Augmentation mammoplasty for cosmesis has been performed on greater than 2 million American women. The authors review different types of breast enhancement and the special considerations in their imaging.
Dr. Shaw deParedes is Professor of Radiology and Director of
Breast Imaging at the Medical College of Virginia, in Richmond; she
is also on the editorial board of this journal. Dr. Dunn is an
Assistant Professor of Radiology and Ms. Cousins is a mammographer,
both at MCV.
Augmentation mammoplasty for cosmesis has been performed on
greater than 2 million American women. The procedures have included
augmentation by direct injection of various substances and
augmentation by placement of a prosthesis or implant.
Reconstruction of the breast after mastectomy is performed by
creation of a breast mound with a myocutaneous flap, or by
insertion of an implant.
Early procedures for augmentation included the direct injection
of various substances, including talc, paraffin and silicone. This
method is no longer performed in the United States, but is
occasionally still used in Asia. The first silicone gel implant was
placed in 1962.1 In 1992, the FDA placed a moratorium on silicone
breast implants after the question of a possible association with
connective tissue disease was raised. Currently in the United
States, only saline implants are permitted for augmentation
Direct injection for augmentation
In the early 1900s, liquid paraffin was used commonly for
augmentation mammoplasty by direct injection into the breast. Other
substances utilized for injection-type breast augmentation have
included wax, oils, fat, and talc. These injections often caused
hard masses with tissue necrosis. In Japan in the 1950s,
augmentation was performed by direct injection of silicone into the
breast; this practice was subsequently adopted in the United
States. Problems similar to those encountered with paraffin
injection occurred with silicone, including the formation of dense,
hard, tender breast masses caused by the response of the tissue to
the foreign material. Silicone injections were banned in the United
States in 1965; however, some women continued to have the procedure
Mammography in the patient who has undergone augmentation bv
direct injection is challenged by the extreme density of the
tissue, the hardness and retraction of tissue, which compromise
positioning, and the extensive masses and calcifications that
develop, limiting accurate diagnosis. The use of higher kVp ranges
(30 to 32) and alternate target/filter combinations (MO/Rh or W/Rh)
to shorten the exposures and better penetrate the tissue are often
of some aid in optimizing the image quality. Hyperdense parenchyma
associated with diffuse spherical or eggshell calcifications of the
fat necrosis type are typical mammographic findings (figure 1).3
Sonography is of limited value, often showing diffuse shadowing
from the fibrotic reaction.
Though only saline implants are currently permitted for
augmentation, three basic types of implants may be seen on
mammography: saline, silicone gel, and double lumen, which contains
silicone in one chamber and saline in the other. The envelopes of
the implants are made of either a smooth silicone elastomer, which
appears on mammography with very well-defined margins, or a
textured elastomer, which, on imaging, has fuzzy, irregular
margins. Some types of saline implants, particularly those used as
tissue expanders for breast reconstruction, are equipped with a
port, through which saline is injected for gradual filling.
Silicone implants are much more dense on mammography than are
saline prostheses. Silicone implants may be associated with gel
bleed4 (migration of silicone through the implant envelope) or
rupture with extravasation of silicone into the tissues. Saline
implants have a greater tendency to deflate if ruptured (figure 2),
but are not associated with the tissue reaction that occurs with
Implants are placed in either a retroglandular (prepectoral)
location or in the subpectoral space. After insertion, the normal
implant incites a fibroblastic response of the contiguous tissue;
this will ultimately develop into a thin capsule which encloses the
implant. One of the complications associated with implants,
particularly those in a retroglandular location, is capsular
thickening and contraction. It is believed that periprosthetic
infection is associated with capsular contraction.5 Implantation in
a retropectoral or submuscular location and the use of textured
implants are both thought to be associated with fewer cases of
Mammographic imaging of the augmented breast
The presence of implants makes imaging the breasts more
challenging and, therefore, correctly positioning the breast for
mammography is vital. The degree to which implants do obscure
breast tissue depends on their position, density, and level of
encapsulation. Silverstein et al7 found a 49% decrease in
measurable breast tissue on mammography after augmentation
mammoplasty; Guenther et al8 report that only 7 of 20 cancers in
women with implants were detected on mammography.
