Patterns of coronal curve changes in forward bending posture: a 3D ultrasound study of adolescent idiopathic scoliosis patients

Three-dimensional ultrasonography could be a potential non-ionizing tool to evaluate vertebral rotation of subjects with adolescent idiopathic scoliosis

Background

Three-dimensional (3D) ultrasonography is nonionizing and has been demonstrated to be a reliable tool for scoliosis assessment, including coronal and sagittal curvatures. It shows a great potential for axial vertebral rotation (AVR) evaluation, yet its validity and reliability need to be further demonstrated.

Materials and Methods

Twenty patients with adolescent idiopathic scoliosis (AIS) (coronal Cobb: 26.6 ± 9.1°) received 3D ultrasound scan for twice, 10 were scanned by the same operator, and the other 10 by different operators. EOS Bi-planar x-rays and 3D scan were conducted on another 29 patients on the same day. Two experienced 3D ultrasonographic researchers, with different experiences on AVR measurement, evaluated the 3D ultrasonographic AVR of the 29 patients (55 curves; coronal Cobb angle: 26.9 ± 11.3°). The gold standard AVR was determined from the 3D reconstruction of coronal and sagittal EOS radiographs. Intra-class correlation coefficients (ICCs), mean absolute difference (MAD), standard error measurements (SEM), and Bland-Altman's bias were reported to evaluate the intra-operator and inter-operator/rater reliabilities of 3D ultrasonography. The reliability of 3D ultrasonographic AVR measurements was further validated using inter-method with that of EOS.

Results

ICCs for intra-operator and inter-operator/rater reliability assessment were all greater than 0.95. MAD, SEM, and bias for the 3D ultrasonographic AVRs were no more than 2.2°, 2.0°, and 0.5°, respectively. AVRs between both modalities were strongly correlated (R 2 = 0.901) and not significantly different (p = 0.205). Bland-Altman plot also shows that the bias was less than 1°, with no proportional bias between the difference and mean of expected and radiographic Cobb angles.

Conclusion

This study demonstrates that 3D ultrasonography is valid and reliable to evaluate AVR in AIS patients. 3D ultrasonography can be a potential tool for screening and following up subjects with AIS and evaluating the effectiveness of nonsurgical treatments.

A novel method for spine ultrasound and X-ray radiograph registration

Ultrasound is a promising imaging method for scoliosis evaluation because it is radiation free and provide real-time images. However, it cannot provide bony details because ultrasound cannot penetrate the bony structure. Therefore, registration of real-time ultrasound images with the previous X-ray radiograph can help physicians understand the spinal deformity of patients. In this study, an improved free-from deformation registration method based on mutual registration and hierarchical adaptive grid (MRHA-FFD) was developed. The method first performed registration grid preprocessing and then optimized control points and conducted mutual registration. Finally, a Blur-aware Attention Network was adopted for image deblurring. The performance of each step was verified by ablation experiments. Comparison experiment between the proposed method and traditional registration methods was also conducted. The qualitative and quantitative results suggested that MRHA-FFD is a promising approach for registering spine ultrasound image and X-ray radiograph.

Assessment of thoracic spinal curvatures in static postures using spatially tracked 3D ultrasound volumes: a proof-of-concept study

The assessment of spinal posture is a difficult endeavour given the lack of identifiable bony landmarks for placement of skin markers. Moreover, potentially significant soft tissue artefacts along the spine further affect the accuracy of marker-based approaches. The objective of this proof-of-concept study was to develop an experimental framework to assess spinal postures by using three-dimensional (3D) ultrasound (US) imaging. A phantom spine model immersed in water was scanned using 3D US in a neutral and two curved postures mimicking a forward flexion in the sagittal plane while the US probe was localised by three electromagnetic tracking sensors attached to the probe head. The obtained anatomical 'coarse' registrations were further refined using an automatic registration algorithm and validated by an experienced sonographer. Spinal landmarks were selected in the US images and validated against magnetic resonance imaging data of the same phantom through image registration. Their position was then related to the location of the tracking sensors identified in the acquired US volumes, enabling the localisation of landmarks in the global coordinate system of the tracking device. Results of this study show that localised 3D US enables US-based anatomical reconstructions comparable to clinical standards and the identification of spinal landmarks in different postures of the spine. The accuracy in sensor identification was 0.49 mm on average while the intra- and inter-observer reliability in sensor identification was strongly correlated with a maximum deviation of 0.8 mm. Mapping of landmarks had a small relative distance error of 0.21 mm (SD = ± 0.16) on average. This study implies that localised 3D US holds the potential for the assessment of full spinal posture by accurately and non-invasively localising vertebrae in space.

