Stefan Raith

Objective breast symmetry evaluation using 3-D surface imaging☆

This study develops an objective breast symmetry evaluation using 3-D surface imaging (Konica-Minolta V910(®) scanner) by superimposing the mirrored left breast over the right and objectively determining the mean 3-D contour difference between the 2 breast surfaces. 3 observers analyzed the evaluation protocol precision using 2 dummy models (n = 60), 10 test subjects (n = 300), clinically tested it on 30 patients (n = 900) and compared it to established 2-D measurements on 23 breast reconstructive patients using the BCCT.core software (n = 690). Mean 3-D evaluation precision, expressed as the coefficient of variation (VC), was 3.54 ± 0.18 for all human subjects without significant intra- and inter-observer differences (p > 0.05). The 3-D breast symmetry evaluation is observer independent, significantly more precise (p < 0.001) than the BCCT.core software (VC = 6.92 ± 0.88) and may play a part in an objective surgical outcome analysis after incorporation into clinical practice.

Comparative Assessment of 3D Surface Scanning Systems in Breast Plastic and Reconstructive Surgery

In this work, we compared accuracy, repeatability, and usability in breast surface imaging of 2 commercial surface scanning systems and a hand-held laser surface scanner prototype coupled with a patient’s motion acquisition and compensation methodology. The accuracy of the scanners was assessed on an anthropomorphic phantom, and to evaluate the usability of the scanners on humans, thorax surface images of 3 volunteers were acquired. Both the intrascanner repeatability and the interscanner comparative accuracy were assessed. The results showed surface-to-surface distance errors inferior to 1 mm and to 2 mm, respectively, for the 2 commercial scanners and for the prototypical one. Moreover, comparable performances of the 3 scanners were found when used for acquiring the breast surface. On the whole, this study demonstrated that handheld laser surface scanners coupled with subject motion compensation methods lend themselves as competitive technologies for human body surface modeling.

A computer-assisted diagnostic and treatment concept to increase accuracy and safety in the extracranial correction of cranial vault asymmetries.

PURPOSE Proteus syndrome is described as a progressive, asymmetric, disproportional overgrowth of various parts of the body. The theory of somatic mosaicism is widely accepted to be the cause of this disease. Affected patients present very heterogeneous symptoms, but in about 30% craniofacial deformities are the leading clinical features. Because no causal therapy exists, treatment options are limited to surgical improvement of functional constraints. MATERIALS AND METHODS A computer-assisted method was used to increase the accuracy and safety of bone removal in the extracranial correction of cranial vault asymmetries. Descriptions of the diagnosis, preoperative planning, and intraoperative management of craniofacial dysmorphia caused by Proteus syndrome in a 6-year-old boy are presented. After computed tomography-based generation of a virtual 3-dimensional (3D) model of the patient and a haptic stereolithographic model to display the special pathology, flow-sensitized 4-dimensional magnetic resonance imaging was performed to clarify the properties of vascular formation inside the hyperostosis. To transfer the mathematically optimized preoperative planning of a new skull shape to the patient, a surgical guide was fabricated by rapid manufacturing. Intraoperative 3D real-time navigation was installed as an additional visualization and security feature. RESULTS The surgery could be performed safely and quickly. Postoperative imaging showed that the surgical plan was realized with high accuracy. CONCLUSION This newly developed and validated method can be successfully implemented in the operating room environment.

High-fidelity human patient simulators compared with human actors in an unannounced mass-casualty exercise.

High-fidelity simulators (HFSs) have been shown to prompt critical actions at a level equal to that of trained human actors (HAs) and increase perceived realism in intrahospital mass-casualty incident (MCI) exercises. For unannounced prehospital MCI exercises, however, no data are available about the feasibility of incorporating HFSs. This case report describes the integration of HFSs in such an unannounced prehospital MCI drill with HAs and provides data about the differences concerning triage, treatment, and transport of HFSs and HAs with identical injury patterns. For this purpose, 75 actors and four high-fidelity simulators were subdivided into nine groups defined by a specific injury pattern. Four HFSs and six HAs comprised a group suffering from traumatic brain injury and blunt abdominal trauma. Triage results, times for transport, and number of diagnostic and therapeutic tasks were recorded. Means were compared by t test or one-way ANOVA. Triage times and results did not differ between actors and simulators. The number of diagnostic (1.25, SD = 0.5 in simulators vs 3.5, SD = 1.05 in HAs; P = .010) and therapeutic tasks (2.0, SD = 1.6 in simulators vs 4.8, SD = 0.4 in HAs; P = .019) were significantly lower in simulators. Due to difficulties in treating and evacuating the casualties from the site of the accident in a timely manner, all simulators died. Possible causal factors and strategies are discussed, with the aim of increasing the utility of simulators in emergency medicine training.

Preoperative flap volume prediction in autologous abdominal breast reconstruction.

