Surface imaging of breast implants using modern high-frequency ultrasound technology in comparison to high-end sonography with power analyses for B-scan optimization 1

Abstract

AIM:

This study aims to evaluate optimized breast implant surface-structure analysis by comparing high-end ultrasound technology with a new high frequency technique. This comparative study used new breast implants with different surfaces in an in vitro setting.

METHODS:

Nine idle silicon or polyurethane (PU) breast implants were examined by two investigators in an experimental in vitro study using two high-end ultrasound devices with multi-frequency transducers (6–15 MHz, 9–16 MHz, 12.5–33 MHz).

The ultrasound B-Mode was optimized using tissue harmonic imaging (THI), speckle reduction imaging (SRI, level 0–5), cross beam (high, medium, low) and photopic.

Using a standardized ultrasound protocol, the implants were examined in the middle (point of highest projection) and lateral, by two independent examiners.

Image evaluation was performed on anonymized digital images in the PACS. The aim was to achieve an artifact-free recording of the surface structure, the surface coating, the total image structures and, as far as possible, an artifact-free internal representation of the implants.

For independent surface evaluation a score was used (0 = undetectability of surface structures, rich in artifacts, 5 = best possible, artifact free image quality).

RESULTS:

The quality of ultrasound imaging of breast implant surfaces after the optimization of B-Scan differed significantly comparing high-end ultrasound technology with modern high-frequency ultrasound technology (p < 0,05).

The following setting has been found to be the best setting with the highest image quality:

B-Mode, SRI value 3, Crossbeam high level with color coded imaging for B- mode. In the total examined frequency range of 6–33 MHz, the highest image quality was found in the average frequency range of 12.5–33 MHz at both measured points. For both devices, device 1 (high-end) and device 2 (high frequency) ultrasound, the image quality was in the

12.5–33 MHz frequency range with an average image quality of 3.236. It was significantly higher, than in the lower frequency ranges and the same frequency range with THI. (p < 0,05).

The image quality of the high-end sonography device was superior to the conventional high-frequency ultrasound device in all frequency ranges.

CONCLUSION:

High-end ultrasound imaging technology was superior in the quality of implant surface evaluation in comparison to high-frequency ultrasound sonography. The gained knowledge can serve as a basis for further multicenter clinical application and studies with the aim to develop an objective, precise tool to evaluate the implant and the surrounding tissue with ultrasound.

Keywords

Breast implant ultrasound high-frequency ultrasound breast implant imaging

1 Introduction

The global demand for breast implants has increased steadily over the last years. Main indications for the use of breast implants continues to be reconstructive breast surgery after mastectomy and mamma carcinoma, reconstructive surgery for breast asymmetry as well as cosmetic surgery. Capsular fibrosis or capsular contracture is the most common adverse effect of breast implants, with an incidence of almost 10% [1]. This excessive foreign body reaction is caused by chronic inflammation with consecutive collagen synthesis [2, 3] and leads to a steadily increasing contraction of the capsular surrounding the implant [4] and thus to its eventual hardening and deformation. Patients complain of an increasing firmness of the breast as well as pain with more advanced capsular fibrosis. Until now, capsular fibrosis has been classified according to the clinical aspect in palpation, according to Baker [5].

The most available method to examine and evaluate a suspect implant is by ultrasound. Despite the high number of patients with capsular fibrosis, there are hardly any publications describing sonographic changes in breast implants with capsular fibrosis.

The aim of the study was to optimize the ultrasound procedure so that diagnostic standards for the early detection of complications can be established, thereby avoiding costly follow-up operations such as changing the implants.

The current gold standard in the diagnosis of ruptured breast implants still is the surgical removal and examination of the removed implant. It is not yet clear which non-invasive imaging technique detects rupture and implant changes with high sensitivity [6].

A complete recording of the breast implant, the thoracic wall and surrounding breast tissue is also possible using magnetic resonance imaging (MRI). However, MRI diagnostics is only available in limited quantities and is very cost-intensive. However, modified examination techniques allow a higher sensitivity and higher specificity of MRI diagnostics, especially in cases of implant rupture [7, 8]. MRI imaging shows the “linguini sign” described by Gorczyca et al. as pathognomonic for intracapsular collapse [9]. Mammography represents a theoretically attractive option for implant diagnostics. Nevertheless, it is also not an alternative due to general low sensitivity in the case of implant failure [9 –11] radiation exposure and, especially, cases of advanced capsular fibrosis, very painful examination.

