Methods for medical applications

This article reports the analysis and preliminary design of a passive, wearable, upper limb exoskeleton to support workers in industrial environments in a vast range of repetitive tasks, offering an effective strategy to reduce the risk of injuries in production lines. The system primary purpose is to compensate for gravity loads acting on the human upper limb. The proposed exoskeleton is based on 6 Degrees-of-Freedom (DoFs) kinematics with 5-DoFs for the shoulder joint (two displacements plus three rotations) and 1-DoF for the elbow. Gravity compensation is implemented with passive elastic elements to minimize weight and reduce cost. A detailed analytical tool is developed to support the designer in the preliminary design stage, investigating the exoskeleton kinetic-static behaviour and deriving optimal design parameters for the springs over the human arm workspace. By defining specific functional requirements (i.e., the user’s features and simulated movements), computationally efficient optimization studies may be carried out to determine the optimal coefficients and positions of the springs, thus, maximizing the accuracy of the gravity balancing. Two different solutions for the arrangement of the elastic elements are investigated, and obtained results are validated with a commercial multi-body tool for some relevant movements of the user’s arm.

Keywords: design optimization , gravity balancing , Upper limb exoskeleton , virtual prototyping , wearable devices

This study presents an alternative process for designing and manufacturing customized trays for dental-whitening treatments. The process is based on a digitized approach consisting of three main stages: design of a reference model, its manufacturing by AM, and thermoforming of the tray. The aim of the study was to develop a high-performance tray, able to guarantee comfort, safety, and efficacy for whitening treatments. To evaluate the patient's experience, some tests under real operating conditions were performed. Twenty people carried out a nighttime treatment of 14 days. Each patient was asked to assess the overall level of satisfaction and the comfort of the tray and its ability to retain the gel. Tooth whitening was also determined according to the VITAPAN scale. All patients involved in the study were satisfied and provided positive feedback about comfort and tightness of the tray. At the end of the treatment, 15 out of 20 patients achieved shade A1 on the VITAPAN scale. The mean improvement in color shades was about 7. These results confirmed the great potential of the proposed dental tray. Its use was proven to guarantee a high level of quality, flexibility, and customization of dental-whitening treatments, improving comfort, safety, and efficacy.

Keywords: additive technologies , bespoke dental trays , custom design , dental engineering , digital manufacturing , esthetic dentistry , tooth whitening

Background: Orthopaedic and Trauma surgery is expected to undergo profound trans-formation as a result of the adoption of 3D technology. Among the various applications, patient specific manufacturing of splints and casts would appear to be, particularly in children, an interesting implementation. This study aims to assess the safety of patient specific 3D casts obtained with a newly developed 3D-scanning devise in a small case series. We therefore conducted a clinical outcome and pre-marketing study in 10 consecutive patients with distal radius fractures treated at an Academic Level I Pediatric Trauma Center. After the application of the 3D cast, patients underwent three consecutive evaluations in the following 21 days. The main outcome measurements were: pain, skin lesions and general comfort, and acceptance of the cast. The three domains were measured with the Visual Analogue Scale (VAS), the NPUAP/EPUAP classification and the Positive affect-Negative affect Scale for Children (PANAS-C), the Self-Assessment Manikin (SAM) clinical psychology tests and a Likert-type five item questionnaire, respectively. A final mechanical analysis of the cast was carried out to confirm product integrity. Results: The results obtained were consistently positive in the investigated domains of general comfort, efficacy of contention and mechanical integrity of the 3D-printed cast as well as in the practicability of the supply chain. Conclusions: This study provides Level IV evidence that patient specific 3D printed casts obtained with a specifically designed software were safe in the management of “buckle” fractures of the distal radius in children. These results encourage to extend the technology to the treatment of more demanding fractures.

Keywords: 3D printing , customized implants , orthopedic device , orthosis modeling , pediatrics , personalized medicine , reverse engineering

Home-based rehabilitation is becoming a gold standard for patient who have undergone knee arthroplasty or full knee replacement, as it helps healthcare costs to be minimized. Nevertheless, there is a chance of increasing adverse health effects in case of home care, primarily due to the patients' lack of motivation and the doctors' difficulty in carrying out rigorous supervision. The development of devices to assess the efficient recovery of the operated joint is highly valued both for the patient, who feels encouraged to perform the proper number of activities, and for the doctor, who can track him/her remotely. Accordingly, this paper introduces an interactive approach to angular range calculation of hip and knee joints based on the use of low-cost devices which can be operated at home. First, the patient's body posture is estimated using a 2D acquisition method. Subsequently, the 3D posture is evaluated by using the depth information coming from an RGB-D sensor. Preliminary results show that the proposed method effectively overcomes many limitations by fusing the results obtained by the state-of-the-art robust 2D pose estimation algorithms with the 3D data of depth cameras by allowing the patient to be correctly tracked during rehabilitation exercises.

