Personalized 3D reconstruction of the rib cage for clinical assessment of trunk deformities

Scoliosis is a 3D deformity of the spine and rib cage. Extensive validation of 3D reconstruction methods of the spine from biplanar radiography has already been published. In this article, we propose a novel method to reconstruct the rib cage, using the same biplanar views as for the 3D reconstruction of the spine, to allow clinical assessment of whole trunk deformities. This technique uses a semi-automatic segmentation of the ribs in the postero-anterior X-ray view and an interactive segmentation of partial rib edges in the lateral view. The rib midlines are automatically extracted in 2D and reconstructed in 3D using the epipolar geometry. For the ribs not visible in the lateral view, the method predicts their 3D shape. The accuracy of the proposed method has been assessed using data obtained from a synthetic bone model as a gold standard and has also been evaluated using data of real patients with scoliotic deformities. Results show that the reconstructed ribs enable a reliable evaluation of the rib axial rotation, which will allow a 3D clinical assessment of the spine and rib cage deformities.     

Morphological patterns of the rib cage and lung in the healthy and adolescent idiopathic scoliosis

The morphology of the rib cage affects both the biomechanics of the upper body's musculoskeletal structure and the respiratory mechanics. This becomes particularly important when evaluating skeletal deformities, as in adolescent idiopathic scoliosis (AIS). The aim of this study was to identify morphological characteristics of the rib cage in relation to the lung in patients with non-deformed and scoliotic spines. Computed tomography data of 40 patients without any visible spinal abnormalities (healthy group) and 21 patients with AIS were obtained retrospectively. All bony structures as well as the right and left lung were reconstructed using image segmentation. Morphological parameters were calculated based on the distances between characteristic morphological landmarks. These parameters included the rib position, length, and area, the rib cage depth and width, and the rib inclination angle on either side, as well as the spinal height and length. Furthermore, we determined the left and right lung volumes, and the area of contact between the rib cage and lung. Differences between healthy and scoliotic spines were statistically analysed using the t-test for unpaired data. The rib cage of the AIS group was significantly deformed in the dorso-ventral and medio-lateral directions. The anatomical proximity of the lung to the ribs was nearly symmetrical in the healthy group. By contrast, within the AIS group, the lung covered a significantly greater area on the left side of the rib cage at large thoracic deformities. Within the levels T1–T6, no significant difference in the rib length, depth to width relationship, or area was observed between the healthy and AIS groups. Inferior to the lung (T7–T12), these parameters exhibited greater variability. The ratio between the width of the rib cage at T6 and the thoracic spinal height (T1–T12) was significantly increased within the thoracic AIS group (1.1 ± 0.08) compared with the healthy group (1.0 ± 0.05). No statistical differences were found between the lung volumes among all the groups. While the rib cage was frequently strongly deformed in the AIS group, the lung and its surrounding ribs appeared to be normally developed. The observed rib hump in AIS appeared to be formed particularly by a more ventral position of the ribs on the concave side. Furthermore, the rib cage width to spinal height ratio suggested that the spinal height of the thoracic AIS-spine is reduced. This indicates that the spine would gain its growth-related height after correcting the spinal deformity. These are the important aspects to consider in the aetiology research and orthopaedic treatment of AIS.     

Quantitative morphometry of the orbit in Chinese adults based on a three-dimensional reconstruction method

The three‐dimensional (3D) reconstruction technique serves as a practical tool in diagnosis, surgical planning, and outcome prediction of plastic and reconstructive surgery. In our study, the morphologic features of the Chinese adult orbit were described by 11 anatomic parameters using a 3D reconstruction technique. Sixty‐four Chinese adults were selected randomly from patients who had undergone craniofacial computed tomography (CT) scans to diagnose conditions other than craniofacial or orbital deformations. The morphologic parameters of orbit such as bony orbital volume, orbital foramen area and orbital rim perimeter were measured on 3D models using this technique. Differences between the two orbits and between the two sexes were investigated. The method of measurement showed high reproducibility of results. No difference between the two orbits was found. There were significant differences between men and women in all anatomic parameters other than orbital height. In men and women, respectively, mean bony orbital volume was 26.02 and 23.32 mL, mean orbital foramen area 11.80 and 11.10 cm², mean orbital rim perimeter 12.65 and 12.20 cm, mean orbital height 33.35 and 33.22 mm, mean orbital width 40.02 and 38.00 mm; mean orbital floor length 47.93 and 46.18 mm, mean orbital roof length 52.93 and 50.89 mm, mean medial orbital wall length 46.43 and 44.41 mm, mean lateral orbital wall length 48.38 and 46.91 mm, mean intraorbital distance 27.18 and 25.11 mm, mean extra‐orbital distance 98.77 and 93.69 mm. It is concluded that the measurements of these orbital parameters could be obtained from a 3D reconstruction method. The two orbits were symmetric based on orbital volume and other anatomic parameters. Orbital size was significantly smaller in women than in men; orbital height, however, was similar. The findings of the present study allow for quantification of the orbital features of Chinese adults and provide parameters for preoperative planning and prediction of postoperative outcome.     