In contrast, sonography represents a cost-effective, ubiquitously available, painless method, free of radiation exposure in the diagnosis of breast implants. Especially new high-resolution probes allow high image quality and high image resolution in higher frequency ranges, but are limited in terms of penetration depth. While ultrasound probes are constantly being developed, further studies on the role of sonography in breast implant diagnostics are rather scarce. In this study, two sonography devices are compared according to their quality of surface imaging of breast implants.

2 Materials and methods

For the study nine commercially available breast implants were used (Table 1).

Table 1
Used ideal breast implants with different surface structure, shape, volume and cohesivity.

Probe Manufacturer Properties (surface/ shape/volume/cohesivity/model No.)

P1 A Mentor Micortextured/round,/250cc/Cohesiv II/M + C II

P1 B Mentor Micortextured/anatomical/245cc/Cohesiv II/CPG321

P1 C Mentor Micortextured/round/250cc/Cohesiv I/M + C

P1 D Mentor Smooth/round/300cc/Cohesiv I/6433613

Poly 1 Polytec Macrotextured (polyurethane)/round/255cc/30725

Poly 2 Polytec Microtextured/anatomical/255cc/20725

Poly 3 Polytec Microtextured/round/255cc/15726

Poly 4 Polytec Macrotextured (polyurethane)/round/255cc/30735

Poly 5 Polytec Microtextured/anatomical/255cc/20735

Probe	Manufacturer	Properties (surface/ shape/volume/cohesivity/model No.)
P1 A	Mentor	Micortextured/round,/250cc/Cohesiv II/M + C II
P1 B	Mentor	Micortextured/anatomical/245cc/Cohesiv II/CPG321
P1 C	Mentor	Micortextured/round/250cc/Cohesiv I/M + C
P1 D	Mentor	Smooth/round/300cc/Cohesiv I/6433613
Poly 1	Polytec	Macrotextured (polyurethane)/round/255cc/30725
Poly 2	Polytec	Microtextured/anatomical/255cc/20725
Poly 3	Polytec	Microtextured/round/255cc/15726
Poly 4	Polytec	Macrotextured (polyurethane)/round/255cc/30735
Poly 5	Polytec	Microtextured/anatomical/255cc/20735

Breast implants are categorised as smooth, microtextured and macrotextured based on their electron microscopic surface texture of their outer silicon elastomer surface [12]. These different surface types differ in the way they interact with the surrounding soft tissue as descirbed by Munhoz et al. [13]

Furthermore breast implants vary in: shape (round and anatomical shape), structure, cohesivity and volume [14]. This wide range of variability makes it possible to find the ideal breast implant for every patient and their individual breast anatomy.The most commonly used implant structures are the following as described by Alba et al. [15]: Single lumen implant: filled with silicon or saline solution; standard double lumen implants: inner lumen filled with silicon gel, outer lumen filled with saline; reverse double lumen implants: inner lumen filled with saline solution, outer lumen filled with silicon gel; Expanders.

The breast implant shell consists of three different layers that can be visualised with ultrasound [16].

The breast implants were evaluated by two examiners in consensus using two high-end ultrasound devices (GE, LOGIQ E (device 2) [17] and Mindray, Resona 7 (device 1) [18]).

The implants were examined with three different multifrequency probes, each with variable frequency ranges from 6–15 MHz, 9–16 MHz, and 12.5–33 MHz. The focus was on optimizing the ultrasound imaging of the implant surface structures.

The following modalities for image optimization were used: Transmission frequency adjustment, speckle reduction imaging (SRI), Tissue harmonizing imaging (THI), cross-beam, Color D, B-image (Photopic). The following setting was found to be the optimal combination: B-scan, SRI value 3, crossbeam high, Color D and Grey F. Examiner 1 was an experienced Ultrasound-specialist with more than 3000 examinations/year over 20 years as senior physician in radiology. Examiner 2 was a resident in plastic and aesthetic surgery without sonography experience.

