Applying graphics processor units to Monte Carlo dose calculation in radiation therapy.

We investigate the potential in using of using a graphics processor unit (GPU) for Monte-Carlo (MC)-based radiation dose calculations. The percent depth dose (PDD) of photons in a medium with known absorption and scattering coefficients is computed using a MC simulation running on both a standard CPU and a GPU. We demonstrate that the GPU's capability for massive parallel processing provides a significant acceleration in the MC calculation, and offers a significant advantage for distributed stochastic simulations on a single computer. Harnessing this potential of GPUs will help in the early adoption of MC for routine planning in a clinical environment.

Outcome of stage I carcinoma of the breast at the University Hospital of the West Indies (1982-1988).

The 5-year survival data for 62 patients with Stage I breast cancer treated at the University Hospital of the West Indies (UHWI) between 1982 and 1988 were evaluated to determine which factors were affecting outcome. The overall survival rates (66.7%) were below those quoted from large multicentre studies from North America, Western Europe and Australasia. The most significant survival differences emerged in the subset of postmenopausal patients with clinically staged disease who fared worse than those with pathologically staged disease. These data suggest that clinical staging is inadequate for the management of Stage I breast cancer. Consistent pathological staging, utilization of other prognostic predictors, and systemic therapy on a more widespread scale may help to improve the clinical outcome.

Wiskott-Aldrich syndrome in a Jamaican.

A 3-week-old boy presented with severe thrombocytopenia and recurrent infections. He was subsequently found to have Wiskott-Aldrich Syndrome, a rare X-linked disorder. Splenectomy was performed and he died of post-splenectomy sepsis despite prophylactic antibiotic therapy. This is the first recorded case in the English-speaking Caribbean.

The POEMS syndrome.

The POEMS syndrome is an unusual disorder manifesting primarily as a peripheral sensorimotor neuropathy in association with a monoclonal gammopathy. The importance of its recognition is that significant clinical improvement may result from localization and treatment of the underlying plasma cell tumour.

The POEMS syndrome

The POEMS syndrome is an unusual disorder manifesting primary as peripheral sensorimotor neuropathy in association with a monoclonal gammopathy. The importance of its recognition is that significant clinical improvement may result from localization and treatment of the underlying plasma cell tumour.

Glanzmann's thrombasthenia and pregnancy.

Glanzmann's thrombasthenia is a rare congenital disorder of platelet function manifesting as defective primary haemostasis. Bleeding episodes often require platelet transfusions, and allo-immunization to donor platelets may occur. The problems of ensuring adequate haemostatic potential for delivery of an allo-immunized pregnant female with Glanzmann's thrombasthenia are presented.

Glanzmann's thrombasthenia and pregnancy

Glanzmann's thrombasthenia is a rare congenital disorder of platelet function manifesting as defective primary haemostasis. Bleeding episodes often require platelet transfusions, and allo-immunization to donor platelets may occur. The problems of ensuring adequate haemostatic potential for delivery of an allo-immunized pregnant female with Glanzmann's thrombasthenia are presented

Spark discharge: application multielement spectrochemical analysis.

Spark discharge is shown to be a cyclic process of energy dissipation, with one spark in a time-connected train influenced by its relation to predecessor sparks. Spectroscopic instruments having temporal, spatial, and spectral resolution indicate that the light emission is highly ordered with cylindrical symmetry about the current-conducting spark channel. The favored spatial coincidence is between the channel and the most highly ionized and most excited species sampled from the cathode, with less ionized and less excited species emitting farther outward. Light absorption occurs to such an extent that there are full line reversals in excited states of magnesium ions, distant from the channel. Schlieren data indicate a toroidal structure in the postdischarge environment. Charge transfer, Penning ionization, and sensitized fluorescence are thought to be the chemical mechanisms responsible for the spectroscopic topography. Experiments in spectrochemical analysis based on the topography and designed for increased sensitivity, reduced matrix effects, and simpler spectra are discussed.

High spatial resolution schlieren photography.

Some geometrical optical considerations for attaining spatial resolution of about 100 microM in a photographic schlieren experiment are presented. The topics of astigmatism, coma, and spherical aberration are considered briefly. Special emphasis is directed to diffraction effects in a single-mirror schlieren instrument. A method for estimating the size of limiting apertures in the knife-edge plane to allow a particular spatial resolution, compromised vs photographic sensitivity, is reported. A sample application for photographing the schlieren effects in a small spark discharge is included.