokers were found to have a significantly lower number of remaining teeth than non-smokers had. The differences between smokers and non-smokers with respect to edentulousness and number of remaining teeth was further accentuated 12 yr later. The mean number of teeth lost during the 12-yr follow-up period was 3.5 among smokers and 2.1 among non-smokers, i.e. 67% higher among smokers than among non-smokers. The associations were independent of age, education, socio-economic group, marital status, frequency of toothbrushing, and frequency of visits to a dentist. It is concluded that smoking seems to play an important role as far as tooth loss is concerned.

Adult↗
PubMed1989

Comparison between panoramic and periapical radiography in the diagnosis of periapical bone lesions.

The diagnostic accuracy of panoramic and periapical radiography was compared by five oral radiologists who assessed the periapical status of 117 teeth evenly distributed throughout the jaws with a 50% probability that either an osteolytic or sclerotic lesion was present. Receiver operating characteristic (ROC) analysis demonstrated no overall significant difference between panoramic and periapical radiography. However, for sclerotic lesions and for all lesions on maxillary premolars and mandibular molars periapical radiography was significantly superior (P less than 0.001); it was also superior for osteolytic lesions in the maxilla as well as for the lesions on mandibular premolars but with a smaller significant difference (P less than 0.05).

Adult↗