Biomedical subjects

F E Eraso

Publications and source records attributed to F E Eraso.

5 recordsLinked to original sources

PubMed1999

Clinical and in vitro film quality comparison of manual and automatic exposure control in panoramic radiography.

OBJECTIVE: Automatic exposure control has been used successfully in medicine to improve image quality and reduce the number of retakes necessitated by inadequate operator selection of exposure factors. The purpose of this study was to assess the influence of automatic exposure control on panoramic image quality. STUDY DESIGN: A total of 352 patients were imaged with either the OP 100 or the Orthophos Plus panoramic machine. An expert consensus panel judged film quality using a 5-point scale. Differences in quality that would have resulted from the use of operator-determined exposures were calculated through use of an algorithm validated with test images of a human phantom. RESULTS: McNemar's test demonstrated significant improvements in quality with automatic exposure control (P = .001) in comparison with manual exposure control. No quality difference was found between the 2 machines (P = .9661). Manual exposure selection by oral and maxillofacial radiology residents was better than selection by technologists and assistants (P = .006). CONCLUSIONS: This study confirms the utility of automatic exposure control for panoramic radiography.

Adult↗

PubMed1998

Characteristics of the Orthopantomograph OP 100.

OBJECTIVE: To investigate empirically the imaging characteristics of the Orthopantomograph OP 100 and compare them to the average form of the dental arch. METHODS: Repeatable radiographs were taken of a lead resolution grid positioned at 1 mm increments along known angular intervals of the projected X-ray beam. Focal trough thickness was determined by visibility of the 1.5 lp mm-1 resolution limits. The path of the effective rotation center was determined using a film positioned at right angles to the slit beam. The vertical magnification and horizontal magnification and distortion index, corrected for the position of the tomographic layer, were calculated using a reference object placed at various resolution limits of the focal trough. The beam projection angle was calculated with respect to the central plane of the focal trough and the average dental arch shape compared with the average proximal contact angle. RESULTS: The maximum resolution observed at the central plane of the focal trough was 5 lp mm-1. The width of the focal trough varied from 17 mm in the anterior region to 44 mm in the posterior region. The path of the effective rotation center was found to translate between three fixed centers of rotation, with the effective anterior projection radius of 24 mm. The vertical magnification factor within the focal trough showed a linear increase along the beam path from 1.24-1.37 and the horizontal magnification varied from 1.01-1.63. The distortion index varied from 0.84-1.24. The beam projection angle increased from 90 degrees anteriorly to 115 degrees in the premolar area with respect to the central plane of the focal trough and from 90 degrees anteriorly to 110 degrees in the premolar area compared with the average dental arch. CONCLUSIONS: The OP 100 provides a focal trough conforming well to the overall geometry of the dental arch and provides adequate spatial resolution.

Dental Arch↗

PubMed1996

Teledentistry: protocols for the transmission of digitized radiographs of the temporomandibular joint.

Tomograms of the temporomandibular joint were digitized in three different formats using a PC-based system. The image resolution for various projections was determined at different camera-film distances. Three series of images were transmitted by telephone, and transmission times were measured. The original radiographs, the digitized images, the transmitted images and the transmitted-and-printed images were presented to 10 observers, who were asked to rate image quality. No difference in image quality was found between the initial digitized and the transmitted images. However, transmitted and transmitted-and-printed images were of significantly lower quality than the original radiographs or the digitized images viewed on a computer monitor. Transmission time was reduced significantly (50%) by cropping the images before transmission. The image quality of individual radiographs was better than radiographs formatted as a series.

Analog-Digital Conversion↗

PubMed1996

Technical note. Modulation transfer function analysis of a newly revised rotational panoramic machine.

OBJECTIVES: To determine the modulation transfer function (MTF) and noise equivalent passband (NE) values for a newly revised rotational panoramic X-ray machine, the PC-1000 (Panoramic Corp., Fort Wayne, Indiana, USA). METHODS: Images of a 10 microns test slit were taken at various locations along the X-ray beam projection path using a Lanex Regular/T-Mat G image receptor. Line spread functions were obtained at specific beam paths by scanning slit images with a microdensitometer. RESULTS: MTF values were highest around the central plane of the image layer, with a maximum near the centre of 0.25 at 4 cycles/mm. The NE values near the central plane of image layer were 1.4 cycles/mm. MTF and NE values in the anterior region were low, 0.2 and 1.2, respectively. The width of the image layer was narrower in the anterior and wider in the posterior segments. Rapid decreases in MTF and NE values were found on the X-ray tube side compared with the receptor side of the central plane. Using a spatial frequency of 0.25 MTF the shape of the image layer was coincident with that determined visually. CONCLUSION: On the basis of the MTF and NE values the image resolution produced by this machine is considered acceptable for panoramic dental radiography.

Mathematics↗

PubMed1996

Low-cost teleradiology for dentistry.

The performance of a low-cost teleradiology system was studied. The time needed for radiographic transmission between computers and the image integrity following transmission were measured. The image resolution was analyzed with a line-pair test chart. Images were transmitted through computers that had a video-processing board and a modem at both the transmission and receiving sites. Intraoral radiographs were captured with a black and white charge-coupled device camera. The time required for image transmission was less than 1 minute (46 to 56 seconds), an effective transmission speed of 1.73 kbyte/s (13.9 kbit/s). No changes were observed in pixel value distributions; hence, there was no loss of image detail. The maximal resolution of the system was 4 line-pairs/mm. The performance of the teleradiology system demonstrated its potential as an effective, low-cost telenetwork for dentistry.

Diagnosis, Computer-Assisted↗