Validation of 3D spino-pelvic muscle reconstructions based on dedicated MRI sequences for fat-water quantification

 Objectives: To evaluate a protocol, including MRI acquisition with dedicated sequences for fat-water quantification and semi-automatic segmentation, for 3D geometry measurement and fat infiltration of key muscles of the spino-pelvic complex. Materials and Methods: MRI Protocol: Two axial acquisitions from the thoraco-lumbar region to the patella were obtained: one T1 weighted and one based on the Dixon method, permitted to evaluate the proportion of fat inside each muscle. Muscle Reconstruction: With Muscl’X software, 3D reconstructions of 18 muscles or groups of muscles were obtained identifying their contours on a limited number of axial images (DPSO Method); 3D references were obtained only on T1 acquisitions identifying the contour of the muscles on all axial images. Evaluation: For two volunteers, three operators completed reconstructions three times across three sessions. Each reconstruction was projected on the reference to calculate the ‘point to surface’ error. Mean and maximal axial section, muscle volume, and muscle length calculated from the reconstructions were compared to reference values, and intra- and inter-operator variability for those parameters were evaluated. Results: 2xRMS ‘point to surface’ error was below 3 mm, on average. The agreement between the two methods was variable between muscles [-4.50; 8.00 %] for the mean axial section, the length and the volume. Intra- and inter-operator variability were less than 5% and comparison of variability for the Fat and T1 reconstructions did not reveal any significant differences. Discussion: Excellent inter- and intra-operator reliability was demonstrated for 3D muscular reconstruction using the DPSO method and Dixon images that allowed generation of patient-specific musculoskeletal models. Fondation Paristech, ISS

Distribution and variability study of the femur cortical thickness from computer tomography

In the context of patient-specific 3D bone reconstruction, enhancing the surface with cortical thickness (COT) opens a large field of applications for research and medicine. This functionality calls for database analysis for better knowledge of COT. Our study provides a new approach to reconstruct 3D internal and external cortical surfaces from computer tomography (CT) scans and analyses COT distribution and variability on a set of asymptomatic femurs. The reconstruction method relies on a short (∼5 min) initialisation phase based on 3D reconstruction from biplanar CT-based virtual X-rays and an automatic optimisation phase based on intensity-based cortical structure detection in the CT volume, the COT being the distance between internal and external cortical surfaces. Surfaces and COT show root mean square reconstruction errors below 1 and 1.3 mm. Descriptions of the COT distributions by anatomical regions are provided and principal component analysis has been applied. The first mode, 16–50% of the variance, corresponds to the variation of the mean COT around its averaged shape; the second mode, 9–28%, corresponds to a fine variation of its shape. A femur COT model can, therefore, be described as the averaged COT distribution in which the first parameter adjusts its mean value and a second parameter adjusts its shape

CT-based semi-automatic quantification of vertebral fracture restoration

Minimally invasive surgeries aiming to restore fractured vertebral body are increasing; therefore, our goals were to create a 3D vertebra reconstruction process and design clinical indices to assess the vertebral restoration in terms of heights, angles and volumes. Based on computed tomography (CT)-scan of the vertebral spine, a 3D reconstruction method as well as relevant clinical indices were developed. First, a vertebra initial solution requiring 5 min of manual adjustments is built. Then an image processing algorithm places this solution in the CT-scan images volume to adjust the model's nodes. On the vertebral body's anterior and posterior parts, nine robust heights, volume and endplate angle measurement methods were developed. These parameters were evaluated by reproducibility and accuracy studies. The vertebral body reconstruction accuracy was 1.0 mm; heights and volume accuracy were, respectively, 1.2 and 179 mm3. In conclusion, a 3D vertebra reconstruction process requiring little user time was proposed as well as 3D clinical indices assessing fractured and restored vertebra

Skeletal muscle segmentation from MRI dataset using a model-based approach

Magnetic resonance imaging (MRI) and computed tomography scans are used to assess muscle volume, but the manual segmentation, slice by slice, is long and tedious. We proposed an improvement in the deformation of a parametric-specific object method using image processing. The 3D subject-specific geometry was reconstructed based on a few selected number of MRI slices by fast rough contouring using polygons. These polygons were matched to the muscle shape by an optimisation method using an original cost function. Then, parametric-specific object was constructed and deformed. The shape was improved using a loop and the cost function in all MRI slices. The 11 main muscles of the thigh were considered, and the time required to get the shape of all muscles was 21 min, with a volume error inferior to 5% and a point-surface distance error (2RMS) inferior to 5 mm. This method provides a good compromise between segmentation time and an accurate representation of the muscles shape

