Biomedical subjects

H Roehrig

Publications and source records attributed to H Roehrig.

7 recordsLinked to original sources

PubMed1992

Performance characteristics and image fidelity of gray-scale monitors.

Gray-scale monitors are an essential element of electronic radiology, and their ability to provide images that are perceived to be identical to those available on conventional or laser-printed film is crucial to success of electronic radiology. Image fidelity is measured in physical characteristics (luminance, dynamic range, distortion, resolution, and noise) and with psychophysical techniques, including receiver operator characteristics analysis with clinical images and testing with contrast-detail patterns to determine threshold contrast. Currently, laser-printed images facilitate greater information transfer than does a gray-scale monitor because of their higher absolute luminance (500 ft-L vs 60 ft-L), greater perceived dynamic range, and better spatial resolution. In the near future, the developments of gray-scale monitors with 150-200 ft-L luminance, a display standard based on just noticeable differences, and algorithms to improve similarities between gray-scale display images and laser-printed images will help increase the acceptability of monitors as a means to make primary diagnoses.

Computer Peripherals↗

PubMed1990

Performance tests and quality control of cathode ray tube displays.

Spatial resolution, noise, characteristic curve, and absolute luminance are the essential parameters that describe physical image quality of a display. This paper presents simple procedures for assessing the performance of a cathode ray tube (CRT) in terms of these parameters as well as easy set up techniques. The procedures can be used in the environment where the CRT is used. The procedures are based on a digital representation of the Society of Motion Pictures and Television Engineers pattern plus a few simple other digital patterns. Additionally, measurement techniques are discussed for estimating brightness uniformity, veiling glare, and distortion. Apart from the absolute luminance, all performance features can be assessed with an uncalibrated photodetector and the eyes of a human observer. The measurement techniques especially enable the user to perform comparisons of different display systems.

Data Display↗

PubMed1990

Computer-simulated lung nodules in digital chest radiographs for detection studies.

Computer simulations of lung nodules overcome many shortcomings of creating radiographs using anthropomorphic nodule phantoms for lung nodule detection studies, but these algorithms can be cumbersome and involved. A simple, fast, and flexible computer program to simulate lung nodules in digital chest radiographs for detection studies is reported. To verify the realism of the simulated nodules, a psychophysical study and a statistical study were conducted. In the psychophysical study, six radiologists and four nonradiologists were asked to distinguish between 17 real lung nodules and 17 computer-simulated lung nodules shown in eight radiographs. The results show that the computer-simulated lung nodules are indistinguishable visually from real lung nodules. Using parameters from the Rose model of vision, results show that the simulated and real nodules are the same statistically. Thus, besides visual validity, statistical analysis in confirming the validity of the simulated lung nodules is included.

Computer Simulation↗

PubMed1989

Intraoperative arteriography: comparison of conventional screen-film with photostimulable imaging plate radiographs.

This prospective study compared images obtained with a photostimulable imaging plate with matched images obtained with a conventional screen-film combination in 26 patients undergoing intraoperative arteriography. Diagnostic accuracy of the two techniques was assessed objectively, and image quality was assessed subjectively. In 16 patients (62%), the radiation exposure was reduced by 50% for the imaging plate technique by decreasing the mAs level generally used for the screen-film combination. Because of the dynamic range of the imaging plate system, no repeat examinations were necessary, while 12% of the screen-film studies had to be repeated because of over- or under-penetration. Imaging plate studies required 6% more time for processing than screen-film studies. Receiver-operating-characteristic analysis indicated no difference in diagnostic accuracy between the two imaging techniques. Subjective evaluation also revealed no difference in observer preference for imaging plate or screen-film studies. The imaging plate technique is an excellent alternative to screen-film studies in the operating room.

Angiography↗

PubMed1987

Finite-length line-spread function.

In this paper we derive a formula for calculating the point-spread function (PSF) of a rotationally symmetric imaging system from measurements along a line through the image of an arbitrary separable input object. An important special case of this formula is when the input object is a finite-length slit. The set of measurements in this case is called the finite-length line-spread function (FLSF). The FLSF differs from the infinite-length line-spread function (LSF) only in the assumed finite length of the line that is input into the system. This difference between the FLSF and the LSF becomes important for imaging systems for which the PSF is large in extent and in which the isoplanatic patch is relatively small. The usual LSF-to-PSF conversion formulas cannot be applied accurately to such systems.

Fourier Analysis↗

PubMed1985

The digital radiology department of the future.

The boom in microelectronics, including cost-effectiveness, has now allowed us to consider the use of these objects to store digital images. There remains much research, development, and clinical evaluation to be done in receptor technology. Further improvements in image processing, optical laser disk storage, and optical transmission and further commercial development of display technology must take place. All of these developments are occurring simultaneously. Within 5 to 10 years, radiology departments will most likely be totally electronic, probably cost-effective, and, it is hoped, more diagnostically accurate.

Data Display↗

PubMedDate not supplied

Use of storage phosphor imaging plates in portal imaging and high-energy radiography: the intensifying effect of metallic screens on the sensitivity.

The sensitivity of storage phosphor imaging plates (SPIP) at megavolt photon energies (60Co, 6-, 10-, and 18-MV radiotherapy beams) is studied both experimentally and by Monte Carlo radiation transport calculations. In addition, the same techniques are used to investigate the intensifying effect of metal screens on the sensitivity of the SPIP. The results provide evidence that the sensitivity of the SPIPs is proportional to the absorbed energy in the phosphor layer per cGy. The spectral sensitivity is calculated for photon energies between 10 keV and 20 MeV for various SPIP-screen combinations.

Aluminum↗