Koen L. Vincken

Background/Objectives: Adolescent idiopathic scoliosis (AIS) can lead to significant chest deformations. The quantification of chest deformity and spinal length could provide additional insights for monitoring during follow-up and treatment. This study proposes a 3D U-Net convolutional neural network (CNN) for automatic thoracic and spinal segmentations of chest MRI scans. Methods: In this proof-of-concept study, axial chest MRI scans from 19 girls aged 8–10 years at risk for AIS development and 19 asymptomatic young adults were acquired (n = 38). The thoracic volume and spine were manually segmented as the ground truth (GT). A 3D U-Net CNN was trained on 31 MRI scans. The seven remaining MRI scans were used for validation, reported by the Dice similarity coefficient (DSC), the Hausdorff distance (HD), precision, and recall. From these segmentations, the thoracic volume and 3D spinal length were calculated. Results: Automatic chest segmentation was possible for all chest MRIs. For the chest volume segmentations, the average DSC was 0.91, HD was 51.89, precision was 0.90, and recall 0.99. For the spinal segmentation, the average DSC was 0.85, HD was 25.98, precision was 0.74, and recall 0.99. Chest volumes and 3D spinal lengths differed by on average 11% and 12% between automatic and GT, respectively. Qualitative analysis showed agreement between the automatic and manual segmentations in most cases. Conclusions: The proposed 3D U-Net CNN shows a high accuracy and good predictions in terms of HD, DSC, precision, and recall. This suggested 3D U-Net CNN could potentially be used to monitor the progression of chest deformation in scoliosis patients in a radiation-free manner. Improvement can be made by training the 3D U-net with more data and improving the GT data.

Quantification of the severity of chest wall deformation in children with spinal deformities is essential for understanding the effects on trunk appearance and cardiopulmonary function. Magnetic resonance imaging (MRI) is particularly valuable for this purpose, as it does not employ ionizing radiation and can provide three-dimensional (3D) imaging of thoracic anatomy. Acquiring sufficient quality images of the chest wall, lungs and airways at key stages of the respiratory cycle, such as end-inspiratory or expiratory phase, is crucial for accurately assessing chest wall deformation and pulmonary function and mechanics. Regarding image quality, low proton density and short relaxation times of the lung tissues result in poor quality images, and long acquisition times result in blurring caused by respiratory and cardiac motion. This overview summarizes strategies developed to address the inherent challenges of visualization of lung tissue and respiratory motion in MRI acquisition of the chest of pediatric patients with spinal deformities. An overview of the main methods for motion-resolved image acquisition and measurement of chest wall motion and thoracic volumes is presented and discussed. It is concluded that despite the development of multiple techniques and diverse strategies for obtaining high-quality, motion-resolved chest MRI, further validation of these methods is required before their implementation in clinics for routine evaluation of chest deformation in pediatric spinal deformity patients.

BACKGROUND AND PURPOSE: The clinical relevance of cortical microinfarcts has recently been established; however, studies on microinfarcts in the deep gray matter are lacking. We examined the risk factors and MR imaging correlates of microinfarcts in the deep gray matter on 7T MR imaging and their relation to cognitive functioning. MATERIALS AND METHODS: Within the Second Manifestations of ARTerial disease–Magnetic Resonance (SMART-MR) study, 213 patients (mean age, 68 [SD, 8] years) had a risk-factor assessment, 7T and 1.5T brain MR imaging, and a cognitive examination. Microinfarcts on 7T MR imaging were defined as lesions of z scores. RESULTS: A total of 47 microinfarcts were found in 28 patients (13%), most commonly in the thalamus. Older age, history of stroke, hypertension, and intima-media thickness were associated with microinfarcts. On 1.5T MR imaging, cerebellar infarcts (relative risk = 2.75; 95% CI, 1.4–5.33) and lacunes in the white (relative risk = 3.28; 95% CI, 3.28–6.04) and deep gray matter (relative risk = 3.06; 95% CI, 1.75–5.35) were associated with microinfarcts, and on 7T MR imaging cortical microinfarcts (relative risk = 2.33; 95% CI, 1.32–4.13). Microinfarcts were also associated with poorer global cognitive functioning (mean difference in the global z score between patients with multiple microinfarcts versus none = −0.97; 95% CI, −1.66 to −0.28, P = .006) and across all cognitive domains. CONCLUSIONS: Microinfarcts in the deep gray matter on 7T MR imaging were associated with worse cognitive functioning and risk factors and MR imaging markers of small-vessel and large-vessel disease. Our findings suggest that microinfarcts in the deep gray matter may represent a novel imaging marker of vascular brain injury.