Standard mammographic imaging of the patient with implants
the following: standard mediolateral, oblique, and craniocaudal
views, and a modified positioning, described by Eklund et al,9
known as the implant displacement (ID) views. Standard views are
utilized to visualize the posterior tissues and low axillary region
of the implant, whereas implant displacement views allow for better
compression and visualization of the anterior parenchyma.
To position the patient for the ID views, the technologist must
palpate the anterior edge of the implant, pulling the tissue that
is anterior to it forward as the compression device is brought
down. As compression is applied, the implant should be displaced
posterosuperiorly (figure 3). These implant displacement views may
not be satisfactory, however, for patients with encapsulated
implants: In this situation, a standard ML or 90° lateral view may
be helpful to visualize more of the tissue obscured by the
Complications of implantation
In addition to the complications already mentioned (gel-bleed
and capsular contracture), other complications related to implants
include frank rupture, infection, hematoma formation, and capsular
calcification. Implants also have been found to have a questionable
association with connective tissue disease.
Rupture of silicone can occur in two basic sites, each affecting
the imaging appearances of the breast differently. Rupture of the
implant with extravasation of its contents into the space
surrounding it (intracapsular location) is differentiated from
rupture through the fibrous capsule and into the tissue
(extracapsular location). Silicone can track into the axilla and be
visualized in lymph nodes. It also can extend into the duct system
and present as a silicone nipple discharge.
Clinical findings, including change in contour or location of
the implant, flattening of the implant, and breast pain are
associated with both intracapsular and extracapsular rupture.
Additionally, extracapsular rupture may be associated with palpable
masses (silicone granulomas) and silicone nipple discharge.
Mammographic and sonographic findings of implant rupture
A normal implant is seen on mammography as having a smooth
contour and an oval shape. The density of each type of implant will
vary: silicone is of high density; saline is less dense. A
double-lumen implant with a saline outer shell has a double-density
or bag-within-a-bag appearance.When the inner lumen of a
double-lumen implant ruptures, there is admixture of the
components. Mammographically, loss of the interface between
silicone and saline occurs, and an admixture of the densities will
result. Rupture of only the outer saline lumen will produce a
mammographic appearance similar to that of a single-lumen silicone
The mammographic finding of a change in implant contour (bulging
or peaking) suggests either herniation or intracapsular rupture.
Presence of such findings should prompt further studies to evaluate
the integrity of the implant. With extracapsular rupture,
mammography may demonstrate the appearance of free silicone
droplets in the breast or axilla. These are hyperdense and may be
Sonography is helpful for the evaluation of a possible implant
rupture, particularly in single-lumen silicone implants. The normal
implant has an echogenic line or interface surrounding an anechoic
oval space;10 textured implants appear as multilayered echogenic
lines anteriorly at the surface.11 Wrinkles or folds in the surface
can be seen on sonography as extending from the periphery of the
implant inward and changing in shape between the transverse and
sagittal planes. Because of the visualization of the internal lumen
within the anechoic space, sonographic imaging of double-lumen
implants can be confused with the pattern of intracapsular
Descriptions of the sonographic findings of intracapsular-space
implant rupture have included diffuse internal echoes, paralleling
horizontal lines,l2 and the stepladder (figure 4) sign.13 Berg et
all4 found the combination of the stepladder sign and
moderate-to-marked low level echoes (figure 5) to be present in 26
of 40 ruptured implants, with a sensitivity of 65% and a
specificity of 57%; Debruhl et all3 found these signs to be
associated with a 70% sensitivity and a 92% specificity for
With extracapsular rupture, sonography demonstrates a classic
"snowstorm appearance" (figure 6), caused by free silicone mixing
with the breast tissue. This area of hyperechogenicity has a
defined anterior margin, but a diffuse, indistinct posterior
margin. Additionally, hypoechoic "masses" (figure 7), representing
larger collections of free silicone, may be visualized in the
breast tissue and are usually associated with the snowstorm pattern
Magnetic resonance imaging (MRI) has proven to be the single
most effective tool for the diagnosis of silicone implant rupture.
