PubMed Health⌕ Search

Biomedical subjects

R G Waggener

Publications and source records attributed to R G Waggener.

At least 19 recordsLinked to original sources
PubMed1992

CT reconstruction algorithm for a dental panoramic x-ray unit.

A variable Jacobian and weighted backprojection algorithm, used for medical CT, was adapted to perform CT reconstructions on data obtained with a dental panoramic x-ray unit. A detector array, fitted to the unit for the purpose of acquiring digital panoramic radiographs, was used to collect the data. Compensations were made for the incomplete (230 degrees) rotation of the panoramic x-ray unit, the non-fixed centre of rotation, the irregular rotation of the x-ray target and detector, and the resulting variances in magnification. The algorithm was tested on mathematically simulated phantoms and on acquired data. Reconstruction of simulated data proved the success of the algorithm. Real data reconstructions showed some defects as a result of inaccuracies in quantifying the experimental panoramic device.

Algorithms↗
PubMed1989

Spatial resolution requirements for digitizing dental radiographs.

A study was performed to determine the appropriate spatial resolution for digitizing and transmitting dental radiographs with the KODAK EKTASCAN, a computer-based digital enhancement and transmission system. Periapical, bitewing, and panoramic radiographs were digitized in three formats representing varying spatial resolution parameters. Eight viewers used a 5-point rating scale to evaluate the detectability of periapical pathosis on the periapical images, of proximal surface caries on the bitewing images, and of various bony abnormalities on the panoramic images. Receiver operating characteristic curves were generated, and the results of the periapical, bitewing and panoramic experiments were presented as trapezoidal and maximum likelihood receiver operating characteristic curve areas. The results of this study indicate that digital images of dental radiographs provide adequate diagnostic accuracy for evaluating the presence of periapical pathosis, proximal surface caries, and specified bony abnormalities. The digitization parameters established for the KODAK EKTASCAN provide a guide for digitizing dental radiographs on other commercially available digital image-processing systems.

Computers↗
PubMed1978

A method for rapid determination of the energy of electron beams from medical linear accelerators.

A method has been developed using a Varian Clinac-18 LINAC for the rapid determination of electron beam energy for clinically used linear accelerators. The method involves measuring the ionization values in a water or polystyrene phantom with an ion chamber at two predetermined depths. Then with predetermined Bremsstrahlung "tail" values which are presented here or which can be developed by the user, the practical range, Rp can be measured. With the Rp, the effective surface energy Eo of the electron beam can be determined by the Markus range-energy formula. Thus, by measuring just two depth ionization values, one is quickly able to determine the Eo of an electron beam without plotting a full depth ionization curve.

Electrons↗
PubMedDate not supplied

Estimation of chemical composition and density from computed tomography carried out at a number of energies.

A method is presented by whichcomputed tomography scans carried out at a number of energies may be utilized to obtain cross-sectional images of density and atomic number in addition to the conventional array of linear attenuation coefficients. This type of analysis has been carried out for various substances of biological relevance. Computer simulated reconstructions of clinical situations suggest that the method shows promise for providing additional diagnostic information and might dispense to some extent with the necessity of injecting contrast agents into the patient.

Autoanalysis↗