Practical applications of Beam's Eye View-based treatment planning to head and neck sites

Because of the complex anatomy of the structures involved by tumor as well as of the critical normal structures, treatment planning for advanced or spatially irregular cancers of head and neck sites is often extremely challenging. Computerized axial tomographic scanning is frequently invaluable in delineating tumor extension into areas inaccessible to physical examination. Our Beam's Eye View Planning (BEVP) capability allows us to incorporate this radiographic information accurately into actual plans used in the clinic. Over the past 2 1/2 years, we have applied this technique to 31 selected head and neck cancer patients at Michael Reese/University of Chicago Center for Radiation Therapy. Tumors were chosen on the basis of anatomical complexity: most involved multiple head and neck sites including orbit, skull base, paranasal sinuses and cavernous sinus. In all cases, radiation tolerance of critical normal structures including spinal cord, brain stem, optic chiasm, and eye had to be considered. With careful use of rigid immobilization devices and the outlining of several normal structures for purposes of alignment, we had no difficulty applying our BEVP technique to clinical simulations. Oblique field blocking was especially facilitated by BEVP. We found the BEVP technique very useful to assure that tumor coverage was adequate and tolerance of normal tissues not exceeded.