When two orthogonal sequences are used to evaluate the
implant,l2,16 a sensitivity of 94% and a specificity of 97% has
been reported. MRI allows multi-planar imaging of the entire
implant and the surrounding tissue, addressing the limitations of
both mammography and ultrasound. In addition, it is not operator
dependent. MR can distinguish between silicone and normal breast
tissue because of its specifically-designed pulse sequences.
However, cost is a consideration, as MR is significantly more
expensive than either mammography or ultrasound. For optimal
resolution, MR is performed with the use of a dedicated breast
coil, with the patient lying in a prone position and the breast
resting dependently within the coil. Axial and sagittal or oblique
sagittal scan planes allow straight forward comparison with
mammographic images. Many different pulse sequences can be used
that distinguish between silicone, water, and fat.
Most medical-grade silicones are composed of methyl polysiloxane
with varying degrees of polymerization. The protons of the methyl
groups are the source of the MR signal. Though the implant envelope
is composed of silicone, the many additional cross-linkages between
the methyl groups renders it an elastic solid, with only minimal MR
There are a variety of suitable pulse sequences for imaging
silicone implants, the use of which is determined by the relative
Larmor precessional frequencies and the Tl and T2 properties of the
fat, muscle, and silicone content in the breast. At 1.5T,l2 the
relative resonance frequency of silicone is approximately 100 Hz
less than fat and 300 Hz less than water. The T1 value of fat is
less than that of muscle, which is less than that of silicone.
Therefore, on a Tl-weighted image, fat has the highest signal
intensity and silicone the lowest. Because the Tl of fat is so
short, its high signal intensity suppresses the intensities of the
other tissues; therefore, a fat-suppression sequence will
facilitate better visualization of the other tissues. Using
clinical suppression techniques, extracapsular silicone is seen as
a hypointense region within a hyperintense region. The fat
saturation pulse will also suppress silicone to some degree because
of the similarities in the resonance frequencies of fat and
In terms of T2 values, the T2 of silicone is greater than fat,
which is greater than muscle. Silicone, therefore, has a high
signal intensity on a T2-weighted image, with fat intermediate in
signal intensity and muscle the lowest. With the addition of water
suppression on a T2-weighted image, cyst fluid and muscle will have
a very low signal intensity, with silicone's remaining high. This
facilitates the easier detection of extracapsular leaks.
Other sequences which take advantage of the different relative
relaxation times of fat, silicone and water can be used. An
inversion recovery sequence with a short TI (STIR) will maintain a
high signal from silicone while suppressing the signal from fat. A
silicone-selective sequence can be accomplished with the use of a
chemical water-suppression pulse in conjunction with STIR.18
A normal silicone implant has a smooth, well-defined margin, and
should have a homogeneous signal intensity. A potential space
exists between the inner surface of the fibrous capsule and the
prosthesis shell. MR cannot normally differentiate between the
hypointense thin shell of an intact prosthesis and the fibrous
capsule. As the fibrous capsule thickens, hardens, and contracts,
it can squeeze and deform the intact prosthesis, causing infoldings
or creases in the envelope. This can be seen in both single-lumen
and double-lumen implants. An outer saline lumen often deflates
over time, and the collapse of the outer shell around the silicone
lumen results in extensive infolding. Rupture of a double-lumen
implant with a saline-filled outer lumen usually only involves the
outer saline-filled component; as this component is of a relatively
small volume (100 ml to 200 ml), there usually is no noticeable
change in the contour of the implant.