Keywords: 3D model , Body tracking , Data fusion , Joints estimation , RGB-D camera

Indeterminate lung nodules detected on CT scans are common findings in clinical practice. Their correct assessment is critical, as early diagnosis of malignancy is crucial to maximise the treatment outcome. In this work, we evaluated the role of form factors as imaging biomarkers to differentiate benign vs. malignant lung lesions on CT scans. We tested a total of three conventional imaging features, six form factors, and two shape features for significant differences between benign and malignant lung lesions on CT scans. The study population consisted of 192 lung nodules from two independent datasets, containing 109 (38 benign, 71 malignant) and 83 (42 benign, 41 malignant) lung lesions, respectively. The standard of reference was either histological evaluation or stability on radiological followup. The statistical significance was determined via the Mann–Whitney U nonparametric test, and the ability of the form factors to discriminate a benign vs. a malignant lesion was assessed through multivariate prediction models based on Support Vector Machines. The univariate analysis returned four form factors (Angelidakis compactness and flatness, Kong flatness, and maximum projection sphericity) that were significantly different between the benign and malignant group in both datasets. In particular, we found that the benign lesions were on average flatter than the malignant ones; conversely, the malignant ones were on average more compact (isotropic) than the benign ones. The multivariate prediction models showed that adding form factors to conventional imaging features improved the prediction accuracy by up to 14.5 pp. We conclude that form factors evaluated on lung nodules on CT scans can improve the differential diagnosis between benign and malignant lesions.

Keywords: computed tomography , form factors , lung cancer , radiomics

Numerical simulations and Finite Element Analysis (FEA) have currently increased their applications in medical field for making preoperative plans to simulate the response of tissues and organs. Soft tissue simulations, such as colorectal simulations, can be adopted to understand the interaction between colon tissues and surrounding tissues, as well as the effects of instruments used in this kind of surgical procedures. This paper analyses through FEA the interaction between a surgical device and a colon tissue when it is fully clamped. Sensitivity analysis in the respect of the material mechanical behaviour, geometric approximation and the effect of thickness variation are investigated with the aim of setting up a virtual prototype of the surgical operation to aid mentoring and preliminary evaluation via haptic solutions. Through this investigation, the force feedback estimation that is necessary in many virtual-reality applications, may be estimated without discharging nonlinear effects that occur during clamping and that usually cannot be simulated efficiently to guarantee real-time solutions. Results are aligned with experimental data, confirming the reliability and right the set-up of FEA. Through them, the preliminary set-up of a haptic force feedback has been described and simulated through Simulink 3D animation, confirming the feasibility of the concept.

Keywords: FEA , Force feedback , Haptic device , Metamodeling , Surgical simulation , Virtual prototyping

Hepatic diseases are serious condition worldwide, and several times doctors analyse the situation and elaborates a preoperative planning based exclusively on the medical images, which are a drawback since they only provide a 2D vision and the location of the damaged tissues in the three-dimensional space cannot be easily determined by surgeons. Nowadays, with the advancement of Computer Aided Design (CAD) technologies and image segmentation, a digital liver model can be obtained to help understand the particular medical case; even with the geometric model, a virtual simulation can be elaborated. This work is divided into two phases; the first phase involves a workflow to create a liver geometrical model from medical images. Whereas the second phase provides a methodology to achieve liver prototype, using the technique of fused deposition modelling (FDM). The two stages determine and evaluate the most influencing parameters to make this design repeatable in different hepatic diseases. The reported case study provides a valuable method for optimizing preoperative plans for liver disease. In addition, the prototype built with additive manufacturing will allow the new doctors to speed up their learning curve, since they can manipulate the real geometry of the patient's liver with their hands.