The implants were removed from the sterile packaging, placed on a sterile surface on an examination table and examined using sterile ultrasound gel. The examination was performed at two areas per implant: At the point of highest projection ventrally and at the lateral upper quadrant at 9 o’ clock ventrally (Fig. 1). To assess the image quality of the surface of the implants, a scale was given between an optimized, artifact-free result (5 points), an image with little artefacts (4 points), an image with artefacts and less structural image quality (3 points), image with rich artefacts (2 points), an image quality with severe artefacts which still remains evaluable (1 point) up to a non-evaluable implant surface with massive artefacts (0 points).

Fig. 1

Breast implants examined with GE Ultrasound probe (a, b) (L146WU) and with Mindray ultrasound probe (c, d) (L14-6WU) (a) Examination on point of highest projection; (b) Examination of the lateral edge 9 o’clock position; (c) Examination on point of highest projection; (d) Examination of lateral edge at 9 0’ clock;

Special care was taken not to put pressure through the transducer on the surface of the implants. The aim was to achieve a preferably artifact-free recording of the surface structure, the implant coating, the image structures and, as far as possible, the internal representation of the implants.

The evaluation of the image quality was performed independently of two readers on anonymized digital images in the PACS.Statistical analyses were performed using SPSS software for Windows 10 Enterprise LTSC Version 1809 (SPSS Version 25; SPSS Inc., Chicago, IL). Mulivariate-Test (Pilai-Spur, Wilks-Lambda, Hotelling-Spur, Roy), T-test, Paired Difference Test, Levene-Test, multifactorial variance analysis) were performed. Probabilities less than 0.05 were considered significant.

3 Results

The image quality of ultrasound imaging of the breast implant surfaces comparing between high-end ultrasound technology to modern high-frequency ultrasound technology differed significantly (p > 0,05). For all 9 implants, it was possible to examine both the implant ventral wall and posterior surface at the two predetermined examination points (at the point of highest projection as well as at the lateral upper quadrant at 9 : 00 o’clock). In addition, all implants could be examined with all probes and thus all frequency ranges. In the total examined frequency range of 6–33 MHz, the highest image quality resulted in an average frequency range of 12.5–33 MHz at both measured points (Fig. 2).

Fig. 2

Ultrasound device 1: high-end ultrasound image taken on point of highest projection of breast implant; (a) ultrasound frequency range from 6,0–13,0 MHz with inferior image quality; (b) superior ultrasound image quality of breast implants in vitro in the high frequency range from 12,5–33 MHz.

The use of SRI (Speckle reduction imaging) has shown a beneficial effect on the surface representation at setting 3 from possible steps of 1–5.

For both, device 1 (high-end) and for extremely echogenic surface structures, the additional use of photopic has proven to be helpful. The additional use of THI did not lead to a significant improvement of the surface representation. The special surface structure of the implants (PU, text, smooth) has no significant effect on the quality of the image.

The following setting has been found to be the best setting with the highest image quality: B-Scan, SRI 3, B-Scan, Crossbeam high.

For both, device 1 (high-end) and device 2 (high-frequency) ultrasound, the image quality in the 12.5–33 MHz frequency range with an average image quality of 3.236 is significantly higher, than in the lower frequency ranges and the same frequency range with THI (Fig. 3).

Fig. 3

Ultrasound image quality in frequency range 6–13 MHz, 9–16 MHz, 12,5–33 MHz, 12,5–33 Mhz + THI comparing high-end ultrasound device (1) with high frequency ultrasound device (2).

For both, device 1 (high-end) and device 2 (modern high frequency) ultrasound, the image quality in the 12.5–33 MHz frequency range with an average image quality of 3.236 was significantly higher than in the lower frequency ranges and the same frequency range with THI.

The image quality in the frequency range of 12.5–33 MHz was significantly (p = 0.000) better compared to the frequency range of 6–13 MHz with a standard deviation of 0.819±0.171.

The same picture can be seen when comparing the frequency ranges 12.5–33 MHz and 9–16 MHz. Here the picture quality of the frequency range 12.5–33 MHz was superior by 0.361±0.171 (p = 0.037). Using tissue harmonic imaging (THI) in the frequency range of 12.5–33 MHz did not improve the picture quality.

