The Palatal System Implant Assembly (Pavad Medical, Inc., Fremont, CA) is designed to treat sleep disordered breathing.
The Palatal System Implant Assembly was determined to be MR-conditional according to the terminology specified in the ASTM International, Designation: F2503. Standard Practice for Marking Medical Devices and Other Items for Safety in the Magnetic Resonance Environment.
Non-clinical testing demonstrated that the Palatal System Implant Assembly is MR Conditional. A patient with this implant can be scanned safely immediately after placement under the following conditions:
-Static magnetic field of 1.5-Tesla
-Maximum spatial gradient magnetic field of 250-Gauss/cm
-Maximum MR system reported whole-body-averaged specific absorption rate (SAR) of 3.5-W/kg for 15 minutes of scanning (per pulse sequence)
In non-clinical testing, the Palatal System Implant Assembly produced a temperature rise of 0.8 °C at a maximum MR system-reported whole body averaged specific absorption rate (SAR) of 3.5-W/kg for 15-minutes of MR scanning (per pulse sequence) in a 1.5-Tesla MR system using a transmit/receive body coil (1.5-Tesla, Magnetom, Software Numaris/4, Version Syngo MR 2002B DHHS, Siemens Medical Solutions, Malvern, PA).
MR image quality may be compromised if the area of interest is in the exact same area or relatively close to the position of the Palatal System Implant Assembly. Therefore, optimization of MR imaging parameters to compensate for the presence of this implant may be necessary. The following chart provides artifact information for the Palatal System Implant Assembly in relation to different pulse sequences at 1.5-Tesla:
Pulse sequence and Signal Void
T1-weighted spin echo, long axis orientation 2.7-cm2
T1-weighted spin echo, short axis orientation 2.7-cm2
Gradient echo, long axis orientation 8.8-cm2
Gradient echo, short axis orientation 9.6-cm2
MRI Procedures and Function of the Palatal System Implant Assembly
The effects of MRI procedures on the functional aspects of Palatal System Implant Assembly devices were assessed. In-vitro testing was performed on a phantom with six Palatal System Implant Assembly devices placed in various orientations relative to the MR system. MRI was conducted using 1.5-Tesla/64 MHz MR system (transmit/receive RF body coil) to perform 8 different MR imaging pulse sequences, as follows: T1-weighted spin echo, T1-weighted fast spin echo, T2-weighted spin echo, T2- weighted fast spin echo, three dimensional fast gradient echo, turbo/fast gradient echo, turbo/fast spoiled gradient echo, echo planar imaging.
The findings indicated that there was no apparent damage or alteration in the function of the Palatal System Implant Assembly. Thus, the Palatal System Implant Assembly was demonstrated to maintain full functionality after exposure to the MRI conditions indicated above.
Additional guidelines for the Palatal System Implant Assembly include:
-Do not use MR systems other than 1.5 Tesla MR systems.
-Continuously monitor the patients using visual and audio means (i.e., intercom system) throughout the MR procedure
-Instruct the patient to alert the MR system operator of any unusual sensations or problems so the MR system operator can terminate the MRI procedure, if needed.
-Provide the patient with a means to alert the MR system operator of any unusual sensations or problems that may be experienced during the MRI procedure.