Biomedical Engineering Reference
In-Depth Information
the technologies can be extended to heavier ions in most cases at the expense of
higher cost and space requirements. We also briefly describe possible variations
to the accelerator scheme, including non scaling Fixed Field Alternating Gradient
(FFAG's) accelerators and various combinations of cyclotrons and synchrotrons
which may have important advantages over existing systems beyond just reduction
in size.
30.2.1
Single room options
Two suppliers of commercial proton therapy systems, IBA and Varian Medical
Systems, offer relatively small, single room proton therapy systems based upon
approved technology. Both systems use compact cyclotrons for acceleration of
protons to the 230 MeV energy required for 30 cm penetration depth into a human
target. The accelerators are adaptations of the standard systems offered by the two
companies, optimized for size and weight. Both systems follow the standard lay-out
of separating the accelerator and energy selection from the patient treatment room,
allowing full shielding of stray radiation produced in the process of beam delivery.
These are the smallest possible fully approved systems available today.
One step further away from the standard lay-out is the system offered by Still
River Systems. The essential philosophy behind this system is to integrate a compact
accelerator system and the energy selection process directly into the gantry rotating
around the patient. In the Monarch
250
the company advertises a small synchro-
cyclotron based on superconducting technology mounted on a rotatable arch, aiming
the beam at the patient from arbitrary directions. While at first this seems to be only
a small modification to standard systems, it actually represents a significant step
away from known centers. The massive shielding which is normally found between
the accelerator and the patient has been removed, the beam travels in a straight line
from the accelerator output to the patient. With passive energy selection, necessary
for cyclotrons, and beam shaping (it is not known to the authors if this shall be a
passive or active system) done this close to the patient position, shielding the patient
from out-of-field background radiation must be a major concern. No information is
available to the authors at the time of writing about shielding requirements and
potential radiation background, nor about beam monitoring and quality assurance
options foreseen for this short beam line.
The Monarch
250
is offered at a price of approximately 25 M$, which compared
to a typical price tag of 125 M$ price tag of a 4 room treatment installation does not
seem to offer a significant financial savings. But smaller size and overall cost of this
integrated system would make proton therapy available to smaller clinics or special-
ized private installations which may not have access to the patient base of 10 million
inhabitants in the geographic capture area necessary to justify a multi-room system.
To our knowledge the Monarch
250
has at the time of writing not yet received
final approval by the Food and Drug Administration, but the company expects this
approval to be forthcoming within this year. According to information in various