Here the frequency of 12.5–33 MHz was significantly better (p = 0.002) with 0.542±0.171 on average with a significance of p = 0.002 compared to the same frequency with THI.

As shown in Fig. 3 the image quality of the high-end sonography device (device 1) was superior to the conventional high-frequency ultrasound device (device 2) in all frequency ranges. In the 6–13 MHz frequency range, device 1 showed an average image quality of 2.528±0.114 compared to device 2 where the average image quality was 2.306±0.195.

The same trend was found at the frequency of 9–16 MHz. Here the picture quality of device 1 was on average 2.972±0.114, compared to device 2 where the average picture quality was 2.778±0.195. At the frequency range of 12.5–33 MHz, device 1 with an average picture quality of 3.472±0.114 was also superior to device 2 with 3.000±0.195 on average.

At the same frequency range of 12.5–33 MHz, the use of THI, lead to no improvement of the image quality. Nevertheless, ultrasound device 1 with an average image quality value of 3.083±0.114 was superior to ultrasound device 2 with an average image quality value of 2.306±0.195 (Fig. 3).

As shown in Fig. 4 there was a clear difference in the image quality of the anterior edge of the implant (blue) compared to the posterior edge (red) of the implant for both, device 1 and device 2. With an average value of 3.319±0.081, the image quality of the anterior edge (blue) of device 1 was significantly better than of device 2 2.903±0.138. The ultrasound image quality of the posterior edge (red) was with an average value of 2.708±0.081 clearly superior with device 1 compared to device 2, where the average value of the image quality was 2.292±0.138.

Fig. 4

Image quality of anterior (blue) and posterior implant surface (red) comparing ultrasound device (1) high-end ultrasound with ultrasound device (2) high-frequency ultrasound device.

4 Discussion

Due to increasing numbers of in vivo breast implants, a reliable examination is required, which is also easily accessible and available. With an incidence of 10.6% [1], capsular fibrosis is the most common complication associated to breast implants. Furthermore, the number of cases of implant-associated anaplastic large-cell lymphoma (ALCL) is steadily increasing [19].

Therefore a reliable imaging examination is required, which should show the intactness of the implant, tears in the implant shell, an incipient capsular fibrosis before visible changes in the breast shape occur. Special efforts should be made, to diagnose and classify exactly changes in the surface structures and specific interactions of tissue, leaks, degree of fibrosis as well as implant-associated anaplastic large cell lymphoma. So far, there is only a small amount of data available on sonographic standards about specific breast implant diagnostics.

As already mentioned in the introduction, MR diagnostic is not a suitable method for comprehensive evaluations and diagnostics of breast implants due to high costs.

Therefore, it is important to define a ubiquitous, easily reproducible and sensitive examination method. Sonography is in particular an essential component of complementary breast imaging and implant diagnostics. Nevertheless, there is hardly any literature focusing on sonographic implant diagnostic. Sowa et. al. were able to show, that short wave elastograhy is a better tool to asses the degree of capsular contraction surrounding the breast implant in correlation with the bakers score [20]. The aim should be to combine the highest clinical experience in one’s own department with the best possible technical knowledge. Hence, high-end sonography should be implemented in the clinical routine, as a significant improvement in image quality can be seen, especially in the high-frequency range. Although our trial has demonstrated the superiority of high-end sonography, it should be noted that the conventional routine ultrasound has also its place in the initial assessment of breast implants. The following B-scan parameters have proven to be advantageous both in modern high-frequency ultrasound technology and in high-end sonography: B-scan, SRI 3, Crossbeam high, Colour D and Grey scale F.

The normal breast implant is an anechoic structure with an echoic capsule. After the implant is placed in situ, a fibrous capsule forms around the implant. Like any other imaging technique, ultrasound imaging of breast implants cannot differentiate the fibrous capsule from the implant capsule.

