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Displacement Forces On MR Conditional Laryngoscopes

M Goette*, N Desai , Texas Children's Hospital, Houston, TX


(Monday, 7/30/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 8

Purpose: To evaluate the displacement forces on MR conditional laryngoscopes with and without batteries in a clinical setting, at a location chosen to simulate the worst case scenario of a pediatric laryngospasm event (i.e. near the region of highest spatial magnetic field gradient of a 3T magnet).

Methods: The ASTM International Designation: F2052 was followed to measure the magnetically induced displacement force on a combination of four MR conditional laryngoscope handles (Sharn Select, Heine (2), and Greenline) and blades of various sizes both with and without commercially-available batteries (i.e. not specifically MR conditional batteries). The testing rig, consisting of a protractor mounted on an acrylic structure, was placed at the end of the MR couch as shown in Figure 1, near the bore of a 3T Philips Achieva magnet being ramped down at end-of-life. Each device was suspended from the rig and the deflection angle was measured in 1° increments, with 45° denoting displacement forces approximately equal to the force of gravity (its weight).

Results: As seen in Table 1, all four MR conditional laryngoscope handles demonstrated deflection angles of less than 45° alone and with a variety of blades attached, denoting displacement forces less than the force due to gravity. When commercially-available ‘C’ or ‘AA’ batteries (depending on handle size) were added, all deflection angles were measured at or near 90°, denoting displacement forces much larger than the forces due to gravity.

Conclusion: This study demonstrated the significant displacement forces on MR conditional handles when used with commercially-available batteries. Although the measurement of deflection angles above 45° does not immediately deem a device unsafe, it is very apparent that they are indeed unsafe using these batteries in the MR environment when the forces are felt first-hand. Further investigation with MR conditional batteries is required.




IM- MRI : Risk evaluation & control

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