In May of 1999, the first Leksell Model C gamma knife was installed at the
Gamma Knife Zentrum in Krefeld, Germany. The authors recount their experien
ce with this latest technical gamma knife development.
Until the end of 1999, extensive physical and technical tests were performe
d and the system's hardware and software were continuously improved and ada
pted to the user's needs. By the end of 1999, 163 GKSs had been performed u
sing the new functionality of the Model C in manual or "trunnion" mode. The
trunnions, the two parts of the system that fix the patient headframe to t
he gamma knife when the isocenter positions, are checked manually.
During the same period the new automatic positioning system (APS) was exten
sively tested and refined so that the first APS treatment could be performe
d in January 2000. Fifty GKSs have been performed with the APS capability o
f the Model C. It was possible to use APS alone in 74% of surgeries whereas
in 14% someshots were given with APS and some with trunnions. In 12%, GKS
was scheduled and planned for APS, but due to unexpected technical (6%) or
mechanical (6%) reasons the treatment had to be performed manually.
At present there are some spatial restrictions with Model C in APS mode whe
n compared with the Model B. The most significant restriction is the narrow
space for the patient's shoulders, especially when deep-seated lesions are
treated. Through mechanical changes of the APS motor housing and some modi
fications of and to the motor driven couch adjustment, these limitations wi
ll be reduced in the future.
The APS treatment runs smoothly and fast. In no case did any relevant safet
y error occur during GKS. The more stringent mechanical limitations of the
APS compared with the Model B means that frame placement on the head is mor
e critical than before.