The fibrotic capsule can only be differentiated from the implant capsule if there is fluid between the layers [16]. Further limitations of ultrasound image quality in general are artifacts, which mostly occur with implants. Artefacts are image alterations caused by physical phenomena of ultrasound and its interaction with tissue. To avoid misinterpretation and misdiagnosis of ultrasound images of breast implants, it is inevitable to know which artefact can occur. The most relevant artefacts in breast implant imaging are: Reverberation are artefacts that can be seen in normal breast implants. They are echoic lines which run parallel to the implant capsule. They should not be misinterpreted as an intracapsular rupture Futher arrtefacts are radial folds which are normal findings in breast implants. They appear as an irregular contour of the implants capsule or as echogenic concave lines, which run from the periphery to the interior of the implant. If they are prominent, they can be misdiagnosed as intracapsular ruptures. If the implant is positioned retroglandular or subpectoral the ultrasound probe will a reduced sensitivity. Acoustic shadowing can be seen if a strong capsula is formed around an implant. This leads to a total absorption or reflection of ultrsaound waves This means that tissue cannot be represented after the shadowing layer [21].

Another limitation of breast implant ultrasound is the distance between the individual layers of the implant shell. As in the diagnosis of the intima-media complex in vascular imaging, artefacts occur when interfaces of different density are less than 5 mm apart. Here, due to the technical limitations, no differentiated resolution between the closely adjacent boundary layers is possible. This should always be taken into account in breast implant ultrasound [21].

Similar publications on B-image optimization as well as the use of high and low frequency transducers for the visualization of implant surfaces are not yet available.

Furthermore, it was observed that the use of THI (Tissue Harmonic Imaging) did not yield any advantage depending on the implant surface. In contrast to the study by Mesuroll et al. [22], the image quality did not improve significantly when using THI.

However, this is different in breast diagnostics without implants. Here a definite optimization of image quality using THI is described [23, 24]. If the experimental set-up is viewed critically, it is to be criticized that no lead-in distance between implant and transducer was used. Especially with PU-coated implants, what led to a more difficult representation of the implant surface.

Therefore, in a subsequent study a lead-in distance will be used as an intermediate layer between the implant and the transducer. This material should resemble the natural breast tissue as much as possible. Considering the differences in the image quality of both sonography devices, a transducer in the frequency range of 12.5–33 MHz seems to be most appropriate for routine breast implant ultrasound. Conventional probes in the lower frequency ranges produced significantly poorer image quality compared to high-frequency sonography. Furthermore, there is a significant difference between a device with high-frequency ultrasound technology compared to high-end sonography. Considering the low reimbursement for a routine breast ultrasound in Germany of 100€ maximum, this superior high-end technology can still not be a standard for all clinics, since the purchase of such a device costs between 100 000€ - 120 000€. However, the increase in quality through the use of high-end ultrasound technology suggests that such a technique and high-frequency transducers for breast diagnostics should be available at selected certified breast centers, preferably in interdisciplinary cooperation between radiology, gynecology and plastic surgery. The number of cases in this experiment is small. Nevertheless, the available data can serve as a basis for future multicentre studies.

5 Conclusions

The study revealed that the following B-scan parameters, for breast implant ultrasound imaging, have proven to be advantageous both in modern high-frequency ultrasound technology and in high-end sonography: B-scan, SRI 3, Crossbeam high, Colour D and Grey-scale F.

With the stated setting adjustments, we were able to detect an ideal transducer frequency and achieved a superior quality of ultrasound images of breast implant surfaces.

Using these optimized settings, ultrasound technology can be a standard in breast implant diagnostics.

Furthermore, high-end ultrasound technology was superior in the quality of implant surface evaluation in comparison to high-frequency ultrasound sonography.

In addition, ultrasound technology is more cost effective in comparison to MRI and also ubiquitously available.To conclude: the optimization of the ultrasound setting for breast implants can also provide less technically experienced examiners with the means to achieve an optimal image and surface representation of breast implants.

Author contributions

Conceptualization, L. Prantl, F.Jung; methodology and examination, E.M. Jung, S.T.Diesch; validation, L.Prantl., F. Jung., E.M: Jung.; formal analysis, S.T. Diesch.; investigation, S.T. Diesch.; resources, S.T. Diesch.; data curation, S.T. Diesch.; writing— original draft preparation, S.T. Diesch.; writing— review and editing, L.Prantl, E.M. Jung, F. Jung.; visualization, S.T,Diesch.; supervision, E.M. Jung.; project administration, E.M. Jung. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional review board statement

Not applicable.

Conflict of interest

The authors declare no conflict of interest.

Ethical review was not necessary for this study.

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