Development of a golden beam data set for the commissioning of a proton double-scattering system in a pencil-beam dose calculation algorithm.

PURPOSE: The purpose of this investigation is to determine if a single set of beam data, described by a minimal set of equations and fitting variables, can be used to commission different installations of a proton double-scattering system in a commercial pencil-beam dose calculation algorithm. METHODS: The beam model parameters required to commission the pencil-beam dose calculation algorithm (virtual and effective SAD, effective source size, and pristine-peak energy spread) are determined for a commercial double-scattering system. These parameters are measured in a first room and parameterized as function of proton energy and nozzle settings by fitting four analytical equations to the measured data. The combination of these equations and fitting values constitutes the golden beam data (GBD). To determine the variation in dose delivery between installations, the same dosimetric properties are measured in two additional rooms at the same facility, as well as in a single room at another facility. The difference between the room-specific measurements and the GBD is evaluated against tolerances that guarantee the 3D dose distribution in each of the rooms matches the GBD-based dose distribution within clinically reasonable limits. The pencil-beam treatment-planning algorithm is commissioned with the GBD. The three-dimensional dose distribution in water is evaluated in the four treatment rooms and compared to the treatment-planning calculated dose distribution. RESULTS: The virtual and effective SAD measurements fall between 226 and 257 cm. The effective source size varies between 2.4 and 6.2 cm for the large-field options, and 1.0 and 2.0 cm for the small-field options. The pristine-peak energy spread decreases from 1.05% at the lowest range to 0.6% at the highest. The virtual SAD as well as the effective source size can be accurately described by a linear relationship as function of the inverse of the residual energy. An additional linear correction term as function of RM-step thickness is required for accurate parameterization of the effective SAD. The GBD energy spread is given by a linear function of the exponential of the beam energy. Except for a few outliers, the measured parameters match the GBD within the specified tolerances in all of the four rooms investigated. For a SOBP field with a range of 15 g/cm2 and an air gap of 25 cm, the maximum difference in the 80%-20% lateral penumbra between the GBD-commissioned treatment-planning system and measurements in any of the four rooms is 0.5 mm. CONCLUSIONS: The beam model parameters of the double-scattering system can be parameterized with a limited set of equations and parameters. This GBD closely matches the measured dosimetric properties in four different rooms.

Tracking the demise of state hospital rate setting.

From its once preeminent position in state health policy, prospective hospital rate setting has declined in use from more than thirty states in 1980 to two today. This essay tracks the trend toward deregulation in various states--especially Massachusetts, New Jersey, and New York-- and examines the continuation of rate setting in Maryland. Principally, the decline reflects the development of managed care and capitation as alternative means to control health spending growth. This trend represents both an evolution in prospective payment methodology and a renewed preference for private over public-sector price controls.

Preceptors' perceptions of a baccalaureate preceptorial experience.

A preceptor's perception of a baccalaureate preceptorial experience has implications for faculty, nursing service administrators, and clinical agency personnel as they select nurses to serve as preceptors. This article describes a specific preceptorial experience and presents data collected from 137 preceptors who participated. Data include descriptive information about the preceptors and an analysis of their responses to six questions about the experience.

A rural nursing practicum: making it work.

Inciting the interest of baccalaureate students in the practice of nursing in a rural setting has been an ongoing challenge for many educators. The authors identify difficulties they encountered when attempting to involve students in a rural nursing practicum and delineate several strategies used to overcome these difficulties.

Mass retreat: the demise of Massachusetts hospital rate regulation.

Massachusetts recently deregulated its 16-year-old hospital rate regulation system, after earlier voting in favor of a delay of its "play-or-pay" universal health care mandate. This retreat holds important lessons for the rest of the nation. Specific flaws in the design of the system weakened regulation's effectiveness and undermined its political support. The failure to control costs led to the postponement of universal access. Massachusetts' experience illustrates that neither competition nor regulation--as currently practiced--are adequate to meet the access and cost control challenges facing the nation.

Nurse faculty practice: from theory to reality.

This article discusses the developmental stages involved in moving the concept of faculty practice from theory to reality. Bennis, Benne, and Chin's theories for planned change and Hage's theory for organizational change with a dominant coalition form the theoretical bases for this redical innovation. Smith's Time Line serves as the framework for tracing the development of the plan over its 6-year history. The political, logistic, and financial promoters and constraints at each stage of development are identified. Faculty reaction to the idea of faculty practice is presented, and the mechanisms used to bring about group consensus are described. The key elements for the successful transition of this plan are a small and resilient group of faculty planners and adaptation of existing organizational systems to accommodate nursing's interests. Finally, the practice plan is presented at its present stage of development with its future goals.