Evaluation of breast skin and tissue stiffness using a non-invasive aspiration device and impact of clinical predictors.

A personalized 3D breast model could present a real benefit for preoperative discussion with patients, surgical planning, and guidance. Breast tissue biomechanical properties have been poorly studied in vivo, although they are important for breast deformation simulation. The main objective of our study was to determine breast skin thickness and breast skin and adipose/fibroglandular tissue stiffness. The secondary objective was to assess clinical predictors of elasticity and thickness: age, smoking status, body mass index, contraception, pregnancies, breastfeeding, menopausal status, history of radiotherapy or breast surgery. Participants were included at the Montpellier University Breast Surgery Department from March to May 2022. Breast skin thickness was measured by ultrasonography, breast skin and adipose/fibroglandular tissue stiffnesses were determined with a VLASTIC non-invasive aspiration device at three different sites (breast segments I-III). Multivariable linear models were used to assess clinical predictors of elasticity and thickness. In this cohort of 196 women, the mean breast skin and adipose/fibroglandular tissue stiffness values were 39 and 3 kPa, respectively. The mean breast skin thickness was 1.83 mm. Only menopausal status was significantly correlated with breast skin thickness and adipose/fibroglandular tissue stiffness. The next step will be to implement these stiffness and thickness values in a biomechanical breast model and to evaluate its capacity to predict breast tissue deformations.

Dynamic three-dimensional virtual environment to improve learning of anatomical structures.

Increasing number of medical students and limited availability of cadavers have led to a reduction in anatomy teaching through human cadaveric dissection. These changes triggered the emergence of innovative teaching and learning strategies in order to maximize students learning of anatomy. An alternative approach to traditional dissection was presented in an effort to improve content delivery and student satisfaction. The objective of this study is to acquire three-dimensional (3D) anatomical data using structured-light surface scanning to create a dynamic four-dimensional (4D) dissection tool of four regions: neck, male inguinal and femoral areas, female perineum, and brachial plexus. At each dissection step, identified anatomical structures were scanned using a 3D surface scanner (Artec Spider™). Resulting 3D color meshes were overlaid to create a 4D (3D+time) environment. An educational interface was created for neck dissection. Its implementation in the visualization platform allowed 4D virtual dissection by navigating from surface to deep layers and vice versa. A group of 28 second-year medical students and 17 first-year surgery residents completed a satisfaction survey. A majority of medical students (96.4%) and 100% of surgery residents said that they would recommend this tool to their colleagues. According to surgery residents, the main elements of this virtual tool were the realistic high-quality of 3D acquisitions and possibility to focus on each anatomical structure. As for medical students, major elements were the interactivity and entertainment aspect, precision, and accuracy of anatomical structures. This approach proves that innovative solutions to anatomy education can be found to help to maintain critical content and student satisfaction in anatomy curriculum.

Feasibility of Cochlea High-frequency Ultrasound and Microcomputed Tomography Registration for Cochlear Computer-assisted Surgery: A Testbed.

INTRODUCTION: There remains no standard imaging method that allows computer-assisted surgery of the cochlea in real time. However, recent evidence suggests that high-frequency ultrasound (HFUS) could permit real-time visualization of cochlear architecture. Registration with an imaging modality that suffers neither attenuation nor conical deformation could reveal useful anatomical landmarks to surgeons. Our study aimed to address the feasibility of an automated three-dimensional (3D) HFUS/microCT registration, and to evaluate the identification of cochlear structures using 2D/3D HFUS and microCT. METHODS: MicroCT, and 2D/3D 40 MHz US in B-mode were performed on ex vivo guinea pig cochlea. An automatic rigid registration algorithm was applied to segmented 3D images. This automatic registration was then compared to a reference method using manual annotated landmarks placed by two senior otologists. Inter- and intrarater reliabilities were evaluated using intraclass correlation coefficient (ICC) and the mean registration error was calculated. RESULTS: 3D HFUS/microCT automatic registration was successful. Excellent levels of concordance were achieved with regards intra-rater reliability for both raters with micro-CT and US images (ICC ranging from 0.98 to 1, p < 0.001) and with regards inter-rater reliability (ICC ranging from 0.99 to 1, p < 0.001). The mean HFUS/microCT automated RE for both observers was 0.17 ±â€Š0.03 mm [0.10-0.25]. Identification of the basilar membrane, modiolus, scala tympani, and scala vestibuli was possible with 2D/3D HFUS and micro-CT. CONCLUSIONS: HFUS/microCT image registration is feasible. 2D/3D HFUS and microCT allow the visualization of cochlear structures. Many potential clinical applications are conceivable.