Preoperative Flap Volume Prediction in Autologous Abdominal Breast Reconstruction Sir: W read with great interest the Viewpoint entitled “A Method of Preoperatively Assessing the Volume of Abdominal Tissue Available for an Autologous Breast Reconstruction” published recently in Plastic and Reconstructive Surgery and would like to congratulate the authors on their interesting work.1 We agree that preoperative flap volume estimation will support surgical planning for adequate breast volume replacement and facilitate the intraoperative flap trimming and final breast shaping, resulting in reduced operative time, and may be helpful in preoperative patient consultation. Current approaches for flap volume/weight determination include intraoperative water displacement or ordinary weight measurements, preoperative ultrasound, and three-dimensional computed tomographic angiography–based calculations.2,3 In particular, computed tomographic angiography has proven clinical utility in the accurate vascular perforator supply determination and preoperative preparation in abdominal free flap breast reconstruction. Furthermore, the diagnostic application of computed tomographic angiography can be easily expanded to flap volume assessment before surgery with potential clinical benefit.3 According to the surgeon’s preoperative flap markings, a virtual three-dimensional model of the abdominal flap can be reconstructed based on preoperative computed tomographic angiography with the resulting flap dimension (in centimeters), surface (in square centimeters), and volume (in cubic centimeters) (Fig. 1). As harvested flap dimensions are subject to intraoperative soft-tissue changes,3 three-dimensional surface scans of the harvested flap were obtained for comparison of the intraoperative flap geometry and volume (three-dimensional scan volume, 534 cc) to the preoperative three-dimensional computed tomographic estimations (three-dimensional computed tomographic scan volume, 549 cc) and to the actual measured flap weight (flap weight, 550 g). Flap dimensions changed significantly with reduction in the horizontal plane and flap enlargement in the vertical plane combined with a flap thickness increase (Fig. 1). The skin surface (in square centimeters) showed a valuable decrease by 15 percent. Although flap geometry has changed, the predicted preoperative (three-dimensional computed tomography) and intraoperative (three-dimensional scan) flap volumes showed no relative differences compared with

Finite Element Simulation of the Deformation of the Female Breast Based on MRI Data and 3-D Surface Scanning: An In-Vivo Method to Assess Biomechanical Material Parameter Sets

Introduction: Biomechanical studies of the mechanical deformations of the human body often use numerical simulations, such as the finite element analysis (FEA). Especially the shape changes of the female breast under varying load conditions are a current area of interest, both in the computational engineering science and the medical sector. During radiological diagnostics the breast is exposed to different mechanical loading conditions than later at the stage of the operation planning and in the operation room. For better operation planning, a prediction of these mechanical deformations on the computer is desired. However, to generate realistic results that consider the physics of biological materials, it is essential to have a sufficient understanding of the theoretical constitutive models and the material parameters that describe the soft tissue of the breast. Although numerous studies have been performed to acquire material parameters, yet no consensus of reliable parameter sets could be generated yet. We think that three-dimensional body scanning can have a decisive role for the determination of soft tissue parameters of the breast.

Breast Reconstruction Using Patients Own Tissue Based on CT Angiography and 3-D Surface Scanning

Breast reconstruction is mainly required for women who have had a breast to be removed (mastectomy) due to breast cancer. The aim of this surgery is to rebuild the natural shape of the breast mound in order to regain symmetry. The current state of the art in autologous breast reconstruction surgery is the transplantation of the patients’ own soft tissue. One of the most popular methods is using soft tissue flaps from the abdominal region such as the deep inferior epigastric artery perforator flap (DIEP). Even though this technique has proven its applicability in reconstructive surgery with enough soft tissue supply at the donor region and a low rate of flap morbidity, one difficulty encountered during the operation planning is the decision of the size and the shape of the transplanted flap. In order to overcome this difficulty, and to provide planning aids for the surgeons, modern imaging technologies such as 3-D surface scanning and 3-D computed tomography angiography (3-D CTA) for volumetric imaging are used. In this study we introduce a computational approach to optimize the preoperative planning in autologous abdominal breast reconstruction using modern 3-D imaging techniques.

Computer assisted evaluation of plate osteosynthesis of diaphyseal femur fracture considering interfragmentary movement: a finite element study.

Abstract A semi-automated workflow for evaluation of diaphyseal fracture treatment of the femur has been developed and implemented. The aim was to investigate the influence of locking compression plating with diverse fracture-specific screw configurations on interfragmentary movements (IFMs) with the use of finite element (FE) analysis. Computed tomography (CT) data of a 22-year-old non-osteoporotic female were used for patient specific modeling of the inhomogeneous material properties of bone. Hounsfield units (HU) were exported and assigned to elements of a FE mesh and converted to mechanical properties such as the Young’s modulus followed by a linear FE analysis performed in a semi-automated fashion. IFM on the near and far cortex was evaluated. A positive correlation between bridging length and IFM was observed. Optimal healing conditions with IFMs between 0.5 mm and 1 mm were found in a constellation with a medium bridging length of 80 mm with three unoccupied screw holes around the fracture gap. Usage of monocortical screws instead of bicortical ones had negligible influence on the evaluated parameters when modeling non-osteoporotic bone. Minimal user input, automation of the procedure and an efficient computation time ensured quick delivery of results which will be essential in a future clinical application.

