Compound versus fundamental imaging in the detection of subdermal contraceptive implants

The purpose of this study was to compare the use of fundamental versus compound sonographic imaging in the localization of nonpalpable subdermal contraceptive implants.

We describe 3 cases of subdermal implants for which detection was requested via sonography. The implants were evaluated with both fundamental and compound imaging with various transducers ranging from 5-2 to 15-7 MHz. The fundamental and compound images were compared with respect to echogenicity and, therefore, visibility, of the contraceptive implant and the appearance of posterior acoustic features.

Both fundamental and compound imaging visualized the focus representing the implant equally well. However, fundamental imaging proved superior to compound imaging for visualizing the posterior acoustic shadowing created by the implant. The posterior acoustic shadowing was the most helpful feature in the identification of these implant rods.

When attempting to image a subdermal contraceptive implant with sonography, fundamental imaging should be used. Compound imaging may mask the posterior acoustic features that can aid in implant identification.