International practice survey on the management of brain metastases: Third International Consensus Workshop on Palliative Radiotherapy and Symptom Control.

AIM: To evaluate international patterns of practice for the management of metastatic disease to the brain. MATERIALS AND METHODS: An online international practice survey was conducted from April to June 2010. Most of the survey questions were based on common management issues for which optimal management using level 1 evidence was lacking. The survey consisted of three sections: respondent demographics, 13 general questions regarding surgery, whole brain radiotherapy (WBRT) and radiosurgery and 13 questions related to specific scenarios. RESULTS: In total, 445 individuals responded to the survey over a 3 month period. Ninety per cent of respondents worked in a hospital-based setting. Ninety-three per cent of respondents were radiation oncologists. Thirty-seven per cent worked in an academic setting. Only three of 26 survey questions generated at least 70% agreement for a favoured response. Eighty-eight per cent of respondents chose comfort measures only for patients with multiple brain metastases who have been previously treated with WBRT and who now present 6 months later with two to four brain metastases (all less than 4 cm in size) with uncontrolled extracranial disease and bedridden state. Seventy-eight per cent of respondents would use WBRT alone for initial treatment in patients with two to four brain metastases (all less than 4 cm in size), with active, uncontrolled extracranial disease and a Karnofsky performance status of 70. Seventy-eight per cent of respondents chose surgical resection for an enlarging single brain metastasis that has been previously treated with radiosurgery. The enlarging single brain metastasis is in a surgically accessible site and is now symptomatic. The patient has controlled extracranial disease, good performance status and magnetic resonance spectroscopy was not diagnostic. CONCLUSIONS: There is a lack of uniform agreement for many common management issues (not well answered by level 1 evidence) in patients with metastatic disease to the brain.

Attitudes and beliefs concerning organ donation among Native Americans in the upper Midwest.

Because of increasing access to renal replacement therapy and the high incidence of renal disease among Native Americans largely due to type 2 diabetes mellitus, it is important to determine attitudes and beliefs in this population toward organ donation. In a study conducted on reservations in the upper Midwest during traditional powwows and health fairs, it was discovered that willingness to donate was more likely to occur if Native Americans were approached by a healthcare worker from their culture, if they had already signed a donor card, or if they knew someone with diabetes. Willingness to be a living donor (81%) was greater than willingness to donate after death (i.e., as a cadaveric donor) (54%). These findings indicate that cultural-specific information about organ failure rates and organ donation, when presented by knowledgeable individuals within the culture, could increase donation in the Native American population.

Absolute optical ranging using low coherence interferometry.

We describe a method for measuring submicrometer distances with an asymmetric fiber Michelson interferometer having an LED as a source of radiation. By measuring the phase slope of the Fourier components in the frequency domain, it is possible to locate the position of reflections with nanometer precision even in the presence of sample dispersion. The method is compatible with time domain sampling at the Nyquist rate which assures efficiency in data acquisition and processing.

Precise length measurements in multimode optical fibers.

Selective optical excitation permits both the group index and the group delay of on-axis modes of multimode fibers to be determined with high precision. The group index of several types of fiber was measured at 1310 nm in a fiber Michelson interferometer, and the values were tabulated. Group delays were obtained from the transit time of short-duration optical pulses. From these data the length of reference fibers approximately 2 km long was calculated. Length-measurement accuracy was limited by group-index uncertainties to approximately 0.04%. Also, a technique that uses these reference fibers to minimize uncertainties in distance measurements made with multimode optical-time-domain reflectometers is described.

Guided-wave reflectometry with micrometer resolution.

We describe a new type of optical reflectometry which is useful in testing single-mode lightguide systems. This technique uses a scanning Michelson interferometer in conjunction with a broadband illuminating source and cross-correlation detection. High resolution is achieved through the limited coherence of the backscattered radiation. With this approach it is possible to distinguish scattering centers separated by only a few micrometers. In some cases loss may be estimated for components in the transmission path of a test lightguide. The basic principles of this diagnostic technique, along with some performance characteristics, are illustrated for an all-fiber reflectometer. We also discuss several laboratory applications which serve to demonstrate the resolution capabilities of this measurement concept.

Optical time-domain reflectometer specifications and performance testing.

From a researcher's as well as a user's point of view, it is highly desirable to adopt a common basis for specifying optical time-domain reflectometer performance parameters. This paper proposes some procedures and test methods which permit these devices to be characterized in a consistent way. Passive test fixtures are also described which may facilitate measurements of dynamic range and other reflectometer properties.

Interlaboratory measurement comparison to determine the attenuation and bandwidth of graded-index optical fibers.

An interlaboratory measurement comparison was conducted by the National Bureau of Standards in cooperation with the Electronic Industries Association. Participants included NBS and nine optical fiber and cable manufacturers. Four graded-index fibers having lengths of 2, 2, 2, and 0.9 km were used. Measurements of attenuation at 850 nm, using both beam optics and mode filter approaches to achieve a restricted launch, gave one standard deviation spreads of 0.24, 0.12, 0.12, and 0.43 dB/km for an overall average of 0.23 dB/km. Best measurement agreement was obtained for a fiber having little differential mode attenuation. Measurements of -3-dB bandwidth from time domain acquired data at 90 nm gave an average one standard deviation spread of 12% with poorer agreement on the higher frequency portion of the frequency response.

Optical fiber phase discriminator.

Phase discriminators are devices widely used at rf and microwave frequencies to convert phase, or frequency, changes to amplitude changes. They find widespread use in generating audio feedback signals for frequency stabilization of oscillators and in angle demodulation applications. This paper demonstrates that similar devices, with similar functions, can be constructed in the visible region using optical fibers as delay-line elements. The operating principles of an optical-fiber delay-line phase discriminator are discussed. The sensitivity is shown to be proportional to the fiber propagation-delay time. A device working at 0.6328 microm is described and compared with predictions.