Computer Assisted Optimization of Prosthetic Socket Design for the Lower Limb Amputees Using 3-D Scan

Introduction: Customary prosthetic socket construction and fabrication process do not take patient specific parameters into account, instead they are based on subjective estimations, competence and capabilities of the orthopedic technician. Therefore a high rate of inappropriate prosthetic supplies is caused to the disadvantage of the amputation patient who suffers from wounds due to excessive pressure. A development of objective planning systems is required, in order to gain higher quality in the prosthetic socket construction. The central aim of the presented work was to improve the currently empirical process of prosthesis design in orthopedic technology with the aid of 3-D scan of the amputation stump, modern imaging techniques (MRI) and computer technology (FEA). Method: Regarding a 3-D scan protocol the amputation stump of 10 patients were scanned in upright position using a 3-D linear laser scanner. Furthermore magnet resonance imaging (MRI) was performed in lying supine position, which produced non-negligible deformation in the soft tissue of the stump. MRI datasets were segmented into different compartments representing fat, muscle and bone using a special software workflow. The segmented geometries were fitted in the surface geometry of the upright 3-D scan. Therefore a simplified FE model was built in consideration of stiffness of soft tissue and bone. The calculated models reproduced the inner anatomical structure of the stump. The described method has been validated on a patient where both upright and regular supine MR image data were accessible in addition to 3-D surface scans with the aid of software calculating the 3-D compare (mean standard deviation in mm) of the 3-D models. The results of the deformation calculations of the patients were validated in FEA simulations and gait analysis. Results: Using 3-D compare of the obvious deformed MRI model in lying position in comparison to the upright MRI model the mean standard deviation (SD) was 13.5 mm. The 3-D comparison of the reversely calculated MRI model in comparison to the upright MRI model showed a mean standard deviation of 5.8 mm (improvement factor 2.34). The mean standard deviation of 5.8 mm did not exceed the mean edge length of the finite elements, thus the results are sufficiently accurate for the following simulations performed by FEA software. Conclusion: Validation results show a considerable improvement from the deformed MRI model in comparison to the reversely calculated MRI model, which is important for a realistic and physically based computer assisted design of the prosthetic socket. Based on patient-specific 3-D model, 3-D visualization, quantification and simulation of the individual biomechanical tissue changes in the amputation stump during the interaction with the prosthetic socket can be evaluated using finite element analysis (FEA).

Breast Volume Measurements Using 3-D Surface Imaging: A Standardized Validation of the Introduced Method and a Comparison to Classical Approaches

Introduction: Precise and objective calculation of breast volume can be helpful to evaluate the aesthetic result of breast surgery, but traditional methods are unsatisfactory. Three-dimensional (3-D) scanning of the body surface allows reproducible and objective assessment of the complex breast region but requires further investigation before clinical application. The main goal of this study was to investigate the precision and accuracy of breast volume measurement using 3-D body scanning and to compare breast volume calculation with 3-D scanning and three classic methods, focusing on relative advantages, disadvantages, and reproducibility. Materials and Methods: Five independent observers standardized the 3-D scanning method using two dummy models (n = 200) and examined its applicability with 6 test subjects and 10 clinical patients (n = 2220). Breast volume measurements obtained with the 3-D scanner technology were compared with reference measurements obtained from test subjects through MRI, thermoplastic castings and anthropomorphic measurements. Results: The mean deviation of the breast volume measurements of one test subject by all observers, expressed as percentage of volume, was 2.86 +/0.98, significantly higher than the deviation for the dummy models, 1.65 +/0.42 (p < 0.001). Inter-observer differences in measurement precision were not statistically significant. The mean breast volumes obtained by MRI (441.42 +/137.05 cc) and 3-D scanning (452.51 +/141.88 cc) significantly correlated (r = 0.995, p < 0.001). MRI showed the highest measurement precision, with a mean deviation (expressed as percent of mean breast volume) of 1.56 +/0.52 compared to 2.27 +/0.99 for the 3D scanner, 7.97 +/3.53 for thermoplastic castings, and 6.26 +/1.56 for the anthropomorphic measurements. Breast volume calculations using MRI showed the best agreement to 3-D scanning measurement (r = 0.990), followed by anthropomorphic measurement (r = 0.947), and thermoplastic castings (r = 0.727). Conclusion: Breast volume measurement using 3-D surface imaging represents a sufficiently precise and accurate method to guarantee objective and exact recording. Compared to three classical methods for breast volume calculation, 3D scanning allows precise measurement, better spatial interpretation of the anatomical area to be operated on (due to lack of chest deformation), non-invasiveness, and good patient tolerance.