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Topographic classification is a nonlinear technique used to enhance nuclear medicine images for tumor detection. Second-order directional derivatives are computed at each pixel location after performing a least-squares fit of the underlying surface using a bivariate cubic polynomial. The eigenvalues and their corresponding eigenvectors computed from the Hessian matrix determine which topographic feature is assigned to the image pixel. Parameter selection for the mask size, curvature threshold, and angle thresholds are chosen to yield the "best" classified image. The classifier is applied to clinical images of cancer patients provided by the Department of Nuclear Medicine at the University of Arizona. Background noise associated with the photon-starved data is suppressed using a Difference-of-Gaussians (DOG) filter prior to pixel classification. Results indicate the feasibility of using this technique to isolate possible tumor sites which will assist the clinician during patient examination.

A thermometry system for use during ultrasound hyperthermia treatments was developed to provide fast and reliable temperature measurements such that transient temperatures from multi-sensor thermocouples could be measured. It was also intended to provide electrical isolation for patient safety when bare thermocouple sensors were used in order to reduce artifacts. The system hardware development involved fabrication of a high precision temperature measurement box which was electrically isolated from, by an opto-isolation unit, and interfaced with, an 386-20 MHz personal computer. The system software development involved a two point calibration program for each thermocouple probe to be used with the system, and a sensor locating program to rapidly identify the probe locations immediately prior to treatment. A single scan temperature reading speed of 0.2 sec for all 112 thermocouple sensors with an average accuracy of ±0.05°C under normal operating conditions (ambient temperature 22°C to 28°C) was achieved. A probe to earth ground leakage sink current of 75 μA and a leakage source current of less than 10 μA was attained.

Let $(X,\chi)$ be a measurable space, let $M = M(X,\chi)$ be the space of nonnegative, bounded measures on $(X,\chi),$ let N be the subset of M with integer values, let ${\cal M}$ be the smallest $\sigma$-algebra on M with respect to which the coordinate functions$$\{f\sb A :M \to \Re\vert f\sb A (\mu) = \mu(A),\forall A \in \chi, \forall\mu \in M\}$$are measurable, and let ${\cal N}$ be the $\sigma$-algebra on N induced by its inclusion in $(M,{\cal M})$. A measurable map $\nu$ from a complete probability space ($\Omega,{\cal E},P)$ to $(M,{\cal M})$ is a random measure of $(X,\chi)$; such a map with range in $(N,{\cal N})$ is a point process. Let $\mu$ be a finite positive measure on $(X,\chi)$, random measure $\nu$ is a Poisson point process on $(X,\chi)$ with mean or directing measure $\mu$ if for all $A \in \chi\ \nu(A;\cdot)$ is a Poisson random variable with mean $\mu(A)$, $$P(\{\omega\vert\nu(A;\omega) = k\}) = e\sp{-\mu(A)}{\mu(A)\sp k\over k!},\ k = 0,1,2,\... ,$$and for any finite collection of pairwise disjoint sets $\{A\sb1,A\sb2,\...,A\sb p\} \subset \chi$ the random variables $\{\nu(A\sb1;\cdot),\nu(A\sb2;\cdot),\...,\nu(A\sb p;\cdot)\}$ are independent,$$P(\cap\sbsp{i = 1}{p}\{\omega\vert\nu(A\sb i;\omega) = k\sb i\}) = {\prod\limits\sbsp{i = 1}{p}}\ P(\{\omega\vert\nu(A\sb i;\omega) = k\sb i\}).$$ Following Peskin, Tranchina, and Hull, we use a Poisson point process to model the occurrence of $\gamma$-photons produced by the decay of a radioactive marker in the tissue of a given patient for a diagnostic procedure in nuclear medicine. The directing measure of the process represents the distribution of the marker during the scan; this directing measure can be estimated through a linear filtering technique. We prove the existence of a continuous, linear, least-squares filter and the approximability of this filter by a sequence of discrete filters of the kind developed by Peskin, Tranchina, and Hull. We also demonstrate techniques for filtering and filter error estimation at high resolution / acase@tulane.edu

Chinese hamster ovary cells were synchronized at the G$\sb1$/S boundary of the cell cycle and labeled for 10 min with $\sp{125}$I-iododeoxyuridine. Samples were frozen for decay accumulation between 15-480 min after labelling. Cells frozen within 1 h after labeling yielded a low LET survival response with a pronounced shoulder and a large D$\sb0$ (255 decays/cell). With longer chase periods the shoulder and the D$\sb0$ decreased progressively and cells harvested 5 h after labeling exhibited a high LET survival response (D$\sb0$: 65 decays/cell). If DNA is assumed to be the sole target for radiation-induced death, these results indicate that DNA maturation increases radiation damage to DNA or reduces repair. Alternatively, if radiation death involves damage to higher-order structures in the nucleus, the findings suggest that newly replicated DNA is not attached to these structures during the initial low LET period, but $\sp{125}$I starts to induce high LET effects as labeled DNA becomes associated with the target structure(s). On balance, our data favor the latter interpretation. / In related experiments, exponentially growing cells were labeled with $\sp{125}$I-iododeoxyuridine for 12 h. Mitotic cells were selected, plated for cell cycle traverse, and harvested during successive stages of the cell cycle for decay accumulation. $\sp{125}$I damage during G$\sb1$ resulted in shoulderless exponential survival curves with a D$\sb0$ of 60-65 decays/cell. Resistance to $\sp{125}$I decays increased as cells progressed through S and the survival curves of cells in late S/G$\sb2$ were characterized by a pronounced shoulder and a D$\sb0$ of 127-139 decays/cell. These findings suggest that the primary target for radiation death is duplicated during S with G$\sb1$ cells containing one set and G$\sb2$ cells two sets of targets. Dual targets, although located within a single cell, act independently, as if already distributed between separate daughter cells. Analysis of the data suggests that the emergence of a shoulder and doubling of the D$\sb0$ in late S/G$\sb2$ cells represents an artifact of the colony formation assay which systematically overstates cell survival when intracellular target multiplicity exceeds 1. / Source: Dissertation Abstracts International, Volume: 53-03, Section: B, page: 1235. / Major Professor: Kurt G. Holer. / Thesis (Ph.D.)--The Florida State University, 1992.

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