Establishment of a Preliminary Screening Workflow for Environmental Electromagnetic Interference (EMI) In Digital Mammography
Abstract
Purpose
This study aims to establish a preliminary screening workflow to identify potential sources of environmental EMI prior to installation of mammography equipment utilizing newer generation Analogic detectors (LMAM2,LMAM3).
Methods
A TriField TF2 was used to acquire 3-axis AC magnetic field readings from 5 mammography rooms: one non-operational due to EMI-induced artifacts, and four in clinical use. Measurements were acquired in a grid at 1m increments and three elevation levels (floor, waist, eye-level), as well as at the position of the detector. Data was used to establish preliminary thresholds of concern that could be used to trigger engagement of the detector manufacturer for further investigation. This workflow was then used to screen proposed locations for the relocation of three mammography units.
Results
Measurements in room A1 with known EMI artifacts ranged from 0.3-1.4mG, with 0.9mGy measured at the plane of the image receptor, and points >1.0mG clustered along wall bordering an electrical closet. Preliminary thresholds of concern were established at 0.8-1.0mG (intermediate) and >1.0 mG (high). Several measurements acquired in 4 operational rooms exceeded those in A1, demonstrating that absolute magnitude of AC magnetic fields is not the only determinate of likelihood of EMI. Methodology successfully identified an electrical conduit running beneath the floor of two rooms slated for relocated units (>6.0mG at floor along path of conduit); readings periodically spiked in conjunction with elevator use resulting in AC magnetic fields >1mG throughout the room at waist-level. Vendor and detector manufacturer were engaged for further evaluation.
Conclusion
The proposed workflow was successfully used to screen three mammography rooms prior to equipment relocation and ultimately resulted in changes to installation locations for two out of the three. Findings support the need for vendor EMI screening guidance to prevent costly installation delays and image quality issues.