## 4 Discussion
[PERSON] and [PERSON] reviewed diagnostic methods and emphasized that scoliosis measurements should not focus only on Cobb angles best calculations because several methods may deliver equally accurate parameters [19]. The analysis of the human torso's shape was also applied before and after scoliosis surgery [25; 27; 72]. The approach presented in this study utilizes the combined data from 3D ST optical scans and X-rays. X-ray imaging of the vertebral column remains crucial for scoliosis case diagnosis. The combination of 3D ST and radiography minimizes the number of required X-rays to one where two X-rays are usually needed. Only simultaneous biplanar radiographic devices with dedicated software (sterEOS software) can create three-dimensional representations of the whole spine [73]. Two perpendicular X-ray images obtained sequentially require extensive computer processing to produce similar results. Moreover, it may be difficult for the patient to stand in the same body position during both radiographs in two different projections. The proposed solution combines a single posterior-anterior (PA) X-ray image with the information provided by a 3D ST optical system. Combining a plain radiogram and the 3D ST image seems more efficient because four-directional full 3D ST scanning produces significantly more information than unidirectional ST [45; 70; 71] without repeated exposure to ionizing radiation [74; 75; 76]. The task to reduce the lifetime risk of cancer from spinal radiographs among people with adolescent idiopathic scoliosis remains essential. Techniques using 3D ST optical scanning may improve patient safety. The presented method is designed for predicting the spinous processes line and approximating the degree of scoliotic deformity. The method, however, assumes no vertebral torsion, and calculations are given only for rotation. There are few techniques for detecting the spinous processes line because most of the rough ST methods result in scolioneter measurements [63] or use particular indices to determine deformity [38]. Appropriate indices should be able to distinguish between different types of surface deformities [38]. Automatic detection of scoliosis by a computer using Moire topographic images results in correct recognition in 95 % of cases [77]. [PERSON] et al. [78] found that a high degree of variability exists between spine scoliosis (Cobb angle) and trunk asymmetry with the back ST's axial rotation. The method's accuracy primarily depends on the quality of the X-ray image's mutual adjustment with the cloud of points obtained using 3D ST optical scanning. The ideal result would be produced using a single device capable of simultaneous X-ray image acquisition and 3D ST optical scanning. In the present study, a single case presented a lower correlation of 0.41. In this case, the reason for the less accurate correlation was technical in nature and was due to the shorter length of the radiograph available for merging of the X-ray and 3D ST. The above would ensure that the data collected by both methods measure the patient in the same posture and would render post hoc alignment unnecessary. Less accurate results are obtained when the data alignment is based on markers placed on the patient's body visible in both the X-ray image and the 3D ST data scan. Several 3D ST systems need markers on the patient's back to identify bony landmarks or measure their contour. Stickers [36; 79] or markers placed on landmarks of the back, including the spinous processes, are frequently used to identify the \"spine line\" [80] and follow the scoliosis curve [81] of examined patients. The use of too many markers during the evaluation may lead to skewing the 3D ST data superimposition over the X-ray image, even in simple cases. This study was performed using previously existing data based on the markerless method. To our knowledge, only Formetric 3D ST [82] and 3 DMADMAC/3D Ortho-screen [53] require no markers. Performing the adjustment of images in the merging procedure in the method may affect the results' reliability.