HFUS Imaging of the Cochlea: A Feasibility Study for Anatomical Identification by Registration with MicroCT.

Cochlear implantation consists in electrically stimulating the auditory nerve by inserting an electrode array inside the cochlea, a bony structure of the inner ear. In the absence of any visual feedback, the insertion results in many cases of damages of the internal structures. This paper presents a feasibility study on intraoperative imaging and identification of cochlear structures with high-frequency ultrasound (HFUS). 6 ex-vivo guinea pig cochleae were subjected to both US and microcomputed tomography (µCT) we respectively referred as intraoperative and preoperative modalities. For each sample, registration based on simulating US from the scanner was performed to allow a precise matching between the visible structures. According to two otologists, the procedure led to a target registration error of 0.32 mm ± 0.05. Thanks to referring to a better preoperative anatomical representation, we were able to intraoperatively identify the modiolus, both scalae vestibuli and tympani and deduce the location of the basilar membrane, all of which is of great interest for cochlear implantation. Our main objective is to extend this procedure to the human case and thus provide a new tool for inner ear surgery.

Geometric and mechanical evaluation of 3D-printing materials for skull base anatomical education and endoscopic surgery simulation - A first step to create reliable customized simulators.

INTRODUCTION: Endoscopic skull base surgery allows minimal invasive therapy through the nostrils to treat infectious or tumorous diseases. Surgical and anatomical education in this field is limited by the lack of validated training models in terms of geometric and mechanical accuracy. We choose to evaluate several consumer-grade materials to create a patient-specific 3D-printed skull base model for anatomical learning and surgical training. METHODS: Four 3D-printed consumer-grade materials were compared to human cadaver bone: calcium sulfate hemihydrate (named Multicolor), polyamide, resin and polycarbonate. We compared the geometric accuracy, forces required to break thin walls of materials and forces required during drilling. RESULTS: All materials had an acceptable global geometric accuracy (from 0.083mm to 0.203mm of global error). Local accuracy was better in polycarbonate (0.09mm) and polyamide (0.15mm) than in Multicolor (0.90mm) and resin (0.86mm). Resin and polyamide thin walls were not broken at 200N. Forces needed to break Multicolor thin walls were 1.6-3.5 times higher than in bone. For polycarbonate, forces applied were 1.6-2.5 times higher. Polycarbonate had a mode of fracture similar to the cadaver bone. Forces applied on materials during drilling followed a normal distribution except for the polyamide which was melted. Energy spent during drilling was respectively 1.6 and 2.6 times higher on bone than on PC and Multicolor. CONCLUSION: Polycarbonate is a good substitute of human cadaver bone for skull base surgery simulation. Thanks to short lead times and reasonable production costs, patient-specific 3D printed models can be used in clinical practice for pre-operative training, improving patient safety.

Cerebrospinal fluid volume does not have etiological role in the incidence of positional skull deformities.

BACKGROUND: Positional skull deformities (PSD) are becoming a daily health concern for craniofacial surgeons. Several reports have indicated that cerebrospinal fluid (CSF) space increases on computed tomography (CT) scans of infants suffering from PSD, suggesting a potential causal link. Here, we describe a semi-automatic method to estimate total brain and CSF volumes quantitatively. We tested the potential correlation between total CSF volume and the occurrence of PSD. METHODS: A single-center retrospective study was carried out using 79 CT scans of PSD and 60 CT scans of control subjects. The endocranium was segmented automatically using a three-dimensional deformable surface model, and the brain was segmented using a semi-automatic threshold-based method. Total CSF volume was estimated based on the difference between endocranial and brain volumes. RESULTS: Automatic segmentation of the endocranium was possible in 75 CT scans. Semi-automatic brain and CSF volume evaluations were performed in 40 CT scans of infants with PSD (18 = occipital plagiocephaly, 11 = fronto-occipital plagiocephaly, and 11 = posterior brachycephaly) and in six control CT scans. Endocranial and total CSF volumes were not significantly different between patients with PSD and controls. The occipital plagiocephaly group had an enlarged brain volume compared with that in patients in the other groups. CONCLUSIONS: Total CSF volume did not change in infants with PSD, and the results do not support a role for volume changes in CSF in the etiology of PSD. Macrocephaly in patients with occipital plagiocephaly may be a specific etiological factor compared with that in other PSDs.

Three-dimensional study of the skin/subcutaneous complex using in vivo whole body 3T MRI: review of the literature and confirmation of a generic pattern of organization.

