Biomedical subjects

A L Hall

Publications and source records attributed to A L Hall.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Generalized image combinations in dual KVP digital radiography.

Dual energy basis decomposition techniques apply to single projection radiographic imaging. The high and low energy images are non-linearly transformed to generate two energy-independent images characterizing the integrated Compton/photoelectric attenuation components. Characteristic linear combinations of these two basis images identify unknown materials, cancel known materials, and generate synthesized monoenergetic images. The problems of intervening materials and material displacement are solved in general for a wide class of clinical imaging tasks. The basis projection angle identifies one from a family of energy selective imaging tasks, and such performance measures as the contrast enhancement factor (CEF) and signal to noise ratio (SNR) are expressed as functions of this angle. Algorithms for the decomposition of high and low energy measurements are compared and experimental images are included.

Computers↗

PubMedDate not supplied

The technical characteristics of matched filtering in digital subtraction angiography.

The technical characteristics of a new digital fluorographic image processing method called matched filtering are presented. This technique, a type of extensive temporal integration, takes a weighted sum of images acquired during passage of a contrast bolus through some area of interest. The weight of each image is governed by the magnitude of the contrast bolus in that image. An essential requirement of the matched filter is that its integral be zero. It is shown for equal exposure rates and typical bolus characteristics that matched filtering provides a factor of two higher signal-to-noise ratio (SNR) than conventional methods for bolus transit times of 10 s or higher. Equilvalently, matched filtering can yield images with quality comparable to conventional digital subtraction angiography (DSA) at a factor of four less patient exposure. The SNR obtained with matched filtering is shown to be within 30% of an ideal bound. Comparisons of matched filtering to standard recursive methods and simple integration are made. Experimental canine studies are presented which compare matched filtering with conventional DSA.

Angiography↗

PubMedDate not supplied

cis-hydroxyproline stimulates the growth of rat mammary carcinoma cells.

With the ever-increasing evidence that the extracellular matrix (ECM) can stimulate tumor growth, it follows that inhibiting the synthesis of tumor-derived stroma may be a potential therapeutic target of cancer progression. The proline analog cis-hydroxyproline (CHP), an inhibitor of collagen deposition, was examined for its effects on the growth of clonal tumor cells that differentially produce type IV collagen and laminin. Two separate clones derived from rat mammary carcinoma cells that produce high and low amounts of type IV collagen and laminin were injected into the flanks of nude mice. Tumors in animals receiving CHP treatment grew faster than tumors in control animals receiving saline, although statistically not significant. Furthermore, upon administration of CHP to these clones in culture, increased proliferation rates of both cell types were observed. These results show that CHP is not useful in preventing stromal development and growth of rat mammary tumor xenografts.

Animals↗