Background Diffusion Tensor Imaging provides indirect information about the quality of the microstructural organisation of tissues. In this longitudinal study, cross-sectional as well as time-related changes of diffusion measures were assessed in (premanifest) Huntington’s disease using automated histogram analysis. Methods Twenty-two premanifest (preHD), 10 manifest Huntington’s disease (HD) and 24 healthy control subjects completed scans at baseline and two year follow-up. Stratification of preHD into a far (preHD-A) and near (preHD-B) to predicted disease onset group was performed. Age-corrected histograms of whole brain white matter (WM), grey matter (GM) and striatal diffusion measures were computed and normalised by the number of voxels in each subject’s data set. Results Higher cross-sectional mean, axial and radial diffusivities were found in both WM and GM in HD compared to preHD and controls (p ≤ 0.001). In preHD, WM axial diffusivity was higher than in controls and lower than in HD (p ≤ 0.01). This finding remained valid only in preHD-B (p ≤ 0.001). Axial diffusivity was also found to be higher in the striatum of preHD-B compared to controls and preHD-A (p ≤ 0.01). No longitudinal differences in diffusivity measures between the groups were found. Conclusions Alterations in cross-sectional diffusion profiles between HD subjects and controls were evident, both in whole brain and striatum. In preHD, only axial diffusivity alterations were found, a finding that applied only to preHD-B upon group stratification. This suggests that axial diffusivity is a sensitive marker for early change in HD prior to disease manifestation. The individual eigenvalues were superior to fractional anisotropy in revealing pathologic microstructural brain alterations. No longitudinal differences were found in any of the diffusivity measures between the groups.

Cross-sectional study. To compare the relative contribution of the vertebral bodies and intervertebral discs with the 3-dimensional spinal deformity in adolescent idiopathic scoliosis. There is an ongoing discussion about the causal role of skeletal growth processes in the etiopathogenesis of adolescent idiopathic scoliosis. Contradictory findings have been reported on the individual contribution of the vertebral bodies as compared with the discs to the coronal deformity. As far as we know, the true 3-dimensional deformity of the discs and vertebral bodies have not yet been described. High-resolution computed tomographic scans of 77 patients with severe adolescent idiopathic scoliosis were included. Torsion and anterior-posterior and right-left asymmetry of each individual vertebral body and intervertebral disc were studied from T2 to L5, using semiautomatic analysis software. True transverse sections were reconstructed along the anterior-posterior and right-left axis of all endplates. These "endplate-vectors" were calculated semiautomatically, taking rotation and tilt into account. Torsion was defined as the difference in axial rotation between 2 subsequent endplates. Asymmetry was defined as the relative anterior-posterior or right-left height difference of the discs and the vertebrae. There were at least 3 times more torsion, anterior overgrowth, and coronal wedging in the discs than in the vertebrae in the thoracic as well as in the (thoraco) lumbar curves (P<0.001). These values correlated significantly with the Cobb angle (r≥0.37; P<0.001). Anterior overgrowth and coronal asymmetry were greater in the apical regions whereas torsion was most pronounced in the transitional segments between the curves. The discs contribute more to 3-D deformity than the bony structures, and there is significant regional variability. This suggests an adaptive rather than an active phenomenon. 2.

Adolescent idiopathic scoliosis occurs far more often in girls than in boys, and its initiation and progression normally takes place around the adolescent growth spurt. Despite extensive research into the topic, no solid explanation for both well-known phenomena has been offered. The sagittal profile of the growing spine has been demonstrated previously to play an important role in the spine’s rotational stiffness. Changes in this sagittal alignment around the growth spurt can be inferred to play an important role in the spine’s propensity to develop a rotatory deformity, i.e. scoliosis. The aim of this study was to quantify sagittal spino-pelvic alignment and orientation in space of each individual vertebra in normal boys and girls in the beginning, at the peak and at the end of pubertal growth. Standardized lateral radiographs of the spine of boys (n = 57) and girls (n = 99) between the age of seven and eighteen who underwent screening for scoliosis, but had a normal spine were enrolled in this study. Children with spino-pelvic pathology at initial screening or during follow-up were excluded. According to Dimeglio’s data, subjects were classified into three groups: before, at and after the peak growth spurt. Seven regional sagittal spino-pelvic parameters, as well as the inclination angles of each individual vertebra between C7 and L5 compared to the gravity line, were measured semi-automatically using in-house developed software. In all subjects, the posteriorly tilted segment was longer, vertebrae T1–T8 were more posteriorly inclined and thoracic kyphosis, pelvic incidence and pelvic tilt were lower before as well as during the peak of the growth spurt, when compared to after the growth spurt (P ≤ 0.023). Furthermore, in girls, thoracic kyphosis was smaller (P = 0.023), the posteriorly inclined segment was longer (P < 0.001) and T1 as well as levels T3–T11 were more posteriorly inclined (P < 0.05) compared to boys at all stages of development. At the peak of the growth spurt, girls had more posterior inclination of upper thoracic vertebrae and lower values for thoracic kyphosis than boys (P = 0.005). These results imply that the spines of girls during the growth spurt are more posteriorly inclined, and thus rotationally less stable, compared to boys at the same stage of development, as well as compared to girls after the growth spurt. This may explain why initiation and progression of adolescent idiopathic scoliosis are more prevalent in girls around puberty.

Human bipedalism appears to be a prerequisite for the development of idiopathic scoliosis. The objective of this study was to examine the effect of different positions of the human spine on vertebral rotation in vivo. Thirty asymptomatic volunteers underwent MRI scanning of the spine in three different body positions; upright, quadrupedal-like and supine. Vertebral rotation in the local transverse plane was measured and compared at different spinal levels between the three body positions. It was shown that in all three positions the mid and lower thoracic vertebrae were predominantly rotated to the right. However, rotation was significantly less in certain areas of the spine in the quadrupedal-like position than in both the standing upright and supine positions. We hypothesize that the erect position of the human spine, but also the supine position, increases dorsally directed shear loads that may increase the tendency of certain spinal segments to rotate.