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Breast implant diagnostic
breast implant
breast sonographie
implant imaging
capsular fibrosis
diagnostics
Diesch
Sophia
Prantl
Lukas
1141
1141
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Introduction
Introduction
Apart from its biological function, the female breast also has an erotic value as a natural attraction. Therefore, it is not surprising that in a society of self-optimization, the desire for a "perfect" breast also appears. But not only personal preferences but also serious illnesses such as tumours or accidents lead to the use of breast implants. Like many medical interventions, breast augmentation carries the risk of complications, such as capsular fibrosis or rupture of the implant. These initially often painless situations often go undetected. Magnetic resonance imaging is often used for diagnosis, but it is not available at all locations and is associated with certain costs and effort. Mammography is an alternative, but also sonography. However, their potential in the diagnostics of implants is not yet fully utilized.
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Construction of a breast implants
Construction of a breast implants
Breast implants are constructed in two layers. The outer layer, which is made of a silicone rubber and the inner layer, called a mandril. In production the mandril is the component of the implant which determines its shape. During the process of production, either the mandril gets dipped into liquid silicon or the silicon is sprayed onto the mandril. This process is repeated several times until the silicon layer reaches a certain thickness and evenness. Then the silicon implant gets removed from the mandril. In silicon breast implants is the silicon outer layer filled with a specific volume of the specific silicongel. The more cohesive the silicon gel is, the higher the gel-shell filling ratio. This leads to a stronger bonding from the silicon-gel to the outer silicon layer which leads to a better maintenance of the implants shape. Low shell-silicon bonding can lead to clinical visual deficiencies as rippling of the implant or collapse of the upper implant pole, if not used in the correct patient with specific soft tissue characteristics.
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Types of breast implants

Types of breast implants
Three common types of breast implants
Silicon gel breast implants
Silicon gel implants are divided into 5 generations. Since the first generation of breast implants from 1963, they underwent extensive changes and improvements. Implants from the first generation were teardrop shaped and filled with silicon gel .The second generation manufactured in the 1970s were filled with silicon gel with lower cohesivity, which improved the breast like, natural feeling of the augmented breast. Yet, they were more prone to gel bleeding and implant capsular rupture. The second big change was the invention of Polyurethan (PU) foam coating of the implants. The PU foam was meant to reduce the incidence of capsula fibrosis [1]. The third major innovation of the second generation was a double lumen implant. These implants contained two lumen, the outer lumen being filled with saline solution, which enclosed the inner lumen filled with silicon gel. The third generation of breast implants were rectified focusing on the implant surface. The newly developed elastomer coating led to reduced gel bleeding. Starting in the third generation, anatomically shaped breast implants were manufactured for the first time. Further more, the implant surface was available in smooth and textured. The nowadays used fifth generation of breast implants, is made out of a more cohesive gel which reduces the risk of gel bleeding and leakage even more. The complication of capsularfibrosis was also reduced [2, 3]. 
Breast implants are categorised as smooth, microtextured and macrotextured based on their electron microscopic surface texture of their outer silicon elastomer surface [4]. These different surface types differ in the way they interact with the surrounding soft tissue as descirbed by Munhoz et al. [5]
Saline breast implants:
Saline breast implants are filled with 0,9 % NaCl Solution. The outer silicon shell is in comparison to silcion-gel implants thicker. Due to higher rates of compliactaions such as leakage, saline breast implants are second choice for breast surgery [8]. In addition, breast implants filled with saline solution tend to cause aesthetically noticeable complications such as curling and wrinkling of the implant.
Structured breast implants (IDEAL Implant):
These new structured implants are made of both saline solution and a silicone outer shell. The implant consists of two lumens within two nested shells, which are all attached at a patch on the back of the implant. The inner lumen ist filled with approximately two thirds of saline solution, the outer lumen with one third. Within the outer lumen is a baffle structure floating, which is not atteched to the shells. This structure is designed to restrict movement of the saline solution in the outer lumen of the implant. The amount of baffle shells is depending on the implant size and does vary. The internal structure of the implant emphasizes the upper pole when the patient is standing upright and also reduces fluid movement. Preoperatively, the implant is inserted empty and once it is perfectly positioned it is filled. IDEAL implants therefore require a much smaller skin incision. Due to the multi-chamber structure and a tear only leads to emptying of one chamber and does not damage the entire implant. Further more is the saline solution in case of implant rupture absorbed by the surrounding breast tissue.   [7].
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Complications following mammoplasty
Complications following mammaplasty
There are acute and late complications following mammoplasty. 
