BAS Switch Fits the Needs of Medical Imaging System
Ethernet is receiving much attention as a communication interface
in embedded systems used in the field of medical imaging. Medical manufacturers
claim the design of imaging systems employ Ethernet to extract the most
benefits from the infrastructure, while allowing physicians to effectively
care for their patients.
Today, physicians in many hospitals and cancer treatment centers, use
such a system called the TomoTherapy Hi-Art System®. The architecture
for this system, designed and manufactured by TomoTherapy Inc. in Madison,
Wisconsin, fuses a three-step process: treatment planning, patient positioning
and treatment delivery. The result is the ability for physicians to
deliver sufficient radiation to destroy a tumor without impairing an
individual's physical well-being or damaging any healthy cells beyond
repair.
To optimize the system's investment, engineers at TomoTherapy chose
Ethernet as the control and communications network. With Ethernet installations
previously in place at the company, TomoTherapy engineers already possessed
a good understanding of the technology.
In this application, the Ethernet switch was important
to the network's infrastructure. It translated to quicker throughput,
enhanced reliability, the meeting of space requirements and the
easy integration of different computers. Once the main concerns
were defined, then engineers searched for a supplier of industrial
Ethernet switches to provide reliable communications between the
main components. They selected Contemporary Controls. This company,
located in Downers Grove, Illinois, is a manufacturer of components
meeting all automation needs.
TomoTherapy opted for the company's BAS switch, offering the newest
in communication technology. The BAS switch (EIBA5-100T) is designed
with a minimum number of components, packing more functionality
and ease of installation into this compact device. |
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The System
To employ the proper amount of control for the TomoTherapy system,
it was only necessary for the subsystems to provide real-time performance,
not the Ethernet communications, to precisely track the position of
the radiation beam.
Tim Holzmann, Lead Design Engineer for TomoTherapy, says the BAS switch
is only accessible to service personnel. It's under the fiberglass covers
of the machine, mounted on the rotating gantry. The equipment resembles
a CT machine, approximately 12" x 12" x 8" with a steel
frame underneath. The two embedded computers on the machine's rotating
side are connected to the stationary computers using the BAS switch.
The selection of the BAS switch was necessary for this robust type of
environments, specifically its EMI protection. Holzmann and other engineers
at TomoTherapy recognized the key benefit of this device. "We were
concerned about the small panel area (10 x 6) for mounting," explains
Holzmann. "But the BAS switch allowed us to provide secure mounting
on the rotating ganty with screw terminal positive locking power connectors.
Good mounting holes. No need for receptacles or extension cords or duct
tape. We had available low-voltage DC power for easy connection to the
switch., saved on extra wiring expense."
"What's even more unique to us," adds Holzmann, "is the
label on this switch. The label on the unit can be written upon so that
port connections can be documented as to the location of our other connected
equipment."
The BAS switch truly embraces the concept of Plug and Play (PnP) because
no operator intervention is required. In case the power must be removed
and reapplied, the unit is able to return to operation.
As for regulatory standards, the BAS switch is UL 508 Listed, C-UL Listed,
CSA No. 22.2 14-M91,
Industrial Control Equipment and carries the CE Mark to be sold in the
European Union.
The infrastructure is not complicated. Holzmann says the two embedded
computers and one RS-485 to Ethernet converter connect to the BAS switch.
The computers use either 10 or 100 base communications with the switch.
The switch connects to a media converter (CAT 5 to coaxial), across
the slip ring, to another media converter, to the stationary machine
network. Cable lengths are short, either 2 to 3 feet.
There was no need for additional wiring.
How the System Works
The patient is positioned lying down on a bench that passes continuously
through the bore of the rotating ring gantry. The gantry shelters a
device known as the linear accelerator. The linear accelerator delivers
radiation in a helical pattern around the patient as the bench moves
simultaneously with the turning gantry.
The system delivers IMRT using a device called a multileaf collimator,
or MLC. The MLC is comprised of a series of leaves. Each leaf opens
or closes to emit or stop radiation. Prior to treatment, physicians
calculate the radiation's required pattern of delivery. This is important
to modulate the radiation's strength so it conforms to the shape and
the location of the tumor.
Other elements of the system allow clinicians to take a CT scan of the
patient's tumor prior to te procedure in order to properly position
the patient.
There's even a reduction in the number of devices in the system's chain
as compared to a radiotherapy department's workflow. "This is an
innovation that's inevitable," says Holzmann. " It's a fact
that systems, such as ours, have advanced to fewer components, especially
in the medical field, but these systems are providing more advanced
functionality. And the BAS switch only adds to the right balance of
effectiveness. The switch is operating great. We have experienced no
failures."
