Render Plan 3-D Conformal Therapy Dosimetry
Treatment Planning Computer

In the summer of 1995, the department acquired two separate Render Plan 3-D conformal therapy treatment planning stations. At the time of their acquisition, the Render Plan program was the only FDA approved treatment planning system for 3-D conformal therapy. The department was fortunate to acquire the equipment as part of an agreement for joint product development with Precision Therapy, the vendor of the software, and Elekta Corporation, the manufacturers for the Gamma Knife radiosurgery system. The treatment planning computer was purchased as part of an agreement that would eventually bring whole body stereotactic treatment capability to the department in exchange for product development in association with 3-D conformal therapy and whole body stereotactic radiosurgery.

Since its delivery, the Render Plan 3-D computer software and hardware have become the departmentıs primary treatment planning computer for both 3-D conformal plans and more standard two-dimensional plans. The 3-D treatment planning capabilities allow certain features of the linear accelerators to be exploited. Specifically, tumor targets are better localized, as are normal tissue-structures not at risk for infiltration by tumor. This better localization as well as the ability to bring beams in from a variety of directions allows for more precise dose localization within tumor regions and better exclusion of normal tissues. Such treatments may be better tolerated because of less normal tissue dose. In addition, with greater exclusion of normal tissue, treatment doses may be escalated, theoretically improving control rates.

A separate, but important, addition acquired along with the Render Plan computer program was the large milling machine in the block room area that, using information from the Render Plan, can be used to design custom tissue compensators. These compensators are milled from ingots of Cerrobend, which is a lead-like compound. These milled compensators can be placed in front of the beam to attenuate and avoid under dosing in thicker regions. This more homogeneous dose may be better-tolerated and better treat areas at risk. This custom milling machine was so large that it had to be divided into sections and reassembled in its current location. It takes approximately one hour for the milling bits to carve out these custom compensators, which are then attached to plates that fit on the treatment machines.

 

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