Keywords: 3D printing , Convolutional neural network , FDM , Image segmentation , Liver disease

The diffusion of Fab Labs and the continuous development of Additive Manufacturing technologies are undoubtedly two relevant phenomena nowadays. The former fuels the latter and vice versa, but their mutual relationship has not been systematically explored so far. This paper presents an exploratory study based on a survey, in which various aspects of the use of 3D printers in Fab Labs are investigated. The results show how different scales of Fab Labs are present in terms of investments made in 3D printing, as well as work purposes are not negligible for many attendees. In addition, the outcomes of the survey show that 3D printers are considered easy to use, as well as manufactured parts are deemed satisfactory. Despite this, there are still some barriers to boosting the market of domestic 3D printers for Fab Lab visitors.

Keywords: 3D printers , CAD , Design for Additive Manufacturing , Fab Labs , Skills

In hip arthroplasty, preoperative planning is fundamental to reaching a successful surgery. Nowadays, several software tools for computed tomography (CT) image processing are available. However, research studies comparing segmentation tools for hip surgery planning for patients affected by osteoarthritic diseases or osteoporotic fractures are still lacking. The present work compares three different software from the geometric, dimensional, and usability perspectives to identify the best three-dimensional (3D) modelling tool for the reconstruction of pathological femoral heads. Syngo.via Frontier (by Siemens Healthcare) is a medical image reading and post-processing software that allows low-skilled operators to produce prototypes. Materialise (by Mimics) is a commercial medical modelling software. 3D Slicer (by slicer.org) is an open-source development platform used in medical and biomedical fields. The 3D models reconstructed starting from the in vivo CT images of the pathological femoral head are compared with the geometries obtained from the laser scan of the in vitro bony specimens. The results show that Mimics and 3D Slicer are better for dimensional and geometric accuracy in the 3D reconstruction, while syngo.via Frontier is the easiest to use in the hospital setting.

Keywords: bio-imaging , CT image segmentation , hip surgery , orthopaedics , reverse engineering , software comparison , surgical planning

Purpose To evaluate the accuracy of 3-D printed models of the femoral head based on preoperative computed tomography (CT) images. Other goals were to compare the cartilage thickness of bony specimen to the printed models and calculate the standard deviation between 3-D printed models based on CT images and laser scan models. Methods This retrospective study analyzed 10 patients who underwent preoperative CT imaging and hip replacement. Preoperative femoral head 3-D printed models were produced from CT images. Bony specimens were collected from surgical operations and scanned using CT and 3-D laser scanning, and cartilage thickness subsequently was measured by histological analysis. Comparisons of printed models based on CT images and printed models based on 3-D laser scanning were performed by overlapping their external surfaces using dedicated software and the standard deviation was calculated. Results The average standard deviation between the bony specimen 3-D models and preoperative 3-D printed CT femoral head models was 0.651 mm. The cartilage was approximately 1.487 mm thick. Discussion The comparison between preoperative CT image-based 3-D models and the postoperative bony specimenbased models permitted evaluation of the accuracy of preoperative CT image-based 3-D printed models. Cartilage thickness was estimated indirectly by comparing models obtained by CT and laser scanning, and it was related to the calculated standard deviation to overcome the cartilage detection limit of CT. This study shows how each step can generate accuracy errors on the final 3-D printed model. A repeatable and sustainable workflow for creating accurate and reproducible 3-D printed models could overcome this issue. Moreover, orthopedic surgeons should be aware of 3-D printed model precision in clinical practice. Conclusions This study provides encouraging results on the accuracy of 3-D printed models for surgical planning.

Keywords: 3-D printing , accuracy assessment , bone segmentation , femoral head model , hip replacement surgical procedure

Since custom-made 3D printed surgical guides for maxillofacial surgery are usually expensive, Augmented Reality (AR) can be efficiently employed to overcome the high costs. The proposed work aims to develop and test an AR application for different maxillofacial surgeries. The application consists in overlaying the cutting lines on the patient's mandible to guide the clinician during the procedure. It has been realized in Unity and preliminary tested with HoloLens 2 and a 3D printed mandible. Seven participants performed two consecutive trials. The mandible with the obtained surgical lines has been scanned after each test to digitally reconstruct the traced lines and compare them with the surgical lines previously designed. The results allowed the preliminary analysis of the developed AR system's accuracy and precision. Mean distances from the designed surgical guides showed good accuracy for the genioplasty (deviation error around 1.03 mm) and orthognathic surgery (deviation error around 1.27 mm), suggesting the applicability of HoloLens 2 for these kinds of surgery. On the contrary, the application was not suitable for the mandibular angle osteotomy (deviation error over 2.50 mm).

