Analysis of existing methods for 3D modelling of femurs starting from two orthogonal images and development of a script for a commercial software package

Extra-Articular Distal Humerus Plate 3D Model Creation by Using the Method of Anatomical Features

Proper fixation techniques are crucial in orthopedic surgery for the treatment of various medical conditions. Fractures of the distal humerus can occur due to either high-energy trauma with skin rupture or low-energy trauma in osteoporotic bone. The recommended surgical approach for treating these extra-articular distal humerus fractures involves performing an open reduction and internal fixation procedure using plate implants. This surgical intervention plays a crucial role in enhancing patient recovery and minimizing soft tissue complications. Dynamic Compression Plates (DCPs) and Locking Compression Plates (LCPs) are commonly used for bone fixation, with LCP extra-articular distal humerus plates being the preferred choice for extra-articular fractures. These fixation systems have anatomically shaped designs that provide angular stability to the bone. However, depending on the shape and position of the bone fracture, additional plate bending may be required during surgery. This can pose challenges such as increased surgery time and the risk of incorrect plate shaping. To enhance the accuracy of plate placement, the study introduces the Method of Anatomical Features (MAF) in conjunction with the Characteristic Product Features methodology (CPF). The utilization of the MAF enables the development of a parametric model for the contact surface between the plate and the humerus. This model is created using specialized Referential Geometrical Entities (RGEs), Constitutive Geometrical Entities (CGEs), and Regions of Interest (ROI) that are specific to the human humerus bone. By utilizing this anatomically tailored contact surface model, the standard plate model can be customized (bent) to precisely conform to the distinct shape of the patient's humerus bone during the pre-operative planning phase. Alternatively, the newly designed model can be fabricated using a specific manufacturing technology. This approach aims to improve geometrical accuracy of plate fixation, thus optimizing surgical outcomes and patient recovery.

Three-Dimensional Subject-Specific Knee Shape Reconstruction with Asynchronous Fluoroscopy Images Using Statistical Shape Modeling

Background and objectives: Statistical shape modeling (SSM) based on computerized tomography (CT) datasets has enabled reasonably accurate reconstructions of subject-specific 3D bone morphology from one or two synchronous radiographs for clinical applications. Increasing the number of radiographic images may increase the reconstruction accuracy, but errors related to the temporal and spatial asynchronization of clinical alternating bi-plane fluoroscopy may also increase. The current study aimed to develop a new approach for subject-specific 3D knee shape reconstruction from multiple asynchronous fluoroscopy images from 2, 4, and 6 X-ray detector views using a CT-based SSM model; and to determine the optimum number of planar images for best accuracy via computer simulations and in vivo experiments.

Methods: A CT-based SSM model of the knee was established from 60 training models in a healthy young Chinese male population. A new two-phase optimization approach for 3D subject-specific model reconstruction from multiple asynchronous clinical fluoroscopy images using the SSM was developed, and its performance was evaluated via computer simulation and in vivo experiments using one, two and three image pairs from an alternating bi-plane fluoroscope.

Results: The computer simulation showed that subject-specific 3D shape reconstruction using three image pairs had the best accuracy with RMSE of 0.52 ± 0.09 and 0.63 ± 0.085 mm for the femur and tibia, respectively. The corresponding values for the in vivo study were 0.64 ± 0.084 and 0.69 ± 0.069 mm, respectively, which was significantly better than those using one image pair (0.81 ± 0.126 and 0.83 ± 0.108 mm). No significant differences existed between using two and three image pairs.

Conclusion: A new two-phase optimization approach was developed for SSM-based 3D subject-specific knee model reconstructions using more than one asynchronous fluoroscopy image pair from widely available alternating bi-plane fluoroscopy systems in clinical settings. A CT-based SSM model of the knee was also developed for a healthy young Chinese male population. The new approach was found to have high mode reconstruction accuracy, and those for both two and three image pairs were much better than for a single image pair. Thus, two image pairs may be used when considering computational costs and radiation dosage. The new approach will be useful for generating patient-specific knee models for clinical applications using multiple asynchronous images from alternating bi-plane fluoroscopy widely available in clinical settings. The current SSM model will serve as a basis for further inclusion of training models with a wider range of sizes and morphological features for broader applications.

