Artificial Intelligence-Enabled Simulation of Gluteal Augmentation: A Helpful Tool in Preoperative Outcome Simulation?

BACKGROUND

While the buttock region is considered an esthetic hallmark, the Brazilian butt lift (BBL) remains controversially discussed in the plastic surgery community. This is due to its contentious safety profile. Thus, informed consent and patient education play a key role in preoperative planning. To this end, we aimed to program an easy-to-use, widely accessible, and low-budget algorithm that produces reliable outcome simulations.

METHODS

The conditional generative adversarial network (GAN) was trained using pre- and postoperative images from 1628 BBL patients. To validate outcome simulation, 25 GAN-generated images were assessed deploying 67 Amazon Mechanical Turk Workers (Mturks).

RESULTS

Mturks could not differentiate between GAN-generated and real patient images in approximately 49.4% of all trials.

CONCLUSION

This study presents a free-to-use, widely accessible, and reliable algorithm to visualize potential surgical outcomes that could potentially be applied in other fields of plastic surgery.

Is 3-Dimensional Scanning Really Helpful in Implant-Based Breast Reconstruction?: A Prospective Study

BACKGROUND

Breast reconstruction is an integral part of breast cancer treatment, and implant-based breast reconstruction is the most commonly used method worldwide. However, there is still no technique that allows surgeons to predict the volume of the required implant. Although computed tomography and magnetic resonance imaging provide adequate representations of the breast, these procedures are time-consuming, expensive, and expose patients to radiation. Therefore, there is a need for safer, noninvasive alternatives for preoperative breast volume measurements.

PATIENTS AND METHODS

This study is a prospective review of 12 patients with early-stage breast cancer who underwent nipple-sparing mastectomy and immediate breast reconstruction with implants. Preoperatively, the Artec Eva 3D scanner was used to acquire volumetric measurements of the breasts. Intraoperatively, the volume of the mastectomy specimen was measured using the water displacement method. Correlations among the preoperative breast, mastectomy specimen, and estimated and final implant volumes were analyzed through Pearson correlation coefficient. A correction prediction factor of 85% was applied where necessary. Patient and physician satisfaction were evaluated 3 months postoperatively.

RESULTS

Our study found a statistically significant correlation between the preoperative breast volumes measured by the Artec Eva 3D scanner and intraoperative mastectomy specimen volumes (r = 0.6578). There was no correlation between the preoperative breast volumes and final implant volumes, mastectomy specimen volumes and final implant volumes, and estimated implant volumes and final implant volumes.

CONCLUSIONS

Although the Artec Eva 3D scanner can offer relatively accurate measurement of breast volumes, multiple studies still need to be done to determine how these data can be applied to the mastectomy procedure and breast implant selection. It may be more applicable for preoperative planning in breast augmentation surgery. Future surgeons should also take into account that variabilities in natural breast size, tumor size, cancer stage, and in patient and physician preferences all influence the outcome of breast reconstruction surgery.

Three-dimensional simulation of aesthetic outcome from breast-conserving surgery compared with viewing photographs or standard care: randomized clinical trial

INTRODUCTION

Over half of women with surgically managed breast cancer in the UK undergo breast-conserving treatment (BCT). While photographs are shown prior to reconstructive surgery or complex oncoplastic procedures, standard practice prior to breast conservation is to simply describe the likely aesthetic changes. Patients have expressed the desire for more personalized information about likely appearance after surgery. The hypothesis was that viewing a three-dimensional (3D) simulation improves patients' confidence in knowing their likely aesthetic outcome after surgery.

METHODS

A randomized, controlled trial of 117 women planning unilateral BCT was undertaken. The randomization was three-way: standard of care (verbal description alone, control group), viewing two-dimensional (2D) photographs, or viewing a 3D simulation before surgery. The primary endpoint was the comparison between groups' median answer on a visual analogue scale (VAS) for the question administered before surgery: 'How confident are you that you know how your breasts are likely to look after treatment?'

RESULTS

The median VAS in the control group was 5.2 (i.q.r. 2.6-7.8); 8.0 (i.q.r. 5.7-8.7) for 2D photography, and 8.9 (i.q.r. 8.2-9.5) for 3D simulation. There was a significant difference between groups (P < 0.010) with post-hoc pairwise comparisons demonstrating a statistically significant difference between 3D simulation and both standard care and viewing 2D photographs (P < 0.010 and P = 0.012, respectively).

CONCLUSION

This RCT has demonstrated that women who viewed an individualized 3D simulation of likely aesthetic outcome for BCT were more confident going into surgery than those who received standard care or who were shown 2D photographs of other women. The impact on longer-term satisfaction with outcome remains to be determined.Registration number: NCT03250260 (http://www.clinicaltrials.gov).

