Abstract
Background Gamma Knife targeting is geometrically limited by the physical dimensions of the
head, helmet, headframe, and the radiation target position. All four aspects need
to be considered for accurate treatment planning. Within the available space, delivery
of the treatment isodose is based on the target position, which must be brought into
the center of the collimator. In cases of anatomically challenging target positions
in far eccentric locations of the head, careful treatment planning needs to be performed
that does not exceed the limits of the system.
Clinical Presentation We describe a case of a challenging far anterior ethmoid sinus hemangiopericytoma
in an 80-year-old woman.
Technique The tumor was treated successfully by positioning the patient prone on a Model C
Gamma unit. The physical restrictions of the Gamma Knife surgical system and the rationale
for improved anterior targeting using the prone position are discussed.
Conclusion A thoughtful approach to positioning in challenging anterior lesions extends the
targeting capabilities of certain Gamma units.
Keywords
radiosurgery - gamma knife - hemangiopericytoma - prone position
