RADIATION FIELD MODELING AND COMPUTERIZED TREATMENT PLANNING

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"The vast improvements of the medical imaging and localization technology over recent years has brought a challenge to physics and computer technology to extend the capabilities of computerized treatment planning and optimization. A new photon beam model using a convolution kernel derived from experimental data has been derived and added as an alternative to the TPS for evaluation against the older NFD-based model. The number of integrated sectors in the electron beam model has been increased from 16 to 128, considerably improving the accuracy of irregular field dose distributions. The next clinical release of the treatment planning system has been delayed in order to incorporate further improvements. The three major changes are (1) the extension of the graphics drivers from 8 bit to 24 bit, so as to accommodate the full dynamic range of both CT, MR and Digital radiography, as well as to permit transparancy shading of organs, a feature which has just become available with the current PPC 604 generation processors; (2) recognition of user-supplied treatment machine data, rather than the hard coded data which currently applies to only one institution; and (3) expansion of the electron beam algorithm to three dimensions with homogeneity correction, rather than the 2-D, unit density model currently in use. This release is scheduled for late Spring 1998. The current research version already incorporates comparative treatment planning, with side-by-side displays of relative hot and cold regions, the display features a standard 512 x 512 main window, with smaller secondary windows. The main image can be panned and zoomed for acurate outlining of small structures. The ability to add additional ""drop-in"" beam datasets will also be added. Coordinated CT-MRI planning was also introduced using a set of tools to scale and register images and output the results in the standard TPS format. A separate program for brachytherapy which performs calculations using the AAPM TG-43 formalism. Modifications to the angular and radial dose functions have been made to permit treatment planning for intravascular brachytherapy. In FY 98, a commercial treatment planning system will be procured to alleviate the responsibilities of direct clinical support. Research will continue, with possible commercial co-sponsorship. The ability to move between multi-level images and dose distributions, as well as non-axial views (beams' eye, sagittal, coronal) using keyboard commands has greatly improved the clinical utility of the program."