In the treatment of Parkinson's disease some cases require the ablation of a specific region in the basal ganglia. The accurate localization of this region inside the patient's brain is essential and because direct visual anatomical information for such deep brain structures is not available, the surgeon has to rely on other sources of information such as MRI, CT and x-ray of the patient's brain. However these imaging techniques do not provide sufficient anatomical information, requiring the use of a subcortical brain atlas book to assist in the localization of the different structures. This way of proceeding is cumbersome and results in a certain lack of accuracy in the localization of the different brain structures. / We developed a method that aids the surgeon to obtain the sufficient anatomical information in a simpler and more accurate manner. We provide him with a segmentation of the patient's MRI scan based on the Schaltenbrand and Wahren subcortical atlas. To achieve such segmentation a volumetric version of the atlas was obtained and was then mapped to a model brain MRI using landmark matching. Using an automated tool for the three-dimensional registration of two MRI volumes the deformation transformation between the model brain MRI and the patient's brain MRI was obtained. By applying this same transformation to the volumetric atlas, we obtain a superposition of a volumetric subcortical atlas onto the MRI of the patient's brain in the stereotactic space. This method results in a more accurate localization of the surgical lesion, thus reducing the number of additional interventions which are often necessary when the results of the first procedure are shown to be unsatisfactory. The whole guidance system is now used routinely at the Montreal Neurological Institute and is part of the standard surgical procedure.

An isocentric teletherapy cobalt unit provides a viable alternative to an isocentric linac as a radiation source for radiosurgery. An isocentric cobalt unit was evaluated for its potential use in radiosurgery in three areas: (1) the physical properties of its radiosurgical beams, (2) the quality of radiosurgical dose distributions obtained with 4 to 10 non-coplanar arcs, and (3) the accuracy with which the radiosurgical dose can be delivered. In each of these areas the 10 MV beam of a linear accelerator served as a standard for comparison. / The difference between the 80%--20% penumbras of the radiosurgical fields of the cobalt-60 and 10 MV photon beams is remarkably small, with the cobalt-60 beam penumbras on the average only about 0.7 mm larger than those of the linac beam. Differences between the cobalt-60 and 10 MV plans in terms of dose homogeneity within the target volume and conformity of the prescribed isodose volume to the target volume are also minimal, and therefore of limited clinical significance. Moreover, measured obtained isodose distributions of a radiosurgical procedure performed on the isocentric cobalt unit agreed with calculated distributions to within the +/-1 mm spatial and +/-5% numerical dose tolerances which are generally accepted in radiosurgery. The viability of isocentric cobalt units for radiosurgery would be of particular interest for centers in developing counties where cobalt units, because of their relatively low costs, provide the only megavoltage source of radiation for radiotherapy, and could easily and inexpensively be modified for radiosurgery.

It is known that slight variations in total dose delivered to the patient in external beam photon radiotherapy can significantly alter the probability of tumour control. For this reason, ICRU has recommended a goal of $ pm$5% precision in the dose delivery to the target volume. Several investigators have analyzed the degree of precision routinely achieved and have come to the conclusion that ICRU's goal can be attained, but in practice this is just barely so. / We have measured the degree of precision which exists in our institution by examining each step of the radiotherapy process on a cobalt unit and a 10 MV linear accelerator. Our study finds beam intensity uncertainties of $ pm$3.8% (one standard deviation) and beam positional uncertainties of $ pm$5.5 mm (one standard deviation). The effect of these uncertainties on the dose to the patient is illustrated for a typical case.

The utilization of ultrasound in diagnostic medicine has increased since the 1950's. Ultrasound is a non-invasive two dimensional (2D) imaging technique that provides useful information about underlying soft tissue anatomical structures. Developed recently, three dimensional (3D) reconstruction algorithms convert a series of sequential 2D ultrasound images into 3D data sets. 3D reconstruction is one phase in a pipeline for 3D ultrasound volume visualization that typically takes upwards of 2 minutes to complete. The objective of this research focuses on high speed 3D ultrasound reconstruction by comparing reconstruction speeds on parallel and sequential processors. To decrease reconstruction times, optimizations such as; conversion from floating point to fixed point, multithreading, in-line coding, and mathematical analysis were performed. Optimizations achieved a 15%--50% performance increase. Although parallel processors are not a requirement for 3D reconstruction, they will be necessary to achieve the ultimate goal of real-time 3D ultrasound volume visualization.