Normal radial folds are one of the most commonly encountered
findings in intact implants, and must be distinguished from
intracapsular rupture. Radial folds are hypointense lines that
emanate from the periphery of an implant at the fibrous
capsule-shell junction, and correspond to the infoldings of an
intact shell. These folds are often thicker than the lines
associated with the "linguine" sign because they consist of two
adjacent shell layers. They may be short and straight (simple), or
long and more curved (complex), and are frequently seen on multiple
contiguous images. Some implants have a polyurethane coating
covering the envelope surface. Because of this coating, a moderate
to large amount of peri-implant reactive fluid is seen
Rupture of an implanted prosthesis is the most common
complication associated with implants. Intracapsular rupture is
well demonstrated on MR. The "linguine sign,"-multiple, low-signal
intensity, wavy lines found within an implant-first described by
Gorczyca et al,16 is specific for intracapsular rupture, and is the
most reliable sign of this complication on MR imaging. These
low-signal-intensity lines represent pieces of free-floating
collapsed envelope surrounded by silicone gel, and are the
equivalent to the ultrasound "stepladder" sign (figure 8).l6,13 An
"inverted teardrop," "noose," or "keyhole" sign may be the only
indication of rupture. This represents a loop-shaped, hypo-intense
structure that is contiguous with the implant envelope,
representing a small focal invagination of the implant shell with
silicone on either side. This is caused by an extensive gel bleed
or by gel that has escaped through a focal rupture.l9,20
A subtle sign of early intracapsular rupture and shell collapse
is hypointense subcapsular lines which closely parallel the fibrous
capsule on contiguous images, corresponding to a minimally
displaced ruptured shell (figures 9 and 10). Phase-encoding
artifact, caused by patient motion during the imaging process, may
cause a hypointense curvilinear line which could be confused with
subcapsular lines if located in a subcapsular position. Repeating
the sequence with less patient motion or with a change in
phase-encoding direction should eliminate the artifact.
Hyperintense water droplets within the silicone are frequently seen
in conjunction with teardrops, subcapsular lines, or the linguine
sign. When seen alone, however, they are not indicative of
A diagnosis of extracapsular rupture is made when there is
silicone outside of the fibrous capsule, either within the breast
parenchyma or along the axilla or chest wall (figure 11). The
localization of free-silicone collections can be helpful in
preoperative planning. However, previous silicone injections or
residual silicone from prior rupture or implant explantation cannot
be distinguished from that of a new rupture.
A number of studies have examined the sensitivities and
specificities of mammography, ultrasound, and MRI for the detection
of implant rupture. However, only a limited number have compared
results of all three modalities in a single study population.
Gorczyca et al21 surgically placed forty single-lumen implants (20
ruptured/20 intact) within the abdominal walls of rabbits and
imaged these implants using mammography, ultrasound, MR, and CT.
The ruptures were all intracapsular, which would limit the
usefulness of mammography. MR was found to have the best
performance, with a sensitivity of 81% and a specificity of 93%. MR
was followed by sonography (sensitivity 70%; specificity 92%) and
mammography (sensitivity 11%; specificity 89%).2l
Everson et al,22 using mammography, sonography, MR, and CT
evaluated 32 women with 63 implants. All patients subsequently
underwent surgical explantation and 22 ruptures were found. MR
again had the best performance (sensitivity 95%; specificity 93%),
followed by sonography (sensitivity 59%, specificity 70%) and
mammography (sensitivity 23%, specificity 98%).22 Berg et al14
evaluated 144 implants (122 single-lumen; 22 double-lumen) with
surface-coil MR and ultrasound. These implants were subsequently
surgically removed. Overall, MR imaging for rupture was found to
have a sensitivity of 98% and a specificity of 9l% for patients
with intact implants. Ultrasound was found to have a sensitivity of
65% for rupture, based on the stepladder sign and/or low-level
echoes, and a specificity of 57%. An overall accuracy rate of 84%
was determined for MR, and 49% for ultrasound.14 AR
The authors wish to thank Ms. Louise Logan for her excellent
assistance in manuscript preparation.
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