Estimating and abstracting the 3D structure of feline bones using neural networks on X-ray (2D) images

Computing 3D bone models using traditional Computed Tomography (CT) requires a high-radiation dose, cost and time. We present a fully automated, domain-agnostic method for estimating the 3D structure of a bone from a pair of 2D X-ray images. Our triplet loss-trained neural network extracts a 128-dimensional embedding of the 2D X-ray images. A classifier then finds the most closely matching 3D bone shape from a predefined set of shapes. Our predictions have an average root mean square (RMS) distance of 1.08 mm between the predicted and true shapes, making our approach more accurate than the average achieved by eight other examined 3D bone reconstruction approaches. Each embedding extracted from a 2D bone image is optimized to uniquely identify the 3D bone CT from which the 2D image originated and can serve as a kind of fingerprint of each bone; possible applications include faster, image content-based bone database searches for forensic purposes.

Long‑term treatment with salicylate enables NMDA receptors and impairs AMPA receptors in C57BL/6J mice inner hair cell ribbon synapse

Salicylate is widely used to produce animal models of tinnitus in mice and/or rats. The side effects on auditory function, including hearing loss and tinnitus, are considered the results of the auditory nerve dysfunction. A recent study indicated that chronic treatment with salicylate for several weeks reduces compressed action potential amplitude, which is contradictory to the studies reporting excessive activation of N-methyl-D-aspartate receptors (NMDAR) in tinnitus-induced animals. The specific aims of the experiment were to detect the effect of salicylate on the inner hair cells (IHCs), ribbon synapse, as well as the association between the hearing threshold and the number of mismatched ribbon synapses. In the present study, mice were injected intraperitoneally with a low dose of salicylate (200 mg/kg) for 14 days. The auditory brainstem response and otoacoustic emission were measured to assess auditory function of the mice. The postsynaptic regions of IHC were identified with two types of immunostaining targets: Postsynaptic density protein 95 and Glu2/3. The number of spheres was counted and the synapses were reconstructed in 3-dimensional images. Increases in distortion product otoacoustic emissions amplitudes of the salicylate group were detected, however, an elevation in the hearing threshold was also observed. A mismatch between pre-and post-ribbon synapses was observed. In addition, the cochlear components, including the numbers of outer hair cells and IHCs, were unlikely to be affected by salicylate. IHC ribbon synapses were more susceptible to salicylate stimuli. Furthermore, mismatch of pre- and post-ribbon synapses may indicate a competitive inhibition between NMDAR and α-amino-3-hydroxy-5-methyl-4-isoxa-zole-propionate receptors and dysfunction of ribbon synapses.

Software Framework for the Creation and Application of Personalized Bone and Plate Implant Geometrical Models

Computer-Assisted Orthopaedic Surgery (CAOS) defines a set of techniques that use computers and other devices for planning, guiding, and performing surgical interventions. The important components of CAOS are accurate geometrical models of human bones and plate implants, which can be used in preoperational planning or for surgical guiding during an intervention. Software framework which is introduced in this study is based on the Model-View-Controller (MVC) architectural pattern, and it uses 3D models of bones and plate implants developed by the application of the Method of Anatomical Features (MAF). The presented framework may be used for preoperative planning processes and for the production of personalized plate implants. The main idea of the research was to develop a novel integrated software framework which will provide improved personalized healthcare to the patient, and at the same time, provide the surgeon with more control over the patient's treatment and recovery.

On the Development of Virtual Reality Scenarios for Computer-Assisted Biomedical Applications

The modelling of virtual environments and scenarios is an important area of research for the development of new computer-assisted systems in the areas of engineering and medicine, particularly in the area of biomechanics and biomedical engineering. One of the main issues while designing a virtual environment is the level of realism, which depends on the computing capacity and the level of accuracy and usefulness of the generated data. Thus, the dilemma is between the aesthetic realism and the information utility. This paper proposes a methodology to develop low-cost and high-quality virtual environments and scenarios for computer-aided biomedical applications. The proposed methodology is based on the open-source software Blender and the Visualization Toolkit libraries (VTK). In order to demonstrate the usability of the proposed methodology, the design and development of a computer-assisted biomedical application is presented and analysed.

Additive Manufacturing Techniques for the Reconstruction of 3D Fetal Faces

This paper deals with additive manufacturing techniques for the creation of 3D fetal face models starting from routine 3D ultrasound data. In particular, two distinct themes are addressed. First, a method for processing and building 3D models based on the use of medical image processing techniques is proposed. Second, the preliminary results of a questionnaire distributed to future parents consider the use of these reconstructions both from an emotional and an affective point of view. In particular, the study focuses on the enhancement of the perception of maternity or paternity and the improvement in the relationship between parents and physicians in case of fetal malformations, in particular facial or cleft lip diseases.