Ultrasound to X-ray synthesis generative attentional network (UXGAN) for adolescent idiopathic scoliosis

Standing X-ray radiograph with Cobb's method is the gold standard for scoliosis diagnosis. However, radiation hazard restricts its application, especially for close follow-up of adolescent patients. Compared with X-ray, ultrasound imaging has advantages of being radiation-free and real-time. To combine advantages of the above two imaging modalities, an ultrasound to X-ray synthesis generative attentional network (UXGAN) was proposed to synthesize ultrasound images into X-ray-like images. In this network, a cyclically consistent network was adopted and was trained end-to-end. An attention module was added and different residual blocks were designed. The quantitative comparison results demonstrated the superiority of our method to the state-of-the-art CycleGAN methods. We further compared the Cobb angle values measured on synthesized images and the real X-ray images, respectively. A good linear correlation (r = 0.95) was demonstrated between the two methods. The above results proved that the proposed method is of great significance for providing both X-ray images and ultrasound images based on the radiation-free ultrasound scanning.

Retrospective Analysis of FED Method Treatment Results in 11-17-Year-Old Children with Idiopathic Scoliosis

(1) Background: Idiopathic scoliosis is a major treatment problem due to its unknown origin and its three-dimensional nature. Attempts to cure it and search for new methods of physiotherapeutic treatment that would lead to its correction are one of the key issues of modern medicine. One of them is the fixation, elongation, de-rotation method (FED), used in the conservative treatment of idiopathic scoliosis. The aim of the study was evaluation of the short-term effectiveness of the FED method in the treatment of patients with idiopathic scoliosis. (2) Methods: Each patient underwent therapy based on the guidelines of the FED method. Patients were tested with the Bunnell scoliometer and the Zebris computer system. The treatment period was three weeks, after which the examinations were repeated. (3) Results: The results appeared to be statistically significant for all tested variables. (4) Conclusions: The examinations showed that the FED method had a statistically significant effect on the improvement of all parameters of posture examination, regardless of the size of the scoliotic deformation angle and bone maturity.

Analysis of Posture Parameters in Patients with Idiopathic Scoliosis with the Use of 3D Ultrasound Diagnostics-Preliminary Results

(1) Background: Idiopathic scoliosis occurs in 2 to 4% of children between 10 and 16 years of age. Due to the harmfulness of radiological examination, non-invasive devices, including the 3D ultrasound technology and Scolioscan apparatus, are more and more frequently used for postural diagnostics. The aim of the study was to analyze the parameters of posture in patients with idiopathic scoliosis with the use of 3D ultrasound diagnostics. (2) Methods: The study included 20 girls, aged 10 to 16 years, with double-curve idiopathic scoliosis (the value of primary curve ranged from 25–50°), types I and II according to King–Moe classification. On the basis of X-ray scan, the Cobb angle of primary and secondary curves was assessed, the skeletal maturity was evaluated with the Risser test, and the type of scoliosis was determined. The girls participated in a 3-week rehabilitation program. The examinations were performed before and after therapy. A scoliometer was used for measurements. Each of the participants underwent individual therapy. The three-plane approach to asymmetric exercises was based largely on positions that included primary curve correction with hypercorrection of the secondary curve. (3) Results: After the therapy, values of trunk rotation angles and the angle of scoliotic curvature of secondary curve were significantly lower than before the therapy, except for the value of the primary curve angle. The parameters measured by X-ray were significantly and positively related to the results obtained with the scoliometer and the scolioscan. (4) Conclusions: The application of therapy that takes into account summing parameters may prevent the deterioration of the secondary curve when treating patients with idiopathic scoliosis. The observed correlations between the parameters of the radiological examination, the scoliometer, and the scolioscan prove the possibility of their interchangeable application in the assessment of effects of the therapy. Three-dimensional ultrasound diagnostics may become an alternative to radiological examination in assessing the treatment effects of patients with idiopathic scoliosis.