PURPOSE: With a view to developing a tool for predicting the behavior of soft tissues during plastic surgery procedures, we looked for the existence of homologies in the overall pattern of organization of the skin/subcutaneous tissue complex between various body parts, using high-resolution in vivo imaging methods and data available in the literature. METHODS: 3T MRI scanning sequences were performed using appropriate radiofrequency coils on the face, thorax, breast, abdomen and lower extremity of six healthy volunteers. The radiological findings were segmented and converted into volumetric data. RESULTS: The superficial and deep adipose tissue was found to be clearly separated by an intermediate layer called stratum membranosum or superficial fascia. This continuous layer covered all the anatomical parts of the body examined. It was found to have several components in the trunk and limbs and to form a continuous layer with the superficial muscular aponeurotic system in the face. A retaining connective network consisting of superficial and deep retinacula cutis detected in all the regions investigated sometimes formed more densely packed structures playing the role of skin ligaments. CONCLUSION: The results of a 3T MRI study on subcutaneous tissue showed the existence of a common pattern of organization of the skin-subcutaneous tissue complex in the various parts of the body studied. This general model is subject to quantitative variations and tissue differentiation processes promoting the sliding or contractility of the supporting tissue. Three-dimensional reconstructions were obtained by post-processing the MRI images and will be used to perform pre-surgical simulations by settings a generic model that can be adapted to the different localization of the human body in a procedural way.

Effects of growth on maxillary distraction osteogenesis in cleft lip and palate.

PURPOSE: The objective was to analyze the effects of growth on the long-term result of maxillary distraction osteogenesis (DO) in cleft lip and palate (CLP). PATIENTS AND METHODS: Retrospective study of 24 CLP cases with long-term follow-up operated for maxillary DO using the Polley and Figueroa technique: 10 patients were distracted during growth, while 14 patients were operated after their growth spurt. Preoperative (T0), 6-12 months postoperative (T1), and ≥4 years postoperative (T2) cephalometric radiographs were evaluated. A classical cephalometric analysis was used to assess the treatment stability, and a Procrustes superimposition method was performed to assess local changes in the maxilla and the mandible. RESULTS: At T0, the mean age was of 11.9 ± 1.4 years for growing patient, and 17.9 ± 3.5 years for patient treated after their growth spurt (P < 0.001). Between T0 and T1, a greater increase of the SNA was shown in growing patients (P = 0.036), but the relapse was more important between T1 and T2, with a significant decrease of the SNA (P = 0.002) and ANB (P = 0.032) compared to the patients treated after their growth spurt. Although not significant, growing patients showed greater rotations of their palatal plane and mandibular plane. CONCLUSIONS: Maxillary DO in CLP does not correct the growth deficit inherent to the pathology. Overcorrection of at least 20% is advised during growth.

Three-dimensional analysis of the intrinsic anatomy of the metatarsal bones.

Knowledge of the anatomy of the forefoot is important for understanding its mechanical pathology and developing specific surgical procedures. The aim of this study was to quantify 3-dimensional morphological parameters, which were proposed for the characterization of the metatarsal intrinsic anatomy. Thirty-five metatarsal bones prepared from 7 cadaver specimens were analyzed according to a new 3-dimensional computer-aided (CA) methodology. Manual and CA measurement techniques were compared. The reality of an intrinsic axial torsion of the metatarsals was underlined with mean values between 3.2 degrees and 57.7 degrees. Using the CA method, the reliability was excellent (intraclass correlation coefficient, 0.98) and significantly better than the manual method (P < .1E-12). With specific consideration of the second metatarsal intrinsic morphology, we emphasized its mechanical function. These results reflect the possibilities of CA systems. These data, which were carried out on specific anatomical characteristics of the metatarsal bones, can improve the metatarsalgia surgical procedures.

Automatic detection and segmentation of evolving processes in 3D medical images: Application to multiple sclerosis.

The study of temporal series of medical images can be helpful for physicians to perform pertinent diagnoses and to help them in the follow-up of a patient: in some diseases, lesions, tumors or anatomical structures vary over time in size, position, composition, etc., either because of a natural pathological process or under the effect of a drug or a therapy. It is a laborious and subjective task to visually and manually analyze such images. Thus the objective of this work was to automatically detect regions with apparent local volume variation with a vector field operator applied to the local displacement field obtained after a non-rigid registration between two successive temporal images. On the other hand, quantitative measurements, such as the volume variation of lesions or segmentation of evolving lesions, are important. By studying the information of apparent shrinking areas in the direct and reverse displacement fields between images, we are able to segment evolving lesions. Then we propose a method to segment lesions in a whole temporal series of images. In this article we apply this approach to automatically detect and segment multiple sclerosis lesions that evolve in time series of MRI scans of the brain. At this stage, we have only applied the approach to a few experimental cases to demonstrate its potential. A clinical validation remains to be done, which will require important additional work.