Development of an Open Source Framework to position and personalize Human Body Models

International audienceThe current manuscript reports on the development status of a software framework to scale (personalize) and position Human Body Models used in safety applications, i.e. the PIPER framework. The framework is both model and code agnostic and it was successfully used with Thums, GHBMC and the new PIPER scalable child model. Various transformation methods to scale or positioning were implemented in an interactive application. The software was released under the Open Source General Public License (GPL) version 2

Subject-specific musculoskeletal model of the lower limb in a lying and standing position

Accurate estimation of joint loads implies using subject-specific musculoskeletal models. Moreover, as the lines of action of the muscles are dictated by the soft tissues, which are in turn influenced by gravitational forces, we developed a method to build subject-specific models of the lower limb in a functional standing position. Bones and skin envelope were obtained in a standing position, whereas muscles and a set of bony landmarks were obtained from conventional magnetic resonance images in a lying position. These muscles were merged with the subject-specific skeletal model using a nonlinear transformation, taking into account soft tissue movements and gravitational effects. Seven asymptomatic lower limbs were modelled using this method, and results showed realistic deformations. Comparing the subject-specific skeletal model to a scaled reference model rendered differences in terms of muscle length up to 4% and in terms of moment arm for adductor muscles up to 30%. These preliminary findings enlightened the importance of subject-specific modelling in a functional position

Carta de una amiga á Maria Victoria Enriqueta, duquesa de Aota, reina electa de España

International audienceSpecifications of a Software Framework to Position and Personalise Human Body Model

Coeval extensional shearing and lateral underflow during Late Cretaceous core complex development in the Niğde Massif, Central Anatolia, Turkey

27 p.International audienceThe Nig¢de Massif, at the southern tip of the Central Anatolian Crystalline Complex, consists of two structural units. Foliations in the lower unit define a dome cored by migmatites. The contact between the two units bears all the elements of a ductile to brittle extensional detachment. Hence the Nig¢de Massif represents an extensional metamorphic core complex. Top-to-NE/ENE shearing at higher levels of the lower unit relates to displacement along the detachment. Deeper levels of the lower unit display hightemperature top-to-SSW ductile shearing. The two shearing deformations show a difference in the mean trend of stretching lineations of up to 58. New 40Ar/39Ar ages combined with previously published data enable us to infer that the two shears were contemporaneous. In our favored interpretation, oblique shearing in the core of the dome reflects lateral underflow, i.e., horizontal flowing of the lower crust in a direction highly oblique to the direction of extension. As a result of the interaction between lateral underflow and downdip shearing along the overlying detachment, distinct structural domains are expected to exist within the migmatitic part of the core complex, with observed counterparts in the Nig¢de dome. Lateral underflow may reflect ''inward'' flow on the scale of the core complex. Regional-scale channel flow is an alternative that would better account for the record of non-coaxial deformation in the core of the dome. More generally, we suspect that the development of lateral underflow in a metamorphic core complex more likely reflects regional channel flow, rather than local inward flow

D3.8 Final version of the personalization and positioning software tool with documentation. PIPER EU Project

The aim of this report is to provide an overview of the final version of the PIPER framework and application. The software, along with its documentation, and not the report, constitutes the main part of the deliverable. The software and documentation were already distributed at the Final Workshop and online (under the Open Source license GPLv2 or later for the software, and the GNU FDL 1.3 license for the documentation). The documentation includes detailed descriptions of the framework principles, user interface, metadata, along with the modules and their parameters. It also includes application scenarios (called workflows). Information about the use of the modules is complemented by Tutorials that were developed as part of WP1 (online on the wiki) and explanatory videos were developed as part of WP4 (videos of the final workshop, now available on YouTube). The headers in the source code files (also available online) list the main contributors to the software. The report will therefore not provide details about information that is already available elsewhere but will only provide a very brief summary of the functionalities available. Some of the descriptions are excerpts of the manual