Microscintigraphy with high resolution collimators and radiographic detectors.

The potential use of high resolution collimators with standard radiographic detectors in place of conventional gamma cameras for high resolution microscintigraphy is presented. Polycapillary multiple hole collimators are shown to provide 10-100 micron scale spatial resolution. A series of images from arrays of 125I brachytherapy seeds in Lucite phantoms display resolution better than 0.1 mm with good sensitivity and a 30 mm field of view. In addition to application to brachytherapy seed localization, such "cellular" level resolution is necessary for high-resolution in vivo imaging in mouse models. The system could also enable the use of a wider variety of isotopes, including much lower photon energy isotopes in nuclear medicine, as the high resolution collimator allows more flexibility in detector constraints.

X-ray optics for better diagnostic imaging.

Polycapillary x-ray optics provide an innovative new way to control x-ray beams. Placing these optics after the object to be imaged provides very efficient rejection of Compton scatter, while allowing image magnification without loss of resolution, image demagnification, or image shaping to match with digital detectors. Measured scatter rejection optics had primary transmissions greater than 50% and scatter transmission of less than 1%. For a 5-cm thick Lucite phantom, this resulted in a contrast enhancement of nearly a factor of two at 20 keV and three at 40 keV. The magnification from the tapered capillary optics improved the MTF at all frequencies out to 1.8 times the original system resolution. Increases below the system resolution are most important because clinically relevant structures generally occupy lower spatial frequencies. Alternatively, placing a collimating optic and diffracting crystal before the patient provides sufficient monochromatic beam intensity for medical imaging. Contrast, resolution, and intensity measurements were performed with both high and low angular acceptance crystals. At 8 keV, contrast enhancement was a factor of 5 relative to the polychromatic case, in good agreement with theoretical values. At 17.5 keV, monochromatic subject contrast was more than a factor of 2 times greater than the conventional polychromatic contrast. An additional factor of two increase in contrast, for a total factor of four, is expected from the removal of scatter in a large beam clinical system. The measured angular resolution after the crystal was 0.4 mrad for a silicon crystal.

Stationary crystal diffraction with a monochromatic convergent X-ray source and application for macromolecular crystal data collection.

A diffraction geometry utilizing convergent X-rays from a polycapillary optic incident on a stationary crystal is described. A mathematical simulation of the resulting diffraction pattern (in terms of spot shape, position and intensity) is presented along with preliminary experimental results recorded from a lysozyme crystal. The effective source coverage factor is introduced to bring the reflection intensities onto the same scale. The feasibility of its application to macromolecular crystal data collection is discussed.

Non-specific urethritis as an office problem.

This article is prompted by experiences gained as a part-time physician, Students' Health Service, The University of Calgary. The steady increase in incidence of non-specific urethritis in young people, and the clinical problems of diagnosis and treatment are discussed. Attention is directed to its still largely unknown causation and there is some discussion of prevention.

A rich experience: clinical clerkship in family practice.

This article demonstrates a year's experience in which the clinical clerkship in family practice is integrated within the curriculum of the University of Calgary Medical School.

Properties of ion-bombarded fused quartz for integrated optics.

Development of techniques for production of carefully controlled, low-loss optical waveguides in solid dielectric materials is essential to development of integrated optical circuits for signal processing in future optical communications systems. Ion implantation offers an attractive possibility because of the refractive index and film thickness control possible by this technique. To evaluate this possibility we have investigated some of the optical properties of ion-bombarded fused quartz. A variety of ions ranging from helium ions to bismuth ions has been used. We have concentrated on refractive index and optical loss variations (on those implants into which a beam could be launched) as effected by (1) ion species and dose, (2) surface preparation, (3) surface temperature during bombardment, and (4) postbombardment annealing. This paper does not attempt to give an inclusive account of all the results obtained but principally discusses the best results so far, which are those using lithium ions. For lithium ion bombardment we have observed approximately linear variation of refractive index at 6328 A with dose n = n(0) + 2.1 x 10(-21)C, where n(0) is the prebombardment value (= 1.458 for fused quartz), and C is the ion concentration in ions/cm(3) (C < 2.2 x 10(19)). The optical absorption decreases significantly with increase in substrate temperature during implantation, and losses less than 0.2 dB/cm have been achieved. The refractive index change appears to be primarily due to disorder produced by the incident particles rather than a chemical doping effect as evidenced by postbombardment annealing studies.