Chest wall kinematics in young subjects with Pectus excavatum

Quantifying chest wall kinematics and rib cage distortion during ventilatory effort in subjects with Pectus excavatum (PE) has yet to be defined. We studied 24 patients: 19 during maximal voluntary ventilation (MVV) and 5 during MVV and cycling exercise (CE). By optoelectronic plethysmography (OEP) we assessed operational volumes in upper rib cage, lower rib cage and abdomen. Ten age-matched healthy subjects served as controls. Patients exhibited mild restrictive lung defect. During MVV end-inspiratory and end-expiratory volumes of chest wall compartments increased progressively in controls, whereas most patients avoided dynamic hyperinflation by setting operational volumes at values lower than controls. Mild rib cage distortion was found in three patients at rest, but neither in patients nor in controls did MVV or CE consistently affect coordinated motion of the rib cage. Rib cage displacement was not correlated with a CT-scan severity index. Conclusions, mild rib cage distortion rarely occurs in PE patients with mild restrictive defect. OEP contributes to clinical evaluation of PE patients.     

3D reconstruction of the spine from biplanar X-rays using parametric models based on transversal and longitudinal inferences

Reconstruction methods from biplanar X-rays provide 3D analysis of spinal deformities for patients in standing position with a low radiation dose. However, such methods require an important reconstruction time and there is a clinical need for fast and accurate techniques. This study proposes and evaluates a novel reconstruction method of the spine from biplanar X-rays. The approach uses parametric models based on longitudinal and transversal inferences.A first reconstruction level, dedicated to routine clinical use, allows to get a fast estimate (reconstruction time: 2 min 30 s) of the 3D reconstruction and accurate clinical measurements. The clinical measurements precision (evaluated on asymptomatic subjects, moderate and severe scolioses) was between 1.2° and 5.6°.For a more accurate 3D reconstruction (complex pathologies or research purposes), a second reconstruction level can be obtained within a reduced reconstruction time (10 min) with a fine adjustment of the 3D models. The mean shape accuracy in comparison with CT-scan was 1.0 mm. The 3D reconstruction method precision was 1.8 mm for the vertebrae position and between 2.3° and 3.9° for the orientation.With a reduced reconstruction time, an improved accuracy and precision and a method proposing two reconstruction levels, this approach is efficient for both clinical routine uses and research purposes.     

脊柱侧凸有限元模型的建立和参数优化

脊柱侧凸种类繁多,为了建立特定患者脊柱的三维有限元模型,并进行生物力学相关的侧凸治疗、病因和病理等研究,参数优化是一个重要的步骤.本文采用螺旋CT扫描收集脊柱侧凸患者的几何学数据,通过系列的图像处理软件和有限元分析软件,建成脊柱侧凸的三维有限元分析模型.该模型初始的材料属性和皮质骨厚度来自文献.其后赋予模型不同材料属性和皮质骨厚度,模拟左、右侧曲试验.首先将计算的结果与临床试验对照,应用SPSS软件进行正交设计数据处理,实现模型材料性质和皮质骨厚度的参数优化.然后再利用优化后模型模拟侧屈和牵引实验,计算结果和临床实验进行对照.结果显示材料性质和皮质骨厚度优化后的模型,其生物力学行为和临床一致.因此,在初步建立的脊柱侧凸的有限元模型的基础上,进行参数优化后的模型有助于深入了解个体的侧凸脊柱的生物力学特征.     

Principal component analysis of chest wall movement in selected pathologies

A method is presented for assessing a compact set of parameters characteristic of respiratory system functional status. 3D movements of points in the chest wall and the volumes of chest wall compartments (pulmonary rib cage, abdominal rib cage and abdomen) are considered. The co-ordinates of these points are measured using an optoelectronic system for 3D motion analysis. Principal component analysis is applied to these data. The behaviour of the eigenvectors of the covariance matrix of the 3D co-ordinates of the points on the chest wall shows close agreement with the pathology characteristics. The same is found for the percentage of total variance explained by the principal components of the volume variations. In this case, the higher values of variance percentage explained indicate independent motions (active or passive) in the degrees of freedom of the system identified by partitioning the total volume into compartments.     

