Contour Reconstruction Research Articles

A fast computational approach for illusory contour reconstruction

Illusory contour reconstruction can be modeled as a minimization problem with a tractable variational level set formulation, utilizing Euler’s elastica to reconstruct the illusory boundaries. However, this kind of formulation is very difficult to solve numerically as it is hard to implement such optimization algorithms efficiently in practice. In this paper, we propose an equivalently reduced variational level set formulation by taking the level set functions as signed distance functions. Technically, an alternating direction method of multipliers (ADMM) is developed by introducing some auxiliary variables, Lagrange multipliers and applying an alternating optimization strategy. With the proposed ADMM method, the minimization problem can be transformed into a series of sub-problems, which can be solved easily via using the Gauss-Seidel iterations and Fast Fourier Transform (FFT). The corresponding level set functions are regarded as signed distance functions during computation process using a simple algebraic projection method, which avoids the traditional re-initialization process for conventional level set functions. Extensive experiments have been conducted on both synthetic and real images, which validated the proposed approach, and demonstrated the advantages of the proposed ADMM-Projection (ADMM-P) method over the existing algorithms based on traditional gradient descent method (GDM) in terms of computational efficiency.

Contour reconstruction of three-dimensional spiral CT damage image

In order to improve the diagnosis and analysis ability of 3D spiral CT and to reconstruct the contour of 3D spiral CT damage image, a contour reconstruction method based on sharpening template enhancement for 3D spiral CT damage image is proposed. This method uses the active contour LasSO model to extract the contour feature of the 3D spiral CT damage image and enhances the information by sharpening the template enhancement technique and makes the noise separation of the 3D spiral CT damage image. The spiral CT image was processed with ENT, and the statistical shape model of 3D spiral CT damage image was established. The gradient algorithm is used to decompose the feature to realize the analysis and reconstruction of the contour feature of the 3D spiral CT damage image, so as to improve the adaptive feature matching ability and the ability to locate the abnormal feature points. The simulation results show that in the 3D spiral CT damage image contour reconstruction, the proposed method performs well in the feature matching of the output pixels, shortens the contour reconstruction time by 20/ms, and provides a strong ability to express the image information. The normalized reconstruction error of CES is 30%, which improves the recognition ability of 3D spiral CT damage image, and increases the signal-to-noise ratio of peak output by 40 dB over other methods.

Additively manufactured versus conventionally pressed cranioplasty implants: An accuracy comparison

This article compared the accuracy of producing patient-specific cranioplasty implants using four different approaches. Benchmark geometry was designed to represent a cranium and a defect added simulating a craniectomy. An 'ideal' contour reconstruction was calculated and compared against reconstructions resulting from the four approaches -'conventional', 'semi-digital', 'digital - non-automated' and 'digital - semi-automated'. The 'conventional' approach relied on hand carving a reconstruction, turning this into a press tool, and pressing titanium sheet. This approach is common in the UK National Health Service. The 'semi-digital' approach removed the hand-carving element. Both of the 'digital' approaches utilised additive manufacturing to produce the end-use implant. The geometries were designed using a non-specialised computer-aided design software and a semi-automated cranioplasty implant-specific computer-aided design software. It was found that all plates were clinically acceptable and that the digitally designed and additive manufacturing plates were as accurate as the conventional implants. There were no significant differences between the additive manufacturing plates designed using non-specialised computer-aided design software and those designed using the semi-automated tool. The semi-automated software and additive manufacturing production process were capable of producing cranioplasty implants of similar accuracy to multi-purpose software and additive manufacturing, and both were more accurate than handmade implants. The difference was not of clinical significance, demonstrating that the accuracy of additive manufacturing cranioplasty implants meets current best practice.

Application of the 3D digital ostectomy template (DOT) in mandibular angle ostectomy (MAO)

