Purpose: To determine the extent of microwave ablation equipment interference with wireless patient monitoring in neighboring clinical spaces and estimate a shielding goal to allow simultaneous operation.
Methods: Two Covidien Emprint microwave ablation units were clinically oriented in a space for a future procedure room, adjacent to an anesthesia induction bay where anesthetized patient vitals are wirelessly monitored with a Philips Expression MR400. One antenna per generator was inserted into an anthropomorphic water tank phantom at locations that represented worst-case clinical scenario for leakage microwave energy. Patient wireless monitoring devices were operated in the induction bay and interference was assessed with microwave generators set to different power levels. Ambient RF power (2.4—2.5 GHz range) was measured in the induction bay using a Tektronix RSA306B USB Spectrum Analyzer. The following measurements were performed 10 times over a 3-week span: (1)background, (2)MR400 communication, (3)full microwave antenna power (I(max)), (4)microwave antenna power level that preceded loss of vital trace (I(Edge)), and (5)power level that did not cause significant interference (I₀) with MR400. To assess the effect of room shielding, microwave units were operated inside an MRI scan room while wireless patient monitoring devices were operated in the adjacent induction bay.
Results: Experiments demonstrated that microwave interference could result in complete loss of patient vitals data. Repeated RF power measurements showed: (1) significant overlap between MR400 communication and leakage microwave at I(max), (2) partial overlap at I(Edge) (3) and negligible overlap at I₀0. From these results, a shielding design goal of 16dB was calculated. Lastly, MRI scan room shielding attenuated leakage microwave to power levels at or below background and prevented interference with MR400 in the adjacent room.
Conclusion: Leakage radiation from microwave ablation devices can catastrophically interfere with wireless patient monitoring in nearby rooms. Proper room shielding can prevent such interference.
Microwaves, Image-guided Therapy
Not Applicable / None Entered.