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Biomedical subjects

G C Sanderink

Publications and source records attributed to G C Sanderink.

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

Dose reduction of two digital sensor systems measuring file lengths.

OBJECTIVE: The aim of this study was to determine the effect of dose reduction on the image quality of two sensor systems with automatic greyscale adjustment. STUDY DESIGN: Two digital sensor systems, Sidexis (Siemens, Bensheim, Germany) and Digora (Soredex, Helsinki, Finland), were tested. The image quality of the systems was determined by comparing lengths of endodontic files (025, 020, 015, and 010 files) and a premolar root in the digital images with lengths on conventional radiographic films. For the experiments the exposure was changed to 100%, 50%, 25%, 12.5%, 6.25%, and 3.125% of that for Ektaspeed films. RESULTS: The lengths of 025 and 020 files and the premolar root in the digital images were comparable with the lengths on films even if the exposure was reduced to 6% of that used for Ektaspeed films. The lengths of 015 files reduced as the exposure was reduced. The lengths of 010 files were significantly shorter than the lengths on films. CONCLUSIONS: With the systems tested, a dose reduction of approximately 95% compared with Ektaspeed films is possible to determine the lengths of a premolar root and 025 and 020 files. For thinner objects a dose reduction is questionable.

Analysis of Variance↗
PubMed1995

[Are conventional dental x-ray films a thing of the past?].

Dental x-ray film is still the most important medium for the detection and storage of x-ray images. However, just as the use of computers cannot be stopped, digital techniques will take over the role of dental x-ray films in dental radiology.

Humans↗
PubMed1994

A simple method for measuring MTF in direct digital intraoral radiography. Technical note.

Conventional methods for measuring the modulation transfer function require the exposure of a narrow slit or straight edge followed by computationally intense data analysis. An alternative method applicable to digital systems uses the standard deviation of gray levels within different frequency regions of a bar pattern. To verify that this method gave reliable results, measurements performed for two systems for intraoral radiography with the use of this method have been compared with modulation transfer function values calculated from Fourier transformations of line spread functions measured for the two systems. The almost identical results confirm the consistency of both sets of modulation transfer function measurements and demonstrate the utility of the bar pattern method for performing rapid measurements.

Fourier Analysis↗
PubMed1994

Resolution as defined by line spread and modulation transfer functions for four digital intraoral radiographic systems.

Line spread functions for four commercially available systems for direct digital intraoral radiography were determined from images of a slit of negligible width. From the fitted line spread functions presampling modulation transfer functions were calculated. The four systems were the Sens-A-Ray (Regam Medical System AB, Sundsvall, Sweden), the VIXA/Visualix (Gendex, Chicago Ill.), the RVG (Trophy Radiologic, Paris, France), and the Flash Dent (Villa Sistemi Medicale srd, Buccinasco, Italy). Digital intraoral radiography is in a state of rapid development, and detectors as well as computer hardware and software are continually modified and improved resulting in successively changing system parameters. As this occurs the present work provides a method that may be used to determine comparable data on future systems.

Electronics, Medical↗
PubMed1994

Image quality of direct digital intraoral x-ray sensors in assessing root canal length. The RadioVisioGraphy, Visualix/VIXA, Sens-A-Ray, and Flash Dent systems compared with Ektaspeed films.

The Trophy RadioVisioGraphy model 32000 system in Normal Mode, the Trophy RVG-PC in Normal and Archive Mode, the Gendex VIXA/Visualix, the Regam Sens-A-Ray, and the Villa Flash Dent in High-Resolution Mode and Normal Mode were compared with respect to the visibility of endodontic files. Kodak Ektaspeed film served as the reference. An acrylic embedded human skull was prepared for taking radiographs with endodontic files (Kerr files size 10 and size 15) on full root length and 1.5 mm short in upper and lower premolars and molars. Possibilities for enhancement of the digital images were not studied. Receiver operating characteristics curves were derived and the areas under the curves were averaged and compared using Student's t test statistic (p < 0.05). Kodak Ektaspeed film gave acceptable results for both file sizes. Both Trophy RVG units in Normal Mode and the Regam Sens-A-Ray system gave results above the areas under the curves equals 0.95 for the size 15 files. For the size 10 files the values of the areas under the curves of all sensors systems were below this threshold. It is concluded that both RVG units in Normal Mode and the Sens-A-Ray system render a comparable result with conventional radiography in determining root canal length with the use of a size 15 files. All sensor systems were unacceptably inferior to film images when size 10 files were used.