BackgroundMandibular angle ostectomy (MAO) is a standard approach in reconstruction of facial contour that is commonly used in East Asian patients with prominent mandibular angles (PMA). MAO is commonly performed via an intraoral approach to reduce scar visibility and risk of facial nerve injury. Since this intraoral approach for MAO has limited visual guidance during the procedure, plastic surgeons often perform the operation based on personal clinical experience. Therefore, we designed a 3D digital ostectomy template (DOT) for guidance during surgery to improve the accuracy and safety of MAO. Methods10 female patients (average age 25.3 years) with PMA were enrolled in this study from August 2014 to October 2015. The DOTs were designed and printed preoperatively and utilized in the operation to guide the osteotomy. The excised mandibular angle bone and the DOTs were measured respective to each other. The data were analyzed to verify the feasibility and safety of the DOT. ResultsAll of the patients were satisfied with the surgical results, and no complications such as fracture, hemorrhage and infection occurred. The distance from gonion (Go) along inferior margin of mandible forward to the distal end of the excised bone is “a”. The distance from Go along posterior margin of ramus upward to the distal end of the excised bone is “b”. The widest distance from Go to the ostectomy line is denoted by “c”. Similarly, the corresponding distance in the DOT is denoted by “a'”, “b'”, “c'”. The statistical results showed that left a vs a’, b vs b’, c vs c’ was 63.27 ± 6.39 mm vs 62.97 ± 6.30 mm (p > 0.05), 23.98 ± 2.25 mm vs 21.83 ± 2.27 mm (p < 0.05), 13.58 ± 2.24 mm vs 13.37 ± 2.14 mm (p > 0.05), respectively. The right a vs a’, b vs b’, c vs c’ was 62.92 ± 5.00 mm vs 62.72 ± 4.99 mm (p > 0.05), 24.03 ± 1.88 mm vs 21.80 ± 1.91 mm (p < 0.05), 13.36 ± 1.70 mm vs 13.22 ± 1.72 mm (p > 0.05), respectively. The results indicate a significant difference between b and b’ both on the right and left sides. ConclusionThrough the application of DOT in MAO, the accuracy and safety of the operation were improved significantly. Unfortunately, the osteotomy could not be guided well in the posterior rim of the ramus. Further improvements in the surgical template are needed for application in PMA associated with oversized chin deformity or in PMA associated with large mandibular angle and severe involution.

Coronal trunk imbalance in idiopathic scoliosis: Does gravity line localisation confirm the physical findings?

Adolescent idiopathic scoliosis (AIS) can require surgical procedures that have major consequences. Coronal imbalance as assessed clinically using a plumb line is a key criterion for selecting patients to surgery. Nevertheless, the reference standard for assessing postural balance of the trunk is gravity line localisation within a validated frame of reference. Recent studies have established that the gravity line can be localised after body contour reconstruction from biplanar radiographs. The objective of this study was to validate a gravity line localisation method based on biplanar radiographs in a population with AIS then to validate gravity line position versus plumb line position. Plumb line and gravity line assessments of coronal balance correlate with each other. A gravity line localisation method based on biplanar radiography was validated in 14 patients with AIS versus force platform as the method of reference. Normal plumb line and gravity line positions were determined in 27 asymptomatic adolescents using biplanar radiography. The results of the two methods were then compared in 53 patients with AIS. The reliability of gravity line localisation in the coronal plane based on biplanar radiography was 2.4mm (95% confidence interval). The distance between the gravity line and the middle of the line connecting the centres of the two femoral heads (HA) showed a strongly significant association with plumb line position computed as the distance from the vertical line through the middle of T1 and the centre of the S1 endplate (T1V/S): r=0.71, p<0.0001. Of the 20 patients with plumb line results indicating coronal imbalance, 11 (55%) had a normal gravity line-to-HA distance. Of the 33 patients with normal plumb line results, 7 (21%) had an abnormal gravity line-to-HA distance. The results of this study validate gravity line determination from biplanar radiographs in a population with AIS. Plumb line position correlated significantly with gravity line position but was less accurate for guiding surgical decisions. IV, retrospective study.

3D Compton scattering imaging and contour reconstruction for a class of Radon transforms

Compton scattering imaging is a nascent concept arising from the current development of high-sensitive energy detectors and is devoted to exploit the scattering radiation to image the electron density of the studied medium. Such detectors are able to collect incoming photons in terms of energy. This paper introduces potential 3D modalities in Compton scattering imaging (CSI). The associated measured data are modeled using a class of generalized Radon transforms. The study of this class of operators leads to build a filtered back-projection kind algorithm preserving the contours of the sought-for function and offering a fast approach to partially solve the associated inverse problems. Simulation results including Poisson noise demonstrate the potential of this new imaging concept as well as the proposed image reconstruction approach.

초소수성 실린더 표면에 충돌하는 액적의 움직임에 관한 수치해석 연구

Droplet impact is widely used in various engineering applications. Various conditions could affect the droplet evolution during impacting process. We have focused on geometrical effect from curved surface. Due to curvature of the wall, dynamics of the droplet would be quite different compared to the flat surface. We also paid great attentions to the contact line behavior. To augment the curvature effect, cylindrical surface with superhydrophobic characteristic was considered in this study. Very high advancing (165o) and receding angle (160o) associated with superhydrophobic surface makes distinctive difference in its behavior between axial and circumferential direction. We have numerical studied the impact process of the 3D droplet on cylindrical surface using Level Contour Reconstruction(LCRM) method. We found that impact behavior is pretty much same as flat surface in the axial direction. In circumferential direction, contact diameter has certain limit for higher impact velocity. Contact time of the droplet is also quite different compared to the flat surface in circumferential direction. At lower impact velocity, contact time of the droplet decrease rapidly with increased impact velocity but has negligible change at higher values.

