Polymer gel measurement of dose homogeneity in the breast: comparing MLC intensity modulation with standard wedged delivery.

Polymer gel dosimetry has been used to measure the radiotherapy dose homogeneity in a breast phantom for two different treatment methods. The first 'standard' method uses two tangential wedged fields while the second method has three static fields shaped by multileaf collimators (MLCs) in addition to the standard wedged fields to create intensity modulated fields. Gel dose distributions from the multileaf modulation treatment show an improved dose uniformity in comparison to the standard treatment with a decreased volume receiving doses over 105%.

The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement.

In this study, the dose distribution delivered by low dose rate Cs-137 brachytherapy sources was investigated using Monte Carlo (MC) techniques and polymer gel dosimetry. The results obtained were compared with a commercial treatment planning system (TPS). The 20 mm and the 30 mm diameter Selectron vaginal applicator set (Nucletron) were used for this study. A homogeneous and a heterogeneous-with an air cavity-polymer gel phantom was used to measure the dose distribution from these sources. The same geometrical set-up was used for the MC calculations. Beyond the applicator tip, differences in dose as large as 20% were found between the MC and TPS. This is attributed to the presence of stainless steel in the applicator and source set, which are not considered by the TPS calculations. Beyond the air cavity, differences in dose of around 5% were noted, due to the TPS assuming a homogeneous water medium. The polymer gel results were in good agreement with the MC calculations for all the cases investigated.

Comparison of EGS4 and MCNP Monte Carlo codes when calculating radiotherapy depth doses.

The Monte Carlo codes EGS4 and MCNP have been compared when calculating radiotherapy depth doses in water. The aims of the work were to study (i) the differences between calculated depth doses in water for a range of monoenergetic photon energies and (ii) the relative efficiency of the two codes for different electron transport energy cut-offs. The depth doses from the two codes agree with each other within the statistical uncertainties of the calculations (1-2%). The relative depth doses also agree with data tabulated in the British Journal of Radiology Supplement 25. A discrepancy in the dose build-up region may by attributed to the different electron transport algorithims used by EGS4 and MCNP. This discrepancy is considerably reduced when the improved electron transport routines are used in the latest (4B) version of MCNP. Timing calculations show that EGS4 is at least 50% faster than MCNP for the geometries used in the simulations.

Timing of coincidence anticipation by NCAA division I softball athletes.

After visual screening, 44 NCAA Division I softball athletes qualified to participate in this study conducted at the 1993 National Invitational Championship Tournament to assess anticipation of coincidence of these athletes. A full-swing batting motion was used to intercept a stimulus apparently moving at 45 or 70 mph, using the Bassin Anticipation Timer. Scores were recorded as early or late after each subject swung a standardized bat which interrupted a photoelectric beam when each of 20 randomly administered slow or fast simulated pitches was presented. Analyses of variance of AE, CE, and VE showed athletes swung significantly early on the 45-mph and late on the 70-mph simulated pitch speed. More specifically, less AE and CE error was recorded at the slow speed; athletes were more consistent (VE) in response to the fast speed. Results supported prior findings in which simulated-pitch speeds were similar to the present ones. Runway length, simulated-pitch speed, and the degree of swing simulation were suggested as variables to consider in similar investigations.

The effects of daily-wear contact lenses on contrast sensitivity in selected professional and collegiate female tennis players.

Contrast sensitivity (CS) has recently emerged as an important predictor of visual performance. Few studies, however, have been published involving CS and its role in vision for sport. The purpose of this investigation was to determine if significant differences occurred in CS between female professional and collegiate tennis players who wore daily-wear soft contact lenses (N = 10) and those players who wore no corrective lenses (N = 10) in competition as measured by the Stereo Optical Optec 2000 Vision Tester. Subjects were between the ages of 18 and 37 years. Mean ages were 21.76 (+/- 4.018) and 25.40 (+/- 5.379) years for those wearing lenses and those not, respectively. Each subject was preliminarily screened for SVA-distance, lateral/vertical phorias, stereopsis, and color perception. All subjects were within accepted limits. CS was assessed at 1.5, 3, 6, 12, and 18 cycles per degree (cpd). Each subject was assessed monocularly; eye initially assessed was determined randomly. A 2 x 2 factorial analysis of variance (alpha = .05) was used to analyze data. No significant differences were found between eyes. Significant differences were found at 3, 6, 12, and 18 cpd. It may be concluded that those female professional and collegiate tennis players wearing no corrective lenses were significantly higher in CS at intermittent and high spatial frequencies than those who wore daily-wear soft contact lenses in competition.