Most authors recommend drawing the mechanical axis on a three-foot (90 cm) full leg length x-ray for accurate assessment of knee alignment. Three foot x-rays are difficult to perform and reproduce and involve undue radiation to the gonads. The purpose of this project is to propose a new radiographic technique whereby the mechanical axis of the knee can be assessed on a short A/P x-ray of the entire tibia. / Methodology. 21 normal adults and 25 patients with malaligned knees were investigated in the following manner--the patient was x-rayed in standing position with the legs positioned exactly parallel to one another and vertical to the floor. Under these circumstances, the ankles were apart by a distance (distance F$ sb1$) equal to the distance between the femoral heads (distance F). The mechanical axes were hence parallel to one another and parallel to the long axis of the x-ray cassette and vertical to the floor. Two separate x-rays were taken, a three-foot (90cm) long x-ray and a short x- ray of the entire tibia. The mechanical axis was determined on the 90 cm, three-foot long x-ray. / A vertical line drawn on the short x-ray starting from the centre of the ankle and extended upwards and parallel to the long axis of the x-ray cassette could accurately identify the mechanical axis of the knee using either technique. (Fig. 1) / The technique has been called the "Parallel Mechanical Axes X-ray Technique". It has been validated and it will be demonstrated that such an x-ray technique: (1) Standardizes positioning of the lower extremities. (2) Is a precise, easily controllable method to assess knee alignment. (3) A short x-ray of the entire tibia is sufficient, thus reducing the cost of x-rays by 50%. (4) Obviates the need to visualize the pelvis thus minimizing net radiation exposure. (5) May be used in clinics and smaller hospitals, since it requires simple and inexpensive x-ray facilities.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3217. Advisers: Kyekyoon Kim; Phillip H. Geil. Includes bibliographical references (leaves 85-93) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3807. Adviser: John A. Katzenellenbogen. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6251. Adviser: Richard F. Nelson. Includes bibliographical references (leaves 81-82) Available on microfilm from Pro Quest Information and Learning.

The A2780s is a cisplatin and radiation-sensitive human ovarian carcinoma cell line from which the more resistant variant, A2780cp, was derived. In vitro experiments on the radiosensitivity of these cells with different treatments may be representative of the in vivo radiosensitivity, and maybe of use to patients receiving radiotherapy. Therefore, many studies have been directed at evaluation of the inhibition of DNA repair in order to improve radiotherapy. Previous studies showed that drugs and hyperthermia are repair inhibitors increasing the effectiveness of radiation. Cisplatin can also radiosensitize the A2780s and A2780cp and inhibit the sublethal damage repair (SLDR) (Raaphorst et al., 1995a). In this study we found no radiosensitization in the A2780s and A2780cp cells when cisplatin is added immediately before or after radiation. When cisplatin was added 24 hours prior to radiation, no increase in cellular resistance (adaptive response) to radiation treatment was observed. On the other hand cisplatin induced resistance when added during a pulse dose rate (PDR of 1 Gy/h) radiation treatment.

In closed angled Glaucoma, fluid pressure in the eye increases because of inadequate fluid flow between the iris and the cornea. One important technique to assess patients at risk of glaucoma is to analyze ultrasound images of the eye to detect abnormal structural changes. Currently, these images are analyzed manually. This thesis presents an algorithm to automatically identify and measure clinically important features in ultrasound images of the eye. The main challenge is stable detection of features in the presence of ultrasound speckle noise; an algorithm is developed to address this using multiscale analysis and template matching. Tests were performed by comparison of results with eighty images of glaucoma patients and normals against the feature locations identified by a trained technologist. In 5% of cases, the algorithm could not analyze the images; in the remaining cases, features were correctly identified (within 97.5 mum) in 97% of images. This work shows promise as a technique to improve the efficiency of clinical interpretation of ultrasound images of the eye.