Audio-visual speech processing and analysis based on subspace projections

Subject of Research.The paper deals with the problems of the mutual reconstruction (transformation) of acoustic and visual components (modalities) of speech. Audio recording of voice represents the acoustic component whereas the parallel video recording of the speaker’s face comprises the visual component. Because of the different physical nature of these modalities, their mutual analysis is accompanied by numerous difficulties. Reconstruction methods can be used to overcome these difficulties. Method. The proposed approach is based on Principal Component Analysis (PCA), Multiple Linear Regression (MLR), Partial Least Squares regression (PLS regression) and K-means clustering algorithm. Moreover, attention is paid to data preprocessing. Mel-frequency cepstral coefficients (MFCCs) are used as acoustic features, and twenty key points, which represent the mouth contour, comprise visual features. Main Results. The experiments on the reconstruction of the mouth contour from the MFCCs are presented. The experiments were carried out on VidTIMIT dataset of audio-visual phrase recordings in English. Four variants of the proposed approach were tested and evaluated. They are based on PCA and PLS regression with clustering and without it. Quantitative (objective) and qualitative (subjective) assessment confirmed the efficiency of the proposed approach. The implementation based on PLS regression with preliminary clustering led to the best results. Practical Relevance. The proposed approach can be used to develop various bimodal biometric systems, voice-driven virtual “avatars”, mobile access control systems and other useful human-computer interaction solutions. Moreover, it is shown that, given the proper implementation, PCA and PLS reduce significantly the computational complexity of the reconstruction operation. In addition, the clustering step can be omitted to increase additionally the processing speed at the cost of slightly lower reconstruction quality.

The Medial Sural Artery Perforator Flap: The First Choice for Soft-Tissue Reconstruction About the Knee.

The gastrocnemius muscle flap may be considered the first choice in many cases of soft-tissue reconstruction about the knee. Limited arc of rotation and reach of the flap as well as unsightly muscle bulk are major disadvantages and were the impetus to look for a local alternative. The aim of this study is to present a consecutive series of patients with a reconstruction about the knee involving the medial sural artery perforator flap (MSAPF). A consecutive series of 17 cases of defect reconstructions about the knee using the MSAPF is described, with an emphasis on early postoperative complications. No major flap-related complications occurred except 1 case of tip necrosis that healed uneventfully after excision and secondary suture. Two patients with direct donor-site closure had a minor complication that required no revision, and 2 had partial skin-graft loss. In summary, use of this pedicled perforator flap represents a reliable technique for soft-tissue reconstruction about the knee with an acceptable complication rate and optimal contour reconstruction without the need for a skin graft and secondary debulking procedures. The range of motion associated with the MSAPF in comparison to the range associated with the gastrocnemius muscle flap is increased so that more proximal and lateral defects can be covered. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

A hybrid interface tracking – level set technique for multiphase flow with soluble surfactant

A formulation for soluble surfactant transport in multiphase flows recently presented by Muradoglu and Tryggvason (JCP 274 (2014) 737–757) [17] is adapted to the context of the Level Contour Reconstruction Method, LCRM, (Shin et al. IJNMF 60 (2009) 753–778, [8]) which is a hybrid method that combines the advantages of the Front-tracking and Level Set methods. Particularly close attention is paid to the formulation and numerical implementation of the surface gradients of surfactant concentration and surface tension. Various benchmark tests are performed to demonstrate the accuracy of different elements of the algorithm. To verify surfactant mass conservation, values for surfactant diffusion along the interface are compared with the exact solution for the problem of uniform expansion of a sphere. The numerical implementation of the discontinuous boundary condition for the source term in the bulk concentration is compared with the approximate solution. Surface tension forces are tested for Marangoni drop translation. Our numerical results for drop deformation in simple shear are compared with experiments and results from previous simulations. All benchmarking tests compare well with existing data thus providing confidence that the adapted LCRM formulation for surfactant advection and diffusion is accurate and effective in three-dimensional multiphase flows with a structured mesh. We also demonstrate that this approach applies easily to massively parallel simulations.