Prediction of the Ideal Implant Size Using 3-Dimensional Healthy Breast Volume in Unilateral Direct-to-Implant Breast Reconstruction

Background and objectives: There is no consensus regarding accurate methods for assessing the size of the implant required for achieving symmetry in direct-to-implant (DTI) breast reconstruction. The purpose of this study was to determine whether the ideal implant size could be estimated using 3D breast volume or mastectomy specimen weight, and to compare prediction performances between the two variables. Materials and Methods: Patients who underwent immediate DTI breast reconstruction from August 2017 to April 2020 were included in this study. Breast volumes were measured using 3D surface imaging preoperatively and at postoperative three months. Ideal implant size was calculated by correcting the used implant volume by the observed postoperative asymmetry in 3D surface imaging. Prediction models using mastectomy weight or 3D volume were made to predict the ideal implant volume. The prediction performance was compared between the models. Results: A total of 56 patients were included in the analysis. In correlation analysis, the volume of the implant used was significantly correlated with the mastectomy specimen weight (R2 = 0.810) and the healthy breast volume (R2 = 0.880). The mean ideal implant volume was 278 ± 123 cc. The prediction model was developed using the healthy breast volume: Implant volume (cc) = healthy breast volume × 0.78 + 26 cc (R2 = 0.900). The prediction model for the ideal implant size using the 3D volume showed better prediction performance than that of using the mastectomy specimen weight (R2 = 0.900 vs 0.759, p < 0.001). Conclusions: The 3D volume of the healthy breast is a more reliable predictor than mastectomy specimen weight to estimate the ideal implant size. The estimation formula obtained in this study may assist in the selection of the ideal implant size in unilateral DTI breast reconstruction.

Finite Element Breast Simulation for Sonography Image Registration

In case of female breast cancer, a breast conserving excision is often necessary. For this purpose, information from multiple medical imaging techniques have to be combined. Sonography imaging is essential for dense breast tissue and the only medical imaging technique available during surgery. During sonography of the outer breast quadrants the woman is usually in contralateral posterior oblique position, being in supine orientation while holding her ipsilateral arm over the head. Thus, these images cannot be directly registered with MRI or mammography images because these imaging technologies are performed in other patient positions with hands on the side of the body. Thus, we present a novel Finite Element approach how to enable a sonography image registration by showing the first time how to transfer the supine position with the arm straight on side into a supine position with the ipsilateral arm over the head which can be used to include information from MRI or mammography images. This approach is shown and validated with 3D scanner breast surface data as proof of concept. When comparing the simulation result with a 3D surface scan in supine orientation with the arm over the head, a mean surface distance error of 1.57 mm is achieved.

Finite element analysis of long-term changes of the breast after augmentation mammoplasty: Implications for implant design

The development of breast implant technology continues to evolve over time, but changes in breast shape after implantation have not been fully elucidated. Thus, we performed computerized finite element analysis in order to better understand the trajectory of changes and stress variation after breast implantation. The finite element analysis of changes in breast shape involved two components: a static analysis of the position where the implant is inserted, and a dynamic analysis of the downward pressure applied in the direction of gravity during physical activity. Through this finite element analysis, in terms of extrinsic changes, it was found that the dimensions of the breast implant and the position of the top-point did not directly correspond to the trajectory of changes in the breast after implantation. In addition, in terms of internal changes, static and dynamic analysis showed that implants with a lower top-point led to an increased amount of stress applied to the lower thorax. The maximum stress values were 1.6 to 2 times larger in the dynamic analysis than in the static analysis. This finding has important implications for plastic surgeons who are concerned with long-term changes or side effects, such as bottoming-out, after anatomic implant placement.

A novel finite element model-based navigation system-supported workflow for breast tumor excision

In the case of female breast cancer, a breast-conserving excision is often desirable. This surgery is based on preoperatively gathered MRI, mammography, and sonography images. These images are recorded in multiple patient positions, e. g., 2D mammography images in standing position with a compressed breast and 3D MRI images in prone position. In contrast, the surgery happens in supine or beach chair position. Due to these different perspectives and the flexible, thus challenging, breast tissue, the excision puts high demands on the physician. Therefore, this publication presents a novel eight-step excision support workflow that can be used to include information captured preoperatively through medical imaging based on a finite element (FE) model. In addition, an indoor positioning system is integrated in the workflow in order to track surgical devices and the sonography transducer during surgery. The preoperative part of the navigation system-supported workflow is outlined exemplarily based on first experimental results including 3D scans of a patient in different patient positions and her MRI images. Graphical Abstract Finite Element model based navigation system supported workflow for breast tumor excision is based on eight steps and allows inclusion of information from medical images recorded in multiple patient positions.