Keywords: Augmented reality , HoloLens 2 , Maxillofacial surgery , Surgical guides

The Obstructive Sleep Apnea Syndrome (OSA) concerns episodes of complete or partial obstruction of the upper airway. Mandibular Advancement Device (MAD) is one of the most used systems for treating this syndrome. Clinicians frequently observe a combination of OSA and periodontitis. There is no research aiming to evaluate how periodontitis staging affects the overall mandibular and maxillary dental arches in the literature. Furthermore, no one has studied the combination between OSA and periodontitis and the effects of MADs on the patients in this condition. This paper aims to develop a numerical simulation approach based on FEM and evaluate the consequences (displacement and stress fields) of the periodontitis staging on PDL and teeth of patients suffering from OSA and treated with MADs. Simulations have been performed for evaluating Stage I of periodontitis. Results highlight a correlation between bone resorption and teeth displacement and periodontal ligaments stress (the higher the bone resorption, the higher the stress and displacement).

Keywords: Finite Element Analysis , Mandibular Advancement Device , Numerical simulation , Obstructive Sleep Apnea , Periodontitis

Disability conditions characterized by hand dysfunction are particularly relevant for the use of touchscreen technology. This work investigates the effects of hand impairment produced by systemic sclerosis (SSc) on touchscreen interaction. It aims to fulfil a dual objective: to provide guidelines to design inclusive interfaces and interaction modalities for SSc patients and to design a hand physio-rehabilitation based on a touchscreen application. Eighty patients participated in the observational study and, accordingly, eighty subjects without impairments were recruited as a control cohort. A specific touchscreen application has been designed and developed including three gestures: tap, drag and drop, and pinch-to-zoom. The work allowed identifying the interface features that significantly influence the performance and, consequently, the design rules for the physio-rehabilitation application.

Keywords: Hand impairment , Human-computer interaction , Inclusive design , Interface design , Systemic sclerosis , User-centred design

Several implant materials are used in cranial surgery. Still, each one has its drawbacks, such as the risk of infections, low mechanical strength, or low osseointegration. Implants with a porous surface are considered more effective than a smooth and rough coating. The porosity density and structure also influence the mechanical properties of the final implant. Moreover, the implant properties depend on the manufacturing method. This study aims to present a custom-made cranial scaffold composed of two distinct layers. A compact inner one guarantees adequate structural properties to the scaffold. In contrast, a porous outer one lightens the scaffold structure and assures the correct osseointegration. The customized scaffold has been designed through a 3D free-form modeling system. It can be manufactured by 3D printing techniques such as direct metal laser sintering in titanium or via selective laser sintering using PEEK. The advantages and limitations of the multi-layered custom-made scaffold and the related design process are qualitatively described.

Keywords: Additive manufacturing , Craniofacial reconstruction , Customized scaffolds , Multi-layered scaffolds , Porous scaffolds

The present paper presents the development of a novel procedure for the modeling of Surgical Cutting Guides (SCGs) exploiting an implicit modeling approach. As discussed in the text, this approach allows for a streamlined and efficient design of this type of medical device. A procedural approach based on the application of a series of a priori-known implicit modeling function allows the generation of personalized surgical guides starting from the i) patient's anatomy and ii) clinical decisions made by the medical staff. The CAD procedure is detailed in the text; achieved results are discussed and compared with a traditional CAD modeling approach on three case studies.

Keywords: CAD , Implicit Modelling , Patient-Specific Instrument , Personalized Medical Device

Dealing with the design of personalized medical devices, mass production is not an option that can be hypothesized. Indeed, a cumbersome production process must be considered in such cases, mainly to account for a delicate design phase that needs to take into consideration, as input, an anatomy that vary each time. This article discusses the development of a statistical tool able to support the design of patient-specific devices. By expanding the classical formulation of the Statistical Shape Model (SSM) with the introduction of multiple levels of information within the same model, the authors have experimented with the concept of an “enhanced SSM”. While the traditional SSM only provides information on the variations that a class of shapes can manifest, the eSSM may include more levels of information. The article discusses two possible mathematical formulations of such statistical tool. Its application to the design of custom-made pelvic implants is discussed. Such application scenario is described starting from the generation of the eSSM for the pelvis. The features of interest considered in this paper are the centers of the acetabular regions of the pelvis, the segmentation of the anatomy in a series of semantical regions that must be considered when developing a load-bearing implant. Finally, the conclusions of this research are drawn and discussed together with possible future development of eSSMs.