Dental Pulp Cavity↗
PubMed1993

Imaging: new versus traditional technological aids.

Until recently film has been the only medium on which to register radiographic images. Despite tremendous increase in sensitivity, the most sensitive films available at present still have a higher resolution than the eye, although at the cost of a more grainy image. Film speed for intraoral films seems to have reached its maximum unless a lower quality is accepted. Other methods, well established in medicine, like digital radiology, teleradiography and picture archiving and communication systems have started to make inroads into dentistry. In 1987 the first intraoral sensor and display processing unit, with the x-ray image on a television monitor, became available as an alternative to conventional radiography. Since then the sensors have improved enabling digital post-processing to enhance details of interest for different diagnostic problems. A dose reduction of approximately 80 per cent compared to D-speed films can be obtained. The sensitive area of the sensor is still relatively small compared to conventional films, resulting in difficulties in positioning it. However new systems approach the image quality of conventional E-speed film. Instant availability of the images is a major attractive benefit of these new technologies. With the arrival of direct digital acquisition of maxillofacial radiographs an 'electronic office' is needed to derive the full benefit from this technology, including local and distant image transfer. Digital imaging in dentistry is presently still in a relatively primitive state although it is anticipated that by the middle of this decade considerable improvement will have been achieved making digital image equipment feasible for the general practitioner.

Equipment Design↗
PubMed1991

The origin of a case of severe image distortion in rotational panoramic radiography.

A rotational panoramic radiograph with an apparently severe error in patient positioning was obtained. There was no image in the middle part of the film which was black. The origin of this severely degraded image is explained by simulating the position of the jaws in relation to the path of the beam during the exposure. The error was caused by incorrect positioning of the patient so that the X-ray beam actually passed outside the jaws when the anterior region was radiographed. Similar misalignment could be reproduced using a phantom head which had been displaced 3 cm lateral and 1 cm behind of the ideal position.

Diagnostic Errors↗
PubMed1990

Applicability of simultaneous rotational panoramic radiography.

The position of the image layer in simultaneous multilayer rotational panoramic radiography using films placed parallel in one cassette was calculated for curved and flat cassettes. Parallel films do not result in parallel layers. The use of a flat cassette results in minor shifts in layer position compared with a curved cassette. The position of the film required to produce parallel curved layers was calculated. Using curved cassettes, extraordinary modifications of the film position would be needed for the anterior region. The use of flat cassettes appears to be practically impossible. Routine use of this technique is therefore unlikely.

Computer Simulation↗
PubMed1989

The effect of system parameters on resolution in rotational panoramic radiography. A mathematical analysis.

The unsharpness in rotational panoramic radiography is the combined effect of motion unsharpness, screen-film unsharpness and geometrical unsharpness. A computer program was written to calculate the noise equivalent passband (Ne) from the modulation transfer function (MTF) of each of the three sources of unsharpness in both the horizontal and vertical dimensions for a typical panoramic machine. Effects on system resolution resulting from changing the size of the focal spot, the screen-film combination, the width of the beam, and the effective projection radius were computed and the interaction of the various parameters was evaluated. Data of this type is essential for evaluation of system performance and for optimizing the operation of panoramic systems.

Computers↗
PubMed1987

The variation in appearance of the hard palate and the nasal floor in rotational panoramic radiography.

This study was performed to find the origin of the radiopacity in the region of the hard palate and to explain the variability in appearance of this radiopacity in panoramic radiographs. It could be demonstrated, with the use of metal markers attached to a dry human skull, that the radiopacities seen in the region of the hard palate represent the junction of the nasal septum and the hard palate and the junction of the maxillary sinus to the hard palate. The appearance of one or two lines depends on the angulation of the skull. A more inclined (chin-down) position of the skull produces two lines, whereas a chin-up position results in a superimposition of the two lines and produces only one line. The image of the junction of the bony septum and palate is unsharp because of the greater distance from the focal plane. The junction of the maxillary sinus to the hard palate is closer to the image layer and will appear as a sharp line.

Cranial Sutures↗
PubMed1986

Application of a photodiode in dental radiology.

A photodiode in a light-tight housing was used as an x-ray detector. Calibration against a standard ionization chamber showed that, for the range of radiation qualities used in dentistry, its output was a reliable measure of the rate of exposure. Photodiodes are available in very small sizes and can be used intraorally. The feasibility of automatic exposure control for intraoral radiography was considered. Measurement of transmission fractions through the mandible with various radiation qualities resulted in a numerical evaluation of radiation risk approximated by the absorbed dose.

Equipment Design↗