Imaging of Implants
Over 1,000,000 American women have had augmentation of the breasts with implants. Three basic types of implants have been used: silicone gel filled, saline filled and double lumen, where two chambers are present – one filled with silicone and the other with saline. Implants are placed for augmentation as well as for reconstruction in patients who undergo a mastectomy. Implants may be placed beneath in front of the pectoralis major muscle, the major chest muscle under the breast.
|Standard mammography views are taken first.
The breast and implant are compressed
with moderate force
|Image displacement mammography views (also called Eklund views) are performed with the implant pushed back against the chest wall. The compression paddle is applied to the breast tissue, which is pulled forward.|
Complications of implants may include: infection, encapsulation, calcification of the capsule, herniation or bulging, rupture. Imaging of the breast in patients with implants should include screening for breast cancer but also may include studies to assess for possible complications such as implant rupture.
When an implant is placed in the breast, the body typically forms a fibrous shell or capsule around the implant. This capsule may become thickened and hardened (encapsulation). The capsule surrounds the implant, so if the implant should rupture, the contents may be contained by the capsule (intracapsular rupture). If the contents extend through the capsule into the surrounding breast tissue, the rupture is extracapsular. An extracapsular ruptures allows for the spread of free silicone throughout the breast and into the soft tissues of the chest wall or axilla. Silicone may be transferred by lymphatic channels into the lymph nodes under the arm.
Screening mammography is necessary in all women over the age 40 and this recommendation includes women with implants. Standard views as well as additional views called “implant displacement” are performed to evaluate the breasts. For the implant displacement views, the technologist manually displaces the implant back and up as she applies the compression paddle to the anterior part of the breast. With this technique the breast tissue is much better evaluated and visualized. However, the tissue located deeper in the breast is usually not visible in entirety because of the overlying implant. If an implant is encapsulated, the implant displacement views are much more difficult to perform, and the visibility of the breast tissue is even more compromised.
If a saline implant ruptures, the saline leaks out and is absorbed in the body. The mammogram demonstrates that the implant is collapsed. If a silicone implant ruptures and is contained within the fibrous capsule, the rupture is not detected on mammography. Ultrasound is sometimes performed to evaluate the integrity of an implant. On ultrasound the intracapsular rupture may be detected. With breast MRI, the anatomy of the breast and the depiction of the implant are optimized. The pieces of the broken wall of the implant floating with the silicone contents within the fibrous shell are easily seen (the “linguine sign”).
In the case of an extracapsular rupture, the droplets of dense silicone outside the implant may be visible on mammography. On ultrasound this finding is confirmed as very dense echogenic droplets of free silicone in the breast tissue. On MRI the fibrous shell, the broken segments of silicone and the droplets of free silicone in the breast tissue are easily visualized. MRI is considered the most sensitive imaging test to assess for implant rupture.
Written By: Ellen Shaw de Paredes, MD, FACR