Acute
Late
bleeding

capsular contracture
infection
 rupture (intracapsular and extracapsular rupture)
tenderness
 herniation
pain
seroma
 loss of nipple sensation
infection (late/chronic)
 assymetrie
pain (chronic)
Capsular contracture following fibrosis
The most common complication after augmentation or reconstruction with implants is capsular contraction [9], with a prevalence ranging from 5% - 19%[10]. Capsular fibrosis is the result of the body's own reaction to the foreign tissue. Initially there is a cytokine-mediated migration of t cells and macrophages. Later, the inflammatory cells decrease and fibroblasts take their place, which are ultimately held responsible for the formation of the fibrosis[11, 12]. But also bacterial contamination seems to play a vital role in development of fibrosis [13]. A drug-based anti-inflammatory therapy approach has so far shown contradictory results. Ultimately, the only solution for both complications is explantation and implant replacement. A possibility for early detection of the changes and treatment without surgery would be desirable, but is currently not available.The contraction can occur weeks to years after implantation. 
Baker classification
Firmness/pain
Implant
Implant visibility
I
soft
non-palpable
not visible
II
minimal
palpable
not visible
III
moderate
easy-palpable
distorsion visible
IV
severe
hard, tender, cold
marked distorsion
Capsular calcification 
Focal or diffuse capsular calcifications can be seen along the implant surface. The calcification is due to micro leakage and gel bleeding of the breast implant. They do not indicate a rupture of the implant and have no clinical significance.  
Implant rupture
As the second most frequent complication after breast augmentation is implant rupture an important complication. A rupture is a tear or the formation of a small hole in the outermost silicone layer. Studies show that this occurs in 1.1 - 2.1 % of the implants examined after 6 years. After 10 years it is already 10 - 16%[8].
Reasons for a implant rupture:
Damage from surgical instruments during mammoplasty
Shell swell (reduction of the stability of the silicone shell by shifting liquid within the implant)
Blunt trauma
In the early stages of rupture patients do normally not develop symptoms, as most ruptures happen „quiet“[8]. Ruptured saline implants deflate very quickly in comparison to gel implants. First conspicuous features  of a ruptured implant can be stiffness of the breast, change in shape, and later on breast pain.
Intracapsular implant rupture 
Intracapsular implant rupture is a rupture of the shell: silicon gel leaks out of the implant and remains confined within the periimplant fibrous capsule. 
They are the most common type of implant rupture and easiest to detected with MRI due ti its high sensitivity. There are several MRI imaging signs, described by Mund et. al.[9], which depicted the degree of intracapsular rupture. Diagnostic of intracapsular rupture can be confounded by ultrasound.
Table 2: MRI Imaging sings if intracapsular breast implant rupture [24]
Imaging Sign
Degree of Collapse
Description of Rupture
Keyhole sign/ noose sign
uncollapsed rupture
Silicon gel is contained in a radial fold
Subcapsular line sign
minimal collapsed rupture
extruded silicon gel separates the elastomer shell form the fibrous capsule
Linguine sign
partial-full collapsed rupture
silicon gel entirely in the intracapsular space
Extracapsuar implant rupture
Mammography can detect cases of extracapsular implant ruptures, showing irregular collections of free silicon gel outside the implant. Further can silicon be detected in axillae lymphatic nodes.  
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Diagnostic modalities
Diagnostic modalities
There are different possibilities for the examination of breast implants. First and foremost is the clinical examination, which today is increasingly being pushed into the background by apperative methods and is highly dependent on the experience of the examiner. The radiological possibilities range from MRI and ultrasound to classical X-rays in mammography and CT. Nevertheless, breast implants do not require routine examination annually. If there is, due to symptoms or the physical examination, clinical concern of the implants integrity, ultrasound should be the first-line diagnostic modality. 
If the ultrasound findings are questionable, or if there is persisting clinical concern, then MRI is indicated.
MRI
MRI is widely accepted as the imaging method of choice to evaluate the implants integrity with a sensitivity and specificity of greater than 90% in evaluating implant rupture [14]. Current recommendations by the FDA are that women with silicone breast implants, should undergo MRI Scans 3 years after augmentation and every second year afterwards [15]. In a recent a study be the European Institute of Oncology it was concluded, that MRI should be the modality of choice to diagnose implant rupture in asymptomatic women due to the superior accuracy compared to ultrasound. However, it is recommended to do routine screenings with ultrasound imaging. If irregularities using ultrasound are detected, MRI imaging should follow to verify (29).