Keywords: Biomedical engineering , Custom implant design , Human modelling , Pelvis , SSM , Statistical shape analysis

The realization of medical devices to assist the surgeon in autologous auricular reconstruction (personalized surgical guides) requires the use of depth maps images obtained from 3D scans of the patient's profile. In order to make the process of ear geometry acquisition and depth map realization faster, more comfortable for the patient and easily accessible by hospital staff, this work proposes a system able to create depth maps from a single RGB image. The proposed approach involves the integration of tools based on convolutional neural networks to build a modular system capable of isolating the ear from the profile, creating the corresponding depth map, and refining it to correct inaccuracies. The system was trained and tested using a database of human profile images and corresponding depth maps made available by the University of Notre Dame. To evaluate the result in this preliminary study, standard metrics such as mean square error and structural similarity were used, yielding results suitable for the targeted application.

Keywords: 3D vision , CNN , Depth map estimation , Ear reconstruction

Orthognathic surgery allows broad-spectrum deformity correction involving both aesthetic and functional aspects on the TMJ (temporo-mandibular joint) and on the facial skull district. The combination of Reverse Engineering (RE), Virtual Surgery Planning (VSP), Computer Aided Design (CAD), Additive Manufacturing (AM), and 3D visualization allows surgeons to plan, virtually, manipulations and the translation of the human parts in the operating room. This work's aim was to define a methodology, in the form of a workflow, for surgery planning and for designing and manufacturing templates for orthognathic surgery. Along the workflow, the error chain was checked and the maximum error in virtual planning was evaluated. The three-dimensional reconstruction of the mandibular shape and bone fragment movements after segmentation allow complete planning of the surgery and, following the proposed method, the introduction of both the innovative evaluation of the transversal intercondylar distance variation after mandibular arch advancement/set and the possibility of use of standard plates to plan and realize a customized surgery. The procedure was adopted in one clinical case on a patient affected by a class III malocclusion with an associated open bite and right deviation of the mandible with expected good results. Compared with the methods from most recent literature, the presented method introduces two elements of novelty and improves surgery results by optimizing costs and operating time. A new era of collaboration among surgeons and engineer has begun and is now bringing several benefits in personalized surgery.

Keywords: 3D-modelling , computer-aided surgery , methodology , orthognathic surgery , rapid manufacturing , surgical template

Mitral regurgitation is a common valvular disorder. Transcatheter edge-to-edge repair (TEER) is a minimally invasive technique which involves holding together the middle segments of the mitral valve leaflets, thereby reducing regurgitation. To date, MitraClipâ„¢ is the only Food and Drug Administration (FDA)-approved device for TEER. The MitraClip procedure is technically challenging, characterised by a steep learning curve. Training is generally performed on simplified models, which do not emphasise anatomical features, realistic materials, or procedural scenarios. The aim of this study is to propose a novel, 3D printed simulator, with a major focus on reproducing the anatomy and plasticity of all areas of the heart involved and specifically the ones of the mitral valve apparatus. A three-dimensional digital model of a heart was generated by segmenting computed tomography (CT). The model was subsequently modified for: (i) adding anatomical features not fully visible with CT; (ii) adapting the model to interact with the MitraClip procedural equipment; and (iii) ensuring modularity of the system. The model was manufactured with a Polyjet technology printer, with a differentiated material assignment among its portions. Polypropylene threads were stitched to replicate chordae tendineae. The proposed system was successfully tested with MitraClip equipment. The simulator was assessed to be feasible to practice in a realistic fashion, different procedural aspects including access, navigation, catheter steering, and leaflets grasping. In addition, the model was found to be compatible with clinical procedural imaging fluoroscopy equipment. Future studies will assess the effect of the proposed training system on improving TEER training.

Keywords: 3D printing , MitraClip procedure , mitral valve regurgitation , Polyjet , segmentation , simulation-based training , transcatheter edge-to-edge repair