Integrals along lines passing through arrays of integer data are used in many applications. Existing algorithms employ parametric methods and floating point calculations to determine the data values that contribute to the line integrals, along with some form of interpolation to weight these data values. A new, nonparametric integer-arithmetic noninterpolating algorithm (NI0) and an extension using first-order interpolation (NI1) are presented here. These algorithms are compared for accuracy and speed with both Siddon’s [Med. Phys. 12, 252 (1985)] parametric floating point algorithm using no interpolation (PF0) and our extension using first-order interpolation (PF1). NI1 gives line integral values significantly closer to those of PF1 than does PF0 and runs nine times faster on a VAXstation 2000. NI0 gives less accurate line integral values than does PF0 but runs 19 times faster.
A system of computer programs has been created to allow the entry of radiotherapy treatment details as defined by the physician, the verification of the machine parameters at every treatment, and the recording of the entire course of treatment. Various utility programs are available to simplify the use and maintenance of the system. The majority of the code is written in FORTRAN-77, the remainder in MACRO-11. The system has been implemented on a PDP 11/60 minicomputer for use with a Mevatron linear accelerator, the implementation required minor hardware changes to the accelerator.
Quality assurance dosimetry often requires the comparison of measured doses with those calculated by a treatment‐planning system for phantoms of density other than 1.000 g/cm3. The presence of an artifact in the Pinnacle3 treatment‐planning system can lead to systematic errors in such cases.a These errors are also present, although reduced in magnitude, in heterogeneous media.PACS: 87.53.Bn, 87.53.Xd
The resolution of multileaf collimators (MLCs) is limited by their finite leaf width. A commercial package (HD‐270™) uses 3D couch translation and leaf adjustments to emulate smaller leaf widths. In this paper, we report on the commissioning of this feature using software testing, dial gauge measurements, and film dosimetry. We also identify a variety of limitations: software bugs and truncation artifacts, MLC leaf positioning uncertainties (random variations, systematic gantry dependence and backlash), and uncertainties in couch positioning. These reduce the capabilities of this implementation below that achievable theoretically.PACS numbers: 87.53.Kn, 87.53.Uv, 87.53.Xd
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