A preliminary study for determination of three-dimensional root apex position of the maxillary teeth using camera calibration technology

OBJECTIVES

To propose a novel method for determining the three-dimensional (3D) root apex position of maxillary teeth using a two-dimensional (2D) panoramic radiograph image and a 3D virtual maxillary cast model.

METHODS

The subjects were 10 adult orthodontic patients treated with non-extraction. The multiple camera matrices were used to define transformative relationships between tooth images of the 2D panoramic radiographs and the 3D virtual maxillary cast models. After construction of the root apex-specific projective (RASP) models, overdetermined equations were used to calculate the 3D root apex position with a direct linear transformation algorithm and the known 2D co-ordinates of the root apex in the panoramic radiograph. For verification of the estimated 3D root apex position, the RASP and 3D-CT models were superimposed using a best-fit method. Then, the values of estimation error (EE; mean, standard deviation, minimum error and maximum error) between the two models were calculated.

RESULTS

The intraclass correlation coefficient values exhibited good reliability for the landmark identification. The mean EE of all root apices of maxillary teeth was 1.88 mm. The EE values, in descending order, were as follows: canine, 2.30 mm; first premolar, 1.93 mm; second premolar, 1.91 mm; first molar, 1.83 mm; second molar, 1.82 mm; lateral incisor, 1.80 mm; and central incisor, 1.53 mm.

CONCLUSIONS

Camera calibration technology allows reliable determination of the 3D root apex position of maxillary teeth without the need for 3D-CT scan or tooth templates.

Effect of different gentamicin dose on the plasticity of the ribbon synapses in cochlear inner hair cells of C57BL/6J mice

Faithful information transfer at the hair cell afferent synapse requires synaptic transmission to be both reliable and temporally precise. The release of neurotransmitter must exhibit both rapid on and off kinetics to accurately follow acoustic stimuli with a periodicity of 1 ms or less. To ensure such remarkable temporal fidelity, the cochlear hair cell afferent synapse undoubtedly relies on unique cellular and molecular specializations. To study effects of different doses of gentamicin on the changes of synaptic ribbons of cochlear inner hair cells (IHCs) in mice, the availability of genetic information, transgenic and knock-out animals make the C57BL/6J mouse a primary model in biomedical research. Aminoglycoside ototoxicity, however, has rarely been studied in mature mice because they are considered highly resistant to the drugs. This study presents models for gentamicin ototoxicity in adult C57BL/6J mouse strains. Five-week-old mice were injected intraperitoneally once daily with 50-300 mg gentamicin base/kg body weight for 7 days. Higher doses of gentamicin appear to be associated with earlier hearing damage in C57BL/6J mice, although not necessarily with more severe damage. At 200 mg/kg, gentamicin appears to induce significant hearing damage while not significantly affect the animal's general condition. Therefore, 200 mg/kg may be an ideal dose for ototoxicity modeling in C57BL/6J mice using gentamicin. In the early period of different dose of gentamicin effect, when the number of hair cells had not changed, the number changes of IHC ribbon synapses had taken place. Through the number of ribbon synapses changing, IHCs increased or decreased connections with spiral ganglion nerves (SGNs). The ribbon synapses played a compensatory role for gentamicin ototoxicity, while this effect was not sufficient to maintain the normal threshold of hearing.

Three types of the serial segmented images suitable for surface reconstruction

Stereoscopic surface models of human organs can be manipulated in real time. This is a significant feature of an interactive simulation system used for clinical practice. Objective surface models are obtainable from the accumulation of each structure's serial outlines, followed by surface reconstruction. The segmented images including the outlines can be divided into outlined images, white-filled images, and color-filled images. The purpose of this study was to report the benefits of the three types of segmented images for surface reconstruction. For the raw data, sectioned images of a male cadaver head were used. In the sectioned images, 91 structures were delineated for the preparation of 234 serial outlined images. The outlined images were converted into white-filled and color-filled images; the reverse conversion was also possible. The outlined images, including the original sectioned images, could be the source not only of surface models but also of volume models. The white-filled images, with a minimal file size, were preferred for separate surface reconstruction of the individual structures. The color-filled images, which allowed for recognition of the entire outlined structures simultaneously, were regarded as a good choice for the construction of several surface models. For the process, we employed a variety of software packages including those for animation, where the images were compatible. This information can be used by other investigators to build their own three-dimensional models. In addition, the surface models of detailed structures in the head, accompanied by the corresponding sectioned and segmented images, will hopefully contribute to various simulations that can be useful to clinicians.