Gingival Zenith as a Reference for Bonding Braces

Orthodontics for adults is the current reality of many practices since the greater accessibility of orthodontic treatment lately. The association of orthodontics with prosthetic rehabilitation is a frequent scenario and requires an adequate multidisciplinary interaction to aim not only orthodontic alignment but also the treatment of other needs. Often, orthodontic planning is one of the steps in the oral rehabilitation and the ortho-periotic interaction is present in the idealization of a harmonious smile. Thus, the techniques of orthodontic leveling should be adapted to the individuality of the patient and the proposal of oral rehabilitation. When there is a need for prosthetic finishing, gingival collage can equalize the zenith line and periodontal aesthetic. The present study aims at the elaboration of a manual to guide orthodontists in the bonding of braces using as a reference the reconstruction of an ideal gingival contour.

Reconstruction of Mandibular Contour Using Individualized High-Density Porous Polyethylene (Medpor®) Implants Under the Guidance of Virtual Surgical Planning and 3D-Printed Surgical Templates.

The mandibular contour plays a significant role in the beautiful and youthful look but the reconstruction remains a challenging problem. The objective of this study was to evaluate the use of individualized high-density porous polyethylene (Medpor®) implants for comprehensive reconstruction of mandibular contour with the aid of computer-aided design/computer-aided manufacturing (CAD/CAM). From 2010 to 2014, 12 patients with mandibular contour deformities were enrolled in our retrospective study. Mandible models and individualized surgical templates were fabricated by three-dimensional (3D) printing and Medpor® implants were made according to the surgical templates. The Medpor® implants were used for both unilateral and bilateral mandibular contour deformities. In four cases, simultaneous mandibular orthognathic surgery was performed with unilateral mandibular contour reconstruction. Eleven patients had a reposeful postoperative recovery with no complication. Delayed infection was shown in one patient and the Medpor® implant was removed. All the 11 patients had the mandibular contour reconstructed satisfactorily. The technique and cases presented demonstrate the utility of Medpor® implants with CAD/CAM in comprehensive mandibular contour reconstruction. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Biomechanical research on contour cage with transacetabular screws fixation in revision total hip arthroplasty

BackgroundUse biomechanical technique to access the strain distribution and stability of Contour anti-protrusion cage with or without the whole circumference acetabular cup fixation by the transacetabular screws. MethodsPelvic specimens from 10 male cadavers were used for the biomechanical test. The models of type C bone defect were copied according to the AAOS classification. Group 1: the contour reconstruction ring was fixed only by flange screws; Group 2: the contour reconstruction ring was fixed both by flange screws and transacetabular screws in dome. Under load in Heel Strike, Midstance, and Toe off phase, the transverse and longitudinal strains were measured in both the superior measure site near the root of the iliac wing and the inferior measure site near the root of the ischium. The relative displacement between the anterior inferior spine and the root of ischium below acetabular component was also measured. FindingsCompared with Group 1, the transverse and longitudinal pressure strain of Group 2 on the superior measure site decreased, and measure sites also showed reductions on the inferior under load under three different gait phases. The result of mean relative displacement showed transacetabular screws fixation couldn't provide significant improvement of displacement prevention. InterpretationBiomechanical test showed that under the premise of a satisfied bone allograft and well-fixed flange screws in iliac and ischium, the satisfactory initial stability of the reconstruction cup can be achieved, but could not be improved by transacetabular screw technique. However, the max strain in root part of the flange will be reduced using transacetabular screws in ilium, pubis and ischium together, and the strain distribution will also be improved.

Numerical Aspects of Cone Beam Contour Reconstruction

We describe a method for directly calculating the contours of a function from cone beam data. The algorithm is based on a new inversion formula for the gradient of a function presented in Louis (Inverse Probl 32(11):115005, 2016. http://stacks.iop.org/0266-5611/32/i=11/a=115005). The Radon transform of the gradient is found by using a Grangeat type of formula, reducing the inversion problem to the inversion of the Radon transform. In that way the influence of the scanning curve, vital for all exact inversion formulas for complete data, is avoided Numerical results are presented for the circular scanning geometry which neither fulfills the Tuy–Kirillov condition nor the much weaker condition given by the author in Louis (Inverse Probl 32(11):115005, 2016. http://stacks.iop.org/0266-5611/32/i=11/a=115005).

モルフォロジーに基づく画像の輪郭分解・再構成(応用)

モルフォロジーに基づく画像の輪郭分解・再構成(応用)

Automated Planning With Multivariate Shape Descriptors for Fibular Transfer in Mandibular Reconstruction.