New software and breast boundary landmarks to calculate breast volumes from 3D surface images

Background

A method to accurately calculate breast volumes helps achieving a better breast surgery outcome. 3D surface imaging potentially allows these calculations in a harmless, quick, and practicable way. The calculated volume from a 3D surface image is dependent on the determined breast boundary and the method of chest wall simulation by software. Currently, there is no consensus on a robust set of breast boundary landmarks and validation studies on breast volume calculation software are scarce. The purposes of this study were to determine the robustness of newly introduced breast boundary landmarks and introduce and validate a new method to simulate a chest wall.

Methods

Sixteen subjects who underwent a unilateral simple mastectomy were included. In addition to the natural skin fold of the breast, the sternomanubrial joint, the transition of the pectoral muscle curve into the breast curvature, and the midaxillary line were used as landmarks to indicate the breast boundary. The intra- and interrater variability of these landmarks was tested. Furthermore, new chest wall simulation software was validated on the breastless chest side of the subjects.

Results

The intra- and interrater variability of the three breast boundary markers was small (mean 3.5–6.7 mm), and no significant difference was found between the intra- and interrater variability (p = 0.08, p = 0.06, and p = 0.10). The mean volume error of the most accurately simulated chest wall was 4.6 ± 37 ml.

Conclusion

The newly introduced landmarks showed to be robust and our new chest wall simulation algorithm showed accurate results.

Level of Evidence: Level IV, diagnostic study.

Applications and limitations of using patient-specific 3D printed molds in autologous breast reconstruction

Background

Over the last years, several techniques have been proposed to improve the outcome of autologous breast reconstruction procedures. One of these innovations describes patient-specific, three-dimensional (3D) printed breast molds for intraoperative use based on 3D stereophotogrammetry. In this article, we want to share our preliminary experiences with producing such templates, its clinical possibilities and limitations in practice.

Methods

Patient-specific templates were designed based on 3D stereophotogrammetry images. The 3D template was fabricated using a 3D printer. During breast reconstruction, the autologous flap was placed inside the printed template to aid the surgeon in determining the shape and volume of the autologous flap creating the desired breast dimensions. Patients were 3D-photographed 6 to 9 months post-operatively.

Results

Three patients with unilateral breast reconstructions showed a width difference of 0.5 cm and mean volume difference of 211 ml between the reconstructed and contralateral breasts. In the three bilateral reconstructed patients, a mean difference in breast width and volume of respectively 0.5 cm and 16 ml was found.

Conclusions

Patient-specific breast templates are inexpensive and relatively easy to design, while being practical and convenient to obtain insight in the dimensions of the desired breast during reconstruction, according to the operating surgeons. Patient selection is however critical, as patients must have sufficient donor volume and/or satisfying breast shape to be able to use the template to its full potential.

Level of evidence: Level IV, therapeutic study.

Weighted regularized statistical shape space projection for breast 3D model reconstruction

The use of 3D imaging has increased as a practical and useful tool for plastic and aesthetic surgery planning. Specifically, the possibility of representing the patient breast anatomy in a 3D shape and simulate aesthetic or plastic procedures is a great tool for communication between surgeon and patient during surgery planning. For the purpose of obtaining the specific 3D model of the breast of a patient, model-based reconstruction methods can be used. In particular, 3D morphable models (3DMM) are a robust and widely used method to perform 3D reconstruction. However, if additional prior information (i.e., known landmarks) is combined with the 3DMM statistical model, shape constraints can be imposed to improve the 3DMM fitting accuracy. In this paper, we present a framework to fit a 3DMM of the breast to two possible inputs: 2D photos and 3D point clouds (scans). Our method consists in a Weighted Regularized (WR) projection into the shape space. The contribution of each point in the 3DMM shape is weighted allowing to assign more relevance to those points that we want to impose as constraints. Our method is applied at multiple stages of the 3D reconstruction process. Firstly, it can be used to obtain a 3DMM initialization from a sparse set of 3D points. Additionally, we embed our method in the 3DMM fitting process in which more reliable or already known 3D points or regions of points, can be weighted in order to preserve their shape information. The proposed method has been tested in two different input settings: scans and 2D pictures assessing both reconstruction frameworks with very positive results.

