Biomedical subjects

D Plenkovich

Publications and source records attributed to D Plenkovich.

4 recordsLinked to original sources

PubMed1995

Intramural pseudodiverticulosis of the esophagus detected on barium esophagograms: increased prevalence in patients with esophageal carcinoma.

OBJECTIVE: We tested the hypothesis that intramural pseudodiverticulosis of the esophagus is more prevalent in patients with esophageal carcinoma than in randomly selected patients who undergo esophagography for other indications. Such an association would prompt a careful search for carcinoma after esophageal intramural pseudodiverticulosis is found. MATERIALS AND METHODS: Single- and double-contrast esophagograms of 245 patients with esophageal carcinoma were retrospectively reviewed. A control group of 6400 esophagograms obtained for indications other than esophageal carcinoma was also reviewed. The statistical significance of the difference in prevalence of esophageal intramural pseudodiverticula between patients with esophageal carcinoma and the control group was tested using the chi-square test. The significance of difference between the number of esophageal intramural pseudodiverticula in patients with esophageal dilatation and the number in those without dilatation was tested using a small-sample nonparametric test. RESULTS: Intramural pseudodiverticulosis of the esophagus was found in 11 patients with esophageal carcinoma (4.5%) and in six control subjects (0.09%). Intramural pseudodiverticulosis of the esophagus was present opposite the tumor as well as both proximally and distally. The number of cases of intramural diverticulosis in patients with esophageal carcinoma and dilatation was not significantly higher than that in patients with carcinoma but without dilatation (p > .1) CONCLUSION: The prevalence of esophageal intramural pseudodiverticulosis is significantly higher in patients with esophageal carcinoma than in patients who underwent esophagography for other indications (p < .0002). This association implies increased risk of esophageal carcinoma in patients with intramural pseudodiverticulosis. Periodic surveillance of patients with intramural pseudodiverticulosis of the esophagus for esophageal carcinoma may be worthwhile.

Adult↗

PubMed1989

Electronic scanning-slit fluorography.

Scattered radiation degrades contrast and signal-to-noise ratio of an x-ray image. If an image intensifier is used as the image receptor, scattering of light photons and electrons within the image intensifier, optical system, and video camera produces veiling glare. anti-scatter grids, air gaps, and paired scanning slits have been used for rejection of scattered radiation. However, none of these methods is effective against veiling glare, because veiling glare is generated after the radiation has passed through any of these anti-scatter devices. In chapter 1 is introduced an innovative approach for highly efficient rejection of both scattered radiation and veiling glare in digital fluorography. This method has been named electronic collimation, and the x-ray imaging technique based upon it is called electronic scanning-slit fluorography. It involves replacing paired fore and aft slits for scatter rejection with only one beam-defining tantalum fore aperture. As this aperture scans across the portion of the patient to be imaged, pulsed x-ray exposures produce images which are digitized and stored in the computer memory. Since the video signal within the projection of the aperture on the image intensifier is much more intense than behind the tantalum, one can discriminate electronically between these two signals and thus eliminate the unwanted x-ray scatter and veiling glare. Such electronic collimation does not require synchronization between the slit scanning and detector readout, which makes it much simpler than alternative methods and potentially adaptable to any digital fluorography system. Theoretical considerations relevant for the construction and evaluation of a prototype unit for electronic scanning slit fluorography are presented in Chapter 2. This chapter consists of four sections. In the first section 'Principles of image detection' the concepts of quantum efficiency and detective quantum efficiency (DQE) are introduced as the most meaningful way to compare different methods of scatter rejection. The DQE is the fraction of incident photons that would have to be detected without additional noise to yield the same signal-to-noise ratio as is actually observed by the detector in question. The second section 'Effect of scatter' contains the derivation of the functional dependence of the image contrast and the signal-to-noise ratio on the scatter-to-primary ratio. This derivation yields the scatter degradation factor (SDF) which is the fraction of available primary beam contrast due to the presence of scatter.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Scatter rejection by electronic collimation.

An electronic scanning-slit technology is under development which involves replacing paired fore and aft slits for scatter rejection with only one fore slit. As the slit scans across the portion of the patient to be imaged, pulsed x-ray exposures produce images of the slit in successive positions, which are digitized and stored in computer memory. Software techniques are used for tracking the slit image, and discriminating against scatter and veiling glare lying outside the slit image. Such "electronic collimation" does not require synchronization between the slit-scanning and detector readout, which makes it much simpler than alternative methods and potentially adaptable to any digital fluorography system. The performance characteristics of a prototype unit are described and images of a low-contrast phantom are presented.

Angiography↗

PubMedDate not supplied

Electronic scanning-slit fluorography: design and performance of a prototype unit.

Electronic scanning-slit fluorography involves replacing paired fore and aft slits for scatter rejection with only one beam-defining tantalum fore aperture. Since the video signal within the projection of the aperture on the image intensifier is much more intense than behind the tantalum, one can discriminate electronically between these two signals and thus eliminate the unwanted x-ray scatter and veiling glare. The general features of a prototype unit are described along with the rationale for the choice of design factors employed. Imaging time of 1-2 s has been achieved using multiple scanning slits. Small focal-spot size and large number of pixels are favored for higher dose utilization, shorter imaging time, and lower x-ray tube loading, as well as for better spatial resolution. Images of a chest phantom show better visibility of low-contrast details, especially in poorly penetrated areas, when compared with the image obtained and displayed under the same conditions, but using a conventional grid to reject scattered radiation.

Biophysical Phenomena↗