Both of these devices can be placed in advance of surgery, the exact duration is variable and is best clarified by the company as it has changed over time. Also weather it can be placed into a node may be updated.
The Savi scout uses radar technology and works well, but has been reported to have possible interference from OR some types of lights. It has a smaller “bloom” on MRI. It is the largest of the localizers, and has been reported as cumbersome to place. Cautery can destroy the device if the bovie tip hits the device.
Mageed uses magnetic energy technology and also works well. It requires plastic or titanium instruments, and there is a reset that needs to be performed with each scan. It’s bloom on MRI is larger. It is easily placed by radiology
There also is the Localizer which uses RFID technology and has an intermediate bloom, no bovie issues, special equipment or light issues. It is reasonably easy for radiology to place, but it can dislodge during dissection.