Signs of implant rupture: Quelle 24
Imaging Sign
Degree of Collapse
Description of Rupture
Keyhole sign/ noose sign
uncollapsed rupture
Silicon gel is contained in a radial fold
Subcapsular line sign
minimal collapsed rupture
extruded silicon gel separates the elastomer shell form the fibrous capsule
Linguine sign
partial-full collapsed rupture
silicon gel entirely in the intracapsular space
Mammography
Mammographie is the most used and inexpensive modality. It has only a low sensitivity due to (11-69%) high radiopaque of silicon [13, 17-19]. Breast Implants represent themselves in mammography as uniformly dense. A further evaluation of the implant, can be made only limited [14]. Therefore implant ruptures can be overseen. 
The benefits of Mamography are the following: a detection of extra capsular ruptures is possible ([17]). 
Possible signs of implant rupture are (non-specific): 
Irregular shape of the implant
Lobular and/or spherical density
Herniation (protrusion of the implant through opening in the fibrous capsule)
Bulging
Undulations
Mammography remains the imaging method to detect breast cancer and not the integrity of breast implants. However the type of implant can be determined and it is possible to distinguish between saline an d silicon single lumen implants. Further free silicon in cases of extracapsular implant rupture can be detected. For the verification of a intracapsular rupture are additional imaging methods as MRI or ultrasound necessary. 
Ultrasound 
Ultrsaound should be a standard method in the evaluation of both, asympomatic and symptomatic breast implants.
Pros:
Sonongraphy is a ubiquitous available, expeditiously, easy for the patient to undergo with nearly no discomfort and cheap imaging method. In opposite to MRI and Mammography it can detect extra and intracapsular ruptures: 
Extracapsular rupture: snowstorm sign[23]
Intracapsular ruptures: stepladder sign [24]
Cons:
high operator dependent. Therefore the examination should be performed by a  specially trained breast sonographer
Technical ultrasound considerations
The sonography of breast implants is highly operator dependent and should be pursued by a special trained breast sonographer. Further more, as shown in our studies, a high frequency probe 12,5-33 MHz (linear) should be used in the evaluation of implants. Only the high frequency probes allow a precise imaging of the capsule-elastomer-shell complex. The downside to high frequency sonography is a limited examination depth. In women with larger breast it should be considered to use a lower frequency (9-16 MHz) to gain further depth. Light compression on the breast should be applied during scanning.
Implant appearance in ultrasound
Intact implants are anechoic [17]. If a fibrous capsule starts to built around the implant, a capsular-shell-complex can be shown using ultrasound technology. This fibrouse-elastome-shell complex appears in sonography mostly as a trilaminar line [19, 21]. The outer surface of the capsule is shown by the outer line in the ultrasound image. The middle line corresponds to the inner surface of the capsule and the outer surface of the elastomer shell. The inner line represents the inner surface of the elastomer shell [18, 21].One should be aware, that orientation marks on the implants can lead to interruption of the trilaminar lines. This should not be mistaken as a implant rupture.Abnormalities as protrusion, herniation, bulging and contour interruption of the elastomer shell occur in areas where the fibrous capsule is thinned and could indicate a a problem with the implant integrityreverberation echoes in the near field must be distinguished from the implants echogenicity. Light compression while sonography can minimize these reverberation artifacts. Further it is possible to detect radial folds. These folds are dynamic and not fixed in position and size.
Extracapsular rupture in sonography:
Snow strom appearance = extravastaed silicon
Homogeneous hyperechoic nodule
Poersterior shadowing
Extracasular silicon granulomas (isoechoic nodule)
Double lumen implant rupture:may simulate single lumen implant
Silicon in lymph nodes (may be associated with extracapsular implant rupture)
Hyperechoic lymph nodes (beginning in the hilum and progressing to the cortex) = snowstorm shadowing

Intracapsular rupture in sonography
Steppladder sign= multiple fold of the collapsed implant shell floating with extravasated silicon, occures in large ruptures with nearly or complete collaps
Double lumen implant rupture: mixing of saline and silicon gel components: mottling of echogenicity
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Examination Algorithme
Examination Algorythm
Ultrasound 
Ultrasound preset
For breast implant examination a high frequency linear probe would be used to achieve high resolution of the implant surface. 
- Preset should be changed to mamma , ideal frequency range12,5-33MHz, SRI 3, no THI, color coded imaging for B-Mode, cross beam high
- always examination of both breasts
- if possible implant type should be known (mikro-, makrotextured or smooth, saline, silicon, double lumen, expander, single lumen etc. 
- sonographic findings should always be correlated with MRI (goldstandard)


MRI
- if you suspect implant defects/rupture an MRI has to be performed as it is the gold standard in breast implant diagnostics
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References