自体肋软骨支架复合乳突区皮肤扩张再造耳郭46例

背景：耳郭支架再造可供选择的材料较多,总体分为人工合成材料及自体组织两种,但各有利弊。 目的：回顾性分析自体肋软骨支架并乳突区皮肤扩张耳郭重建后的临床效果及并发症发生情况。 方法：选择淮安市第一人民医院烧伤整形科进行人工耳郭再造的患者46例,入院后行乳突区皮肤扩张,采用自体肋软骨支架耳郭再造,乳突区皮瓣转移覆盖的方法进行耳郭再造,观察再造效果及再造后并发症发生情况。 结果与结论：46例患者均获得满意耳郭再造效果,耳郭形态逼真,耳颅角清晰。患者治疗后3个月,再造侧耳颅角、耳郭长度及耳郭高度同健侧比较,差异无显著性意义(P > 0.05)。患者治疗后3个月及1年再造耳耳颅角、耳郭长度及耳郭高度比较差异无显著性意义(P> 0.05)。提示乳突区皮肤扩张肋软骨支架耳郭再造安全性高,能够取得较好的再造效果。     

Robust femur condyle disambiguation on biplanar X-rays

Three-dimensional (3D) reconstruction of the skeleton from biplanar X-rays relies on scarce information digitalised by an operator on both frontal and lateral radiographs. In clinical routine, difficulties occur for non-skilled operators to discriminate the medial from the lateral femur condyle on the lateral view. Our study proposes an algorithm able to detect automatically a possible inversion of the two condyles by the operator at an early stage of the reconstruction process. It relies on the computation of two 3D femur surfaces, one directly from the operator digitalisation and the other from the same digitalisation with medial and lateral condyles automatically swapped. Pairs of virtual biplanar X-rays are computed for both reconstructions and the closest pair to the original X-rays is selected on the basis of similarity measures, pointing the correct 3D surface. The algorithm shows a success rate higher than 85% for both asymptomatic and pathological femurs whatever the initial condyle digitalisation of the operator, bringing automatically non-skilled operators acting in clinical routine to the level of skilled operators. This study validates moreover the proof-of-concept of automatic shape adjustments of a 3D surface on the basis of similarity measures in the process of 3D reconstruction from biplanar X-rays.     

The effect of age and demographics on rib shape

Elderly populations have a higher risk of rib fractures and other associated thoracic injuries than younger adults, and the changes in body morphology that occur with age are a potential cause of this increased risk. Rib centroidal path geometry for 20 627 ribs was extracted from computed tomography (CT) scans of 1042 live adult subjects, then fitted to a six‐parameter mathematical model that accurately characterizes rib size and shape, and a three‐parameter model of rib orientation within the body. Multivariable regression characterized the independent effect of age, height, weight, and sex on the rib shape and orientation across the adult population, and statistically significant effects were seen from all demographic factors (P < 0.0001). This study reports a novel aging effect whereby both the rib end‐to‐end separation and rib aspect ratio are seen to increase with age, producing elongated and flatter overall rib shapes in elderly populations, with age alone explaining up to 20% of population variability in the aspect ratio of mid‐level ribs. Age was not strongly associated with overall rib arc length, indicating that age effects were related to shape change rather than overall bone length. The rib shape effect was found to be more strongly and directly associated with age than previously documented age‐related changes in rib angulation. Other demographic results showed height and sex being most strongly associated with rib size, and weight most strongly associated with rib pump‐handle angle. Results from the study provide a statistical model for building rib shapes typical of any given demographic by age, height, weight, and sex, and can be used to help build population‐specific computational models of the thoracic rib cage. Furthermore, results also quantify normal population ranges for rib shape parameters which can be used to improve the assessment and treatment of rib skeletal deformity and disease.     

Three-dimensional reconstruction of the lower limb from biplanar calibrated radiographs

Three-dimensional (3D) reconstruction of lower limbs is essential for surgical planning and clinical outcome evaluation. 3D reconstruction from biplanar calibrated radiographs may be an alternative to irradiation issues of CT-scan. A previous study proposed a two-step reconstruction method based on parametric models and statistical inferences leading to a fast Initial Solution (IS) followed by manual adjustments. This study aims to improve the IS using a new 3D database, a novel parametric model of the tibia and a different regression approach. The IS was evaluated in terms of shape accuracy on 9 lower limbs and reproducibility of clinical measurements on 22 lower limbs. Reconstruction time was also evaluated. Comparison to the previous method showed an improvement of the IS in terms of shape accuracy (1.3 vs. 1.6 and 2 mm respectively for both femur and tibia) and reproducibility of clinical measurements (i.e. 3.1° vs. 8.3° for neck-shaft-angle; 4.2° and 5° vs. 5° and 6° for tibial and femoral torsion respectively). The proposed approach constitutes a considerable step towards an automatic 3D reconstruction of lower limb.     