This paper introduces methods to automate preoperative planning of fibular segmentation and placement for mandibular reconstruction with fibular flaps. Preoperative virtual planning for this type of surgery has been performed by manual adjustment of many parameters, or based upon a single feature of the reconstruction. We propose a novel planning procedure formulated as a nonconvex minimization problem of an objective function using the multilateral shape descriptors. A retrospective study was designed and 120 reconstruction plans were reproduced using computed tomography images with oral surgeons. The proposed automated planning model was quantitatively compared with both the existing model and the surgeons' plans. The results show that the developed framework attains stable automated planning that agrees with the surgeons' decisions. This method addresses tradeoff problems between symmetric reconstruction and restoration of the native contour of the mandible.

Efficacy analysis of endoscopic stage Ⅰ reconstruction of nasal contour and function

Objective:The aim of this study is to assess the effectiveness of endoscopic stage Ⅰ reconstruction of nasal contour and function.Method:Twenty subjects with severe nasal trauma,nasal bone fracture and deviation of nasal septum were selected.The surgeries of stage Ⅰ reconstruction of nasal contour and function were proceeded on 7 to 30 days after trauma.Result:The VAS scores of deformity of nasal contour and severity of nasal blockage assessed by patients decreased significantly after operation.Deflection distance of nasal dorsum measured by 3D imaging decreased significantly.In patients with abnormal nasal ventilation,the volume and the minimal cross-section area of abnormal nasal cavity increased significantly(P<0.05).Conclusion:The effectiveness of endoscopic stage Ⅰ reconstruction of nasal contour and function was excellent.The patients were satisfied with improvement of nasal contour and ventilation.

Reconstruction of lost depth data in multiview video-plus-depth communications using geometric transforms

This paper addresses depth data recovery in multiview video-plus-depth communications affected by transmission errors and/or packet loss. The novel aspects of the proposed method rely on the use of geometric transforms and warping vectors, capable of capturing complex motion and view-dependent deformations, which are not efficiently handled by traditional motion and/or disparity compensation methods. By exploiting the geometric nature of depth information, a region matching approach combined with depth contour reconstruction is devised to achieve accurate interpolation of arbitrary shapes within lost regions of depth maps. The simulation results show that, for different packet loss rates, up to 20%, the depth maps recovered by the proposed method produce virtual views with better quality than existing methods based on motion information and spatial interpolation. An average PSNR gain of 1.48dB is obtained in virtual views synthesised from depth maps using the proposed method.

Numerical investigation of interaction between rising bubbles in a viscous liquid

The rising behavior of bubbles undergoing bubble-bubble interaction in a viscous liquid is studied using a two-dimensional direct numerical simulation. Level contour reconstruction method (LCRM), one of the connectivity-free front tracking methods, is applied to describe a moving interface accurately under highly deformable conditions. This work focuses on the effects of bubble size on the interaction of two bubbles rising side-by-side in a stagnant liquid. Several characteristics of bubble-bubble interaction are analyzed quantitatively as supported by energy analysis. The results showed clear differences between small and large bubbles with respect to their interaction behavior in terms of lateral movement, vortex intensity, suppression of surface deformation, and viscous dissipation rate. Distributions of vorticity and viscous dissipation rate near the bubble interfaces also differed depending on the size of the bubbles. Strong vortices from large bubbles triggered oscillation in bubble-bubble interaction and played a dominant role in the interaction process as the size of bubbles increases.

A self-calibrating approach for the segmentation of retinal vessels by template matching and contour reconstruction.

The automated processing of retinal images is a widely researched area in medical image analysis. Screening systems based on the automated and accurate recognition of retinopathies enable the earlier diagnosis of diseases like diabetic retinopathy, hypertension and their complications. The segmentation of the vascular system is a crucial task in the field: on the one hand, the accurate extraction of the vessel pixels aids the detection of other anatomical parts (like the optic disc Hoover and Goldbaum, 2003) and lesions (like microaneurysms Sopharak etal., 2013); on the other hand, the geometrical features of the vascular system and their temporal changes are shown to be related to diseases, like the vessel tortuosity to Fabry disease Sodi etal., 2013 and the arteriolar-to-venus (A/V) ratio to hypertension (Pakter etal., 2005). In this study, a novel technique based on template matching and contour reconstruction is proposed for the segmentation of the vasculature. In the template matching step generalized Gabor function based templates are used to extract the center lines of vessels. Then, the intensity characteristics of vessel contours measured in training databases are reconstructed. The method was trained and tested on two publicly available databases, DRIVE and STARE; and reached an average accuracy of 0.9494 and 0.9610, respectively. We have also carried out cross-database tests and found that the accuracy scores are higher than that of any previous technique trained and tested on the same database.