ViewRay Inc. MRIdian® system L-0009 Release 4.5 47
Chapter 2: Safety Information and
SAR: The MRIdian MRIS operates in the Normal Operating Mode for SAR at all times.
According to IEC 60601-2-33 (3rd Edition), a SAR of less than 2 W/kG in the whole body is in
the Normal Operating Mode. Because of the 0.35T field strength, the MRIS does not exceed
1.2 W/kG, and is therefore always in the Normal Operating Mode.
dB/dt: Th
e MRIdian 0.35T magnet is capable of operating in the First Level Controlled Mode
for dB/dt. Patients may experience peripheral nerve stimulation, or a twitching sensation,
during scans. In situations where the system enters the First Level Controlled Mode for dB/dt,
the operator will receive a dialog box warning indicating that the particular sequence is in the
First Controlled Mode for dB/dt. The operator is required to acknowledge this warning before
continuing the scan. Operation of the system in the Second Controlled Mode for dB/dt is
prevented by software controls.
2.11.2 First Level Controlled Operating Mode
All treatment cinés are in the First Level Controlled Operating Mode for dB/dt. See
"Peripheral Nerve Stimulation (dB/dt)” on page 46
The system alerts the operator when a scan will enter the First Level Controlled Operating
Mode
by displaying the following warning:
You must OK the First Level Controlled Operating Mode by taking the deliberate action of
Clicking > OK.
You must inform your patient of the possibility of peripheral nerve stimulation and remain in
c
onstant audio and visual contact with the patient.
Operators must receive training in methods to minimize adverse health effects of high
gr
adient magnetic fields.
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