Effectiveness of the FED Method in the Treatment of Idiopathic Scoliosis of Girls Aged 11-15 Years

(1) Background: The unknown etiology of idiopathic scoliosis and its three-dimensional nature make the cause-and-effect therapeutic management difficult. A tendency to progression of scoliosis and the failure of many methods of conservative treatment have prompted the search for new methods that would stop and correct deformations. One of them is the FED method, used in the conservative treatment of idiopathic scolioses, in which all scoliotic curves are corrected. The aim of this study was a comparative analysis of the effectiveness of idiopathic scoliosis treatment with the FED and FITS methods. (2) Methods: The study included 60 randomly selected girls, aged 11 to 15 years, treated with the FED and FITS methods. They were diagnosed with idiopathic scoliosis grade II according to Cobb and double-curve scoliosis type I and II according to King–Moe classification. The results of the therapy were assessed with the use of the Bunnell scoliometer. The examinations were performed before the start of the therapy—on the first day of the child’s stay—and 3 weeks after the therapy. The angle of trunk rotation and the sum of two rotations were assessed using a scoliometer. (3) Results: The performed statistical analysis demonstrated significant changes in the examined parameters in both therapeutic groups. (4) Conclusions: 1. The obtained results indicate that the FED therapy may prove to be an effective method of treating idiopathic scoliosis; however, it requires further research in a larger group of patients; 2. both methods significantly improved trunk rotation in primary and secondary scoliosis, but after using summing parameters (SDR parameter), the FED method appeared to be statistically more effective.

3D ultrasound imaging provides reliable angle measurement with validity comparable to X-ray in patients with adolescent idiopathic scoliosis

BACKGROUND & OBJECTIVE

The application of ultrasound imaging for spine evaluation could minimize radiation exposure for patients with adolescence idiopathic scoliosis (AIS). A customized three-dimensional (3D) ultrasound imaging system has been demonstrated to provide reliable and valid coronal curvature measurements. However, these measurements were using the spinous processes as anatomical reference, leading to a predictable underestimation of the traditionally used Cobb angles. An alternative 3D ultrasound image reconstruction method was applied to create coronal images with more lateral features for angle measurement. The objective of this study was to test the reliability and the validity of this angle, the ultrasound curve angle (UCA), and compare the UCA with the Cobb angles on X-ray images of patients with AIS.

MATERIALS AND METHODS

This study was divided into: 1) Investigation of intra- and inter-reliability between two raters for measuring the UCA and two operators for acquiring ultrasound images; 2) Investigation of the validity between the radiographic Cobb angle and the UCA. Fifty patients and 164 patients with AIS, were included in the two stages, respectively. Patients underwent bi-planar X-ray and 3D ultrasound scanning on the same day. The proposed UCA was used to measure the coronal curvature from the ultrasound coronal images, which were formed using a newly customized volume projection imaging (VPI) method. The intra-rater/operator and inter-rater and operator reliability of the UCA were tested by intra-class correlation coefficient (ICC) (3,1) and (2,1), respectively. The validity of UCA measurements as compared to radiographic Cobb angles was tested by inter-method ICC (2,1), mean absolute difference (MAD), standard error of measurement (SEM), Pearson correlation coefficient and Bland-Altman statistics. The level of significance was set as 0.05.

RESULTS

Excellent intra-rater and intra-operator (ICC (3,1)≥0.973) and excellent inter-rater and inter-operator reliability (ICC (2,1)≥0.925) for UCA measurement, with overall MAD and SEM no more than 3.5° and 1.7° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. Very good correlations were observed between UCA and Cobb angle for main thoracic (R 2 =0.893) and (thoraco)lumbar (R 2 =0.884) curves. The mean (SD) measurements in terms of radiographic Cobb and UCA were 27.2 ​± ​11.6° and 26.3 ​± ​11.4° for main thoracic curves; and 26.2 ​± ​11.4° and 24.8 ​± ​9.7° for (thoraco)lumbar curve respectively. One hundred sixty-four subjects (33 male and 131 female subjects; 11-18 years of age, mean of 15.1 ​± ​1.9 years) were included for the validity session. Excellent inter-method variations (ICC (2,K) ≥0.933) with overall MAD and SEM no more than 3.0° and 1.5° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. In addition, Bland-Altman plots demonstrated an acceptable agreement between ultrasound and radiographic Cobb measurements.