The Cleveland Clinic PediPump: virtual fitting studies in children using three-dimensional reconstructions of cardiac computed tomography scans

The fitting of implantable ventricular assist devices (VADs) is a particular challenge for pediatric patients and patients with small body surface area. The purpose of this study was to determine optimal placement of the PediPump, a pediatric VAD currently under development at the Cleveland Clinic, using virtual three-dimensional (3D) on-screen models. Digital models were created from computed tomographic datasets of pediatric hearts using commercially available 3D image processing software. Pixels representing the myocardium, great vessels, sternum, and rib cage were selected and rendered as on-screen models (n = 13) from pediatric patients with or without congenital heart disease (median age 42 months; range 2 days to 13 years 11 months). Using 3D model manipulation software, virtual models of the PediPump (70 x 10 mm) were combined on-screen with the anatomic models. A variety of virtual fitting options were created, which allowed easy detection of device interference with surrounding tissues. Generation of 3D on-screen models of cardiac structures in relation to PediPump placement has provided useful preliminary fitting information, which is being used to guide further development of this device.     

Chest wall kinematics during cough in healthy subjects

Aim: The study of kinematics of the chest wall (CW) could allow us to define the relative deflationary contribution of its compartments during fits of coughing. We hypothesized that if forces applied to the lung apposed rib cage are not commensurate with those applied to the abdomen‐apposed rib cage, cough could result in rib cage distortion. Methods: In 12 (five women) healthy subjects we evaluated the volumes of CW (Vcw) and its compartments: the lung apposed rib cage, the abdomen apposed rib cage and the abdomen, by optoelectronic plethysmography. The loop of volume of the lung apposed rib cage/volume of the abdomen apposed rib cage allowed the calculation of mean rib cage distortion, resulting in a dimensionless number which, when multiplied by 100, gives percentage distortion. Each subject performed voluntary single and prolonged coughing efforts at functional residual capacity (FRC) and after maximal inspiration (max). The normal level of mean distortion was set at <0.5%. Results: The three compartments contributed to reducing end‐expiratory Vcw during cough at FRC and prolonged maximum cough, with the latter resulting in the greatest CW deflation. Mean rib cage distortion did not differ between men and women (P > 0.1), but tended to significantly increase from single to prolonged Cough Max (1.3% ± 1.0 vs. 2.3% ± 1.6, respectively; P = 0.06). Conclusion: Rib cage distortion may ensue during coughing, probably as a result of uneven distribution of forces applied to the rib cage.     

Rib Cage Morphogenesis in the Human Embryo: A Detailed Three-Dimensional Analysis

Formation of the skeletal structure in the human embryo has important consequences in terms of support, protection, and function of organs and other systems. We aimed to describe the formation of the rib cage during the embryonic period, in order to detect prominent features and identify the possible factors affecting rib cage morphology. We employed high-resolution digitized imaging data (n = 34) obtained in human embryos with Carnegie stage (CS) between 17 and 23. The rib cage became detectable as cartilage formation at CS17, expanding outward from the dorsal side of the chest-abdominal region. Ribs elongated progressively to surround the chest, differentiating into the upper and lower rib cage regions by CS20. The ends of corresponding ribs in the upper region elongated toward each other, leading to their joining and sternum formation between CS21 and CS23, while the lower region of the rib cage remained widely open. The rib cage area with the largest width shifted from the 5th rib pair at CS17 to the 9th pair at CS23. The depth of the rib cage was similar across the upper region at CS17, with the major portion remaining in the middle part after CS20. The heart was located beneath the rib pairs providing the largest depth, while the liver was located beneath the rib pairs providing the largest width. Formation of the sternum, development of spinal kyphosis, and organization of larger internal organs within the thoracic and abdominal cavity are possible factors affecting rib cage morphology. Anat Rec, 302:2211–2223, 2019. © 2019 American Association for Anatomy     

A filtering approach to image reconstruction in 3D SPECT

We present a new approach to three-dimensional (3D) image reconstruction using analytical inversion of the exponential divergent beam transform, which can serve as a mathematical model for cone-beam 3D SPECT imaging. We apply a circular cone-beam scan and assume constant attenuation inside a convex area with a known boundary, which is satisfactory in brain imaging. The reconstruction problem is reduced to an image restoration problem characterized by a shift-variant point spread function which is given analytically. The method requires two computation steps: backprojection and filtering. The modulation transfer function (MTF) of the filter is derived by means of an original methodology using the 2D Laplace transform. The filter is implemented in the frequency domain and requires 2D Fourier transform of transverse slices. In order to obtain a shift-invariant cone-beam projection-backprojection operator we resort to an approximation, assuming that the collimator has a relatively large focal length. Nevertheless, numerical experiments demonstrate surprisingly good results for detectors with relatively short focal lengths. The use of a wavelet-based filtering algorithm greatly improves the stability to Poisson noise.     

