Biomedical subjects

B G Fallone

Publications and source records attributed to B G Fallone.

60 records · Page 4Linked to original sources

PubMedDate not supplied

A logit model for the modulation transfer function of screen-film systems.

An empirically derived logit function is proposed to describe the modulation transfer function of x-ray screen-film systems. Simple and exact weighted linear regression analyses are performed to characterize the function and to describe the data within experimental accuracy. Calculations comparing the proposed function and the complementary error function (probit) representations of the modulation transfer function are given and discussed.

Models, Theoretical↗

PubMedDate not supplied

Approximations to saturation curves in gas-filled parallel-plate ionization chambers.

Saturation curves were measured for air and nitrogen in the exposure rate range from approximately 1 to approximately 500 R/min. Because of the differences between the ion-ion versus electron-ion recombination processes, the air and nitrogen saturation curves differ considerably even when measured under identical chamber and exposure rate conditions. A comparison between our experimental data and various approximations to saturation curves in air, developed by others, is given. It is then shown that the air saturation curve can be approximated by a sum of three simple exponential functions.

Air↗

PubMedDate not supplied

A linear-quadratic fit for saturation curves obtained under continuous irradiation of parallel-plate ionization chambers.

An approximation to saturation curves of parallel-plate ionization chambers for various gases under continuous irradiation is given. The proposed fit asymptotically agrees with Mie's set of equations for the low and the high collection efficiency regions. It is shown that this fit which, for gases containing electronegative atoms, is dependent upon a parameter obtained from physical constants agrees with measurement and with values calculated from Mie's set of equations. However, for gases containing nonelectronegative atoms, it is shown that an additional experimental parameter is required to fit the measurements.

Gases↗

PubMedDate not supplied

A novel algorithm for the edge detection and edge enhancement of medical images.

A novel algorithm, histogram shifting (HS) is presented, which performs edge detection or edge enhancement with the choice of two parameters. The histogram of a region surrounding each pixel is found and translated toward the origin, resulting in the new pixel value. Images from a variety of medical imaging modalities were processed with HS to perform detection and enhancement of edges. Comparison with results obtained from conventional edge detection (e.g., Sobel) and with conventional edge-enhancement algorithms is discussed. HS appears to perform the edge-detection operation without introducing "double-edge" effects often obtained with conventional edge-detection algorithms. HS also appears to perform edge enhancement without introducing extensive noise artifacts, which may be noticeable with many edge-enhancement algorithms.

Algorithms↗

PubMedDate not supplied

Contrast enhancement of portal images by selective histogram equalization.

Because of the high energy of the treatment beam, contrast of portal verification films is very poor. A simple contrast enhancement technique is described which we have labeled selective histogram equalization (SHE), to improve visualization of double-exposure portal images and this facilitate the beam verification process. The technique performs separate histogram equalization on the treatment- and open-field sections of double-exposure portal images. Delineation of the treatment field edge and separation into two regions is performed automatically for off-line portal radiographs by a strategic combination of Sobel filtration and morphological processes. Analyses of images processed by SHE and other adaptive histogram equalization techniques indicate that SHE produces improved contrast enhancement with minimal addition of noise or artifacts, thus simplifying the beam verification procedure. The simple implementation of an automatic SHE process with on-line portal systems is also discussed.

Algorithms↗

PubMedDate not supplied

Technique to improve lateral cervico-thoracic radiographs.

Lateral radiographs taken during radiotherapy simulation of the upper thoracic and lower cervical region are often of poor quality because of the difference in separation seen by the incident beam. A simple method of compensating for this is the application of a thin foil of lead on the simulator that obscures the light field in the superior portion of the field. This technique has the advantage of being simple, fast and easily reproducible.

Humans↗