Breast tissue stiffness estimation for surgical guidance using gravity-induced excitation

Tissue stiffness interrogation is fundamental in breast cancer diagnosis and treatment. Furthermore, biomechanical models for predicting breast deformations have been created for several breast cancer applications. Within these applications, constitutive mechanical properties must be defined and the accuracy of this estimation directly impacts the overall performance of the model. In this study, we present an image-derived computational framework to obtain quantitative, patient specific stiffness properties for application in image-guided breast cancer surgery and interventions. The method uses two MR acquisitions of the breast in different supine gravity-loaded configurations to fit mechanical properties to a biomechanical breast model. A reproducibility assessment of the method was performed in a test-retest study using healthy volunteers and was further characterized in simulation. In five human data sets, the within subject coefficient of variation ranged from 10.7% to 27% and the intraclass correlation coefficient ranged from 0.91-0.944 for assessment of fibroglandular and adipose tissue stiffness. In simulation, fibroglandular content and deformation magnitude were shown to have significant effects on the shape and convexity of the objective function defined by image similarity. These observations provide an important step forward in characterizing the use of nonrigid image registration methodologies in conjunction with biomechanical models to estimate tissue stiffness. In addition, the results suggest that stiffness estimation methods using gravity-induced excitation can reliably and feasibly be implemented in breast cancer surgery/intervention workflows.

The Kinect Recording System for objective three- and four-dimensional breast assessment with image overlays

INTRODUCTION

We investigated the application of the validated portable Kinect camera for three- and four-dimensional breast assessment in female life models.

METHOD

Breast images from six life models were captured using the Kinect camera. Capture was conducted with taking three different arm positions while standing upright: with the arms straight down, straight up to the side at 90° and straight all the way up. Images of the volunteers were superimposed on each other. Digital linear distances between sternal notch and nipple-areola complexes were obtained and compared. The views of plastic and breast surgeons to arm positions were questioned. An example for clinical application was provided.

RESULTS

Successful capture of images of the female life breast models was achieved. Digital breast measurements at the three different arm positions revealed considerable variation in linear distances measured on the images obtained with the Kinect camera. The dynamic of breast movements could be demonstrated by image overlay and the first ever four-dimensional breast assessment was demonstrated. Fourteen plastic and breast surgeons were found to have nine different opinions regarding their favoured arm positions for breast capture. Even though precision of image sharpness still needs improvement, the images were satisfactory for clinical patient use. The Kinect data were shown to be applicable to surgery planning by designing a planar flap from the 3D mesh.

CONCLUSION

The portable and low-cost Kinect camera proved to be easy to use for the first application in life models for three- and four-dimensional breast assessment.

Multi-view stereophotogrammetry for post-mastectomy breast reconstruction

A multi-view three-dimensional stereophotogrammetry system was developed to capture 3D shape of breasts for breast cancer patients. The patients had received immediate unilateral breast reconstruction after mastectomy by the extended latissimus dorsi flap and without contralateral surgery. In order to capture the whole breast shape including the inframammary fold, the patients were introduced to the imaging room and leaned over the imaging rig to open up the inframammary fold and to expose the entire area of each breast. The imaging system consisted of eight high-resolution ([Formula: see text] pixels) digital cameras and four flash units. The cameras were arranged in four stereo pairs from four different view angles to cover the whole surface of the breasts. The system calibration was carried out ahead of every capture session, and the stereo images were matched to generate four range images to be integrated using an elastic model proposed. A watertight breast mesh model was reconstructed to measure the volume of the breast captured. The accuracy of using the developed multi-view stereophotogrammetry system for breast volume measurement was 11.12cc with SEM 7.74cc, comparing to the measurements of the water displacement method. It was concluded that the 3D stereophotogrammetry image system developed was more reliable than the method of water displacement.

Volume Preserved Mass-Spring Model with Novel Constraints for Soft Tissue Deformation

An interactive surgical simulation system needs to meet three main requirements, speed, accuracy, and stability. In this paper, we present a stable and accurate method for animating mass-spring systems in real time. An integration scheme derived from explicit integration is used to obtain interactive realistic animation for a multiobject environment. We explore a predictor-corrector approach by correcting the estimation of the explicit integration in a poststep process. We introduce novel constraints on positions into the mass-spring model (MSM) to model the nonlinearity and preserve volume for the realistic simulation of the incompressibility. We verify the proposed MSM by comparing its deformations with the reference deformations of the nonlinear finite-element method. Moreover, experiments on porcine organs are designed for the evaluation of the multiobject deformation. Using a pair of freshly harvested porcine liver and gallbladder, the real organ deformations are acquired by computed tomography and used as the reference ground truth. Compared to the porcine model, our model achieves a 1.502 mm mean absolute error measured at landmark locations for cases with small deformation (the largest deformation is 49.109 mm) and a 3.639 mm mean absolute error for cases with large deformation (the largest deformation is 83.137 mm). The changes of volume for the two deformations are limited to 0.030% and 0.057%, respectively. Finally, an implementation in a virtual reality environment for laparoscopic cholecystectomy demonstrates that our model is capable to simulate large deformation and preserve volume in real-time calculations.