Image feature analysis and computer-aided diagnosis in digital radiography: automated analysis of sizes of heart and lung in chest images

We are developing an automated method for determining a number of parameters related to the size and shape of the heart and of the lungs in chest radiographs. In order to obtain standard patterns of the cardiac shadow as "gold standards," four radiologists traced their best estimates of the entire contour of the heart, including the largely invisible inferior margin, on 11 radiographs. These contours were analyzed by Fourier transform, and the results were used as a guide to obtain a shift-variant cosine function which was applied to the prediction of the cardiac contour by fitting a limited number of detected heart boundary points. These points were obtained from analysis of edge gradients in two orthogonal directions. A simple observer study indicated that the contours of the heart shadows computed for 60 chest radiographs were generally acceptable to radiologists for estimation of the size and area of the projected heart. We also detected the rib cage and the edges of the diaphragm, which enabled us to determine the projected thoracic area. From these results, we calculated the cardiothoracic ratio and other parameters, such as the ratio of the projected heart area to the projected thoracic area.     

Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood

Better understanding of the effects of growth on children’s bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children’s rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT scans of 48 children, aged 4 months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A “costal index” was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level 1 to 3 and increased from level 3 to 7. For all levels, the cartilage accounted for 45–60 % of the rib length, and was longer for the first years of life. The mean costal index decreased by 21 % for subjects over 3-year old compared to those under three (p < 10^?4). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the pediatric thorax and help to detect clinical abnormalities.     

3D打印个体化人工椎体在胸腰椎肿瘤整块切除后脊柱稳定性重建中的应用

目的探索3D打印个体化人工椎体在胸腰椎肿瘤整块切除后脊柱稳定性重建中的临床疗效。方法回顾性分析华中科技大学同济医学院附属同济医院2015年7月至2020年6月收治的接受一期后路全脊椎整块切除术的胸腰椎肿瘤患者28例,分为2组,每组14例。其中3D组使用3D打印个体化人工椎体重建,常规组使用钛笼重建。对比两组的住院时间、手术时间、术中出血量,记录术前、术后7 d及末次随访时视觉模拟评分(VAS),Frankel分级情况,测量节段高度及角度,评估临床疗效。结果两组患者住院时间、手术时间、术中出血量和VAS评分比较,差异无统计学意义。共8例患者Frankel评分获得一个等级的改善(28.6%)。3D组椎间高度丢失(1.9±2.2)mm,内植物沉降2例,沉降率14.3%;常规组椎间高度丢失(6.6±5.5)mm,内植物沉降8例,沉降率57.1%;两组比较差异有统计学意义(<0.05)。在节段角度丢失方面组间差异无统计学意义(=0.571)。3D组所有患者内固定良好,常规组1例患者发生断棒情况。结论 3D打印人工椎体可以更好地维持节段高度,降低椎间隙塌陷和内固定失败的风险。     

Validation of statistical shape model based reconstruction of the proximal femur—A morphology study

Seventeen bones (sixteen cadaveric bones and one plastic bone) were used to validate a method for reconstructing a surface model of the proximal femur from 2D X-ray radiographs and a statistical shape model that was constructed from thirty training surface models. Unlike previously introduced validation studies, where surface-based distance errors were used to evaluate the reconstruction accuracy, here we propose to use errors measured based on clinically relevant morphometric parameters. For this purpose, a program was developed to robustly extract those morphometric parameters from the thirty training surface models (training population), from the seventeen surface models reconstructed from X-ray radiographs, and from the seventeen ground truth surface models obtained either by a CT-scan reconstruction method or by a laser-scan reconstruction method. A statistical analysis was then performed to classify the seventeen test bones into two categories: normal cases and outliers. This classification step depends on the measured parameters of the particular test bone. In case all parameters of a test bone were covered by the training population's parameter ranges, this bone is classified as normal bone, otherwise as outlier bone.Our experimental results showed that statistically there was no significant difference between the morphometric parameters extracted from the reconstructed surface models of the normal cases and those extracted from the reconstructed surface models of the outliers. Therefore, our statistical shape model based reconstruction technique can be used to reconstruct not only the surface model of a normal bone but also that of an outlier bone.