CONCLUSION

In this study, very good correlations and agreement were demonstrated between the ultrasound and X-ray measurements of the scoliotic curvature. Judging from the promising results of this study, patients with AIS with different severity of curves can be evaluated and monitored by ultrasound imaging, reducing the usage of radiation during follow-ups. This method could also be used for scoliosis screening.The Translational potential of this article: Ultrasound curve angle (UCA) obtained from 3D ultrasound imaging system can provide reliable and valid evaluation on coronal curvature for patients with AIS, without the need of radiation.

Validation of Scolioscan Air-Portable Radiation-Free Three-Dimensional Ultrasound Imaging Assessment System for Scoliosis

To diagnose scoliosis, the standing radiograph with Cobb's method is the gold standard for clinical practice. Recently, three-dimensional (3D) ultrasound imaging, which is radiation-free and inexpensive, has been demonstrated to be reliable for the assessment of scoliosis and validated by several groups. A portable 3D ultrasound system for scoliosis assessment is very much demanded, as it can further extend its potential applications for scoliosis screening, diagnosis, monitoring, treatment outcome measurement, and progress prediction. The aim of this study was to investigate the reliability of a newly developed portable 3D ultrasound imaging system, Scolioscan Air, for scoliosis assessment using coronal images it generated. The system was comprised of a handheld probe and tablet PC linking with a USB cable, and the probe further included a palm-sized ultrasound module together with a low-profile optical spatial sensor. A plastic phantom with three different angle structures built-in was used to evaluate the accuracy of measurement by positioning in 10 different orientations. Then, 19 volunteers with scoliosis (13F and 6M; Age: 13.6 ± 3.2 years) with different severity of scoliosis were assessed. Each subject underwent scanning by a commercially available 3D ultrasound imaging system, Scolioscan, and the portable 3D ultrasound imaging system, with the same posture on the same date. The spinal process angles (SPA) were measured in the coronal images formed by both systems and compared with each other. The angle phantom measurement showed the measured angles well agreed with the designed values, 59.7 ± 2.9 vs. 60 degrees, 40.8 ± 1.9 vs. 40 degrees, and 20.9 ± 2.1 vs. 20 degrees. For the subject tests, results demonstrated that there was a very good agreement between the angles obtained by the two systems, with a strong correlation (R2 = 0.78) for the 29 curves measured. The absolute difference between the two data sets was 2.9 ± 1.8 degrees. In addition, there was a small mean difference of 1.2 degrees, and the differences were symmetrically distributed around the mean difference according to the Bland-Altman test. Scolioscan Air was sufficiently comparable to Scolioscan in scoliosis assessment, overcoming the space limitation of Scolioscan and thus providing wider applications. Further studies involving a larger number of subjects are worthwhile to demonstrate its potential clinical values for the management of scoliosis.

A Novel Method to Measure the Sagittal Curvature in Spinal Deformities: The Reliability and Feasibility of 3-D Ultrasound Imaging

The objective of this study was to test the reliability of sagittal spinal curvature measurements using 3-D ultrasound in patients with adolescent idiopathic scoliosis (AIS). Ultrasound spinous process angle (USSPA) and ultrasound laminae angle (USLA) were measured on sagittal ultrasound images, while the Cobb angle (XCA) was measured on sagittal X-ray images. Intra-class correlation coefficients (ICC) for the intra- and inter-observer variability, linear regression analysis and Bland-Altman method, including mean absolute difference (MAD), were investigated to evaluate the reliability and validity of the two ultrasound angles compared with XCA. Excellent measurement reliabilities were demonstrated for both ultrasound angles (ICC ≥ 0.91). Moderate to good and significant linear correlations and good agreement were demonstrated between the ultrasound methods and XCA (Thoracic [R² ≥ 0.574] / Lumbar [R² ≥ 0.635]). No significant differences were found for the MADs between both corrected ultrasound angles and XCA. Sagittal ultrasound angles were demonstrated to be reliable for assessing sagittal curvature using spinous processes and laminae and to have good and significant correlations with XCAs. Since it is non-ionizing and relatively low cost, this method opens the possibility of providing frequent curve monitoring and evaluation, and screening for AIS patients, particularly based on sagittal profiles.